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 GR5 (AV8B).

Specifications

 

 

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Gas-operated sears withdrawn from parachute deployment unit (PDU) rocket and barostatic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 harness 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