(6) USEFUL LOAD
~ Crew (10 Men at 175 lbs. each) • • • • • • • • • • • • • • • • 1750.0 Lbs.
Fuel -
Main Engines &: Aux. Engines • • • • • • • • • • • • • • • 3930.0 Lbs .•
Overhead Tanks 475 Gal.@ 6#/Gal. 2850.0 Lbs.
Slip Tanks, 180 Gal. •••••••••• 1080.0
Oil -
Main Engines - 52 Gal. @ 7.5# Gal.
Aux. Power Plant, 3 Gal. @ 7.5#
• • • • • • •
• • • • • • • • •
Droppable Fuel Tanks (2) . . . . . . . . . . . . . . . . ~ . . ...
Baggage
Cargo
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Armament . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1. 50 Cal. M.G. . . . . . . . . . . . . . 105.0 Lbs.
2. M.G. Ammunition . . . . . . . . . . 132.0
3. Bomb Racks
. . . . . . . . . . . 41.6
4· Bomb Racks . . . . . . . . . . . 41.6
5. Bombs M-17 • • • • • • • • • • • 650.0
6. Bombs M-17 . . . . . . . . . . . 650.0
Equipment . . . . ~ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Navigation Gear
a. Charts, Publications ••••••
b. Optical Drift Sight •••••••
c. Wiley Drift Sight •••••••••
d. Parallel Rulers, Binoculars,
Stop Watch, Dividers ······• e. Miscellaneous Gear •••••••••
Total
Photographic •••••••••••••••••
Pyrotechnics -
a. Signal Pistol •••••••••••••
b. 24 Rounds Signal Flares ••••
c. 24 Float Lights •••••••••••
d. 24 Bronze Powder Markers . · ·
Total
-18-
7.5 Lbs.
13.5
1.5
14.0
18~5
55.0 Lbs.
55.0 Lbs.
2.1 Lbs.
7.2
52.8
48.0
110.1 Lbs.
390.0 Lbs •
22.5
42.1 Lbs.
00.0 Lbs.
00.0 Lbs.
1620.0 Lbs.
570.3 Lbs.
USEFUL LOAD
Emergency Life Saving Equipment:
a. Ten Life Jackets@ 3# •••••••••• 30.0 Lbs.
b. Life Raft •.•••••••••••••••••••• 66.0
Total ••••••••• 96.0 Lbs.
Food and Water:
a. Food, Canned . . . . . . . . . . . . . . . . . . .
b. Food, Fresh . . . . . . . . . . . . . . . . . . . .
c. Water, Fresh . . . . . . . . . . . . . . . . . . .
d. Rescue, Rations . . . . . . . . . . . . . . . .
e. Emergency, Food and Water . . . . . .
Total
Miscellaneous Equipment:
a. Classified Container •••••••••••
b. Emergency Cable ••••••••••••••••
c. Two Flashlights@ 3/4 Lbs. • ••••
d. Signal Flags •••••••••••••••••••
e. Fuel Pick-up, Green Marker Buoys,
Grapnel ....•.•...•.•.......••....
f. One (1) Chute, One (1) Harness ••
g.. P. & W. Engine Kit •••••••••••••
h. Wire Cutter and Knife ••••••••••
i. Rigger's Kit •••••••••••••••••••
30.0 Lbs.
55.0
35.0
16.0
27.0
163.0 Lbs.
2.2 Lbs.
5.0
1.5
1.0
28.0
18.0
15.0
5.0
lh2.
Total 91.2 Lbs.
TOTAL USEFUL LOAD 8325.1 Lbs.
-19-
It is recommended that the total car load be not
allowed to exceed 18,300 lbs., or 2300 lbs. over the design
Under such condition of 2300 lbs. "Design Heaviness"
the factors of safety are reduced to about 2.6 for the car
structure and about 3.5 for the car suspension.
NOTE: "Design heaviness" is the excess of car load over
design load -a.nd should not be confuseq. with "flight
heaviness" which is the excess of gross load over
gross lift.
"Flight heaviness" alone is no measure of the factors
of safety of the car structure and suspension.
Under condi tiofls of high lift there may be no
"flight heaviness" but a high "design heaviness."
Under conditions of low lift there may be no
"design heaviness" but a high "flight heaviness."
Preceeding pages show computations of a typical car
load. It is suggested that similar forms be used for actual
computations before take-off.
-21-
B. ENVELOPE PRESSURE CONTROL SYSTEM
(1) General Description
The maintenance of a predetermined pressure differ
ential between the gas in the envelope of a non-rigid air
ship and the surrounding atmosphere is the first basic
requirement to the successful operation of this type of
airship.
The functioning of the envelope in assuming the various
flight stresses, the proper suspension of the car, the effic
ient operation of the controls, all depend upon a closely
held pressure differential.
It is the function of the pressure control system to
maintain this pressure differential within a certain range
and to do this with a minimum loss of lifting gas. This
result is accomplished by inflating the envelope partly with
gas and partly with air, the air being contained in a forward
and an aft ballonet, and by regulating the inflation of the
air by means of an air system,without changes to the amount
of gas in the envelope. Under extreme conditions, outside
of the range of the air system, gas can be released auto
matically by meatls of two gas valves to prevent the internal
pressure of the envelope from rising above a safe value.
The pressure control system is also used to adjust the
trim of the ship by regulating the relative inflation of
the two ballonets.
-22-
(2) Air System
The air system comprises a forward and an aft
ballonet, a system of scoops, ducts, valves and air chambers.
Air is taken in at scoops located in the port and starboard
motor outriggers and is led through a check valve of the
butterfly type into an air chamber. From this chamber, two
air ducts lead, one to the forward and the other to the aft
ballonet, through ma~ually controlled dampers. An automatic
valve is connected to each ballonet system and is set to
release air automatically when the pressure reaches a pre
determined value. In airships K-3 thru K-98, a blower with
a gasoline power plant is provided in the cabin to supply
pressure to the air system when the pressure from the regular
system becomes inadequate. In airships K-99 and future, an
electric blower is provided. The construction of the system
is described in full detail in the "Descriptive Specifications
Manual." The operation of the system is considered further
below:
(a) Scoops
As mentioned above, air is collected by scoops located
in the port and the starboard outrigger and is led to an air
chamber through check valves. This air chamber can be con
nected to either or both ballonets by means of two manually
controlled dampers. The air pressure in the ballonets can
be adjusted within certain limits, as described further on,
by regulating the opening of the scoops.
-23-
......
AIR INTAKE AIR DISCHARGE
Flg. -v
AIR PRESSURE SYSTEM
K-3 thru K-'98
Fig. VI Air Scoops
(b) Valve Settings (See Buaer Manual 12-304)
The pressure in the forward and aft ballonets is limit
ed by the forward and aft automatic air release valves. These
two valves are set to operate at different pressures for
reasons that will become apparent further on.
The valve of the forward ballonet is set to start open
ing when the air pressure in the forward ballonet, as read
at the car manometer, reaches 1.50 inches of water. The
valve of the aft ballonet is set to begin to open at an air
pressure of 2.00 inches of water.
When the ballonets are partly infl a ted there is a
difference of pressure bet •Neen the air in the ballonets and
the gas in the envelope. This difference depends upon the
-25-
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,1 : l ; i ' l ! :_j_ i l . I :
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I ~ --- r : ~ . 1 , 1 • l-~-1---;·--r--:- : ~ ·-;--·----·r·--. __ --__ ---1
_-_-_-_-_-_-~-~---· -_-.:..--_ .. _-.... -;
----- ____ ! _____ -----T-~---r~-l-~ :~~--- c-. --l~-i.~] ___ ;=1~- :~ j __ -=-- ~-- -~ +----- ~ _ -·---"
L----- ....... J __ Q___ . I i ! I . ; i
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, ---1 0 - - 20 30 ·-~· 40 --·-- 50 · 60 -- 70 --BG -~- 90 --·1 00 - ,-----~-,--- ,
----______ :_ . _____ ; --~-_j_-~ __ j__ ________ L --~--- _; ___ · __ l ____ i_~ __ t _____ : _j ____ ~ __ . __ : --~-----; --~-~-~
j ! l ~
- - -L--·---·--- ___ l - - ~- FULLNES S , OF BALLO NETS ---~----'·---;~-- '·
I I • t
; l l . ; ' . +-·---· ------·----------------· _f____ ----~""---.. -~---'------------ ---- --·------~
Fig. VII ·-- ------~·----~-----"': ______ ... ___ __.. ..... -- . ---- ------ -
AIR PRESSURE IN EXCESS OF GAS PRESSURE
vs --% FULLNESS OF BALLONETS AT ZERO- PITCH ANGLE
AT STANDARD UNIT LIFT CONDITIONS
-26-
height of the upper part of the fabric of the ballonets
or upon the degree of their inflations, upon the lift co
efficient of the gas, and upon the f~bric weight which
reacts on the air.
Curve in Fig. VII shows the relation between this
difference in pressure and the inflation of the ballonets
at standard lift coefficient. It will be noted the.t the
difference of pressure is about 0.50 inches at full infla
tion and nea~ly zero when the ballonets are fully deflated.
Since the automatic air valves are operated by the
air pressur~ in the ballonets and not by the gas pressure,
it will be obvious that the system will tend to regulate
for a higher gas pressure when the ballonets are empty than
when they are inflated.
(c) Pressure Regulation
Under normal flight condition a gas pressure of about
1.5 inches of water should be maintained with a maximum vari-
ation of 1.25 to 2.00 inches.
CAUTION: Under no condition should the pressure be allowed
to go lower than 0.5 inch or higher than 3.0 inches
of water, the lower pressure being permissible only
in landing operations or in the hangar when there
is little or no forward speed.
It is particularly essential to maintain an adequate
internal pressure when the ship is operated at high speed
or when moored at the mast during high winds.
-27-
The K-airships are designed for a maximum speed of
65 knots with an internal gas pressure of 1.5 inches of
water.
Since the automatic air valves, as .pointed out above,
are operated by the air pressure of the ballonets, the
corresponding gas pressure at which they open depends on the
gas inflation of the ship. If, for instance, the ship is
85% gas inflated and the ballonets are more than half infle .ted,
it can be seen, by referring to the curve in Fig. VII that
the gas pressure in the envelope is about 0.32 inches of
water less than the air pressure in the ballonets. The air
valve of the forward ballonet will open, therefore, at air
pressure of 1.5 inches of water, while the corresponding gas
pressure is .32 inches of water less than the setting of th~
gas valve or 1.18 inches.
It will still be possible, however, to maintain the
recommended operating gas pressure of 1.5 inches of water
by opening the forward air damper and regulating the scoop
opening so as to produce air circulation through the air
damper and the partially opened air valve.
CAUTION: The matter of the proper regulation of the air
scoops is of the utmost importance. If the
scoops are opened too wide, excessive pressure
may be built up in the envelope causing loss of
gas. If the scoops are not opened enough, the
gas pressure may drop to a dangerously low value
resulting in buckling of the envelope.
-28-
With the differential valve setting outlined above,
it is apparent that as long as the ship is operated below
the pres sure height of the forward ballonet, air is re
leased only from this ballonet when the altitude of the
ship is increased. Hence, if upon descending, the pilot
operates only the forward damper, the air which has been
valved out during the ascent will be replaced to the for
ward ballonet, thus restoring the trim of the ship to the
same condition that exi s ted at take-off.
During short flights, the oper a tion of the system is
automatic, and no manual adjustment needs to be made except
to open the forward damper. During long flights, occasional
manual adjustments of the air balance may be necessary, but
the system remains largely self-operating.
(d) Air Valve Adjustment
All valves are adjusted to their specified settings
and t ested before being inst alled in the airship and re
tes ted after installation.
The valve settings should not be changed unless diffi
culties arise. Adjustments should then be made only by a
qualified person. During emergency, it may be necessary to
adjust the valve in flight. Instructions below should
clarify any difficulties that may be encountered.
-29-
Two 36~inch diameter air valves, see Fig. VIII and
IX, are provided in the air line in the top of the car
structure for valving air from the ballonets. One of the
valves is located between Fre~es 4 and 5, and valves air
from the aft ballonet, the air going out through louvers
on the port side of the car. The other valve, located
between frames 6 and 7, valves air from the forward ballonet
and exhausts air on the starboard side of the car. Control
lines for opening and closing the valves extend to Pilot's
Instrument panel, see Fig. XI, Page 42.
The air valves are set to open as follows:
Aft Valve -
Forward Valve - 1.5" H20
To adjust valves on K-3 thru K-53, exclusive of K-49:
(1) Inside knob adjustments (Three)
(c)
(d)
(e)
(f)
(g)
Break seal on each valve adjustment knob.
Apply same number of turns to each knob.
Never adjust one or two knobs, but adjust
them all equally, to prevent warping and
improper seating.
One complete turn of each of the inside
adjustments will effect a change in the
opening point of .018 inch H20.
Do all loosening and some tightening on
the inside.
Turn adjustments clockwise to tighten or
increase opening pressure.
Turn adjustments counter-clockwise to loosen
or decreas -e opening pressure.
Re-seal valve adjustments to prevent valve
frbm losing its settin~.
-30-
Fig. VIII - 36" Air Valve
·K-3 thru K-53, Excl. of K-49
-31-
(2) Outside Gear Adjustments
(d)
(e)
(f)
(g)
Remove gear cover.
Remove cotter pin (through gear).
Do most tightening on outside gear and no
loosening.
When tightened until 2-7/8" of screw pro
trudes from the gear, the forward or aft
air valve opening point will increase 7/16"
H20. This is a maximum condition.
Turn counter-clockwise to tighten or increase
opening point.
Turn clockwise to loosen or decrease opening
point.
Replace cotter pin and gear cover.
In the event the valves are completely out of adjust
ment, then proceed as follows:
1. Set outside gear adjustment to neutral setting.
NOTE: Neutral setting is defined as 1-1/2"
of screw protrusion from gear. Total
length of screw is 3 inches.
2. Build up air pressure to 1.5" H20 at the manometer
in the car and adjust inside knobs as previously described.
3. The valve is considered in adjustment when the
dome begins to float freely and emits a characteristic hum.
4· Re-seal all adjust ment knobs and replace outside
adjusting gear cover, together with the cotter ~in.
Insofar as the aft valve is concerned, build up
air pressure to 2 inches and repeat the above procedure.
To ad.iust valves on K-49. K-54 and later airships:
Open the zippers for the access openings in the ceiling
of the car and remove the lock seal attached to each knob.
Unscrew the l/2tr O.D. sealing caps and turn adjusting knobs.
-32-
Give each of the knobs an egual number of turns and
in the same direction. Turning the knobs clockwise, or to
the right, inc~eases the pressure necessary to operate the
valve. Turning the knobs counter-clockwise, or to the left,
lowers the pressure necessary to operate the valve. Tests
conducted on a number of modified valves in a valve test
chamber determined that ten complete turns on each of the
three knobs changes the pressure setting necessary to oper
ate the valve by 1/5 of an inch of H20.
After a satisfactory resetting is found, add. leather
washers and screw the sealing caps in place again, then
safety the knobs to the clips on the shield. Test setting
against the air manometers. The use of the gas manometer
is misleading, except at, or very near, pressure height.
-33--