P-38 with Roll-Royce Merlins

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Marshall_Stack

Senior Airman
382
8
Sep 29, 2005
Missouri
In Warren Bodie's book on P-38s, he feels that if the P-38 was retrofitted with the R.R. Merlin like the Mustang, it would have been a much better plane in Northern Europe. The problem with the Allison turbos in the cold and with the British fuel was a challenge to say the least.

What do you think?
 
That's not an unheard of idea but since the ship did fine in warm climes like the Med and Pacific it would have been hard to justify re-engining just the ETO planes. And depending on the time it might have been superfluous if the P-51 had debuted.
 
Many folks have mentioned this and there was always "folklore" at Lockheed that this was thought of - it wasn't that simple of just slappin Merlins on the airframe. Many things would of had to be re-designed, it might of not been worth the effort....
 
The Merlin was also a heavier engine I think, The original Allison engined Mustang was considered the sweeter handling machine due to less weight on the front end, but of course, it lacked the power of it's Merlin engined siblings.

THe P-38 was already quite a good aircraft as it was, if expensive and complicated compared to other aircraft. The turbocharged version wouldn't have lacked much power compared to a Merlin if any and could in fact have been better at altitude as the turbo is theoretically more adjustable. Reliability would perhaps be the only reason for the change and I dont think there were enough problems or even enough P-38s to warrant the change, especially with the Mustang coming on stream for much less and demanding the Merlin engine.
 
Lockheed did look at installing the Merlins on the P38 and there were indications of an increase in performance. It was also determined that the manufacturing process would have been easier, plus there would have been some room in in the booms made available for additional fuel cells.

But in the end, by the time they could have implimented the changes, it was decided the P51 was going to be the escort fighter and it just wasnt worth it to interrupt production.
 

Where did you hear that? The Allisons used on the P-38 were "GFE" Government Furnished Equipment and in that sceniro there is little interface contractually between "Prime" (Lockheed) and the subcontractor (Allison)
 
Allison was a GM company.

Btw, R-R had a P-38 delivered to Hucknall in 1944 for a trial installation of Merlin XXs in 1944. When it became known, they were told to return the a/c immediately. Seems it would be not that much trouble to replace the Allisons having experence previously with the P-51 conversion. Lockheed did extensive engineering evaluations of Merlin P-38s and would have transformed the P-38 in a simular manner to the P-51.
 
KraziKanuK said:
Allison was a GM company.
Click to expand...
I know...

I doubt there was any serious lobbying by Allison. Bottom line if the decision was made to replace the Allison with Merlins the powers to be would of seen it through, just as they did on the P-51.

Back then as it is today, propulsion manufacturers must cater to the prime airframe manufacturer, not the other way around....
 
One thing stopped the P-38 from receiving Merlin engines. THe production lines would have had to be shut down for two weeks in order to re-tool for Merlin installation. The loss of two weeks production was judged more important than having a better performing aircraft.
 
I'd have to look it up to get a name but the General in charge of procurement was a former GM executive and held stock in GM. This man decided the Allison would stay in the P-38.

Lockheed designed the installation of Merlins as early as '41, as an optional power plant. It was felt that the overall performance would increase but climb would suffer. The problem here is the supercharger/prop reduction gearing which can be geared for power (climb) or speed, an example of this can be seen at the following site
http://spitfireperformance.com/
You will need to go to the Mustang tests you'll note MS (.42 reduction I belive these are right but there not stated on this material) and FS (.477 reduction) gear and its affect on speed/climb. Note: the pertinent test is of a P-51H, listed as a Mustang III with a Merlin 100, the test is quite far down the page.

The turbo being less dependant on RPM for power is not affected and use the middle ground. The P-38F/Spitfire tests on the following site illustrates this extremely well showing the P-38F climb right in the middle of the two Spit IXs one of each reduction ratio.
http://prodocs.netfirms.com this is the Pro Docs page and has a huge collection of WWII aircraft info, that address doesn't always work but its all I have.

I've seen several estimates of the results of the installation form 1,000lbs added to an even swap. The drawings range from a profile like the early, more streamlined version, to a front radiator installation like the J/K/L models but without the radiators on the booms. Drag wise that would not be a big difference in drag, the front radiators are in a propeller wash area and add very little drag and the rear radiators are in the wing turbulence area and follow the "Meredeth Rule" to add a little thrust over the drag produced.

wmaxt
 
KraziKanuK said:
Did I say Allison did the lobbying?
Click to expand...
Several threads ago.....
KraziKanuK said:
The idea of putting Merlins in the P-38 was squashed by lobbying by General Motors.
Click to expand...
KraziKanuK said:
Allison was a GM company.
Click to expand...

While at Lockheed I knew several engineers who worked on the program and got to chat with them a bit. Ben Rich (he wrote the book Skunk Works, his daughter was a good friend of my ex wife) told me that there was a study done right before Pearl Harbor and again later in the war. Again, the engines were government furnished and when designated in the design phase, the government wanted to stick with the Allison, there was little complaint from Lockheed. He did say there was a problem with the rear pistions (closest to the firewall) always burning up first. This was identified to Allison...

It was also mentioned that there was a desire to keep the design "All American" although Packard eventually built the Merlin - Possible and probable...

I know the procurement folks for the AAF were out of Wright Patterson, (and are still today) and I would find it hard to believe that one general could of attempted to stop Lockheed from pursuing Merlins on the P-38. If it was true and Allison (GM) had this guy in their pocket, why not do the same when North American was planning to drop the Merlin in the Mustang?
 

I just pointed out where the decision was made and what the connections that man had. In response to your last question -
1. Allison was at capacity of an expanded factory.
2. A different officer was in charge of P-51 production, a colonel who had ties to a congressman.

I certainly don't know all the ins and out of this but
1. Why no second source for the P-38 until Jan, '45? Until March '44 it was the only AAF air superiority fighter with range and numbers to take the fight to the enemy of a 1:1 basis.
2. P-38K squashed for +/- 50 airplane (~two weeks) delay?
3. Why no unified mixture/prop/throttle control that was ready for installation but denied by the WPB.

I'm sure the "All American" argument was used in '41 and the "Don't want to delay production" argument was probably used later but who really knows?

I certainly don't dispute what you are saying, just that there seems to be more to it.

wmaxt
 
Theres always the possibilty that all Packard built Merlins were designated for the P51, so none were available.

The Merlin equiped P51's were a magnitude better in performance than the Allison equiped Mustangs, but a merlin equiped P38 only had a slight marginal improvement over the Allisons.

If I was in charge of the aircraft production board, Id veto changing the P38 line for the "umpteenth time" for such little over all improvement.
 
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