U.S. Air Force has restricted pilots weighing less than 136 pounds from flying the F-35A Lightning II stealth fighter following safety c...
U.S. Air Force has restricted pilots weighing less than 136 pounds from flying the F-35A Lightning II stealth fighter following safety concerns about the ejection seat.
Recent tests by the ejection seat maker Martin-Baker, has found the US16E ejection seat could cause an unacceptable risk of neck injury during parachute deployment/opening for lighter-weight pilots at low-speed conditions.
The requirement is for the seat to be certified for any pilot weighing between 103 and 245 pounds. An unacceptable level of risk was discovered for pilots weighing less than 136 pounds (61.7 kg).
Air Force leaders decided that as an interim solution, no pilot less than 136 pounds will be allowed to fly the aircraft until the problem is resolved. As a result, one pilot was impacted.
There is also an elevated level of risk for pilots between 136 and 165 pounds. While the probability of an ejection in this slow speed regime remains very low, estimated at one in 100,000 flight hours, the risk of a critical injury in that circumstance is currently higher than legacy fighter ejection seats.
The reason there is an increased risk only for lightweight pilots is because these pilots are assumed to have lower neck strength than heavier pilots and therefore are unable to sustain higher neck loads we are seeing during ejection.
The problem is compounded by the introduction of new third generation VSI helmet mounted display, which is heavy and add strain to pilots.
The three improvements have been proposed for protection of lightweight pilots:
- A reduced weight helmet that weighs 6 ounces less than the current helmet that will reduce neck loads during catapult and wind blast phases;
- A pilot weight switch on the ejection seat that reduces the opening shock of the parachute by slightly delaying the parachutes opening for lightweight pilots;
- A head support that will be sewn into the parachute risers that will reduce the rearward head movement of the pilot when the main chute of the ejection seat opens reducing the pilots neck loads.
USAF has accepted risk of similar magnitude in previous ejection seats. Based on the remote probability of an event occurring requiring ejection from the aircraft and pilot weight considerations, the airworthiness authorities recommended and the Air Force has accepted continuation of flight for pilots falling within the 136 to 165 pound range.
“We expect the manufacturer to find and implement a solution,” said Secretary of the Air Force Deborah Lee James. “We must ensure the ejection seat is tested to meet our specifications and weight requirements. We are going to ensure this gets done right.”
The F-35 Joint Program Office is working in concert with the contractors to explore possible options to fix the ejection seat issue, which is expected in 2016.
F-35 is slated to achieve initial operational clearance and join the USAF in 2016. U.S. Marine Corps has already opertaionalised the aircraft in July 2015.
