An Odd Question about P-38s

[Walrus 7]

Did anyone ever try to install Merlins in P-38s?

Having seen what the Merlin did for the P-51, I would have thought it logical to try them in all Allison-engined aircraft, especially those which had less than optimal performance in Europe. I know it was tried with the P-40, which resulted in the -F model, but my books don't note any attempt to do so with the P-38. That doesn't mean it didn't happen, though.

Walrus

[retroaviation]

Don't know if the Merlin was tried in the P-38 or not, but just because it had an Allison in it, didn't make it a bad airplane (not that you were implying that it was though). The P-38 had an external turbo-supercharger for each engine (much like the B-17's had), which made the Allison able to run well at higher altitudes.

As far as I'm concerned, the Allison is a MUCH better engine than the Merlin. There's a reason that you only see TV interviews with pilots that flew behind Merlins, not the mechanics that maintained them. Not to take anything away from the Merlin and it's role in the War though. It certainly had the better internal supercharger, which could power airplanes such as the Mustang to much higher altitudes than initially needed when designed with the Allison.

Just my two cents worth.

Gary

[JDK]

Hi Walrus,

My understanding was that the P-38 was in part withdrawn from Northern Europe due to political and logistic supply reasons, rather than actual performance issues.

A type that held its own in the Pacific as the P-38 did was, I would believe more than adequate in the ETO, in the right hands, even if not the best type in theatre.

The supply of a P-38 without turbos to the RAF who, naturally, found it a dog of course also can muddy the waters somewhat.

We have recently had a long discussion trying to list all the types that were fitted with the Rolls Royce Merlin here on Plane Talk, without mention of the P-38, so I suspect the short answer is 'no'!

Cheers,

[airnutz]

Did anyone ever try to install Merlins in P-38s?

Having seen what the Merlin did for the P-51, I would have thought it logical to try them in all Allison-engined aircraft, especially those which had less than optimal performance in Europe. I know it was tried with the P-40, which resulted in the -F model, but my books don't note any attempt to do so with the P-38. That doesn't mean it didn't happen, though.

Walrus

It was considered, but apparently expediency favored the change unnecessary...
http://home.att.net/~C.C.Jordan/P-38K.html

[Nathan]

On the old us-aircraft.com board we talked about this thoroughly. Unfortainately it was a few years ago and I cannot for the life of me remember what we found to be the reason for not putting the Merlin in a P-38. I think one factor was that the Merlins were in high demand for the P-51 so they would have been in short supply. Second I think the design of the P-38 would not have worked for the Merlin?

I am surprised Gary thinks the Allison is a better engine. Although I have heard that the Merlin had lots of overheating problems?

I think putting Allisons on the P-38 was a good idea.

Cheers,
Nate

[Wolverine]

No right-handed merlin?

[retroaviation]

I am surprised Gary thinks the Allison is a better engine

You've obviously never worked on a Merlin then, huh?

No right-handed merlin?

Yup. There's a "backwards turner" on the P-82 here in our hangar.

Gary

[Nathan]

I am surprised Gary thinks the Allison is a better engine

You've obviously never worked on a Merlin then, huh?

No right-handed merlin?

Yup. There's a "backwards turner" on the P-82 here in our hangar.

Gary

No Gary can't say that I have. Maybe you could enlighten us by telling us some first hand experiances the differences between working on an Allison and a Merlin. Please with sugar on top.

-Nate

[retroaviation]

Well, the first of all, I'm in no way an expert on any of the "steam powered" engines. I've just been fortunate enough to have had the opportunity to work on them from time to time. However, as far as my experience has been with them, the first item that's easy to mention (albeit not that big of a deal) is the tools. With an Allison, most U.S. mechanics already have SAE tools (1/2", 9/16", etc. wrenches & such). Well, if you're working on a Mustang, for example, you've got to have those SAE tools for working on the airframe, and even many engine items, BUT you also must have British Standard tools as well. Oh, and you'll need several spark plug sockets, because when removing or installing the top plugs and you drop your socket down in the valley, under the intake runners, you'll never see it again. It'll be lost forever. I bet Sparrow has quite a collection of sockets from when he disassembles an engine for overhaul.

There's plenty of other personal reasons I'd rather work on an Allison than a Merlin. On an Allison, you don't have to adjust the valves every 20 hours and retorque the heads & banks every 50. The rocker arms have rollers on them, where the (stock) Merlins don't, which means that the Merlin is MUCH more prone to ruining camshafts and such. And on and on and on.

Again, PLEASE, PLEASE don't take any of this as me slamming the Merlin. It was a great engine at the appropriate time in the War. It has obviously been the powerplant to some of the most spectacular airplanes in history. But as I mentioned before, if given the choice, I'd much rather have an Allison in front of me than a Merlin. Just my opinion.

Now back to the topic...I didn't check out the link that airnutz posted, but if they did indeed consider the Merlin for the P-38, did it also retain the external turbo-superchargers? If so, what did it look like? Any changes to the cowlings and such?

Gary

[chico]

Hi Walrus,

My understanding was that the P-38 was in part withdrawn from Northern Europe due to political and logistic supply reasons, rather than actual performance issues.

I'd have to do a lot of digging for the source, but one of the "performance" related issues what the P-38's tendency to compress at high speeds, turning it into a twin engine lawn dart during a dive. A field modification was put together by Lockheed (I'm assuming some sort of improved dive brake), but the C-47 bringing the parts was shot down in a friendly fire incident. That delay offered the Mustang a chance to further prove itself, and for its proponents to gain even more steam.

These issues were overcome once the idea of "compression" was better understood.

Ironically, the P-38's range, speed, and firepower made it ideal for use in the Pacific theater, even though those were supposedly the limiting factors affecting the aircraft in Europe.

[visaliaaviation]

It is my understanding that the P-38 required as much as 3x's the maintenance that the P-51 did. A P-47 about 1.5x', etc. It is quite apparent that the powers that be/were in the Spring and summer of 1944 betting on a forseable end of the war. Production of both -38 and -47 were being curtailed and the AAF had decided that nearly all 8th AF groups switch over to Mustangs. Unit costs were probably another factor in this decision. In the end, only 56 fg kept its P-47's till the end of hostilities there.

P-38's were simply not a viable aircraft for roles envisioned in the post war era. A "Merlin" powered P-38 is an intriguing concept, but I think economic realities blocked any developement down that line.

The P-40 F had the-1 Packard, which did not,IIRC, give it outstanding performance. One would have to wonder what a -7 would have done in say the P-40Q airframe vs Mustang? At least then we'd be comparing apples to apples.

[Dan K]

Neat article (if you've got the time).

http://www.wwiiaircraftperformance.org/ ... wayne.html

To abbreviate, scroll down to heading "Merlin Powered Lightning".


Pirating slightly ( ), I have no hands-on experience with maintaining either 1710 or 1650, but little clues hint at supporting Gary's theory about the Merlin being a comparative maintenance hog.

I'm not sure if official TBO's were ever published during wartime, but I keep seeing numbers suggesting that the Merlin's was around 500 hrs and the Allison around twice that.

I also noticed at Mike Nixon's Vintage V-12's site that the typical Allison rebuild takes 2-3 months, whereas the Merlin takes 3-4 months.

Hmmm....

[REGINALD VON GLEASON III]

the murlin was awesome

Not that I've done any wrench twisting on either, but everytime I look at an Allison I'm just puzzled by the poor design of the intake manifold. It's got so many bends and turns in it it's just a wonder that the poor thing can breath at all.

Dan

[Chris]

It seems like the Brits had this theory that if using five parts could make something work well, then using eight parts would make it work even better.