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GOT: The Curtiss-Wright XP-55 Ascender


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#11 Wuzak

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Posted 26 December 2016 - 07:59 AM

The IV-1430 was supposed to have 1600hp for the production version, but the flight engines that flew in the XP-49 and XP-67 probably had little over 1000hp.



#12 GregP

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Posted 26 December 2016 - 10:46 AM

Thought so. We all know that modern jet canards wouldn't fly very long without a computer to help out, but the one I saw flying as an RC SEEMED to fly just fine. Maybe he had a pitch axis gyro in it ... I didn't ask. But RC helicopters with gyros fly MUCH better than the ones without them do.

 

I tried a gyro once in an RC pattern plane on the yaw axis and it did a very good job of keeping the plane straight. I stopped only because I'm a dedicated purist (but not snobby about it) and wanted to exercise my own flying skills instead of having it done for me.

 

I'll say this for the yaw gyro ... landing rollounts were a bit straighter than my unassisted rollouts were! I never worried about takeoffs because they were almost all quite straight for me. Pattern planes have a big and effective rudder, great power to weight, and it makes installing retracts easier since there were only two instead of three. I never did build one with a retracting tailwheel and see no reason to unless it is a racer.

 

Cheers and Happy Holidays a bit belatedly perhaps.



#13 Wuzak

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Posted 26 December 2016 - 01:03 PM

I have just been skimming over the handling description in American Secret Pusher Fighters of World War II.

 

It seems I owe the XP-55 some apologies.

 

Static pitch stability was considered normal, dynamic pitch stability required between 2 and 4 cycles to return to trimmed flight depending on the duration of the oscillations.

 

Lateral stability was normal or close to normal when at moderate banking angles.

 

In spiral flight the turn tended to tighten when going to the left but would experience a Dutch roll condition when turning to the right.

 

Direction stability was neutral for small yaw angles and positive for large yaw angles.

 

Control effectiveness was good under normal flight circumstances.

 

Continuous elevator input would produce normal pitching motion, but abrupt elevator movements would induce oscillations, which was considered poor for aerial gunnery.

 

Uncontrolled pitching could occur in rough air.

 

Roll rate was considered average.

 

Most manoeuvres could be performed comfortably, but some were difficult to co-ordinate the controls, particularly for small manoeuvres.

 

The stall characteristics were the downfall of the aircraft. No warning for the stall was given. The stall would cause the aircraft to pitch down and roll to the right, with a change of direction of 135 degrees.

 

If no control input was used to try to recover the stall, the aircraft would enter into a steep dive until speed built up enough for a successful recovery. Altitude loss was about 3000-3500ft.

 

If recovery was attempted the problem was worsened, and 4000ft was lost before recovery.

 

Curtiss tested the aircraft to 390mph IAS in dives.

 

A top speed of 377.5mph at 16,900ft was achieved in testing, climb rate was 2350ft/min at sea level and 2460ft/min at 13,700ft.

 

The engine overheated in ground running, and over-cooled in flight. For landing approach the engine had to be kept at higher power to maintain engine temperature.

 

In landing configuration the stall speed was 106mph IAS.

 

Take-off required 135mph IAS and 3000-3500ft of runway. One of the culprits was the small size of the elevator and the limited angle of attack it could use (17 degrees).


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#14 Wuzak

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Posted 26 December 2016 - 01:07 PM

Also, the XP-55 had what was described as a "free floating elevator".

 

That is, when the pilot wasn't deflecting the elevator it was free to move, to some degree, without his input.



#15 Wuzak

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Posted 26 December 2016 - 01:33 PM

It seems that the XP-55 was about as fast as the similarly powered P-40N, but not as fast as the P-51A or later P-39s.

 

The climb rate was somewhat less as well.

 

Compared the the P-40N, the XP-55 (third prototype) had greater wing span (41ft vs 37ft 4in) but lower wing area (217ft² vs 236ft²).

 

The XP-55 was slightly lighter empty (6354lb vs 6405lb), heavier loaded (7931lb vs 7730lb),and slightly lighter at MTOW (8805lb vs 8860lb).



#16 Romantic Technofreak

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Posted 26 December 2016 - 03:20 PM

Not intended as a start of discussion on it, ...

May I humbly remind you, Greg, that this is exactly what internet forums are intended for? :) (Well, at least I think so...)

 

I have no idea about aerodynamics, but it seems to me canards are/were especially dangerous at low speeds. On Youtube, there is a movie about a XP-55 model. It flies well, but crashes its undercarraige while trying to land (that happens to other RC aircraft too, I admit). Remember, Georg Wulf, Focke's companion, died in 1927 in testing a canard. Maybe it needed Burt Rutan to make them safe.

 

 We all know that modern jet canards wouldn't fly very long without a computer to help out, ...

Isn't that meant about modern flying wings? :huh:

 

Thank you Wuzak for all these additional informations! :rolleyes:

 

Regards, RT



#17 GregP

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Posted 26 December 2016 - 08:10 PM

Actually I meant to say I didn't want to argue about it and did not want to imply that a flying RC represented a good model of a full size aircraft. Let's say non-escalational wording got in the way.



#18 CORSNING

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Posted 26 December 2016 - 08:59 PM

Very nice post #13 Wayne, very nice. You almost make me wish I would start incorporating

experimental aircraft in the AIRCRAFT PERFORMANCE section so that I could include

your post.

True story, Jeff :)


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#19 GregP

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Posted 26 December 2016 - 10:33 PM

Hi RT,

 

Modern flying wings need computer stability enhancements to fly like normal planes, but they don't need them to just fly. Just to fly like "conventionally stable" aircraft. Our Northrop N9M-B Flying Wing has no computer and flies just fine. But it isn't a military fighter.

 

The Typhoon is a canard, as are the Rafale, the J-20, and a few others. Even the F-16 needs a computer to keep the pointy end pointing forward. Most are designed to be statically unstable and have artificial stability built in with computer stability agumentation, many times at 45 - 60 times per second. Not too sure of they NEED that unless they are going to engage in air combat maneuuvering, but the Military fighters must be able to do exactly that, engage in ACM.

 

I am not aware if the Beech Starship had computer-augmented stability or not, but I am under the impression it didn't. I do recall the canard pivoted forward as the speed got slower and/or when flaps came down. The Rutan Varieze ariplanes don't have any computer stability enhancement and fly just fine, though they CAN get upset a bit in rain, stability-wise. I am under the imression that almost all canards of a useful military size and a useful military mission need computer to fly what is considered as "right."

 

Perhaps I am mistaken but, if so, I am unaware of an exception in the military arena. Perhaps not so in the civil or commercial market, but I'd bank on computers in the commercial market, should anyone be so bold as to actually field a canard airliner. If they did, and if there was a fatality, that might be the end of travel on canard airliners after all the bad press gets finished. Not for safety, mind you, but rather in public opinion, after the press and litigation got finished.

 

If lawyers smell money, they don't care a bit about the truth as long as significant money can be recovered from somehwere and put into their pockets. Just personal opinion, but it seems to fit the facts in the real world.



#20 Wuzak

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Posted 26 December 2016 - 11:07 PM

I am under the imression that almost all canards of a useful military size and a useful military mission need computer to fly what is considered as "right."

 

I think all modern military fighter type aircraft need computer control because of the relaxed stability, no matter what the configuration.


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