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Handley Page Hendon (HP.25)


Biplane Torpedo Bomber Prototype Aircraft


Just six prototypes made up the twin-seat Handley Page Hendon - developed from the earlier Hanley single-seat biplane - torpedo bomber program.
Authored By: Staff Writer | Edited: 1/31/2019
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Specifications


Year: 1924
Status: Cancelled
Manufacturer(s): Handley Page - UK
Production: 6
Capabilities: Ground Attack; Navy/Maritime; X-Plane;
Crew: 2
Length: 34.48 ft (10.51 m)
Width: 45.93 ft (14 m)
Height: 13.68 ft (4.17 m)
Weight (Empty): 4,409 lb (2,000 kg)
Weight (MTOW): 6,967 lb (3,160 kg)
Power: 1 x Napier Lion IIB 12-cylinder water-cooled engine developing 450 horsepower and driving a two-bladed wooden propeller at the nose.
Speed: 110 mph (177 kph; 96 kts)
Ceiling: 9,514 feet (2,900 m; 1.8 miles)
Operators: United Kingdom (cancelled)
Part of the work completed by Handley Page during the early 1920s, in an attempt to satisfy a standing Fleet Air Arm (FAA) requirement of 1920 for a modern carrier-based torpedo bomber, was the "Hendon". This twin-seat torpedo-carrying biplane was built alongside the single-seat "Hanley" of similar form and function, both of which would ultimately be passed over for the Blackburn "Dart" (detailed elsewhere on this site). The Hendon was completed in six prototype examples and flown in 1924 but these ended their days as test aircraft for various wing surface control fittings and carrier operation evaluations.

The aircraft exhibited many qualities of the time: an over-under biplane wing configuration, open-air cockpit, and fixed tail-dragger undercarriage. The wings were multi-bayed with parallel struts and left unstaggered. The engine was positioned at the nose in the usual way and drove a two-bladed propeller. The cockpit was seated near midships with generally poor views for the pilot (the machine gunner was directly behind). The fuselage sported slab sides and tapered towards the tail to which a single-finned rudder was affixed. The undercarriage involved a twin-wheeled component under the forward mass of the aircraft with a simple tail skid under the rear.

FAA authorities saw enough value in the Hendon to order is as a test aeroplane through a contract given on November 27th, 1923 - this to cover a total of six aircraft. Hanley had designed this two-seater from the final Hanley form, the Hanley III. The Hanley III was the third of three iterations born from the Hanley project and ultimately rectified control issues in the design while incorporating full-span leading edge slots for low-altitude, low-speed handling crucial to carrier operations. Specification 25/23 was drawn up to cover the new aircraft, then known as the "Type Ta" (retrospectively redesignated to "HP.25").

A first-flight of the prototype Hendon was recorded on July 7th, 1924 and the entire lot was constructed before the end of the year for further testing. Some revisions were made to the design when the full war load was added, resulting in slight sweepback of the wing mainplanes to offset heavier loads placed on the tail section.

Three distinct variants of the Hendon were completed: Hendon I, Hendon II, and Hendon III. The Hendon II mark were three revised Hendon I aircraft with improved slot gear and the Hendon III was a one-off conversion of a Hendon II model with slotted flaps.

The basic approach to the design borrowed much from the Hanley save for a slightly lengthened fuselage to accommodate the second crewmember - as such a tandem-seat arrangement was used. Dimensions included a running length of 34.5 feet, a wingspan of 46 feet, and a height of 13.7 feet. Empty weight reached 4,350lb and the Maximum Take-Off Weight (MTOW) reached 7,000lb. Power was from a Napier Lion IIB 12-cylinder, water-cooled unit of 450 horsepower - the same engine featured in the earlier Hanley and the competing Dart aircraft - and this was used to power a two-bladed wooden propeller at the nose. Performance specs included a maximum speed of 110 miles-per-hour with a service ceiling up to 9,500 feet.

Standard armament was a single 0.303 Vickers Machine Gun over the nose in a fixed, forward-firing mounting synchronized to fire through the spinning propeller blades as well as a single 0.303 Lewis Machine Gun on a trainable mounting at the rear cockpit. The bombload was either a single 18" (457mm) aerial torpedo or 2 x 230lb drop bombs.






Armament



STANDARD:
1 x 0.303 Vickers Machine Gun in fixed, forward-firing mounting over the nose and synchronized to fire through the spinning propeller blades.
1 x 0.303 Lewis Machine Gun on trainable mounting in rear cockpit.

OPTIONAL:
1 x 18" (457mm) aerial torpedo OR 2 x 230lb conventional drop bombs.

Graphical image of an aircraft aerial torpedo
Graphical image of an aircraft conventional drop bomb munition

Variants / Models



• "Hendon" - Base Series Name.
• Hendon I - Initial prototype design based in the single-seat Hanley III torpedo carrier prototype; six examples completed as test aircraft under FAA contract.
• Hendon II - Three Hendon III aircraft with modified leading edge wings.
• Hendon III - One-off modification of Hendon II aircraft; slotted flaps added.
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