Why not a jet driven P-38?

[Graeme]

Originally Posted by delcyros

It seems the idea was not unpopular.

But not very successful.

Originally Posted by delcyros

BTW- has anyone a detailed drawing of the sections in question (midwing section and more importantly the center fuselage gondola)?

This may help.

[SoD Stitch]

Originally Posted by Graeme

From SoD StitchI have very little on Lockheed's P-38 floatplane, do you have more on it?

The P-38 floatplane was a proposal conceived by Hal Hibbard, Lt. Ben Kelsey, and Kelly Johnson to install floats on a "standard" P-38E airframe; the only major modification would have been the upswept empennage. The floats were designed to just bolt-on to the bottom of the engine nacelles, while leaving the standard tricycle landing gear alone for normal land operations. The main impetus for coming up with the proposal was as a solution for ferrying large numbers of aircraft across the Pacific Ocean without having to put them on ships. The theoretical range of the P-38 floatplane was approximately 5,000 miles, as the floats would double as 1000-gallon drop tanks. The proposal also included the provision for jettisoning the floats in-flight in case of combat or a similar in-flight emergency. Also, this way the plane could take-off from water but land on a normal runway.

With the US's victory at Midway, this became a moot point, as P-38's could fly all the way to Midway from either the Aleutians or Hawa'ii. Several plans and artwork were generated by Lockheed depicting the floatplane version, but no prototypes were ever built or even started.

[delcyros]

Thanks Graeme. I used that picture to give an expression how the side appearence of the center fuselage section would be in comparison to a normal P-38H. Note that the J-31 mod 3 fit´s well into a new rear fuselage. I suspect that the parasite drage is increased slightly and the very section where the engine fits is needed to have a more circular diameter instead of an oval one. This requires a longer exhoust pipe to reduce drag as shown in the picture below. A later mod might adress this problem more properly.

For more details I would need to have a copy from a scale cutaway drawing or the instruction manual for mechanics. Can anyone point me to sources?

Thanks in advance and kind regards,

delc

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[Graeme]

Eric and SoD Stitch, thanks for the info on the waterborne P-38 project.

Originally Posted by delcyros

For more details I would need to have a copy from a scale cutaway drawing or the instruction manual for mechanics. Can anyone point me to sources?

Can cutaways be drawn to scale? (isometric?).

[kool kitty89]

I found this on wikipedia: "Buffeting was another early aerodynamic problem, difficult to sort out from compressibility as both were reported by test pilots as 'tail shake'. Buffeting came about from airflow disturbances ahead of the tail; the airplane would shake at high speed. Leading edge wing slots were tried as were combinations of filleting between the wing, cockpit and engine nacelles. Air tunnel test number 15 solved the buffeting completely and its fillet solution was fitted to every subsequent P-38 airframe. The problem was traced to a 40% increase in air speed at the wing-fuselage junction where the chord/thickness ratio was highest. An airspeed of 500 mph at 25,000 feet could push airflow at the wing-fuselage junction close to the speed of sound. Filleting forever solved the buffeting problem for the P-38E and later models."

So since they solved buffeting and compressability problems at speeds of 500+mph (which the P-38 could manage in a dive) maby a jet version would have been workable. Even if you slimmed down the (now engineless) nacelles and booms for less drag there'd still be plenty of room for fuel to increase capasity which could bring range up to acceptable standards. Still, it probably wouldn't reach 600mph, but even the P-80A barely made it past 550mph in level flight.

Also, there were turboprops in 1945, the first relatively reliable one was tested in March of '45.(Though I'm not sure this model would have been realistic for the P-80 since it would have been over 40" wide since it was based on the Dewent turbojet)
From Wikipedia: "The first British turboprop engine was the Rolls-Royce RB.50 Trent, a converted Derwent II fitted with reduction gear and a Rotol 7 ft 11 inch five-bladed propeller. Two Trents were fitted to Gloster Meteor EE227 — the sole "Trent-Meteor" — which became the first relatively reliable turboprop powered aircraft. From their experience with the Trent, Rolls-Royce developed the Dart, which became one of the most reliable turboprop engines ever built. Dart production continued for more than fifty years."

[kool kitty89]

Also I think Lockheed wouldn't have chosen to adapt the P-38 because, though do-able, Lockheed already had jet airframe sesigns to work with Like the L133 and Bell's single-engine version of the Airacomet (which was reworked into the XP-80).

In addition, Lockheed wasn't chosen to design the craft to be fitted with the GE engines (I-A, I-16, J31) adapted from the british welland. Bell got that contract, and the main reason was that Bell wasn't producing any crucial aircraft at the time (also other reasons like Bell's close proximity to the GE plant), while Lockheed was heavily depended on for wartime production. The reason Lockheed started working on the XP-80 design was started when they were given Bell's plans for their single-engine version because their hands were full with the main design.

At first I wondered why Lockheed even bothered working on Bell's design and didn't simply change the L133 to use a single engine. Then I realized how rushed they were with only180 days to design a working prototype. The more conventional design would be easier to develop in the limited time window.

Bell was pushed into a symilar position, but they were worse off without being allowed to streamline and optimise the airframe, (the government did this to try to shorten development time and to not infringe on other projects) which was probably a bad idea since they could have still made the deadline. Bell also didn't have much information on the performance of the engines to base their design on. All these factors led contributed to the mediocrity of the P-59, which I think had the performance potential of the early Meteors though it's design probably wasn't as adaptible as the Meteor's. If developed properly I think the P-39A would have been comperable to the Meteor F1 and the P-59B comperable to the F3, (both model's had coperable engines too: with the I-16/J31(early model)=the welland and the J31(late model)=the derwent I). But after this Lockheed's designs would have beaten the airacomet in performance and development potential, as well as the use of a single engine which would mean fewer limits on production numbers.

I know I strayed from the main topic a little but it's still interesting and maby I'll get some more intrest in this topic again.

[delcyros]

Originally Posted by kool kitty89

In addition, Lockheed wasn't chosen to design the craft to be fitted with the GE engines (I-A, I-16, J31) adapted from the british welland. Bell got that contract, and the main reason was that Bell wasn't producing any crucial aircraft at the time (also other reasons like Bell's close proximity to the GE plant), while Lockheed was heavily depended on for wartime production. The reason Lockheed started working on the XP-80 design was started when they were given Bell's plans for their single-engine version because their hands were full with the main design.

This certainly was the case from Lockheeds point of view. I personally regard the P-59 as technology demonstrator plane and little else.

Originally Posted by kool kitty89

At first I wondered why Lockheed even bothered working on Bell's design and didn't simply change the L133 to use a single engine. Then I realized how rushed they were with only180 days to design a working prototype. The more conventional design would be easier to develop in the limited time window.

Actually, the L133 was a no go. It´s fuselage cross section reveals that it was dimensionated around a L1000 axial jet engine (a design which never worked), so redesigning the fuselage to fit the larger radial J-31 or -34 is a major task. Add the unprooven airframe concept and Your own observations and You see how wisely Lockheed kept the balance between prooven work and own studies.

Originally Posted by kool kitty89

I know I strayed from the main topic a little but it's still interesting and maby I'll get some more intrest in this topic again.

Yes, a highly fascinating topic, my friend!

[kool kitty89]

Thanks for the complement.

The airacomet was also useful as a conversion trainer.
And I wonder why they didn't use low mounted wings on the P-59 like they did with the single engined version. I looks like the engines could fit over the wings (where the air intakes are in the XP-59B pictured on pg 1 of this topic) without the exaust hitting the tailplane.

Any comments on the improvements on the P-38's compressability and buffeting problems?

Perhaps 2 Westinghouse J30 axial jet engines would have worked in the the L133 they were rated at 1600 lbf each (about the same as the welland and early J31) and first entered production in late '44, though problems delayed it until early '45 (when FH Phantom's prototype took to the air for the first time-- though this plane ened up as the navy's equivalant of the P-59 and only 62 were produced) The J30 was the first american axial turbojet to enter production. But by this time the XP-80 would have already been well uner way so it would probably have been more attractive than the L133.
Also I think you mean J33 not J34 as the J34 was another early Westighouse axial turbojet (which was later available with an afterburner), actualy a later development of the J30 and was used in the sucessful McDonnell F2H Banshee as well as the failed Vought F6U Pirate and Curtiss-Wright XF-87 Blackhawk (which looks coincedentaly alot like Gruman's Tigercat.)

I took another look at the L133 design an now see that it's obvious that it needed 2 engines since the 2 exaust exits are on either side or the tail and there were no working sesigns for divergent-exaust engines available yet. I'm not sure of the size of the J31, but it looks like it's about 4 ft wide and from what I've seen of the L-1000 it wasn't too much less than 4ft wide (maby 3 ft) so maby this might have been used, though until the P-59 was canceled these were probably all diverted tward it. But the J31 was in production before the J30 so maby it would have been an option...
Check it out here: General Electric J31 - Wikipedia, the free encyclopedia Here's a clip from the history channel about GE's early engines: Video Clips (click on the 3rd clip)

Here's a pic of the L-1000 and a draft of the L133 design from here: EnginesUSA and L133

[FLYBOYJ]

Originally Posted by kool kitty89

At first I wondered why Lockheed even bothered working on Bell's design and didn't simply change the L133 to use a single engine. Then I realized how rushed they were with only180 days to design a working prototype. The more conventional design would be easier to develop in the limited time window.

You have to realized that military contractors - back then and even today don't have a say in certain situations and this was probably one of them, especially if they are spending government money.

AAF officials never liked the L133 design, but as stated the wing was used on the XP-80.

[kool kitty89]

I'm pretty sure the airforce regected the design because of its radical desicn. (as they perfered a more conservative approach and Lockheed had a hard enough time getting them to accept the P-38 design)

Earlier you posted that the P-80 used the P-38's wing, later you said it used the L133's, so which is it?

[Soundbreaker Welch?]

A P-38 called the Black Pearl?

Kilroy Jack Sparrow wasn't around in WWII. <[:{0

[FLYBOYJ]

Originally Posted by kool kitty89

I'm pretty sure the airforce regected the design because of its radical desicn. (as they perfered a more conservative approach and Lockheed had a hard enough time getting them to accept the P-38 design)

Earlier you posted that the P-80 used the P-38's wing, later you said it used the L133's, so which is it?

The P-80 used the L133's wing - the P-80 also used the wingtips from the P-38 as well as the nose (although it was turned upside down)

[kool kitty89]

Oh, thanks for the clarification.
Still, does anyone have coments on the impoved compressibillity and buffeting characteristics of the later models I mentioned a few posts back?

[kool kitty89]

I know we've reasoned-out all the reasons of why the P-38 was not converted to jet propultion but here's a website full of alternate configurations of the Lightning just for fun: Translated version of http://www.kristofmeunier.fr/

[Civettone]

Impressive site, what an imagination and effort this guy put in! Some of his designs are really fantastic.

Kris