To suit the special requirements of the United States Navy, the Mk. 5 seat was introduced in 1957 and its production paralleled to that of the Mk. 4. In general the Mk. 5 seats conformed to the same basic pattern of the Mk. 4 and included the standard 80 feet per second gun, 1¼ second time delay with g switch and barostatic control, duplex drogue system plus all the other features necessary for their use at all speeds and heights. To meet specific American crash requirements however, the seat structure and harness were strengthened to withstand deceleration loads of 40g, instead of the 25 g British specification, resulting in a slight increase in weight.

In addition, the seats were provided with special canopy breaker peaks on the headbox to provide for the eventuality of having to eject through the canopy, standard practice on the A.5 seat installed in the Grumman 9F-8T Cougar. On the majority of the other Mk. 5 seats the American system of jettisoning the canopy was linked up with the face blind firing handle. The low level capabilities of the Mk. 5 seat were successfully demonstrated in August 1957, when Flying Officer Sidney Hughes ejected from a Grumman Cougar at the U.S. Naval Air Test Centre, Patuxent River, before a group of high ranking U.S. Navy Officers. Subsequently, the decision was made to standardise the Martin-Baker Mk. 5 seats for all United States Navy jet fighters and trainers, and many fuselages were sent to the Company’s factory at Denham for trial installations.

 

North American Sabre and Republic Thunderflash aircraft of the Norwegian Air Force were the first of many N.A.T.O. aircraft to be flown into Chalgrove airfield where the installation of Martin-Baker Mk. 5 seats was made, replacing the original American ejection seats fitted in these aircraft, because the Norwegian Air Force preferred Martin-Baker seats. Altogether the Mk. 5 seat has been fitted to nearly twenty types of American aircraft, including such advanced aircraft as the McDonnell Phantom, L.T.V. Crusader, and Grumman Intruder.

Specifications

 

Specifications	Mk 5 (Typical)
Operating ceiling	50000+ ft
Minimum height/speed	Zero/90 KIAS
Crew boarding mass range	70.4 to 101.7 kg
Crew size range	5th to 95th percentile Maximum
Maximum Speed for ejection	600+ KIAS
Parachute type	Irvin I 24
Parachute deployment	Drogue assisted
Drogue parachute type	Duplex drogues 22 in. and 5 ft
Drogue deployment	Drogue gun. Cartidge generated gas. Initiated by
	0.5 sec clockwork time-delay, tripped during
	ejection sequence
Harness type	Combined
Ejection seat operation type	Ejection gun
Ejection gun	80 ft/sec One primary cartridge, two secondary
	cartridges, 72 in. stroke
Ejection initiation	Face screen or seat pan firing
Barostatic time-release unit	Yes, tripped during ejection sequence,
	g-restrictor, time-release unit for man/seat
	separation
Manual override handle	Yes
Guillotine	Yes
Seat adjustment	Up/down, manual operation
Arm restraints	No
Leg restraints	Yes, two garters
Oxygen supply	Bottled oxygen
Personal survival pack	Yes with liferaft
Aircrew services	Personal equipment connector (PEC) provides
	connections for
	- main oxygen
	- emergency oxygen
	- air ventilated suit
	- anti-g suit
	- mic/tel
Canopy jettison	Yes, aircraft variant dependent

How it works

Face screen seat or seat pan firing handle pulled
Canopy jettison initiated
Ejection gun fires, seat moves up guide rails, secondary cartridges fire
Emergency oxygen tripped
Aircrew services disconnect
Leg restraints disconnect
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

High speed
     - g-restrictor prevents operation of time-release mechanism

Below 10000 ft, low speed
     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

Harness and leg lines released from seat
Drogues deploy main parachute, aircrew separates from seat
Normal descent
Manual separation system available if necessary. Operation of manual separation handle
  fires a cartridge that operates a guillotine, severing the parachute attachment line, linkages
  function releasing parachute harness, negative-g strap, PEC and leg restraint cords.
  Freeing parachute from seat. Aircrew can then use rip cord to operate parachute