Martin-Baker developed the Mk.12 seat to provide a cost effective escape system with an improved low speed and adverse attitude recovery capability. The Mk.12 seat introduces a significant improvement in seat performance over the speed range zero to 625 knots and from ground level to the service ceiling of the aircraft or the limit of the pilot’s protective equipment. The seat has the capability of sensing airspeed and adjusting its mode of operation accordingly. The Mk.12 seat has been qualified for the UK Royal Air Force Harrier GR7 (AV8B).
- Seat firing handle pulled causing seat initiation twin cartridges to fire
- Night vision goggles separation initiated
- Miniature detonating cord trip initiates canopy fracturing system
- Harness retraction unit operated
- Gas-operated sears withdrawn from parachute deployment unit (PDU) rocket and barostatic time-release unit (BTRU)
- Primary cartridge fired causing inner and intermediate pistons to rise, releasing top latch
- Secondary cartridges fire in turn as seat rises
- Seat electrical supply and onboard oxygen supply hose disconnected
- Emergency oxygen trips
- Personal equipment connector aircraft portion removed from seat portion by static line to disconnect anti-g suit hose and mic/tel connections
- Leg restraint lines draw back and restrain aircrew’s legs
- Leg restraint lines become taut and rivets shear, freeing lines from floor brackets
- Pitot heads operated by static lines
- Mode selector g-switch operated by static line
- Remote rocket initiator operated by static line, cartridge fires to ignite rocket pack
- Rocket pack sustains upward thrust of ejection gun
- PDU rocket fires 0.3 sec after ejection to remove parachute container lid and deploy drogues to stabilize and decrease velocity of seat
- Low speed AND low altitude
- Gas from PDU fires mechanical mode selector cartridge to operate BTRU in 0.3 sec,
free drogue shackle link and release parachute mechanical lock
- Gas from BTRU cartridge used to operate upper harness locks and lower harness release mechanism to free lower harness lugs, negative-g straps, leg restraint lines and personal equipment connector man portion
- High speed OR high altitude
- Mechanical mode selector inhibited
-Barostatic capsule and g-switch operate to prevent parachute deployment above pre-determined altitude and speed
- BTRU completes run below pre-determined altitude and speed to fire cartridge in 1.1 sec
- Gas from BTRU 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 straps, leg restraint lines and personal equipment connector man portion
- Manual separation (override) used if automatic PDU/BTRU system fails
- Secondary drogue withdraw 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
- Pulling survival pack from seat causes automatic deployment unit to operate which lowers survival pack on drop line below aircrew
- Manual deployment used if automatic system fails
- Normal parachute descent follows
- On immersion in water, automatic liferaft inflation unit operates to inflate liferaft