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GOT: The Curtiss-Wright XP-55 Ascender


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#1 Romantic Technofreak

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Posted 16 December 2016 - 10:51 AM

Hi friends,

 

when Wikipedia continues becoming better, it may be not easy to write a satisfactory GOT topic about an aircraft, because Wikipedia already contains everything one would like to know. But in this case, it turned out that (about an American aircraft!), the German Wikipedia are more extensive than the one in English language. So I decided to translate the German text for you, one more feature you have exclusively as Warbirdsforum user! (I hope not too many germanisms occur...)

 

 

The Curtiss XP-55 Ascender

 

(internal designation CW-24) was an experimental fighter aircraft of the US producer's Curtiss-Wright's Curtiss Airplane Division St. Louis. It was a very unconventional design for a pursuit aircraft, which should meet the demand for the best possible visibility for the pilot while maintaining low air resistance and high firepower. The XP-55 reached the second place in the competition, this being a long distance behind the XP-54. The CW-1 to CW-25 series was only used by the Curtiss-Wright plant in St. Louis between 1930 and the beginning of the Second World War.

 

 

Concept Development

 

Basis for the development of the XP-55 were the requirements of the on 14 or 27 November 1939 published Circular Proposal XC-622 (also called Air Corps Type Specification XC-622). There the following performance values were required: ascent to 6100 m (7000 mph) in 7 minutes, a speed of 680 km/h (425 mph) in 4600 to 6100 m (15,000 to 20,000 ft), the top speed should be 840 km/h (525 mph, his was considered a theoretical limit for propeller aircraft) and at least 1.5 hours of flight. The deployment should be possible from an unprepared 915 m (3000 ft) long runway surrounded by 15 m (50 ft) high obstacles. On February 20, 1940, these requirements have been added by the Request For Data R40-C. To make the ambitious flight performance possible, the US Army Air Corps (USAAC) favored the Pratt & Whitney X-1800, other sources [1] say, this was the Pratt & Whitney H-3130 delivering 1800 hp, which at later stages of development should be increased to 3000 horsepower. The demands in R40-C differed from the usual requests of the War Department to airframe manufacturers in a way that here it was directly asked to draw up draft outside the previous conventions.

 

The Air Corps chose five concepts (Bell XP-52/XP-59, Vultee XP-54, Curtiss XP-55 and Northrop XP-56) for the subsequent development, later the XP-67 came added as a sixth pattern. The works were followed up to different development stages, but only three designs led to flying machines [I mean only the XP-52 never flew, RT].

 

The Curtiss Airplane Division of Curtiss-Wright in St. Louis submitted proposals for an aircraft with three potential engine alternatives. The Army chose to use P-249C with a Continental IV-1430-3 delivering 1600 hp and counter-rotating airscrews. The P-249C had a pusher propellers, swept wings fastened far aft, and end discs attached to the tips of the surfaces as side rudders. The freely movable stabilator at the bow gave the design the look of a canard airplane. However, these are defined by an on the bow fixed rudder fin with elevator contrary to the XP-55 design. Here, the joystick was connected with trimming surfaces at the rear edge of the elevator. These were only activated at the take-off, during the flight the area could turn freely. The foreseen armament, concentrated in the bow, consisted of a 0.30-cal machine gun, two 0.50-cal machine guns and a 37-mm machine gun. The span should be 9.85 m and the length should be 7.78 m.

 

The contract for the construction and first wind tunnel tests for the XP-55 (Model CW-24) was signed on 22 June 1940. Curtiss ensured the high performance requirements of the XC-622 and R40-C, although until then only paper studies were carried out. The wind tunnel results showed poor flight stability and inadequate control characteristics, particularly when approaching the stall speed. The necessary construction work to remedy these grievances would certainly have influenced the performance, so that the Air Corps delayed the further commissioning of Curtiss.

 

 

Experimental aircraft CW 24-B

 

Then the plant decided to continue the work on its own cost and to create a full-scale flyable proof-of-concept model for generating additional flight data. This model, called 24-B experimental aircraft, was in the last stages of construction, when Curtiss on 28 November 1941was able to conclude a new agreement with the Air Corps for the continuation of the project.

 

The CW 24-B had a load-bearing fuselage structure made of fabric-covered welded steel tubes. The wing with a span of 11.16 m was carried out in timber construction, the sweep of the t/4-line was 26.5 °. The length was 8.36 m and the flying weight was 1640 kg. Unlike in the original P-249C design, the vertical rudders at the 24-B were attached at about half the span. The outer areas of the surface areas showed a considerable wash-ou to reduce the tendency to stall. The cowled chassis was not retractable. The crew consisted of a pilot and an engineer. However, with a Menasco C6 S-5 Super Buccaneer delivering 275 hp to drive the plane, it was underpowered and only reached 290 to 320 km/h as the maximum speed.

 

The CW 24-B (USAAC serial no. 42-39347) flew for the first time on 2 December 1941 at the Muroc Army Air Field . In the test flights, the surface area of the front wing was increased by 25% and the vertical rudders were shifted outwards by 1.20 m. As a result, these surfaces were located as end discs on the wing tips and were supported by two low fins above and below the engine cowling. Later, surface extensions were installed outside the end disks to increase the longitudinal stability. By May 1942, 169 flights had been carried out. At the beginning, spinning experiments were not performed because experiments in a vertical wind tunnel with a model of the CW 24-B in 1:16 scale gave results of an uncontrollable flat spinning behaviour. The CW 24-B then was brought to Langley for own wind tunnel tests.

 

 

XP-55

 

On July 10, 1942, the Army ordered three XP-55 prototypes. Since the originally forseen engine was not available, Curtiss planned to use the Allison V-1710-F16 with 1250 hp, which had been originally intended for the design P-249A. As a result, Curtiss guaranteed the top speed of 670 km/h in 5900 m, a climb of 7.1 min to 6100 m and one hour as the maximum flight time.

 

After Don Berlin had been responsible for the design work, the following construction work was performed by George Augustus Page Jr. as chief engineer and E. M. "Bud" Flesh as chief designer. The interpretation of the XP-55 was strongly oriented on the CW 24-B. The wings with a sweep of 28 ° on the t/4-line (45 ° at the wing front edge) had ailerons and split flaps. The vertical fins above and below the engine were equipped with air inlets for cooling the engine compartment (top) and a heat exchanger (bottom). The propeller shaft also drove a blower for forced cooling. At the outer load stations two additional tanks with 190 L each could be carried. The 3.05 m diameter three-blade propeller could be blown off by means of compressed air in case of emergency for the pilot's exit in flight.

 

After an inspection of the dummy finally the 1275 hp delivering Allison V-1710-95 (F23R) without turbochargers and a smaller fuel capacity was chosen. The weight increased by 40% compared to the original concept of 3600 kg. The armament in the final version consisted of four .50 cal-MGs.

 

The roll-out of the first prototype (USAAF series 42-78845) took place on 26 June 1943. After taxiing tests, the first flight took place on the 13th or 19th of July 1943 (depending on the source) on Scott Field, located near the Curtiss works. The flight test revealed some problems of the XP-55. Thus, for example, very long take-off distances were required, which should be remedied by an enlargement of the elevator. The engine tended to overheat on the ground despite various changes in the air inlets. Inboard of the ailerons boundary layer fences were installed to improve the flow pattern on the wings at high angles of attack. Continued test flights on Lambert Field showed generally good flight characteristics, but on November 15 at stall testing the machine crashed. The behavior of the aircraft during the crash resembled the phenomenon of stable vertical flatspinning, which had already been observed during the model spinning tests in the wind tunnel. The test pilot J. Harvey Gray could leave the plane.

 

As a direct result of the crash a new series of wind tunnel investigations began, which led as a result to an increase in the span by attaching trailerons, connected to the ailerons. This change was directly adopted in the third machine (42-78847), which was still under construction. The second aircraft (42-78846) flew for the first time on 9 January 1944, followed by the third prototype on 25 April. This one soon continued the interrupted stalling tests, whereby it was found that a stall warning practically did not exist and the machine suddenly fell off and only could be brought under control after a loss of height by more than 1000 m. The subsequently installed pressure sensor, which activated a stick shaker, was one of the first artificial stall warning systems in an aircraft. A simple solution for the high loss of height in the stall could not be found.

 

The second prototype also received the modifications of the third sample in the autumn of 1944. Although the test pilots described many good features of the second machine, they also complained that many changes had yet to be made until they were ready for production. After the third plane had been transferred to Wright Field in mid-December 1944, it crashed there on May 27, 1945, with a pilot and a civilian killed on the ground [other sources say 4 victims, due to English Wikipedia].

 

 

Development end

 

For the army decided to consider the stall characteristics of the Ascender, including the warning system, as unacceptable, in addition to the other unresolved deficiencies, such as the long take-off, excessive weight and cooling problems, at the end of 1944 this led to the discontinuation of any further development. Until then costs of about 3.5 million US dollars had accumulated.

 

 

Construction

 

The XP-55 has canard wings and a pusher propeller, which at its time was a very unconventional construction. The engine was behind the cockpit and the rear edge of the wing. This was one of the reasons for their strong sweep. The wings had ailerons and landing flaps, and carried the vertical rudders as well as, which each rose upwards and downwards just before the ends. The elevator, built as a mass-balanced stabilator with equidistant deflecting auxiliary rudders, sat at the front of the bow. The chassis was, for the first time at the company, designed as a tricycle landing gear with single wheels on each strut. Since the originally planned engine Pratt & Whitney X-1800 was not available, the three aircraft received 12-cylinder engines Allison V-1710.

 

End of German Wikipedia text. The following paper sources are given:

  • William Green: Fighters (War Planes of the Second World War, Volume Four), MacDonald, 3. Auflage 1965, ohne ISBN, S. 62-65
  • Bill Gunston: Curtiss Ascender (Prototype Pusuits). In: Aeroplane Monthly November 1979, S. 580-583
  • Peter M. Bowers: Curtiss Aircraft 1907 - 1947, Putnam, 1979, ISBN 0-370-10029-8, S. 466-469
  • Francis Allen: Ascent -Tail-First (Curtiss-Wright XP-55 Ascender). In: AIR Enthusiast Fifty-One August-Oktober 1993, S. 10-15
  • Bill Norton: U.S. Experimental & Prototype Aircraft Projects - Fighters 1939-1945, Specialty Press, 2008, ISBN 978-1-58007-109-3

 

One of the prototypes (#2) survives in the Kalamazoo AirZoo museum.

 

Now, let's look at some pictures (they can be improved by using XnView, like always):

 

The CW-24-B (sorry, forgot to store the source), the mechanic's compartment is clearly visible:

3137616536333931.jpg

The CW-24-B in the Langley windtunnel (from Wikipedia):
6337653964386538.jpg

Contemporary XP-55 pictures. This one roames around in the net:
6234376364313433.jpg

From avionslegendaires.free.fr:
3037386430306433.jpg

 

Source not stored again. The ground looks being a bit askew:
3031393634396163.jpg

Busy work. From the website of the German magazine Fliegerrevue:
1280_6436306638613736.jpg

 

Then modern pictures from Kalamazoo. Here source given:
3966626466663335.jpg

From skytamer.com:
1280_3766333934343964.jpg

Also from skytamer.com:
1280_3736643734656261.jpg

From recreationalaviation.blogspot.de:
6136656662653035.jpg

 

(to be continued)


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#2 Romantic Technofreak

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Posted 16 December 2016 - 10:54 AM

(continued from above:)

 

Close-up from cybermodeler.com:
3335306561343861.jpg

Also close-up from cybermodeler.com:
6666316532393735.jpg

 

 

Hope you enjoyed, and best regards,

RT


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#3 Armand

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Posted 16 December 2016 - 02:34 PM

Hi friends, when Wikipedia continues becoming better, it may be not easy to write a satisfactory GOT topic about an aircraft, because Wikipedia already contains everything one would like to know. But in this case, it turned out that (about an American aircraft!), the German Wikipedia are more extensive than the one in English language.

A little addition around the infamous Wiki':
Once I mentioned the Danish sailor Jesper Bank, who is born in My hometown. He is Olympic medalist and double -champ with multiple international medals too and to avoid wrong information about such specific details as what/where I chosed to check the Danish Wikipedia, wich I generally have excluded due to unsufficient contains, but even at this national subject did the Danish Wiki' fail :-o
As sceptic of the 'interrest' of this Danish subject on the English Wiki' I wasn't dissapointed by the likely thin information on the English site.
However a little desperate for the medal-details of the local hero I found the need of Googeling the subject - And was shown the German Wikipedia as first hit :-o This was not without reason as I there found a thoroughly article about Jesper Banks achievements :-o

#4 Rick65

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Posted 17 December 2016 - 09:08 AM

Some great photos.

I am surprised not to see a mention of what was supposedly the the plane's very appropriate nick name, the Arse ender.

As seemed a habit for the company Curtiss managed to create a very 1930s looking plane that existed in the 40s and performed below their expectations.


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#5 Wuzak

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Posted 18 December 2016 - 12:10 AM

After taxiing tests, the first flight took place on the 13th or 19th of July 1943 (depending on the source) on Scott Field, located near the Curtiss works. The flight test revealed some problems of the XP-55. Thus, for example, very long take-off distances were required, which should be remedied by an enlargement of the elevator. The engine tended to overheat on the ground despite various changes in the air inlets. Inboard of the ailerons boundary layer fences were installed to improve the flow pattern on the wings at high angles of attack. Continued test flights on Lambert Field showed generally good flight characteristics, but on November 15 at stall testing the machine crashed. The behavior of the aircraft during the crash resembled the phenomenon of stable vertical flatspinning, which had already been observed during the model spinning tests in the wind tunnel. The test pilot J. Harvey Gray could leave the plane.


Inverted flat spinning.

Apparently when the crash happened the aircraft flipped on its back, the engine stalled out and there was no forward momentum, so the flight controls were of no use. The pilot escaped after falling several thousand feet.
 
Curtiss_XP-55_following_crash.jpg
Curtiss XP-55 following crash [No restrictions or Public domain], by http://www.flickr.co...in/photostream/, from Wikimedia Commons
 

The second prototype also received the modifications of the third sample in the autumn of 1944. Although the test pilots described many good features of the second machine, they also complained that many changes had yet to be made until they were ready for production. After the third plane had been transferred to Wright Field in mid-December 1944, it crashed there on May 27, 1945, with a pilot and a civilian killed on the ground [other sources say 4 victims, due to English Wikipedia].

 
The crash happened at an air show celebrating the end of the war.
 
The XP-55 hit a car on a road near to the show, killing the driver at least.
 
I can't find my reference to confirm the total.
 
 

 

6234376364313433.jpg


Note the addition of wing fences.

#6 Wuzak

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Posted 23 December 2016 - 11:49 AM

The crash happened at an air show celebrating the end of the war.

 
The XP-55 hit a car on a road near to the show, killing the driver at least.
 
I can't find my reference to confirm the total.

 

The event was the Seventh War Bond Rally at Wright Field. There were an estimated 100,000 - 200,000 spectators that day.

 

The pilot was Captain William C. Glasgow, a veteran of 80 combat missions over Europe. 

 

Each aircraft in the show was to make a pass during which a slow roll would be performed and its course resumed. Glasgow had completed his first roll when the aircraft flicked to the left than to the right before entering into an inverted dive to the ground. Glasgow was killed in the crash.

 

As the aircraft crashed it hit a car on the airfield's perimeter road. The occupants were the driver, his wife and their two children, one an infant, and a friend. The driver had just asked a policeman directions to the entrance to the field and was turning his car around when the aircraft hit. The plane burst into flames, enveloping the car. 

 

 

The driver and his wife escaped the car by themselves, the driver collapsing soon after. Passers-by rescued the children and the friend from the car. The driver later died from his injuries, but the others survived with varying degrees of burns.

 

The XP-55 had also broken off the radio aerial from the policeman's patrol car, while metal fragments from the crashing plane broke his wind screen.



#7 Wuzak

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Posted 23 December 2016 - 11:53 AM

After taxiing tests, the first flight took place on the 13th or 19th of July 1943 (depending on the source) on Scott Field, located near the Curtiss works. The flight test revealed some problems of the XP-55. Thus, for example, very long take-off distances were required, which should be remedied by an enlargement of the elevator. The engine tended to overheat on the ground despite various changes in the air inlets. Inboard of the ailerons boundary layer fences were installed to improve the flow pattern on the wings at high angles of attack. Continued test flights on Lambert Field showed generally good flight characteristics, but on November 15 at stall testing the machine crashed. The behavior of the aircraft during the crash resembled the phenomenon of stable vertical flatspinning, which had already been observed during the model spinning tests in the wind tunnel. The test pilot J. Harvey Gray could leave the plane.


Inverted flat spinning.

Apparently when the crash happened the aircraft flipped on its back, the engine stalled out and there was no forward momentum, so the flight controls were of no use. The pilot escaped after falling several thousand feet.


The pilot fell 16,000ft inverted before he was able to escape the aircraft.
 

The plane missed a framhouse by about 100 yards (91.4m).



#8 GregP

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Posted 25 December 2016 - 08:42 AM

I wonder how it might have performed had it used an engine with the power it was actually designed for.

 

It certainly wasn't the first aircraft to fall into that category. The F-14 comes quickly to mind ... designed for two 30,000 lbf engines but early units (pre-D) had 20,000 lbf engines installed. The Cutlass also comes to mind with underpowered Westinghouse turbojets and a very high crash rate. Westinghouse promised 10,000 lbf in afterburner and delivered 6,100 lbf. Ergo, way underpowered for what was expected.



#9 Wuzak

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Posted 25 December 2016 - 12:59 PM

I wonder how it might have performed had it used an engine with the power it was actually designed for.

 

The XP-55 was to use the IV-1430, so the substitution of the V-1710 didn't change much in power terms.

 

The main problem with the XP-55 was the airframe.



#10 GregP

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Posted 26 December 2016 - 06:31 AM

When I first read about it some 45 years ago, it was said at the time that it was originally designed for some 1,500 HP at a considerably lighter weight. What it got was a less HP and heavier weight, making it a bit underpowered when compared with the original design. And we all know that canards are very susceptible to flying characteristic degradation with weight and power going the wrong way. Ask any VariEze owner about weight and power. Better yet, ask Burt Rutan.

 

My original post above stands, I wonder what it might have flown like if it had the power it was originally designed for?

 

Nobody in here or else where can answer that one, Wayne, except to say it would have had a better power-to-weight ratio and would have been a bit lighter and more powerful. Whether or not that might have made some of the situations it got into more recoverable or not is certainly debatable (not that I want to debate it), and I don't suggest anything one way or the other in here.

 

But I HAVE seen an RC version of it fly just fine and very fighter-like, with decent stall manners.

 

Of course, we all know that an RC tends to have a MUCH better power to weight ratio than a full size aircraft, and it is likely that the RC version alos had a bit more control throw and possibly control area, though it DID look pretty stock. Still, I didn't exactly measure it, just watched it and appreciated seeing it fly. It didn't look squirrely in the least bit. I have NO idea of the airfoils were anywhere NEAR realistic and I seriously doubt it.

 

Not intended as a start of discussion on it, just wondering more or less out loud.


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