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	Copy No. ________
	Secret!
	Diving Regulations
	for U-boats
	(U-boat Div.Reg.)
	Berlin 1943
	Oberkommando der Kriegsmarine
	Navy Official Inst. No. 381                                     Issued August 1943

Click the icin to view the above page in the original Fraktur

	Corrections are to be entered in accordance with "Bulletin for publications" paragraph 5.
	This is a Secret item in terms of Reich Penal Code § 88 [24 April 1934 version].  Violation is punishable in accordance with this code, if any other criminal law rules do not apply.

	In addition to the procedures given in these diving regulations, flotilla orders, standing war experiences and other regulations in issued orders and instructions are to be observed.

	Table of Contents
	Sub paragraph Page Section I General regulations 5 - 6 1 - 10   A.  Instructional language and commands 5 - 6 11 - 15   B.  Diving board, Assignment board 7 16 - 25   C.  Safety regulations 7 - 9 26 - 30   D.  Diving log book 9 - 10         Section II 31 - 40   Readiness for sea 11 - 13         Section III Readiness to dive 14 - 18 41 - 42   A.  Commands 14 43 - 50   B.  Actions to be taken 14 - 16 51 - 60   C.  Reports 16 - 18         Section IV 61 - 70   Leak test 19 - 21         Section V 71 - 100   Trim test 22 - 29         Section VI 101 - 110   Test dive 30 - 32         Section VII 111 - 130   Crash diving 33 - 37 131 - 140   A.  Negative buoyancy tanks 37 - 39 141 - 150   B.  Preflooding of forward ballast tanks while crash diving 39 - 41

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	Sub paragraph Page Section VIII Submerged cruise 42 - 51 151 - 160   A.  General 42 - 43 161 - 170   B.  Cruising at periscope depth 44 - 45 171 - 175   C.  Going quickly to 20 meters 45 - 46 176 - 180         Going quickly to periscope depth 46 - 47 181 - 195   D.  Cruising at great depth 47 - 50 196 - 200   E.  Silent running 50 - 51         Section IX 201 - 230   Surfacing 52 - 59       Section X 231 - 240   Lying on the bottom, rising from the bottom 60 - 63         Section XI Conduct in difficult conditions 64 - 68 241 - 247   A.  Water intake 64 - 65 248 - 253   B.  Scuttling the boat 66 254 - 360   C.  Countering large trim angles 67 - 68         Section XII Diving commands 69 - 81 261 - 268   A.  Preliminary remarks 69 - 70 269 - 274   B.  Negative pressure test 71 - 72 275 - 280   C.  Test dive 72 - 74 281 - 285   D.  Crash dive 74 - 75 286 - 290   E.  Submerged cruise 286 - 290        a)  Depth keeping orders 75 - 76 291 - 295        b)  Depth changing 76 - 77 296 - 297        c)  Periscope 77 - 78 298 - 300        d)  Negative buoyancy tanks 78 301 - 303        e)  Working with men 79 304 - 305        f)  Rudders 79 306 - 315     306 - 315   F.  Surfacing 79 - 81         Appendix Instructions for the performance of the pressure dock test 82 - 84

	- 5 -
	Section I
	General Regulations
	A.  Instructional language and commands
	1.  All orders, reports and feedback given while flooding, diving, surfacing, blowing etc. are to be repeated to guarantee they are understood correctly.
	The report of execution must follow every order.
	2.  When orders concerning the operation of shut off valves are given only the words "open" and "close" are to be used.  In feedback about the position of the valve only the words "on" and "off" are to be used.  Words such as "shut, tight and opened", are prohibited
	Only standardized nomenclature (in accordance with the sketch book) is to be used in the naming of piping, shutoff valves etc.
	3.  The order to flood is only to be given verbally.  If the vents are to be opened during submerged cruise, the command is: "Open vents".
	4.  Strict silence generally prevails in the boat while submerged, so that sounds which suggest any malfunction in the compressed air system or water entry from outside are heard immediately.
	To a great extent operations are done by communication with hand signals.

	- 6 -
	5.  Each proposed knocking, filing etc. must be requested.  Moving about the boat is to be conducted noiselessly after prior request to the control room.   It must be limited to that which is absolutely necessary.  In addition, it is necessary that floor plates lie firmly and do not rattle.
	6.  Diving commands see separate compilation Section XII.
	7.  Free.
	8.  Free.
	9.  Free.
	10.  Free.

	- 7 -
	B.  Diving board, assignment board
	11.  Diving boards listing the steps which must be taken to prepare for diving are issued for every type of boat.  The sailors who implement these measures or must take over responsibility for correct execution are listed on the assignment boards.
	12.  The measures concern:
	I.  Upper deck:
	a)  seamanship,
	b)  technical.
	II.  Below deck:
	By compartment from aft to forward.
	13.  Diving boards are installed in every compartment, also Morse code is displayed on a separate board in every compartment.
	14.  Every man of the crew must be proficient in the operation of the safety and rescue equipment.
	15.  Free.
	C.  Safety regulations
	16.  A boat may dive only if a Commander and an Engineering Officer are aboard.
	17.  To enter and depart dry dock an Engineering Officer must be aboard.

	- 8 -
	18.  Partial flooding of tanks in the harbor may be carried out only under the supervision of the Engineering Officer.  In addition, the boat must be ready to dive below decks (if necessary with the exception of the conning tower hatch).
	It is important to assure that the compressed air supply is sufficient to blow flooded tanks.  With the high pressure air installation out of service, partial flooding of the ballast tanks may be executed only if emergency blowing of ballast tanks is installed and connected.
	19.  In the harbor after business hours all hatches must be closed except for the conning tower hatch.
	The torpedo loading hatch may be open only in the presence of an Officer.
	20.  Before diving the Commander must be knowledgeable of the water depth and other navigational matters.   During peacetime exercises the shallowest water depth is 18 meters.   Diving in shallow water may take place only with very small trim angles.
	21.  During peacetime exercises the boat may not be dived unless the following are aboard:
	a)  half of the compressed air supply,
	b)  half of the oxygen supply,
	c)  an operable escape device for every man aboard.
	22.  The flood valves may be opened at sea only when the boat is ready to dive.  They may not be closed, as long as the associated ballast tanks are totally or partially flooded.
	23.  Ready to dive reports:
	Boats proceeding independently in home waters are to send the diving report or surfacing report as a coded radio message on the applicable safety frequency.  Training flotillas acknowledge the diving and surfacing reports by special abbreviations according to a reference number plan.  Safety frequencies are continuously monitored by the responsible base or the safety vessel present at sea.

	- 9 -
	24.  Free.
	25.  Free.
	D.  Diving logbook
	26.  The diving log book is maintained by the Zentralemaat [Petty Officer in charge of the Control Room, typically a Maschinenmaat] under supervision of the Chief Engineering Officer to monitor weight and trim changes.  It is a secret document, therefore it is taken and signed daily by the Engineering Officer.  From time to time it is to be submitted to the Commander for counter signature.
	27.  A trim computation is established for every diving day, another after every large change (e.g., torpedo loading).  The starting point of the trim computation is always the last sounding after balancing of the boat.  Therefore, this sounding is carried out carefully to energetically resolve of any discrepancies.
	28.  Every sheet of the diving log book must be filled out completely, so that on its own, it proves the weight and trim condition of the boat unambiguously.
	In addition, it is an important aid for depth control, particularly for longer submerged cruising, if at any time the complete filling of the regulating tanks and the distribution of trim water is evident (by writing down the filling changes).

	- 10 -
	29.  Free.
	30.  Free.

	- 11 -
	Section II
	Readiness for sea
	31.  Before every cruise the submarine is to be made ready for sea in a general manner according to the regulations issued for surface ships.  In addition, the following preparations are to be made:
	32.  By the Watch Officer:
	a)  check the under water communications equipment,
	b)  immediately after torpedo loading reinstall braces,
	c)  examine the signal buoys, if installed.
	33.  By the Engineering Officer:
	a)  turn on the gyro compass 5 hours before ready to sail,
	b)  adjust the depth gauge, trim angle and heeling indicators,
	c)  test the diving planes (also uncoupled for manual operation) and the diving plane position indicators,
	d)  check the hull closure and (if installed) vent valve position indicators,
	e)  establish the trim computation,
	f)  charge the battery (if the exercise does not require that batteries are full, observe the provisions adopted to preserve battery life),
	g)  test the periscope installation,
	h)  close or check the hatches and bulkheads,
	i)  perform the leak test.

	- 12 -
	34.  Before starting the diesel engines for a test run, special attention must be paid to the fact that the main clutches [tail clutches - aft of the E-motor] are disengaged.  The diesel engine clutch [between the diesel engine and E-motor] is engaged, so that the armature of the E motor runs as a flywheel.  15 minutes before ready to sail the engines are turned off and the main clutches are engaged.  If possible, the bilges are pumped out after previously asking the bridge "Request pumping out".  The ballast tanks are blown out separately (the required flood valves are to be opened for this purpose).
	35.  Beneath the upper deck and inside the boat all items must be stowed for sea.
	36.  To be ready to sail all hatches are to be closed except for the conning tower hatch.   The hatches must be closed not only from above.  A man must be standing at the hatch below deck to crank the hatch from below.   A report must made each time to the Engineering Officer: "Torpedo loading hatch", "Galley hatch" etc. "is off".  The safety catch on the hatches must not be clamped.
	37.  The reports:
	"Boat is ready for sea",
	"Machinery is ready for sea",
	include all of the appropriate measures for going to sea and subsequent diving.
	This implies that the boat is ready to dive except for operationally necessary shut-off valves below deck and that the leak test was performed.
	38.  If individual measures could not be performed, it is to be specifically reported to the Commander.
	39.  Free.

	- 13 -
	40.  Free.

	- 14 -
	Section III
	Readiness to dive
	A.  Commands
	41.  The Commander gives the order:
	Commander:  "Prepare to dive",
	if necessary with restrictions (e.g. "except for diesels")
	If circumstances require, it is first ordered:
	"Upper deck prepare to dive"
	and later
	"Below deck prepare to dive".
	42.  This command is only given to the Engineering Officer.  The Engineering Officer repeats it and passes it to all rooms verbally man to man.
	B.  Actions to be taken
	43.  Actions to be taken by the Watch Officer:
	a)  prepare the upper deck to dive (Seamanship),
	b)  prepare the artillery to dive,
	c)  prepare the communications equipment to dive,
	d)  prepare the torpedo armament to dive.
	44.  Actions to be taken by the Engineering Officer:
	a)  calculate and establish the weight and trim condition,
	b)  prepare the upper deck to dive (Technical),
	c)  prepare below decks to dive.

	- 15 -
	45.  Explanation of 43:
	In preparing the upper deck to dive the following directives are to be particularly emphasized:
	No loose items may lie under the upper deck.  All objects, such as lines, fenders, torpedo loading device, gangway, dingy, must be lashed, so that they cannot be knocked loose and foul the anchor or rescue equipment, air, diesel exhaust and vent ducting or also the propellers.  The dogs of all access hatches and other fasteners must be checked for proper closing.   Attention must be paid to the fact that the access hatches are closed correctly and do not rattle.  The signal buoy (if installed) must be latched and secured.  The drain and plug screw of the dingy must be open.
	In readying the bridge, attention is to be paid to the fact that all folding seats are well secured because otherwise, they will rattle during submerged cruise.  All wooden gratings need to be checked.
	The speaking tube cocks are closed on the order of the Commander.  If they remain open at prepare to submerge, they must be closed not later than by the closing of the conning tower hatch.
	46.  The following guidance is particularly important in preparing below decks:
	The back-up shut-off valves must not only be closed (as far as submerged operation allows), but also checked for operability.  The operability and correct indication of display devices is to be checked.
	The Engineering Officer personally inspects that the hatches and support beams in the torpedo hatches are correctly in place at each break in the ready to submerge condition.  The hatches are to be illuminated by the hanging of trouble lights.  After prior request to the bridge

	- 16 -
	the bilges are to be well pumped.  During calculation and establishment of the filling quantities the Engineering Officer must pay attention to the fact that regulating and trim water is distributed appropriately.
	47.  The senior man in each room reports readiness to dive to the Engineering Officer.
	The Engineering Officer monitors the ready to dive condition of individual rooms by checking thru-hull closures  (also of the Torpedo and Communication Sections).  The report of the Torpedomaaten [Torpedomen] as to the condition of the torpedo tubes and torpedo tanks goes to the Engineering Officer and the Watch Officer.
	48.  To perform the most precise weight calculation Section Leaders must provide the Zentralemaaten very precise information on the movement of weights and their location in the boat.
	49.  After each shipyard period or long cruise pause the Engineering Officer must personally check the overall condition of closures with reference to the diving board.
	50.  Free.
	C.  Reports
	51.  The Commander receives the following reports by the Watch Officer (meaning the responsible Section Officer in each case):
	a)  "Upper deck ready to dive",
	b)  "Torpedo armament ready to dive",
	c)  "Artillery ready to dive" and
	d)  "Communications ready to dive".

	- 17 -
	52.  The Commander receives the following message from the Engineering Officer:
	"Below deck ready to dive".
	53.  In boats with main ballast and reserve fuel oil tanks the state of the main ballast and reserve fuel oil tanks [whether they are configured as fuel oil tanks or ballast tanks] are included in the Engineering Officer's (not the Watch Officer's) report.
	54.  If the ready to dive condition of individual sections is only partly achieved, the preceding messages are qualified for example "Below decks ready to dive except for diesels".
	55.  If faults arise during the check of the ready to dive condition which can not be removed, this must be reported to the Commander.
	56.  The Commander is personally responsible for opening and closing the conning tower hatch.   After opening or closing the Commander notifies the boat:
	Commander:  "Conning tower hatch is open or closed".
	After the ready to dive condition report has been issued there should be no interruptions.  If however, an interruption is necessary, the Commander, the Engineering Officer and the Watch Officer must be informed simultaneously.
	57.  When starting or stopping the diesel engines or ventilators the Engineering Officer shall separately order the required opening and closing of the head and foot valves of the air shafts and posts shall report that execution has taken place.
	The opening and closing of the exhaust gas valves and valves and hull cut-off valves of auxiliary machinery and pumps is included in the order to start and stop the engine concerned.
	58.  Free.

	- 18 -
	59.  Free.
	60.  Free.

	- 19 -
	Section IV
	Leak test
	61.  A leak test must take place before every peacetime diving maneuver.  It can be performed as a positive or negative pressure test, normally as a negative pressure test.  For this purpose the barometer must first be set at the external pressure.
	62.  Condition of the boat:
	Boat is ready to dive, crew is at diving stations.
	Orders and reports:
	Commander:  "Closing conning tower hatch".
	Commander:  "Conning tower hatch off.  Negative pressure test".
	The Order:  "Coning tower hatch off" is passed to all rooms verbally man to man.
	63.  Engineering Officer repeats and then orders:
	"Turn on exhaust air fan" .
	"Open exhaust air head and foot valves".
	"Open exhaust air slidegate valves".
	Thereupon the reports are made by posts:
	"Exhaust air fan running".
	"Exhaust air head valve on".
	"Exhaust air foot valve on".
	"Exhaust air slide gate valves after- (fore-) ship on.
	64.  If the negative pressure in the barometer does not fall any further with the exhaust:
	Engineering Officer:  "Close exhaust air head and foot valve"
	Posts:  "Exhaust air foot valve off".
	"Exhaust air head valve off".
	Engineering Officer:  Stop exhaust air fan".
	"Close exhaust air slide gate valves".
	Posts:    "Exhaust air fan stopped".
	"Exhaust air slide gate valves aft (forward) off".

	- 20 -
	65.  After turning off the fan the following report is made to the Commander:
	Engineering Officer:  "Negative pressure x mb",
	Afterwards the report on the weight and trim condition of the boat.
	The Zentralemaat notes the time and after two minutes reports to the Engineering Officer: "Time is up".
	If the negative pressure holds after the conclusion of the waiting period, during which there is utmost quiet in the boat, the report is made to the Commander:
	Engineering Officer:  "Negative pressure has fallen x mb and is holding".
	66.  If the negative pressure does not hold, this is to be reported and the cause determined.  Decreases in the negative pressure are mostly due to leaks in the compressed air installation or in hull closures.  If it can not be determined with certainty which of the two causes is present, the leak test is to be repeated with positive pressure.  During the positive pressure test an increase in pressure indicates leaks in the compressed air installation, falling pressure indicates leaks in the shut-off valves of the pressure hull.
	Under no circumstances may the boat dive, before the cause of the leak is found and eliminated.
	When a negative pressure test is followed by submerged cruise, the negative pressure is maintained in the boat.
	67.  A leak test is to be performed after each interruption of the diving condition, i.e. after each opening of the torpedo or traffic hatches.  A new leak test is not required after opening the conning tower hatch and the hull closures necessary for operating the diesel engines (diesel air, exhaust valves, cooling water), for ventilating the boat (ventilation head and foot valve) and for the compressors.
	In the case of boats with pressure resistant bulkheads, from time to time a leak test of individual compartments should be done.

	- 21 -
	68.  Free.
	69.  Free.
	70.  Free.

	- 22 -
	Section V
	Trim test
	71.  A trim test shall be performed when the weight and trim condition of the boat has become uncertain due to any circumstances, e.g., after shipyard downtime, after ballasting, on fitting out.
	During the first trim test after the shipyard period the Flotilla Engineering Officer or his deputy must be aboard.
	The trim test is to be carried out in the calmest water possible.
	72.  To avoid the boat settling immediately after flooding, the boat is to be made as light as possible by pumping out the regulating and torpedo compensating tanks.  The filling of trim tanks is based on a rough calculation made beforehand.
	73.  Condition of the boat:
	Boat is ready for dive, crew is at diving stations, conning tower hatch is closed, leak test completed.
	74.  Orders and reports:
	Commander:  "Open flood valves, watertight bow and (as appropriate) watertight stern".
	The Engineering Officer repeats the command.  At the same time, the repetition is considered as an execution order to the sailors according their individual role in the operation.
	The flood valves and watertight bow and, if existing, watertight stern are opened by the sailors according to their role in the operation.
	75.  The Engineering Officer receives the following individual reports:
	Posts:  "Flood valves on".
	"Watertight bow on".
	"Watertight stern on".
	Engineering Officer to Commander:  "Flood valves, watertight bow, watertight stern on".

	- 23 -
	76.  Commander:  "Prepare to vent".
	Engineering Officer repeats the order.
	Posts:  "One . . . . . ready".
	Boats with vents operated by compressed air will proceed as follows:
	For peacetime diving exercises and, during the first trim test after shipyard period, for greater safety, the vents are moved by hand and locked.  Only with "Prepare to vent" are they moved by air and unlocked by order of the Engineering Officer.
	Orders for this:
	Commander:  "Prepare to vent".
	Engineering Officer repeats and orders:
	"Switch vents to air and unlock".
	Posts:  "Vents One, Two . . . . . . . switched to air and unlocked".
	Engineering Officer to Commander:  "Vents ready".
	77.  Commander:  "Trim test, flood at the discretion of the Engineering Officer".
	The Engineering Officer repeats the order and allows the vents to be opened.  In so doing, it is up to him to allow all vents to be opened at once or to flood the ballast tanks one after another.  However, it is important that the normal attitude of the boat is maintained and that only a slight down angle appears.
	78.  After opening the vents the reports to the Engineering Officer take place in numerical order of the ballast tanks.
	Posts:  "Vents One, Two, . . . . . . . . on".
	Engineering Officer:  "Vents on".
	79.  During flooding the bilges and drains of the air shafts and exhaust gas piping must be observed.  If a drain produces water, this is an indication that the concerned hull closure is leaking.
	All leaks are reported immediately to the Engineering Officer and forwarded to the Commander.

	- 24 -
	80.  In the case of leaks whose extent can not be overlooked or that require immediate counter measures, in principle the Commander gives the order, in urgent cases also the Engineering Officer:
	"Blow, close vents".
	If only "blow" is ordered, the order to close the vents is included.
	The same is done if the boat settles too deeply during flooding or takes on too great a bow or stern angle.
	81.  If the flooding maneuver runs normally, the order follows:
	Commander:  "Bring boat to x tons positive buoyancy and put in balance".
	Engineering officer repeats the order.
	The boat is brought to a positive buoyancy of approximately 2 tons by flooding the regulating tanks on the orders of the Engineering Officer initially without consideration of the trim.  Now the boat becomes sensitive in longitudinal stability and is oscillated by means of small trim adjustments to purge the residual air from the ballast tanks.
	The boat is brought to the ordered buoyancy by further flooding the regulating tanks.  From 2 tons of positive buoyancy the Engineering Officer continually reports decreases in the remaining buoyancy.
	82.  To execute a simultaneous test of the depth gauges, the boat is brought so far under water, that the conning tower deck just floods.   This condition is accurately determined by opening the test cock in the conning tower hatch.
	When the boat is brought so far under water that, according to the depth gauge indicator, the coning tower deck is just above the water surface, the Engineering Officer reports:
	Engineering Officer to Commander:  "Test cock just above the water".
	From this point only small quantities of water are flooded to exactly note the moment the conning tower deck is covered.  The moment the test cock makes water,

	- 25 -
	Commander to Engineering Officer:  "Zero, test cock under water".
	The test cock is closed and the Engineering Officer compares the depth meter.
	83.  During the flooding and pumping of the regulating tanks attention is to be paid to the list of the boat and it is to be removed.
	84.  If trimming with people is necessary, this should be carried out within the fore- and aftership, e.g., "Bow room two men forward".   On the order:
	Engineering officer:  "Rooms forward" respectively "astern".
	The crew is to run to the front or back of their compartments to the forward or aft watertight bulkhead.  On the order:
	Engineering officer:  "Section forward" respectively "astern".
	They run in each case up to the pressure resistant bulkhead in the control room or in the end rooms.
	If particularly strong trim effects are required, it is extended to the entire length of the boat:
	Engineering officer:  "All men forward or astern".
	In each case only dispensable sailors run.  Helmsmen, control room teams and the operating team of the motors remain at their posts.
	At the order:
	Engineering Officer:  "To stations".
	The sailors run again to their diving stations according to their role.
	85.  Pumping and flooding of the regulating tanks is ordered only with "Pump" and "Flood" stating the quantity in liters or metric tons.  Preparatory orders such as "Standby to pump" must not be issued.
	Pump, flood and trim orders must always take place with an indication of quantity to definitely set a limit for the weight and trim change.

	- 26 -
	86.  Now the boat is oscillated to at least 3° bow and stern down two times, to ensure that the residual air can escape from the ballast tanks.  Then, when oscillating is finished:
	Engineering Officer to Commander:  "Boat is oscillated".
	87.  Commander:  "Close vents".
	The Engineering Officer repeats the order which is considered at the same time as an execution order.  The vents are closed and reported to the Engineering Officer.
	a)  In medium boats:
	Posts:  Vent One, Three both, Two-Four both off and secured".
	"Five off and secured".
	The report of the Post vent five takes place only after the reports of one to four.
	b)  In large boats:
	Posts:  "Vent One, Two-Three are off and tried".
	"Vent Four-Five are off and secured".
	"Vents Six-Seven, Eight are off and tried".
	By Posts in the number order of the ballast tanks. (Four and Five are switched to manual when preparing to surface.)  Tried means: safety pin fully inserted, rotated 90°, turned back and removed again.
	Engineering Officer to Commander:  "Vents off".
	88.  When balance and trim are established as ordered, report:
	Engineering Officer to Commander:  "Buoyancy x tons, boat balanced".
	(The buoyancy the boat has with conning tower deck just flooded is to be indicated.)
	Commander:  "Note contents".

	- 27 -
	89.  Engineering Officer repeats and orders:
	"Prepare to sound".
	Soundings are always taken on:  regulating tanks, trim tanks, torpedo compensating tanks, waste water, drinking water, wash water tanks and bilges (in liters), if necessary also lubricating and fuel oil tanks and sounding comparison completed.
	The reports of readiness to take the soundings go by rooms in the direction of the control room.  The passed report includes individual readiness, so that the Engineering Officer receives only the compartment reports:
	Posts:  "Fore- (After-) ship ready to sound".
	and
	"Control room ready to sound".
	90.  Before the trim indicator goes to zero:
	Engineering Officer:  "Attention sounding".
	A moment before passing through:
	Engineering Officer:   "Zero".
	At zero the soundings are carried out and the results are reported to the control room for entry in the diving logbook.
	91.  These readings are to be made with great care, since they form the basis for the trim calculation.  Therefore they are to be repeated in case of disagreement.
	Simultaneously the specific weight of the sea water is measured and is also entered in the diving logbook.  In taking this measurement it must be ensured that the specific weight meter is clean and free of grease, oil and air bubbles (let the water run in slowly) and that the water runs off long enough, to ensure that water outside the hull gets into the measuring glass.  The specification of specific weight takes place by noting only the thousandths, e.g., 1.2 instead of 1.0012 or 13.5 instead of 1.0135.
	92.  After noting the contents the trim test is finished.  Whenever possible a submerged cruise is conducted, or the boat is surfaced.

	- 28 -
	93.  In boats with compressed air-operated vents the opening and closing of the vents by hand is to be practiced occasionally.
	94.  Free.
	95.  Free.
	96.  Free.
	97.  Free.
	98.  Free.

	- 29 -
	99.  Free.
	100.  Free.

	- 30 -
	Section VI
	Test dive
	101.  While accurate documents concerning weight and trim are generally not available during the trim test, for the test dive these values are taken from the last dive as well as from the known weight and trim changes that have taken place since then.  Therefore, the test dive is carried out with calculated fillings of the regulating tanks and trim tanks and the dive represents the practical test for the correctness of the calculated values.
	The stronger the sense of responsibility is maintained for co-operation in the boat, the better the calculated fillings will agree with those actually necessary.
	102.  Speed and confidence in the execution of test dives are an important training goal.
	103.  The purpose of the test dive is the achievement of correct weight and trim condition, i.e. the boat becomes balanced.  Furthermore, the test dive serves as a validation of the readiness to dive.
	It is to be executed during peace as in war each day at sea, furthermore after each conversion of a main ballast and fuel oil tank to a ballast tank and after upper deck torpedoes are taken into the boat.
	104.  Sequence of the test dive:
	Commands and reports, see Section V and XII.
	At the diving location the specific weight of the sea water is measured one more time and if necessary, the filling of the regulating tanks is adjusted.

	- 31 -
	The Engineering Officer is to be informed of the existing water depth.  The boat is ready to dive, the leak test completed, diving stations occupied.
	105.  At the order "Flood" the vents are opened except for vent One, in order to tilt the boat quickly and is only opened later by the separate order of the Engineering Officer "One".  If this order is not given approximately 5 seconds after the flood order, the Post reminds him by "Question One ".
	106.  The boat is dived at a down angle of 5-8°.  In so doing, the ordered depth is initially overshot by about 2-5 meters, then the boat is oscillated twice 3-4° up and down and the ordered depth is approached from below.
	If the oscillation is conducted with insufficient up and down angle, residual air remains in the ballast tanks.   As a result, smooth depth control is made impossible because with every depth change the air occupies a different volume so that when going deeper the boat becomes heavier and when coming shallow becomes lighter (the boat cycles on an air bubble).
	107.  After the report of
	Engineering Officer:  "Boat has been oscillated".
	The order always follows
	Commander:  "Close vents".
	108.  Generally, the balancing of the boat takes place for the smallest speed settings at periscope depth and 1/2-1° bow down. (In a rough sea or strongly out of trim boat, pre or coarse balancing including soundings takes place as appropriate at a depth of 20-60 meters.)  Mistakes which are made during balancing concerning the down angle may have a particularly disastrous effect.  After balancing the boat must, in every situation which can arise during attack, be secure in the hands of the Engineering Officer, without making changes in the fillings.  Therefore, particular emphasis is to be placed on accurate balancing during training.

	- 32 -
	109.  The Engineering Officer establishes the correct weight and trim condition of the boat and has soundings taken.  The contents of all liquid tanks and all bilges are measured and recorded in the diving log book.
	Engineering Officer to Commander:  "Boat is balanced for one (both) motors at Ahead KF (LF) [KF = dead slow, LF = slow], at x meters 1° down angle.  Contents are recorded (or taken, to be recorded)".
	110.  Free.

	- 33 -
	Section VII
	Crash diving
	111.  The crash dive is a wartime maneuver and forms the basis of front training of a crew.  Therefore, routine preliminary training for crash diving including timing is particularly important.  It is to be done as often as possible and gradually to be made more demanding.  Only the certainty that every man of the crew handles the measures and controls he is responsible for with absolute certainty allows the Commander to carry out the crash dive in wartime.
	112.  During advanced training the crash dive is to be practiced under the following aggravating conditions:
	a)  While blowing with compressed air or blowing out the ballast tanks with diesel exhaust,
	b)  During charging with a disengaged shaft.
	Additionally, surfacing during a previously initiated crash dive maneuver is to be practiced.
	113.  Generally, before the beginning of crash diving exercises a leak test and test dive must take place.  Attention must be paid to sufficient water depth.
	114.  The sequence of the crash dive maneuver is as follows:
	The boat proceeds on the surface on both diesel engines. (During exercises all propulsion levels are to be applied alternately.  During advanced stages of training: both engines Ahead GF and Ahead 2 x GF.) [ GF = 3/4 speed, 2 x GF = full speed] flood valves of the ballast tanks, vents of the waterproof bow and the watertight stern are open.  Trim and weight of the boat are to be maintained according to the most recent

	- 34 -
	test dive.  The watch is at wartime cruising stations, the off duty watch in the living-spaces.
	115.  Order:  "Alarm!"
	The helmsman sounds the alarm bell and shouts "Alarm".  He immediately puts both engine telegraphs on "Dive", switches the receivers to "Both rooms", turns off the alarm bell and, finally, switches the engine telegraph receivers to "E motor".  The engine telegraphs remain set on "Dive", until the E motor is set for Ahead GF or another propulsion level is ordered by the Commander.
	116.  Every man of the crew repeats the order aloud, so that it is guaranteed that even the sleepers are awakened by the order.  Particular attention must be paid to the loud exclamation of the order because the noise still prevalent in the boat must be overcome and the order must get into the diesel engine room even in the event of the failure of the alarm bell, flashing light and engine telegraphs.
	117.  Crash dive is always performed by the watch in accordance with the assignment board (e.g., in the type VII additional calling up of the off-duty Obermaschinisten [Chief Machinist] and Zentralemaaten).  Assignments are to be distributed so that the alarm diving maneuver can be always executed by the watch.
	118.  The diesel engines are shut down immediately, the diesel clutches are disengaged, the E motors are switched to Ahead GF (without further order), all air intake head and foot valves and the outer exhaust gas flap valves and inner exhaust gas valves are closed.
	The diving planes are set "Forward hard down", "Aft midships".
	119.  In addition to any existing indicating system the Engineering Officer receives the following report verbally:
	From the diesel engine room via the control room "Ready". (Report includes the diesel exhaust gas valves and foot valves, in large boats the ventilation air exhaust and intake head valves as well as activating and switching the ventilation air to central ventilation.  The forwarding from the back of the control room includes the head valves.)

	- 35 -
	In boats with indicating system displays the brightly burning lamp shows that the hull closure is off (if there is no light then further inquiry is absolutely required!)
	120.  Thereupon
	Engineering Officer to Commander:  "Ready".
	Watch Officer to Engineering Officer "Is off", when conning tower hatch is latched.
	Commander:  "Flood".
	121.  Engineering Officer repeats the order.  The vents are opened, vent One on the order
	Engineering Officer:  "One".
	To avoid steep down angle, if necessary Posts remind the Engineering Officer of vent One by
	Posts:  "Question One".
	Posts report to the Engineering Officer that the vents are open in the order of the numbers of the ballast tanks.
	122.  Thereupon
	Engineering Officer to Commander:  "Vents on".
	Commander:  "Go to depth x meters".  (At the front usually to 80 meters).
	The Engineering Officer repeats the order and passes it to all rooms.
	123.  While flooding E motor room and diesel engines are made completely ready to dive and are reported to the Engineering Officer.  Posts: "Aftership ready to dive".
	The pressure gauges of the cooling water piping are to be monitored, as well the drains of the gas spaces of the exhaust gas piping.
	124.  Once the down angle indicator indicates, the upper deck is flooded, and the boat quickly assumes a down angle.  In general, it should be dived so that the upper edge of the bridge bulwark and the stern submerge at the same moment.  Accordingly, for every type of boat, the degree of the down angle is established:
	Type II and VII:  8 to 15°,
	Type IX C, IX D, XB and XIV:  7 to 12°.

	- 36 -
	125.  Only in experienced boats in service at the front may the rear diving plane may be put down at the start of the diving maneuver with small deflections.   In large boats it is appropriate to augment with "Aft down" and is permissible.  The limit is dependent on the type of boat and the state of training of the crew.  When the boat is down by the bow, the rear diving plane is immediately set up appropriately to avoid an excessive down angle.  Large boats must augment according to the desired down angle with "Aft down".
	126.  In most cases, crash diving at the front depends not only on getting away from the surface as quickly as possible, but also on reaching a greater depth as quickly as possible.  For this purpose from 20 meters the boat is to be vigorously tilted (as appropriate with a change of course) and quickly driven deeper at down angles of 15 to 30°.
	127.  Free
	128.  Free
	129.  Free

	- 37 -
	130.  Free
	A.  Negative buoyancy tanks
	131.  Boats with negative buoyancy tanks will proceed as follows:   If the boat is ready to crash dive the negative buoyancy tanks are kept filled while running on the surface, so that the boat is given a negative buoyancy corresponding to the size of the ballast tanks.  After execution of the order "Flood" and the boat has a noticeable descending tendency, the negative buoyancy tanks are expressed, on the order of the Engineering Officer "Express".
	[Note:  in English the command "Blow" is used to empty both ballast tanks and negative buoyancy tanks (quick diving tanks) with compressed air.  In German there is a distinction between these two types of tanks.  The command to blow ballast tanks is "Anblasen" and the command to blow the negative buoyancy tanks is "Ausdrucken".  This distinction is preserved in this translation by using the word "Express".]
	The best time for expressing for medium size boats is a depth of approximately 8 to 10 meters, for large boats a depth of 10 to 12 meters.  Experience shows that the primary effect of the negative buoyancy tank is in faster breaking through the water surface while diving.  Because reaching of great depths quickly is almost exclusively dependent on the down angle and the propulsion setting (approximately 25 to 30°, 2 x GF.), it is wrong to express the negative buoyancy tanks at greater depth, because the extremely small advantage gained is in no relation to the danger in which the boat can be placed in such a case.  In particular, air consumption and the time to express are increased considerably.
	132.  Engineering Officer:  "Express".
	Thereupon the "Express negative buoyancy tank" valves are fully opened and expressed at the highest possible pressure (20 to 30 technical atmospheres = at).   While doing this, the "Residual water check" lines are monitored and, once air escapes, the flood valve is quickly closed.   If both have air, the "Express negative buoyancy tanks" valve is partly closed at 5 to 10 at and completely closed as soon as both

	- 38 -
	flood valves are closed.  Calls for not-expressing
	Posts:  "Air".
	"Is off".
	After expressing is completed the negative buoyancy tanks are checked once more at the  "Residual water check" lines, then a report is made to the Engineering Officer about expressing.
	Posts:  "Negative buoyancy tanks expressed".
	133.  The pressure difference meters are to be monitored, particularly during expressing (danger of rupture with closed flood valve) and when the boat rises.  More than 2 at higher than outboard pressure is prohibited and must be equalized.
	Equalization takes place after previous request to the Engineering Officer (for passing on to the conning tower) by complete opening of the "Vent negative buoyancy tank" valve, appropriately up to an internal pressure of 1.5 at (external pressure at periscope depth).
	134.  Free.
	135.  Free.
	136.  Free.

	- 39 -
	137.  Free.
	138.  Free.
	139.  Free.
	140.  Free.
	B.  Pre-flooding forward ballast tanks wile crash diving
	141.  Preflooding of the forward or forward and center ballast tanks is prohibited for boats in the homeland.
	142.  Proceeding with preflooded ballast tanks is prohibited because cruising speed and stability are thereby reduced.  The boat can settle and undercut with vents not completely shut, especially at night, without this being noticed by the bridge-personnel in time.  The time gain made possible by preflooding stands in no relation to the danger to the boat associated with it.

	- 40 -
	143.  If the order to crash dive is given again while blowing, no premature opening of the forward vents may take place in this condition.
	144.  The diving times of medium boats are so favorable - in general they are under half a minute - that in general preflooding is not necessary.  It is left to the judgment of the Commander whether boats at the front open the vent of the ballast tank Five on crash diving without further notice.  This may depend on the weather conditions, the state of training of the boat and other special circumstances.
	However, the Commander must ensure that there is always clear instruction about whether it should be preflooded on crash diving or not.
	145.  In large boats (type IX C, IX D, X B and XIV) the pre flooding of the forward ballast tank or the forward and center diving tanks on crash diving is left to the judgment of the Commander.
	In well run front boats it is customary and there is no objection to it.
	146.  Free.
	147.  Free.

	- 41 -
	148.  Free.
	149.  Free.
	150.  Free.

	- 42 -
	Section VIII
	Submerged Cruise
	A.  General
	151.  The boat is balanced for Ahead KF (or LF) at x meters 1° down angle.
	152.  Orders of the Engineering Officer about the depth to be steered are repeated by the forward planesman and about the angle to be steered by the rear planesman.  In contrast to rudder helmsman, diving plane position orders are not repeated, but are implemented immediately and their execution is also not reported.
	153.  The ordered depth is given to all rooms by the Engineering Officer verbally man to man.  Bow and stern rooms compare this report to their depth gauges and report discrepancies of more than 10 meters.
	154.  In the boat strict silence prevails, every non essential movement to and fro must be avoided.  The changing of the watch takes place by exchange of individual sailors. Things are handed over, not gotten.  Every use of pumps, including hand pumps (cook), may take place only by approval of the Commander.
	155.  As soon as it is possible, [i.e. when the regulating and reserve fuel oil tanks have been converted for use as regulating tanks] two regulating tanks are to be cross connected ready to flood and two regulating tanks ready to pump, namely one about half-full under 3 to 4 at as a shallow pumping regulating tank, the other approximately 2/3 full under 10 to 12 at as a deep pumping regulating tank.  Boats with only two regulating tanks operate one as a flooding regulating tank, the other as a deep pumping regulating tank.
	The drain in the blowing distributor is opened a little bit, so that no residual air can get into the ballast tanks and form air bubbles.

	- 43 -
	The low pressure measuring range gauges (diesel exhaust blowing gauge and suction pressure gauge of the drain pumps) are secured and vented.
	The bilges are to be observed constantly.  They are sounded every hour and reported to the Engineering Officer.
	156.  All work or movement of the torpedo armament which causes weight or trim changes must be approved by the Engineering Officer, because depth control is greatly affected  thereby.
	Hard over rudder positions make the boat strongly down by the stern.  Therefore, the rudder helmsman must always announce the hard over position with the report:
	Helmsman:  "Rudder over 15".
	If he puts the rudder amidships again, he reports:
	Helmsman:  "Rudder coming in".
	The Engineering Officer confirms this report by repeating.
	157.  During longer dives air is to be sampled  hourly starting at 4 hours.  The O2 content may decrease to 18% and CO2 content may rise to 2%.
	158.  Free.
	159.  Free.
	160.  Free.

	- 44 -
	B.  Cruising at periscope depth
	161.  At periscope depth the Engineering Officer continually reports depth and tendency of the boat for deviations of more than 20 to 50 cm (depending on sea state).
	162.  In heavy seas getting too shallow is particularly dangerous.  If necessary the Engineering Officer must immediately take vigorous counter measures, i.e. request higher speed, flood, fill the negative buoyancy tanks, at the broaching of the boat order: "Open vents".
	163.  Pumping generally takes place by air from the shallow pumping regulating tank.  It is expedient when balancing and pumping larger quantities, if the situation allows, to pump from a flooding regulating tank.
	Trimming always takes place by air.
	164.  Hydraulic oil for periscope drive is pumped up by hand by the Zentralemaat without separate order.  If if the bottle pressure has fallen to less than 60 kgs/cm², after the previous announcement:
	Zentralemaat:  "Pumping hydraulic oil".
	165.  When operating the periscope complete extension and retraction of the periscope is reported from the conning tower to the control room with:
	Commander:  "Periscope extended (retracted)".
	166.  With completely extended periscope a constant periscope comparison takes place:
	On undercutting:
	Engineering Officer:  "Periscope cut under".
	Commander:  "Zero".
	Engineering Officer:  "x meters".
	On coming free:
	Engineering Officer:  "Periscope comes free".
	Commander:  "Through".
	Engineering Officer:  "x meters".

	- 45 -
	167.  Free.
	168.  Free.
	169.  Free.
	170.  Free.
	C.  Going quickly to 20 meters.  Going quickly to periscope depth.
	171.  "Go quickly to 20 meters" is to be regarded as an emergency maneuver.  Therefore, it must be executed quickly and energetically.  In so doing, it is desirable that the down angle remains at 5 to 8°, so that the stern is not higher than the bridge bulwark.

	- 46 -
	172.  Commander:  "Go quickly to 20 meters".
	Engineering Officer:  Repeats the order.
	The rudder helmsman sets the engine telegraphs on Ahead GF, both plane helmsmen set "hard down", generally, the aft diving plane holds the down angle.
	173.  To avoid commotion in the boat do not trim with people. (Except in small boats.)  It is ineffective in medium and large boats because of control perturbation.  The effect starts comparatively late and then is more difficult to bring under control.
	174.  The ordered depth is somewhat exceeded and headed to from below as speed is decreased.
	175.  Free.
	176.  The opposite maneuver "Go quickly to periscope depth" is also performed quickly.  Before complete silence in the boat and listen!
	It is important that the boat passes quickly through the ramming danger zone, 20-13 meters, while getting the periscope free at very low speed (spray streak) and no angle slowly continuing to rise.   Getting stuck shortly before the periscope is free must be avoided as well as coming too shallow.
	177.  "Go quickly to periscope depth“.
	Engineering Officer repeats the order.
	The boat is brought up by increasing speed and by energetic tilting of the diving planes to approximately 3 to 5° stern down.  Meanwhile the Zentralemaat pumps hydraulic oil up.

	- 47 -
	178.  At 18 meters speed is decreased, and the periscope is extended.
	The Engineering Officer reports to the Commander at 18 meters and from 2 meters before periscope depth constantly reports the depth with vocal emphasis from which the tendency is recognizable.
	Engineering Officer:  "Periscope comes free".
	Commander:  "Through".
	Engineering Officer:  "x meters".
	179.  With this maneuver getting too shallow is particularly dangerous.   As soon as this danger exists, energetic counter measures are to be taken immediately.
	If the boat was balanced at 20 meters or deeper, it must be flooded a certain minimum amount for driving at periscope depth according to the sea state and type of boat.
	180.  Free.
	D.  Cruising at great depths
	181.  To proceed to great depths (more than 40 meters), the Engineering Officer gives the depth order and the depth changes in increments of 10 meters to all rooms verbally man to man.
	Because the boat loses volume at greater depth, it must be made lighter by timely pumping (for type VII boats approximately 1 ton per 100 meters).  It is appropriate to pump out a greater amount, because the boat will be heavier by the accumulating leak water anyway.
	182.  From 20 meters the outer doors of the torpedo tubes are to be closed in consideration of the torpedoes.  The depth meters for shallow depths are to be switched off and vented in good time.  Diving plane helmsmen report the switching on/off with:
	Helmsman:  ". . . . . . . . depth meter switched on- (off)".
	To avoid confusion, which depth meters are switched off is to be turned over at each watch change.

	- 48 -
	183.  From 40 meters greater attention is paid to all shut-off valves and pressure hull openings as well as the bilges.
	The periscopes are to be placed on the buffer.   The main drain pump is to be switched to serial connection.  With sufficient discharge head pumping can be done with the pump alone, at sufficiently high pressure of the deep pumping regulating tank by air alone.
	184.  If the tightening of hatches or other valves is necessary, sailors are to be assigned to loosen them about the same amount when ascending.  The same is to be done for the glands of the stern tubes.
	Water intake, particularly in the exhaust gas valves and glands of the stern tubes, is to be reported to the Engineering Officer immediately.
	185.  Pumping at great depth is accomplished with the main drain pump (serial connection) from a pressurized regulating tank.  In the course of this, the static head of the pump, i.e. the pressure difference between inlet (regulating tank pressure) and outlet (outboard pressure), may not be greater than 8 at.  If a regulating tank is set at more than 14 at, to avoid tearing the bulkhead, the adjacent pressure resistant tanks (negative buoyancy tank, regulating and auxiliary fuel oil tank) are also to be put under some pressure.
	186.  During prolonged cruising at great depth the boat becomes too heavy and down by the stern by water intake (stern tubes, exhaust gas valves).   With required silent running (listening pursuit) it is always better to steer on an air bubble, than to become heavily down by the stern.  For this purpose, the center ballast tank is blown briefly (3 to 5 seconds) and heavily (20 to 30 at), several times if necessary .
	The water from the aftership is pumped by means of hand drain pump or the auxiliary bilge and trim pump into a non-pressurized regulating tank (if necessary also by bailer in the bow room and control room bilge).

	- 49 -
	187.  When steering with an air bubble in calm seas, the blown ballast tank is to be vented into the boat in short sips as the boat rises, according to the expansion of the air bubble.  The expansion of the air bubble is exceptionally low at great depths.  Migration of the air bubble and bilge water make the boat longitudinally unstable.  However, depth control is not too difficult, if significant longitudinal buoyancy changes, and above all, buoyancy reversal are avoided.
	188.  Free.
	189.  Free.
	190.  Free.
	191.  Blowing all ballast tanks at great depths is restricted to special emergencies (settling in the case of water entry), because compressed air consumption is very high. Air is lost as the boat rises, because the boat is already completely blown.  In the case of unequal blowing an initially low heeling or bow up/down angle will be much bigger on rising, because the air takes the path of least

	- 50 -
	resistance.  In such cases the appropriate blow valves are to be cracked to decrease the heeling or bow up/down angle.
	If the boat is to remain submerged, the vents must be opened again very early (open One later, if necessary blow One strongly later so that the boat becomes bow heavy).
	192.  If the boat is coming from great depth to periscope depth, an intermediate stop is to be inserted at 20 meters to balance and thoroughly listen.
	193.  Free.
	194.  Free.
	195.  Free.
	E.  Silent Running
	196.  At the order "Silent running" the E motors are set for silent running revolutions. This is established for each boat by sound trials.  The engine telegraph is set on the propulsion setting nearest to this revolutions.

	- 51 -
	197.  All auxiliary motors in the boat are secured except for the gyro-compass installation, diving plane motors, rudder motor and 0.3-kW sound converter.  These are switched off only by special order of the Commander.
	The light voltage is regulated down to 90 to 100 volts (the latter for the gyro-compass transformer).
	198.  In the boat there are only whispers, even as required orders are conveyed by voice and telephone.  Even the slightest noise must be eliminated, e.g., rattle of pots, required movements take place silently.
	199.  The command for ending silent running is:
	Commander:  "End silent running".
	200.  Free.

	- 52 -
	Section IX
	Surfacing
	201.  After the commander has satisfied himself by visual sweep and sound bearings that the boat can surface, he gives the order:
	Commander:  "Prepare to surface",
	and orders the outfit for the bridge watch.
	The Engineering Officer repeats the order and passes it verbally man to man to all rooms.
	202.  The boat does not yet go higher.
	One diesel engine is made ready to blow and the other for cruise immediately after surfacing.  The order includes permission to operate the auxiliary lubricating oil pump. The compressors are made ready for use.
	The vents are checked one more time, to ensure they are closed and are reported to the Engineering Officer.
	The negative buoyancy tanks are equalized to outboard pressure.
	Excess pressure of more than 40 mb is to be pumped off with the electric compressor, if possible, to prevent carrying away acid when opening the conning tower hatch.
	Meanwhile, the bridge watch prepares and stays ready.
	203.  The independent reports to the Engineering Officer are:
	Posts:  "Vent . . . . . . . . checked, off and secured".
	(Accordingly in large boats:  tried.)
	Diesel:  "Diesel ready, starboard drive".
	Zentralemaat:  "Negative buoyancy tanks equalized".
	Bridge Mate:  "Bridge watch ready".

	- 53 -
	204.  Engineering Officer to Commander:  "Below decks ready to surface, starboard drive, positive pressure x mb".
	Commander:  "Surface".
	Engineering Officer repeats the order and passes it verbally to all rooms man to man.
	The drains of the blowing distributors are closed, the electric compressor is operated and the diesel-foot valve required for later pressure equalization is half opened.
	205.  To surface, the boat goes to GF Ahead because, if immediate diving is required (aircraft alarm), high speed is absolutely necessary.  The boat is angled stern down and driven up dynamically with diving planes "Forward hard up", "Aft up 5-10".  They report:
	Engineering Officer to Commander:  "Boat rises"  and immediately orders
	Engineering Officer:  "Open negative buoyancy tanks" (flood valves are opened).
	Engineering Officer to Commander:  "13 meters, 12" meter by meter.
	206.  Commander:  "Blow".
	Engineering Officer repeats, Zentralemaat blows without delay.
	While blowing the negative buoyancy tanks are filled without further orders.
	Engineering Officer to Commander:  "Conning tower hatch free", order concluded at 7.5 meters.
	Engineering Officer:  "Equalize pressure".
	On this order the (in large boats the starboard) diesel air intake head valve, with close observation of the associated drain, is opened 3-4 turns.  Pressure equalization takes place only by order of the Engineering Officer.
	Now the Commander cranks the conning tower hatch open, however, the pawl must be latched.

	- 54 -
	207.  For every type of boat a special blowing order is issued which indicates which ballast tanks are to be blown.  The position of the blow valves in the blowing distributor should correspond to this intent.  In boats with several battery charging options it is broken down so that the same ballast tanks are blown for each battery charging option.
	The aft ballast tank is always blown, because should it become necessary to crash dive while surfacing the boat would settle bow down only with difficulty.
	208.  If the boat is out and sufficiently blown and, after the first brief dip, appears to have no tendency to settle further, there follows:
	Engineering Officer to Commander:  "Boat is out" and
	"Pressure equalization complete (or over pressure still 80, 60 . . . . . . . . mb)".
	Commander:  "Stop blowing".
	Engineering Officer repeats.
	209.  The Commander opens the conning tower hatch by unlatching the pawl.
	Commander:  "Conning tower hatch open".
	Engineering Officer repeats and passes the order verbally to all rooms man to man.
	Now the head valve, used for pressure equalization, is closed immediately again and reported to the Engineering Officer.
	Posts:  "(Starboard) Diesel air intake head valve off".
	210.  The Commander goes to the bridge, as well as the Watch Officer, and orders, if all is clear above:
	Commander:  "Blow with diesels", "Set the bridge watch".
	Engineering Officer repeats the orders, the bridge watch takes position, but a diving planesman remains to monitor the down angle and depth.
	Engineering Officer: "Open diesel air intake head and foot valves", "Start diesel to blow".

	- 55 -
	The blow valves, set in accordance with blowing order, are opened.
	Posts:  "Diesel air intake head and foot valves on".
	The blowing diesel starts running and is reported
	Posts:  "Blowing diesel runs".
	211.  For each type of boat a special blowing order is issued which indicates the order of the ballast tanks while blowing.
	In boats whose blowing piping is not routed down to the residual water level, the exhaust valves in the control room may not be opened until the blowing pressure meter indicates the prescribed pressure.  In this case, therefore, the diesel engine must regulate blowing pressure with the outer exhaust gas valve when starting.
	212.  Engineering Officer e.g.:  "One and Five blowing".
	The filling of the negative buoyancy tanks is reported to the Engineering Officer
	Posts:  "Negative buoyancy tanks filled".
	During the surfacing maneuver the Engineering Officer stands beneath the control room hatch and ensures calm and diving discipline in the boat.  No one needs to go to the control room.
	While blowing the diving planes remain set "Forward up hard".  Engineering Officer and Zentralemaat continually monitor depth, down angle and blowing pressure.
	213.  Both E motors still run at GF Ahead, for the drive side
	Commander:  "Starboard (port) motor stop".
	"Starboard (port) switch to diesel",
	After the completion report of the helmsman
	Commander:  "Starboard engine Ahead LF (HF)".  [HF = half speed]
	As soon as the driving diesel is turning, for the E-motor side
	Commander:  "Port (starboard) motor stop".
	In wartime starting the driving diesel takes place as soon as the boat is out.

	- 56 -
	214.  The bridge informs the control room which ballast tanks are blown.  The appropriate blowing valves are closed.  The blowing time must be continually monitored by the Engineering Officer by stopwatch, because at night in rough seas observation of blowing is often not possible.  In this case
	Engineering Officer to Commander:  "Blowing ended".
	otherwise normally by observation of the bridge
	Commander:  "All blown".
	Engineering Officer repeats.
	215.  Engineering Officer: "Stop blowing with diesel" (show clenched fist).
	Posts:  "Diesel blowing stopped".
	After blowing the diving planes are placed "Forward up seven" and "Aft up five " and the switch buttons are secured  to prevent unintentional positioning.
	The diving planes remain in this condition during surface cruise to fight against the danger of under cutting.  During surface cruise the control room watch observes the unchanged position of the diving planes at regular intervals.
	216.  Commander: "Secure from diving stations, boat remains ready to submerge".
	"Boat remains ready to submerge" means: all hull closures remain closed except for those operationally necessary.  The order "Secure from diving stations" must not be given until the ballast tanks are completely blown out.  Should the boat remain on the surface in a partially blown condition for a longer time, the crew always remains at diving stations except for the bridge watch.
	217.  If necessary before the order "Secure from diving stations" is given,
	Commander:  "Close flood valves, watertight bow, water tight stern".
	Engineering Officer repeats the order, which also serves as an execution order.

	- 57 -
	Posts:  "Flood valves off".
	"Watertight bow, watertight stern off".
	Engineering Officer to Commander:  "Flood valves, watertight bow, watertight stern off".
	218.  Also the blowing diesel can be used immediately after blowing is completed, i.e. it can be switched without a request.
	219.  During peacetime the hatches in the upper deck may be opened, weather permitting, only by separate order and only when all ballast tanks are blown and the flood valves are closed.
	220.  After closing the flood valves the blow valves in the blowing manifold for the ballast tanks and ballast and reserve fuel oil tanks whose flood valves are closed must also be closed.
	221.  During or after surfacing the following takes place
	a)  Compressing air.  The compressors are employed by the engine operating team automatically (electric compressor while surfacing, diesel compressor, as long as a diesel is running) and they report
	Posts:  "Both compressors running"  (or "Electric or diesel compressor running")
	b)  Ventilating the boat and afterwards of the battery by the fan.
	c)  Pumping the bilges after previous request to the bridge.
	After pumping the main drainage piping is flooded and flushed and the pump rinsed by pumping from sea to sea to free the pump and piping of oily residue, afterwards the filters are exchanged and cleaned.  Flushing the main drainage piping takes 1/2 minute (if longer: Caution! Battery bilge!).
	d)  Charging the battery if necessary.  The Engineering Officer personally checks the vacuum pressure of the battery and orders
	Engineering Officer:  "From Engineering Officer switch to charging".

	- 58 -
	Only on this order is charging switched to on the part of the E motor and is reported back:
	Posts:  "To the Engineering Officer and Bridge, charging switched to".
	222.  Free.
	223.  Free.
	224.  Free.
	225.  Free.
	226.  Free.

	- 59 -
	227.  Free.
	228.  Free.
	229.  Free.
	230.  Free.

	- 60 -
	Section X
	Lying on the bottom, rising from the bottom
	231.  After the order "Head for the bottom", "Employ depth sounder" the boat is brought to depth with small down angle (2-3°) and low speed.  To avoid damage to the rudders and screws, up angle is to be prevented by all means.
	In waters with strong current the bottom is headed for with greater down angle (3-7°) against the current.  With the danger of blowing sand the periscope is to be extended up to the smooth neck before heading for the bottom.  At depths more than 60 meters the periscope must always be put on the buffer.
	232.  The Engineering Officer passes to all rooms verbally man to man
	Engineering Officer:  "Boat heads for the bottom".
	When the depth sounder indicates only 2 meters under the keel, the motors are stopped.  When bottom contact is noticed in the boat (light tremor in the boat, down angle indicator goes to zero, depth meters shows no further falling), the report follows
	Engineering Officer to Commander:  "Boat has touched the bottom, water depth x meters", thereupon
	Commander:  "Settle the boat".
	233.  The Engineering Officer repeats the order and orders the flooding of the regulating tanks or filling the negative buoyancy tanks.  At the same time the specific gravity of the sea water is measured.  Generally, a negative buoyancy of 1-2 tons is sufficient to settle the boat.   Slight down angle is appropriate.
	In rough seas rocking of the boat can be eased by an increase in negative buoyancy.  However, too great a negative buoyancy lowers the stability of the boat too much, so that the rolling motions become even stronger.  If no relief from rocking is achieved by increasing negative buoyancy, the boat is to be laid on the bottom with little negative buoyancy and slight bow down angle.

	- 61 -
	With current of low strength one tries to fix the boat on the bottom with negative buoyancy.  However, in current as light as 1.5-2 knots the boat is easily moved sideways, it rolls, bumps and floats.  Then it is better to set the boat down on the bow slightly heavy.
	234.  If, despite all measures, the boat can not be brought to a safe position on the bottom, if the other circumstances allow, it is better to rise from the bottom and to stay in the vicinity of the targeted ship's position by diving at lowest speed.
	If the boat rises even though negative buoyancy should be present, then first the vents are to be opened again, so that any misplaced air can escape.
	235.  After settling the boat, the bottom watch is set; the watch always includes an officer (Engineering Officer or Watch Officer), if the situation and training condition allows, also a senior machinist.  The remaining strength of the watch depends on the type of boat and the situation.   Except for the officers (the Watch Officers go on watch) the bottom watch is made up of technical personnel.
	236.  While lying on the bottom, the depth meter, trim indicator, down angle indicator, gyro-compass, pressure gauges of the regulating tanks and bilges are monitored continually and the determined values are noted and written down every half hour.   Unusual noises are to be reported immediately.  When lying for a long time air quality tests are to be carried out and appropriate air purification and required oxygen provided.
	With a muddy bottom, clogging of the depth meter may occur, which can be determined by a comparison with the pressure gauges in the cooling water piping or in the discharge line of the main drain pump.   As a preventative measure, the depth meter lines of turned off depth meters are to be blown out.  Lying on the bottom with a muddy bottom or loose sand banks is to be avoided particularly with current or in storms, since the danger of silting up exists.

	- 62 -
	237.  If the boat is to be raised from the bottom, the order follows:
	Commander:  "Raise boat from the bottom".
	"To diving stations".
	First the listening installation is to be manned and during peacetime exercises other boats are asked if they are in the vicinity by underwater telephone.
	After lying on the bottom for a long time all bilges are to be pumped into the ballast tank intended for this.  The filling of all bunkers and ballast tanks is to be examined, and the specific weight of sea water is measured for comparison.
	238.  First the regulating tanks are pumped with the main drain pump, until the calculated moderate positive buoyancy is present.   Now pumping is halted to wait and see if the boat separates from the bottom.  Slight positive buoyancy works only very slowly.  Forward and aft movement of the crew (except for control room and motor operators) assist release from the bottom.  If necessary, continue pumping with the auxiliary drain pump, in order to achieve as gentle a release from the bottom as possible and to avoid the boat shooting up too quickly.
	Blowing with compressed air to release from the bottom must be avoided because of the rising billow of air.  However if blowing can not be avoided, then it must take place in the stern, because as a result, the boat separates more easily from the bottom than by blowing the center ballast tanks.  After the freeing the boat from the bottom the ballast tanks are to be immediately flooded again.  Blowing the ballast tanks must be carried out carefully, so that inadmissible pressures in the ballast tanks are avoided, should the flood valves lie in the mud.
	239.  During release from the bottom the boat is to remain bow down (at least 2°), so that rudders and screws are not damaged.   As soon as the boat is bow down and free forward and aft, the propellers may be engaged.

	- 63 -
	240.  Free.

	- 64 -
	Section XI
	Conduct in difficult situations
	A.  Water intake
	241.  If the boat accidentally takes on water resulting in such a large negative buoyancy that it sinks, the following must be taken into consideration before blowing the ballast tanks, ballast and fuel oil tanks, the watertight bow or watertight stern:
	a)  How many metric tons of water have entered the boat?
	b)  Which ballast tanks, ballast and reserve fuel oil tanks etc. are presumably damaged?
	c)  Will partially or completely blowing the ballast tanks or other buoyancy options give the boat enough buoyancy?
	The purpose of these considerations should be to avoid the haphazard and wasteful consumption of compressed air as much as possible.
	242.  Therefore, the Commander and the Engineering Officer have the responsibility to use the available compressed air supply with the greatest efficiency when operating the various safety equipment.  If blowing the ballast tanks is not enough, one must strive to create buoyancy by moving other weight overboard.  The order in which to try to lighten the boat and thereby to bring it to the surface is:
	a)  partially blow or completely blow ballast tanks and ballast and reserve fuel oil tanks (if necessary also fixed fuel oil tanks, watertight bow, watertight stern),
	b)  pump or express regulating tanks, trim tanks,
	c)  pump torpedo compensating tanks,
	d)  jettison the anchor,
	e)  shoot torpedoes, if possible, pump the tube after each shot.
	f)  pump fuel oil tanks and lubricating oil tanks.

	- 65 -
	243.  If a U-boat has sunk and the crew is no longer able to bring the boat by own means to the surface, prepare to escape after deploying the rescue equipment (if installed) and making the escape gear ready.
	On accidents in the homeland escape is to be delayed if the situation in the boat allows, because it may be expected that in most cases the sinking location is known and auxiliary vessels will soon arrive.  In such a case the call to escape is made by the rescuer after execution of the necessary preparatory measures.
	If rescue cannot take place from outside with certainty, escape is to be executed as soon as possible.
	244.  In the case of water entry which does not immediately lead to the sinking of the boat holding the boat by blowing ballast tanks or ballast and reserve fuel oil tanks must be attempted.  Boats in the homeland are to surface immediately.
	245.  On boats with pressure resistant compartments the spaces adjacent to refuge space can be placed under pressure.  This means that after abandonment of the compartment in which the leak is located, its buoyancy can be preserved based on knowledge of the position of the leak in the boat by blowing out the whole space if necessary.  However, blowing the space only makes sense if the leak lies far enough down.
	246.  Free.
	247.  Free.

	- 66 -
	B.  Scuttling the boat
	248.  Typically, there will not be a lot of time available for execution of the order "Scuttle the boat".  Therefore, if the Commander decides to scuttle the boat his order "Prepare to scuttle" is to be passed verbally from man to man in due time.  The order "All men out of the boat" is executed as quickly as possible.  The Commander remains on the bridge, the Engineering Officer and the Zentralemaat inside the boat until the last.
	249.  The vents are unlocked at "Prepare to scuttle", on boats with negative buoyancy tanks the flood valves of the negative buoyancy tanks are opened, ready to flood by collective vents, also, the manifold valves to the regulating tanks are opened, ready to flood by the hull valve.
	250.  The Engineering Officer remains at the speaking tube in communication with the Commander to receive the scuttling order.  Then the vents are opened according to situation of the boat.  Make sure that articulated vent levers do not revert back! (Insert key in between to control emergency flap valves)
	251.  If enough time exists to blow up he boat, set explosive cartridges at the flooding lines of the torpedo compensating tanks, to the filters of the cooling water piping (open hull valves before), at the outlet of the drainage piping, head etc. as appropriate.
	252.  Free.
	253.  Free.

	- 67 -
	C.  Countering large trim angles
	254.  Generally, large bow/stern heaviness, caused by an out of trim boat or by incorrect depth control measures, can be countered with operable diving planes (whether motorized or by manual operation) by high speed (GF or AK) and by setting diving planes "up hard" for bow heaviness and "down hard" for stern heaviness.  Additionally, with bow heaviness the rudder can be put hard over.  With very large bow/stern heaviness the lowest lying ballast tank can be blown hard for a short time for quicker correction.  Particular care must be taken to vent the forward ballast tank while still in a bow heavy condition
	255.  Countering large bow heaviness in the event of flooding.   Immediately stop and blow center and forward ballast tanks, center not fully blown.  Diving planes up hard, rudder hard over.  If heaviness decreases, blow aft ballast tank, so that boat does not fall more than 10-15° stern down.  Then if necessary blow center again completely.  If the boat becomes stern heavy, immediately go to AK to also bring the boat up dynamically.   Afterwards, if the boat is to remain submerged, and is still in the bow heavy condition order "Ready at vents" and "Open vent".
	256.  Countering stern heaviness in the event of flooding.   Immediately go to AK, blow center and aft, center not fully blown.  If heaviness decreases, also blow forward, so that boat does not become bow heavy, and if necessary open the center vent again completely.  If the boat is to remain submerged, make the boat bow heavy by opening the center and forward vents and continuing to blow aft, only vent ballast tank one in the bow heavy condition.
	257.  Free.

	- 68 -
	258.  Free.
	259.  Free.
	260.  Free.

	- 69 -
	Section XII
	Diving commands
	A.  Preliminary remarks
	261.  Verbal order transmission is the most important method in the boat.  It must work properly and safely in every conceivable situation.  The commands, orders and reports are carried out exclusively in the prescribed form.  Before forwarding they are to be repeated.
	262.  The order and reporting installation is used only by the Engineering Officer and is provided exclusively for the transmission of orders.  In case of danger and for all hands maneuvers it may be used by the helmsman for the additional announcement of the orders ("All men out of the boat", "Rudder failure", "Man overboard").
	263.  Voice tubes are used for orders and messages concerning the torpedo armament (e.g., torpedo settings), as well as reports, further inquiries to the control room to the Engineering Officer (e.g., draining, outer doors).  Start whistle is omitted when submerged.
	264.  When submerged, the order transmitting telephone is rung with only one quarter rotation.  The receiver reports with room, rank and name (e.g., "Bow room, Gefreiter [Leading Seaman] Meier"), then the caller as well (e.g., "Control room, Engineering Officer"), intermediate calls are answered with "Attention".  Passed orders, inquiries, reports etc. are always repeated by the receiver and are confirmed with verbatim or analogous repetition by the caller with "Correct".
	If the order transmission is finished, the caller says "End" and hangs up after repetition. With longer order transmissions by telephone (e.g., diving plane failure, bearing reports) the Zentralemaat after finishing instead orders: "Connection out".

	- 70 -
	Generally, voice tube usage takes place in the same manor (repetition, "Correct", "Connection out").
	265.  Key to the following compilation:
	+  = transmitted by means of Order transmitting system,
	B  = order,
	M = report,
	W = repeat or repeat and forward.
	266.  Free.
	267.  Free.
	268.  Free.

	- 71 -
	What? From? Wording Remarks   B.  Negative pressure test           269. B. C.O. Prepare to dive     W.B. W.O. Upper deck prepare to dive     +W.B. E.O. Below deck prepare to dive Verbally to all rooms   M. Posts Bow room (Officers room. . . . ) ready to dive By rooms in the direction of the control room   M. Posts Fore- (After-) ship (control room) is ready to dive (as appropriate except for the diesel) E.O. receives departmental reports only   M. E.O. Below deck ready to dive (as appropriate except for . . . . )   M. W.O. Upper deck ready to dive         270. B. C.O. To diving stations     +W.B. E.O. To diving stations Verbally to all rooms   M. Posts Foreship . . . . at diving stations E.O. receives only departmental reports   M. E.O. Below deck at diving stations         271. M. C.O. Closing conning tower hatch     M.B. C.O. Conning tower hatch off, negative pressure test     +W.B. E.O. Conning tower hatch off, negative pressure test     W. Posts Conning tower hatch off Verbally to all rooms   B. E.O. Turn on exhaust air fan     Open exhaust air head and foot valves     Open exhaust air slidegate valves     M. Posts Exhaust air fan running     Exhaust air head valve on     Exhaust air foot valve on     Exhaust air slide gate valves fore- (after-) ship (control room) on Again by rooms in the direction of the control room   B. E.O. Close exhaust air head and foot valve     M. Posts Exhaust air head- (foot-) valve off     B. E.O. Close exhaust air slide gate valves     M. Posts Exhaust air slide gate valve foreship . . . . off     B. E.O. Stop exhaust air fan     M. Posts Exhaust air fan stopped

	- 72 -
	What? From? Wording Remarks             M. E.O. Negative pressure x mb, contents established for x tons, residual buoyancy (or negative buoyancy) and trim condition 0° (if appropriate add change) Utmost quiet in the boat       272. M. Z.Maat Time is up After 2 minutes   M. E.O. Negative pressure has fallen x mb and is holding     M. C.O. Opening conning tower hatch     M. C.O. Conning tower hatch on     +W. E.O. Conning tower hatch on     W. Posts Conning tower hatch on To all rooms       273. Free.                             274. Free.                             C. Test dive 275. Boat is ready to dive, below decks at diving stations, negative pressure test completed     B. C.O. Prepare to dive (if not yet ordered) See negative pressure test   B. C.O. Open flood valves, watertight bow, water tight stern     W.B. E.O. " Can be ordered during the negative pressure test

	- 73 -
	What? From? Wording Remarks             M. Posts Flood valves on     M. Posts Watertight bow, water tight stern, on     M. E.O. Flood valves, water tight bow, water tight stern on     B. C.O. To diving stations (if not yet ordered) See negative pressure test   B. C.O. Negative pressure test (if not yet ordered) See negative pressure test       276. B. C.O. Ready at vents     W.B. E.O.             "     W. Posts Ready at vents     M. Posts 1. . . . . ready     M. Z.Maat Vents ready (once unlocking is reported)     M. E.O. Vents ready         277. B. C.O. Flood     W.B. E.O. Flood     W. Posts Flood Verbally to all rooms   B. E.O. One (Post 1 reminds if necessary)     M. Posts One . . . . on     M. E.O. Vents on     B. E.O. Express     W. Posts Express     M. Posts Air (when residual water test shows air) Only in boats with negative buoyancy tanks   M. Posts Off (when flood valve is off)     M. Posts Negative buoyancy tanks expressed         278. B C.O. Go to x meters Verbally to all rooms   W.B. E.O.          "              "   M. E.O. Depth in increments of 10 meters     M. E.O. Boat oscillated     B. C.O. Close vents

	- 74 -
	What? From? Wording Remarks             W.B. E.O.       " Verbally to all rooms   M. Posts One . . . . etc. off and locked Large boats accordingly   M. E.O. Vents off         279. Free.                             280. Free.                             D.  Crash diving 281. B. C.O. Alarm!  All repeat aloud     M. Posts Ready (Diesel and control room head valve) Lamp board   M. E.O. Ready (E.O. takes position below the hatch)      M. W.O. Off (conning tower hatch is latched)     B. C.O. Flood     B. E.O. Flood (vents are only opened by order of the E.O.) Monitor   B. E.O. One Monitor   B. C.O. (Quickly) go to x meters Verbally to all rooms   W.B. E.O.                  " Verbally to all rooms       282. B. E.O. Express     Reports of the vents and negative buoyancy tanks as for test dive

	- 75 -
	What? From? Wording Remarks       283. M. Posts Aftership ready to dive     Depth reports, oscillating, closing vents as for test dive         284. Free.                             285. Free.                             E.  Submerged cruise a) Controlling orders       286. B. C.O. Balance the boat for both motors Ahead KF at x meters 1° bow down. Or one motor or LF or x° bow down   W. E.O. "     +B. E.O. Balancing the boat Silence in the boat.       287. B. E.O. Flood x, pump x, (x in liters) or x tons Rough quantity reports run in increments of 500   M. Posts Flooding (pumping) one hundred - two hundred - 300 . . . . x flooded (pumped) Fine in increments of 100, trimming in increments of 50   B. E.O. Stop flooding (pumping, trimming) For standard orders in tons, flood roughly or pump with the main drain pump   M. Posts Repeat and report:  x (or x tons) flooded, etc.   B. E.O. Trim to forward (aft) x (x in liters)

	- 76 -
	What? From? Wording Remarks         M. Posts Trimming to aft (forward) 50 - 100 - 150 - 200 - . . . . x are trimmed to aft (forward)         288. +B. E.O. Prepare to sound     W. Posts              "     M. Posts Venting trim tanks Verbally to all rooms   M. Posts . . . . tank (. . . . bilge) ready to sound In the direction of the control room   M. Posts . . . . room is ready to sound     M. Posts Fore- (After-) ship (control room) ready to sound To E.O.   +B. E.O. Sounding! Attention! . . . . Zero!     M. Z.Maat Contents are recorded, total contents of the regulating tanks x tons, trim tank aft x (in liters)         289. M. E.O. Boat is balanced for both motors Ahead KF, at x meters, 1° bow down, contents noted         290. Free.                             b)  Depth changes       291. M. E.O. Boat steady ...., boat falls ...., boat rises, in addition according to the situation, sea state etc. depth reports in increments of 50 cm     M. E.O. Large depth changes in increments of 10 meters Verbally to all rooms   Bow room and stern room observe depth change in the depth meters and announce differences of more than 10 meters from the running deep reports or the depth to be headed for Verbally to all rooms

	- 77 -
	What? From? Wording Remarks       292. M. E.O. Request speed increase (request HF) In emergency   M. E.O. Speed increase no longer necessary (boat can be held at LF)         293. B. C.O. Quickly go to x meters Ahead GF   B. E.O. Quickly go to x meters         294. Free.                             294. Free.                             c) Periscope       296. M. C.O. Periscope extending (retracting)     B. C.O. Hydraulic fluid (insufficient pressure to drive)     M. Z.Maat Pumping hydraulic fluid (always if under 60 kgs/cm2, and on order: "Quickly go to periscope depth")     M. E.O. Periscope free     M. C.O. Through     M. E.O. x meters     M. E.O. (boat settles . . . . ) periscope cuts under Omitted on "Quickly go to 20 meters"   M. C.O. Zero     M. E.O. x meters

	- 78 -
	What? From? Wording Remarks       297. Free.           d)  Negative buoyancy tanks       298. B. E.O. Ready at negative buoyancy tanks Hands on flood valves ready to operate   B. E.O. Fill negative buoyancy tanks (also without notice) Not until open vents, then open flood valve   B. E.O. Express (Negative buoyancy tanks)     B. E.O. (Negative buoyancy tanks) Check for residual water     M. Z.Maat Both air (starboard water, port air) According to results   M. Z.Maat Request to equalize negative buoyancy tank     B. E.O. Equalize (negative buoyancy tanks) (equalize over pressure using vents)     B. E.O. Open Negative buoyancy tanks (open flood valves)         299. Free.                             300. Free.

	- 79 -
	What? From? Wording Remarks       e)  Working with men       301. Applicable only when the crew is at "Action stations"     +B. E.O. Rooms forward (aft) Without changing rooms   +B. E.O. Compartments forward (aft) (Foreship and aftership and also the control room) To the control room bulkhead   +B. E.O. All men forward (aft) As far as the bow (stern) room   +B. E.O. At Stations (never means "Dismiss from action stations")         302. Free.                             303. Free.                             f)  Rudder       304. M. H. Rudder over 15°     E.O. repeats     M. H. Rudder coming in     E.O. repeats         305. Free.                             F.  Surfacing       306. B. C.O. Prepare to surface (after all around sweep in the periscope and precise all around listening)     +B. E.O. Prepare to surface Verbally to all rooms   M. D. Diesels ready, starboard (port) drive

	- 80 -
	What? From? Wording Remarks         M. B.L.S. Bridge watch ready To E.O.   M. Z.Maat Negative buoyancy tanks equalized     M. Posts Vent 1 . . . . checked, off and secured (large boats accordingly)         307. M. E.O. Below decks ready to surface, starboard drive, positive pressure x mb (the individual measures above are included in this ready report)     B. C.O. Retract periscope, both motors Ahead GF.     B. C.O. Surface Verbally to all rooms       308. W.B. E.O. Surface Verbally to all rooms   M.B. E.O. Boat rises, opening negative buoyancy tanks     M. E.O. 14 meters, 13 meters, 12 meters, in increments of 1 meter     B. C.O. Blow     W.B. E.O. Blow (no further depth reports) Negative buoyancy tanks filling   M.B. E.O. Conning tower hatch free, equalize pressure Negative buoyancy tanks filling   M. C.O. Opening conning tower hatch (Orders for drive diesel)             M. E.O. Boat is out, pressure equalization complete     B. C.O. Stop blowing, conning tower hatch on     B.W. E.O. Stop blowing Stop filling [negative buoyancy tanks]       309. +W. E.O. Conning tower hatch on (Posts"  Head valve is off) Verbally to all rooms   B. C.O. Blow with diesel (set the bridge watch)     W.B. E.O. "     Open diesel air intake head valve and foot valve, start diesel to blow     M. Posts Diesel air intake head and foot valve are on, blowing diesel runs     M. E.O. 1 and e.g.5 blowing Filling negative buoyancy tanks completely

	- 81 -
	What? From? Wording Remarks       310. B. E.O. Start exhaust air fan, open exhaust air head and foot valves, open exhaust air slidegate valves Filling negative buoyancy tanks completely   W.M. Posts         "        and report accordingly     M. E.O. To bridge:  Request permission to pump out?     B. C.O. Pump     B. E.O. Pump bilges Z.Maat equalize weight and trim       311. M. C.O. The number and side of the blowing ballast tanks are given (by finger sign) by the bridge to the E.O. beneath the conning tower hatch     M. C.O. All have blown (circle sign)     W.B. E.O.                "            Stop blowing with diesel Sign:  clenched fist   W.M. Posts Then:  "Blowing diesel stopped"         312. B C.O. Dismissed from diving stations, boat remains ready to dive. Verbally to all rooms   +W.B. E.O. "     B. C.O. As appropriate:  Close flood valves, watertight bow, watertight stern     W.B.M. E.O. Repeats and reports accordingly         313. Free.                             314. Free.                             315. Free.

	- 82 -
	Annex
	Instructions for the performance of the pressure dock test
	1. Bring the boat to the greatest possible negative buoyancy for diving, i.e. completely fill trim tanks, regulating and fuel oil tanks, torpedo and negative buoyancy tanks, and torpedo tubes.  Open upper deck torpedo canisters, however, at the same time, the boat must be balanced.   Calculate attainable negative buoyancy on the basis of the documentation from the last dive and inform the responsible representative of the KMW.  It should not be less than 10 tons.     2. Stow any non pressure resistant supplies crammed beneath the upper deck (stowed away beer bottles etc) in the boat.     3. After entering [the ballasted down dock] the boat is set in place [on the bottom of the dock] by lifting the dock [de-ballasting the dock] and bringing the water level [inside the still open dock] to approximately 3.8 meters draught.  Thereupon the flood valves are opened after completion of an under pressure test (boat ready to submerge) and the ballast tanks are flooded by opening the vents.  Flood valves and vents remain open during the pressure test.  Traffic only through the conning tower hatch.     4. The telephone connection is established by the dock staff.  Satisfactory communications are ensured by testing.     5. In the event that the telephone connection is interrupted during the test it continues.  Communications are maintained by underwater telephone signals which are answered by the dock staff by tapping against the pressure dock hull.

Note:  The German Navy built a new pressure dock in 1967.  Dock "C" Displacement: 13,106 tons, Length: 93.0 meters, Beam: 26.50 meters Draft : 3.60 meters.  Dock "C" was retired in 2011 because it was not large enough to accommodate the new type 212A submarines.  Click to view a photograph Dock "C"