Overview

Experience with the manually operated seats had shown that a number of fatalities had occurred, due to unconsciousness after ejection, inaction due to circumstantial stress, or lack of time to carry out the necessary manual operations when ejecting at low altitudes. Accordingly, effort was concentrated on producing a simple, yet effective, fully automatic ejection seat, capable of being produced in quantity, reliable in service, and designed to permit the retrospective conversion of most of the existing manually operated seats already installed in Service aircraft.
In the design of the first automatic seat, it was decided to house the personal parachute in a container in the back of the seat and the dinghy pack in the seat pan, to facilitate the use of the drogue to effect deployment of the parachute. It was also necessary to devise some means of disconnecting the drogue from the seat at the correct time and transferring its pull to the parachute, and simultaneously a means of releasing the occupant complete with his parachute and dinghy pack from the seat.
On the Mk. 1 seats, the drogue had been attached to the top of the seat by a solid shackle. This was now replaced by a "Scissor Shackle", capable of being opened automatically at a pre-determined time.

 Specifications

 

Specifications	Mk 2 (Typical)
Operating ceiling	Unknown
Minimum height/speed	Unknown
Crew boarding mass range	70.4 to 101.7 kg
Crew size range	5th to 95th percentile
Maximum Speed for ejection	400+ KIAS
Parachute type	Irvin I 24
Parachute deployment	Automatic
Drogue parachute type	24 in. Later versions 22 in. controller drogue and 5 ft
	stabiliser drogue
Drogue deployment	Drogue gun. Initiated by 1 sec clockwork
	time-delay, tripped by short static line
Harness type	Type 1 to 4
Ejection seat operation type	Ejection gun
Ejection gun	Early version - two cartridge, 60 ft/sec
	Later versions - 50 ft/sec
	Later versions - 80 ft/sec
Ejection initiation	Face screen firing
Barostatic time-release unit	Yes
Manual override handle	No, but provision for manual separation
Timers	Time-release unit for man/seat separation
Seat adjustment	Up/down
Arm restraints	No
Leg restraints	Integral thigh guards and foot rests
Oxygen supply	Bottled oxygen
Personal survival pack	Liferaft pack
Aircrew services	No
Command ejection	No

How it works

Face screen seat firing handle pulled
Two cartridge ejection gun fires, seat moves up guide rails
Emergency oxygen tripped
As seat rises, static line initiates time-delay which fires drogue gun after 1 sec
As seat rises, static line initiates time release unit
24/22 in. dia then 5 ft dia drogues stabilise and slow seat

 Above 10000 ft
     - barostat prevents operation of time-release mechanism

 Below 10000 ft
     5 sec after initiation of time-release unit plunger releases scissor shackle to
     - separate drogue from seat
     - transfer pull to canvas apron positioned between parachute and its container
     - release face blind

Canvas apron tautens and tips aircrew forward out of seat
Parachute withdrawal line, attached to apron, pulls parachute pack closure pins and
  apex of parachute from pack
Parachute deploys, drogue and apron still attached
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

Variants