P.Bowers Curtiss Aircraft 1907-1947 (Putnam)
Model HA (Model 16)
The HA series of 1918 had no connection with the H-series flying-boats that originated in 1914. The HA was not even a Curtiss design; it was designed by Captain B. L. Smith of the US Marine Corps, and the Curtiss Engineering Corporation at Garden City was given a contract to build a prototype in December 1917. Two others were ordered later. Powered with the new Liberty engine, the two-seat seaplane was named Dunkirk Fighter because it was intended to establish Allied air superiority over the Belgian coastal area around Dunkirk, then held by the Germans.
Construction of the first HA, Navy serial A2278, was conventional wood and fabric, but there were several notable departures from standard configuration. The Liberty engine was entirely buried in the nose of a fat fuselage that was rounded out by formers and stringers outside of the basic rectangular structure. The nose was tipped with a large-diameter spinner. The single main float was mounted on two centreline struts and was stabilized by bracing wires running out to the inner bay of wing struts. The wing arrangement was unusual in that the upper wing, which had its roots resting on the top of the fuselage, was rigged with dihedral while the lower wing was rigged with anhedral. The pilot in the forward cockpit sat in a large cutout behind the rear spar of the upper wing while the gunner had a conventional cockpit and two-gun Scarff ring.
The first HA was ready for flight on 21 March, 1918. It was so tail heavy as to be almost unmanageable in the air and Curtiss's best pilot Roland Rohlfs managed to bring it down in a series of swoops to a crash landing that destroyed the aeroplane.
HA-1 - Curtiss was then given a contract for two additional HAs, Navy serials A4110 and 4111, and some parts of the first one were incorporated into a considerably revised second prototype designated HA-l. Main changes were redesigned vertical tail surfaces with fixed vertical fin area above and below the fuselage, a more rearward location for the wings, and deletion of the spinner in favour of a nose radiator installation. Price less GFE was $42,900.
The performance of the A4110 was greatly improved, but it caught fire in the air. Pilot Rohlfs got it down safely but A4110 was a total loss.
HA-2 - The third HA was fitted with entirely new wings and became the HA-2. The new wings were of two-bay type with no dihedral on either panel. A centre section for the upper wing was held above the fuselage on conventional struts. The Armistice ended further military development of the HA design but the speed of the surviving example encouraged the Navy to enter it in the postwar Curtiss Marine Trophy Race for Service seaplanes. Cost was $42,900 less GFE.
HA Mail - In 1919, Curtiss developed a landplane version of the HA-1 into a single-seat mailplane for the Post Office Department, which was then operating the US Air Mail service. The pilot was moved to the former rear cockpit location and the front cockpit was converted to a mail and cargo compartment. After trying one with single-bay wings, Curtiss sold three two-bay HA mailplanes to the Post Office for $12,000 each less engines.
Fighter seaplane. Pilot and gunner.
360 hp Liberty.
Span 36 ft (10,97 m); length 30 ft 9 in (9,37 m); height 10ft 7 in (3,22 m); wing area 387 sq ft (35,95 sq m).
Empty weight 2,449 lb (1,110 kg); gross weight 3,602 lb (1,634 kg).
Maximum speed 126 mph (202,77 km/h); climb 9,000 ft (2,743 m) 10 min; service ceiling 19,000 ft (5,791 m); endurance (full throttle) 2 1/2 hr.
Fighter seaplane. Pilot and gunner.
360 hp Liberty.
Span 42 ft (12,8 m); length 30 ft 9 in (9,37 m); height 11 ft 5 in (3,47 m); wing area 490 sq ft (45,52 sq m).
Empty weight 2,946 lb (1,336 kg); gross weight 3,907 lb (1,772 kg).
Maximum speed 118 mph (189,89 km/h); climb 7,900 ft (2,408 m) 10 min; endurance (full throttle) 2 1/2 hr.
Armament (both types) - two fixed and two flexible machine-guns.
G.Swanborough, P.Bowers United States Navy Aircraft Since 1911 (Putnam)
CURTISS HA DUNKIRK FIGHTER
The HA was designed to serve as a two-seat escort and air superiority fighter for the Dunkirk-Calais area. Powered with the 400 hp Liberty, the prototype HA (A2278) flew on March 21, 1918, but soon crashed. Two modified versions were then ordered as HA-1 (A4110) which included salvageable parts of A2278, and the longer-winged HA-2 (A4111). Following the war's end, both were used for miscellaneous testing, and a landplane variant of HA-2 was developed for the Post Office department as a mailplane. Span, 36 ft (HA-2 span, 42 ft); length, 30 ft 9 in; gross weight, 4,012 lb; max speed, 132mph.
W.Green, G.Swanborough The Complete Book of Fighters
CURTISS HA USA
Designed by Capt B L Smith of the US Marine Corps as a two-seat patrol fighter floatplane for use in the Dunkirk-Calais area, the HA - known unofficially as the "Dunkirk Fighter” - was intended to combat the Brandenburg float fighters and was built at the experimental plant of the Curtiss Engineering Corporation. Of conventional wooden construction with fabric skinning, the HA was powered by a 425 hp Liberty 12 engine and featured an unusually rotund fuselage. Proposed armament comprised two synchronized 0.3-in (7,62-mm) Marlin machine guns and two Lewis guns of the same calibre on a Scarff mounting in the rear cockpit. The HA was flown for the first time on 21 March 1918, but was found to be unstable longitudinally and seriously tail heavy. The initial test terminated in a crash. Curtiss was then awarded a contract for two further prototypes, the first of which, the HA-1, utilized salvaged components from the original HA and featured revised vertical tail surfaces, an annular-type radiator and relocated wings. The HA-1 demonstrated appreciably improved handling qualities, but was written off after a fire in the air. The third HA prototype, the HA-2, differed appreciably from the HA-1 (see following entry). The following data apply to the HA-1 float fighter.
Max speed, 126 mph (203 km/h).
Time to 9,000 ft (2 743 m), 10 min.
Empty weight, 2,449 lb (1 111 kg).
Loaded weight, 3,602 lb (1634 kg).
Span, 36 ft 0 in (10,97 m).
Length, 30 ft 9 in (9,37 m).
Height, 10 ft 7 in (3,23 m).
Wing area, 387 sq ft (35,95 m2).
CURTISS HA-2 USA
The third HA float fighter prototype embodied considerable redesign as the HA-2. Powered by a 12-cylinder Liberty 12 water-cooled engine, like the preceding prototypes, the HA-2 had longer-span wings of marginally increased chord and gap, the upper wing being raised clear of the fuselage, the decking of which was lowered. The radiator was redesigned, but cooling problems were encountered and although the HA-2 proved more docile than the lighter HA-1, it possessed insufficient promise to warrant further development.
Max speed, 118 mph (190 km/h).
Time to 7,900 ft (2408 m), 10 min.
Empty weight, 2,946 lb (1 336 kg).
Loaded weight, 3,907 lb (1772 kg).
Span, 42 ft 0 in (12,80m).
Length, 30 ft 9 in (9,37m).
Height, 11 ft 5in (3,48 m).
Wing area, 490 sq ft (45,52 m2).