Beaufighter T. F. X.

2.1 General. The following are the main features of the aircraft.

2.2 Loading.
Tests were made at a take-off weight of 24,000 lb. with the centre of gravity 52.5 inches aft of the datum point. The loading included one 18 inch Mark XII torpedo carried centally under the fuselage.

2.3 Engine numbers and limitations.

The following limitations applied to the Hercules XVII at the time of the tests.

3.1 Take-off:
Take-off run and distance to clear a 50 ft. obstacle were measured using a flap setting of 15 deg.

3.2 Climb.
Ceiling climbs were made with cooling gills fully open using the best climbing speeds as determined from partial climbs, and changing supercharger gear at the optimum height deduced form separate preliminary climbs using M.S. and F.S. supercharger in turn.

3.3 Level speeds.
The following speed trials were made with cooling gills closed.

4.1. Take-off results were corrected to zero wind and standard atmospheric conditions by the methods of R & M 1172.

Climb and level speed results were corrected to standard atmospheric conditions by the method of A.& A.E.E. Report N. Res.170. Level speeds were corrected to 95% of the take-off weight (22,800 lb.).

The position error for Beaufighter X.7540, has been corrected for weight and used in calculating speeds in this report.

4.2. Take-off. Results of measurements of take-off run and distance to clear 50 ft. obstacle using a flap setting of 15 deg. are given below.

The handling qualities during take-off and initial climb were as for Beaufighter VI E.L.223, except for the swing to starboard which is more pronounced on this aircraft. The swing can still however be held by differential operation of the throttles during the earlier part of the run and by use of rudder in the latter part.

4.3. Partial climb tests give a best climbing speed of 130 knots to a full throttle height F.S. gear, reducing by 1 knot per 1000 ft. above this height.

Results of climb to ceiling are given in Table I and Fig.1. Rates of climb of 1460 ft/min and 1260 ft/min were obtained up to full throttle heights using M.S. and F.S. gear respectively. The optimum change gear height is 4,500 ft. The estimated ceiling is 20,400 feet.

4.4. Level speeds. Speed results are given in Table II and Fig.2.
A summary of the maximum speeds obtained under maximum power for level flight and maximum economical cruising power are given below.

With the throttle lever at the maximum power position and at maximum R.P.M., a boost pressure of 10.5 lb/sq.in. was obtained. An instrument error of +0.5 lb/sq.in. gave a true boost pressure of 11.0 lb/sq.in. which exceeded the limitations of 10.0 lb/sq.in. The following maximum speeds are therefore taken from the speed curve at the full throttle heights corresponding to a boost pressure of 10.0 lb/sq.in.

Speeds that could be obtained below full throttle height at a controlled boost pressure of 10.0 lb/sq.in. have been estimated from the results and are given in Table III and Fig.2.

5.1. The results of the previous tests are compared with those obtained on Beaufighter VI EL.223 powered by Hercules VI engines.

5.2. Handling. No difference in handling properties has been observed apart from the increase in swing at take-off mentioned in para.4.2.

5.3. Performance.