YFM-1 Airacuda

ThomasP said:

Although not in any official original documents, I remember reading (a long time ago) about the idea behind the Airacuda. Whatever article or book I read it in stated that the Airacuda was not originally intended to defend the continental US from foreign bombers, but to be a long range escort for the B-17. The soon-to-be B-17 was thought to be capable of attacking out to 1000 miles away, and a suitable escort was needed.

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This design kind of was based on several concepts and, there were ideas for bomber-escorts, but the problem was meeting the goal period, and doing it with all the needless requirements saddled onto the design.

Basic Requirements

• Have good speed, acceleration and climb.
• Be maneuverable, and be able to tolerate large g-loads
• Possess adequate firepower for the task.

The problems were that, while power-to-weight ratios favored the small, and fuel-fraction was more important than the actual mass of fuel: Volume favors the large, and the structure has to be able to carry a suitable amount of fuel, while being light & strong enough to maneuver and accelerate quickly.

The other problems had to do with the fact that fighter operations tend to involve a lot more time at high power-settings, and a lot of maneuvering, so the combat range and ferry range are substantially different from each other: While the bomber's combat-range was 80% the ferry-range; the fighters was usually about 40-67%. This problem was further exacerbated by the fact that fighters often naturally cruised faster than bombers and, to be tactically usable, it was preferable to cruise faster than the maximum-range cruise.

The speed wasn't too negotiable, so the solution was how to handle the speed difference: One solution was to fly over the bombers, using an S-weave. The curved flight-path resulted in a longer flight-path relative to the bomber, which would make the required range even further than it would if they simply flew in a straight-line; the other option was a convoy arrangement where the bombers would fly at their own pace, while the fighters are timed to rendezvous near the target, surge ahead, and clear out the way of enemy fighters. This favored the difference between the speed of the two aircraft, but would be more spaced out to close-escort.

The range issue could be partially fixed by the fact that they could use two waves of fighters to cover the bombers on the way in and out, and potentially a third to cover them over the target, but the range problem was still very serious.

Needless Requirements

• Rear Gunner: Desired so the plane can augment the bomber's defensive firepower. There were also some fighter guys who thought it could be useful to defeat the Lufbury circle. The fighter guys did seem to be keen on the idea of having long-ranges to do diving attacks on the enemy's rear (I'm not sure if this meant dive-bombing, or merely strafing), which might have been aimed at encompassing the attack role (something the bomber guys probably would have appreciated, since attack was low on the rung).
• Range must be achieved on Internal Fuel: They were opposed to ferry tanks because they would provide a source of drag even after all fuel was exhausted; they were opposed to drop-tanks because pilots would drop them at the start of combat to lighten the plane up and, in doing so, sacrifice all the range benefits that came with it.

The drop-tank issue was probably greatly overblown since, provided they were used from the point where a positive rate of climb was established to cruise altitude and speed, a considerable amount of fuel would be expended and, even if they were jettisoned right then: One would still have an airplane at cruise and speed with nearly full internal fuel.

The rear-gun idea was quickly seen as useless with the Berliner Joyce P-16/PB-1 (the gunner would often be pinned under g-load): The idea still was pursued again with the P-24 (which crashed before this problem could be tested out), and it's developed form, the P-30/PB-2 where it was found the gunner would sometimes black-out under g-load.

The fighter guys and bomber guys were often at each others throats and, since both felt they were right: None would listen to the other even when they made valid points. Unsurprisingly, with the bomber guys ruling the roost, they typically got their way. They decided the problem wasn't that they needed to ditch the second crew-member who took up excessive space and weight, and hang drop-tanks, but to use a multi-engined aircraft instead.

Initially, they proposed a modified Martin B-10 series aircraft with a strengthened fuselage, no-bombs, forward mounted guns, and additional gunners to help protect the bombers. It was found to have likely been slower than the B-10 it was to escort. Claire Chennault pointed out the absurdity of trying to produce a plane as large as a bomber that would be faster than a bomber. While they realized the modified B-10 was a bad idea, they still felt the basic idea was valid.

Well, prior to WWII a common belief was that, "Dogfighting at speeds over 300 MPH will be impossible because you'd be moving as fast as human nerve impulses do."

And note that the Boltan Paul Defiant was build around the same idea as the Airacuda. Engaging bombers would be more like naval engagements than the WWII Scout Versus Observation Plane. The interceptors would stand off and fire away. In fact just about every nation except the US conceived and built multi-seat day fighters, all of which proved to be woefully inadequate when facing even relatively pedestrian single seat fighters. The rear gunner was not just there to tell the pilot they had a bad guy in their six, he was expected to fight, too.

Capt "Winkel" Brown described his first good look at a BF-110. He was in a flight of Hawker Hart light bombers being used as trainers at the time of the BoB and a BF-110 suddenly pulled up along side and the rear gunner blew away one of the Harts. In reality I suspect that the rear gunner very rarely got to perform in the attack role; he probably was trying to keep from throwing up.

The P-61 was designed as a night fighter but it clearly was influenced by the "Convoy Fighter" concept. On the other hand they made it incredibly maneuverable. It was not until recently that I realized that both the Gunner and the Radar Operator seats on the P-61 were designed to swivel in synchronization with the top turret.