Ground Run after Engine Changes
 

Just wondering, how long are post maintenance engine runs these days. I remember hours of high power engine runs on Tristars years ago but would hope that things are smarter with 737NG, A320 and all the other spangly new jets.

Does anyone have a clue about how much running is required after an engine change?

Thanks

The RAT!

Some engines, {operators expense} come already to just be fitted an idle run. They run them on the test bed and all we have to do is fit the engine and like i say, idle for leak checks and some functions like Generator disconnect and then its ready to go

cessna24

PW 4000 series on the B777 - bolt it up, fire it up, if it don't leak at idle, sign it and send it - just like Cessna 24 said.

If the RB211 was test bed run and serviceable, even back in the 70s it only needed a leak check and GI/FI and gen disconnect.
But where I worked, the engines were not test bed run (we didn't have one), so we did Test 1 to 17 incl. With no problems we could do it in 45mins. It was Test 4 and 5 that took the time as you were bedding in the abradable liners! But then we got lots of practice! 13 Tristars, HPT blade hard life 1200cycles.

13 Tristars would be the worlds biggest fleet now! Guess today it must be the RAF with what, 8 or 9.

Rat

1-Does the test bed mean test cell?

I am wondering about the 17 tests and hours on high power engine run stated by Hangar_RAT (or 45 minutes as stated by Swedish Steve)?
The engine that you want to install on aircraft is supposed to be good: I assume (I might be wrong?) this engine was overhauled or repaired and tested in test cell in engines shop especially if internal items of engine were replaced. Either the engine is overhauled/repaired or new, it will require only few tests (leak test, gen disconnect,...) and not hours of high power engine run. May be you are using engine aircraft run as a substitute to engine test cell?
I hope I can get some clarifications regarding this subject: I guess I am missing or mis-understanding something especially when it come to engines shop work and Hangar or line work.

2-When you are performing high power engine run on engine (mounted on wing) do you run the opposite engine?

3-Steve, what do you mean by GI/FI?

Feedback appreciated.
Thank you.

In a few words. The engine is fitted to the aircraft by us engineers and once all connected to the aircraft itself, we ground run the engine. This involves starting the engine and ensuring it meets all the correct figures. If it meets the correct figures, we sign up and let the drivers take it away somewhere far away!! If by chance it fails to meet these figures, then its back to the hangar for adjustments. This job is usually a hangar job but us lineys sometimes have to chip in. I recently changed a UPS B767 engine. Good fun.

When running high power checks, yes, you do run the other engine but usually at idle. But please someone correct me if diff for some a/c. And we have to sit on the brakes to stop her rolling forward.

Cessna24

4-engine types, symetrical pair, and usually both near high power.

TriStar.
The last two engine changes I've seen were 8 hour affairs to install, ground run for leak check, and one (only) high power run.

Test bed = test cell

FI = Flight idle

GI = Ground idle

If the new engine's fuel system had been preserved (normally the case) then wet motoring (ignition off) is in order until fuel vapor is seen in the core exhaust.

Of course instrument validity is checked too.

747 outboard engine above 1.3 epr opposite engine to 1.3 (for RR/PW, GE equivalent N1) for balancing, no higher even if you take engine being tested to 1.6 epr. Inboard engines do not require balancing, this is to reduce torsional loads on wings and landing gear.

The RB211 is a modular engine. There are 7 modules including the fan case. When the engine is taken into the shop a decision is made of which modules to overhaul. In the early days (I am talking 1977) the HP Turbine had a very limited life. So every 1100 or so cycles the engine was removed to the shop. If there was no other problem, the shop could replace the HP (04) module in a couple of days. We then sent the removed 04 module off for overhaul, and put the repaired engine onto the next aircraft that needed one. This engine then needed a test bed acceptance run. In the RR MM are a list of tests numbered 1 to 17. The manual tells you which test to do depending on what has been changed on the engine. Test 1 was oil circulation and fuel drains, test 17 was Thrust reverser function. The important tests were test 4 and 5 which were running in the engine, and checking performance. We then converted all the figures back to ISA and calculated the engine performance. On the RB211-22B it was sometimes marginal on installation!
If you did these tests in order it could take some time, but having a lot of practice I could easily do the lot under the hour. My personal record was a Nbr 3 engine. Aircraft came in the hangar at 1400, on the run bay at 1820, and on the ramp at 2000 for a 2130 departure. But we were waiting for it, and the new engine was a good one. The Nbr 2 engine took a lot longer!

Coincidental question here - if you swapped out both engines out (PW 4000) would a flight test also be required.

It would be normally up to an individual airline on the test flight, do not think it is a requirement.
However for ETOPS you would normally require a flight lasting 1 hour to validate ETOPS requirements, could be the first hour of an ETOPS flight before being cleared to continue.
Please correct me if l am wrong.

No, except for aircraft with manual controls, like all B737s, flight tests are the exception after maintenance. ETOPS rules may interfere, but except for the odd exceptional situation, we only carry out flight tests after elevator and aileron work on the B737.