AIRCRAFT HEAT EXCHANGER

A heat exchanger for heat transfer between an external first flow along a first flowpath and a second flow along an internal second flowpath, has: a first manifold (104); a second manifold (106); and a plurality of tubes (120) extending from the first manifold (104) to the second manifold (106) and having respective interiors (120) bounding respective legs of the second flowpath. The plurality of tubes (120) comprises a plurality groups of tubes (120). For each of the groups of the tubes (120): the tubes (120) of the group have first ends (126) mounted to the first manifold (104) at respective first locations; and the tubes (120) of the group have second ends (128) mounted to the second manifold (106) at respective second locations. From the first manifold (104) to the second manifold (106), each tube (120) has: an upstream concave first turn (142); an upstream convex second turn (144); and an upstream concave third turn (146); and the second locations are offset downstream along the first flowpath from the respective first locations.