F-35 Turbine Blade Crack Raises Durability Questions


A .6 in. crack in a third-stage low pressure turbine (LPT) blade of an F-35A last month was the result of “thermal creep,” says USAF Lt. Gen. Christopher Bogdan, F-35 program executive officer.

Though the problem is not thought to be a design flaw in the F135 engine, the Pratt & Whitney propulsion system is “not out of the woods” yet as officials study what implications there could be for durability of the system once it is fielded, he told an audience March 5 at Aviation Week’s Defense Technology & Affordability Requirements conference outside Washington.

The crack was found Feb. 19 during a routine borescope inspection on the ground, but it led to a fleetwide grounding, which was lifted March 1.

The crack was found on a blade in AF-2’s engine. Bogdan says this was the “workhorse engine on the program,” which has been used for envelope expansion work and, thus, exposed to extremes in operation, including flights at 1.5 Mach; in low-level, supersonic conditions and at 7-8G. This aircraft was “doing the majority of the envelope expansion for the A-model fleet,” he says.

Two other aircraft in the conventional-takeoff-and-landing fleet, AF-3 and AF-6 remain grounded because they have been flown in similar – though not quite as rigorous – conditions.

Engine experts will require at least two more weeks to explore what implications there are for engine durability, Bogdan says. “What level of thermal stress would it take to get to that point on a normal airplane,” not exposed to such extremes, he says. “The issue is if it turns out that it is less than 100% of what we expect the life of the engine to be, then we have turbine blade having life limiting parts on it and we’ll have to deal with that.”

Should this become a problem, customers could be required to conduct additional inspections and/or additional maintenance over what was originally planned.

Please or Register to post comments.

What's Ares?

Aviation Week's defense blog

From The Archives

Aviation Week is approaching its 100th anniversary in 2016. In a series of blogs, our editors highlight editorial content from the magazine's long and rich history.


Aug 27, 2015

Aviation Week Lifts Veil On Boeing B-52 Bomber (1952) 20

In 1952, Aviation Week provided the first details on the new Boeing B-52 bomber....More
Aug 14, 2015

Bonanza Travel Pays 3

The legendary Beechcraft Bonanza has an impressive production record, so perhaps the marketers back in 1949 were onto something when they coined the phrase "Bonanza travel pays."...More
Aug 14, 2015

Venerable Boeing 727 Prototype To Fly Again 29

The most famous 727, the prototype aircraft which would join United as N7001U, was delivered to the airline in October 1964 having served its time as a Boeing test aircraft....More
Aug 13, 2015

Aviation Week And The Bomb

Aviation News did not predict how nuclear weapons would change the world. But neither did anyone else....More
Aug 13, 2015

Collins Radar Takes The Ups And Downs Out Of Flying

Turbulence? Rockwell Collins had a solution for those bumpy rides in the early 80s with its WXR-700 Doppler Weather Radar....More
Blog Archive
Penton Corporate

Sponsored Introduction Continue on to (or wait seconds) ×