Two engine failures in one flight, the second one to the ground (airfield)

[Sam Rutherford]

So,
I had an interesting day with a 'new' plane (microlight) - and am trying to figure out what might have happened. Help appreciated.

I'll bullet point the bits I think important...

• Avid Flyer 4, in great condition.
• Jabiru 2200, in great condition.
• Flight across Alps, south to north.
• Average altitude 9000’, maximum 12K.
• 4 hours.

Took off as normal, but only after a weird whistling on the comms – stopped by removing the aircraft power supply and relying on the 9v battery inside.
After 3 hours, engine started running roughly, occasionally. Carb icing suspected but carb heat had no effect.

Suspected choked/choking mags (no leaning option on this one) – so attempted to lean with fuel tap. Fairly difficult – several donkey stops before I found the point on the tap (only 90 degrees between open and closed!) – but again, no real change/improvement.

Problem increasing – so I increased RPM (from 2600 to 3000) and engine ran faster than for a normal cruise but smoothly, EGT etc. all okay.
Then, silence. Long let down to valley floor (doing all the usual things) engine restarted (by itself) at about 500’ agl – I’d have made my field I think… :hmm:

Nearest airfield 10 minutes away (long 10 minutes!), engine running smoothly. Made a very tight circuit  and once on base reduced power – engine cut. Landing made. Tried to start engine immediately, but barely turned over then clicking from starter (typical weak battery noise). Pushed plane to taxiway and apron…

Closer analysis with a multimeter, battery reading 12.1V and once engine started with external power there was no change to this figure with RPM movement. The aircraft has no electrical system indicators.
30 years flying, and I get two engine failures in one flight!

Answers on a postcard?

Fly safe, Sam.

[Planet Basher]

Alternator and/or regulator.

[foxmoth]

Is the ignition run from the electrics or a magneto system? If from electrics it certainly sounds like that could be the problem, otherwise vapour lock?

[3wheels]

Is trying to lean by partially turing off the fuel a normal procedure? I've certainly never heard of it.

What does the Flight Manual recommend in the event of a power loss?

Whilst you may not have a manual mixture control there is presumably some device in the engine that automatically adjusts the mixture and by partially turning off the fuel you have interfered with that systems settings....

[Above The Clouds]

What is fitted, mags or electronic ignition ?

[Small Rodent Driver]

Car type ignition system on the Jab (although there are two of them). Not mags.

Suspect ignition system. Trigger transducers etc.

[foxmoth]

The aircraft has no electrical system indicators.

Sounds a very poor system if the ignition depends on the aircraft electrical supply!

[Capt Kremmen]

What fuel were you using ? Avgas/Mogas ?

[Planet Basher]

The failure of the volage to increase with the increase in revs as indicated by the OP is classic charging system failure.

[gasax]

Some study of the Jabiru manual and this aircraft might be in order. The noise on the intercom is classic alternator regulator failure.
The engine response in the air is strange. The Bing carbs automatically compensate for altitude so using the fuel cock apart from being a non-standard and blunt tool should not be necessary. However you increased the rpm. Above 2800rpm the Jabiru is meant to run rich to ensure it does not over heat. Artificially leaning the mix with your blunt tool compromises that richening and may lead to cylinder head / valve issues - which are far from unknown in the Jabiru. The ignition is direct from the flywheel coils so unless they have got hot (again a known Jabiru problem area, there should be cooling tubes leading to them from the cooling shrouds) there should be no connection to the electrical generation issue, but they are easily tested

[piperboy84]

Glad it all worked out Sam. No idea on the faults but get to the bottom of them all before you have another crack at the Alps, pretty ballsy flying there !!

[Sam Rutherford]

Thanks for the answers so far. I'm particularly interested in the regulator/whistle connection (we thought the problem was the power supply lead to the intercom box - not the actual power supply). So thought problem solved (delayed flight for an hour to do this) before departing...

Understand about the 'blunt tool' leaning method - but was trying everything! Whilst there is a paucity of both instrumentation and controls, it does have 2x EGT and a CHT indicator - so I was happy that all the temps stayed okay throughout.

Will post back once the tech gets his hands on it!

[Sam Rutherford]

Okay, regulator was faulty. At the same time, this doesn't explain the engine cuts as the mags are on a separate circuit from battery and Alternator (which is as it should be).

Best thinking on that is that they choked up after a long period at altitude unleaned, hence the need to add power to keep everything running.

When I cut the throttle to land I was expecting the engine to stop - and it did.

So, I think we have it.

Not that I'm usually flying these sorts of aircraft that high for that long - but some form of leaning would seem a good idea!

Cheers, Sam.

[Genghis the Engineer]

Most of my engine failures have been with that engine model!

I suspect that the failure on closing the throttle is probably down to tickover being set too low - I've seen that a couple of times test flying homebuilts, and it may be unrelated to the other issues.

J2.2s can ice, and there are various carb heat solutions available. Not all of them are brilliant, hence that I've seen several aeroplanes with multiple carb heat systems. I would take a look at that, and see if you're truly satisfied that it's up to the job.

What state were the plugs, before and after?

I'm not sure I've ever seen a mixture control for a Jabiru.

G

[custardpsc]

>Okay, regulator was faulty. At the same time, this doesn't explain the engine cuts as the mags >are on a separate circuit from battery and Alternator (which is as it should be).

no mags according to SRD -

>Car type ignition system on the Jab (although there are two of them). Not mags.

Inoperative regulator = no charge to battery

Electronic ignition fed by a discharging battery wouldn't last forever and would likely misfire before stopping completely. If the battery was rested or got warmer it might recover enough to start/run from a windmilling prop situation.