Special Feature MT 5/2022 · 55 role of the ejection seat was to get the pilot safely out of the aircraft and into the parachute and get them safely back on ground. Ejection seats are not able to sense the weight of the pilot prior to ejection. The seat actually measures the acceleration post ejection and, if it records very high acceleration, then this indicates a low mass present in the seat and accordingly delays parachute deployment. If the seat records very low acceleration, it’s likely that there is a heavier mass present in the seat, hence it speeds up the parachute deployment. Essentially ejection seats measure acceleration to fix the timing of parachute deployment. Seat Safety Speaking on the maintenance of ejection seats, Roberts said that typically an ejection seat can stay for the life of the aircraft, provided inspections and time-bound replacements are strictly adhered to. An ejection seat needs to be removed from the aircraft every three years during which it is tested. Lifed items on these seats include items such as seat harnesses, the escape parachute and leg lines. These items are checked along with other lifed items and replaced, if required, during the periodic inspections done every 3,6 or 10 years. “If our instructions are strictly adhered to, then our ejection can seats can remain on the aircraft for its entire life. This is the case with all of our customers, because they don’t want to buy another seat and all this work is done in-country by our customers.” Roberts added that Russian ejection seats need to be replaced every 10 years, which means that if the aircraft is kept in service for 40 years, then four ejection seats will need to be purchased in that timeframe. To assist customers, Martin-Baker has now moved away from sub- contractors who supply the ISS and has moved this work in-house. The company’s dependence on sub-contractors had resulted in obsolescence-related issues for seat sequencers every five years or so, Roberts said. The Bangladesh Air Force’s (BAF) new Centre of Excellence (CoE) for aircrew safety, which will also carry out MRO work on Mk.10 ejection seats ordered by the BAF, was recently inaugurated and will also undertake MRO of ejection seats to be procured for the BAF’s future acquisitions. Martin-Baker had committed to the establishment of the CoE, when it was awarded a contract by the BAF in 2019 for supply and retrofit of 69 Mk.10 ejection seats for its Chinese-built F-7/FT-7 and K-8W aircraft. The Philippine Air Force (PAF) uses Martin-Baker ejection seats on its trainer aircraft and A-29s, and is also setting up a maintenance facility for their seats, construction of which began recently. the IN fighter tender. Roberts said there was also interest from the Royal Malaysian Air Force to upgrade to Mk18 seats on their F/A-18 Hornets. Martin-Baker has approximately 1,000 seats in service on eight aircraft in service with the Indian Air Force (IAF) and IN. It has received orders for 51 IN16G seats for the Tejas Mk-1 and will also supply 93 IN16G seats for the Tejas Mk-1A. Roberts said the IN16G seat has also been proposed for the upcoming Tejas Mk-2 programme and the Mk18 seat is being offered for the IAF Advanced Medium Combat Aircraft and IN Twin Engine Deck Based Fighter (TEDBF). Safe to Eject A key aspect of the new Mk18 seat is its ability to safely undertake the ejection of a small female or a very large male. This is certainly an important distinction, with the growing number of female fighter pilots in many modern air forces today. Roberts said female pilots bring in specific female physiological requirements. “If you have two pilots that may be twins for the same size and mass, the female is 25%, weaker by structure, as also in respects like bone mineral density, ligament and muscle mass for a comparable male counterpart.” For the purposes of comparison, we can say that a small female would be about 1.5m tall and weigh about 47 kilos nude, about 52 kilos dressed. In comparison a large male would be about 2m tall and weigh up to approximately 120 kg dressed. An ejection seat would need to deliver minimum acceleration for the small female, who weighs less, as compared to delivering maximum velocity for the big male, who is heavier. As a result, according to Roberts, it is important to minimise acceleration and maximise velocity after ejection for the small female, to ensure they are not injured during ejection. This aspect of ejection seat technology is receiving a lot of attention at MartinBaker, Roberts added. Ejection seats are currently not tailored for the weights of individual pilots. In twin-seat aircraft, the ejection seats are fitted with MartinBaker’s Interseat Sequencing System (ISS), which is triggered when the pilot pulls the ejection handle. With the ISS, pilots can choose to delay ejection between the front and the rear or fire the seats independently or operate them in command mode when, regardless of who fires the seat, the rear seat gets ejected first, followed by the front. Following ejection, the in-seat electronics record the acceleration during and after ejection and measure pressure and temperature to obtain altitude data. The seat electronics then select the appropriate time to deploy the parachute. This is called environmental sensing, Roberts said, “the seat goes into the environment, senses what’s out there, how high you are, how fast you are and then selects the parachute deployment times based on the information obtained.” Roberts emphasised that the Atul Chandra is an experienced and widely-published journalist and writer covering Indian and regional issues in aerospace, aviation and defence. Left: The Navy Aircrew Common Ejection Seat NXG (NACES NXG) seat is an update to Martin-Baker’s Mk14 based NACES seat and is being proposed for the F/18 Hornet, Super Hornet and T-45 Goshawk. (Photo: Atul Chandra) Right: The US18E ejection seat has been selected for F-16V FMS programmes and is also being offered on the F-21 for an Indian Air Force requirement. (Photo: Martin-Baker) f
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