About the engine issue the JSF is currently experiencing, could this be the
same issues as they had a couple of years ago with the STOVL engine which was also a blade issue?
JSF Nieuws.nl
Long history of engine problems since 2006
It can not be excluded that the root cause of the current problem is more structural than a simple manufacturing error or an isolated incident. Since 2006 there had been a series of engine problems with the F-135 engine.
Already in May 2006, Aviation Week reporter David A. Fulghum wrote 0a detailed article “Joint Strike Fighter F135 Engine Burns Hotter Than Desired” and described the risk of a shorter engine life or engine damage caused by higher than expected temperatures on the F-135 engine.
In August 2007 and February 2008 there were serious problems. Turbine blades broke off suddenly by a form of metal fatigue. The cause was sought in a combination of factors.
On 30 August 2007 in test engine FX634, after 122 hours of testing, a turbine blade in the 3rd LPT stage broke off completely. On 4-February-2008 something similar happened to engine FTE06, also in the 3rd LPT stage, after 19 hours.
These problems with the engine contributed significantly to the delays in the JSF test program for the period 2007-2008.
Redesign of the engine in 2008
In early 2008, an engine, the FX640 ground test engine, was equipped with numerous sensors and instruments. On April 21, 2008 a test process was started to find the cause of the problem. Through a detailed test plan the forces and tensions that arise in the engine were mapped by different power ranges. At that moment it seemed to be primarily an issue of the F-35B STOVL (vertical landing) version. The cracks in the turbine blades were created in exactly the same place, and seemed to occur when switching from forward to vertical drive. Later in 2008, the results became available. The blade crackes seemed to have been caused by certain vibrations that triggered a material failure.
This led to a redesign of a number of elements in the engine. One of the upgrades was a change of the distance between the turbine blades. After the redesign the engine was retested and recertified. At the end of 2008 Pratt & Whitney issued a press statement, that they were convinced that the problems were solved.
In 2009, problems with redesigned engine
In July 2009, the then head of the JSF Program Office, General Heinz was still not happy with the F-135 problems, he said against the press: “The problems include too many individual blades that fail to meet specifications, as well as combined “stack-ups” of blades that fail early. I’m not satisfied with the rates that I’m getting.”
A few days later he was commissioned by the Pentagon not to comment publicly on problems with the F-135 engine.
In September 2009, again serious engine problems revealed during testing of the Pratt & Whitney F-135 engine. At a crucial moment in the debate in the U.S. Congress on the choice of two competing engine types (the Pentagon want to delete the second engine choice (GE / Rolls Royce F-136) a Pratt & Whitney F-135 engine broke. Again the cause seemed to lie in broken turbine blades. However, now the problem occurred in the new engine type with the redesigned turbine blades.
Engine problems continuing until now
After problems in 2009 officials no longer publicly commented about the engine problem. Also there were no indications that there actually were problems with the engine or that there were any reliability issues.
In April 2011, however, Admiral Venlet, the then Head of JSF Program Office, told reporters that some engine problems were impacting on the delivery schedule.
The grounding of last week put the engine back in the spotlight of publicity. However, at this moment it is not the complex F-35B STOVL version, but an engine in an F-35A, the Air Force version.
For Pratt & Whitney, hopefully it is an one-off, and not a structural problem.