The link below leads to a long list of articles posted yesterday explicating various issues. I’ve chosen just one to post separately to give an example......
http://www.defensenews.com/smr/hidden-troubles-f35/
The Hidden Troubles of the F-35
https://www.defensenews.com/air/2019...-environments/
The Marine Corps’ ‘No. 1 priority’ for the F-35 involves a rough landing in hot environments
WASHINGTON — It was a hot day aboard the
amphibious assault ship Essex when a pilot brought his F-35B in for what is known as a “mode four” flight operation, where the jet enters hover mode near a landing spot, slides over to the target area and then
vertically lands onto the ship.
It’s a key part of the F-35B’s short-takeoff-and-vertical-landing capability, known as STOVL. And normally, everything in a “mode four” landing goes smoothly. But on this day, when the pilot triggered the thrust to slow his descent, something went wrong. The engine, working hard on a day that temperatures cracked 90 degrees Fahrenheit while trying to lift a plane that was heavier than most returning to base, wouldn’t generate the needed thrust for a safe, ideal landing.
The pilot got the plane down, but was shaken enough by the situation to write up an incident report that would eventually be marked as “high” concern by the F-35 program office. “May result in unanticipated and uncontrolled sink, leading to hard landing or potential ejection/loss of aircraft, particularly in the presence of HGI [hot gas ingestion],” reads a summary of the issue, which was obtained by Defense News as part of a cache of “for official use only” documents that detail major concerns with the F-35 Joint Strike Fighter.....
The issue seems to stem from two factors: the heat, and the fact that much of the testing for the “mode four” maneuver was done with planes that were lighter, as they weren’t armed with heavy stores of weaponry. Feedback from the Marine Corps highlighted that while the average engine should not see this issue until around 750 flight hours, “several engines are at/near the point of concern,” and that number will continue to grow with the extended use of older planes.........
Winter said engineers have identified an issue in the design of the control software that the pilot uses to generate demand for thrust from the propulsion system.
“There’s no redesign of the engine [necessary]. The engine is doing what the engine is supposed to do,” Winter emphasized, before acknowledging that in addition to the software fix, the program office has worked with Honeywell to change how the company calibrates the throttle valve on the engine. “We’ve identified the software fix for the control system, the calibration fix to the throttle valve and some near-term fleet actions that could be taken for very hot days to ensure that the pilot gets the performance he or she needs on those hot days,” he said.
That software fix will be a rolling target, as the first increment of the software release is due in June, followed by another at the end of this year or early next year. “We’ve given them tighter tolerances to tune them more precisely, so that when it goes on the engine it’s no longer not giving the command the way it’s supposed to be,” Winter explained. “It wasn’t tuned correctly for this high-demand phase of flight. Now, we fixed that. That’s fixed. The software is going in to make sure that the pilot can command that thrust and understand the heat and the loading.”
Those fixes won’t be cheap, and when asked who would pay for them, Winter was blunt, saying it is his office’s belief the thrust issue is a “design deficiency” that merits “consideration” from industry. “In this case it doesn’t matter that the design was done back in 2002, it’s still pragmatistic, so you owe consideration because we’re fixing it right now,” Winter said of industry..........