Meticulous Testing on a BSAA Tudor lV
Report on Carribean Test – Tudor IV
Summary: The results obtained on these Tropical Trials show that:
(A) the performance is satisfactory for operations in the tropics on our present routes, and
(B) the radiator cooling is satisfactory in tropical operations.
(Configuration: the Aircraft was fitted with the latest short chord Wing Root Fillets and the Propellers had the shortened Overshoes. The undercarriage, however, was not modified to the shortened type.)
Aileron Controls were light & pleasant at all speeds. Elevator & rudder are, however, a little too heavy to be pleasant. The Aircraft has no marked vices but it will swing at take-off if permitted to do so in some circumstances. This swing in the normal case into Wind is less than a Lancastrian but owing to the very large fin surface the weather-cocking tendency both at Take-off and on Landing is slightly more marked than a Lancastrian.
Landings can be carried out normally in almost any Attitude but it is desirable to touch with almost more vertical component if some bouncing is to be avoided (with the present, unmodified undercarriage). At 74,000 lbs. All Up Weight. the Approach should be carried out at a speed not lower than 115 Knots, and at such a weight the Aircraft should not be held off too high as the drop at this weight comes quite suddenly as opposed to the gentle sink which occurs at the lighter Loads. Two Night Take-offs and 2 -Night Landings were carried out and no adverse features were discovered. A failure of an outboard Engine at Take-off can be held quite easily on Rudder though on these Tests this was not attempted at very low Speeds (nothing under 110 Knots). Up to 5° of Bank materially assists Rudder control in these conditions and is particularly recommended in the case of a 2 Engine failure. The Aircraft appeared to stall evenly, and the Nose dropped away at about the same time as the Tail Buffet started. The Stall and the Buffet appeared to be normal.
Cruising Porcedure & Resultant Air Miles Per Gallon:
In order to obtain a high AMPG it is necessary in this Aircraft with its large span to operate at a low Indicated Air Speed of about 155 Knots ASI at 80,000 lbs. Decreasing to about 145 Knots at the lighter Loads. To achieve the best AMPG at these speeds, the height should be chosen so as to obtain at full throttle the highest permissible cruising Brake Mean Effective Pressure. This is at about 10,000ft at the full weight at 155 Knots in M gear. In the absence of experience, a comparison of the improvement of the Merlin 621 in relation to the Merlin 24, combined with the relevant Maker’s recommendations, must be used to decide what Cruising BMEP to be used. On this basis in initial operations it is recommended that we use 175 lbs. Per sq. Inch BMEP (equivalent sea level).
The AMPG obtained in low blower on these Trials were all better than those obtained at Boscombe Down for the Tudor I in its final form which are about 2% to 4% worse than the latest A V Roe figures for this particular Aircraft (See A V Roe Report No. FTS/688 IV/I dated 1st June 1947). A Test carried out on Flight No.2 comparing the AMPG with Radiators “auto-closed” as opposed to “inch-closed” showed the latter approximately 0.75% better. In order to obtain a high True Air Speed without adversely affecting AMPG it is, of course, necessary to fly at high-level which entails the use of Pressurisation. As on this series of Flights the pressurisation was not fully Serviceable, it was not possible to obtain a full set of figures. It is clear, however, that high-level Cruising is essential for satisfactory Operation of this Aircraft.
As a tentative measure the following is the proposed BSAA Cruising Procedure:-
“Fly at 155 knots ASI above 70,000-lbs, using the required power obtained with the following combination of boost and RPM:-
It is recommended also as a tentative measure that we should adopt a Cruising climb at 140 Knots ASI using 2,650 rpm and boost between +7 and +9. The rate of Climb using 2,650 rpm and +9 boost (taking-off at 80,000 lbs.) was tested on 2 occasions (Flight No.5 & Flight No.8). The average rate of climb to 10,000ft was 375ft per min in the 1st case and 397ft per min in the 2nd case. The 1st Test was carried out in turbulent conditions.
In common with other electrical instruments fitted 2 Radiator thermometers gave some trouble during the Flights. They appeared, however, to be working normally at the time the Radiator suitability Tests were carried out.
High-Level Tropical Tests:
One Test was carried out in S gear using maximum permissible continuous power at 20,000 feet. The results are shown in the Appendix to Flight No.4. The figures obtained are well within the permissible limits. With the outside air temperature 27° above standard atmosphere the highest radiator reading with radiator flaps at manual-open was 100° which is 25° below normal permissible maximum and 35° below emergency maximum. With the radiator flaps closed the highest temperature reached on one Engine was 116° with the average of the other 3 at 109°. (Note: The thermometer which gave the high reading was flickering and must, therefore, be regarded as suspect). All temperatures are within the permissible limits.
The Rolls-Royce brochure figures for the Merlin 621 shows fuel consumptions which have always been regarded as unacceptably high. The fuel injector pumps, in general, have been on the high side, and have in any case incorporated tolerances of performance far too wide for acceptance in Commercial operation. On this occasion, however, the pumps had been carefully calibrated on the low side of the permitted setting and had small tolerances. The results achieved were most gratifying and in general, the figures agreed with the Rolls-Royce brochure almost exactly.
These injector pumps work on a capacity basis rather than a mass basis and therefore deliver the same quantity of fuel regardless of the specific gravity of the fuel used. Figures were obtained on practically all flights and results are plotted in figure No. 1. The AMPG on the Prestwick/Gander & Santa Maria/London seems to indicate that colder conditions improve the performance by about 2% over the figures obtained in the tropical conditions of the remaining Flights. Further figures are required for confirmation.
Oil consumption outward bound averaged as follows:-
P.O .394 G.P.M.
P.I. .382 G.P.M.
S.I. .394 G.P.M.
S.O. .362 G.P.M.
Homeward bound the consumption was:-
P.O .216 G.P.M.
P.I. .284 G.P.M.
S.I. .236 G.P.M.
S.O. .06 G.P.M. * Gauge read 30 gallons on ETA London (i.e. 6-7 above others)
Three Engine climb and 3 Engine cruising in tropical conditions both appeared to be satisfactory. Three Engine cruising is shown under the Appendix of Flight No.5, paragraph (a).
Three engine climbs are shown under Appendix of Flight No.6, paragraphs (a) & (d), and Flight No.7, paragraph (c).
(Note: 2-Engine cruising was carried out at Jamaica and with both Engines on the Port side stopped & feathered, level Flight was maintained at 6,000 feet at 2,850 RPM and +16 boost with an ASI reading of 130 Knots).
The electrical instruments undoubtedly were the source of the greatest trouble during this series of Flights. In most cases, the fault lay not with the Instrument but in the Transmitter concerned. Whether this is merely a characteristic of a new Aircraft or whether we can expect these Instruments to continue to cause trouble is at present uncertain. It is, however clear that drastic steps must be taken to obtain more reliable results from electrical Instruments.
At Nassau, the Port oleo leg (shock absorber) deflated overnight and owing to difficulties of obtaining adaptors and the fact that the compressed air supply was limited a considerable delay was caused before Departure. The Schrader valve on this oleo leg was found to be slightly loose and as a test for leaks otherwise showed negative results, it was assumed that this was the cause of the deflation.
Many minor details of the Aircraft are unsatisfactory and must be rectified:-
1. Fuel Gauges poor.
2. Tank Cocks at present inaccessible in Flight must be made accessible.
3. Pilots’ seats so close to Pedestal that ingress & egress are difficult, (modify seats).
4. Light intensity of centre Instrument Panel too low (compared with Starboard Panel which is on the same Dimmer switch).
5. Noise level too high (particularly where no sound-proofing is provided, e.g. in a small compartment at the rear of the forward Passenger Cabin. Tailpipes must be fitted at least to inboard side of inner Engine. Escape Hatches & Entrance Door require additional sealing rubbers to improve Sound-proofing).
6. Vibration: No carpets were fitted in this Aircraft but even allowing for this it appears that more vibration is transmitted to the Fuselage than in most modern large Aircraft. This is particularly noticeable in the centre section compartment.
7. Ventilation of the Lavatories & Galley most unsatisfactory.
8. Electrical Turn & Bank Indicators must each be provided with a switch immediately under the Instruments.
9. CSUs appear to be sluggish.
10. As there are only 2 Generators fitted, the electrical Services would be overloaded if Galley Services, Cabin Lights, Ventilating Fan & Radio were all working at Take-off and inner Engine failed. This overloading would result in a very slow Feathering, and it is essential, therefore, that standing orders provide that Electrical Loads be kept to an absolute minimum during take-off & landing.
11. Electrical Generator cut off switches are at present unprotected and can be knocked off accidentally.
12. Refuelling System needs further investigation to determine Fuel Capacity when Refuelling over the top & Fuel capacity when pressure Refuelling, – consistency of these figures to be checked.
13. The clear view panel on each side of the Cockpit jams the control wheel and if the panel is accidentally left open this could be dangerous. Hinging it on the trailing edge of the Panel would be an improvement.