Piasecki H-25A: The Wrong Helicopter at the Right Place

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Introduction and History
The Piasecki HUP Retriever is a tandem-rotor utility helicopter that would eventually lead to their more popular H-21 utility helicopter. Initial development of the aircraft started around 1946, and was a direct competitor to Sikorsky’s XHJS-1, which was an upscaled H-5. The Piasecki prototype, designated XHJP-1, had its first flight sometime in 1947 and won the contract. The prototype model was accepted for service, but it would still take a few years for a production model to be introduced. By 1950, however, the HUP-1 would enter production for the US Navy. Two subsequent developments would arise from the original model: An upgraded model for the Navy, and another for the Army. The Navy’s new model would be designated HUP-2, while the Army’s model would be the H-25A Army Mule. Both models featured removal of the tail surfaces and uprated engines, however the Navy model also featured an autopilot. The H-25A first entered Army inventory starting in 1953, but, despite the promising performance from the initial tests, was deemed unsuitable for front-line Army service and withdrawn from Army inventory starting in 1955. By 1958, the Army’s inventory of H-25As was completely withdrawn and transferred over to the Navy, where they received the designation HUP-3. The HUP would only remain in service for roughly 6 years after this, being retired by the Navy in 1964.

Specifications
For a tandem-rotor helicopter, the H-25 was relatively compact, and fairly maneuverable: It was the first helicopter to perform a loop while demonstrating its g-loading capabilities.

Specifications (H-25A)

Crew: 2 (Pilot and Co-Pilot) with room for 2 passengers
Length (Rotors Turning): 56’ 11"
Length (Rotors In Phase and Static): 48’ 7"
Length (Rotors Dephased): 40’ 2.7"
Length (Blades Folded): 31’ 11"
Width (Blades Folded): 8’ 6"
Width (Rotors Turning): 35’
Tread: 8’ (Main Gear)
Height Overall (Blades Folded): 13’ 2.3"
Fuel capacity: 150 gallons

Weights:
Basic Weight: 4150 lbs.
Normal Gross Weight: 4600 to 4900 lbs.
Maximum Load: 5400 lbs.
Maximum Overload: 5750 lbs.

Do Not Exceed Speed: 100 to 105 knots
Ceiling: 12,000 to 15,750 ft.
Range: 402 to 421 nmi
Engine: Continental R-975-46A (450 to 475 hp standard, 500 to 525 hp emergency power)
Engine RPM: 800-1200 (idle), 2100 to 2350 (2400 emergency maxmimum)
Main Rotor RPM: 230 minimum, 245-273 normal (360 maximum)
Climb Rate (Normal Power):
Maximum climb rate (Minimum to 4900 lbs.): 500 ft./min. @ SL, 92 ft./min. @ 14,000 ft.
Maximum climb rate (4901 to 5400 lbs.): 500 ft./min. @ SL, 345 ft./min. @ 10,000 ft.
Climb Rate (Emergency Power):
Maximum climb rate (Minimum to 4900 lbs.): 1379 ft./min. @ 4,000 ft., 190 ft./min. @ 14,000 ft.
Maximum climb rate (4901 to 5400 lbs.): 1057 ft./min. @ 4,000 ft., 412 ft./min. @ 10,000 ft.
Maximum climb rate (5401 to 5750 lbs.): 872 ft./min. @ 4,000 ft., 193 ft./min. @ 10,000 ft.

Armament
The H-25A was never intended to have an armament, as was with most other utility helicopters. However, a single example found its way into the hands of a Colonel Jay D. Vanderpool in Fort Rucker. Vanderpool led a group that was tasked with turning the helicopter into a weapons platform, to take advantage of the “3rd dimension” of ground combat, being the air. While his H-25A would be subject to the same retirement as the rest of the Army’s inventory, this one certainly had a much more eventful service life. The armament given to the helicopter was nothing short of unusual. While it came armed with the two AN/M2 .30 (or possibly .50, depending on what you read), it also had two packs of 66 1.5" NAKA spin-stabilized rockets, totaling 132 rockets. These rockets were given to Vanderpool by the Air Force, which in turn was originally manufactured by Rocketdyne for Northrop’s N-102 fighter which never made it past a mockup. During test fires, it gave the group a good idea about the future of 40mm ordnance in development. Unfortunately, Vanderpool’s fools would expend the entire stock of rockets within a year. On top of this, very little information (if any at all) survives to this day about the rockets.

Armament Images (3)



Other Images (10)










Conclusion
The H-25A, an unusual yet handy helicopter, found its way quickly in and out of the Army’s inventory. Fortunately, a single one found its way in the hall of fame for attack helicopter development. In-game the H-25A could see itself as the start of a tandem-rotor line for the American helicopter tree, as there are many notable examples of such aircraft that have yet to be added. Favorable flight performance with a light armament would make lower BR matchmaking ideal for this aircraft.

Sources

NAVWEPS 01-250HCA-1 - HUP-1, HUP-2, & H-25A Flight Handbook - 19600701
H-25A CS - 19560416
US Army Aviation Digest - June 1971
US Army Aviation Digest - August 1971
The Evolution of the Advanced Attack Helicopter, Final Report - Major Dante A. Camia - 6 June 1975
Piasecki - The PH-42 (H-21) Transport Helicopter - April 1954
Cobra! The Attack Helicopter - Mike Verier (2013)
American Military Helicopters and Vertical/Short Landing and Takeoff Aircraft Since 1941 - E. R. Johnson (2021)
U.S. Army Aircraft Since 1947 - Stephen Harding (1990)
Information on the NAKA rocket

2 Likes

That’s really cool! +1

🇺🇸: Mi4av at home

1 Like

I’m aware (thanks to you) of the armed H-25A and H-21C, and already knew about the ACH-47A. Are there more beyond those three?

The only question would be: are these rockets good against vehicles? If not and they were used only against infantry, then I would not recommend this bird and prefer instead the H-21. If they had an AT warhead like a HEAT one, then I would be glad to see this bird around 7.3 - 7.7!!!