thumb|Concorde skin temperatures. They depended on the balance of heat transfer from the boundary layer, heat picked up from solar radiation, heat radiated back from the surface to the atmosphere, and heat transferred to the internal structure.</ref> As the fuselage heated up it expanded by as much as . The most obvious manifestation of this was a gap that opened up on the flight deck between the flight engineer's console and the bulkhead. On some aircraft that conducted a retiring supersonic flight, the flight engineers placed their caps in this expanded gap, wedging the cap when the airframe shrank again. To keep the cabin cool, Concorde used the fuel as a heat sink for the heat from the air conditioning. The same method also cooled the hydraulics. During supersonic flight a visor was used to keep high temperature air from flowing over the cockpit skin.
thumb|Concorde skin temperatures. They depended on the balance of heat transfer from the boundary layer, heat picked up from solar radiation, heat radiated back from the surface to the atmosphere and heat transferred to the internal structure.</ref> As the fuselage heated up it expanded by as much as . The most obvious manifestation of this was a gap that opened up on the flight deck between the flight engineer's console and the bulkhead. On some aircraft that conducted a retiring supersonic flight, the flight engineers placed their caps in this expanded gap, wedging the cap when the airframe shrank again. To keep the cabin cool, Concorde used the fuel as a heat sink for the heat from the air conditioning. The same method also cooled the hydraulics. During supersonic flight a visor was used to keep high temperature air from flowing over the cockpit ski,n.