Fig. IX - 36" Air Valve
K-49, K-54 & Future
-34-
(e) Take-Off
Yv'hen the ship is in the hangar it is norl!lally J..cept
under proper pressure by means of a ground blower. As
the ship is taken out of the hangar, v;ea ther condi tion3
may be such as to cause a change of the temperature of the
gas.
If the temperature is increased, air will be released
automatically by the air valves. If the temperature is de-
creased, air may have to be blo~~ into the system to keep
up the pressure. This may be done by ope ning the scoops and
the air dampers, and speeding up the engines or it may be
done by means of the auxiliary blower.
NOTE: The dampers can be kept continuously open while
air is blown occasionally in the system by man
euvering the throttles, the check valves pre
venting loss of air when the engines are idle.
Under normal conditions, however, it is best to
keep the dampers closed when not pumping air.
(f) Climb
As soon as the ship begins to rise, the problem is no
longer one of feeding air to the system, but one of releas-
ing air to maintain a constant differential pressure between
the gas in the envelope an.d the decreasing atmospheric pressure.
This is done autom a tically as outlined above, by the <>-ir
valves. The air valves and ducts can prevent the pressure
from rising above 2.5 inche s of water when the ship is rising
a t a speed of 2400 ft. per minute.
-35-
During the climb both dampers should be closed. The
scoops, however, should remain open so that the pilot may
be able to blow air into the ballonets by opening the
dampers, should he decide to come do~m again .
CAUTION: 2400 ft •. per.minute is the maximum permissible
rate of climb. The actual rate of climb should
be kept wel l below this vaiue.
(g) Level Flight
In level flight it is common pr2.ctice to keep the for
ward damper and the scoops open so as to produce an air
pressure slightly higher than the setting of the valves,
causing a circulation of air through the air damper and
the air valve.
CAUTION: The air release valves should not be opened
manually when the ship is flying near or above
pressure height.
A warning to this effect is mounted on the pilot's
instrument panel. As long as the valves are opere>.ted auto-
rna tically, with the scoops and air damper opened, pre ::;sure
in the system does not drop below the setting of the valves
although the ballonets may become completely deflated. If
the air valves were opened manually at this 'point, the small
amount of air in the system would become quickly exhe.usted,
the pressure dropping to atmospheric pre2sure. The 3ir line
pa tches or the air line frame may be dama.ged by the full
unbalanced gas pressure.
-36-
(h) Descending
When the ship is descending, air must be fed into the
system to maintain the differential pressure between the
inside of the envelope and the increasing atmospheric
pressure. The scoops should be opened wide enough to per
mit adequate air flow. The air scoops, ducts, and damper
valves can admit air into the ballon ets at a sufficient rate
to maintain a gas pressure of 1.25 inches of water when the
shi p is descending at a rate of 1200 feet per minute, at a
forward speed of 50 knots.
The air intake capacity naturally decreases as the
forward speed is reduced so that the maximum permissible
rate of descent is less than 1200 feet per minute when the
forward speed is less than 5.0 lrnots.
CAUTION: 1200 feet per minute is the maximum permissible
rate of descent. The actual rate of descent
should be kept well below this value.
(i) Landing
At the time of landing it _usually becomes necessary
to throttle down the motors and the air scoop system can no
longer supply the required pressure to the ballonets. An
auxiliary blower is provided for such conditions.
The blower is of sufficient capacity to maintain a
gas pressure of 0.5 inches of water at the gas manometer
-37-
when the ship is descending without power at the rate of
250 ft. per minute. This pressure, while inadequate for
normal flight, is sufficient to permit satisfactory hand
ling of the ship during landing operations.
Instructions for starting the blower for airships
K-3 thru K-98 are given on p~_ ge 44.
(j) Shifting Air
During flight, it may bec.ome necessary to adjust the
relative inflation of the two ballonets ·in order to change
the trim of the ship. This is done by operating the air
valves and dampers manually.
In trimming the ship in this manner, it may be well to
consider air as ordinary ballast, the effect of transferring
air being the same as that of transferring any ballast.
(k) Blowing Air Into The Gas
In emergency cases where a large amount of gas has been
lost, such as when the ship is descending after having over
shot its pressure height, and the ballonets, even when fully
inflated, cannot keep up the . pressure of the envelope, it
may become necessary to blow air into the gas.
This may be done by untying the sleeve connecting the
air chamber to the envelope. This sleeve is located above
-38-
the cabin ceiling, starboard, and makes a nyn connection
with the helium inflation sleeve. Only the amount of air
necessary to bring the pressure to th~ required value
should be used.
(3) Gas Release System (See BuAer Manual 12-304 12-307).
The gas release system includes two 20-inch gas
valves, located on the port and starboard sides of the
envelope at panel 34, and gores K and .L. It includes, also,
two rip panels located on the top of the ship from panel 21
to 28, and from panel 53 to 59.
(a) Gas Valves
The gas valves are set to operate automatically when
the gas pressure reaches 2-1/2-inches of water as read
on the gas manometer. They can also be operated manually
from the pilot's instrument panel. The gas valves are
equipped with micro switches which operate telltale lights
on the pilot's panel when the gas valve begins to open at
2-1/2-inches of water. In order to offset localized drop
of pressure in the air stream and to prevent premature
opening of the valves, a semi-circular windshield is attached
to the envelope on the aft side of the . valve.
CAUTION: Do not attempt to hold gas valves closed
manually when . flying above - pr.essure height
as _excessive pressure maY deYelop in the
envelope.
-39-
Fig. X
Helium Inflation Sleeve
-40-
(b) Rip Panels
The rope which opens the forward rip panel can be
reached from · the forward door; the rope which opens the
aft panel can be reached from the aft door. They are
dyed red to avoid confusion with the other ropes.
(4) Controls and Auxiliaries
(a) Valve Controls
The air and gas release valves can be operated man~
ually from the pilot's instrument panel, Fig. XI. Every
valve has an opening arid a closing control. Pulling the
opening control lifts the valve off its seat and releases
air or gas as the case may be. The valves should close by
themselves when the opening control is released.
A closing control is provided, however, to force the
valves closed in case they should stick. The control is
also used to make certain that the gas valves are closed,
and that no gas is being lost when flying near pressure
height.
The following check procedure of the valves is
recommended:
1. Before take-of .f, crack all valves 6pen for a
short instant to make ce~tain that the valves
and telltale lights operate satisfactorily.
2. When flying close to pressure height, pull
closing control of gas valves fro m t ime to time.
-41-
A - Safety Switch
B- Mechanic's Signal
C - Forwar~ Air Damper
D - Forward Air Valve, Open
E - Aft Air Valve, Open
F - Aft Air Damper, Close
G - "Forward Air Valve, Close
R - Aft Air Valve, Close
I, J, K, L- Fuel Dumping
M - Port Helium Valve, Close
N - .Port Helium Valve, Open
0 - Stlbd Helium Valve, Close
P- St'bd.Helium Valve, Open
Q, R - Slip Tanks
~ (!)Q)®@ ®@
·Fig. XI - Flight and Instrument Panel
-42-
(b) Damper Control
The air dampers can be kept open by means of an
olive on the control cables. The dampers are normally
held closed by springs which prevent the dampers from
opening under the pressure of air from the scoops.
(c) Manometers
The air pressure in the two ballonets and the gas
pressure in the envelope are read on three manometers,
located on the flight panel. Each manometer is equipped
with a three-position valve ·.
When this valve is turned on the position marked
"Check" the manometers should read zero. If necessary,
the reading can be brought back to zero by means of an
adjusting dial. This check should be made before every
take-off.
v7hile in flight the valve should be turned on the
position marked "static."
A mechanical manometer on the instrument panel reads
the gas pressure and is used as a check .on tl).e liquid
manometer.
-43-
Fig. XII
Starting Auxiliary Blower
(K-.3 thru K-98)
(d) Starting Auxiliary Blower (K-.3 thru K-98)
1. Turn on switch on pilot's instrument panel.
2. Open fuel line shut-off cock on gasoline
filter bowl as-sembly. (Turn counter-clockwise) •
.3. Close carburetor choke (choke is open when
lever is against stop pin). Open throttle
by pulling black button on throttle wire.
4. Wind starting rope on pulley, brace one hand
on fuel tank and pull rope hard, giving quick
spin to engine. Repeat, if necessary, until
engine starts. Then immediately open choke
partially easing to full position as engine
warms up. If engine is warm from previous
running, it is not necessary to use choke for
starting.
5. Open air intake door.
-44-
(e) Stonping Blower
1. Turn off button on pilot's p~nel.
NOTE: Engine can also be stopped by pressing
red stop button, mounted on me.gneto
stator plate until engine stops.
2. Vfuen the airship is in flight with the Homelite
Model HRU-28 auxiliary blower stopped, a
parti al vacuum is set up in the exh aust. This
partial vacuum draws fuel into the crankcase.
In many instances, this has resulted in bursting
the crankcase or cylinders and pistons when
the pl~nt was started. To prevent this, the
fuel line shut-off valve must be ti ghtly closed
whenever the plant is stopped, whether in flight
or at the airship base.
(f) LaDel Electric Blower
The production schedule calls for a LaDel electric
blower to replace the gasoline powered blower, described
above, on airships K-99 and future. The only source of
power for this blower is the Lawrance auxili ary generator.
The auxili a ry generator must be running at rated speed
before the electric blower may be used.
(5) Summary: Pressure Control System
(a) Settings
1. Forward Air Valve: Begins to open at 1.50 inches
of water of air pressure in the for ward ballonet
as read on car manometer.
2. Aft Air Valve: Begins to open at 2.00 inches of
water of air pressure in the aft ballonet a s
read on car manometer.
3. Gas Valve: Begins to open at 2-1/2-inches of
water as r ead on gas manometer.
(b) Control, Instruments & Auxiliaries Chart
See Fig. XIII
(c) Operation Chart
See Fig. XIV
-45-
INST,RUMENTS,
CONTROLS
AUXILIARIES
Air Scoop
Adjustment
Air Damper
Contols
Air Valve
Controls
Manometers (3)
Pressure Gage
Auxiliary
Blower
Switch for
Auxiliary
Blower
Gas Valve
Controls
Air Sleeve
Rip Cords
LOCATION
Port & Starboard
of Frame 6.
Pilot's Instrument
Panel Fig. XI
Pilot's Instrument
Panel Fig. XI
Pilot's Flight
Panel Fig. XI
Pilot's Instrument
Panel Fig. XI
Cabin Deck, Frame
5, Fig. XII
Pilot's Instrument
Board Fig. XI /l~so
switch on engine
Pilot's Instrument
Panel Fig. XI
Ceiling Frame 6.
Outside of Forward
and Aft Doors
Fig. XIII
PURPOSE
To control air pressure in
air chambers and ballonets.
To direct air to the for
ward or aft ballonet
To release air from the for
ward or aft ballonets and
to close valve.
To indicate pressure of the
gas in envelope and of the
air in the two ballonets
To check liquid gas pressure
manometer
To supply air pressure to
ballonets when regular sys
tem becomes inadequate
To shut off motor.
To release gas manually and
to close valve.
To blow air into gas in
emergency
To deflate ship rapidly in
emergency
Controls, Instruments and Auxiliaries Chart
-46-
OPERATION
Take:.:.orf
Climbing
Flying
near
pressure
height
Level
Flight
Normal
Descend
ing
Landing
Shifting
Air .
Blowing
air into
gas
CONDITION NORMAL SETTING REWLARE:S
Air in both Both dampers Keep up ship inflation
ballonets closed if necessary by opening
dampers and by occasion-
al .blasts of propellers
or by auxiliary blower
Air being re- Both dampers Watch for excessive gas
leased from closed pressure. Stay below
Fwd.Ballonet climbing rate of 1200 ft.
per minute.
Ballonets are Open both Maintain full operating
fully deflat- dampers and pressure tn air system.
ed.Gas valves scoops. Do not operate air valves
operate auto- manually. Check closing
matically to control of gas valves to
release gas if make sure no gas is being
pressure height lost. Watch the tell-tale
is exceeded.
Ship in trim.
Air in both
ballonets.
Air being nor
mally replaced
in forward
ballonet
Motors are
throttled
down. Pressure
from regular
system is
inadequate
Excessive
loss of gas
Open forward
damper and re-
gula te scoops
to produce de-
sired p.ressure
Open forward
damper
Start blower
motor,open
intake door,
open both
dampers.
use dampers &
air valves
as needed.
lights.
Consider air as regular
ballast in determining
effect of shift on trim.
Watch for too low pressure.
Stay below descending rate
of 600 ft. per minute.
See Page 44 for instructions
to start blower motor~
Consider air as regular
ballast in determining
effect of shift on trim.
Untie sleeve Blow only the minimum amount
which connects air necessary to maintain
air to gas. pressure.
Fig. XIV
Operation Chart - Pressure Control System
-47
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-48-