Powerful problems

Yes engine development is complex. Especially when considering the tri-service F-35 requirements.

One would think that the project managers and other big-brains will get out of the current F-35 grounding which revolves around cracked turbine blades.

Let us review some F-35 engine history. Below is a 2008 briefing that deals with earlier engine failures. One comment in the brief shows that Pratt and Whitney knowledge came up short.



---"P&W had neither the standard work nor the advanced analytical techniques to address this phenomenon
–Exceeds current industry state-of-the-art"---

Now on to other F-35 engine problem history here and here.

Graham Warwick AW; 14-sep-2009

The CTOL engine was 2,455 cycles into a 2,600-cycle durability test leading to initial service release when "parts were noticed coming out of the jet pipe". The engine was still running and capable of producing thrust when it was shut down.

Inspection revealed tip damage to a "handful" of blades on the first and section fan stages, which are integrally bladed rotors (IBR). Downstream damage was confined to the compressor. There was no visible damage to the combustor and turbine.

The F135 was 5 hours into an 11-hour supersonic high-cycle fatigue test and was being pushed very hard through a sequence of throttle transients. For this test, the inlet-plenum hardware on the test stand had been changed to run at supersonic conditions. There is something at the bottom of the engine [between the fan and compressor] that we want to retrieve".

And 27-sep-2011

Only a couple of days after the termination of the FY2011 budget in the F136 engine development contract new problems are reported by Stephen Trimble of Flight International in the competitive F135 engine program.

Some quotes from the article "New engine snag upsets F-35 manufacturing progress":

Pratt & Whitney confirms that a "small number" of F135 test and production engines have been replaced with spares since March. The replacements were ordered after a ground test engine was found to be mis-assembled after an overhaul, Pratt & Whitney says. Further checks identified the same problem on other test and production engines.

"These engines are being replaced by spare engines on site in Fort Worth, with no impact to the F-35 flight test programme," the company says.
However, Venlet says the engine problem has caused a short-term interruption to the new manufacturing plan.

Venlet's predecessor, Brig Gen David Heinz, also complained about quality control issues on the F135 engine, telling reporters in July 2009 that although individual turbine stages met quality specifications, the combined stack of stages in a completed engine did not meet tolerances for quality.

It is unfortunate that lobbying and back-room deals got rid of the alternate F-35 engine by GE/Rolls known as the F-136. This was a big sell in the early justification to Congress (and to all partner nations) posing as "value-added", that two engine vendors would inject healthy competition into the program.

GE/Rolls was with the program, became a stalking horse, and then, kicked out to cover F-35 Nunn-McCurdy cost rise in other parts of the program. Note that they still get some work with STOVL appliances that go with the Pratt and Whitney engine.