FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1950
1950 - 1838.PDF
FLIGHT, 5 October 1950 375 face junction and also sealing all lightening holes in the rear spar, which also forms the wing trailing-edge in way of the flaps. The resulting effect on the handling qualities of the aircraft was extremely beneficial, the greater part of the deficiencies mentioned above being eliminated. During the course of the engine cooling trials on the Sealand, considerable development work was carried out, not only to obtain the best cooling arrangements possible for tropical operation, but also to improve climb perform- ance. Many quite minor modifications of the type shown in the accompanying diagrams were tried and that illus- trated last was finally accepted. It will be noted that all the modifications were of a relatively simple nature, with the possible exception of the switch of the oil coolers from the top of the engine nacelles to the wing leading-edge. The resulting improvements in cooling and performance for tropical operations were far from insignificant, however. Peak cylinder temperatures were reduced by 20 deg C, oil temperatures by 150 deg C, and the rate of climb of the aircraft improved by 50ft/min. The improvement in per- formance was of particular importance in view of the inevitable critical state of affairs that exists when a twin- engined aircraft suffers an engine failure. The Sealand, being an amphibian, naturally had its problems peculiar to water operation. One of these which soon became apparent during the early water handling trials was a tendency to angle back excessively at what is known as "hump speed." All flying-boats of the con- ventional two-step variety take off from water in two distinct stages. During the first stage, up to approximately 35 knots on the Sealand, the boat is supported mainly by normal water buoyancy. The fore-and-aft trim normally increases until at the end of the buoyance stage (the " hump") the rear step lifts clear and the boat rides only on its forebody. During the second stage of the water run the aircraft is then supported partly by water planing loads on the forebody and by air-lift in the whjgs. If the change of trim at hump speed is too great (as it was with the Sea- land) there is a tendency for a porpoise to be set up during this transition period. This fault was not dangerous with the Sealant , but considerable skill and concentration on the Woo! tufting on an experimental Sealand nacelle. The curious behaviour of the tuft on the flap is evidence of flow breakway. part of the pilot was required to effect a smooth take-off. The trouble was largely eliminated by the introduction o4 \ixt strips along the afterbody chines and by sharpening the new step just forward of the retracted tail wheel, ff is believed that the angle of trim and tendency to porpoise were reduced because these sharp edges destroyed water suction on the afterbody, which was tending to keep the tail down. A similar phenomenon has recently been experienced in America. There it was found, whilst tank-testing flying- boat models, that in order to obtain realistic trims during water runs the chines of the model planing surfaces needed to be razor sharp, otherwise excessive trimming angles were obtained as experienced on the full-scale Sealand. STURCEON DEVELOPMENT The liquid-cooled Merlin engines of the twin-engined Sturgeon deck-landing aircraft are cooled by means of radiators placed in the wing leading-edges between fuselage and engine nacelles. The normal leading-edge profiles of Progressive Sealand modifications to obtain the best cooling arrangements far tropical operation and to improve Elimb performance. ORIGINAL CHI COOLER COOLING AIR TO COMPBESSOR AND GENERATOR OIL COOlEC ENTRY, BLANKED OFF COOLING AIR - 0 ENGINE ICCESSORiES U SHROUD OVER 'EXHAUST PIPE
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
