Three years and eight failed tests later, the U.S. Navy successfully executed an arrested landing of its F-35 variant fifth-generation fighter this week on the oldest active aircraft carrier in the U.S. fleet.
On Monday, a Lockheed Martin F-35C Lighting II Joint Strike Fighter piloted by Navy test pilot Cmdr. Tony
Wilson successfully landed on the flight deck of the
U.S.S. Nimitz, marking the fighter’s first successful arrested landing — when a
jet is brought to a stop by a tailhook attached to the rear of the aircraft,
which snags a wire stretched across a carrier’s deck.
This week’s first successful landing comes about three
years after the Navy’s F-35 variant failed eight arrested landing attempts as a
result of arresting hook design issues. According to The Aviationist, the distance between the
aircraft’s initial tailhook placement and the rear landing wheels was too
short, resulting in the arresting cable laying nearly flat on the flight deck
by the time the tailhook was in position to intercept it.
Late last week the Pentagon announced the findings of an
investigation into an F-35 engine fire earlier this year, which resulted in the
third across-the-board grounding of the fleet since the Joint Strike Fighters
began undergoing flight tests.
“The engine failure and subsequent fire were the result
of micro fractures in one of the three-stage fan sections that compress air
before it enters the engine,” the Department of Defense announced in a press
release last Friday. “These sections are lined with a polyimide material that
is designed to rub against the fan blades to reduce pressure loss.”
In the case of the F-35 in question, the third fan was
rubbed “in excess of tolerance” while executing maneuvers weeks before the
failure, heating the blades to 1,900 degrees, or 900 more than expected. The
rubbing caused fractures in the titanium component of the rotor, which grew
over the weeks before the June runway fire.
“That caused that rotor to liberate from the
airplane,” Air Force Lt. Gen. Christopher C. Bogdan said. ”The fire
was caused not by the engine, but by the pieces of the engine that flew out
through the aft upper fuselage fuel tank.”
The Pentagon announced two short-term fixes for the
problem, including a “burn-in” process that includes flying the aircraft in a
specific way in order to break-in the engine ”such that where this rubbing
occurs has now been burned in, so to speak, and anything else you do with the
airplane inside the envelope won’t cause any more rubbing than what it has
already seen,” Bogdan said.
In the second fix, engineers “pre-trench” the stator
walls, so that ”[w]hen we put the fan blade in there, no matter what we do
on the airplane G-wise, speed-wise, altitude-wise, it won’t rub anymore,”
Bogdan explained.
The general said it will take months to execute fixes on
all fielded F-35s, and engine producer Pratt & Whitney has proposed several
long-term fixes for future engine production.
No comments:
Post a Comment