Fuel Injection Icing
 

Hi all - any ideas on what could have caused this?

Flying an IO360 equipped aircraft with fuel injection, up a coastline after an uneventful over land flight. Weather is:

METAR 131820Z 26009KT CAVOK 16/08 Q1013=

1700' QNH, less than 1NM over the water flying parallel with the coast. 90kts, 2200rpm 6gph. Notice a reduction in power, increase throttle - no response. Full throttle gives no improvement. Excercise Alternate Air - SUDDEN LOSS OF ALL POWER! Alt Air to closed, regain 1900-2000rpm. Fuel pump on, change tanks, cycle mags no change. Declare a PAN and limp home. Power gradually improves but is by no means back to full by landing 10mins later. (still 6gph at full throttle)

Aircraft to be inspected by engineers tomorrow. Initial thoughts are icing to the fuel injection system, and if I'd left the alt air on (hindsight - great eh?) it would have cleared it as carb heat would. Doing some research this evening shows that Alt Air helps with impact ice only and that according to GASCO you can't get icing with fuel injection.

Any ideas? (ps still had fuel in both tanks on landing - before anyone asks!)

Some air path or fuel path blockage.

No way to get fuel icing on avgas at about +12C OAT.

Definitely dismantle everything outside the engine and inspect, including all fuel hoses.

The correlation with the alternate air operation may be a good pointer, or may be a redherring.

Blocked injector(s), possibly due to contaminated fuel.

Leaking injector diaphragm.

had the similar on a PA38
 

When I was training, I had a similar problem on a Tomahawk ( normal carb stuff).

Engine was slowly losing power, selected hot air and it went very rough and i thought it was going to stop. Hot air off and power came back. I Put the hot air back on again but bottled out and turned it off after 5 mins and 1000' loss of altitude and limped back to Panshanger.

Problem was an air leak somewhere, though I don't recall where.

Hope it helps

Hi Get your engineers to also check the fuel return lines, and the tank vents, sounds like a fuel flow/blockage or air in system problem.

Will.

It does sound like a fuel restriction of some kind - debris in tank, blocked filter etc.
6 US gall/hr would give no more than about 45% power for a standard parallel valve 8.5 compression IO-360, which at 2200 rpm would normally be at about 19-20" manifold pressure. Full throttle and rich mixture should be around twice that flow rate.
Did the EGT indicate a leaner than normal mixture?
Did you try returning the mixture to fully rich when it happened?
The loss of power given the RPM and fuel flow was probably a lean-cut. I don't know why the alternate air caused a further power loss - possibly it affected the manifold pressure at a given throttle opening.
I would have thought a fuel flow check would give an indication if this was the case.

Might not apply to your engine.

http://www.lycoming.textron.com/supp...pdfs/SB581.pdf

If you are talking about icing in the tank, true. However, carb/throttle body icing is more likely in warm, humid conditions than cold dry ones.

Throttle body icing is VERY unlikely with an injected engine however, we had a problem with our Arrow where the diaphragm in the fuel [ump was breaking up and the debris was blocking the injector.

Had someone put Mogas in [with 5% Ethanol] previously? From your wording it doesn't read as though it was your own machine.

But this isn't consistent with induction icing, is it. You'd expect a marginal decrease in power because of the warmer, richer mixture, unless it's a rich cut (seems unlikely). Had you tested the alternate air before flight?

I remember reading a report in GASIL many years ago about a partial engine failure in a fuel injected helicopter. After investigation it was decided that the impossible happened and it had suffered from induction icing. I'm sorry I can't remember the details but I think it was about 1989.
DO.

Hi there
Throttle(butterfly)icing can occur in injected engines as I once took part in the retrieval of a force-landed aircraft powered by an IO-540, which had made a descent thru cloud, aftre having encountered icing conditions.When the crew popped out of cloud, the throttle wouldn't respond and all they could get was idle power.When the cowlings were pulled off, the remains of ice could be seen in the air intake and the engine was soon able to be started and it ran normally.
I would also go along with the suggestion about checking the fuel manifold, as I have also encountered a loss of power associated with a diaphragm failure in the flow divider on an IO-360.
regards
TDD

This is nothing more than structural icing, possible in any IMC between 0C and roughly -15C.

The argument about fuel system icing in injected engines is whether one can get it due to the gas expansion. I don't think one can.

There would not have been gas expansion triggered cooling in the air intake.

We had a Mooney land at Newcastle last year with suspected induction icing. The pilot had overboosted the engine trying to maintain power. It lost most of its oil through the turbocharger and I believe most of the cylinders needed to be replaced. The conditions were perfect for normal carburetor icing. The Mooney was in VMC. The engine died on the runway.

I think people rule out icing far too quickly. Have people read the articles on clear air ice formation under the anvil of large thunderstorms in turbine engines?

My theory here is that induction icing formed at the butterfly.

BHenderson, I have read articles on flying under the anvil of CBs and from what I have read it is not a good idea... there was an incident with a B757 at Palma a while back (couple of years ago perhaps?) that flew under the anvil of a CB just after takeoff and was damaged by hail.

Smithy

Induction icing is not unheard of in the older M20K turbocharged Mooneys, but the conditions conducive to it are very cold temperatures in visible moisture and the icing forms on the induction air filter. Opening the alternate air system or descending into warmer air restores power. To alleviate the problem, the factory offered replacement automatically opening alternate air systems. The main region the reports of induction icing problems came from were in Northern Canada during the winter. There are no documented reports of induction icing problems in other areas, including those where carburettor icing is much more prevalent (such as IMC).

If the Mooney really was suffering from significant induction icing, the air supply would be being throttled and power output would consequently be low. I can't see how the pilot could then overboost the engine. Of the potential icing problems, it sounds more likely he was suffering airframe and prop icing and needed the extra power to make up for the drag and deformation of the wing and prop aerofoils. Given that conditions were VMC, that would appear not to be the cause. More probably there could have been some blockage in the fuel supply which would have allowed him to run at higher power but with a very lean mixture and high EGTs, but that would have been nothing to do with icing.

I am still going with blocked injector(s).

:confused:

Sorry for the delay in replying, but the engineer's inspection revealed a blocked injector.

I did try fully rich but it gave a further drop in rpm. The Alt Air was tested on the run up before TO and it gave the normal slight drop. The fuel was from a regularly inspected supply, tested during the A check that morning, the aircraft had flown approx 2 hours prior to the incident on the day and the aircraft has been fairly busy over the last few weeks.

Thanks for your responses - I guess it answers the original question about ice!

cheers

SP6

On an IO360, one blocked injector does not account for the symptoms in your first post, sp6.

A single blocked injector would cause rough running, with a lot of vibration, but not what you got.

You may find other stuff elsewhere...

The message about the injector was passed on to me today, I haven't been back to the airfield to talk to the engineer in person. Before I do go back, I'll certainly be reading up on how injection systems work - my old text books just show carburettors.

The engine continued to run smoothly, with the reduced power. and in response to an earlier post, only AVGAS from a certified source is used for that aircraft - no way could it have been MOGAS and no one uses the aircraft for touring so it never leaves its home base.

I'm just glad 2100rpm was enough to keep me flying and enough for a slow climb to give me 2500' qfe when I got to the field. Phew!