The Mk. 2 automatic seats were successful in providing safe escape from the aircraft in service at the period, but there was still room for improvement at very low altitudes and very high speeds. In addition, the advent of aircraft such as the Javelin and the V bombers with their high fin projections and higher operating speeds, made it necessary to increase the height of the ejection trajectory, any increase also improving the chance of a successful ejection at low altitudes.

- Face screen seat firing handle pulled
- Canopy jettison initiated (if fitted)
- Ejection gun fires, seat moves up guide rails
- Emergency oxygen tripped
- As seat rises, static line initiates time-delay which fires drogue gun after 0.5 sec
- As seat rises, static line initiates time-release unit
- 22 in. dia then 5 ft dia drogues stabilise and slow seat

- Above 10000 ft

- barostat prevents operation of time-release mechanism


- Below 10000 ft

- 1.5 sec (3 sec on earlier Mk3) after initiation of time-release unit the plunger releases scissor shackle to
- transfer pull of drogue to lifting lines of parachute, releasing it from seat
- release face blind
- Drogues deploy main parachute, aircrew separates from seat
- Normal descent
- In the event of failure of time-release unit
- aircrew pulls D ring on parachute harness. This pulls slide disconnect pin which disconnects withdrawal line from parachute
- pulling D ring also removes canvas flap from second D ring
- aircrew pulls second D ring to operate parachute