\.oJ
B • . AVERAGE PERFORMANCE *
)
K-3 thru K-8 K-9 thru K-13
Speed Knots •••••••••••• 40 50.0 62.5 50 50 67 .• 5
R.P.M. . . . . . . . . . . . . . . . . 1450 1780 2200 1120 1340 1775
Fuel Consumption
Lbs./Hour ••••••••••••• 120 160** 520 98 160** 375
Endurance, Hourf>
Based on 6000 Lbs.Fuel 50 37.5 11.5
" " 5200 Lbs.Fuel - - - 53.2 32.5 14
"
II 5650 Lbs.Fuel - - - - - -
Range, Nautical Miles ••. 2000 1875 690 2130 1625 945
* See Pages 65, 66 and 67 for more complete performance data.
**Based on lean carburetor setting.
RECOMMENDED TOP SPEED - 67.5 KNOTS PER HOUR.
K-14 &: Future
40 50 67.5
],.050 1290 1740
102 165** 400
55.0 34.2 14.1
2200 1710 950
filtJHT AN!JliJtJHT CfJJYTROL
s··;:,;;~~ .
. · . ..• . :_ ~ .. :~)~
-=======II. FLIGHT& . FLIGHT CONTROL========
A. FLIGHT CHARACTERISTICS
The lift of an airship is made up of two components -
the static lift and the dynamic lift. These two components
have different physical origins and require separate treat
ment.
(1) Static Lift
The static lift is that component of lift which is due
to buoyancy and which iS independent of any motion of the
ship with respect to the air.
The gross static lift of an airship is the difference
between the weight of the air displaced and the weight of
the lifting gas.
The net lift is the difference between the gross lift
and the gross weight of the ship.
The ship is said to be "light" when the gross lift ex
ceeds the gross weight. The ship is said to be "heavyn when
the gross weight exceeds the gross lift.
In calculating the gross lift of an airship both the
gas volume and the lift coefficient of the helium, or lift
per 1000 cubic feet, must be knovm.
The lift coefficient c.an be computed, as indicated be
low, when various conditions of the atmosphere and of the
helium are known.
The gas volume, however, can be determined accurately
only when the ship is fully inflated. Calculations of gross
lift are largely limi t ·ed, therefore to full inflation.
-4-
Ordinarily an airship takes off less than fully in
flated and the lift condition is determined by a wei gh-off
rather than by calculation. After take-off, the pilot is
interested in keeping track of the variations in gross and
n~t lift as affected by the burning of fuel or dropping of
ballast on the one hand, and by the variations in atmos-
pheric conditions on the other. The changes of lift can be
followed by means of simple rules of thumb discussed later on.
(a) Calculating Full Inflation Lift
References: (1) War Department Technical Manual
TM-135
(2) Goodyear Aircraft Report on 100%
Weigh Off of K-4 Airship, Oct.l5,
1941, Revised Nov. 6, 1943.
The lift coefficient, or lift per 1000 cubic feet can
be computed from the following formula:
L = CP
Where: L
Ta
1325 - 16.7 Ra Ea
Ta
185 - 21.5 Rg Eg
Tg
(1)
=Lift Coefficient in lbs. per 1000 Cu.Ft.
= Gas Purity, %
= Atmospheric Pressure, in. of HG.
= Absolute Air Temperature, oF.= 459.8 Plus Air Temp.
Tg - Absolute Gas Temperature, oF.= 459.8 Plus Gas Temp .. -
Ra - Relative Humidity of Air, % -
Rg - Relative Humidity of Gas, % -
Ea = Vapor Pressure at Temperature, Ta
Eg - Vapor Pressure at Temperature, Tg
-5-
EFFECT °C. SUPERHEAT
ON LIFT
°C. LBS.
15 ..,__
f--
1--
1--
1--10 1000
~
1--5 500
-
0 0
C.-F. --- = - :::::: - = - = - = - = -
=
:::::: = - = -
- ::::::::: 1-- ~
-r- = r- = =
1--
= ~ :::::::::
=
I= = r- = r- = = f-
=
-;::::: = = -,..__ =
f- = 1-- =
= - = - = - = - :::::::::
lO
0 - = - -20
FARENHEIT CENTIGRADE
SCALE
For K-Airship
Fig. I
Superhea.t Chart
-6-
EFFECT °F. SUPERHEAT
ON LIFT
LBS. oF.
15'00 30
1000 20
500 10
0 0
If the effect of humidity is neglected, the formula
oecomes:
L = CP 1325 - 185 (2)
Ta Tg
If Tg = Ta and there is no superheat, then:
L = 1140 CP (3)
Ta
Formula (3) may be accurate enough for rough computa-
tions. But even when more accurate results . are desired, it
may be found convenient to use this formula and to apply
quick corrections for humidity and superheat according to
the following rules:
l. For each 5° of positive superheat, increase
lift by 1%.
2. For each 5° of
by 1%.
negative superheat, reduce lift
3. Correct for humidity in accor dance with the
following table:
LOSS IN LIFT CAUSED BY HUMIDITY
Air Temperature Loss in Lift at Saturation
0°F
20oF
32°F
50°F
70°F
90°F
l00°F
For less than
satu:ration by
l/20 of 1%
l/10 of 1%
l/5 o"f 1%
l/2 of 1%
1% less than dry air
1.8% less than dry air
2.5% less than dry air
100% humidity, multiply loss
%humidity.
-7-
in lift at
FIG. 21
~--·-·--- --
' _, I • ~ +
I I - l - ----l-1
r]-.30:-2 ~
t • ·r f ' !
Fig. II - Helium Purity -8-
The curves in Fig. II make it possible to find directly
the lift coefficient given by formula (3). This lift co
efficient should be corrected for humidity and superheat as
outlined above.
(b) Lift Vari2tions
The table below gives a number of rules which permit
keeping track of lift variations after take-off.
EFFECT ~ oF VARIOUS ATMOSPHERIC
CONDITIONS ON GROSS LIFT
CONDITION EFFECT ON GROSS LIFT
Increased Altitude,
Decreased Barometric
Pressure
Decreased Altitude,
Increased Barometric
Pressure.
Decreased Ambient
Temperature, No
Superheat
Increased Ambient
TempePa ture, No
Superheat.
Pqsitive Superheat
Negative Superheat
Below
Pressure Height
NONE
NONE
NONE
NONE
Increased by 1% for
every 5° F. *
Decreased by 1% for
every 5° F. *
Above
Pressure Height
Reduced by 1% for
every 360 ft.or
• 3 in. Hg. *
NONE **
NONE **
Reduced by 1% for
every 5o F. *
Increased by a neg
ligible amount.
Decreased b~ 1%
for every 5 F. **
* For the K-ship, 1% of gross lift amounts to about 250 lbs.
Superheat can be seen, therefore, to affect lift by about
50 lbs. for every 1°F., or 90 lbs. for every 1°C.
** Gas contracts and ship is no longer at pressure height.
-9-
NOTE: The student pilot is sometimes confused by the
apparent contradiction between some of the above
rules, which seem to imply that lift is unaffected
by temperature, and the known fact that an airship
has a greater lift in winter than in summer.
The contradiction is easily cleared when it is
considered that the rules in the above table apply
only to the lift of an airship to which no helium
is added.
It is true, as indicated by the above rules, that
the lift of an airship inflated during the summer
remains the same when cold weather sets in, pro
vided no gas is added and no gas is lost and neglect
ing the .effect of humidity. The gas and the dis
placed air contract in the same proportion so that a
like weight of gas has th.e same lift in winter as in
summer.
At the same time, because of the gas contraction, it
is possible to add a certain amount of gas in winter
to a ship which had been fully inflated in the sum
mer. A fully inflated ship has, therefore, a greater
lift in winter than in summer.
(2) Static Trim
An airship trims at an angle such as to bring the
center of gravity directly below the center of buoyancy. The
K-airships trim at an angle of 3.5°,plus or Ia.inus 1/2°, nose
down at static equilibrium, when .fully inflated, with con
ditions such as to produce a static lift of 62 lbs. per 1000
cubic feet and with a load distribution as indicated on the
following page.
Under the above conditions, the location of the center
of buoyancy and of some of the important centers of gravity
along the longitudinal axis are given below:
-10-
Center of Buoyancy:
Center of Gravity of
Ship as a whole:
Center of Gravity of
Loaded Car.
Center of Gravity of
Envelope:
20.53 ft. Aft of Frame 9.
1.75 ft. Forward of Center of
Buoyancy.
8.45 ft. Forward of Center of
Buoyancy.
10.00 ft. Aft of Center of
Buoyancy.
The useful load is ordinarily distributed approximate
ly about the center of gravity of the car so that changes
in the useful load do not alter greatly the location of the
center of gravity of the car.
The center of gravity of the ship as a whole, however,
changes with the total car load since, as indicated above,
the center of gravity of the car is considerably forward of
the center of gravity of the envelope which makes up the
balance of the gross load. An increase of car load has the
effect of moving the center of gravity of the ship forward
and of increasing the nose down angle. A decrease of car
load has the effect of moving the center of gravity of the
ship aft and of decreasing the nose down angle.
A change of 10,000 ft. lbs. in the moment balance with
respect to the center of buoyancy of the ship, whether caused
by a change of total load or by a change of load distribution,
alters the static trim angle by about 1°.
-11-
/
Since the trim angle is measured at full inflation
and at equilibrium a change in the lift coefficient must be
accompanied by a corresponding change in the car load to
maintain equilibrium. Therefoxe, when the lift is greater,
the load will also be greater, and the ship will trim at a
greater nose dovm angle. A difference between the su~ner
and winter trim angles may be observed because of this factor.
At less than full inflation the trim of the ship is
affected by the above factors, and also by the relative
inflation of the ballonets.
(3) Dynamic Lift
The dynamic lift of an airship is the lift which de
pends upon the forward motion and the angle of attack of the
ship with respect to the air. See Fig. III for dynamic lift
at various forward speeds.
The curves plotted in Fig. IV show the variation of the
minimum length of the take-off run of model K-airships with
heaviness and head wind.
The assumptions on which the curves are based are
n~ither exact nor invariable, but they are on the safe side,
giving an over estimate rather than an under estimate of
the required length of the take-off run.
(4) Factors of Safety
The suspension system and the car structure of the K-
airship are designed for a total car load of 16,000 lbs. The
minimum factors of safety at this load are 3.00 for the car
structure and 4.00 for the car suspension.
-12-
/
--- -· ··--·-··------. --- 90· ---~--
70 I -.. 0 , v L. L..
--·----·- -o--__ "
0.7S Fi.JL.L.. POWER
0 ------------------------------------------0 1000 zooo 3000 4000 5000
-9-·-- ---- --.--- ---------.-----,-----.-----------r----------:---------,.------r· · ~--~-----~---------... --~--~-.. --------~---,---------.-.--........_. ______ _
______ .._ ___ _,___ __ , _______ .... ~---- ----;-------- --- ·t·· ------ -·
----------·- ____________________________ j__ --:-----l---·------·------i
- -- - -- --- ---- -------- ..•.
--------_...---------------------~---------,.~----'"-·-----~------~--.-----_...-.------------.----;--- ... --------- ..... - ---~----~----·
-----------·--·-------------------·-·. _______________ , _________ ..._ ___________ ELt;._IJJ: ·- ·- ---------·------1
--··---.. ·---~ __________________________ .... -------=~---=-~~--- /I'l&AMZC:-~~-~~-------______ L__~
l/FT .CHA-RT- ---.- -·--- i
- --------------------- ---- ---- ~-... ·-------------------·- _......_ _____ ._-.)
...
____ , ____ . --.. - -· -- -·- -- .---- -' . .
-· -------··-"""---·- ---~·----·- --~----·------ - -·- .;.... .. _.,__, __ ,. _____________ _,_. ·-· .... ~~---- -- - -~· ~-- ----... ·-·-·-----~
DYNAMIC LIFT VS. VELOCITY
AT IIARIOUS ANGLES OF ATTACK
AND VARIOUS HORSE POWER)
I<- TYPE AIR SHIP
VALuEs BAseD ON K-13 FLIGHT TEsr
VALUEs . BAsED ON /VJ-1 Moe>EL TEsr
8000 9000 10000 11000 12000
----'"1
~ D} !]M I C L IF T ( P 0 UN D S)
.. ------- - 13-
1000 r--\----+VARIATION OF MINIMUM LENGTH OF
TAKG'-OFF !?UN WITH HeAVINESS
AND HEAD WIND
..... BOO
~ FIGURE lY-~
~
700 TAKf-Off CHART
from Bureau o{ Aeronautics
(( SERVICE BULLETIN No. 60
~ 600
~ soo
~
~
~
~ 300
~
zoo
s /0 15 20 2S 30 3S 40
H£AD WIND 7 KNOTS
·-14-
(5) WEIGHT EMPTY
Note: All weights are for ships before K-75.
·ENVELOPE GROUP
Main Envelope Fabric •••••••••••••••••••••••••••••
Ballonets ...........................•. ~ ......... .
Air Lines ...•....................................
Frames •••••••••••••• ~............ 85.7 Lbs.
Fabric Patches & Lacing •••••••••• 109.6
Rip Panels, Complete with cords •••••.••••••••••••
Car Suspension ••••••••••••••••••••••••••••••••••
Inside Catenaries ••••••e••••••••• 524.0 Inside Cables .•••••••••••••••••• 129.6
Outside Catenaries ••••••••••••••• 102.2
Outside Cables •••••••••••••••••• 22•7
Gas Valves & Reinforcement •••••••••••••••••••••••
Air Pressure System ••••••••••••••••••••••••••••••
Air Valve Reinforcement •••••••••• 6.0
Bow Stiffening ................................. .
Bow Cone •••••••••••••••••••••••••
Batten Patches, Laces, Etc. • ••••
Battens ........................ .
Batten Cables •••••••••••••••••••
Mooring Cone Spindle & Pendant •••
Miscellaneous ••••••••••••••••••••
Handling Lines •••••••••••••••••••••••
Drag Rope ••••••••••••••••••••••••
Yaw Lines •.•••••••••••.••••••••••
Handling Lines, All Others •••••••
106.8
102.0
378.0
28.6
45-4 32.5
. . . . . . . . . . .
18.5
39.9
78.8
Fin Suspension, attached to envelope •••••••••••••
Lighting & Bonding System •••••••••••••••••••••••
Car Fairing, Tape Lacing Cord & Padding •••••••••
Miscellaneous equipment, patches, manholes and
sleeves attached to the envelope ••••••••••••
TOTAL ENVELOPE GROUP
EMPENNAGE GROUP
. . . . . . . . . . . . . . . . . . . . . . . .
Upper Fin •••••••••••••••••••••••
Horizontal Fins (2) •••••••••••••
Lov1er Fin ................ · . · · · · ·
Upper Rudder •••••••••••.••••••••
Elevators (2) •••••••••••••••••••
Lower Rudder ••••••••••••••••••••
Fin Brace System ••••••••••••••••
241.0 Lbs.
482.0
217.0
86.0
172.0
56.0
100.0
TOTAL EMPENNAGE GROUP . . . . . . . . . . . . . . . . . . . . . .
5670.4 Lbs .
820.0
195.3
21.1
778.5
68.0
6.0
693.3
137.2
145.6
20.5
31.8
301.6
8895.3 Lbs.
1354.0 Lbs.
TOTAL ENVELOPE & E1IPENNAGE •••••••••••••••••• 10,249.3 Lh~.
-15-
WEIGHT EMPTY
CONTROL CAR GROUP
Car ································L··········· 2250.0 Lbs. Framework •••••••••••••••••••••••• 1056.0 Lbs.
Metal Skin & Skin Stiffeners •••• 436.6
Fabric Covering ••••••••••••••••• 5.6
Windows ••••••••••••••••••••••••• 120.1
Doors Complete •••••••••••••••••• 61.1
Handling Boxes and Doors •••••••• 9.5
Bomb Hatch Doors & Opening Mech. 44.6
Rand Rails and Brackets ••••••••• 32.7
Insulation & Compartment Partition 33.8
Flooring & Supports •• • • • •• •• • • • • 322.6
Access Ladders if carried in flight 16.8
Miscellaneous ••••••••••••••••••••• 110.6
Landing Gear
Landing Wheel As s embly ••••••••••••••••••••• 228.5 Lbs.
~beel & Tire •••••••••••••••••••• 77.5 Lbs.
Fork and Axle ••••••••••••••••••• 45.9
Shock Absorber •••••••••••••••••• 43.6
Retracting Mechanism •••••••••••• 37.5
Miscellaneous Installation •••••• 24.0
Outriggers & Engine Nacelles ••••••••••••••••••• 741.1 Lbs.
Structure •••••••••••••••••••••• 250.0 Lbs.
M e~l Skin & Skin Stiffeners •••• 151.5
Engine Mounts •••••••••••••••••• 78.8
Cowliz.!gS • • . . . . . • . . • . • . • . . • • • • • • 95.0
Engine Nacelles & Stiffeners •••• 165.8
Power Pl ant Group •••••••••••••••••••••••••••••• 2642.8 Lbs.
Engines (as installed) ••••••••• 1858.0 Lbs.
Engine Accessories ••••••••••••• 238.1
Power Plant Controls ••••••••••• 39.9
Propellers ••••••••••••••••••••• 422.8
Stc>.rting System • • • • • • • • • • • • • • • • 84.0
Lubrication System ••••••••••••••••••••••••••••• 154-3 Lbs. Tanks & Protection, Installation 44.1 Lbs.
Oil Coolers •••••••••••••••••••• 60.5
Pumps,not integral with engine 4-5
Piping, etc. •••••••••••••••••• 45.2
-16-
WEIGHT EMPTY
.Fuel System ..•••••..•••••••.•• ~ ..•.•••.••..•.•.•
Tanks & Protection, installation
Pumps, including transfer pump &.
hose •••••••••••••••••••••••••••• 314.4 Lbs.
Piping for Fuel and Vent Systems 233.6
Fixed Equipment ••••••.•••...••••••••••••••••••.
Instruments •••••••••••••••••••• 127.2 Lbs.
Major Controls, complete ••••••• 125.8
Minor Controls, complete ••••••• 42.5
Pressure Tube Assembly ••••••••• 32.6
Electrical ••••••••••••••••••••• 624.8
Communication (Radio & Radar,
MAD, IFF) ••••••• 1098.0
Furnishings •••••••••••••.••••.••••••••••••••••.
Personnel ················~····· 287.4 Lbs. Einergency • • • • • • • • • • • •.• • • • • • • • • • 47.4
Chair Base in Aft Section •••••• 3.2
Navigator's Table •••••••••••••• 19.9
Radio Table •••••••••••••••••••• 26.7
Heating Equipment •••••••••••••• 33.0
Car Ceiling •••••••••••••••••••• 27.3
Rigger's Cabinet ••••••••••••••• 15~0
Navigational Gear Rack ••••••••• 5.3
Miscellaneous •••••••••••••••••• 1.7
Air System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Auxiliary Power Plant • • • • • • • • • • • • • • • • • • • • • • • • • •
TOTAL CAR GROUP . . . . . . . . . . .
-17-