1.0 Comments of Trials.

               The aeroplane was delivered with the early production pattern of windscreen which is practically flush fitting on the outside, and armour plating over the fuel tank in the fuselage. The latter modification was not incorporated in L.1547 when that Hurricane was tested in turn with the wooden fixed pitch and metal two-pitch airscrews. (See Part of Report No.M/689/a dated 9th October 1939 and 21st January 1939 respectively). It is unlikely that the performance of L.2026 has been affecrted by the armour plating.

               All the tests at 6316 lb. had been completed with the exception of a full throttle climb when the engine was damaged and had to be replaced. This climb and the trials at 6750 lb. were therefore carried out with a new engine.

2.0 Take-off (pages 10,10(a). Fig.17)..

               The take-off run in zero wind and under standard atmospheric conditions is better than that of the 2-pitch airscrew Hurricane. The accompanying table gives the take-off for 3 types of airscrew and for the overload Rotol case. The use of 20 ° flap for 6,750 lb. on the Rotol Hurricane shortened the run and distance to screen by 15 yards.

               It was found that at normal load the best climbing speed as determined from partial climbs was not suitable owing to the instability and uncomfortably steep attitude obtaining at this speed when at high altitudes. The climbing speed was increased by 20 mph to 170 mph A.S.I., a more suitable speed which improved the handling qualities of the aeroplane on the climb. The same procedure had to be adopted in the overload case.

               The following table gives comparative times in minutes to reach various heights for the best climbing speed and recommended climbing speed at normal load. Also included are the times to height for the overload case and for a Hurricane with a fixed pitch airscrew. No figures are available for a climb with a two-pitch airscrew.

               In addition to the routine speed tests on this aeroplane as delivered, subsidiary tests were made to determine the effect of engine r.p.m. on the top speed. Further tests were made at overload.

4.1 Controlling R.P.M.

               Speed tests were made at 13,000 and 9,000 ft with the boost pressure maintained constant at 6¼ lb. per sq.in whilst the R.P.M. was varied over a range from 2,600 to 3,000. These tests were made to determine whether the maximum speed was attained with the airscrew controlling at 2,800 r.p.m. as found to be on Rotol Spitfire N.3171 (See first part of report A.&.A.E.E.692,d March 1940). The maximum speed of the Hurricane was attained with the airscrew controlling at 3,000 r.p.m.

4.2 Overload.

               Increasing the weight from 6,316 lb. to 6,750 lb. had the effect of reducing the maximum level speed by 6 m.p.h. from 316 to 310 m.p.h. though it should be noted that the engine was changed between the two sets of results.

5.0 Interconnection between throttle and airscrew control. (Drg.No.1811)

               A device has been incorporated to prevent the engine being opened up with the airscrew controlling at low engine speeds. It consists of a length of Bowden cable attached at one end to the lower arm of the throttle lever and at the other end to the constant speed control lever. When the engine control is moved forward the C.S. control, if inadvertently left in the low r.p.m. position, is pulled forward into a high r.p.m. setting. These are the only circumstances under which the interconnection system functions, normal independent operation of the two controls being possible otherwise.

               This device has proved satisfactory in all conditions of flight and should eliminate risk of damage to an engine due to the above cause.