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Aviation History
1952
1952 - 0412.PDF
186 FLIGHT, 15 February 1952 direction), whilst on the left-hand screen target range is given in zenith (i.e., height). The light emission from these screens, whilst not particularly bright, would be quite enough to impair the pilot's night vision and, for this reason, the observer scans the screens through a "what the butler saw" viewing-shroud. Owing to the sharply denned demands of cockpit layout, the seats are staggered in all three dimensions. Laterally, the centre point of the pilot's seat is 8in to port of the fuselage centre-line, whilst the centre point of the observer's seat is ioin to starboard; fore and aft, the observer's seat is 15.15m abaft the pilot's seat; vertically, the observer's seat is fixed at 14.3m above the floor, whilst the pilot's seat is adjustable over a height range between 12.45m and i6.2in above the floor. Perhaps because he needs to bend forward to watch the viewing screens, perhaps because of limited space, the observer is not given a back to his seat; it is simply a pan on legs anchored rigidly to the floor. Whether any modification of this arrangement is foreseen we do not know; there are no Service trade unions. As is to be expected, the performance of-the night fighter matches that of the Trainer almost exactly, and both the two-seat versions can achieve a greater maximum speed at the higher altitudes than can the standard single-seater Vampire, this being ascribed to the enhanced fineness-ratio of their fuselage profiles, and despite the comparatively large flat area of the front screens. As may be seen from the various curves, the performance can be summarized as follows : The clean aircraft achieves its operational ceiling of 40,000ft in 16.3 min, and only slightly longer (17.5 min) is taken to reach the reduced operational ceiling of 34,000ft when the aircraft has the additional weight and drag of two 100-gal drop tanks. The complementary curves of rate of climb are particularly impressive, showing as they do that, even at the tropopause, the clean aircraft is capable of climb ing at 1,500ft min. The curve of maximum level speed represents the performance of the clean aircraft at a mean weight of 9,900 lb, i.e., with approximately half fuel used. This shows that the aircraft achieves its best speed at 20,000ft, namely, 477 kt (M 0.775). As an extension of this context, it is apposite to tabulate the limiting true Mach number for various altitudes :— Altitude (ft) Limiting true Mach number Sea Level 10,000 20,000 30,000 40,000 These figures apply to the equipment, and at low altitude the stressing limitation of 477 kt E.A.S. is the effective parameter. With drop tanks, 0.725 0.78 0.81 0.815 0.815 aircraft the limiting Mach number at high altitude is M 0.755, whilst the stressing limitation is 390 kt E.A.S. The ability of the Vampire to make high-speed turns in an astonishingly small compass is well known, but the curves of turn radii tell the story with marked effect. At 40,000ft, 400 kt represents a Mach number of 0.7 and it can be seen that, whilst the radius of steady turn is 1.95 nautical miles, the aircraft can, in fact, be pulled round at the minimum radius of 0.95 n.m. What is even more remarkable is that, at 375 kt at 30,000ft (M 0.65) it can make a 360 deg turn of but fractionally over 1 n.m. diameter. On the score of range and endurance, perhaps the most concise method of giving the performance is again in tabular form. In this context, still-air range is taken to be the total distance that can be flown after allowance for the fuel used during take-off, climb and descent; the distance covered on climb and descent is credited to the range. Altitude Sea Level 20,000 30,000 40.000 Still-air Range, n.m. 330 gal 345 535 705 760 530 gai 540 775 1,060 Cruising Speed, kt 330 gal 260 260 285 350 530 gal 260 260 285 The patrol duration of the aircraft can be set out in the same manner and, again for these purposes, is taken to mean the time left for patrol after allowance is made for the fuel used for take-off, climb, ten minutes' combat at patrol altitude, and descent; the time for climb, combat and descent is not included. Altitude Sea Level 20,000 30.000 40,000 Patrol Duration, hours 330 gal 1.20 1.30 1.45 1.20 530 gal 2.30 2.35 2.70 Mean Patrol Speed, kt 330 gal 170 230 275 335 350 gal 170 230 275 without external It must be pointed out that the figures quoted in these two tables would need to be reduced somewhat for operational purposes in order to allow for a practical fuel reserve. This is, in fact, apparent from the definitions given for still-air range and patrol duration. This brief survey of the salient performance features of the Vampire night fighter makes it clear that, even although the Venom night fighter (and, very likely, the D.H. no all-weather fighter) will give us night protection in the not- too-distant future, their smaller and less powerful brother is well fitted to carry the burden until these more advanced types are ready to take on the job. C.B.B-W. 40 wmssur r~ EXTERNAL EQUIPMENT, -KTAKC-OrT WEIGHT WITH 2«IOO GAL DROP- TANKS fTAKE'OFP WEIGHT '-. so «B,IODL ' WITHOUT EXTERNAL EQUIPMENT O I 2 3 4* B RATE OF CLIMB (ft/irfnx iOCO) 1 1 1 1 1 1 1 1 1 111 1 5 » 15 20 TIMS TO HEIGHT (mln) Family of performance curves showing respectively, from left to right, combat climb, maximum level speed, and turning performance. The maximum speed and turning performance curves are for the air craft without external equipment and at a mean weight of 9,900 lb. All curves relate to I.C.A.N, standard atmosphere conditions. (LIMITED BY ENGINE POWER) MINIMUM RAMUS OF TURN 4JO 440 4SO 480 TRUE AW SPEED (kt) SCO 520 200 1 I I I I I 250 BOO 350 400 TRUE AIR SPEED (kt)
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