Has a Merlin ever been put into a P-39?

[MikeGazdik]

I have been reading through old posts, and digging up some nice newfound information on the P-39, one of my pet favorites. ( I like underdogs I guess)

Has anyone ever seen or heard about the P-39 having a Merlin installed? For racing or any other reason? That might be quite an airplane!!

[Colin1]

As far as war production goes

I don't think the P-39 was ever even conceptualised with a Merlin but the USAAF placed an order on 27Jun41 for two prototypes of the P-63 powered by the same V-1710-47 engine. The serials were 41-19511 and 41-19512.
A third prototype was also ordered, 42-78015, this one fitted with the Packard Merlin.
The first prototype, 41-19511, flew for the first time on 07Dec42, the first anniversary of Pearl Harbour. It was destroyed on 28Jan43 when its landing gear failed to extend.
The second prototype, 41-19512, followed 05Feb43. It too was destroyed, this time due to an engine failure.
The Merlin-engined 42-78015 was later delivered with another Allison instead, as the Merlins were primarily needed for the P-51.

and as far as air racing goes

A P-63C-5 (44-4181/NX73744, race no 53) in natural metal finish was brought to the 1948 air races by Frank Singer. A year later, Singer returned with a P-63C-5 painted dark grey and trimmed in red.
Decades later, it is not clear whether Singer had one Kingcobra or two. Re-registered (B9009/race no 90) this ship was extensively modified and distinguished by a tiny bubble canopy when flown in the 1971 San Diego air races piloted by Larry Havens.
This aircraft had a shortened wing, concave wing tips, and a V-1710-135(G4) engine.
Plans existed to convert the craft to a Merlin engine but before they could materialise, it was lost on a trials flight on 07Sep72 when Havens bailed out.

And that's about as much as I can find concerning Merlin interest for the P-39.

Sources
Bell P-39 Airacobra
Robert F Dorr & Jerry Scutts
Crowood Aviation Series
ISBN: 1 86126 348 1
Page 130

[MikeGazdik]

Wow, very detailed, thanks for the info Colin. I didn't think the Air Corps / Bell had had ever tried. I had figured some racer would have attempted the conversion. With the amount of P-39 /P-63 airframes being found on the increase, I wonder if anyone would try it in the future.

Which leads me to two more seperate thoughts. 1) Is a P-39 / P-63 lighter than a P-51 and if so, would that translate to more speed around the pylons? 1b) A P-63 does have laminar airfoil wings correct? 2) If the Allisons were orginally better at low altitude, and the Merlins at high altitudes, why are the Merlins THE inline for Unlimited racing? Couldn't the Allison be tuned to equal or greater performance since the racing is on the deck. Or is the Allison still limited by its single stage supercharger even down low when racing?

[claidemore]

There are low alt rated Merlins, as well as high alt ones.

[Colin1]

Originally Posted by MikeGazdik

1) Is a P-39 / P-63 lighter than a P-51 and if so, would that translate to more speed around the pylons?

1b) A P-63 does have laminar airfoil wings correct?

P-39
Empty: 5,600lbs (2540Kgs)
Loaded: 7,780lbs (3530Kgs)
Max speed: 380mph

P-63
Empty: 6,375lbs (2892Kgs)
Loaded: 10,500lbs (4763Kgs)
Max speed: 410mph

P-51 (Allison)
Empty: 6,300lbs (2858Kgs)
Loaded: 8,600lbs (3901Kgs)
Max speed: 390mph

P-51D
Empty: 7,125lbs (3230Kgs)
Loaded: 11,600lbs (5,206Kgs)
Max speed: 437mph

The P-63 was outwardly similar to the P-39, the lineage was obvious and unmistakeable but it was a completely different aircraft. Unfortunately, most of the novel design features were set prior to Pearl Harbour; at the time the design must have looked as good as anything.
The P-63 did indeed employ a laminar-flow wing section but I have my doubts as to the efficacy of the technology as applied to any WWII fighter, not just the P-63.

[MikeGazdik]

I guess what I am getting after is this thought. P-51 and P-63 both have laminar wings. The 63 is a little lighter, and I may suspect a little more aerodynamically clean. Put a race Merlin in one with the right prop, you might have a tough racer!

[Colin1]

Originally Posted by MikeGazdik

I guess what I am getting after is this thought. P-51 and P-63 both have laminar wings. The 63 is a little lighter, and I may suspect a little more aerodynamically clean. Put a race Merlin in one with the right prop, you might have a tough racer!

Yes
I can see what you're driving at, the fly in the P-63 ointment for me was the retention of the awful, car-door/canopy arrangement that must have dragged at the a/c's aerodynamics.
A few were fitted with a teardop-style canopy a la P-51D, other than that it looked a beautifully clean a/c that has features I'm surprised weren't more extensively emulated throughout the industry. The use of leading-edge radiator cooling, vented at the trailing edge exploiting Meredith Effect and doing away with boxy, under-wing coolers and ventral scoops. This, admittedly, might have proved tricky for a/c using Fowler flap arrangements but then again, maybe not, the vent being blended into the upper wing possibly.

The other is the mid-engined layout, contentious maybe but like performance cars, it distributes the a/c's weight beautifully, gets it up on tricycle undercarriage for better ground-handling visibility and puts a big, punchy armament in the airscrew. I don't know how comfortable a pilot would feel sitting so close to the airscrew but he could conceivably have been moved much further forward giving him an unparallelled view of his own battlespace, instead of the enemy a/c 'disappearing' behind his engine cowl; it wasn't until planes like the Me163, the Ar234 or the Meteor that this was exploited. I discount the P-38 pilot because he doesn't have airscrews in front of him to worry about.

Fitted with the Packard Merlin, I see no reason why it couldn't have competed with the P-51 in everything but long-range escort - the only viable internal tankage area being occupied by the engine.

As a racer, I agree, it would have made a tough opponent but neither the P-63 nor the P-51 were fast enough in level flight to truly exploit laminar-flow technology - it wouldn't have helped.

[FLYBOYJ]

Originally Posted by Colin1

YesA few were fitted with a teardop-style canopy a la P-51D, other than that it looked a beautifully clean a/c that has features I'm surprised weren't more extensively emulated throughout the industry

Agree...

[drgondog]

Originally Posted by Colin1

P-39
Empty: 5,600lbs (2540Kgs)
Loaded: 7,780lbs (3530Kgs)
Max speed: 380mph

P-63
Empty: 6,375lbs (2892Kgs)
Loaded: 10,500lbs (4763Kgs)
Max speed: 410mph

P-51 (Allison)
Empty: 6,300lbs (2858Kgs)
Loaded: 8,600lbs (3901Kgs)
Max speed: 390mph

P-51D
Empty: 7,125lbs (3230Kgs)
Loaded: 11,600lbs (5,206Kgs)
Max speed: 437mph

The P-63 was outwardly similar to the P-39, the lineage was obvious and unmistakeable but it was a completely different aircraft. Unfortunately, most of the novel design features were set prior to Pearl Harbour; at the time the design must have looked as good as anything.
The P-63 did indeed employ a laminar-flow wing section but I have my doubts as to the efficacy of the technology as applied to any WWII fighter, not just the P-63.

Hard to pin down. What we do know is that airfoil had a very low Cd0. We debated (on this site) quite extensively Gene Lednicer's VSAERO modelling paper for the P-51B and D, the Fw 190A and D-9 and the Spit IX with excellent graphics demonstrating pressure distribution and drag results very closely approaching the wind tunnel results.

The only limitation that VSAERO had from any theoretical modelling approach I have seen is the inability to introduce surface roughness and any non-steady indicial velocity components to test separation conditions for AoA below critical.

Interestingly again, from one of the NACA Charts Lednicer presented, the 51 was second only to the P-80 (of US) in total parasite drag - and definitely superior to both the 190s and the Spit and 47 and F4U and P-38 - all of which were in the Spit IX range, above the Fw 190D-9.

[Colin1]

Originally Posted by drgondog

Hard to pin down. What we do know is that airfoil had a very low Cd0. We debated (on this site) quite extensively Gene Lednicer's VSAERO modelling paper for the P-51B and D, the Fw 190A and D-9 and the Spit IX with excellent graphics demonstrating pressure distribution and drag results very closely approaching the wind tunnel results.

The only limitation that VSAERO had from any theoretical modelling approach I have seen is the inability to introduce surface roughness and any non-steady indicial velocity components to test separation conditions for AoA below critical.

Interestingly again, from one of the NACA Charts Lednicer presented, the 51 was second only to the P-80 (of US) in total parasite drag - and definitely superior to both the 190s and the Spit and 47 and F4U and P-38 - all of which were in the Spit IX range, above the Fw 190D-9.

I've not read that report
it sounds interesting and I'd like to dig it up and go through it.
I'm a big fan of the late Lee Atwood, a US aeronautics and later astronautics engineer; the man was a god and I have huge admiration for him, a genuinely clever guy.
He did some paper on laminar-flow and how it was there on the Mustang, it just didn't do much (what chance of finding that, I wonder?); I seem to remember something about laminar-flow being key to a WWII combat pilot in the dive.

[Marshall_Stack]

How about putting a turbosupercharger in the P-39 as originally designed? I know that Bell fought to keep the turbosupercharger on the plane despite the USAAF and NACAs infinite wisdom to delete it (either because of drag or problems with the turbo). If I was Bell, I would have continued testing on that configuration.

I wonder what would have the higher gas consumption; the turbo and Allison or the Merlin 61?

[Colin1]

Originally Posted by Marshall_Stack

I wonder what would have the higher gas consumption; the turbo and Allison or the Merlin 61?

Looking at it purely from a mechanical data point of view;

Allison
Weight: 1340lbs (608Kgs)
Displacement: 28 litres (1710 cu in)

Merlin 61
Weight: 1320lbs (600Kgs)
Displacement: 27 litres (1650 cu in)

the Merlin looks to shade the Allison on fuel; 'ain't no replacement for displacement' holds but it costs fuel. The weight of any supercharger would also need to be added to the all-up weight of the Allison.

[davebender]

'ain't no replacement for displacement' holds but it costs fuel

I am under the impression that newer versions of the DB605 were more fuel efficient then newer versions of the RR Merlin despite having a greater displacement.

[Colin1]

Originally Posted by davebender

I am under the impression that newer versions of the DB605 were more fuel efficient then newer versions of the RR Merlin despite having a greater displacement.

You're probably right
but as a rule of thumb it does hold some water...

my previous post doesn't unequivocally state that the Merlin was better on fuel than the Allison, I used basic, mechanical data to present my assumption that it probably was

[drgondog]

Originally Posted by Colin1

I've not read that report
it sounds interesting and I'd like to dig it up and go through it.
I'm a big fan of the late Lee Atwood, a US aeronautics and later astronautics engineer; the man was a god and I have huge admiration for him, a genuinely clever guy.
He did some paper on laminar-flow and how it was there on the Mustang, it just didn't do much (what chance of finding that, I wonder?); I seem to remember something about laminar-flow being key to a WWII combat pilot in the dive.

http://www.ww2aircraft.net/forum/pol...s-12456-4.html (Allied tests of captured Bf-109's)

Colin - Here is where I posted it last year..last link, bottom page, post 60