McDonnell XP-67 Moonbat

[Scott Kenny]

The Army was well aware that the I-1430 wasn't going to be continuing. That program had been cancelled while the XP-67 prototype was still being built. Mr Mac had gone around the various offices with concepts for production engines, and a contemporary memo by the Army's XP-67 project officer, John Aldridge, talks about them: "...in view of the feeling that come what may, there is no chance of further engines of this [I-1430] type being built, an engine change in the second [XP-67 prototype] airplane is the most advisable move to make. McDonnell proposes to make this change to either an Allison two-stage engine or the Rolls-Royce 14SM engine. Along with installation of one of those alternate types of engines, McDonnell proposes to install J-32 Westernhouse (sic) Jet Unit in the space now occupied by the turbo in each engine nacelle... This proposal was presented to General Carroll who directed that the matter be held in abeyance pending clarification of the engine allocation picture. Mr. McDonnell wanted to have the program approved at once as he feels that he has man-power available to start work immediately, and should it be decided to put the airplane in production, large savings in time would be accomplished by taking action now..." There's a handwritten note at the bottom of the preserved copy of this memo: "Carroll proposes - (1) select best available engine for No. 2 airplane; (2) if the second a/c is a success, go into production."

J32s? Those make less thrust than the radiator duct of a P-51D...

But Col Marshall S Roth (Engineering Division, Wright Field) painted a more realistic picture in a telephone conversation with Col R. C. Wilson (Chief of Development Engineering) on July 14, 1944. "McDonnell has been in here several times selling the idea of installing the Rolls-Royce engine with the I-70 in back... [his] conversation will lead you to believe that all there is to it is a couple of new engines and the I-70 in back but it is not that. It is a complete new airplane. The nacelles will have to be changed, and an extra wing panel added, raise the pilot's cockpit, added span, need a new tail, etc. The peculiar shape of that airplane requires everything to be faired in from one thing to another which when put all together means a complete new airplane."

As much as I might wish otherwise, Roth was absolutely right about this. McDonnell's own surviving 3-views of the mixed-propulsion aircraft show very clearly that it would have shared the general shape of the XP-67 but the new nacelles were designed to fit tightly around the I-1430 (whose frontal area was 27% smaller than the V-1710 version contemplated for substitution, according to XP-67's Case History report) would be taller, meaning that the cockpit would have to be raised higher in order to even preserve the already poor vision to the side. That would mean new forward and after fuselage as well, to preserve the shape contouring philosophy that was the basis of the whole concept. So it would be pointless to give MAC either of the alternate engines since neither would fit inside the XP-67's airframe, and there was no time or money (or honestly patience) to have MAC do detail design and wind tunnel testing for what was being shown around in cartoon form as P-67C (fighter) and P-67E (recce).

Bugger.

But now I know how to model it for gaming. Go find a 1/285 scale model when everything else is 1/300.

 

[stever_sl]

J32s? Those make less thrust than the radiator duct of a P-51D...



Bugger.

But now I know how to model it for gaming. Go find a 1/285 scale model when everything else is 1/300.

Jet engine choices were pretty limited in 1944! The early ones were pretty anemic, but actually I'm not sure what Aldridge was talking about. After extensive (and expensive!) archive searches we've only been able to turn up 2 drawings of notional P-67 mixed propulsion layouts, and neither mentions J32. One is labelled "G.E. Type I-20 Unit" which would have been the J39 if it had gone into production. (This is also the engine specified in McDonnell Engineering Report #236, describing the hoped-for Service version, P-67C.) The other is unlabelled but shows an outline of what looks like a centrifugal-flow turbojet rather than a J32's axial flow type. It seems likely that Aldridge had his wires crossed and just said the wrong thing, as did Roth in his conversation with Wilson when he spoke of "I-70" instead of "I-20." At least that's my best guess.

 

[Scott Kenny]

Jet engine choices were pretty limited in 1944! The early ones were pretty anemic, but actually I'm not sure what Aldridge was talking about. After extensive (and expensive!) archive searches we've only been able to turn up 2 drawings of notional P-67 mixed propulsion layouts, and neither mentions J32. One is labelled "G.E. Type I-20 Unit" which would have been the J39 if it had gone into production. (This is also the engine specified in McDonnell Engineering Report #236, describing the hoped-for Service version, P-67C.) The other is unlabelled but shows an outline of what looks like a centrifugal-flow turbojet rather than a J32's axial flow type. It seems likely that Aldridge had his wires crossed and just said the wrong thing, as did Roth in his conversation with Wilson when he spoke of "I-70" instead of "I-20." At least that's my best guess.

Thanks!

Those J39s are a much bigger unit than the J32, and almost certainly larger in diameter than the turbocharger used on the XI-1430 or the V-1710 including ductwork.

Personally, I'd want to stick a J30 in the back of the nacelles. The J30 is 19" in diameter and 100" long, the J31 (which was developed into the J39) is 42" in diameter and 72" long. Both engines are ~800lbs, and both engines make over 1400lbs thrust, with the J31 making 1650. (The J34 is a much bigger and heavier engine, ~1200lbs)

Looks like you'd want either a Merlin or the Allison V-1710-119, to have two-stage supercharging on the engine to open up space for a jet engine.

 

[stever_sl]

Looks like you'd want either a Merlin or the Allison V-1710-119, to have two-stage supercharging on the engine to open up space for a jet engine.

The I-1430 was perfectly capable of being fitted with better superchargers, and in fact it originally had a 2-stage 2-speed supercharger, as a letter from Continental to AAF Materiel Command on 5 October 1943 describes:

“1. In accordance with your [i.e. AAF Materiel Command] request, we have carefully review [sic] our overall experimental and research program and submit herewith a revised proposal for the Model XI-1430-9A Engine, in lieu of our proposal dated 18 June 1943, and request the substitution of the following program for the program set forth in Contract #w535 ac-39568 (Ref. a, b, c, and d).
“2. The Model XI-1430-9A Engine will be essentially the same as the Model I-1430-A1 Engine, except that it will have a single-stage – single speed supercharger in place of the two-stage – two-speed supercharger...”

 

[PhR]

Time's right to start a thread on my namesake, the XP-67 Moonbat (a.k.a. simply as the Bat). Here's a good link about it.

U.S. Army Air Force Resource Center - A Warbirds Resource Group Site

This site deals with various technical aspects of the United States Air Force, primarily the aircraft.

www.warbirdsresourcegroup.org

Moonbat

Sorry to brake a little bit your dream, but I disagree with this nickname "Moonbat". When I wrote the detailed history of this magnificent machine for French magazine "Avions", I consulted plenty of original documents, from manufacturer and from various administrations. I never found any mention of "Bat" or "Moonbat".
In addition, even if the word "Moonbat" appeared sporadictly during 19th century, it was popularized only in 1947 by Robert A. Heinlein in his science fiction novel "Space Jockey", years after the end of XP-67 story.

 

[Foo Fighter]

This potentiall ground breaking aircraft, had to have some kind of unique moniker. WOE is wrong with the name that has stuck most? I can understand those who wish for factual denomiiations to be scrosanct but, who does it hurt?

Frankly put, I have ever known this project as the 'Moonbat' and it chall remain so with me. Be happy with your preference, just do not ridicule or doubtr others for theirs.

 

[PhR]

This potentiall ground breaking aircraft, had to have some kind of unique moniker. WOE is wrong with the name that has stuck most? I can understand those who wish for factual denomiiations to be scrosanct but, who does it hurt?

Frankly put, I have ever known this project as the 'Moonbat' and it chall remain so with me. Be happy with your preference, just do not ridicule or doubtr others for theirs.

I don't want to ridicule anybody. Of course, this nickname can be used for the XP-67 by anybody wants to use it. I am just factual: this was not an official name and it was not used at the time this prototype was flying.
The older mention I found is an article from Walt Boyle entitled "It Might Have Been Moonbat". Maybe this name was used before, I don't know exactly where it comes from and when it first appeared.

 

[hesham]

My dear Philippe,

you got only half of the truth,frankly it was called "Bat",as unofficial named.

The American Fighter The Definitive Guide to American Fighter Aircraft from 1917 to the Present

 

[southwestforests]

Boeing's image archives look like they caption every photo of the McDonnell XP-67 with

"McDonnell XP-67 Bat ________________"​

​But so far I've not encountered one image where the caption says boo about the Bat name.

Some samples:

Boeing Images - XP-67 Bat on the Tarmac

Welcome to The Boeing Company's official source for licensed aerospace photography, illustrations and videos.

secure.boeingimages.com

Boeing Images - McDonnell XP-67 Bat in Assembly

Welcome to The Boeing Company's official source for licensed aerospace photography, illustrations and videos.

secure.boeingimages.com

Boeing Images - McDonnell XP-67 Bat Cockpit

Welcome to The Boeing Company's official source for licensed aerospace photography, illustrations and videos.

secure.boeingimages.com

Boeing Images - McDonnell XP-67 Bat in Flight

Welcome to The Boeing Company's official source for licensed aerospace photography, illustrations and videos.

secure.boeingimages.com

 

[PhR]

The nickname "Bat" may have been used at the time, but does not appear to have been official. "Moonbat", on the other hand, was not a word used at that time. It really looks apocryphal.

I see plenty of recent mentions of the nickname "Bat", but none are contemporary with the flights of prototype. Has anyone seen a document or testimony from the period using this nickname?

 

[bercr]

Boeing's image archives look like they caption every photo of the McDonnell XP-67 with

​

"McDonnell XP-67 Bat ________________"​

Unfortunately, the captions presented on BoeingImages are not necessarily a guarantee of historical truth. For example, look at this one (and it's not the only one):

 

[southwestforests]

For example, look at this one (and it's not the only one):

I do not have enough P-51 data in my memory to divine from the given image what it not historical truth in it.

 

[Stargazer]

I do not have enough P-51 data in my memory to divine from the given image what it not historical truth in it.

I think it looks more like a P-51H.

 

[Stargazer]

Regarding the "Bat" and "Moonbat" monickers...
Here is a 1952 McDonnell document listing all of the company's aircraft to date.
As you can plainly see, all of them carry a proper name, except for... the XP-67.
It is obvious to me that if any company-given name had existed, that would have been the logical place to find it... and yet it isn't there, which makes it abundantly clear to me that "Bat"/"Moonbat" were later inventions.

 

[bercr]

I do not have enough P-51 data in my memory to divine from the given image what it not historical truth in it.

Yes, I'm sorry, the screenshot is too small and blurry, I should change it. Stargazer is right, it's a P-51H.

 

[Arjen]

I do not have enough P-51 data in my memory to divine from the given image what it not historical truth in it.

Note pronounced kink in P-51D's rear fuselage, bulbous canopy. -H's fuselage kink further aft, less prominent. Metal canopy frame different.
1000006565: P-51D
1000006564: P-51H

 

[Stargazer]

Note pronounced kink in P-51D's rear fuselage, bulbous canopy.

Your post is not quite clear I think: perhaps clearly label the two photos as P-51D vs. P-51H...

The canopy on the "H" model is flattened, and the ventral intake extends a lot further towards the tail; the fin is also shaped differently (among many other differences).

 

[southwestforests]

Yes, I'm sorry, the screenshot is too small, I should change it. Stargazer is right, it's a P-51H.

In the meantime I enlarged photo and looked up the tail number.
Some references give 464164 as the prototype XP-51G and some give other tail numbers for that/those aircraft.

Oh, probably should clarify that I enlarged the image at Boeing's website, not the one here.

 

[Arjen]

@Stargazer You're quite right, but when I attach images the original filename disappears. Amended.
@southwestforests XP-51G was one of the lightweight Mustang variants.

 

[southwestforests]

Unfortunately, the captions presented on BoeingImages are not necessarily a guarantee of historical truth. For example, look at this one (and it's not the only one):

Just now found this about it, interesting data nugget there on the last line,

https://www.aerialvisuals.ca/AirframeDossier.php?Serial=227715

​		Constructed as a P-51H-1-NA by North American at Inglewood, California, USA.​
Circa 1944​		Taken on Strength/Charge with the United States Army Air Force with s/n 44-64164.​
​		Transferred to NACA Ames Aeronautical Laboratory, NAS Moffett Field, CA.​

 

[Apteryx]

I don't want to ridicule anybody. Of course, this nickname can be used for the XP-67 by anybody wants to use it. I am just factual: this was not an official name and it was not used at the time this prototype was flying.
The older mention I found is an article from Walt Boyle entitled "It Might Have Been Moonbat". Maybe this name was used before, I don't know exactly where it comes from and when it first appeared.

It stands to reason that people were calling the XP-67 the "Bat" informally while it was under test or at least after photos of it were made public. Its planform was notably bat-like, after all. There's no reason to think that MAC gave it an official company name--the prototype never got close to serial production, after all. The real evidence for "Bat" being the contemporary, and widely used, nickname is that MAC continued the "spooky" style of names when they actually got planes into production, e.g. the Phantom, Demon, Voodoo etc. Fun fact, related in Tommy Thomason's wonderful monograph on the F4H Phantom II: MAC held an in-house naming competition, and let employees vote on a name. Their choice was the Satan. BuAer had veto power, of course, and went with Phantom II.

 

[Mark Nankivil]

Unfortunately, the captions presented on BoeingImages are not necessarily a guarantee of historical truth. For example, look at this one (and it's not the only one):View attachment 729408

P-51H - look at the leading edge fo the wing and the fuselage is also slightly different.