El.290

SUMMARY
...........Brief performance trials have been made at a weight of 24,000 lb. on Beaufighter T.F.X. E.L. 290 fitted with Hercules XVII engines and carrying a Mark XII torpedo. The following results were obtained.

Take-off run under standard atmospheric conditions and zero wind = 440 yds.
Distance to clear 50 ft. screen = 760 yds.

Maximum rates of climbs:-

M.S. gear up to full throttle height (2600 ft) 1460 ft. per min.
F.S. gear up to full throttle height (9600 ft) 1260 ft. per min.
Service ceiling 20,400 ft.
Estimated absolute ceiling = 21,300 ft.

Maximum true airspeeds:-

All-out power M.S. gear 297 mph (258 knots) at 1300 ft.
All-out power F.S. gear 308 mph (268 knots) at 9200 ft.

Maximum economical cruising power M.S. gear 267 mph (232 knots) at 9700 ft.
Maximum economical cruising power F.S. gear 277 mph (241 knots) at 16000 ft.

...........Comparing with previous tests of a Beaufighter VI with torpedo the all out level speed at 1500 feet has been increased by 9 m.p.h. by the use of the Hercules XVII engine.

1. Introduction.

...........Performance and engine cooling trials were required on a Beaufighter aircraft fitted with Hercules XVII engines and carrying an 18 inch torpedo. This report deals with take-off, climb, and level speed performance.

2. Condition of aircraft relevant to tests.

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

................An 18 inch torpedo was carried under and clear of the fuselage.
................Dive brakes, fitted on the upper and lower trailing edges of eaach wing inboard of the ailerons wer retracted during flight. These brakes were of production type and slightly proud of the wing when retracted.
................A venturi for operating the dive brakes were fitted uder each wing.
................The nose of the fuselage was modified for a torpedo camera.
................The four gun ports in the starboard and the two in the port leading edges were sealed.
................A standard aerial mast and aerial were fitted.
................Aerials extended from the aerial mast to both tailplane tips.
................I.F.F. aerials extended form each tailplane tip to the fuselage.
................A D.F. loop was contained in the perspex cupola on top of the fuselage.
................A drift recorder projected on the port side of the fuselage opposite the navigators seat.
................The pressure head was of type Mk.VIIID, and was situated under the port wing. The pressure head was identical in type and position with that of Beaufighter X.7540.

...........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.

Makers No.Air Ministry No.
PortH 110006A.M. 451005
StarboardH 110004A.M. 451003

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

ConditionR.P.M.Boost lb/sq.in.
Take-off2900+10.0*
Maximum power for climbing2400+6.0
Maximum power for level flight2900+10.0
Maximum continuous cruising power2400+6.0
Maximum economical cruising power2400+2.0
* or full throttle
3. Scope of 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.

(i)Maximum power for level flight
M.S. supercharger gear 1000 ft. - 10,000 ft.
F.S. supercharger gear 2000 ft. - 16,000 ft.

(ii)Maximum economical cruising power
M.S. supercharger gear 1000 ft. - 16,000 ft.
F.S. supercharger gear 7000 ft. - 16,000 ft.
4. Results of tests.

...........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.

.Under conditions
of test
mean wind speed 1 mph
Temp +7 deg. C.
Pressure 29.99 ins. Hg.
Corrected to
standard
atmospheric
conditions
Take-off run yards400440
A.S.I. at take-off88 mph.
True airspeed at take-off (from camera)85 mph.
Distance from rest to clear 50 ft. obstacle-yds.715760
A.S.I. during initial climb107 mph.
True airspeed at a height of 50 ft. (from camera)106 mph.
Mean take-off R.P.M.2900.
Mean take-of boost lb/sq.in.+9.5.
................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.

Height
feet
R.P.M.Boost
lb/sq.in.
S/C
gear
T.A.S.
m.p.h. (knots)
13002880*+10.0M.S.297
(258)
92002865*+10.0F.S.308
(268)
97002400+2.0M.S.267
(232)
160002400+2.0F.S.277
(241)
................* Maximum R.P.M. not obtainable due to maladjustment of constant speed unit.

................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. Comparison of results with those of Hercules VI installation.

...........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.

...................5.31 Take-off. (In zero wind and under standard atmospheric conditions) Take-off run and distance to clear 50 ft. screen of Beaufighter E.K.223 at a weight of 24300 lb, were 440 yards and 760 yards respectively which agree identically with the correspsonding distances given in this report. Replacing the Hercules VI by the Hercules XVII engine, therefore, apparently produces no improvment in take-off performance.

...................5.32 Level speeds. The Hercules VI and Hercules XVII installations give the same maximum true airspeed at 3500 feet. Below this height the Beaufighter T.F.X. is faster than the Mark VI; at 1300 feet the difference in true airspeed is 9 m.p.h.

Table I.
Climb Performance Take-off weight 24,000 lb.
2400 R.P.M. Cold air intake. Gills fully open.

Height
feet
Time to
height
mins.
Rate of
climb
ft/min
T.A.S.
m.p.h.
(knots)
A.S.I.
m.p.h.
(knots)
P.E.C.Comp.Mean Man.
pressure
lb/sq.in.
S/C
gear
001460154
(130)
150
(130)
4.00.06.0M.S.
2600*1.81460160
(139)
150
(130)
4.0-0.16.0"
4500**3.21260164
(142)
150
(130)
4.0-.24.25M.S./F.S
60004.41260168
(146)
150
(130)
4.0-.26.0F.S.
80006.01260173
(150)
150
(130)
4.0-.36.0"
9600*7.21260177
(154)
150
(130)
4.0-.36.0"
120009.41000180
(156)
146
(127)
4.2-.43.8"
1400011.6780183
(159)
144
(125)
4.2-.52.3"
1600014.7560186
(161)
142
(123)
4.3-.71.0"
1800019.1350189
(164)
139
(121)
4.6-.8-0.2"
2000027.9140193
(168)
137
(119)
4.7-.9-1.3"
2040031.2100193
(168)
136
(118)
4.8-1.0-1.6"

* Full throttle heightsEstimated absolute = 21,300 feet.
** Change gear height

Table II.
Level speed performance. All-up weight 22800 lb.(i.e. 95% take-off weight)
Cold air intake. Gills closed.

Height
feet
T.A.S.
m.p.h.
(knots)
A.S.I.
m.p.h.
(knots)
P.E.C. Comp.Mean Boost
pressure
lb/sq.in.
Mean
R.P.M.
Super-
charger
gear
200*297
(258)
303
(263)
-6.70.011.02880M.S.
1300**297
(258)
299
(260)
-6.4-0.210.0""
2000296
(257)
294
(255)
-5.9-0.49.4""
4000295
(256)
284
(247)
-5.4-0.87.7""
6000293
(254)
274
(238)
-4.8-1.36.1""
8000290
(252)
262
(222)
-4.0-1.34.6""
10000287
(249)
251
(218)
-3.1-1.33.3""
2000282
(245)
279
(242)
-5.1-0.311.0 2865F.S.
4000290
(252)
279
(242)
-5.1-0.711.0""
6000299
(260)
279
(242)
-5.1-1.111.0""
8300*308
(267)
278
(241)
-5.0-1.511.0""
9200**308
(267)
271
(235)
-4.6-1.610.0""
10000307
(267)
270
(234)
-4.5-1.89.2""
12000306
(266)
261
(226)
-3.9-2.07.3""
14000305
(265)
251
(218)
-3.2-2.35.7""
16000302
(262)
241
(209)
-2.5-2.34.1""

* Test full throttle heights
** Full throttle height with boost restricted to 10.0 lb/sq.in.
(Cruising speeds at 2400 r.p.m. and +2.0 boost omitted)

Table III.
Level speed performance 22800 lb.
Estimated performance at 10.0 lb/sq.in. boost pressure.
Below full throttle height F.S. gear

Height
feet
T.A.S.
m.p.h.
(knots)
A.S.I.
m.p.h.
(knots)
P.E.C. Comp.Mean Boost
pressure
lb/sq.in.
Mean
R.P.M.
Super-
charger
gear
9200*308
(268)
271
(235)
-4.6-1.6+10.02865F.S.
8000303
(263)
275
(239)
-4.8-1.4"""
6000294
(255)
275
(239)
-4.8-1.1"""
4000286
(248)
275
(239)
-4.8-0.7"""
2000278
(241)
275
(239)
-4.8-0.3"""

* Full throttle height
Fig. 1 Climb Performance
Fig. 2 Level Speed Performance

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