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Why didn't Allison work harder on developing it?
Hard to believe because the V-1710 seemed to be more reliable and easier to build than the Merlin. I'm beginning to think that the Allison got a really bad rap.
There was a lot to improve on V-1710, a much more important engine than the V-3420.
Merlin was probably more reliable.
V-1710 was a decent engine, Merlin was far better.
Merlin have had better altitude performance from day one.I seriously doubt it was far better overall, but it definitely had better altitude performance once the 2-stage supercharger was fitted to the 60-series and later engines.
Pick a late-war V-1710 and compare it with a late-war Merlin.Late-war Allisons were everything the Merlin was and more. During the hard-hitting years of 1943 - 1944, and even into 1945, the Merlin was better-suited to the ETO environment.
It certainly didn't run as long as a V-1710 before needing overhaul, but longevity doesn't win fights. Performance does.
As far as the V-3420, the propulsion system on the XB-42 was a coaxial system, meaning one engine drove one propeller, the other engine drove the other propeller. This allowed independent control of the Curtiss Electric propellers including feathering on both and reverse on the aft propeller. Those functionaliity would have been lost on a V-3420 powered XB-42. XB-42 Props
The Allison W-3420 had potential. to be sure, and four were fitted to a B-29.
View attachment 693509
It was faster than the normal R-3350 version, but would have also interrupted production. You'd think they could have anticipated that had it been adopted, it would have interrupted production since they declined to improve the F6F-5's rolling characteristics for the exact same reason ... it would have interrupted production.
They also tried an Allison-powered B-17, though they were V-1710s rather than W-3420s.
View attachment 693510
It was also faster than the radial-powered variety but, are you ready for it, it would have interrupted production! Go figure, huh?
Merlin have had better altitude performance from day one.
Pick a late-war V-1710 and compare it with a late-war Merlin.
1944 and 1945 were the late-war years, Merlin proving itself time and again in the MTO, Eastern Front and Asia/Pacific, too.
Agreed pretty much.
The V-3420 installation was to be an engine module that bolted up to the airframe. That is, they unbolt the R3350 engine module and bolt up the V-3420 module. The engine module contained the engine, radiator, turbos, coolers, etc.
No (major) airframe mods were necessary, though there may have bene some controls that needed changing.
The XB-38 had radiators installed in the leading edge between the nacelles. The chin scoop fed an intercooler, replacing the one in the wing on the regular B-17. The turbo was in the same place.
The XB-39 would not have interrupted B-29 production much. But V-3420 production was virtually non-existent, the engine modules were not in production and Fisher, who developed the engine module, were mucking around with the XP-75. The XB-39 only had its first flight in December 1944, by which time the B-29 was in service. Production probably would not have made the war (due to engine availability).
Had the XB-39 flown in December 1943 I would think that its added performance (at the cost of some range) would warrant production.
The XB-38 did require more extensive modifications to the airframe, but this could have been avoided by putting the radiators in the nacelles. The performance gain over the regular B-17 was not that great, and not worth the effort. Later, higher performance V-1710s would have stretched the advantage over the regular B-17,
Changing to the XB-38 would have cost some production, so probably a wise choice to abandon it.
By a tiny bit, yes. They were about even as single-stage units, with the Allison giving slightly better performance lower and the Merlin slightly better performance up higher by maybe 2,000 feet or so.
The Merlin's performance was great, all the time during the war. In the 60-series, it topped out at about 1,710 hp @ 3,000 rpm @ 6,400 feet (Merlin 38 / 69 as fitted to P-51 B/C and D/K). The post-war Merlin 130/131 topped out at about 2,070 hp @ 3,000 rpm. At 25,000 feet, the 2-stage Merlin was about 1,300 hp or so.
The V-1710 lagged a bit behind for a good bit of the war. But, a representative unit would be the V-1710-89/91 as flown in the P-38J. It made 1,600 hp @ 3,000 RPM @ 10,000 feet and 1,425 HP @ 3,000 @ 24,900feet. Not much to choose, really, once the issues were worked out, as they were by early 1944.
The late-war V-1710-127 made 2,950hp @ 3,000 rpm @ 11,000 feet, which was 400+ hp more than any flying wartime Merlin made. It didn't make the war, but was running and ready if needed.
I've seen some estimates that would give the B-38 Fortress about 1000 more miles range at the cost of a slightly lower operating ceiling. That would make it a very attractive option in the early Pacific campaigns where the B-24 was proving to be a "dog," a very difficult aircraft to operate and maintain. If the B-38 eventually proved successful and had range equal or better than the "difficult" B-24, the B-24 could be cancelled. Production prior to the B-29 could be focused on B-17 and B-38s, with different factories assembling the two variants. Those already turning out standard B-17s, mostly for Europe, would continue. B-24 factories would convert to the B-38, until production of the B-29 was ready.The V-3420 installation was to be an engine module that bolted up to the airframe. That is, they unbolt the R3350 engine module and bolt up the V-3420 module. The engine module contained the engine, radiator, turbos, coolers, etc.
No (major) airframe mods were necessary, though there may have bene some controls that needed changing.
The XB-38 had radiators installed in the leading edge between the nacelles. The chin scoop fed an intercooler, replacing the one in the wing on the regular B-17. The turbo was in the same place.
The XB-39 would not have interrupted B-29 production much. But V-3420 production was virtually non-existent, the engine modules were not in production and Fisher, who developed the engine module, were mucking around with the XP-75. The XB-39 only had its first flight in December 1944, by which time the B-29 was in service. Production probably would not have made the war (due to engine availability).
Had the XB-39 flown in December 1943 I would think that its added performance (at the cost of some range) would warrant production.
The XB-38 did require more extensive modifications to the airframe, but this could have been avoided by putting the radiators in the nacelles. The performance gain over the regular B-17 was not that great, and not worth the effort. Later, higher performance V-1710s would have stretched the advantage over the regular B-17,
Changing to the XB-38 would have cost some production, so probably a wise choice to abandon it.
I've seen estimates that both were not only faster, but had a range advantage too (over the "standard" B-29 and B-17.The Allison W-3420 had potential. to be sure, and four were fitted to a B-29.
View attachment 693509
It was faster than the normal R-3350 version, but would have also interrupted production. You'd think they could have anticipated that had it been adopted, it would have interrupted production since they declined to improve the F6F-5's rolling characteristics for the exact same reason ... it would have interrupted production.
They also tried an Allison-powered B-17, though they were V-1710s rather than W-3420s.
View attachment 693510
It was also faster than the radial-powered variety but, are you ready for it, it would have interrupted production! Go figure, huh?
By a tiny bit, yes. They were about even as single-stage units, with the Allison giving slightly better performance lower and the Merlin slightly better performance up higher by maybe 2,000 feet or so.
The V-1710 lagged a bit behind for a good bit of the war. But, a representative unit would be the V-1710-89/91 as flown in the P-38J. It made 1,600 hp @ 3,000 RPM @ 10,000 feet and 1,425 HP @ 3,000 @ 24,900feet. Not much to choose, really, once the issues were worked out, as they were by early 1944.
The late-war V-1710-127 made 2,950hp @ 3,000 rpm @ 11,000 feet, which was 400+ hp more than any flying wartime Merlin made. It didn't make the war, but was running and ready if needed.