FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1947
1947 - 0008.PDF
FLIGHT JANUARY 2ND.. 1947 Naval Aircraft Design Requirements Discussed by Supermarine Technical Staff LECTURING before the Southamp-ton Branch of the Royal Aero-' nautical Society on December nth, Mr. A. N. Clifton, M.B.E., B.Sc, F.R.Ae.S., chief of Vickers- Armstrongs (Supermarine) Technical Office, outlined the development of naval aircraft and explained some- thing of the technical requirements in modern machines for naval use. Naval aircraft design, he said, was really ordinary aircraft design made more difficult. The first handicap was the severity of take-off requirements. Although a certain amount of wind due to the ship's speed could be relied upon, long runs were out of the ques- tion and catapult spools and accelera- tor hooks must be provided and the aircraft must have the necessary strength to withstand the added forces imposed. Provision for rocket accelera - ting gear must also be made. Control characteristics and view must be specially studied and undercarriage shock absorption and rebound damp- ing of a high order were necessary. An arrester hook and an airframe suitably strengthened for this attachment were other requirements. Radio equipment for naval use was more complicated and heavier than that required on landplanes and provision for wing fold- ing and restrictions on dimensions were necessary. To indicate the increase in weight necessary, Mr. Clifton gave an esti- mate for a fighter, showing that the additional weight for a machine of approximately io,ooolb was at least 45olb made up as follows: — Accelerator books and pro-vision for KATOG 5olb. Arrester hook 6olb. Extra radio 3olb. Folding wings, slinging and lashing points iGolb. Longer stroke undercarriage. . 401b. Provision for oil heating, fuel draining, etc 5lb. 345'u-E-'xtra structure weight at 3c per cent / 1051b. TOTAL INCREASE /. 4501b. Landing are^of an air-craft carrier and an airfield runway compared. LANDING AREA A/C CARRIER 2OPFSJ DECK AIRFIELD RUNWAY I5OOYDS- Examining the take-off question in detail, Mr. Clifton dealt first with the normal take-off, using engine -power alone. Bearing in mind that more than half the deck might be required for aircraft landing on, he said, this was only possible under favourable conditions. Partially lowered flaps were essential and a contra-rotating airscrew, which eliminated swing, was desirable. Under less favourable conditions rockets could be used for acceleration. These were carried in jettisonable con- tainers and delivered their thrust ap- proximately through the C.G. in side elevation. The standard rocket gave a thrust of i,2oolb for four seconds and weighed 661b, and a container for two rockets weighed 5olb. Four rockets might be carried on a fighter to attain a 500-ft run in still air, or a 250-ft run against a 20-knot wind. This worked out at an average acceleration of about 1 G, of which I G might be provided by the engine. / Finally there was the accelerator, a 2000 woo 10 20 30 DEFLECTION OF FLAP- DEGREES 40 Variation of take-off distance with flapdeflection. (Naval fighter with 47-5 lb/ sq ft wing loading.) mechanical device. The British type consisted of a trolley which was rather similar to the naval catapult in that it engaged four spools on the airframe. The forward attachments supplied the thrust and floated vertically while the rear ones held up the tail. The trolley was hauled by a rope running below a slot in the deck and the motive power was compressed air or cordite. With a maximum acceleration of about 2| G (or a mean acceleration of if G) plus airscrew thrust over a distance of 100 ft the speed at the end was about 60 knots, relative to the ship. To this speed could be added an allowance of 20 knots for the wind speed over the deck, giving a total airspeed of 80 knots. A simpler method was developed by the U.S. Navy and had since been 250 ' 2<3 CONTRA ROTATING AIRSCREW PLUS 4 ROCKETS 2x3 CONTRA-ROTATING AIRSCREW PLUS 1_ 2)S?ACCELERAT0R \ 0 5 10 15 20 25 30 THRUST (1000 POUNDS) Variation of take-off distance in 27knot wind with thrust. (Naval fighter with wing loading of 47-5 lb/sq ft.Take-off power 1,900 b.h.p. adopted here. This generally used two hooks on the aircraft with a strap to engage these, and a claw projecting through a slot in the deck and pro- pelled by the accelerating mechanism. The aircraft ran on its own main and tail wheels and at the end of the run the cable was left behind and fell off the hooks. The loads on the under- carriage were fairly severe though generally speaking not severe enough to call for increased strength. These loads were due to the downward slope of the cable, and resulted in the machine running along on nearly flat tyres, The cable direction was care- fully selected to pass just below the C.G. to avoid nosing over and too great a tail-wheel load. The advan- tages of this method were a minimum of gear above deck, quickness in opera- tion (because no trolleys had to be lined up and engaged) and simpler and lighter attachments on the aircraft. Launching' Rate An essential requirement for take- off was a high rate of launching. For one thing the aircraft might be wanted t., in a hurry, and secondly the carrier . | might have to lose station relativist"- accompanying ships due to the neces- sity to steam into wind. Under favour- able conditions, a squadron of twelve aircraft could be launched by accelera- tion in about 10 minutes. In that time the remainder of the Fleet might be 7 or 8 miles ahead. Landing-on was a different matter altogether. It was a hazardous pro- cess calling for a high degree of co- ordinated skill on the part of the pilot and the " batsman " directing him. In the air perfect control was essential, and once on the deck the aircraft must not bounce. la the latter respect aero-
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
