Aircraft fire prevention (Equipment Branch report)

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Auburn University Libra ries
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3 1706 025 851 33 3 NON
File D 52.1 /93 MATERIEL D_IV/rS ION REPORT, SERIA L No. 2794
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-~I
AIR CORPS INFORMATION CIRCULAR
Vol. VI
PUBLISHED BY THE CHIEF OF THE AIR CORPS, WASHINGTON, D. C.
September 15, 1927 No. 592
AIRCRAFT FIRE PREVENTION
( EQUIPMENT BRANCH REPORT )
Prepared by R. Gelzenlichter
Materiel Division, Air Corps
Wright Field, Dayton, Ohio
May 27, 1927
UNITED STATES
GOVERNMENT PRINTING OFFICE
WASHINGTON
1928
' " srovJO oraugMll\
Ra p L\BR~R'l
\"\~'( 2 8 10\:
Non·Oepoitor~. '/
l\ubutn Uni\JeTS\
CERTIFICATE: By direction of the Secretary of War the matter contained
herein is published as administrative information and is required for the proper
transaction of the public business.
(n)
AIRCRAFT FIRE PREVENTION
OBJECT
1. The purpose of this study and series of tests was:
To DETERMINE THE CAUSE AND PROVIDE PREVEN­TIVE
MEASURES IN AIRCRAFT TO ELIMINATE THE
HAZARD FROM FIRE IN THE Arn OR IN THE EVENT OF A
CRASH.
CONCLUSIONS
1. No fires were tr.aced to ignition.
2. Except for two fires of undetermined origin and
one presumably from static, all fires which occurred
resulted from gasoline entering hot exhaust manifolds
and coming in contact with hot exhaust ports or valves.
3. Thoroughly ventilated and drained compartments
are necessary in aircraft to prevent an accumulation of
gasoline, oil or vapor and possible ignition.
RECOMMENDATIONS
1. Structural.
(a) Ventilate all compartments to prevent any
accumulation of gasoline or oil vapors and
to preclude any chance of their being
ignited.
2. Electrical-Continued.
(c) All bare high tension conductors and all bare
safetying devices should be covered by
protectors of an approved ty1pe.
(d) Eliminate metal identification tags on igni­tion
wires.
3. Fuel and oil.
(a) Air-pressure gasoline feed should not be
used.
(b) All lines will be so installed as to prevent oil
or gasoline leaking or being sprayed onto
high tension conductors or exhaust stack
in case of leaky or broken joints.
(c) All drain pipes and vent lines should be long
enough to extend 2 inches outside the
cowling or fuselage and so located that
drainage can not be returned into the air­craft.
· They should be so supported that
they can not be bent out of place when
removing or replacing cowling.
(d) Where there is a possibility of relative
movement between any support or con­nections
there should be a flexible joint
placed near each point of support or con­nection.
(e) The carburetor air scoop should not have
recesses or plugged openings which will
allow gasoline to stand in puddles.
(j) Gasoline tanks should be located where
they will not spill their contents over the
engine. Suggested locations for gasoline
tanks for single-engined airplanes are
listed in order of preference:
(1) Droppable tanks.
(2) Lower wing, near side of fuselage.
(3) Bottom of fuselage, rear of fire wall.
(4) Section of fuselage, behind fire wall.
(5) Upper wing, outside of center sec-tion.
(g) Locate gasoline tanks so as to be subject to
as little shock as possible in case of a
crash.
(h) Provide for dropping the gasoline tank
instantaneously in flight by a mechanism
operated by the pilot; this mechanism
to be so located that it can be readily
inspected without the removal of the
cowling.
(b) The fire wall should fit closely to the cowling
all around the section of the fuselage and
when longerons, pipes, wires, and control
members pass through it, the clearances
should not be larger than necessary for
assembly and after assembly all openings
should be closed with a flexible material
which would delay the progress of flames.
Holes through which nonmovable mem­bers
pass should be closed by rubber
grommets, rawhide or sheet asbestos and,
for holes through which movable members
pass, rawhide is suggested. The fire wall
should have an edge of approximately
one-fourth inch turned forward to act as
a deflector for oil or gasoline and as a
drain through the bottom of the engine
compartment instead of permitting oil
or gasoline to seep through the seams into
the fuselage. Fire walls should not be
painted or varnished except when a bat­tery
is mounted close to it, then acid­proof
paint may be applied to prevent
corrosion in the vicinity of the battery
1
4.
on y. Exhaust.
(a) The cowl openings through which the ex­haust
system passes should have a
minimum of clearance to allow for passage
of stack.
2. Electrical.
(a) Where bare or lightly insulated high tension
parts are used they will clear the parts of
the engine and airplane, which are nor­mally
at ground potential, by at least
three-fourth inch.
(b) All connections of high tension wire requir­ing
safety wire ot other fastenings should
be insulated to withstand the same poten­tial
as the wire covering.
(1)
(b) The outer ends of exhaust stacks should be
cut at 90°.
(c) The manifold type of stack should be at
least 4 inches from the cowl or fuselage to
the inside, parallel to the fuselage. The
individual type of stack will protrude at
least 6 i'nches outside the cowling.
4. Exhaust-Continued.
(d) The exhaust system should p1lss the follow­ing
ground fire test:
(1) Run engine to normal running
temperature.
(2) Induce all possible extra heating
by leaning the mixture and re­tar'ding
the spark. After getting
the exhaust system as hot as
possible, shut off the gasoline
supply to the carburetors and,
as soon as the motor stops, inject
1 ounce of mineral lubricating oil
in stacks Nos. 4, 5, and 6 from
the front.
(3) Repeat this same procedure with
aviation gasoline.
( 4) Each operation to be repeated three
times with no flame resulting.
(e) I ndividual aluminum air-cooled stacks are
recommended for all engine installations
or no stacks at all, except for special
missions.
5. Extinguishers.
(a) Installation of a combination hand and
fixed fire extinguisher on all aircraft is
recommended.
6. Air-cooled engines.
(a) It is recommended that tests be conducted
on exhaust systems for air-cooled engines
when engines are available.
HISTORY
2
1. The problem of fire prevention in aircraft is an
old one and dates back several years during a time
when complete records of various preventive measures
were not kept, but a few of the outstanding studies are
listed as follows:
(a) Underslung main fuel tanks.
(1) Gasoline tanks of 80 and 97 gallons capacity
with rubber crash proof and leak proof
covers were designed to fit under the
fuselages, in the landing gear of DH-4
airplanes. The airplane was slowed up
considerably; was loggy on the controls
and the tank covers became soaked with
gasoline.
(b) Main tanks in lower wing.
(1) A specially designed thick section lower
wing was built and installed on a DH- 4
airplane in which the main tanks were
housed, one in each wing butt. This re­sulted
in the airplane having less speed,
being more sluggish on the controls and
the longitudinal stability was not all that
could be desired.
(c) Tanks on upper wings.
(1) Two cylindrical tanks of a combined capa­city
equivalent to the standard DH- 4
airplane were installed over the inner
bay strut points on the top surface of the
upper wing. This resulted in slower
speed and sluggish controls.
( d) Air starters.
(1) The use of air starters was considered be­cause
of the possibility of eliminating the
battery system of starting, but, because
of the simplicity and trustworthiness of
the electric starter in comparison, the air
starters were abandoned.
(e) Aluminum manifolds.
(1) Various styles of aluminum manifolds, made
of sheet aluminum welded after the man­ner
of the regular steel Liberty manifold
and of aluminum and aluminum alloy
cast in sections to eliminate the expansion
difficulty, were constructed and tested but
were unsuccessful due to heat, expansion,
and gas pressure.
(f) Carbon tetrachloride bombs.
(1) Fragile containers made of "Pyrex" glass
were installed directly behind the engine
so that in case of a crash they would
break and flood the engine compartment
with a liquid to prevent fire. Each
"bomb" held two quarts of carbon
tetrachloride and was installed as shown
in Figure 1.
(g) Sprinkler systems.
(1) A great number of sprinkler systems have
been investigated and tested and the
underlying principle of operation is
practically the same in all, i. e., the extin­guishing
agent is expelled from the tank,
through suitable piping, nozzles, etc.,
over and around the engine by means of
air pressure within the tank. Most of
these systems are not reliable due to
leakage caused by vibration of the air­craft
and the corrosion of parts. Systems
have been designed of late though that
seem very promising, the most satisfac­tory
type being the Air Corps types B- 7
and B-8.
2. The following figures were compiled to show the
fire hazard in crashes of service airplanes:
Summary
_______________ 1 rn21 \ rn22 1923 1924
Reports received ____________________________ _
Number or persons in accidents _____________ _
Number or fatalities _____________________ _____
1
Number or fires in the air. __________________ _
Number of fires after crash __________________ _
Number of fatalities after crash, fire . . ------ - -
CRASH TESTS
131
202
3~ I 14
16
92
164
32
1
18
22
158
262
31
2
10
13
179
298
30
0
9
13
1. Authority was granted for the construction of a
crash runway for the destruction of obsolete and un­serviceable
aircraft in an effort to obtain authentic
engineering data as to the actual causes of fires in
aircraft. This runway was completed July, 1924, and
is approximately 566 feet in length, the first 360 feet
of which is a grade of about 4.85 per cent and the
difference in elevation of each end being about 20 feet.
At the lower end a reinforced concrete wall 10 feet
3
FIG. !.-Two carbon-tetrachloride bombs installed in front of fire wall on DH-4 airplane
FIG. 2.-Crash runway, showing guide rails for landing gear wheels, concrete wall, and shelters for photographers
wide, 3 feet thick, 14 feet above and 6 feet below ground
was constructed. Shields and bomb shelters were
placed in several locat ions, near the wall, for the pro­tection
of photographers and observers. Figure 2
gives a good idea as to the general character of this
runway.
2. Obsolete and salvaged aircraft were procured and
assembled with gasoline t anks, power plant, landing
gear, and other necessary equipment, but minus wings.
The airplanes were then started from various points
4
along the runway and after t he engine was sufficiently
warm they were released and allowed t o crash into the
wall at the foot of the runway; the idea being to simu­late
the worst condit ions of a crash , and slow motion
pictures, as well as normal speed pictures, were taken
from either side. These pictures, after development ,
were studied under a microscope and the definite start
of the fire located whenever a fire occurred.
3. Crashes were conducted under various condit ions
and are tabulated as follows:
CRASH SERIES No. 1- JuLY 30, 1924 , To APRIL 29, 1925
T ests to determine the source of fire on crashing- other than i gnition
Date Type airplane Engine Exhaust manifolds Fuel tanks Gasoline system Ignition system Remarks
July 30, 1924 ______ Dff-4B _________ Wright ff _______ Short stacks _______ Plain ____________ Sylphon pump _ Magneto ________ __ No fire.
Oct. 13, 1924 ______ Orenco _____ __ ___ __ __ _ do ___________ ____ do . ... ... ------ Leak proof. __ ________ do __________ ..... do___ ___ _______ Do.
. {Generator_________ Do.
Oct. 27, 1924 __ __ __ U$D-9A ________ Liberty 12 ______ Standard Dff-4 ... __ __ _ do __ ________ Gear pump _____ Batte r y (de- }Fire
strayed). ·
Jan. 13, 1925 .• . ••.• Loening PW-2 .. Wright ff _______ Short stacks _______ Crash proof. ____ Sylphon pump _ Magneto __________ No fire.
Jan. 14, 1925 .. . __ __ T. M. MB-1J _______ __ do ________________ do ____________ Plain ____________ ..... do _______________ do_____________ Do.
Do ____ __ _____ J -1Jff _______________ do ___________ 12-inch stacks __________ do ___________ Air pressure ____ _____ do_____________ Do.
Do _ ____ __ ____ T . M. MB-3 .... _____ do ___________ 3-inch stacks ______ Leak proof. _____ Sylphon pump ______ do_____ ____ ____ Do.
F b 26 1925 USD-gA--------} . {Standard Dff-4 .•. } . . {Generator ___ ___ ___ Do. ~ar· 12
•
1925
------ Dff-4B Li berty 12 ______ .... do _____________ P lam ________ __ __ Gravity ________ Batte r y (de- }F;•e
· • ------ ------ --- Saxophone____ ____ strayed). u •
Mar. 26, 1925 .•.... ___ __ do __________ ..... do ______ ___ _ S ho r t 12-inch _____ do ___________ Air pressure _____ Batte r y (do- To fire.
Apr. 3, stacks. strayed). 1925 ____ ______ __ do ________ ___ . . ... do ___________ 12-inch stacks ____ ______ do _____ ___________ do ___________ ..... do _____________ Fire.
Do _______ ____ X B- JA ___ _______ Wright ff _______ Saxophone ____ ____ Leak proof._____ ylphon pump _ Magneto__ __ ______ Do.
Do ___________ Fokker DVH ________ do ________________ do _______ ______ Plain ___ __ _______ Air pre ure _________ _ do ______ ______ No fire.
Apr. 8, 1925... •.•.• Dff-4B _________ Liberty 12... ... . {~~~\ihagj~~~~:: } .... do __ ____ ___ _____ _ do __________ {B s~r~~:d').Y (de- }Fire.
Do _ ____ ______ XB-lA _________ Wright ff _______ None _____________ Leak proof. ___ __ Sylphon pump _ Magneto____ ______ To. fire.
Apr~i;iiiu:::::: : ii~:-::B~~~::: -L"iiie~~ii~i_:::::: :::::~~::::::::::::: -~1~!:1;:,::::::::::: -~~i~-S~~~~~~~~:::: -il·a-i0I t"e·r·y-·(ae:· g~: strayed) .
;;~:~'.~•· ·~~·~0••;::~~~~;,;•••• ••:·~:·:••:••::• :~:.!f.·~::•::: =~,~~,·:~~;,,•co~: ~• Apr:;9;-iii5_-_::::: ~~1c~i--nvii~::1·i,.vi-i~~i-:H::::::: :::::~~::::::::::::: :::::~~::::::::::: :::::~~::::::::::: -M:a·:iei<i:::::::::: Fir~0 ·
SUMMARY OF CRASHES
T ABLE 1.-Fires occurring in their relation to ground
temperatures
Temperature.degrees Number Number
~ Fahrenheit crashes fires
2191_ . ._ ___: _____ -_-_-__-_- -_-__-_- -_-__-_-_- -_
24 ___ ---- - - - - --- ---- - - - -
41_ __ ------ - - - - ---- -- - - -
48 __ _ - - - --- - --- - -- --- - - -
50 ___ ------ -- - -- -- - ---- -
52. -- ---- ----- -- -- -- --- -
55 •• - - ----- - - - - - -- ----- -
57 - - - - - ---- -- - - --- ____ _._
68 _____ - - ---- -- -- - -- --- -
71. ____ -- -- -- - -- - - -- ----
75 ___ ---- - --- -- - ---- - - - so __ ___ ---------- -------
Total. -- - ---- - ----
1
1
3
1
6
5
3
1
1
1
1
1
1
26
0
0
0
1
3
2
0
0
0
0
0
0
0
6
; Comment.-It bad been suggested by a number of
pilots that the ground temperature might have a
considerable effect on the likelihood of fires occurring
on crashes. While it is believed this may have some
effect , it is not t hought that the above tabulation
shows any data that will be at all conclusive. There
are a good many other variables present that are not
shown in the above tabulation.
TABLE 2.-Fires in respect to the kind of gasoline tank
Kind of tank I N=l =0
· crashes fires •
------
Leak proof or crash prooL_________________ ___ ____ 8 2
Plain ·------------------------------------- --------___1_ 8 4
T ot al . --- - - --------- -- ---------------------- 26 6
Comment.-The same remarks apply to this analysis
as to Table No. l. It bas been noted, however, from
a study of the pictures made at t he time of the cra~h.
that the airplane has to strike at a speed of approxi­mately
50 miles an hour before a complete rupture is
made of the rubber-covered leak-proof tank, and it is
believed that the use of a rubber-covered tank on
service airplanes will r esult in the diminution of fires
on crashes.
TABLE 3.-Fires with respect to ignition systems
System
crashed fires
Remarks N=-1 Nb1e1;1-
~~~~~~~~-1-~~
Magneto_ -- ------------
Generator alone._-----­No
ignition (battery
only carried ; de­stroyed
Just before
crash).
14 2 1 fire at end of exhaust mani­fold;
1 fire at exhaust port.
1 Fire at end of exhaust stacks.
3
2
10
All systems •••.•.• ~ --6
Comment.-The preceding table is not at all complete
as no actual investigation of ignition systems had been
carried out. Before the fire hazard of ignition systems
can be determined, it will be necessary to completely
whip the possibilities of fire from exhaust stacks and
to then proceed with various kinds of ignition systems.
It is believed1 however, that the above table shows,
with fair conclusiveness, that magneto ignition is not
a fire hazard of any noticeable magnitude.
TABLE 4.-Fires, as to gasoline systems
I Number I umber
________s_ yst_e_m_ _______ crashed ~
Air pressure __ ____ ______ ___ _ ------- __ ------------- 14 3
10 2
2 1
Gear or sylphon pump ..... .........•....... . . ...
Gravity ..... .•.•................ ... . ..............
All systems ............... . ................ . 26 6
Comment.-Many other variables are not taken into
account in the above analysis. It will be noted that
there is no difference distinguishable in the results
obtained between air pressure, pump feed, or gravity
feed gasoline systems.
TABLE 5.-Fire, in relation to exhaust systems
Kind of exhaust system
"Saxophone" manifold ____ ________ _
Night-flying manifold ............. .
Individual stacks 12 inches and less
in length . . ......... ..... ... . . ... .
No exhaust stacks .... ......•... . ...
Num­ber
Of
crashes
8
12
Total... ...................... 26
Num­ber
of
tires
Remarks
Caught from ex·
llaust port.
5
Comment.-The preceding table represents the most
conclusive evidence gained so far. It shows that, dis­regarding
ignition, the exhaust system is mainly respon­sible
for fires.
TABLE 6.-Exact origin of fires as determined from
observation
End of exhaust mant.old ...•••..• ••.•.....•.................•
Not distinguishable . .•.......•.•.•••..•....•..•.............•
Exhaust port ••.• -------- ..... _ .. ___ __ -----.. _ . . .. ___ ......•.
Total. ____ .. -- . --- •. -- - . - - -- - . - . -•. -- --- --- . - -- -- - --··
Number
of fires
Comment.-It will be noted that of the six fires the
start of all but one of them was easily determined from
a study of the motion pictures. The above table is
merely a supplementary statement, giving conclusions
already arrived at in Table 5.
Method of test.-After making a number of crashes
it was found advisable to modify the runway in order
to raise the tail of the airplane by means of an out­rigger
at the moment of impact and so deluge the
engine with gasoline on crash. The length of run was
also changed to 300 feet, in order to reduce the force
of impact to a more reasonable figure. See Figures 3
and 4.
In order to preclude the possibility of fire from the
ignition system the generators were removed and the
battery mounted on the landing-gear axle, where it was
knocked off by striking a stop in the track 25 feet from
the wall.
CRASH SERIES 0 . 2 .- JUNE 4, 1925, TO SEPTEMBER 11, 1925
Miscellaneous tests of 12-inch air-cooled aluminum individual exhaust stacks
Date Type airplane Engine
Type of airplane Exhaust
DH-4 .•••.••.•.•.•.....•.• 12-inch air cooled •••... . . ..
SNaoxnoep.h-o-n--e.- -__-_-_- -. -_-_-__-_-_-_-_-_- -_
Exhaust manifolds Fuel tanks Gasoline system Ignition system Remarks
Num-ber
of Fires
crashes
10
5
1
0
1
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Comment.-This indicated that aluminum individual
air-cooled exhaust stacks are not sufficiently hot ·to
ignite when gasoline is thrown over the engine from
bursted tanks.
6
Fm. 3.-View showing ramp at foot of runway, in order to lift tail of the airplane before crashing
Fm. 4.-Typical crash after ramp .was installed
7
CnASH SEnIEs No. 3.-I ovEMBER 10, 1925, To DECEMBER 7, 1925
T ests to determine effectiveness of rubber-covered gasoline tanks and using magneto ignition and 10Y2-inch straight
steel individual exhaust stacks on a Wright engine
Date 1 Type airplane Engine Exhaust mauHolds Fuel tanks Gasoline system Ignition system J Remarks
Nov. 10, 1925 ___ ___ MB-3 _____ ___ __ Wright H ____ ___ IOY.-inch steel__ ___ Rubber covered_ Gravity ___ _____ Magneto _________ _
Dec~~:~~i~:::::::;:::::g~::::::::::: :::::~~::::::::::: :Iiig~~~~:~i=~~== :~Jg~~~~:r:::::: :::::~~:::::::::::,:::::g~:::::::::::::
-o fire.
Do.
Do.
Do.
Type of
airplane Exhaust Ignition
I
'l'anks Crashes Fires
Comment.-Straight steel stacks apparently run
s ufficiently cool on the Wright engine to eliminate fire
hazard even though the tanks did not prevent con-
MB-3 ____ lOY. -inch Magneto ___ ___ Rubber cov- 4 o siderable gasoline lleing pou red over the engine.
straight
steel.
Date
ered
CRASH SERIES ro. 4.- FEBRUARY 16, 1926, TO MARCH 24, 1926
Test to determine efficiency of 10Y2-inch straight steel individiwl stacks
Type
airplane Engine Exhaust manifolds Fuel tanks Gasoline
system Ignition system
Feb. 16, 1926 __ ----- - - - - - - - DH ____ __ Liberty ___ lOY.-inch straigbt steel. Plain ______ Gravity __ Generator-battery (destroyed)_
Do __ ___ __ ---------- --- ___ do ____ ___ ___ do ______ ______ do ___ ________ _____ __ __ do ____ ___ ___ do _____ __ ____ do ______ ----- -- ___ -----_ . __
Do ____ _______ -- -- -- --- ___ do _____ __ ___ do ___ _____ __ __ do ____ ____ -- ---- -- __ __ do __ ____ ____ do __ ___ __ I ____ do ____ _______ __ --- ---------
Febglt1:~~~:::::::::::::: :::g~::::::: :::~~::::::: :::::~~::::::::::::::::: :::~~::::::: :::g~:::::::J:::::gL:::::::::::::::::::::: Feb. 26, 1926--- -------- - -- ___ do ____ ______ do ____ ___ ___ __ do _____ ___ ____ ______ __ do ___ __ __ ___ do _______ ___ __ do ________________________ _
Do ___ __ __ ________ __ __ __ .do ______ ____ do ____ ____ ____ do __ ___ ----- __ ----- ___ do ___ __ ___ __ do ______ _____ .do ___ __ _________ -----------
Mar1:f 6,-i926:::: :: : :::: :: : :: :~g::::::: :: :~g::::: :: : ::: :~g:::::: :: : :: :: : : : : : ::~g::::: :: : : :~g:::::: :I:::: :~g:::: :: ::: : : : : : :: : ::: : :: :: Do _ ___ __ ---- - -- ------ ___ do _____ _____ do ____ ________ do ___ ___ ___ ---- ---- ___ do ___ __ _____ do ___ ________ do _______ . __ _ -- ---------- --
Mar. 24, 1926-- --- -- ------- ___ do _____ _____ do ____ ________ do ___ ________ _____ ____ do __ ________ do ___ __ _____ do ____ ______ ___ __ ______ ___ _
DO------ --------- ---- - ___ do __________ do ____________ do ____ _______ _________ do __________ do ________ __ __ do ______ _______ _____ ___ ___ _
Do _ ------ _____ __ ________ do __________ do _________ __ do _______________ _____ do __________ do _____ __
1
____ _ do ______ ____ _____ _____ ____ _
all of the fires started from the exhaust stacks.
Remarks
Fire.
No fire.
Do.
Do.
Do.
Fire.
No fire.
Do.
Do.
Fire.
No fire.
Do.
Do
Do.
Out of
Type or ai rplane Ignition
DH ________ __ Generator-battery
(destroyed).
Exhaust I Crashes
JOY. inch straight I 14
steel.
Fires
3
the 14 airplanes crashed 4 were designated "no test"
as examinations of the motion pictures clearly showed
that no gasoline reached the exhaust stacks and 1
other airplane was doubtful because of a similar
condition.
Comment.-The use of straight steel individual ex-
!must stacks is not satisfactor y on Libert y motors as
CRASH SERIES No. 5.- JuNE 10 TO J u LY 17, 1926
Tests to determine if the generator and battery i gnition system was a cause of fire
Date I ~ype airplane Engine Exhaust manifolds Fu~! tanks Gasoline system Ignition system
June 10, 1926 ____ __ XB-lA __ _____ Liberty __ _ o stacks __ _______ Plam __ ______ Gravity __________ Battery-generator_ ________ _ _
Do ______ ----- _____ do ______ .. ___ do __________ _ do ____ ___ ___ __ . _____ do ______ . ___ .. do _______ -- -- -- ----_do __ ___ _____ ---- __ __ ----
Do ___ __ ______ - ---.do __ ___ ___ ___ do _____ _______ do ___________ __ ----_do _______ _____ do ___ ____ --- --- __ __ _ do ____ __ __ ______ --- -- -- -
June 15, 1926_ - - - -- _____ do __ ______ .. _do ___ ____ ---- .do ____ ___ _____ ___ __ do ____ ___ _____ do _______ ___ __ ______ do ____ __ ___ _______ -- --- --
Do ______ --- -- __ .. _do ____ _____ __ do _____ _______ do ______ ______ ___ ___ do _____ ___ __ __ do ____ ___ ____ __ ___ __ do _____ ____ ---------- ----
Do _ ___ -- ----- _____ do _ __ ______ __ do _______ __ ___ do _____ ____ _____ ____ do __ _________ _ do __ __ ____________ _ do _____ __ _______ ____ ___ _ _
J un~l?:_~~~~~~~~~ ~ ~~~ ~~L~ ~~ ~ ~ ~~ j~~~~~~~~ ~ ~~ j~~~~~~~ ~ ~~~~~~I~ ~~~jL~ ~ ~ ~~ ~~ ~~L~~~~~ ~ ~~ ~~ ~~ ~~ ~~~~~~~ ~~~ ~~ ~~~~~ ~~ ~ ~~ ~ ~~ ~
Remarks
Fire.
No fire.
Do.
Do.
Fire.
Do.
No fire.
Do.
Fire.
No fire.
Type of ai r­plane
Ignition Exhaust
Num­Crashes
ber of
fires
XB- LA ___ ___ Generator-bat tery_ None_________ _____ JO
Comment.-One fire was caused by static upon
impact, t he motor striking a spark upon the steel
rails which had been installed to reinforce the wall.
One fire was of undetermined origin and two fires
started in No. 1 exhaust port on left bank of engine.
No fire could be traced to the ignition system.
76293· - 28--2
8
CRASH SERIES No. 6.-JuLY 15 To SEPTEMBER 30, 1926
Miscellaneous tests of magneto and battery ignition in different types of airplanes
Date Type airplane Engine Exhaust manifolds Fuel tanks Gasoline system Ignition system Remarks
July 15, 1926 _______ DH-4B_ ---------- Liberty_------ None _____________ Plain __________ Gravity __________ Magneto __________ ~~efue .
~1:~111111 :!l~-""11 •!~li!liilii :~lliill~li ~1~ililil~ lill liillllllillll !~1~:11:1111: II
Type of
airplane Motor Exhaust Ignition
DH-4 _____ Liberty ___ None _________ 2 magnetos, 1
spark plug to the shell. This is considered a fire
Crashes Fires hazard. A corona was present at the end of the
spark plug wire conduit. No. 5 plug on inside of left-
1 hand bank, which is approximately seven-sixteenths
battery.
MB-3 _____ Wright ___ Straight steeL Magneto _____ _
XB-lA ____ Liberty ___ None ___ ___________ do ________ _ 2
6
1
1
inch from carburetor, had a constant jump spark to
g the carburetor.
Br~guet ______ do ___________ do _________ Battery ______ _
VE-9 _____ Wright ________ do _________ Magneto _____ _ 0
0
Comment.-One fire occurred and was of undeter­mined
origin, starting nine seconds after the crash.
It is evident that this ignition is not a fire hazard and
also indicates that straight steel individual stacks are
not a hazard on Wright engines.
GROUND FIRE TESTS (IGNITION)
1. In accordance with order 651-1-72 five different
airplanes with different type of engine installation were
tested on the night of July 14, 1926.
2. The primary reason for these tests were to
observe where sparks (if any) might occur throughout
the system. These tests were observed by representa­tives
of different sections and proved very satisfactory.
The following airplanes with the engine installations
are described in order:
Type P-2, P-431
This airplane is equipped with a Curtis engine with
the distributors on the rear end of each cam-shaft
housing. At 1,000 revolutions per minute a spark from
the wire feeding the right-hand distributor with high
tension current from the magneto would take place
intermittently, and at higher revolutions per minute
would become more frequent. This spark was at a
point between the wire and the gun synchronizing
torque bracket. There was a continual visible flame
at the distributor vent. At different spark plugs the
insulating nipples were removed and an occasional
spark was noticed from No. 3 inside spark plug on
right-hand bank to the intake manifold.
Type 0-1, P-437
This airplane is equipped with a Curtiss engine and
proved that dirt may be considered a fire hazard.
No. 1 spark plug on inside of right-hand bank was dirty
and a constant spark would jump from the head of the
Type XC0-6, P-360
This airplane was tested and proved very satis­factory.
The only recommendation is that the spark
plug wire conduit· be opposite from its present installa­tion
so that the wires will come out of holes on the
bottom instead of the top; this will allow the conduit
to drain itself of any foreign liquids.
Type VE-9, P-204
This Vought airplane with Wright engine installa­tion
proved much worse than anticipated. A decided
sparking was noticed between all wires where near
any grounded parts. Sparking occurred at all wires
including the low tension. A very decided corona
appeared at the ends of the conduit between the mag­netos.
Type 0-7, P-432
This airplane is equipped with a Packard 1,500
engine with the distributor in the middle of cam shaft.
At low speed the distributor shows no visible electrical
phenomena but at high speed the segment on the dis­tributor
had the appearance of a grinding wheel
throwing off sparks. Sparks passed from plug of No. 2
cylinder on inside of left-hand bank to bonding. A
large corona was visible around coil in the vee under
the distributor and around spark plug wires where
massed together. All spark plug wires where close
together and having metal tags with cylinder num­bers
would jump spark from one to another.
Comment.-The above tests indicate that definite
action should be taken to prevent sparks occurring
during normal operation of the engine or to completely
insulate the sparking part from any possible source
of fuel. Definite recommendations are as follows:
(a) No high-tension ignition wires should be used
which are not fresh or do not comply with
approved specifications.
(b) The use of metal marking tags should be dis­continued.
(c) In case it is not possible to immediately com­ply
with the Handbook provisions for a
minimum of three-fourths inch clearance
between the high-tension conductor and
grounded metal, the wires should be pro­vided
with extra insulation and securely
fastened in place in such a manner as to
prevent arcing from the high-tension con­ductor
to grounded metal or other high-ten­sion
wire.
(d) Particular care should be taken to insure the
outer surface of the spark plug insulator
being kept clean.
(e) Ignition apparatus in which the coil and dis­tributor
are separated should not be used.
(f) In case a jump-gap distributor is used, it
should be totally inclosed so as to avoid
contact between fuel and the sparking gap.
EXHAUST STACKS
1. Two runs were made on Liberty engine installed
on DH-4B fuselage. The standard "saxophone"
type exhaust manifold was used. Temperatures were
taken with a thermocouple, as per sketch below:
Readings were taken by inserting the thermocouple
in small holes in manifold opposite the exhaust ports.
First run-Full throttle, lean mixture, retarded spark,
engine water temperature 62° to 65° C.
Location
Tempera­tures,
de­grees
Fah-renheit
No. L--- - -- -- ------ 1, 020
No. 2_ ____ __ ________ 1, 250
No. 3------ - - ------ - 1, 285 ' o. 4__ ____ __ _______ 1, 220
No. 5----- ---- --- --- 1, 160
No. 6______ _____ ____ l, 230
End _______ _________ 1,400
Second run-Full throttle, lean mixture, retarded spark,
engine temperature, 60° C.
Location
NNoo.. 2L _-_-_-_-_-_-_-_-_ -__--__--_- NNoo.. 43 -_-_-_-_-__-_-_-_--_-_-_-__- -_
No. 5 __ ____ _______ _
No. 6 ____ __ ___ ___ _ End--- ------- -- ----
Tempera­tures,
de­grees
Fah-renheit
1, 230
1, 3l0
1,300
1, 220
1, 130
1, 140
1, 330
The peculiar result of getting higher temperatures
at the end than at the port raises doubt as to the
accuracy of the measurements, or must indicate after
burning in the stack.
9
2. Runs were made on the same DH-4B. The left
bank of cylinders exhausted into a steel water-jacketed
exhaust manifold mounted in place of the standard
saxophone manifold used previously. Readings were
taken with a thermocouple as before:
First run-Engine water temperature 65° to 85° C.
revolutions per minute 1,325, full throttle, retarded
spark, lean mixture
Location
No. L ___ ________ __ _
NNoo.. 32 -_-_-__-_-_-_--_-_-__-_-_--_-_
No. 4 ______________ _
No. 5 ______________ _
NEnod. 6_-_-_-_-_-__-_-_-_-_-_-_-_-_- -_
Tempera­tures,
de­grees
Fah-renheit
1, 310
1,360
1,400
1, 290
1, 270
1, 220
1,310
Second run-Engine water temperature 85° C., revo­lutions
per minute 1,440, normal (rich) mixture,
advanced spark, full throttle
Location
No. L-- ----------- ­NNoo..
32- _-_-__-_-_-_-_-_-_-_-_-_-_- -_
No. 4 ____________ __ No. 5 ___ __________ _ No. 6--------------­End
. ••. --------- -- -
Tempera­tures,
de­grees
Fah-renheit
1, 000
1,080
1, 120
1, 150
1,070
1,000
900
3. A Wright 300 horsepower engine, mounted in an
XB-lA airplane fuselage, was tried out with a water­cooled
manifold. Temperature readings were taken in
a manner similar to those on the Liberty engine.
First run.-Water temperature 70° to 80° C., lean mixture,
full throttle
Location
NNoo.. 2L _-_-__-_-_--_-_-_-__-_--_-_ -_
No. 3--------------­No.
4- --------------
End .. ------_ ---- __ _
Tempera­ture,
de­grees
Fah­renheit
1, 100
1, 100
1, 190
1,200
890
No fire resulted on injection of gasoline or oil into
end of stack, following the run.
Second run.-W ater temperature 80° C., rich mixture, full
throttle
Location
No.L ___________ __ _
No. 2--------------­No.
3------------ --­ENnod.
4__-_-_-_-_-_-_--_-__- ----------
Tempera­ture,
de­grees
Fah-renheit
1, 080
1, 110
1,250
1,250
810
10
I o fire resulted on injection of gasoline or oil into
end of stack, following the run .
4. The water-cooled manifolds were then removecl
from both engines and standard manifolds installed.
Temperatures were taken as before. ·
Liberty engine in DH- 4B airplane, run at full throttle,
lean mixture and retnrded spark, engine revolutions per
mimite, 1,275
Loca tion
No. L _____________ _
No. 2 ______ ________ _
No. 3 _________ _____ _
No. 4. ______ _______ _
No. 5 _______ ____ ___ _
No. 6 ______________ _
End ___ __ ________ __ _
Tempera­ture,
de­grees
Fah-renheit
1, 040
1, 050
1, 170
1, 060
980
1, 130
1,380
Fire resulted from either oil or gasoline injected into
encl of exhaust stack end.
Wright " H " engine in XB- JA fuselage; rull throttle,
lean mixture
Location
Tempera­ture,
de­grees
Fah-renheit
No.!._______ _____ __ 1, 130
No. 2___ ___ _________ 1, 150
No. 3__ ___ __ _______ _ 1, 220
No. 4.____ __________ 1, 300
End ____ ______ ______ 1, 380
Fire resulted when gasoline or oil was injected into
the end of the manifold.
Comment.-It was shown by above tests that fire
could be expected from a standard, uncooled exhaust
stack whenever gasoline or oil was injected into the
stack, following the running of the engine. With the
water-cooled exhaust manifolds t here wa.s no sign of
either smoke or fire when the oil was injected. The
water-cooled manifolds were very heavy, being made
of sheet steel, with no attempt to save weight. Work
is to be done, leading to a reduction in weight by the
use of less water and lighter material.
5. A test was run on a standard steel "saxophone"
manifold, with a connection for introducing C02 into
the manifold.
Fii:st run- Check. Engine run up to normal flying
condition and gasoline shut off. On stopping, 8 cubic
centimeters oil was injected into hole at No. 5, using a
hypodermic. Fire resulted.
Second run-Engine as before; C02 valve opened
slightly. Engine stopped and 8 cubic centimeters, oil·
injected. Smoke, but no fire resulted.
Third run-Engine as before; oil injected when engine
stopped. Fire resulted. C02 valve opened slightly .
Fire went out in three seconds.
o cooling action was noted on the manifold. Very
little C02 used. The effect was as though the fire was
being smothered. Tests will be made, using measured
quantity of C02•
6. T ests were then made on various t ypes of short
exhaust stacks, arranged as follows:
(.._ __: ;:-::::.::__ __) ~· Propeller.
No fire, oil or gasoline, 3 trials 11-U+t+HH, 12-inch
finned, aluminum. lt-ttttttttf
No fire, oil or gasoline, 3 trials~ 12-inch
finned, aluminum. u-+tttttttf
Fire every time, oil or gasoline n l 12-inch
plain, steel. u,__ __ _
Fire, oil or gasoline p 10-inch plain, steel.
Fire, oil or gasoline p 8-inch plain, steel.
Fire, oil or gasoline (J:::J 6-inch plain, steel.
The finned air-cooled stack is made to the following
design:
Tube, duralumin, 2 inches inside
diameter, Ys-inch walls, 12 inches
long, with 16 circular fins welded
at top side. Fins of aluminum,
6 inches in diameter, Ys inch thick.
Engine was run at full throttle and as lean as possible.
Lubricating oil and gasoline injected into the ends of
each of these stacks caught fire, the oil catching fire
more readily than the gasoline. No fire resulted from
the aluminum stacks.
7. An open-ended steel exhaust manifold of the
description shown below was tested out. It caught
fire quite readily. As the individual leads to the mani­fold
are capable of catching fire, it is not believed
worth while to continue tests on t)lis type of manifold.
See Figure 12.
f0 0 llllllllllll
8. A C02 bottle containing 272 ounces of C02 was
mounted on a manifold, as shown below, by means of
a suitable joint. The engine was run up to speed and
gasoline cut off. The C02 bottle was given a blow
with a hammer, releasing the C02, and a fraction of a
second later lubricating oil was injected into the open
end of the manifold. A fairly dense white smoke re­sulted,
which lasted until the C02 was exhausted. It
then caught fire. There was no noticeable reduction
in temperature of the stack due to the flow of carbon
dioxide. This development will be abandoned, due to
necessary complication of the system for automatically
turning on C02 and the doubtful value of C02 after it
is turned on. See Figure 5.
9. Test of row of aluminum manifolds.-A test wa
made by injecting oil into stacks immediately after a
full lean run. None of the stacks could be fired. Size
of the fins was cut down from 6 to 4.45 inches in diam­eter.
See sketch below and Figure 15.
o. 1 and No. 6 were then replaced by straight
stacks of aluminum, without fins. It was found that
oil ignited in these 70 per cent of the time. A number
of runs were made without exhaust stacks, oil being
sprayed on the bare exhaust valve. No fire resulted.
10. Water-cooled aluminum manifold.-A manifold
of the general design shown in sketch below was then
tried out. This manifold weighed 12 pounds empty
and 2172 pounds full. The temperature rise in this
manifold was from 12° to 20° C., water "in" being 68°
and water "out" 87°. There was no sign of fire.
See Figure 9.
\TO~
~1VPUl1P
11. Weights of exhaust systems.-
Water-cooled saxophone stack, 2172X2=43 pounds
(plus water).
Steel saxophone stack, 1272X2=25 pounds.
Twelve-inch sheet aluminum finned stacks, 372X 12=
42 pounds.
Twelve-inch plain steel stacks, 172X 12= 18 pounds.
11
12. The Liberty engine in DH-4 fuselage was tested
with short air-cooled exhaust stacks. Cast stacks
were placed on right bank on the first five cylinders
and a sheet metal stack on the cylinder next to the
fire wall. The left bank exhausted into the water­cooled
manifold with the aluminum tail pipe. The
engine was run for five minutes with advanced spark
and rich mixture and was stopped by shutting off
gasoline supply.
F!Re Wllll
TlflL Pl?e
After waiting 15 seconds, oil was injected into No. 5
stack, and after 15 seconds more, into ro. 6 stack.
This operation was repeated three times without any
fire being evidenced. The cycle of operations was
then reversed, oil being injected into No. 6 stack after
15 seconds wait and then 15 seconds later into No. 5.
No fire resulted. Following this series of tests, the
engine was run for one-half ·hour at 1,250 revolutions
per minute, with lean mixture and retarded spark. On
stopping the engine, oil was immediately injected into
No. 5 and No. 6 stacks. r o fire resulted. The
engine was then run as before, for two and a half hours
and No. 6 and No. 5 stacks immediately tested with
oil. No fires resulted. During the above running,
there were no mechanical failures on either the air­cooled
stacks or the water-cooled manifold.
13. The fol lowing set-up was made to determine
what heat was being taken from the 'vater jacket on
the exhaust manifold:
EN51NE
First run-350 pounds water from 25° to 52° C. in
9.4 minutes.
Second run-350 pounds water from 25° to 52°C.
in 10.5 minutes.
Third run-350 pounds water from 25° to 52° C. in
10.5 minutes.
A verage-350 pounds water from 25° to 52° C. in
10.1 minutes.
This is equivalent to 17,000 British thermal units in
10.1 minutes, or 1,685 British thermal units per
minute, and this is equivalent to 39 horsepower. For
two manifolds, the horsepower absorbed by the
cooling water will be about 78 to 80.
12
Following the above, a second series of runs was ' 14. In addition to the above, numerous other mani­made
under conditions allowing for a better control of folds and systems were investigated. The following
the rate of flow of water thru the jacket on the manifold: figures illustrate their design:
First run-350 pounds water from 26° to 67° C. in FIGURE 5.-Standard manifold type with bottleof
16.1 minutes. carbon dioxide to release gas on impact .
. Second run-350 pounds water from 26° to 66° C. FIGURE 6.-Standard manifold type with bottle of
in 16.03 minutes. water or carbon tetrachloride in rear to break and
Third run-350 pounds water from 26° to 67° C. in flood manifold on impact.
16.1 minutes. FIGURE 7.-Standard manifold type with air-cooling
Average--350 pounds water from 26° to 66.5° C.
in 16.07 minutes. arrangement on tail for cooling the end.
FIGURE 8.-Aluminum water-cooled stack in series,
This is equivalent to the absorption by the cooling
water of 37.4 horsepower. For two manifolds it equals with cooling system, open at front end, with Jong tail
75 horsepower. The present DH-4B radiator will pipe.
dissipate through cooling 246 horsepower. If the .FIGUR~ 9.-Alumii:iu~ "'.ater-c.ooled stack in seri~s
water jacket of present design is used, it will be neces- with cooling system srmilar rn design to standard mam­sary
to increase the radiating surface by 30 per cent. I fold type.
The present booster radiator will dissipate 61 horse- . FIGUR~ 10.-Cast alumin_um stack with fi.ns thre~­power.
It weighs 46 pounds. If the water-cooled eighths mch on center, with flanges 47':! mches m
jacketing system were installed on a DH- 4B, the in- diameter.
crease in weight would be: FIGURE 11.-Air-cooled steel manifold type with
Pounds long tail pipe.
Exhaust manifold ____ ___ __ __ ___ ___ _ Non
3
e
5
. FIGURE 12.-Standard manifold type, open at front
Water_______ ____ _______ ________ ___ end, steel. "
Booster radiator_____ ___ _____ ___ ___ _ 46 FIGURE 13.-Flexible steel indivirlual stacks.
Total weight___ _______ __ _____ 82 FIGURE 14.-Air-cooled manifold t ype, aluminum.
The air-cooled, short exhaust stacks will weigh 3}.i I FIGURE 15.-Welded ~luminum ai~-cooled s~acks ..
pounds per set of 12, 10.6 inches long. If this system FIGURE 16.-0-2B airplane eqmpped with a1r-were
installed on a DH- 4B, the weight increase would cooled exhaust stacks.
be: 15. Considering all types so far tested, the individual
Pounds
2 "saxophone" stacks____ _ _ _ _ 26
12 air-cooled (sheet metal) stacks________ 39
Difference ____ _______ ________ _______ 13
air-cooled, cast aluminum exhaust stack appears to
be the most satisfactory from the standpoints of
fire hazard, weight, installation, maintenance, and
cost.
13 •
FIG.!;:5.-Standard manifold type, with bottle oficarbon-dioxide to release gas on impact
Fro. 6.-Standard manifold type, with bottle of water or carbon-tetrachloride In rear to break and flood manifold on impact
14
'
Fm. 7.-Standard manifold type, with air cooling arrangement on toil for cooling: the end
FIG. 8.-Aluminum water-cooled stack in series, with cooling system, open at front end, with long tail pipe
15
Fm. 9.-Alumlnum water-cooled stack in series with rooling system similar in design to standard manifold type
FIG. 10.-Cast aluminum stack with fins% inch on center, with flanges 4 ~ inches in diameter
76293-28--3 •
16
FIG. 11.-Air-cooled steel manifold type with long tail pipe
FIG. 12.-Standard manifold type, open at front end- steel
17
FIG. 13.-Flerible steel individual stacks
FJG. 14.-Air-cooled manifold type-aluminum
18
FIG. 15.-Welded aluminum air-cooled stacks
FIG. 16.- 0-2B airplane equipped with air-cooled exhaust stacks
19
INSPECTIONS
1. Au investigation was made of reported fires in
P- 1 and PW-8 airplanes at Selfridge Field and the
following is the report of conditions encountered:
" The particular points investigated were as fol­lows:
(a) Sources of combustible material.
(1) Leaky gasoline connections.
(2) Leaky scoop joints.
(3) Sheet metal plugs in the bottom of scoops.
(4) Location of carburetor drains.
(5) Crankcase breathers.
(6) Inflammable vapors from cooling system .
(b) Sources of sparks of flames necessary to start a fire.
(1) Spark between bare high tension terminals
and metal parts of the airplane.
(2) Vents in magnetos.
(3) Spontaneous combustion of insulation.
( 4) Exhaust stacks.
(5) Back-fires.
(c.) The possibilities of fire traveling from the engine
compartment to other parts of the plane, or
giving sufficient air to make an explosive mixture
led to special investigations of-
(1) Cowling.
(2) Fire walls.
" The possibilities of leaky gasoline connections were
found to be very great. In at least one case of fire,
it was apparently definitely proved that the source
of combustible material was a leaky uni"Ou in the
gasoline system.
" There was no particular evidence that any of the
other sources of combustible material had actually
caused a considerable fire; however, it is felt that
additional precautions should be taken in the design
of the various items to prevent any possibility of fire.
"The possibilities of sparks between bare high­tension
terminals and ground was found to be very
great. In fact, there is a probable intermittent spark­ing
between spark plugs and the altitude control rod
in every P-1 or PW-8 airplane inspected either here
or at Selfridge Field. This condition should not
exist but apparently it has persisted and trouble is
expected in the P-2 airplane with the V-1400 engine.
"It was quite evident that at least one fire was
caused by sparks from the magneto itself.
" There was no evidence of spontaneous combustion
of ignition wire insulation; however, a sample of the
cable now in use at Selfridge was obtained and com­plete
tests were conducted on it at the division.
" There was no evidence that exhaust stacks had
caused any fires; however, it is recommended that
additional precautions be taken in the design of ex­haust
stacks on all future airplanes.
"There was no evidence that back-fires had caused
any of the recent fires; however, there is considerable
evidence that at least one fire experienced by Captain
Tillinghast about two years ago was caused by back­firing,
and for this reason it is felt that additional pre­cautions
should be taken in the scoop joints and the
elimination of sheet-metal plugs in the bottom of the
scoops is recommended.
"Lieutenant Hunter's wrecked airplane was in­spected
and it is believed that the diagnosis by the
personnel of Selfridge is correct, and that the fire was
started by the disintegration of the engine.
" The results of the inspection indicated that the
following steps should be taken by the commanding
officers of stations using P- 1 or PW- 8 airplanes:
(a) Insure that all gasoline connections are gas tight
by inspection before each flight.
(b) Increase the clearance between bare high-tension
parts and ground to a minimum of three-fourths
inch. Note that in some cases it will be im­possible
to meet this requirement; however, it
should be done wherever possible.
(c) Cover spark-plug terminals with rubber nipples.
(d) Close all fire-wall openings with rubber grommets,
floating washers, or equivalent.
(e) Provide small louvres in the cowling sufficient in
size to ventilate the engine compartment suffi­ciently
to remove any accumulation of gasoline,
without formation of explosive mixture.
"A number of additional points are being referred
to the Materiel Division for further study and redesign.
In particular, a redesign of gasoline-system fittings
and an increase in clearance between high-tension
parts uninsulated and ground to a minimum of three­fourths
inch was recommended, also a definite fire­prevention
test for all new airplanes, to cover the points
mentioned above."
2. All new aircraft were subjected to inspection for
fire hazard in accordance with inspection sheets shown
on pages 20 and 21.
3. In addition, nearly all aircraft at this division
were inspected for fire hazard and definite recommen­dations
were made for the correction of discrepancies
found peculiar to each airplane. ·
Eng. Div. A. C. 6811-F-McCook Field
EQUIPMENT INSPECTION REPORT
Report No ___________ ______ __ Inspector __ _ ___ ____ ___ _______ ____ __ _______ __ - --- ---- --- - - Airplane No __ __ ___ __ ___ _____ _ ])ate __ ___ _______ _____ ______ __ MISCELLANEOUS
(g) EXHAUST STACKS:
1. T ype of engine ______ _____ ______ ___ __ ___ _____________ ___________ ___ _________ __ ___ ___ ___ ___ ___ __ 2. Number of cylinders ___ ____ ____ ________ ____ ___ ___ __ _______ ______ ____ __ __ ____ ____ __ _________ ____ _
3. Size of exhaust ports ______ ______ __ _________ ____ _____ _____ __ ______ ___ ____ ______ ___ ________ ____ __ 4. Individual or grouped ___ ___ ____ ___ _____ _______ _____ ___ _______ ____ ____ __ . ___ . _. __ ___ ___ ___ ____ __ _
5. Manifold or eparate stacks ____ __ __ _____________________ ____ _____________ _ . _. _________ __________ _
6. ~1a te ri aJ _________ __ ___________ ______ ____ ____ __ ____ __ __ _____ ________ _____ __________________ ____ 7. Length ____ _____ ______ __ _____ ______ _____________ ____ ____ ___ ______ ____ ___ __ ________ ____________ _
8. Circumference _________ __ __ ___ ___________ ___ __ ________ ____ ____ _____ ___ __ _________ __ - - - ---------
9. Gage or mat eriaL _____ ______________ _____ __ __ _____ __ _____ _________ _____ _____ __________ ___ _____ _
10. Area of cooling surface _______ __ ____ ____ ______ _____ ______ _____ __ ______ _ ·· - __ ___ ___ ____ ____ ___ ____ 11. Amount of stack under cowling ______ ______ __ ____ ______ ___ _____ ____ ___ _____ _ . _____ __ ______ ·· - ____ _
12. Amount of stacks in slipstream _____ ____ __ __ _____ ______ ______ __ _____ _____ _____ ___ __________ ______ _
13. SKETCH
14. Have these stacks been fire tested? __ ___ _____ ___ ______ _____ _____ . _ ·- ·- . ____________ _____________ _ .
15. Has this type of stack been fire tested? ___ ____ _________ ____ _____ ___ _ . _ . __ ___ _________ ___ ____ ___ __ _
16. Location of exhaust stacks in relation to gas and oil system _ _______ ______ _ . ______ ___________ _____ __ 17. Fire tested__ ____ _________ _____ 18. Accepted ___ ___ __ __ __ __ __ ___ _ 19. Rejected ___ ________ __ ____ _
20. Run engine so as to secure normal water temperature.
21. Induce all possible extra hea ting by leaning the mixture and retarding the spark. After getting the exhaust
system as hot as possible, cut gasoline supply to carburetor. As soon as motor stops, inject 1 oz. of
mineral, lubricating oil into stacks Nos. 4, 5, and 6 from front.
22. Repeat this same procedure with aviation gasoline.
23. This operation to be repeated three times with each fluid.
24. Inspect each spark plug for clearance between head of plug and parts liable to cause a ground.
(20)
21
Eng. Div. A. C. 681>-F-McCook Field
25. Is there a 3/4'' space between head of spark plug and parts liable to cause a ground connection? _____ ______ _
26. Are there any joints or connections in gas or oil lines near magneto, exhaust stacks, or spark plugs? ____ ____ 27. Are there any solid connections in oil or gas lines ahead of fire wall? __ _____ __ __ ____ ____ _____ __ _____ __ _
28. Are any gas or oil lines above or dangerously near ignition units or high-tension connections? __ ___________ _
29. Are openings in fire wall excessive in size?_ ________ _____ ___________ __________ ___ ______ ______ __ __ __ _
30. Is ignition wire according to specifications? ____ ___ _____ _________________________________________ ___ _
31. Are vent lines secured; with their outlets 4" outside of fuselage or cowling? ___________________________ _
32. Are holes in cowling excessive in size for exh11-ust stacks?_ __ ___ ____ __ _________ ___ ___________ ________ _ 33. Is the distance from end of exhaust stacks to cowling or fuselage less than 4"'? _________________________ _
34. Has engine cowling proper openings for ventilation? ______ __ _____ ___ __ ______ ____ _______ ____________ _ 35. Has air scoop manifold any recesses or plugged openings which might hold gasoline?_ __________________ _
36. Are high-tension wire safetied? ___ __ _____________________________ ___________________ - - - - - - - - - -- - - -
37. Is safety appliance insulated? ____ _ - -- -- _____ ___ _____ _______ ___________________ __ ___ - __ _ - - - _ - - - - - -
38. Are heads of spark plugs covered with rubber protectors? _________________________ ________ _____ ____ _ 22
PHOTOGRAPHS
1. As previously noted, photographs were taken of
every airplane crashed. Still pictures were taken of
the a irplanes before the crash, as a record of the
equipment installed and the type of craft. Slow­speed
motion pictures were taken on one side of the
crash and normal-speed motion pictures on the other.
Still pictures were also taken of the airplane at the
moment of impact and after the crash, to show the
condition of the engine, manifolds, gas tank, etc.
2. The photographs (figs. 17 to 32, inclusive) shown
on the following pages illustrate some typical crash
condit ions and give a better idea of the problem.
23
•
FIG. 17.-Crasb of USD-9A airplane with Liberty engine. (See also pp. 24 and 2.;)
24
•
F10. 18.-Crasb of USD-9A airplane with Liberty engine. (See also pp. 23 and 25)
25
I
Fm. 19.-Crash of USD-9A airplane with Liberty engine. (See also pp. 23 and 24)
26
FJG. 20.-Crasb of DH-4B airplane, March 12, 1925. (See also pp. 27 and 28)
27
FIG. 21.-Crash of DH-4B airplane, March 12, 1925. (See also pp. 26 and 28)
28
F10. 22.-Crash of DH-4B airplane, March 12, 1926. (See also pp. 26 and 'Zl)
29
FIG. 23.- Crash of XB-IA airplane, April 3, 1925. (See also p. 30)
30
FIG. 24.-Crash of XB-lA airplane, April 3, 1925. (See also p. 29)
31
FIG. 25.- DH-4 airplane ready for crash
FIG. 26.-Crash or DB-4 airplane with air-cooled stacks
•
32
FIG. 27.-0rssh or DH-4 airplane with air-cooled stacks
El<l-28.-0rash of DH-4 airplane with standard saxophone stacks-fire
•
33
Flo. 29.-DH-4_alrplane after crash-straight, steel exhaust stacks
•
FIG. 30.-Typical crash impact before ramp was installed
34
FIG. 31.-Typ!cal crash fire
FIG. 32.-Typical crash impact after ramp was installed. Note gas vapor and steam. No fire
0