206 Engine Question

[Phil Croucher]

Hi guys -

 

Got a jetbox that has to be set at 65% for idling because it has a tendency to surge, particularly on winding up the throttle. It also runs quite hot. It does not surge at all in flight operations. This is a quite elusive problem and we would welcome some ideas from the panel

 

cheers

 

Phil

[amodao]

First thing is to lower the idle Max 64%.

Look for cracks in the burner can. (Inside of elbow especially.)

 

Snoop all of the lines for leaks/cracks.

 

Sounds like the Gas producer fuel control bypass valve is not operating freely.

Pull the FCU fuel filter and inspect and clean it.

Bendix FCU Filter

Cleaning procedure for the Bendix para 4.A, 73-20-02 RR C20 MM

CECO FCU Filter

Cleaning procedure in para 4.A, 73-20-04 RR C20 MM

 

The hot running issue:

Have you cleaned and inspected the Fuel Nozzle?

Is the new part number 23077068 Fuel Nozzle installed?

 

If you already did your fuel nozzle pull the burner can and have a good look at the liner and nozzle shield and nozzle.

[beltdrive]

Albert what you doing on a jetbox???? lol...hey my eng.....let me refrase that before he kicks my *^)_%......the engeneer I work with seconds...Amodao.....

so what u been doing these days..?? :up: My 2 cents park it find out first......

[leadingedge]

Allison and Bell says 63%, not 64,65,62, or 61, 63% final answer.

 

I will concur with the trouble shooting as indicated by my estemed coleage as listed above.

[sharkbait]

A simplistic thought ( of which I have many ) - Bleed Valve?

[DGP]

I would say sharkbait hit the nail right on...seen many a bad bleed valve....get someone to watch the bleed valve while at idle...and yes 63 is the idle speed...if the valve is fluctuating without moving the throttle you should have found your problem. You can also try closing the valve with the engine not running to see if it is closing properly...should move fairly easily and smoothly...not hard to move and sticking...addios amigos.... :

[leadingedge]

DG the bleed valve thing is good, but what makes me curious is the fact he says it happens during throttle up. Could it be the throttle rigging or fuel control maybe?

[DGP]

####...I have seen fcu set at the wrong flow rate for type....this usually will show up when someone complains about the aircraft being a poor performer or a real powerhouse...usually a complaint about fuel consumption would be reason to check the flow rate...good place to start and easier than changing parts. As for the thottle up guestion...going thottle up is done slowly ...throttle down is done quickly...you are going to notice things better on the way up than when you rap the throttle to idle....bleed valve is closing with throttle up and happens slower....going to idle rapidly opens the bleed valve...going slowly down is not good as bleed valve will hunt and could cause a compresser stall.Improper rigging will not show up as a hot running engine and I would say would not cause engine surge but checking the rigging is the first step in trouble shooting the problem and the easiest.I had a jetbox with a ceco fuel system doing strange things one time...idle speed would change on its own...flamed out going to idle...surging N1...we changed the fcu twice seemed to cure the problem...til the engine deceled and hard landed....pilot tried to restart a/c on the ground...lets not ask why....thats another story and time...turns out the engine driven fuel pump was going south which caused the high pressure fuel filter to bypass...which contaminated the fcu and governor...sometimes things are not that easy to cure and the more input the better....

[leadingedge]

Do we have a report on the bleed valve issue yet? I will go along with MS, it sounds like a FCU to me, but I have been wrong before.

 

Oh what stories I could tell...........

[frenchwrench]

We had one at NMH that surged and it turned out to be the bleed valve's dirty stem,we found it out after the pilot put heat on stealing some of the air.we sprayed some cleaner on the stem as we moved up and down.. High idle could be the 30 degree setting a bit high,preventing the adjust screw from **** from working.