Evening star., 1942-11-11
Accuracy Of Bombing
AtGreai neighfMak
'Forts' Formidable
Years Of Experiment
Needed to Reach
35,OO0-Foot Ceiling
BY WILLIAM F. BONI,

ny WILLIAM F. BONl.
Associated Press Military Editor.
SEATTLE, Nov. II P.-One o.
the things that makes. the Flyine
FORTRESS such headache to Jap anc
Nazi alike is its ability to bomb with
deadly effect from high attitudes.
The accuracy Of the bomb sight
has something to do with that, o1
course, but first the Flying Fortress
mad to get up to those high attitudes
SO this Is the story of how it got
there.
Even the original Boeing 299, fore
runner of the present-day Fortresses
was an exceptional high altitude
ship. 1t could go to 27,OOO feet and
1t and its Immediate successors, the
early Bits and B-17A's, enabled
Army Air Corps pilots to smash one
international record after another
Tor altitude with load and speed
with load.
Used Turbo- Superchargers.
The B-l7A was the first to use
turbo-superchargers which, driven
by the exhaust gases, feed COM
pressed air into the motors in the
upper reaches where the air is thin
1t was an installation that cost
Boeing and the Army many head
aches, for until then turbos had
been installed successfully only in
single-motored aircraft.
TN addition to its order for 13
Of the first Bits" explains Well
wood Beall, Boeing's chief engineer
the Army ordered one extra plane
as what is known as static test
article Finally, though, Gen.
Echols (Maj. Gen. o. P. Echols)
chief of the materiel center at
Wright Field, told us to go ahead
and fly that plane, using it as a
test model for the turbo-super-
chargers"
The turbos first were installed on
top of the engine nacelles. But
they caused so much buffeting on
the first flight that it wasn't deemed
safe even to try them there again.
The turbos were shifted to the un-
derside of the nacelles.
The job of finding out the causes
of the turbos' failure at extreme al
titudes went to Eddie Allen, a genial
wizard who carries the burdensome
title of director of the flight and
aerodynamics DIVISION" and his
staff. About year ago, they found
the answer and today, at peak alti-
tude, the four motors still deliver
the full rated military power.
Cold Complicates Problem.
At those extreme attitudes, where
rubber tail wheels have been shat
tered by machine-gun fire because
they were frozen solid, oil and other
lubricants also froze, the controls
froze. the propellers stopped or
ran away. (Today, at $4,000 feet,
the props can be feathered-impor-
tant not only in case engine trouble
should develop at that height, but
also because it means that now
props can be feathered at ground
temperatures of so degrees below
EeroD
Sparkplugs are,=at the moment,
the "bottleneck" OF substratosphsre
flying, Mr.. Allen explains. That is
because, in those high reaches, there
are SO many peculiar electrical
manifestations -,44p > =, ..
Human ability to perform up 70
standard is another difficulty, one
which the Boeing pilots are helping
to solve for the Army.
They have their own strato cham
ber Gust as Lockheed has for its
pilots who fly the high-climbing
P-38). Before a flight to $4,000
feet or beyond, the engineering
crews must don full equipment, in
cluding pressurized suits and oxy-
gen masks and, while breathing in
oxygen, must exercise for As min
utes. In that way nitrogen is driv-
en- out of the bloodstream. for it is
the nitrogen reaction in the blood
that create ero-embolism, to altl-
tude flyers what "the bends are to
deep-sea divers.
Cruising Details Worked Out.
Mr.. Aliens department also has
worked out detailed cruising and
performance charts, from which a
ferrying pilot of the Army Air
Forces air transport command can
figure out almost to the gallon the
amount of fuel it will require to fly
4 Fortress from San Francisco to
Hawaii under the prevailing con-
ditions of weather, load, cruising
speed, etc.-and even can tell how
far he can get in case one or even
two engines should conk out.
The engineering test flights con-
tinue all the time. At present Eddie
Allen and his staff have three
planes turned back to them by the
AAF for just that purpose.
One plane is used purely for lg-
milton tests at $4,000 feet and high
er, tests which may result in stand
ard installations in all AAF high
altitude planes. The other two are
reserved for performance tests on
Army y-requested equipment and in
stallationS.