Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: CMC Airboss on January 17, 2006, 01:28:18 PM
-
I was reading a book on the P-40 that discussed the replacement of the Allison with Merlin engines in the F model. That led me to wonder: Were Rolls Royce/Packard Merlins ever installed in the P-38 Lightning?
MiG
-
Did they ever make a left turning Merlin?
-
oooohhhh, dont we wish they did.
Warren Bodie, who wrote pretty much the definitive P-38 book (IMHO) made a major lament over this very issue. He had extensive access to Lockheed's and the giovernment's archives in researching his book, and as I remember he said there apparently wasnt any reason this didnt get tried. Maybe nobody thought about it...
Its also possible that the production boards jsut wanted allison to have a place to pu ttheir engines. In the 30s, it was common military practice to divide up orders and even subcontracts to keep as many companies solvent as possible with the tight budgets around. In the 30s, 50 airplanes was a big order...I'm not kidding. So, i wonder if this "keep our options open" thinking didnt just carry over to this situation. It may also be that (without the benefit of hindsight) the planning boards werent sure they'd get enough merlins to fill all needs, so they didnt want to add another airframe to list of ones waiting for the engine.
The performance of a Merlin engined turbocharged lightning would be....impressive.
-
AFAIK actuall installation never happened; there were plans by Lockheed and also RR got one plane for conversion but nothing materialized.
gripen
-
Check the 38Q thread just down the board from this one. Widewing explains it all pretty well.
-
Originally posted by Debonair
Did they ever make a left turning Merlin?
The Mosquito B.Mk XVI was powered by a Merlin 72 and 73 or Merlin 76 and 77 "handed" engines, so yes, there were left turning Merlins.
-
Lockheed actually researched the installation of the Merlin XX. They made a proposal to the AAF in 1940 that included a detailed analytical study.
Unfortunately, the AAF was not interested in using British engines and GM began howling immediately (they owned Allison).
The net result is no P-38s ever were modified or flown with a Merlin engine installation.
My regards,
Widewing
-
And what a shame it was , during a demonstration tour , Tony LeVier ( a lockheed test pilot) got caught in some bad weather and set down his p-38j by mistake at a field operated by the rolls-royce experimental group. Talk about irony. I read this in Warren Bodie's book " The Lockheed P-38 Lightning" Which IMHO is a must read for any 38 fan .
38
-
In '42 and '43 the possibility of replacing the F-5 and F-10 in the P-38E, F and G with a XX series 2-speed/single-stage Merlin, ie the V-1650-1, would have been attractive. The Allisons were not cleared to run at emergency powers of 1325 hp, and in the AFDU tests they weren't even being run at 1150 hp mil power. Eventually the Allisons were cleared on sort of a sliding scale of power ratings that put them ahead of the Merlin XX series depending on altitude. But for quite some time the Merlin XX would have offered better performance at lower altitudes, and roughly equivalent performance at higher (25,000 ft) altitudes. Except, the Allison was roughly 30-35% more fuel efficient than contemporary Merlins. 11% higher compression ratio and the exhaust driven turbos compressing the charge made a big difference in fuel economy. So you would have seen a substantial decrease in range compared to Allison engined Lightnings.
By the time the 2-speed/2-stage V-1650-3/7 would have been available the F-17/B-33 combo was also available for the P-38J. And there wouldn't have been much if any advantage for the Merlin over that Allison/turbo combination. The F-17/B-33 put out more power at ALL altitudes than the -3 could manage, and the -7 only had a very slight 100-120 hp or so advantage in the 5000-7000 ft range, other than that the F-17/B-33 outperformed it at all altitudes. Lockheed had some performance estimates showing the Merlin giving slight speed improvements at altitude, but that is probably more due to the higher reduction gear ratio and lower prop tip speed than any superiority of the Merlin. And Lockheed based their calculations on using the original engine cowlings without the draggier beard radiators the -J/L used, I don't know if they appreciated the fact that even the aftercooled Merlins would have required more heat exchanger capacity than the B-33 intercooler used. I suspect in practice they would have had to go with the beard radiator as well, and there wouldn't have been any drag advantage for the Merlin engined aircraft. And again, the Merlin is going to decrease the aircraft range by 30%+ due to the Allison's better fuel economy. All in all not a real attractive change, especially compared to the K which could have been available at the same time.
Greg Shaw
-
Hi Greg,
Great analysis! :-) Let me add that the Merlin would have come out a bit better at high speed than shaft power comparisons suggest because it produced a substantial amount of exhaust thrust.
However, the Allisons seem to have been a good choice for an aircraft which was designed with the turbosuperchargers in mind, and I agree that there would have been no clear case for perferring the V-1650 over the V-1710 as P-38 powerplant.
Inspired by your comment on fuel economy: Do you think it would have been possible to equip the P-51 with a turbo-supercharged Allison? The V-1710 was its original powerplant, after all ...
Regards,
Henning (HoHun)
-
imagine the speeds a merlin lightning could have done lol, would have been the nemesis of all german fighter pilots. would have probably been one of the fastest fighters around for a while too!
well, international cooperation for you:)
-
Very interesting Greg.
Thanks for sharing it.
All the best,
Crumpp
-
Compressibility in level flight could have been a real problem
-
Hm... at least Allison had lot of faith on their two stage mechanically supercharged V-1710s and the P-38. They considered to replace turbo charged V-1710s of the P-38 with the V-1710-F28R/L. Notable thing in these engines was that Allison claimed WER rating 1700hp at 26000ft (wet), as for comparison WER rating of the F32R was 1720hp at 20700ft (wet + aftercooler) with higher auxilary stage gear ratio. Makes me wonder how Allison rated their engines.
gripen
-
Originally posted by HoHun
Hi Greg,
Inspired by your comment on fuel economy: Do you think it would have been possible to equip the P-51 with a turbo-supercharged Allison? The V-1710 was its original powerplant, after all ...
Regards,
Henning (HoHun)
I don't know if it was ever considered to go back to Allisons on the P-51, but I do know that the F-82 Twin Mustang did have Allisons again. But I believe these used engine driven superchargers, not turbos, but I'm not sure. Widewing will know this of course.
Hmm, the P-51 was known for its enormous range, imagine what a turbocharged Allison Mustang would have been capable of.
-
The XP-51J was an attempt to go back to Allisons with the P-51 airframe. It featured the F32R engine, it flew first time April 1945 but it's unclear if it was ever flown with full ratings due to engine developement problems. AFAIK turbos were never seen as an option in the P-51 due to limited space. Basicly the F30R/L of the P-38L was the last V-1710 produced for the turbo installations, all later V-1710s featured mechanical superchargers and turbo-compound in some cases. The V-1710 powered F-82 variants had two stage mechanical superchargers.
gripen
-
Great insight from all.