By Tommy H. Thomason

Sunday, February 6, 2011

Transition to Martin-Baker Ejection Seats

Early on, even before there were ejection seats in jets, the U.S. Navy established a relationship with Martin-Baker, a company located in England and dedicated to the development of the ejection seat. Two of its officers went there in 1945 to witness ejection seat testing. Although the Navy continued to rely on its airframe contractors to supply ejection seats when required, its specifications favored the Martin-Baker design philosophy of face-curtain activation of the seat.While it didn't buy Martin-Baker seats for various reasons at the time, it did purchase a trainer/test rig from M-B and required their airplane contractors to furnish seats that were fired with the M-B type face curtain (the Air Force used triggers located on the seat's arm rests).
The man in the fedora is James Martin, later knighted as Sir James, visiting the Philadelphia Navy Yard in August 1946 where the Martin-Baker test rig had been installed.

The early ejection seats were simply bailout assists. Even after features like automatic seat separation were added, a survivable ejection had to be initiated at least 500 feet above the ground, much more if the airplane had a high sink rate. Ejection during takeoff or final approach was not an option.

Martin-Baker was dedicated to improving the seat capability and in the mid-fifties succeeded in qualifying a seat system that resulted from a survivable ejection on the runway at speeds above 100 knots. In 1956, BuAer contracted with Grumman to install the new Mk4 M-B seat in an F9F-8T for a demonstration. Flying Officer Sidney Hughes, RAF, successfully ejected from it at Patuxent River in August 1957 while on the runway at 120 kts.


This successful demonstration resulted in a Navy contract with Martin-Baker for the Mk5 seat, which was a strengthened version of the Mk 4 from a crashworthiness standpoint. (An actuator loop was also added at the front of the seat pan to expedite ejection if required, such as an emergency during catapult launch, or when g-levels made reaching the face-curtain loops difficult.) Most in-service Navy fighters with ejection seats were changed over to the new seat, either in production or as a retrofit. It took a few years because each installation had to be developed and certified by Martin-Baker. The seats were somewhat tailored to each aircraft type, with specific identifiers in some cases, e.g. H5 for the F4H, F5 for the F8U, and P5 for the F4D (shown here).



The changeover appears to have begun with the single and two-seat F9F Cougars in the training command.  The first F9F-8T ejection on Martin-Baker seats was in September 1958. The first Cougar ejection was in November.

Martin-baker seats were installed in F3H BuNos 146709-146740 at the factory. The first ejections using a Martin-Baker seat from the F3H reportedly occurred in March 1958 with the last in a McDonnell seat in November 1960.

The F-4 Phantom first flew with a McDonnell seat but it was quickly supplanted by the M-B Mk 5 seat in production, probably in 1960 with the second block of production airplanes. (For more detail on the change to Martin-Baker seats in general and the F4H in particular, see http://phantomphacts.blogspot.fr/2013/10/f4h-phantom-ii-ejection-seat-history.html.)

Vought was reluctant to admit that the M-B seat was better than its own (although they did install a M-B seat in the third F8U-3 which flew in late 1958). Its seat was a modification of the Douglas Escapac seat which also provided survivable ejection on takeoff and approach. However resistance was futile. M-B Mk-F5s were installed in F8U-2s toward the end of their production run and retrofitted to surviving F8Us.  (Contrary to some reports, a cockpit console width change was not required, only different rails and catapult fittings plus stiffening of the bulkhead.)

LTjg John T. Kryway cut it a bit fine with the M-B seat but survived after his hard landing on FDR in October 1961 necessitated jettisoning his F8U-1:



The North American FJ-4s appear to have begun to be switched over in early 1961 at the first or second major overhaul after late 1960. The first reported ejection using the Martin-Baker seat was in September 1961. If you don't have a photo of the specific aircraft being modeled, the best bet is the original seat. The earliest example that I found of a MB seat in the FJ-4 is VA-144's 3rd deployment, November 1961 to May 1962. However, there is a picture of a reserve FJ-4B dated July 1963 with the original seat.

No M-B seats appear to have been installed in F4Ds during production at Douglas, but most survivors were eventually converted to the Mk-P5 during an overhaul.

One notable exception to the changeout to M-Bs was the F11F Tiger. A quantity of 201 seats was procured for the Tigers but they were not installed, with the exception of two F11Fs subsequently pulled out of long-term storage for an in-flight thrust reverser program.

Martin-Baker demonstrated its zero-zero seat in 1961, with the Navy procuring it in 1965 as the Mk7. The performance increase was accomplished by the addition of a rocket.

The Mk5 and Mk7 seats are easily differentiated by the parachute housing. On the Mk5, the parachute was enclosed in a horseshoe-shaped fabric casing that was housed in a black-painted metal shell on the upper seat back. (See the F4D P5 picture above.) On the Mk7, the parachute was enclosed in a green composite horseshoe-shaped shell mounted on the upper seat back.


The changeover to the Mk 7 seat in U.S. Navy fighters began in late 1967 or early 1968 with Mk 5 seats being modified to the Mk 7 configuration. The first F-4Js were produced with Mk 5 seats (deliveries with Mk7s reportedly began in December 1967) and then retrofitted, as were F-4Bs; the changeover was reportedly complete by 1970. (The last RF-4Bs were reportedly delivered with the Mk 7.) The F-8J conversions from F-8Es included the installation of the F7 seat. The Hs (rebuilt F-8Ds) after mid 1968, and all Ks (rebuilt F-8Cs) and Ls (rebuilt F-8Bs) models were also delivered with the F7 seat.

1 comment:

Bill Abbott said...

Hi Tommy,
I built the Hasegawa 1/72 F11F-1 Tiger and converted the seat to represent a Martin Baker Mk 5... After it was glued together it became obvious (from lack of reference photos showing same) that the Mk 5 seats were never used in the Fleet, training or Blue Angels' Tigers.
In his Detail and Scale book on the F-8, Bert Kinsey repeats the story of the F-8 cockpit interior having to be widened to accommodate the Martin Baker seat. You seem to have an edge in credibility and I'll take your version until something better comes along.

Kinsey also includes a grumpy remark to the effect that Vought's own seat was only a year from having a rocket engine (and presumably zero altitude capability) when the MB retrofit was ordered. Vice the MB seat which didn't become rocket boosted until some years later. Did Vought really beat MB to having a rocket boosted seat, and zero altitude / low (or zero) speed capability? It doesn't seem like a spare-time activity that an airframe company would lead in... as none of them ever led before, or since. Vought might have had a rocket, sorting out zero-zero would seem to be more than just pyrotechnics.

I deeply appreciate your diagnostic for Mk 5 vs Mk 7 seats - Mk 5 having the black metal shell around the parachute container, Mk 7 having the bare, green, reinforced plastic container. The Mk 7 came in so many different flavors and airplane references do a lousy job of distinguishing Mk 5 from Mk 7 or explaining visual differences. Many thanks. Now I'm figuring out which camo-greens to use for seat cushions, which for parachute containers and which for the cloth top of the parachute containter...

Cheers!
Bill