YFM-1 Airacuda
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MIflyer
1st Lieutenant
Well, for the K-14, the main issue was rate of turn so for that one they did use a rate gyro. But that one you did not move around; it was fixed.
For tracking, using moveable gunsights, it was a different situation:
airandspace.si.edu
For tracking, using moveable gunsights, it was a different situation:
Defending the Superbomber: The B-29’s Central Fire Control System
Aeronautics curator Christophere Moore explores one important advancement on the B-29 Superfortress: its central fire control system.
SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
I do believe the voice of our gunner is Mel Blanc.
- Thread starter
- #24
I'd have figured the two purposes of a gyro-sight would be to compute lead.
MIflyer
1st Lieutenant
The K-14 had to know the rate of turn to compute lead, and the rate gyro supplied that info.
I read that late in the war our pilots were told it was Okay to tell the Japanese "secrets" in order to avoid torture; it was not going to affect the war in any case. A P-51 pilot that came down in Japan told them that the new K-14 gunsight did not always work well in (Left?) turns. Soon thereafter P-51's encountered some Japanese fighters that for some reason broke into Left turns. But those Mustangs had not been equipped with the K-14 yet and blew the hell out of those fighters.
I read that late in the war our pilots were told it was Okay to tell the Japanese "secrets" in order to avoid torture; it was not going to affect the war in any case. A P-51 pilot that came down in Japan told them that the new K-14 gunsight did not always work well in (Left?) turns. Soon thereafter P-51's encountered some Japanese fighters that for some reason broke into Left turns. But those Mustangs had not been equipped with the K-14 yet and blew the hell out of those fighters.
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- Thread starter
- #26
So, this gyroscopic system just calculated for barrel elevation?
Note: Edited for misunderstanding.
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MiTasol
1st Lieutenant
Somewhere in my book collection is a book on RAF guns from WW2 and the Ministry of Aircraft Production had the same problems with loading machine gun belts until some bright spark realized that H&O Wills had machines that stacked damage free fragile cigarettes into soft packets and contracted them to solve the problem. This was done within a few (relative) days.
SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
Hey, that's one for us smokers!
MIflyer
1st Lieutenant
The Indians disliked the limited gun armament of the Mig-21 (two and usually only one 30MM gun) and devised a way to take a dual 23MM pack, normally carried as an external store, and bolt it against the belly (not on a pylon), the belt feed for the cannons wrapping around the inside of the airplane's skin. The Soviets liked it so much they copied it.
Back in the day, when the equivalent of this site on usenet was rec.aviation.mil we were privileged to get posts from Erik Schilling, pre-war test pilot and Flying Tiger. He flew the Airacuda, and this is what he recorded about it.
ubject: Bell Airacuda (YFM-1)
From: [email protected](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
ubject: Bell Airacuda (YFM-1)
From: [email protected](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
MIflyer
1st Lieutenant
In other words the Airacuda was built using the same assumptions as that savior of the BoB, Defiant turret fighter.
MiTasol
1st Lieutenant
I think the Defiant was a far better concept - at least the pilot could point the turret forward and use it for repelling head on attacks and it did not have a critical system like the APU.
SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
The Defiant really was a well built airplane built to a flawed spec. Would there have been a problem with the guns firing through the propeller if the guns pointed forward? There must have been some consideration.
MiTasol
1st Lieutenant
The flight manual is somewhere here on the forum and allows the pilot to fire it forward. I think the bullets pass above the propeller arc
Angled 12 o'clock high. Sort of like Schrage Musik.
MIflyer
1st Lieutenant
The Me-410 with the 50MM cannon was basically conceived long the same lines as the Airacuda. Adoplh Galand said that while the cannon had the range to hit the American bombers outside the range of their machine guns, they could not hit anything that far out. At a range where they could hit something they were within the range of the .50 cal. And just about any maneuvering resulted in the gun jamming. When P-51's and P-47's showed up, the jig was up.
- Thread starter
- #37
Regarding the YFM-1's 37mm feed mechanism
Regarding the YFM-1 as a whole
The idea wasn't just confined to us interestingly (the French & Germans also thought of similar ideas).
For the most part, the gyro description seemed similar to the B-29's system interestingly except a few years earlier. The arrangement appeared to make single-man operation impossible because of the periscopic system's details. That said, it is getting quite close to a workable concept that would appear on the XP-54 (it had a lead-computing sight with 0.50's that could vary in elevation and convergence that could be corrected solely by the pilot).
So, the problem would have been not just hypothetical/theoretical but practical knowledge to make it work with both the particular gun and aircraft installation?
Two questionsMiTasol said:
- Was this problem with loading on the ground or in the air? I ask because the gunners on the YFM-1 were there apparently, to load the guns in the air.
- Would you say the RAF had this problem sorted out better or worse than us?
Actually, James Doohan lived to play Scotty in Star Trek largely because he smoked: His lighter stopped a bullet that would have otherwise killed him. Interestingly, it might have accounted for why he ended up with both Parkinson's and Alzheimer's disease (there had been a claim made allegedly that smoking prevented Alzheimers, but it was only because it killed smokers usually before they got old enough to develop it. For those who actually managed to escape lung-cancer, the incidence was higher).
Regarding the YFM-1 as a whole
How did the old usenet system work? How did people find the groups they wanted?
Does that have to do with the pusher prop?
The 2 x 37mm cannon definitely served this purpose (the aircraft was also able to drop bombs on formations of aircraft), but the defensive weapons seemed to be based on the escort fighter mission: There was a pervasive idea that escort fighters should have turrets so they could act like a flying turret primarily to augment the bomber's defensive gunners. It seemed the idea was that it could rove across the formation and add firepower when needed predominantly, and if that failed, simply chase after them and shoot them out of the sky with the traditional forward mounted guns.
The idea wasn't just confined to us interestingly (the French & Germans also thought of similar ideas).
While I'm not sure how reliable the feed mechanism was with the specified ammunition capacity: The idea of having the gunners able to operate the guns in an emergency seemed like something that would be useful on a boat or ship, but not an aircraft where weight and space are at a premium.
When he said "clutch the guns into the gyros" was he talking about the artificial horizon gyro, or simply to the fire-control system's gyros?
For the most part, the gyro description seemed similar to the B-29's system interestingly except a few years earlier. The arrangement appeared to make single-man operation impossible because of the periscopic system's details. That said, it is getting quite close to a workable concept that would appear on the XP-54 (it had a lead-computing sight with 0.50's that could vary in elevation and convergence that could be corrected solely by the pilot).
Most hydraulics are driven by pumps that are mechanically driven off the engine right?
Doesn't sound very "auxiliary".
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MIflyer
1st Lieutenant
" all electrical systems became inoperative: NO fuel pressure, NO vacuum, NO hydraulic pressure, NO gear, NO flaps and NO ENGINES."
With a relative few exceptions aircraft engines are not dependent on the electrical system.
With a relative few exceptions aircraft engines are not dependent on the electrical system.
MiTasol
1st Lieutenant
Mainly in the creation of feed belts initially (the previous method was manual with a press producing about a foot at a time with lots of dud belts) but they also built powered feed mechanisms to drag long lines of ammo long distances from some turret ammo boxes.
- Thread starter
- #40
