Curtiss XP-55 Ascender canard fighter (Model CW-24)

[alfakilo]

Thanks very much for all the photos! Very neat thread!

I've always wondered what the designers of aircraft such as this thought they were going to gain over the existing conventional layouts. One thing seems certain...few to none of them ever panned out.

 

[Kevin Renner]

The XP-55 fell victim to two things that greatly affected its possible success. The first was the abandonment of the Pratt & Whitney H type sleeve valve engines. P&W was allowed by the USAAF to shut down the two H 24 cylinder engines they had under development to concentrate on the R-4360. The second was the dawning of the jet age. Now as to whether or not the XP-55 would of been able to meet its performance goals with the X-1800 is another matter. Curtis was not on top of their game by this time. But I think a jet conversion ala the Saab 21R would of been intersting

 

[Apteryx]

Amazing photos! Some details I'd never seen before in other photos, for which I'm grateful!

What spoils this fantastic restoration job a little is the use of a modern non-USAAF font for the writings underneath the cockpit (me and my perfectionism... : )

The font is Arial, designed all the way back in 1982. Probably vinyl letters. If they had a vector file of the authentic lettering, they could have used that same vinyl as a stencil and sprayed the lettering on!

Still, it's mind-blowing to see this bird looking so good.
--
Ian

 

[elmayerle]

What went wrong with the XP-55? Well, having used the NACA wind tunnel test reports on it as the basis for my semester-long project in a graduate-level stability and control course, i can say that the numbers say the aircraft most likely was bloody difficult to fly and quite unstable.

 

[Stargazer]

I'm pretty sure that with a bit more reworking such as redesigning the fins or enlarging the canards, it would have flown well.

We take for granted that an aircraft is more or less the same general configuration because we have been told so for decades, and even official agencies always showed strong reserves when faced with challenging designs. I'm convinced that putting a jet-powered Ascender in production might have changed drastically the way we conceive of aircraft, opening minds early to new ways of flying.

 

[elmayerle]

Actually, the greatest instability was in pitch control from the published wind tunnel test data.

 

[Antonio]

'm pretty sure that with a bit more reworking such as redesigning the fins or enlarging the canards, it would have flown well.

From the books and articles I've read I guess it was not so simple. Evan told about it in the previous reply.

There are designs canceled for political reasons but most unbuilt designs basically don't work for technical reasons.

I'm not a engineer but If I understanded it right, canard designs stability problems are not easy to solve with aerodynamic configuration alone. Modern canard aircraft rely on computer aided flight systems.

Dear engineers could you help us?

Thanks in advance

Antonio

 

[overscan (PaulMM)]

Sorry Stargazer, but my money's on Evan.

 

[GeorgeA]

One of the bigger problems with canard designs is managing the CoG as the fuel burns off. It's not an insurmountable problem, but it is a challenge.

 

[alfakilo]

Here is a quote I found...

Issued on November 27 1939, The Curtiss XP-55 Ascender was another response to Circular Proposal R-40C. It called for a fighter that would be much more effective than any extant--with a top speed, rate of climb, maneuverability, armament, and pilot visibility, all of which would be far superior to those of any existing fighter.

Earlier, I asked what benefits a design such as this might be thought to have over the existing conventional layouts...using these objectives, my thoughts...

1. Top speed. With the proposed engine, possibly a top speed that was on a par with the later P-47 and P-51 versions...450mph and above. But, as everyone found out, there is a limit to what a piston engine can do, as well as the aerodynamics of the airframe itself as speeds approached 500mph.

2. Rate of climb. With that much power, climb rate may well have been superior.

3. Maneuverability. Not too sure this would have been a winner. The test flights ran into problems with pitch control and stalling...not the kinds of problems wanted in a fighter. High angle of attack behavior seems to have been a significant issue.

4. Armament. Descriptions vary between the proposed number of machine guns and cannon...but for the 1939 time frame, the proposals didn't significantly exceed the existing armament of the P-39 or P-38. In its final configuration of four .50 m/g, it was at best average for the time.

5. Visibility. Not the best, even for 1939, the P-39 and P-38 both had canopy designs with fewer obstructions. The relatively long nose would have been a detriment in a turning fight since the pilot's visibility would have been reduced...this would have been particularly troublesome when trying to line up a firing solution on a turning target.

Makes me wonder what the airplane would have been like given the original engine power and the development time to iron out the stability issues.

 

[Retrofit]

One of the bigger problems with canard designs is managing the CoG as the fuel burns off. It's not an insurmountable problem, but it is a challenge.

I think the XP-55 was not a true canard (where the CG is situated between the main wing and the forward surface) but more a "stable" flying wing, obtaining longitudinal stability only from the position of the wing relative to the CG, with a forward mounted (canard emulation) free-floating manoeuvring elevator.

 

[Stargazer]

3. Maneuverability. Not too sure this would have been a winner. The test flights ran into problems with pitch control and stalling...not the kinds of problems wanted in a fighter. High angle of attack behavior seems to have been a significant issue.

Hey, why do you think even Burt Rutan himself designed a midget fighter, the ARES, from scratch? I don't think a VariEze or a Long-EZ type would be appropriate for high angle of attack manoeuvers. For all the rest, they are great flyers, but fighting calls for very different requirements.

 

[AeroFranz]

The c.g. issues are best solved with fuel tanks closer to c.g., as in wing strakes a la Long Eze. other major considerations pertain to airfoil selection. The much touted stall-proof-ness of canards is achieved only if you pick an airfoil with lower maximum lift coefficientit on the foreplanes compared to the main surfaces. This way the nose stalls first, and produces a restoring moment in pitch. I am not sure the XP-55 had such feature, if they had figured that one out. I know it took none less than John Roncz to give the Ezes acceptable flying qualities, and then at the cost of all sorts of aerodynamic fixes like wing vortillons and vortex generator tabs.
Anyway, as a result of requiring a margin between stalling the nose surfaces before the main surfaces, the overall maximum lift coefficient is reduced. I think that for a given wingloading, the turning capability and field performance is slightly reduced.
With FBW and relaxed static stability, I think these issues are non-existent.
Returning to the XP-55 - getting it right was probably hindered by the lack of experience with the configurations. However, later designs benefitted from the (mostly negative) experience gained with it.

 

[saturncanuck]

Here you go Stargazer....

The camera is a Canon 20D. I shot these on a tripod using a trigger and aperture priority. If there were hard shadows in the image, I'd handhold a flash and use it while the shutter is open. Lighting in this hangar was pretty even (though the main display building takes cues from the bat caves of the USAF Museum!).

Enjoy the Day! Mark

They spelled it wrong. Shouldn't it be "Ass-Ender"?

 

[Stargazer]

Wonder how yoy managed to NOT get it renamed "donkey-ender", as this happened to me recently on this very forum... the quotes, maybe? The capitals? Anyway... Yeah, "Ass-Ender" was the inhouse nickname for the aircraft at Curtiss-Wright... well, for obvious reasons... LOL

 

[elmayerle]

Sorry Stargazer, but my money's on Evan.

Thanks for the vote of confidence. For the configuration tested and flown, it badly needed a stability augmentation system and iin the course of the semester-long Stability and Control course, it was my "project aircraft" to at least develop a first approximation of the control laws such a system for that aircraft would require. It was a most interesting course.

 

[memaerobilia]

Here is the C-W viewpoint:
From the Curtiss-Wright Company file on the Ascender:
In an original, typewritten report (not a copy) with heading, “Development of Unusual, Experimental Fighter Plane Design."

“Advantages claimed for the tail-first aircraft of this type are; speed equal to or greater than conventional design airplanes of the same horsepower; improved longitudinal control and maneuverability; improved forward visibility and search view; it is Quieter, because the engine is behind the pilot; guns being clustered in the nose of the plane, fire straight ahead and need not be synchronized to fire through the propeller, nor need their rate of fire be limited; increased rudder effectiveness for recovery from spins; less danger to pilot from fire in the engine; better handling characteristics on the ground; better handling characteristics at very high speed because the elevators…being in front… are removed fom the compressibility wake of the wing.” It was first flown at Scott Field, Illinois, July 13 1943, several other flights were made at Lambert Field, St. Louis Illinois.
Another interesting feature, I had not remembered, was that the Ascender “has a “kickoff” control on its Curtiss Electric three-blade constant speed propeller so the pilot may jettison the propeller in event of an emergency jump.”

 

[memaerobilia]

I think I finally figured out how to attach photos directly from my files (instead of a photobucket link). so I can finally start posting some images. Here is a first generation original company photo of the Flying Model 24 b from the C-W files.. (I hope). Note the difference from post # 1 in this thread, taken from the opposite end. This one has full wheel fairings, so I assume a fixed gear.

 

[Stargazer]

Beautiful picture! I'd never seen a front view of the 24B. Are you keeping the photos small on purpose? If not, I think you should at least double the size! 400 pixels wide is a bit small to appreciate all the details. Anyway it's really nice that you can contribute to this thread!

 

[Mark Nankivil]

Greetings All -

A few more XP-55 images....

Enjoy the Day! Mark

 

[mz]

There's no fundamental difference in a canard, a tandem wing or a regular configuration. Greatly simplified, in each, the basic secret to pitch stability is that the fore surface must be at a higher set incidence than the aft.

This often means that in a canard aircraft, you can't have high max lift (read large flaps) in the larger main wing - which is why canards suck at landing.

Here's an illuminating graph (that takes quite a while to understand), from Stanford or MIT, I forget.

 

[ninjrk]

Hope these might be of use, I was fortunate enough to volunteer at the Air Zoo when they were working on her.

Matt

 

[ninjrk]

 

[Stargazer]

This is FANTASTIC!!! One of my all-time favorite experimental types is back in top shape... and there is hope I might even be able to see it one day... Where will it be on display?

 

[ninjrk]

It's on display at the main building of the Kalamazoo Air Zoo in Kalamazoo Michigan. IIRC, he agreement is that they keep it indefinitely until the NASM wants it back. It was fascinating to watch it come back together. The exterior paintwork was completely redone under the direction that every mark had to be exactly reproduced, so they did stencils of the entire plane so the markings are at the same cock-eyed angles that some airman sprayed on 60+ years ago. I got a laugh out of spending over a month making exact positional templates for markings that had been obviously slapped on with minimal care originally. The cockpit, all interior surfaces, and wheelwells were allowed to be cleaned but not touched up at all, so the zinc oxide you see is the original paint. What I thought was cool is that the grease pencil marks from the original engineers cover those surfaces and remain intact, I think you can see some in the wheelwell pic up above.

Matt

 

[The Artist]

This is FANTASTIC!!! One of my all-time favorite experimental types is back in top shape... and there is hope I might even be able to see it one day... Where will it be on display?

Has there been any talk of flying it again? My understanding has been that the Smithsonian's policy is that when an aircraft comes into their collection it will never be flown again.

 

[ninjrk]

Not that I'm aware of, I know we kept everything inside as is except for cleaning, so nothing below the fuselage skin has been worked on. I would imagine there's no real chance it will ever fly again, especially as it's the last of its kind and could never be replaced.

Matt

 

[ninjrk]

Oh, and minor fun fact? The housing over the top intake? It's balsa wood and pine carved to shape. That's the original part, BTW.

Matt

 

[Johnbr]

I have wondered how it would do with a jet engine in it.

 

[Stargazer]

I guess this is what many of us have wondered about this aircraft for a long time... but we'll never know!

 

[airman]

but last image of first page with P.286-17 is it a jet variant of Xp-55 ? ???

 

[Justo Miranda]

Goblin engine

 

[ninjrk]

Somewhere I've got photocopies of the technical documents NASM provided but there is a short Curtiss memo that they contemplated the possibillity of a jet engine but it would have required a complete redesign of the fuselage and was never pursued. I tried to follow up on my own with Curtis-wright but they sadly destroyed all of the materials they'd had from their aviation days except for a bare handful that were destroyed by a pipe bursting. Their archivist was most pleasant and helpful but the stuff is long gone.

Matt

 

[saturncanuck]

This is FANTASTIC!!! One of my all-time favorite experimental types is back in top shape... and there is hope I might even be able to see it one day... Where will it be on display?

Has there been any talk of flying it again? My understanding has been that the Smithsonian's policy is that when an aircraft comes into their collection it will never be flown again.

Yes, this is true. Their policy is to restore the aircraft to its factory fresh condition and preserve it for future generations. The engine is laquered to maintain its longevity, so, these aircraft will never fly again. That said, the NASM did not restore the Ascender (aka Ass-Ender)

 

[ninjrk]

Yes, this is true. Their policy is to restore the aircraft to its factory fresh condition and preserve it for future generations. The engine is laquered to maintain its longevity, so, these aircraft will never fly again. That said, the NASM did not restore the Ascender (aka Ass-Ender)

Actually, while the NASM didn't do the restoration the Air Zoo is one of the few places outside that the NASM contracts to do restorations, so we had to follow their guidelines exactly to maintain the restoration in accordance with their policies. I believe the airframe arrived with the engine already sealed up, I don't recall ever seeing the fuselage open to expose it.

Matt

 

[saturncanuck]

Yes, this is true. Their policy is to restore the aircraft to its factory fresh condition and preserve it for future generations. The engine is laquered to maintain its longevity, so, these aircraft will never fly again. That said, the NASM did not restore the Ascender (aka Ass-Ender)

Actually, while the NASM didn't do the restoration the Air Zoo is one of the few places outside that the NASM contracts to do restorations, so we had to follow their guidelines exactly to maintain the restoration in accordance with their policies. I believe the airframe arrived with the engine already sealed up, I don't recall ever seeing the fuselage open to expose it.

Matt

Thanks, Matt, for clearing that up. BTW, she looks gorgeous!!!!!!

 

[Sundog]

Beautiful pictures all. For those of you wondering about all of the fuss with canards, here is a good reference article for you.

Canards: design with care (page 1)
Canards: design with care (page 2)
Canards: design with care (page 3)

 

[Triton]

Photograph of Curtiss Ascender prototype from 1943 found on eBay.

URL: http://cgi.ebay.com/CURTISS-XP-55-ASCENDER-TAILLESS-PROTOTYPE-42-78846-1943-/310242802223?pt=LH_DefaultDomain_0

Seller's description:

Perfect Curtiss-Wright 8 X 10 black and white photo of the second prototype P-55 tailless pusher canard, 1943.

 

[Stargazer]

Okay, so now I'm home and I can access my files. Lockheed worked on two distinct canard combat projects: the first one was the L-133, a stainless steel twin-engine jet fighter, and the L-137, a high-altitude bomber project competing for Type Specification XC-124 against the B-27 and B-28 (not to be mistaken with the L-129, competing for the same spec but with a conventional configuration). The L-137 was also called the Model 30 and is portrayed in the various attached pictures. I believe the artwork you found is another take on that selfsame project.

Just realized I made a mistake here, as this should read XC-214... :-[

 

[Rubber Rookie]

OK, I realize that I'm coming into this discussion way late, but I've always loved the look of the XP-55. My question is what lead Curtiss to go with swept wings? As far as I know, few if any American engineers knew of the benefits of swept wings (as far as trans-sonic speed is concerned). Was it to help move the CG back?

I still plan on building my own XP-55 rubber powered free flight model some day. Need to vastly improve my building skills first.