Airc?eit of the P.F.A.

Rarest of all rare birds in the Association, and one of the most unusual types on the British Civil Register, the Hirtenberg H.S.9A is not only a sole survivor, but a 'one off' aeroplane with a most interesting history.

The Hirtenberg aircraft company was formed to take over the works of the old Hopfner Company, which had been the first company to start production of aeroplanes in Austria after the first World War and which had to go into liquidation in 1935. Herr Th. Hopfner remained as director of the aircraft department of Hirtenberg, whose first production was the licence-built Focke-Wulf Steiglitz.

Hopfner had designed and built a series of parasol wing monoplanes in previous years so that it was not surprising that he should produce, among the designs of the new company, a very good-looking parasol monoplane, powered by a Siemens Shotti S.H.4A radial engine. 'This was the Hirtenberg H.S.9.

The structure of this aeroplane was to the classic formula of a wooden, two-spar, fabric,covered wing, with steel tube fuselage also ,covered by fabric. The tail unit was mixed wood and steel, fabric-covered. The undercarriage consisted of long-travel oleo legs, with a very wide track. Wheel brakes were fitted. Complete dual controls were carried in both the tandem cockpits. The wings folded about the rear spars and the joint of the vee interplane struts with the fuselage.

A number of these aircraft were built with the l25ll5O h.p. Siemens, and in 1937 one was built for Mr. J. H. Davis of Vienna. This was the one and only H.S.9A, constructor's No. 001, and differed from the normal type in being fitted with a de Havilland Gipsy Major (No. g996). It had been intended that this aeroplane should be used to try for a contract from Air Ministry for a Tiger Moth replacement aircraft and con- t6 sequently contained a large number of A.G.S. parts-which must have simplified maintenance after its arrival here. It left the factory on 23rd July, 1937, spent the period from 24th July to 13th August being tested and commenced its career with its owner on the following day.

On the 23rd August, at Vienna, the tail-skid caught in an obstruction and was torn out, damaging the tail. The registration letters were OE-DJH (the nearest Mr. Davis could get to having his own initials on it) and these, reflecting the political situation of the time, became D-EDJH in May, 1938.

In July, 1939, the Hirtenberg arrived at Croydon. A certain amount of confusion-not to say alarm-was caused by this strange, swastika-beflagged arrivaT, but its position was very soon legalised and the registration G-AGAK allotted to it. When war broke out it was at Airwork, from where it departed for Filton, remaining there, as far as we know, throughout the war. Returning to Airwork for a C. of A. when it was restored to the Register after the war (ll146), the tail-skid was replaced by a tailwheel in the lollowing year. Back at Bristol in 1947 it was sold to D. D. Budworth (18-9-50), and passed into the hands of A. J. Stocks of Croydon on 27th August, 1954. He sold it to J. E. Coxon (9th November, 1955), and on l6th April,1956, it was purchased by its present owner, C. H. Cosmelli. It lives at the present time in the blister hangar at Denham. One fairly recent modification has been the installation of a wing-root fuel tank to supplement the normal tankage.

The writer has only flown once in the H.S.9A, but on that occasion was most irnpressed by the steadiness and freedom from vibration of the aeroplane. It is a very sturdy and quite heavy aircraft, with an empty weight of 1,291 1b., and a loaded weight of 2,090 lb.

Popular Flying, September, 1957