The Pratt & Whitney F135 engine has returned to Arnold Engineering Development Complex for another round of testing, with a fresh engine component the focus of the latest efforts.

According to the US Air Force, the F135, which powers the F-35 Lightning II aircraft is currently undergoing testing in one of the Sea Level Test Cells at Arnold.

“Since late June, a newly-designed fan rotor installed in the engine has been subjected to endurance and Accelerated Mission Testing. Accelerated Mission Testing, or AMT, is a testing method used to rapidly age an engine, allowing for the identification and correction of issues before they would occur in normal use. Through AMT, a tested engine will accumulate several years of normal life in a short amount of time.”

“The whole purpose of an AMT is to basically put some wear and tear on the engine, if you will, some life, that simulates what it would have out in the field,” said Test Manager Don Corona, now retired.

“But instead of waiting several years to get that, we accomplish that in several months.”

Not only does the AMT consist of testing at ambient air conditions, but it also includes RAM. The term ‘RAM’ refers to the use of test facility compressors to increase the engine inlet pressure and temperature to more closely simulate actual flight conditions.

Corona said RAM simulates high speed travel at a low altitude, allowing engineers to assess how these conditions impact the engine and its components.

“The Sea Level AMT does put wear and tear on the engine that you would see in operation. However, the RAM conditions ensure that we also have data that is representative of flying at high speed at low altitude conditions, which is actually a harsher environment for the engine,” Corona said.

Corona said the test is all about making sure the new fan rotor design checks out before it finds its way into the engine of an F-35.

“This testing will then allow that new design to be disseminated to the fleet,” he said.

“We can’t just take a new design and put it out there on the engines, so this is going to be part of the testing to get it qualified to be put on an engine out in the fleet.”

After testing has concluded, the engine will be disassembled and examined.

“When the engine is done testing, they will tear the engine down and they will examine all the components in what is called an ACI – an Analytical Condition Inspection,” Corona said.

“They will look at all the engine components at that time, and they’ll see if the wear on all the engine parts is consistent with what they would expect.”

The F135 also underwent testing last year to cover pre-AMT objectives. That testing concluded in late 2018, around six months before the AMT involving the newly-designed fan rotor began. Testing of the F135, which is sponsored by the F-35 Joint Program Office, is set to continue into 2020.

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andy reeves

more British ‘bits’ = more jobs, better technical knowledge, good for the economy

james

But Andy there would have been a lot more bits had the RR joint alternative engine the F136 been funded. Another political move by the US DoD to keep the UK technology base suppressed. Its been almost 7 years since the 136 was dumped. It was considered to be more advanced than the F135, but foreign.

Sean

The R136 was 60% General Electric and 40% Rolls Royce (split between RR is Bristol and RR in Indianapolis). So I doubt the DoD stopped funding its development because it had a minority ‘foreign’ component.
More likely it thought it could spend the projected $2 billion to finish development on other things.

Farouk

From what I can gather, the decision to ditch the alternative engine was undertaken by the Obama administration simply to save money. The same mindset was also used to curtain the F22 at just under 200 citing that Russia and China would not have a stealth aircraft flying for a good 20 years and then China revealed to the world , the J20 just 2 years later. Cancellation of that alternative engine is really going to come back and haunt the F35 program.

expat

But the original point of funding a second engine was to create competition and drive down cost. The f136 engine was on the bench the better engine. P&W just better at lobbying than GE and RR imo.

Trevor

Surely it was an absurd notion to offer 2 engines. 2 different huge development costs and if both put in service only half the benefits of efficiency in numbers.
Wasn’t this F136 engine based around thrust vectoring as used in the Boeing plane?

Pompeyblokeinoxford

The F16 provides you with a choice of engines, as does the Merlin. There are more.

Peter Crisp

How good are military jet engines compared with those found in airliners?
There’s a huge amount of work going on to make commercial jet engines more fuel efficient does that get transferred or are they completely different?

Stephen

Very different, the thrust to weight ratios for modern fighter jets is much higher than required for commercial airliners. You could take an engine from business jet and make a passable training aircraft but you couldn’t expect ‘fighter’ performance on a military jet using COTs engines.

expat

Areas like materials there’s a lot of cross over.

DaveyB

Yes and no. A fighter’s jet engine can be either a turbojet or a low by-pass turbofan. I’m ignoring exotic combination, ramjet or rocket engines. A turbojet is where all the air at the face of the engine passes through the core such as the Olympus used on Concorde. A low-bypass turbo fan has a percentage of air at the face of the engine that does not go through the core. The older designs used this as a coolant medium for the outside of the engine and the air was routed directly to the exhaust pipe, which then had fuel… Read more »

Peter Crisp

Thanks for the incredibly informative reply.

JohnH

Thanks. That was an amazing reply.