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Vultee XA-41

USA flag United States of America (1944)
Prototype Ground Attack Aircraft – 1 Built

XA-41 in flight

The Vultee XA-41 was a single-engine aircraft that began life as a dive bomber. Months later, its role was changed to a low-level attack aircraft. The XA-41 performed admirably in flight tests, but the United States Army Air Corps (USAAC) eventually decided that the fighter aircraft then in service were already performing well enough in the attack role. Despite its job being erased, the XA-41 continued development as a testbed, showing off the powerful XR-4360 engine it mounted and how much it could carry. The aircraft itself would have been deadly had it been produced in large numbers, as it boasted four 37mm cannons. As the war went on, the XA-41 was still being tested. Throughout the trials, the aircraft had extremely good performance, even being able to outturn a P-51, but its speed wasn’t quite enough for its role. At one point, it was given to the Navy for testing and eventually it would wind up at Pratt & Whitney (PR). At PR, it served as a testbed through the war and was eventually scrapped in 1950.

History

Cutaway Concept for the XA-41

The XA-41 began as part of a United States Army Air Corps (USAAC) requirement in October 1941 for a new single-seat attack aircraft. The Douglas A-20 Havoc (and soon to be produced North American A-36 Apache) was performing well at the time, but the USAAC wanted something new. The aircraft requested had to be able to reach at least 300mph (482.8kph) at sea level, have a service ceiling of at least 30,000ft (9,144m), and a range of 1,200 miles (1,932km). For the attack role, the aircraft was to have either 37mm, 20mm, or 50. cal guns mounted in the wings. Given this imposing armament, it is likely the aircraft would have attacked soft targets or even been used for tank-busting.

The USAAC commissioned Vultee Aircraft Corporation, Kaiser Fleetwings, and Curtiss to design a new aircraft for the role. Kaiser Fleetwings developed the XA-39, which would have mounted the R-2800-27 engine. Their aircraft didn’t progress beyond the mockup stage. Curtiss reused their naval XTBC-1 prototype for their part, renaming it the XA-40. This also didn’t go beyond the mockup stage. Vultee’s answer was the V-90, a ground attack aircraft mounting the fairly new and powerful R-4360 engine. Interestingly, the XA-41 started off as a dive bomber, despite it being commissioned as an attack aircraft. It isn’t often stated, but the Army had been interested in dive bombers since 1940, going as far as purchasing several Navy designs. The Army bought several SB2D-1 Helldivers in December of 1940 and renamed them the A-25 Shrike. They also had a troubled history with one of Vultee’s own aircraft, the A-35 Vengeance, which they tried numerous times, but to no avail. The XA-41 was most likely a chance for the Army to have a successful dive bomber or attack aircraft. The Army was satisfied with Vultee’s V-90 design and awarded a contract for two prototypes on November 10, 1942. Shortly after a mockup inspection, the Army interestingly switched the role from a dive bomber to a dedicated attack aircraft. The switch was rather abrupt and caused a delay in the development.

XA-41 Prototype

On April 30th, a new contract was signed which included a static mockup. Vultee continued construction on the project until the prototype was halfway completed, at which point the Army decided that the most current aircraft, the Republic P-47 Thunderbolt and North American P-51 Mustang, were already quite capable in the attack role. But this wouldn’t be the end of the XA-41. Maj.Gen Oliver P. Echols, Chief of the Material Division, opted not to cancel the program and instead complete it in order to show the true potential of a new attack aircraft with the new R-4360 engine. This decision went through on November 20th, with the prototype ¾ the way through completion. The 2nd prototype was cut at this point and only one would be built (Serial No. 43-35124/5).

On February 11th, 1944, the XA-41 flew for the first time from Vultee Field, California, with test pilot Frank Davis at the controls, and landed at March Field, California. Several flights after this were conducted at the nearby army base. The aircraft was flown by both Vultee and Army pilots, and both agreed it handled well. There were some problems here and there, which Vultee quickly fixed with some additions to the airframe. On June 25, the Army accepted the XA-41. On July 16th, on its 60th flight, the aircraft was ferried to Eglin Field, Florida. Testing proved the XA-41 was an exceptional aircraft, with many great features. The craft had an excellent turn rate, being able to outturn the P-51. For its size, it carried an impressive arsenal of weapons. But the Army wanted an attack aircraft that could also defend itself if the need would arise, and the 350mph (563.2 km/h) of the XA-41 wasn’t that impressive compared to other aircraft in service. The United States Navy became interested in the XA-41 at some point and the prototype was given to them for testing at Patuxent River, Maryland. The Navy wanted to see if the aircraft could be flown from aircraft carriers. After the Navy briefly tested it, the XA-41 was given to Pratt & Whitney (PR) on August 22, 1944. It was obvious at this point that the XA-41 would never see combat, but would remain in the US as a testbed aircraft. Serving with PR, it was used as a flying testbed for their R-4360 engine, as well as having a supercharger mounted. As testing continued, the aircraft was purchased by PR on October 9 and re-registered as NX6037N. There are few documents that reference the XA-41 post-war. The only thing mentioned is that the sole XA-41 was finally scrapped in 1950, having served for many years at PR.

Design

The XA-41 was a conventional single-engine aircraft. It had a slight gull wing and a tail sitter configuration. The landing gear in the wings would retract inboard and was placed widely to allow better landing performance. During development, the tail wheel had doors installed to completely cover it in-flight. The cockpit was placed far forward and raised to allow the pilot to see over the engine, giving him better visibility when attacking ground targets. The ventral tail had an extension that spanned most of the length of the aircraft. This was added during development. A spinner was also added at some point. The XA-41 mounted the PR XR-4360 Wasp Major engine, which was the main reason the Army and PR were so interested in the project.

For armament, the XA-41 had four M2 Browning .50 cal machine-guns mounted in the wings. For the attack role, it was meant to mount four more 37mm cannons (sources don’t mention what particular kind of gun) in the wings. All armament in the wings was placed outside of the propeller’s range. For bombing, the XA-41 had a bomb bay that could carry four 500Ibs bombs, a torpedo, additional fuel, or two 1,600Ibs weapons. In total, it had up to 6,500Ibs of ordnance. Documents mention that up to 1,100Ibs of additional bombs could be mounted to the wings. The aforementioned competing XA-39 only sported the four Brownings, two 37mms, as well as a predicted carrying capacity of six 500Ibs bombs.

Variants

  • XA-41 – [The sole prototype built, used as a testbed for the XR-4360 engine.]

Operators

  • United States of America – The United States Army Air Corps would have operated it had it entered production. After serving as a testbed for the Army, the Navy and Pratt & Whitney also did tests with the aircraft.

XA-41 Specifications

Wingspan 54 ft / 16.4 m
Length 48 ft 7 in / 14.8 m
Height 14 ft 5 in / 4.4 m
Wing Area 540 ft² / 164.5 m²
Engine 1x 3,000 hp ( 2240 kW ) XR-4360-9
Propeller 1x 4-bladed Hamilton Standard propeller
Weights
Empty 13,400 lb / 6078.1 kg
Gross 18,800 lb / 8527.5 kg
Maximum 23,359 lb / 10595.4 kg
Climb Rate
Rate of Climb at Sea Level 2,326 ft / 708.9m per minute
Maximum Speed 353 mph / 568 kmh at 15,000 ft / 4572 m
Cruising Speed 270 mph / 434.5 kmh
Range 800 mi / 1287.4 km
Maximum Service Ceiling 27,000 ft / 8229.6 m
Crew 1 pilot
Armament
  • 4 Browning M2 machine guns (400rpg)
  • 4 37mm cannons (30rpg)
  • Up to 6,500 Ibs of weapons

Gallery

llustrations by Haryo Panji https://www.deviantart.com/haryopanji

Vultee-XA-41 Original Prototype Colors
Vultee XA-41 with possible service markings (artist interpretation)
XA-41 at Patuxent River
XA-41 on the runway
XA-41 in a slight climb
XA-41 parked on the ramp

Sources

 

Douglas XTB2D-1 Skypirate

usa flag USA (1945)
Prototype Torpedo Bomber – 2 Built

XTB2D-1 on the Runway
First prototype of the Skypirate on the runway.

The Douglas XTB2D-1 “Skypirate” was a large, single-engine torpedo bomber built for use on the Midway class carriers during World War 2. At the time, it was the largest aircraft to be used aboard a carrier, dwarfing even two-engine designs. Unfortunately for the Skypirate, engine troubles, little support from the US Navy (USN), and numerous setbacks with the construction of Midway-class carriers nearly doomed it from the start. By the time it was airworthy, it was trying to fill an obsolete role which other aircraft, such as the TBF/TBM Avenger, already filled adequately. Work continued after the war, with several attempts to revive the program but it proved to be too costly and the Skypirate program was finally cancelled in 1947, with the two prototypes being scrapped in 1948.

History

With engagements such as the Battle of the Coral Sea and the hunt for the Bismarck, the effectiveness of torpedo bombers, such as the TBF/TBM Avenger and Fairey Swordfish, was clear. With the announcement of the large Midway-class carriers, the possibility of a new torpedo-bomber/scout bomber came about. In February 1942, a competition was put forward by the Navy for this role. The Douglas Aircraft Company, based in Southern California, proposed the Skypirate. The single-engine Skypirate was picked from eight different designs, most of which were two-engined. The Bureau of Aeronautics (BuAer) wasn’t expecting a single engine design to be submitted, assuming the specified massive carrying capacity would require a two-engine design. The program was being headed by Ed Heinemann as lead designer and Bob Donovan as the chief engineer, who would be on the project until the end.

XTB2D-1 Frontal View
An impressive look at the massive Skypirate from the front.

In November of 1942, Douglas was given permission to begin production of two prototypes and a mockup of the XTB2D-1 (then called the Devastator II, before being changed to Skypirate). Delays in the development of the Midway class would continue to hamper the Skypirate throughout its life. The finished product was a formidable aircraft, capable of carrying four torpedoes from land or two torpedoes from a carrier, the former being four times the carrying capacity of the TBM Avenger. In March and May of 1943, the mockup was inspected and an order for 23 production aircraft was put in. This was enough for a single squadron to operate from a Midway carrier. Problems began about this time, with the delivery of engines and propellers being delayed. By 1944, the Skypirate was still not airborne and it was obvious it wouldn’t be operational anytime soon. With earlier torpedo bombers performing adequately, a lack of support from the Navy, most of the Japanese fleet in shambles and continued delays with the Midway class (which would eventually sail after the war), the 23 production planes were cancelled. On February 18th, 1945, the first Skypirate was rolled out of the production facility, being completed on March 13th and finally going airborne on May 8th. Neither of the prototypes had any defensive armaments, but they were tested with torpedoes and drop tanks. Although no production was to ever start, the Skypirates would continue flying until the end of the war. During one such flight in June of 1945, a Skypirate was damaged mid-flight, but the craft was brought down safely. Engine problems were a frequent issue with the Skypirate and propeller problems would ground it in August of 1945, not flying again until after the war.

Skypirate Landing
Perhaps the most well known photo of the aircraft, the Skypirate prepares to land.

Postwar, the aircraft industry changed with the introduction of jet aircraft, thus eliminating the need for many prototypes being developed during the war. The Skypirate was no exception. With the torpedo bomber role now fading, the Douglas firm looked at other options to revive their Skypirate. Some ideas included using the Skypirate for an electronic warfare role or even as an anti-submarine aircraft (a role overtaken by another piston engine aircraft, the Grumman AF Guardian), but none of these propositions ever managed to become reality. As the Cold War was just beginning, the Skypirate program ended in 1947 and the 2 prototypes were scrapped in 1948.

Design

The Skypirate is most likely the largest single-engine aircraft to ever be designed for carrier operations. In comparison, the twin-engined B-25 Mitchell medium bomber measured around the same in length and width.

In flight
The 2nd prototype in flight, notice how the tail is shorter in comparison to the first prototype.

The initial Skypirate design had an internal bomb bay, which the prototypes dropped in favor of four external Mark 51 Mod 7 bomb hardpoints. These hardpoints could carry a range of weapons including 500Ib-2000Ib bombs, torpedoes, depth charges, mines or even incendiary bombs. The use of up to 4 Mk.13 Torpedoes (from land) were planned had it entered production. The Skypirate could alternatively carry up to 8,400Ibs of bombs. For offensive armament, the Skypirate had 4 M2 Browning machine guns in the wings. For defense, it had a Firestone model 250CH-3 remote turret behind the cockpit which carried 2 M2 Brownings and a turret in the back of the lower fuselage which carried a single M2 Browning. The lower turret was remotely fired through electronic control and powered hydraulically. Drawings indicate that Mark 2 Gun Containers could be added for extra forward firepower but none were ever attached during testing. 300 gallon drop tanks were also fitted during testing and could have been used had the craft been operational.

The Mockup
The sole mockup made alongside the 2 prototypes.

Along with such an impressive weapons payload, the Skypirate was full of advancements which would have improved its performance. To get such a large aircraft off the ground, the Skypirate was powered by a single Pratt & Whitney XR-4360-8, the largest radial engine ever built up to that time. The engine had a unique exhaust style that combined the exhausts in alternating rows to lower the effects of backpressure. Being a carrier-based aircraft, the Skypirate had folding wings as well as a catapult hook. The inclusion of a tricycle landing gear was also interesting, as it helped with bomb loading and carrier space. Most single engine aircraft of the time preferred using a tailwheel. The Skypirate had large flaps that extended the length of wingspan. The outer flaps served as ailerons while the midsection flaps were used as dive flaps. The dive flaps could also be lowered to help the aircraft cruise or assist in turning to help ease the stress off the aircraft when fully loaded. To assist with bombing or flight in general, a Type 3 Sperry vacuum-controlled, hydraulic autopilot was also to be added. A de-icing system was also added that pumped hot air over the wings and tail section.

The planned modifications of the prototypes are interesting to note. The 2nd prototype (Bu.36934) differed from the first, having a shorter tail of 8.6 ft, compared to the regular 10.5 ft tail of the original design. This was done most likely to conserve valuable space when inside a carrier. Along with these differences, plans to fit a jet engine in the fuselage of the 2nd prototype were made, but nothing ever came to fruition. The first prototype (Bu.36933) had a larger tail and was planned to be converted for the scout bomber role. These plans included adding cameras onboard. As with the jet engine designs, these also never came to be.

Variants

  • XTB2D-1 Bu.36933 – Prototype version, lacked any armament
  • XTB2D-1 Bu.36934 – The 2nd prototype. The tail was shortened to 8.6 ft. Also lacked any armament.
  • TB2D-1 – Proposed production version, 23 were ordered and planned production was to be 100 built every month. These versions were to be fitted with four .50 caliber machine guns in the wings, two in a Firestone power turret and one remotely controlled in the ventral hull. Eventually, the production versions were cancelled in favor of higher priority projects.

Operators

  • United States of America – Slated to be used aboard the Navy’s Midway-class carriers, with the end of the war and other setbacks, the XTB2D-1 was never used operationally.
XTB2D-1 Rollout
The design team poses with the first Skypirate on rollout day.

TB2D-1 Specifications

Wingspan 70 ft / 21.3 m
Length 46 ft / 14 m
Height 22 ft 6 in / 6.9 m
Wing Area 605 ft² / 184.4 m²
Engine 1x 3,000 hp ( 2240 kW ) XR-4360-8
Propeller 1x 8 bladed Hamilton Standard contra-rotating propeller
Fuel Capacity 501 US gal / 1896 L
Oil Capacity 28 US gal / 106 L
Empty Weight 18,405 lbs / 8350 kg
Gross Weight 28,545 lbs / 12950 kg
Maximum Weight 34,760 lbs / 15765 kg
Rate of Climb at Sea Level 1,390 ft / 425 m per minute
Time to 10,000 ft / 3048 m 8.2 minutes (Normal) 10.2 minutes (Military)
Time to 20,000 ft / 6096 m 22.3 minutes (Normal) 26.5 minutes (Military)
Maximum Speed 340 mph / 550 km/h at 15,600 ft / 4755 m
Cruising Speed 168 mph / 270 km/h

312 mph / 500 km/h (with torpedoes)

Range 1,250 mi / 2010 km (Torpedoes)

2,880 mi / 4635 km (Maximum)

Maximum Service Ceiling 24,500 ft / 7470 m
Crew 1 pilot

2 gunners

Armament 4 Browning M2 machine guns mounted in the wings (1600rds)

2 Browning M2 machine guns mounted in turret (1200 rds, incl remote 50.)

1 remote Browning M2 machine guns mounted in ventral hull

4 x Mk 13 Torpedoes (from land)

2 x Mk 13 Torpedoes (from carrier)

2 x 2,100 lbs Bombs

Total of 8,400 lbs payload capacity

2 x Mark 2 Gun Containers

Gallery

llustrations by Haryo Panji https://www.deviantart.com/haryopanji

Douglas XTB2D Skypirate Side View
Douglas TB2D Skypirate Side View – With the Defensive Gun Pod

 

XTB2D End
The last known photos of the Skypirates before being scrapped.
XTB2D Loaded
One of the prototypes with mounted Mk-13 torpedoes.
XTB2D Backside
A back view of one of the prototypes
XTB2D-1 on the Runway
First prototype of the Skypirate on the runway.
XTB2D-1 Frontal View
An impressive look at the massive Skypirate from the front.
Skypirate Landing
Perhaps the most well known photo of the aircraft, the Skypirate prepares to land.
In flight
The 2nd prototype in flight, notice how the tail is shorter in comparison to the first prototype.
The Mockup
The sole mockup made alongside the 2 prototypes.
XTB2D-1 Rollout
The design team poses with the first Skypirate on rollout day.

Sources