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Aviation History
1948
1948 - 1066.PDF
6o FLIGHT JULY 15TH, 1948 The recording accelerometers installed in the aircraft are the Peravia (left) low-speed unit covering a + 10 to — 4 g range, and the Barnes highflow-speed unit covering a range of ± 5 g. Gust Hunting A.M.I.Mech.E., A.F.R.Ae.S., who is assistant to Mr. N. E.Rowe; whilst actually based at Cranfield are Mr. D. M. Davies, M.A., the scientific officer, Captain T. T. Thomas, D.F.C.and Bar, F.R.Met.S., research pilot, and Navigation Officer D. L. Jones. For six years during the war, Dr. Hislop wasin charge of the high-altitude flight, and from thcfe went to R.A.E., Farnborough, for two years, prior to joining JB.E.A.in January, 1947. Mr. Davies went direct from Cambridge to the Performance Department of M.A.P., in 1942, where i»ostof his time was concerned with high-speed fighters;' he joined^ B.E.A. in June, 1946. Both Captain Thomas and NavigationOfficer Jones gained a great deal of experience on Mosquitoes during their war service in the R.A.F., Capt. Thomas havingserved in the Pathfinder Force, whilst N/O. Jones was engaged on P.R. work with Mosquito 16s and 34s. The task facing the Gust Research Unit has something of theneedle-in-a-haystack quality, in that there is no factual evidence available anywhere to show why clear-air gusts occur,how frequently they occur, at what heights such gusts aFe most markedly violent, the amplitude of gust velocities likely to bemet, nor whether the gusts are a function of terrain conforma- tion, a result of particular meteorological conditions, or acomplex of both. Although, therefore, there is some justifica- tion for the needle-in-a-haystack analogy, if, for example, aftera year's flying totalling 500 to 600 hours, few data on clear-air gilsts are amassed, it will be a negative answer of some positivevalue. It is entirely possible that a great deal of flying will be putin to get only a few results, but this would afford some indica- tion that the incidence of gusts may not, after all, be ofserious moment. It is, however, much too early as yet to hazard any ideas on the subject, and for the very reason thatthe whole business is so tenuous, there is a cBstain danger in being over-hasty in drawing conclusions with#wt the amassingof as many fundamental data as possibl^^/"*^ So far, a total of about 120 flying houjsnas been compiled, Resplendent in the grey and red B.E.A. colours, Mosquito G-MZE shares with its fellow, G-AJZF, the distinction of being the only aircraft of its type ever granted a full C. of A. some 84 of which have been on useful flights, that is to bay,sorties during which positive gust results have been obtained. These positive results were gained on four occasions, viz , ona flight to Inverness, where gusts of 0.5 g were encountered at 18-19,oooft over the Cairngorms; on flights to Lisbon and back,when gusts of 0.3 g were found over the Brest Peninsula at 25-30,oooft, and also north of Luarca, off the coast ofnorthern Spain at 30,000ft; and on a flight back from Copen- hagen, when gusts of 0.3 g were encountered at about 32,000ftover Heligoland. The velocities of these gusts were respectively n.4ft/sec in the instances of 0.3g acceleration, and igft/secfor the 0.5 g acceleration, the gust velocity being calculated , from the recorded acceleration, equated with wing loading,relative air density, alleviation factor, slope of lift curve and indicated air speed. 0 The Flight Plan The flight plan adopted on search flights is to climb steadilyon course at the aircraft's normal climbing speed up to maximum height, about 36,000ft, then descend at a constantI.A.S. of about 220 m.p.h. to 20,000ft, thereafter climbing again to maximum height, this process going on throughout theflight, with the maximum height increasing to about 40,000ft as the fuel load is decreased. The sketch map shows the flighttrack of the Cranneld/Lisbon sortie, together with a vertical section illustrating the altitude flight path. At each 5,000ft-interval of climb and descent, the Peravia recording accelero- meter is run for about one minute to take sample conditions.When gusts are encountered, the first thing Captain Thomas has to decide is whether, allowing, say, one hour for gustinvestigation, he can continue on to the planned destination, whether there is an alternative airfield which he could use ifnecessary, or whether it would be best to return to base. Having reached a decision on this, the first research requirementis to determine the thickness of the gust layer, and this is done' by alternately diving and climbing through the layer severaltimes. The second requirement is the taking of ambient tem- perature records at i,oooft-intervals from 6,000ft below thegust layer up to 4,000ft above it, the temperatures being taken during short, level runs through thelayer, so that figures are obtained of the ambients on each side of, andinside the layer, thus allowing a tem- perature gradient to be plotted. Thenext thing to determine is the hori- zontal extent of the layer, this beingdone by flying a form of square- search; the position-plotting of thegust region is fixed by Gee if it is in an area of Gee coverage, or otherwiseby D.R. navigation. Necessarily, the navigator's workmust be of a sufficiently high standard to allow the precise fixture of thelayer position, and it means 100 per cent concentration on navigation fromtake-off to landing, since gusts may well be encountered anywhere en (Continued on page 76.)
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