Vultee Aircraft XP-54 "Swoose Goose

Cockpit

The XP-54 was unique in numerous ways. The pressurized cockpit required a complex entry system: the pilot's seat acted as an elevator for cockpit access from the ground. The pilot lowered the seat electrically, sat in it, and raised it into the cockpit. Bail-out procedure was complicated by the pressurization system and necessitated a downward ejection of the pilot and seat in order to clear the propeller arc. Also, the nose section could pivot through the vertical, three degrees up and six degrees down. In the nose, two 37 mm T-9 cannon were in rigid mounts while two .50 cal machine guns were in movable mounts. Movement of the nose and machine guns was controlled by a special compensating gun sight. Thus, the cannon trajectory could be elevated without altering the flight attitude of the airplane. The large nose section gave rise to its whimsical nickname, the Swoose Goose, inspired by a song about Alexander who was half swan and half goose: "Alexander was a swoose.

XP-54 Flight Characteristics
For its first flight on January 13, 1941, the XP-54 was fitted with Curtiss propeller. The take-off run was excessively long, and the propeller was not considered capable of taking advantage of the power of the engine.

For the second test flight the propeller was changed for a Hamilton Standard 4 blade propeller. Take-off distance was improved by approximately 10%, but it was still over 3,000ft/914m.

Ground handling was considered excellent, owing to the tricycle landing gear.

The overall handling characteristics were considered normal, stability was good about all axes, though some longitudinal instability was found during normal power climbs at 180mph and CoG aft of 28% MAC. Considering that in combat with ammunition expended the CoG could move as far aft as 34% MAC, ballast in the nose would most likely have been required.

Rudder and elevator control was light, and require little trimming fo speed and CoG changes. Aileron forces remained steady at increased speeds, and were relatively light.

Flutter was tested in dives to 460mph TAs in dives and was deemed satisfactory.

Climb tests showed the XP-54 had a sea level rate of climb of 1,620ft/min (8.2m/s), which was not very good for a pursuit type aircraft in 1943.

Staling speed at 18,000lb (8,165kg) was 110mph with the flaps down (10° inner flaps, 30° outer flaps) and 120mph with the flaps up. Lowering the flaps and gear induced a nose down trim change, which was easily controllable.

Approach speed for landing was 140mph IAS, touch down at approximately 115mph IAS. Control during landing was good, and ground run varied between 1,100ft and 1,500ft (335m and 457m).

Performance
Unsurprisingly, the XP-54's performance did not live up to the projections.

Speed measurements were taken with three different surface finishes:

• Factory Finish - Camouflage
• Superfinish - Camouflage
• Superfinish - waxed and polished

Altitude Power Factory Superfinish Superfinish
Setting Finish Camouflage Waxed
Sea Level Military 287 296 304
Sea Level Normal 273 281 289
10,000ft Military 318 327 337
10,000ft Normal 304 311 321
20,000ft Military 352 361 372
20,000ft Normal 335 344 356
28,000ft* Military 380 389 404
32,000ft* Normal 373 382 397

By 1939, the U.S. Air Corps Research Board decided among the needs in the liquid-cooled field were 1,342 to 1,491 kW (1,800 to 2,000 hp) flat engines for installation in bomber wings; requirements only attainable by an H type.

Lycoming had already begun studies for a 24-cylinder H-2470 engine, just two O-1230 opposed engines pancaked together. The first H-2470 is believed to have passed a development test in 1942, and the Navy sent a letter of intent ordering 100 engines, for which the principal use was to be the Curtiss F14C fighter, the first carrier fighter designed with a liquid-cooled engine since 1925. However, before the new factory went into production, the Navy decided that it would be available in quantity too late to be of use in the war, and accordingly canceled its contract.
Lycoming XH-2470-7, H-24 Engine
This XH-2470-1 engine was flight tested in the Army Vultee XP-54in 1943, but not produced for similar reasons.
Dimensions
Length 231.5 cm (91.13 in.), Width 82.7cm (32.54 in.), Height 128.2 cm (50.47 in

• ype: Reciprocating, H-type, 24 cylinders, water-cooled
• Power rating: 1,715 kW (2,300 hp) at 3,000 rpm
• Displacement: 40 L (2,468 cu in.)
• Bore and Stroke: 133 mm (5.3 in.) x 121 mm (4.8 in.)
• Weight: 1,088.6 kg (2,400 lb)

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johnbr said:

View attachment 467760 XP-54 Flight Characteristics
For its first flight on January 13, 1941, the XP-54 was fitted with Curtiss propeller.

Click to expand...

A small correction: the first flight of the XP-54 was January 15, 1943, having started ground testing in December 1942.

An interesting point for me was the pressure cabin.

Originally the XP-54 was not to have one, like the in-production pursuits. But observations of the air war in Europe suggested they needed one.

So the XP-54 was to have the pressure cockpit. Around teh same time this was being thrashed out between the Materiel Command and Vultee, Supermarine was developing a pressursied cabin for the Spitfire VI.

The cabin for the VI was rather simpler. The canopy was fixed in place by the ground crew and sealed with an inflatable rubber tube. The canopy could be jettisoned by the pilot in flight if necessary.

The Spitfire VI cabin pressurisation only gave a difference of 2psi, which meant the pressure in the cockpit was equivalent to ~20,000ft when the aircraft was flying at 30,000ft, or 25,000ft when at 35,000ft.

In contrast, the XP-54 aimed to maintain cabin pressure equivalent to 10,000ft when flying at 35,000ft, a difference of 6.6psi. The cabin glasshouse was totally fixed, with entry and egress by the contraption shown in previous postings. This was complicated and heavy.

At some point, before the middle of 1944, the Spitfire changed to a sliding hood for the pressure cabin.

There are two things regarding the second XP-54 prototype I have to bring up:

1. Photos of the second XP-54 on its first flight show the rudder with the serial number 41-1211, but that serial was allotted to a Vultee BT-13 Valiant, and AAF records clearly indicate that the second XP-54 was given the serial 42-108994.

2. Some older WW2 American military aviation publications claim that the second XP-54 flew once, but the flight log by the test pilot for the second XP-54 shows that XP-54 serial number 42-108994 made ten flights (see Gerald Balzer's 2008 publication American Secret Pusher Fighters of World War II: XP-54, XP-55, and XP-56).

Nice work!