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Aviation History
1957
1957 - 0264.PDF
266 FLIGHT, 1 March 1957 THE FAIREY DELTA 2 Part II of the LickleyjTwiss Lecture: Flying "A Very '£ Pleasant Machine''' AS recorded in these pages last week, a "main" lecture of the RoyalAeronautical Society, with the Fairey Delta 2 as its subject, was given on February 14 by Mr. R. L. Lickley, B.Sc, F.R.Ae.S., technicaldirector and chief engineer of the Fairey Aviation Co., Ltd., and Mr. L. P. Twiss, test pilot of the company. (Mr. Twiss secured the world'sair speed record with the F.D.2 nearly a year ago, at a speed of 1,132 m.p.h.)- Last week we reported the first part of the lecture—Mr.Lickley's dissertation on the design and construction of the aircraft; and the general discussion was summarized in our news columns.Below we give points from the test pilot's contribution to the joint paper. THIS aircraft shows every promise of being a very pleasantflying machine. Soon after take-off I had confidence inthe handling characteristics, and I should like to con- gratulate all the design and engineering personnel who madethis possible." These words, said Mr. Twiss, were from the opening paragraph of his flight-test report on the Fairey Delta 2,and they still rang very true today. The great day [continued Mr. Twiss] was October 6, 1954, atBoscombe Down, and was the start of an intensely interesting development programme—not without its setbacks and excite-ments—which was highlighted last March by the gaining of the world's absolute air speed record for Britain. The early flightsfollowed the pattern of most prototype aircraft and, but for an unfortunate setback on the fourteenth flight, went very smoothly.This was the first aircraft in this country to fly with powered controls with no means of manual reversion, i.e., the controlswere entirely irreversible, the pilot's control column being purely a selection lever to a system of valves. With the system as it wasarranged, every component was duplicated except the engine. There was a pump, hydraulic supply pipes, jacks, valves, and soon, for each system. We made a large number of ground tests. An extreme case was taken—an engine seizure at altitude withthe reserve accumulator pressure at the level at which the pumps were about to cut in. Typical flight manoeuvres during a descentand landing in calm and rougher air were simulated, following the flight pattern suggested by the R.A.E. in the simulated cases 1IO 1OO- 9O- 8O- 7O- </) 40 z < 3O 2 2O 10 REPAIRS AND MODIFICATIONMODS, ' done on the Ayro 707. The results of these simulated manoeuvres were encouraging. It was found that more than 1,000 deg of control surface movement, used as required, were available. This was thought to be sufficient for an emergency let-down from 30,000ft and a landing. These ground tests were put severely to the test on flightNo. 14, when I suffered an engine stoppage some 30 miles from base, and was able to glide back and make a wheels-up landing.Further improvements have now bsen made; a ram-air-driven turbine hydraulic pump is now available for such an emergency. Control Flutter Testing. Many people ask why we took solong to work up to supersonic flight. "Hasten carefully" is the motto of a sensible test pilot and flight development team; andthere was a very special reason why the flight envelope should be extended with care. This was the first high-speed aircraft to flyin this country without any mass balance on the control surfaces. Theory had suggested that sufficient stiffness could be obtainedthrough the powered control system to guard against "classical" flutter and, that mass balance might well make things worse! Thespace was still available in the wings and fin, but approximately 1,000 1b of dead weight was saved by not fitting mass balance.However, there was still an element of doubt about single degree of freedom flutter—little practical experience of which wasavailable in the world. Of this type of control system, with no feed-back from the control surface to the stick, mild flutter maybe occurring at the control surface without any indication to the pilot. More violent flutter would of course be apparent byvibration of the whole airframe. Flight tests were therefore planned in such a way as to obtain as much previous warning ofthe onset of flutter as could be arranged. Flutter records are obtained by mounting small recordingaccelerometers in various parts of the structure. Continuous trace recordings are taken of the effect of the pilot initiating asharp deflection of all three surfaces—rudder, aileron, and elevator—under steady conditions. The measure of the dampingis then compared at various speeds and Mach numbers. These tests are very laborious, as, for reasons of safety, it is necessaryto increase the speed in small increments, processing and examining the recordsbetween each step. A deterioration in damping would act as a warning to pro-ceed in smaller increments or even to stop. The average increment of Mach numberwas 0.01, with examination of records every 0.02 over the regions theoreticallysupposed to be critical. It is worthy of note that the flight-development and maintenance team worked up to a high degree of efficiency.The aircraft would be ready to take-off on its next flight, refuelled, recordsexamined, auto-observer replenished, and so on within forty minutes. This enabledus to make four to five flights of this type in a day. Control and Stability. During theflutter testing a considerable amount of information was obtained about thestability of the aircraft. Elevator angles to trim and to manoeuvre, and so on, wereobtained throughout the flight envelope covered and conventional stability checkswere made both subsonically and super- sonically. Extensive longitudinal manoeuvr- i 8 a I 2 Q1954 isIHiNa^y15 1955 S o a K3 3 tt 8 1956 Serviceability record of the Fairey Delta from the first flight to mid-November 7956.
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