On a tour of the Blackbird I learned some astounding facts. The Blackbird, of which one model is the SR71, gets hot when flying at
2100 MPH. But how hot is really mind boggling. Especially when the age of this aircraft is considered. The first one flew in 1961, I believe. The skin around the cockpit heats to 600 degrees F! But that's nothing. The leading edges went up to 1100. And behind the engines the skin was over 3000!!! The planes would take off with 1/2 full tanks. Once airborne they would fill up from air tankers which had been aloft for quite a while at fairly high altitude to cool the fuel down. This fuel was pumped around inside the plane to cool the fuselage. You can imagine how the pilot would have cooked with the skin around him at 600 degrees. After the fuel did it's cooling job it was used in the hydraulics as the working fluid. By this time it was ready for the engines and was burned. The plane did leak fuel when on the ground. When the skin got hot the leaks were sealed. This seems to me that the outer skin must have also been the tank wall. The tanks were pressurised with nitrogen as the fuel was drawn out to prevent collapse when the plane was at lower altitude. This seems to me that what was really being prevented was the collapse of the plane itself! A truly amazing piece of engineering and still, after 45 years, the fastest plane ever built. ERS- posted
18 years ago