Merlin 28 powered P-39

This has been touched on before in numerous previous threads.

Usually the discussion centres around the 2 stage 60-series Merlins, which have much improved altitude performance. The downsize for the Merlin 60-series in the P-39 is the extra weight (1640-1690lbs) of the engine compared to the Allison (c. 1325-1350lb) and the vastly increased cooling requirements.

The weight of the 2 speed single stage Merlins is much less than 60 series, being listed at 1460lb (Lumsden). A bit over 100lbs more than the Allison, but without the need for extra cooling for an intercooler.

The length of the Merlin is also a problem. At 88.7" long it is longer than a single stage F series V-1710 (I use the F series because the E series doesn't have the reduction gear and wouldn't, therefore, be comparable to the Merlin). How much longer, I am not sure (wiki gives 85.81" for an F30R).

But what of the two speed single stage Merlins - the XX series?

The 2 speed Merlins have a length of 71" (69" for single speed). Their width is 29.8" vs 29.2" for the V-1710 (and 30.7" for 2 stage Merlins). The height of the Merlin is somewhat more than the V-1710 at 43.0" (vs 37.65" for the V-1710, 41.2" for the single speed Merlin and 40.0" for the 2 stage Merlin). Some, or all, of that is, doubtless, due to the downdraft carburettor.

The downdraft carburettor would be, IMO, the biggest hurdle to fitting the Merlin 28/V-1650-1. So, if a downdraft carby could be fitted to the Merlin it should fit. I see no major difficulties in doing this, apart from engineering time.

But what of performance?

The P-40F seems to have had a good performance increase when compared to the P-40E. Especially at higher altitudes.

The P-40E seems to have a maximum speed of 342mph @ 11,400ft, dropping to 340mph @ 15,000ft. 11,400ft looks to be the critical altitude of the V-1710-39.

The P-40F looks to have a top speed of around 364.5mph @ 19,270ft (FS gear) and 350.5mph @ 12,800ft (MS gear).

(This chart gives a maximum speed of 361mph @ 15,000ft for the P-41E vs 365mph @ 19,270ft for the P-40F.)

The P-40F also appears to have a time to climb advantage over the P-40E - 10.2 minutes to 20,000ft vs 11.82 minutes.

So, could a Merlin 28/V-1650-1 P-39 have been done?
Should a Merlin 28/V-1650-1 P-39 have been done?
Would the 2 speed Merlin transform teh P-39's performance, or merely make a slight improvement?

Not unless Merlin engine production is drastically increased in time to be installed in P-39.

British built fighter aircraft had priority for RR Merlin engine. Lancaster Bomber was second in line and about half of those engines were made in Detroit. If you want Merlin engine in other aircraft such as P-39 then you need a second U.S. manufacturing plant.

A better engine in the P-39 definitely would have helped. But I'm not sure it would have made it a more dominate player in the air war. The western allies had no clue how to use the P-39. The Russians on the other hand used it to great advantage. Many of their top aces at one time flew the P-39. Pilots using proper tactics combined with knowing the P-39 strengths were very deadly to the LW.

Most American pilots had no clue how to succeed with P-40 either during December 1941. P-39 pilots will learn the hard way just as P-40 pilots did.

davebender said:

Most American pilots had no clue how to succeed with P-40 either during December 1941. P-39 pilots will learn the hard way just as P-40 pilots did.

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What tactics would the P-39 have used to succeed against the Zero? The same as used by the P-40's?

Coyote said:

A better engine in the P-39 definitely would have helped. But I'm not sure it would have made it a more dominate player in the air war. The western allies had no clue how to use the P-39. The Russians on the other hand used it to great advantage. Many of their top aces at one time flew the P-39. Pilots using proper tactics combined with knowing the P-39 strengths were very deadly to the LW.

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Russian tactics with the P-39 were relative to their overall tactics which focused on low altitude operations, to which the P-39 was better suited. They didn't try to use the P-39 in as an interceptor against bombers operating at 20,000 feet as the USAAF did in New Guinea, a role in which it was slightly less than useless. It also made it a sitting duck for the Zero escorts who were always higher. By the time
that became apparent and it was now longer used in that role, newer models of the Allison were available for the later model P-39s and P-40s that offered altitude performance closer to the Merlin XX.

Duane

P-39 is faster which makes boom zoom an obvious choice.

davebender said:

P-39 is faster which makes boom zoom an obvious choice.

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The P-39 was faster, but the Zeros would be higher. Does anyone have a rule of thumb for the point where an altitude advantage overcomes a level-flight speed advantage (at least for the Japanese planes in question)?

davebender said:

Not unless Merlin engine production is drastically increased in time to be installed in P-39.

British built fighter aircraft had priority for RR Merlin engine. Lancaster Bomber was second in line and about half of those engines were made in Detroit. If you want Merlin engine in other aircraft such as P-39 then you need a second U.S. manufacturing plant.

Click to expand...

I can't remember if it was 1/5 or 1/3 of all Packard Merlin production was to be used for USAAF aircraft. It was a contract stipulation. That's why P-40s got V-1650-1s.

It was supposed to be 1/3.

Not necessarily.

P-39s could be flying @ 5,000 feet, providing escort for light bombers flying @ 1,000 feet. Zeros must come down low if they intend to intercept the bombers. If bombers aren't intercepted then American forces win by default when bombs start impacting on target.

Shortround6 said:

It was supposed to be 1/3.

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Right.

And where did all those V-1650-1s go?


As far as I can tell the only aircraft to get the V-1650, until teh -3 and P-51B), was the P-40. Isn't the P-39 just as good a recipient as the P-40?

davebender said:

Not necessarily.

P-39s could be flying @ 5,000 feet, providing escort for light bombers flying @ 1,000 feet. Zeros must come down low if they intend to intercept the bombers. If bombers aren't intercepted then American forces win by default when bombs start impacting on target.

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Surely in that instance the altitude gives the Zeroes the tactical advantage, and their speed disadvantage to the P-39 is cancelled because of the ability to dive onto the target?

wuzak said:

Surely in that instance the altitude gives the Zeroes the tactical advantage, and their speed disadvantage to the P-39 is cancelled because of the ability to dive onto the target?

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Height advantage can be negated depending on what alt you are at. Bombers/escort flying below 1000ft leaves little room for interceptors to boom and zoom.

Since most of the combats between Zeros and P-39s took place over New Guinea, there'd be very few places you could fly 1000 ft, if you were over land.
The Owen Stanley mountain range dominates New Guinea,as high as 12,000 ft, and missions flown between allied and Japanese strongholds meant flying over those mountains. You don't clear foggy, turbulent, mountain passes by just a few hundred feet with a formation of bombers.
To get to the Japanese we had to operate at the altitudes dictated by the terrain.