A gas seal for aerospace engines has a stationary seal housing, a rotating seal plate mounted on the engine drive shaft and a carbon ring seal movably supported in the housing with a face which mates with the face of the seal plate to create a gas seal therebetween. A plurality of flexible pins have first ends supported on the housing and second ends slidably connected with the carbon ring seal to permit the latter to shift axially. A plurality of compression springs bias the two seal faces together. The housing has a first twist lock which selectively engages a second twist lock on the carbon ring seal to movably retain the latter in the housing. The second ends of the spring pins resiliently deflect during mutual rotation of the carbon ring seal and the housing to facilitate engagement and disengagement of the first and second twist locks.