WASHINGTON — The Air Force could be ready to remove restrictions on lightweight F-35 pilots as early as April, following fixes to the aircraft's ejection seat and helmet.

But Martin-Baker's US16E ejection seat is not completely in the clear yet. Even if the newly modified pilot-escape system meets requirements, the service may still press ahead with certifying a second ejection seat as a bulwark against potential risks in the future, said Brig. Gen. Scott Pleus, who heads the Air Force's F-35 integration office.

In 2015, the Air Force discovered that F-35 pilots who weigh less than 136 pounds were at high risk of severe or potentially fatal neck injuries upon being ejected from the aircraft. The service then restricted all pilots below that weight from flying the F-35 while Martin-Baker, which produces the US16E ejection seat found in all variants, and Rockwell Collins, which manufactures the helmet, adjusted their products.

Now, testing of the modified escape system is mostly complete, and the F-35 Joint Program Office (JPO) has provided that data to the Air Force Lifecycle Management Center, which functions as the service's airworthiness authority, Pleus told Defense News during a Feb. 10 interview.
 
One last test remains, an "electro-environmental" demonstration scheduled for March that validates that the escape system fires only when triggered. After reviewing the data, Air Force engineers and airworthiness experts will produce a final report, he said.

"Assuming that the seat meets the specification requirements and has the capability of providing safe ejection parameters for our 103 pound pilot to our 245 pound pilot, once the Air Force has certified that the seat is cleared for that range of operations, we will remove the weight restriction currently in place," Pleus said.

"We anticipate that by April, we should have a response from our airworthiness authority," a role performed by Lt. Gen. John Thompson, Air Force Life Cycle Management Center commander. "If that were to be the case, there would be a series of retrofits that would be required for the seats. That would probably take a few months, and at that point, we would have a capability of opening the pipeline to lightweight student pilots."

Martin-Baker and Rockwell Collins have made three major changes to their products in order to make the escape system safe for lightweight pilots.

A new switch in the US16E ejection seat alters the parachute loads to accommodate pilots of different weight ranges, and a head support panel helps protect the head and neck from stress upon ejection. The weight of the Rockwell Collins helmet has also dropped from 5.1 to 4.6 pounds.

Some Air Force leaders have been skeptical of the fixes to the pilot escape system and have advocated looking into a second ejection seat. Last summer, Lt. Gen. Arnold Bunch, its top uniformed acquisition official, requested that the JPO study how qualifying United Technologies’ ACES 5 model would affect the F-35 program’s cost and schedule.

That report is due in March and will help to inform the final decision on whether to lift weight restrictions, Pleus said. But even if restrictions are lifted, the service may decide to qualify ACES 5 nonetheless.

Given the number of F-35s planned to be purchased by the Air Force — 1,763 in total — Pleus believes that there would be value to qualifying a second seat, in case further problems with the US16E surface later down the road. But service leaders will have to weigh that against the UT ejection seat’s cost and capability, he added.

"If at some point if an issue arises with the Martin-Baker seat, or from a cost effectiveness or safety standpoint, we would make a decision over which was the better seat," he said. "Right now, we have no data about the ACES 5 seat. Is it safer? It might not be. Is it more expensive or cheaper? I don’t know that."

Retrofitting the Pilot Escape System

Once flight restrictions on lightweight pilots are lifted, Martin-Baker engineers will begin retrofitting US16E ejection seats in the Air Force’s F-35A fleet, starting with aircraft at the training bases, JPO and company officials told Defense News last year.

If the Air Force gives the green light to lift F-35 weight restrictions this spring, the service anticipates that the first retrofits would wrap up as early as this fall.

The JPO had hoped that the service would be able to remove flight restrictions on lightweight pilots by the end of last year, but it took longer than anticipated for the companies and program office to synthesize test data. In September, officials said the program office and Lockheed Martin had already put together a preliminary retrofit strategy and had ordered the parts needed to begin modifying the seats.

It will take about two years for all of the F-35s to move through the pipeline, JPO officials said then.