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Aviation History
1948
1948 - 1660.PDF
422 FLIGHT OCTOBER ym, 1948 Annular Tempest 6 In the Air ballast has been placed near the tail and ioi that reason the aircraft is limited to accelerations of 4|g But foi this, more might have been seen of the aircraft in displays, and perhaps it might have competed at Lympne. It seems fairly certain that the absence of the chin radia- tor has resulted in a smoothing-out ol airflow around the tail surfaces, and this is felt particularly at low speeds The cockpit of the Tempest is roomy and comfortable. but does not quite come up to the standard of the later jet fighters in regard to grouping, arrangement of instru- ments and simplicity. There are a number of controls to find and understand, and the hydraulic services are not self-neutralizing after operation. Boost, pitch, mixture and radiator need to be watched, and flap and undercarriage selection and locking is not quite as simple as on later aircraft Again, many pilots are now becoming spoiled by the all-round good view from the tricycle tail-up jets, and as a result the size, height and length of a Tempest as seen from the cockpit are slightly alarming. Pre-flight Briefing A tew minutes' briefing from Jack Olver, Napier test pilot who has done many hours of development flying on this aircraft, sufficed to clear up doubts and' remind me of the sequence of operations, and on the second cartridge the Sabre was away. At first I taxied painfully slowly and care- fully (sitting as heavily as possible on the back end of my parachute) feeling con- vinced that with so much forward of the cockpit a hollow in the grass or too hard a nip on the powerful brakes would put me on my nose. However, I soon found that these fears were ungrounded, and pro- ceeded to get on with the job more confidently. Take-off on this Napier-Tempest from the fairly rough grass field at Luton calls for no special comment. I had been told that +9 lb boost at 3,750 r.p.m. was adequate, but +15 lb at 3,850 was available if I preferred it. Swing ten- dency was quite pronounced after open- ing up, but easy to control. In an en- deavour to watch dials and airfield both at the same: time, I made what might be called a two-tone take-off. The urge and noise shortly after moving off was very considerable with throttle and r.p.m. at the high stop, so after a hundred yards or so I eased back to a less urgent-sounding power output at around +9 1b boost and climbed com- fortably away at 2,500 ft/min and 200 m.p.h. I had expected that the Sabre with its 24 cylinders and sleeve valves would be particularly smooth in operation, and, in fact, it is so, though not quite as smooth as I had expected. When this point was mentioned after landing, I \vas informed that any roughness can be attributed to distribution. It is no mean problem to arrange even distri- bution to the 48 widely dispersed inlet ports in the sleeves. Strangely enough, the Sabre VII which has the highest boost pressure of any of the Sabre series, has proved to be exceptionally smooth. This may be due to the water/methanol injection. Speed builds up rapidly in level flight and quickly reaches around 350 -^ " Flight " photographs. These three portraits provide a most interesting comparison BBlWu.ii lilt j* 39O Tempest 6 with chin radiator, the experimental Tempest 6 with annular radiator, and the same aircraft in its latest form with ducted spinner and annular radiator. m.p.h., and it is apparent that the airframe is very clean. Roll performance is good, particularly in view of the absence of tab assistance on the ailerons. One complete roll at about 300 m.p.h., which I timed roughly, took rather less than 4 seconds. Stalling qualities have, it seems, been made a little more gentle, and at a weight of around 12,000 1b with every- thing up, the engine-off stall occurs at approximately 105 m.p.h. Some warn- ing signs a few m.p.h. faster are fol- lowed by snatching at the left aileron. Recovery was rapid. The standard machine is stated to stall at 108 m.p.h. I.A.S. at 12,300 lb weight and at 92 m.p.h. with flaps and wheels down. On the approach I was interested to feel the changes of trim as services were operated. Flaps down produced a fairly pronounced nose-down tendency, wheels down more nose-down, but radiator gill opening had no effect at all. The opening action for the annular radiator, it will be remembered, is a rearward movement of the annular "gill." It is probably on landing that their difference between standard and anntife lar Tempest 6 is most easily detected-^ for control on holding-off remains posfe five and sensitive until the actual touch-1 down, and the aircraft can be felt dowtf on to three points in true Tiger Moth style. A slight swing may try to develop on the landing run, but, as ot»- all occasions on the ground, th# Tempest with its wide undercarriagf 4OO 42O 44O 46O TRUE AIR SPEED-M.P. H. 47C Performance figures for four types of Sabre- engined Tempest. . — Tempest 6 with Sabre 5 (maximum boost +15 Ib boost at 3,850 r.p.m.) and 8-blade 9-deg.-root-angle diffuser. Same aircraft fitted with 12-blade 13-deg.-root-angle diffuser. Standard Tempest 6 with Sabre 7 (maximum boost +I7£lb boost at 3,850 r.p.m.) Tempest 6 with Sabre 5A, ducted spin- ner and annular radiator, and 12-blade 13-deg.- root-angle diffuser, as described in this article.
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