GTSIO fuel flow problem

[camlobe]

Hi folks. Need some help.

GTSIO-520-L on a 421.
40 hours since factory. Dumped on my lap. The engine was never set up properly at installation (done elsewhere). Don't you hate trying to correct someone's laziness/incompetence/insert your own reason.

Now have the unmetered fuel flow right at top and bottom. MAP's now match throughout the range. Now have 25 RPM rise on ICO. All seems good.

Problem remaining....

Cannot get the indicated fuel flow up at the bottom end of the range. Doesn't even reach the green arc until around 1500 RPM. Everything matching nicely between the engines once RPM's at or above 1900. Nothing in 97-3C seems to help cure this problem.

I am probably missing something blindly obvious, and will take any constructive critisism/pisstaking on the way to remedying the fault.

Over to you all and thanks in advance.

camlobe

[NutLoose]

Hi folks. Need some help.

GTSIO-520-L on a 421.
40 hours since factory. Dumped on my lap. The engine was never set up properly at installation (done elsewhere). Don't you hate trying to correct someone's laziness/incompetence/insert your own reason.

Now have the unmetered fuel flow right at top and bottom. MAP's now match throughout the range. Now have 25 RPM rise on ICO. All seems good.

Problem remaining....

Cannot get the indicated fuel flow up at the bottom end of the range. Doesn't even reach the green arc until around 1500 RPM. Everything matching nicely between the engines once RPM's at or above 1900. Nothing in 97-3C seems to help cure this problem.

I am probably missing something blindly obvious, and will take any constructive critisism/pisstaking on the way to remedying the fault.

Over to you all and thanks in advance.

camlobe


Will have a think about this see if i can come up with anything, are you aware of this? might be sucking eggs so to speak but
http://www.tcmlink.com/pdf2/SB06-1A.pdf

One thing though,I got a TSIO 520WB new from the factory and that came with short reach plugs instead of the correct long reach items, had all sorts of probs with that, when the second was fitted by another company I heard they to were having issues in flight as it was misfiring to death, they had tried everything under the sun, I contacted them told them to check the plugs and guess what............ yup same thing even after we had informed the factory twice.

[sir.pratt]

try swapping Wf txmitters. maybe the impellor is sticky/tight and doesn't come alive until a decent flow is available.

[camlobe]

NutLoose,
Many thanks for your reply. Factory engine fitted in 2001, hence 06-1A is n/a. Plugs are correct length. We don't have any rough running, just low fuel flow up to 1900 RPM.

sir.pratt
Many thanks for your reply also. This one is steam-driven, equiped with direct reading fuel flow guages, already swapped at the guage. Problem with the engine.

[gaunty]

camlobe
It's gotta be a dodgy fuel pump.
Have you had the fuel pump bench tested and calibrated, they may have transferred the original pump from the timex engine and it is tired or whilst it has been sitting on the bench waiting to go back on the engine its gummed up. Unless the pump is doing its thing and the internal baro and fuel pressure gimcrackery is fully serviceable, you can spend a lifetime chasing it. It's the heart of those engines.

If as you you say the engine was never set up from installation, I would recommend the quickest way would be to bench test the fuel pump, fuel manifold and check the injector sizes for each pot. While you are doing that send the electrical harness to the test bench as well just to be sure. Take everything back to spec set up to the manual then it should be just fine.

[Graybeard]

How about a leaking intake manifold?

[arcs'n'sparcs]

It's been a long time since I've had my hands on one of these, but I seem to remember a similar defect. The guage is direct reading, so is actually measuring fuel pressure, not flow? Also seem to remember that there is MAP(?) connected to the indicator. If MAP is ok across range, problem must lie with pressure. So, if the engine is running ok, actual fuel flow is ok, then the pressure required to provide this flow must be less than maintenance manual specs. With my defect, the injectors were worn and oversize, so the fuel to the engine required less pressure for the same actual flow. I'm hoping you've already fixed the defect, (your post was a while ago) but this may be of some help. Did my head in at the time, was only a young bloke thrown in at the deep end!

[gaunty]

arcs'n'sparcs :ok: I'd say you're pretty close my memory is cranky on it too, and there is an aneroid device in the pump that adjusts the pressure/flow for altitude against commanded MAP. Hence no need to adjust FF on climb/descent. It's quite a complicated fuel pump as pumps go and perhaps only a short step from the turbine FCU.

That fuel pump, accurate injector size and fuel manifold pressure (spring loaded if I recall) are the heart of the engine.

You didn't work for Rex perchance?

[camlobe]

Greybeard, arcs'n'sparcs and gaunty,

Many thanks for your inputs as well. Everything with this low-time engine pointed to a pump problem.
After speaking to a very knowledgable and experienced chap who used to work for a now defunct, highly respected engine shop in Yorkshire (thanks Gerry A*****e) and spending two days fetteling, we now have agreeable results. At last, both port and stbd engines are balanced with all their indications. And the aircraft flies spot on with equal fuel burn. And we haven't had to change the pump.

This was one of those occasions when, after doing the adjustments and following the SB as I had done on many previous occasions, the expected results never materialised, leading to serious self-doubt.

All's well that ends well. Thank you all for your valued inputs. Much appreciated.

camlobe

[arcs'n'sparcs]

No worries camlobe, glad to hear you've solved your problem. :) Was there anything specific in the fix?

gaunty, no I've never worked for Rex though I may be putting my resume in if my eba negotiations go in the direction I think they will! Any jobs?
My problem occurred in Darwin quite a few years ago. I think the worst thing was my inexperience and a bunch of framies that wouldn't admit there was something wrong with their engine - gotta be the gauge!:ugh:

[gaunty]

arcs'n'sparcs

Gotta feeling I know the C421C you are talking about, didn't belong to an Aboriginal mob did it, just cant place the guy who was the boss. I think I came up from Perth to pick it up to sell it for them. VH-DKT??

Wasn't talking bout the current Rex regional operator woz talking about Rex Aviation the Cessna Distributor :ok:

['aveagoodknight]

arcs 'n' sparcs, wasn't WGS or ANH was it? :p

Also seem to remember that a leaking or blocked upper deck line can cause similar issues. I think that UDP is an input into the fuel pump and is also used as an ambient reference for the direct reading fuel flow (read pressure as arcs'n'sparcs pointed out)...

I got quite good at setting up all the pressures with the 'blue box' on the GTSIOs in 404s and 421s in my day. Sadly those memories have given way to MECs, HMUs, EECs, CDU interrogation and seat recline mechanisms.


'ave a good night!

[arcs'n'sparcs]

To be honest guys, can't remember the rego, though it was blue! Yeah, big help there. Owned by Exec Air Charter. And yeah, much nicer nowadays with HMU's/MFCU's/FADEC etc. Still got that big fan up the front though! :rolleyes:

Hope you all had a great Christmas and all the best for the New Year.

Keep those spanners swinging! :ok: