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Aviation History
1945
1945 - 0434.PDF
250 FLIGHT Rocket-Assisted -off C. B. BAILEY-WATSON Description of Installations and Method Used by Fleet Air Arm Carrier "borne Aircraft TIE evolution oi a practicable method ior assistingthe take-off of aircraft either by reason of the loador the desirability of reducing take-off time and dis- tance has been a problem that has exercised the ingenuity of aeronautical technicians for a lengthy period. Many methods have been suggested, some of which have been seemingly fanciful; but we have direct evidence of the practicability of two diverse systems in (i) the Short-Mayo composite arrangement, and (ii) the use of rockets. So far, at least in this country and also in America (where rapidity of uptake was again evidenced), the use of rockets for take-off assistance has been confined to naval aircraft, primarily for flying off the baby flat top or " VVoolworth " carriers; but a photograph of an interesting application was published in the December 28th, 1944, issue of Flight which showed a Martin Mariner flying boat taking-off with "squirt" assistance and producing a somewhat anadyo- mcncan effect. This particular application is of more than passing interest because it implies that the assistance is provided for reasons of take-off weight, although, of course, a boosted take-off would be useful for times when the water surface conditions were unfavour- able. However, our use of rocket assistance has, so far, been confined to reducing the take-off time and distance by giving the aircraft a largely increased tractive thrust and consequently accelerating it very rapidly to its take-off speed. For this purpose a standard rocket was developed by the Pro- jectile Development Department of the Ministry of Supply for applica- tion by the Aero Department of the Royal Aircraft Establishment who were responsible for all the aero- nautical side of research and development work of the project. The Heston Aircraft Company, Ltd., were entrusted with the de- sign and manufacture of a practic- able scheme of mounting and jettisoning, and this concern may SPRING-LOADED HOOK Detail of anchorage and adjustment ofSeafire rocket carrier box to upper surface of wing trail1 ng edge. take the credit for evolving a simple and straightforward solution to a part of the problem which may well have been imbued with expensive and unnecessary complexity. The first aircraft to be equipped with an operational cate- gory installation was a Vought-Sikorsky Chesapeke; a trial installation was made and proved eminently successful; however, for other reasons the Chesapekes were not devoted to operational service with rocket-assisted take-off gear but were employed as trainers. After this, the Seafire was equipped for rocket assist- ance, and uses four "tubes "—two per side—the urge from which will get the machine into the air in approximately four seconds and within a distance of 200ft. from rest. The standard rocket as now used is comprised of a 5m. dia. cold-dravm steel tube, 41m. long, of about Jin. wall thickness, and with a venturi ejection orifice incorporating a four-inch divergent nozzle ; in this case is contained 26 lb. of cordite, the total rocket weight being 66 lb. Detona- tion, or, perhaps more accurately, firing, is electric, and the mean thrust developed by the complete installation is approximately 4,400 lb. which, considering the mean speed during the aircraft's acceleration, S about an equivalent of the thrust production from three Merlins at that speed. Actual acceleration with rocket assistance is increased by nearly foyr times over that for the normal unassisted take-off, for, it should be remembered, the rocket thrust is directly applied and in- volves no indirect transmission losses. Maximum thrust is de- veloped at about 0.1 sec. after fir- ing, and then a small drop occurs to a value which is maintained roughly constant up to the take-off point, after which it drops appre- ciably and rapidly to zero corres- ponding with exhaustion of the charge. Design of the rockets and installations has been very clever in that the aircraft is, in each case, airborne by the time the charge is spent, i.e., within 4 sec. UPPER SURFACE QF WING TRAILING EDGE
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