MK8 EJECTION
SEATS
40 ejections using a Mk8 ejection seat Over 560 Mk8's currently flying in Tucano

Following development of the highly successful Mk10 rocket assisted ejection seat, a simplified, lightweight variant of this seat, designated the Mk8, was introduced for primary trainer aircraft, such as the Embraer Tucano. The most significant design simplification was the removal of the rocket motor, to save weight. In most other respects, the Mk8 seat retains the excellent design features and functionality of the Mk10 seat. The Mk8 seat provides runway level escape at speeds down to 70 knots, and has a maximum escape speed capability of 425 knots.

The Mk8 seat is currently in service in the Embraer Tucano, which is operated by the following countries: Angola, Argentina, Brazil, Colombia, Egypt, Honduras, Iraq, Kenya, Kuwait, Mauritania, Paraguay, Peru, United Kingdom and Venezuela. To date, there have been 40 ejections from a Mk8 ejection seat.

Operating Ceiling 50000+ ft (15,250m)
Minimum height/Speed Zero/70 knots in near level attitude
Crew boarding mass range 78.2 to 116.2 kg
Crew size range 5th to 95th percentile
Maximum Speed for ejection 600 KIAS
Parachute type GQ Type 1000 Mk 2
Parachute deployment Drogue assisted
Drogue parachute type 5ft
Drogue deployment Drogue gun. Initiated by trip rod
Harness type Combined
Ejection seat operation type Ejection gun
Ejection gun Single, two stage
Gun stroke length Variant dependent
Ejection initiation Handle on seat pan
Electronic Sequencer No
Barostatic time-release unit Yes + g-restrictor. Initiated by trip rod
Automatic back-up unit No
Manual override handle Yes
Timers No
Seat adjustment Up/down. Actuator operated 28 Vdc
Arm restraints No
Leg restraints Yes, two garters
Oxygen supply Bottled emergency oxygen
Onboard oxygen generating system connection
Personal survival pack Yes
Aircrew services Oxygen (main and emergency) and mic/tel
Command ejection No
Canopy jettison No
Miniature detonating cord No
Interseat sequencing system No
  • Tucano
  • Seat firing handle is pulled, causing seat initiation cartridge to fire
  • Harness retraction unit operated
  • Primary cartridge fired causing inner and intermediate pistons to rise, releasing the 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 disconnect
  • Emergency oxygen trips
  • After the delay mechanism has operated, the 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 8000ft 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 pilot in the 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 the drop line below aircrew - Normal parachute descent follows
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