Subject: Bell Airacuda  (YFM-1)
From: erikavg@ix.netcom.com(Erik Shilling)
Date: Jul 24 1996
Newsgroups: rec.aviation.military

      Another airplane I flew was the YFM-1 Airacuda, made by Bell
Aircraft Corporation in Buffalo, New York.  It was a pusher built
around two exhaust-driven turbo-charged Allison engines of 1040
horsepower each.  It was new in type and concept.  The design's
hypothesis was that it would be used as a bomber-destroyer.  It had two
thirty-seven millimeter cannons, one in the nose of each nacelle, but
little in the way of defensive weapons.  Several other innovations were
being explored on the Airacuda that were not used on any previous
military airplanes.  Because some of the innovations were impractical,
they haven't been used since. 

      Flying the Bell Airacuda was a new experience for me, since it
was the first pusher aircraft I'd ever flown.  Its handling
characteristics were foreign to anything I had ever had my hands on.
Under power it was unstable in pitch, but stable with power off.  While
flying straight and level, if a correction in pitch was required, a
forward push on the control resulted in the airplane wanting to pitch
over even more.  Pitch control became a matter of continually jockeying
the controls, however slightly, even when the aircraft was in proper
trim.  The same applied if pulling back on the control.  It would tend
to continue pitching up, requiring an immediate corrective response.
The same happened in a turn.  With power off, the Bell became stable in
pitch.  This was fortunate because during approach and landing, it
was very stable, and a nice flying airplane.  

      It was built around several new ideas never tried before, and was
unlike any other fighters up to that time.  First, it wasn't designed
to be a fighter plane, although many had the mistaken idea that it
was.  It could be better described as a bomber destroyer.  The
tactics suggested by its designer were based upon the machine being
used as a flying antiaircraft platform.  It was a defensive weapon to
be used only against incoming bombers that were beyond the range of
escorting fighters.  Although it had some defensive weapons, I think
they were more psychological in nature, for the benefit of the YFM-1
crew, than practical.  

      The tactics envisioned were that the Airacuda would fly in trail,
just out of range of the enemy bomber formation's guns.  Up to that
time bombers had 30 and 50 caliber weapons.  It is important for the
reader to keep in mind that the Bell would be used only against enemy
bomber formations that were out of range of protective fighter escort.
The YFM-1 had little or no effective firepower for its defense, and
as a consequence, would be a sitting duck against agile fighters.  The
front of each engine nacelle housed a 37 mm, gyro-stabilized cannon.
With the longer range of the 37 mm guns, they could pluck the enemy
bombers off, one by one.  In other words, it was a mobile antiaircraft
gun platform.

      The primary function of the men in the nacelles was loading the
guns, although they could be fired by the gun crew in an emergency.
Initially, the pilot of the plane aimed the airplane in the general
direction of the formation.  Further correction in aim would then be
made by the gun control officer, and fired by him.  His station was
directly behind the pilot, using an inverted periscope that came out
through the belly of the ship to aim the guns.  The fire control
officer would clutch the guns into the gyros, which stabilized them.
From that moment on they would stay on target.  The person operating
the guns could then make any further correction and fire away until the
bomber was brought down.  His position had swing-out flight controls,
and in an emergency he could fly the airplane.  If it was necessary to
abandon the aircraft, the pilot would have to feather both engines to
prevent the propellers from chewing the men to pieces, especially those
in the nacelles.  The flight manual said they would feather in six
seconds; that's a long time in my book.

      In addition to being a pusher airplane, the YFM-1 also had other
unusual features.  It had only one engine-driven accessory, an emergency
fifty-ampere generator on the left engine.  The Bell Airacuda was an
electrical nightmare.  All normally driven engine accessories, such as
fuel pumps, hydraulic pumps, vacuum pump, and the gyros stabilizing the
guns were electrically driven.  Because of all the electrical energy
required, the ship had to have a full-time auxiliary power unit.  The
auxiliary power unit was driven by a powerful four-cylinder gasoline
engine which ran all the equipment.  Since the aircraft was required to
operate at high altitudes, the APU also had to be turbo-supercharged.
To do this, a dual bleed came from the same exhaust turbo-chargers that
super-charged the Allison engines.  The power unit was the weak link in
the system.

      Changing fuel tanks was simple.  There was no fuel selector as we
normally think of one.  Each fuel tank had its own fuel pump.  Tanks
were changed by flipping the switch on for the electric fuel pump of
the desired tank.  The gear and flap selector was similar in appearance
to the C-47's fuel selector.  Gear and flaps were activated by rotating
this control to the appropriate position.  It only had three
positions--takeoff, fly and land--and could be turned only in a clock-
wise direction.  In the takeoff position, the flaps were retracted.  In
the fly position, the gear was retracted, and in the land position,
both gear and flaps came down.  The flaps immediately followed the
gear.  Unfortunately the two were not isolated from each other, and
that posed a minor problem.  

      To get gear only, such as on downwind, the pilot would watch the
gear as it extended.  When almost all the way down, he tripped the
circuit breaker.  Then on final, when the flaps were required, the
breaker was turned back on.  At the completion of the landing roll, the
pilot would select fly position, retracting the flaps.  

      The engines had no cooling fans, so in summer the airplanes had
to be towed to the takeoff position before starting.  As soon as there
was an indication of an oil temperature rise, the pilot immediately
started the takeoff run.  When landing, if the oil temperature was on
the high side, the pilot would have to shut the engines down and have
the ship towed to the parking area.  If the airplane had only a short
distance to taxi, it could continue to its parking place under its own
power.  

      One recurring problem experienced by pilots flying the Airacudas
was that the auxiliary power unit would all too frequently stall or
quit.  The reverse current relay would stick and motorized the
generator.  Since this would drain most of the current from the
battery, all electrical systems became inoperative: NO fuel pressure,
NO vacuum, NO hydraulic pressure, NO gear, NO flaps and NO ENGINES.
The first time I lost both engines, I was in the landing pattern on
base leg just about to turn final when the APU quit, then a second
later so did both Allison engines.  

      Fortunately, it occurred right after the gear locked down, and I
was able to make the runway without power.  Although the airplane had a
wobble pump, the handle was only four inches long.  It was impossible
to supply two Allison engines with the wobble pump, since they consumed
over three hundred gallons of fuel per hour at full power.  Its only
purpose was to start the engines.  

      The second time the problem occurred, I was flying on
instruments, but again I was fortunate.  They both quit not too long
after I had started into the overcast.  I knew there was a couple
thousand foot ceiling under the cloud base, so I dove out of the cloud
before the gyros tumbled.  All the while, the crew chief was trying to
restart the APU, which started with room to spare.  With the APU going,
the fuel pumps came on and both Allison engines began producing power.
The remainder of the trip to Langley was uneventful and I made a safe
landing there.  

Regards,

Erik Shilling
-- 
Erik Shilling		Author; Destiny: A Flying Tiger's 
Flight Leader              Rendezvous With Fate.
3rd Squadron AVG
Flying Tigers