Introduction of the rocket pack to the range of Mk. 4 and Mk. 5 seats created the basic Mk. 6 and Mk. 7 ranges respectively. However, many of the Mk. 7 range of seats were subsequently embodied with additional improvements in design such as Power Retraction Systems, Remote Fired Rocket Systems and Sequencing Systems as later described. The Mk. 8 seat (developed for the T.S.R.2 aircraft), was a rocket assisted seat and was undoubtedly the most advanced aircrew escape system produced up to that time. Despite the unfortunate cancellation of the T.S.R.2, much valuable experience was gained, which was fully exploited in later designs.
- Seat firing handle pulled causing seat initiation cartridge to fire
- Harness retraction unit operated
- Primary cartridge fired causing inner and intermediate pistons to rise, releasing top latch
- Secondary cartridges fire in turn as seat rises
- Electrical connections separate disconnecting seat actuator circuit
- Leg restraint lines draw back and restrain aircrew’s legs
- Leg restraint lines become taut and rivets shear, freeing lines from ejection gun cross beam
- Trip rods withdraw sears from drogue gun and barostatic time-release units
- Onboard oxygen and mic/tel disconnected
- Emergency oxygen trips
- After delay mechanism has operated, drogue gun piston fires
- Deployment of drogue stabilises and retards the seat and aircrew
- Low altitude/High speed –
- Seat descends stabilised by drogue
- Barostatic time-release unit completes run and fires
- High speed/high altitude –
- Barostatic capsule operates to prevent parachute deployment above pre-determined altitude
- Barostatic controlled g-switch delays parachute deployment above 8000 ft until speed and g-force are reduced
- Barostatic time release unit operates below pre-determined altitude, completes run and fires
- Manual separation (override) used if automatic system fails
- Gas from cartridge used to free drogue shackle link, release parachute mechanical lock, operate upper harness locks and lower harness release mechanism to free lower harness lugs, negative-g strap and leg restraint lines
- Drogue withdraws parachute from container
- Sticker straps momentarily hold aircrew in seat
- Parachute develops, lifts aircrew and survival pack from seat and pulls sticker clips from clips causing aircrew and seat to diverge
- Aircrew operates survival pack release strap which lowers survival pack on drop line below aircrew
- Normal parachute descent follows