FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1946
1946 - 0203.PDF
JANUARY 31ST, 1946 FLIGHT A long nose and a five-blade Rotol characterised the XIV, the later fighter-reconnaissance version of which is seen in a snow-coveredsetting. The last of the Spitfire series, the XXI and XXII, are in formation on the right. the left, one merely trimmed this tendency out on the rudder bias until, by virtue of various complicated aerodynamic forces, the aircraft would fly level while, of course, skidding quietly along to the left. The top needle of the Watney, Combe and Reid showed the amount of this skid, and there you were. This amount varied in complicated proportion to the amount by which one's aircraft would normally, when properly trimmed directionally and left to itself, have been trying to roll. It was a quite mechanically standard method of indicating the amount of lateral trim error, and all pilots would produce the same answer for the same air- craft at the same speed. Unfortunately, however, four degrees of indicated skid, say, were by no means the same as twice two degrees of skid when translated into lateral trim terms. The unfortunate rigger had to think that one out, and he very quickly learned to do so. There were, occasionally, those awful moments when an aircraft off the production line would be tending to roll violently over one way while already having a near-limit upfloat tendency on the opposite aileron. Obviously, it was not possible to dress the aileron to correct the trim without still furthei increasing this upfloat. Results could sometimes be obtained by a judicious hammering of the shrouds, but it usually meant a complete aileron change and sometimes even a complete wing change. Pleasure Riding By way of reliei from the old original pressure-cabin types, the Mark XI P.R.U. Spitfire was quite the simplest and most easy-going affair designed for medium high- altitude work and for a high speed. There was no pressure- cabin and, most delightful of all, no gun-sight to restrict one's forward view. In place of the bullet-proof screen was a pleasant one-piece moulding which, with the canopy, gave an unrestricted view of the entire upper hemisphere. It carried no guns, though there were two extra wing tanks well outboard, the contents of which were indicated on two extraordinary gauges which seemed always to indicate the same amount, whether the tanks were empty or full. The line to take was that of running each of them dry—then at least you knew where you were. First of the Griffon-engined Spitfires, the XII seemed to behave simply as a Mark V, with more power and a swings in the opposite direction, i.e., to the right. In the early days, when flying these later Marks, it required something of an effort of memory to set the rudder bias correctly— though nothing very terrible happened, other than to the muscles of the left leg, if the fact that the aircraft was Griffon-powered had been forgotten. But the XII had a new and rather special noise which we were to learn to like as more and more XIIs and XIVs came into the market. Remembering the old days of the II, we were once again to become accustomed to the cartridge-starting procedure. Although the actual stalling speed, even at the greater all-up weight, appeared to be virtually unchanged, the XII and later Griffon Marks had a pleasant way of staying much more firmly on the ground after touchdown in rough conditions One of the more mysterious troubles with which aircraft are sometimes beset appeared with a particular XII which had already done quite a good deal of flying. This aircraft developed a power-surging tendency which was tantamount almost to a series of dead cuts—and always at high speeds. The constant-speed unit was at first suspected, and hopes of a cure were high when the inside of the mechanism was discovered to be both worn and very dirty. But the surging continued. In turn the c.s.u., the airscrew, and even the carburettor were changed, with no perceptible result. Only a long series of very earnest diving tests at different boosts and c.s. settings brought to light the definite fact that the violence of the surging increased primarily with the speed—320 m.p.h. appeared to be the critical "start- ing" speed—and, to a lesser degree, with the number ol the revolutions and the degree of boost. Obviously, there- fore, the trouble was bound up with some variation in "ram" effect, and it was eventually discovered that, through a fault, the shape of the intake was being changed by the increasing air pressure. It was not actually closing up so much as distorting, and neither the boost control nor the c.s.u. could cope with the violent alternations in outer intake pressures. Some of the characteristics of the Spitfire family, and oi
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
