The F-35 program office is working on a variety of fixes for ejection seat issues that caused the Air Force to impose weight restrictions, but it may take a year until pilots weighing less than 136 pounds are cleared to fly the Lockheed Martin [LMT] jet, the program executive officer said on Wednesday during testimony to the House Armed Services Committee.

The first two operational F-35A Lightning II aircraft arrive at Hill Air Force Base, Utah, Sept. 2, 2015. Photo: Air Force
The first two operational F-35A Lightning II aircraft arrive at Hill Air Force Base, Utah, Sept. 2, 2015. Photo: Air Force

The Air Force in mid-October announced that it had restricted pilots weighing less than 136 pounds from piloting the F-35 due to safety concerns about the Martin-Baker US16E ejection seat—a move that has sidelined one pilot. The requirement is for the seat to accommodate pilots weighing between 103 and 245 pounds.

Air Force Lt. Gen. Christopher Bogdan, who heads the F-35 joint program office, said that an Aug. 27 ejection seat test conducted with a mannequin showed a one in 50,000 risk of neck injury for lightweight pilots flying at slow speeds.

“That was too much of a risk for the airworthiness authorities,” he said.

The military plans on making three changes to the ejection seat and to the F-35’s technically advanced but heavyweight helmet, which has been found to contribute to neck injury during the catapult and wind blast phases of ejection, Bogdan said.

“If pilot has the helmet on…and that helmet weighs more than 4.8 pounds, then the neck loads for that lightweight pilot  by a very little bit exceeds what we would consider to be perfectly safe,” he said. The service wants to decrease the 5.4 pound weight helmet weight by six ounces, and has been working to do that for about six months.

“It will take about another year for us to finish that and ensure that every helmet is less than 4.8 pounds.”

Another issue occurs during the “opening shock phase” of ejection, when parachute on the back of the seat releases, he said. The program office found if it delays the parachute coming out for a fraction of a second, that allows the seat to decelerate so the force on the pilot’s neck isn’t as severe. It plans to begin putting a switch on the side of the ejection seat that a pilot can set for a heavy or lightweight pilot.

It also plans to install a head support panel between the parachute risers to keep the pilot’s head from jerking back too far.

“The government is not paying a penny” for development and manufacturing costs involved with resolving these issues, Bogdan said. “The supply chain from Lockheed through BAE Systems though Martin-Baker will bear the cost of fixing this, as they should.”

In an Air Force news release, the service also noted increased risk for pilots between 136 and 165 pounds.

“That elevated risk is so small that it’s something that we’re willing to accept,” Bogdan told reporters after the hearing. Those pilots have a one in 200,000 chance of neck injury, but that figure takes into account all flights, not just flights where the pilot has to eject.

In the event of an ejection, the probability of injury climbs to 23 percent for pilots in that weight range, but the probability of a pilot having to do that is just one in 200,000, he said. “That one in 200,000 is no different than the risk that we see in legacy airplanes today.”