SUPERSONIC AIRCRAFT BRING LUBRICATION PROBLEMS

THE ATTENTION which has been paid in both the lay and technical press to the Concorde has revealed the many problems associated with the design and construction of aircraft flying at supersonic speeds. They relate to both aerodynamic design and the materials of construction where, particularly for the latter, one of the main influencing factors is the high surface temperature caused by skin friction. In the case of the Concorde which, it is stated, has a mximum speed of Mach 2‐2 and will fly for some 60 per cent of the time at a cruising speed of Mach 2‐1, the airframe can still be made mainly from conventional aluminium alloy as are today's jets. But the surface temperature starts to rise rapidly as speed exceeds Mach 2‐2 and this will mean that before long aluminium alloys will have to be replaced by harder metals with higher weight‐to‐strength ratio, for example titanium or stainless steel alloys. At the same time it is known that surface temperatures will range from, say, minus 65°F to 450°F with some—areas e.g., engine mounts—well above 1000°F.