Strange Rotax 582 "kick"

[Zibi]

I've noticed that my 582 every now and then will do a kind of a stronger shake as if someone would give the airframe a kick.

 

When it happens it will be a single event like that every couple minutes or so (it doesn't start shaking all the time, just one kick, and back to normal).

 

It seems to happen more on cloudy days or when flying relatively close to clouds (on most days it doesn't happen at all).

 

When it happens all engine parameters stay normal.

 

Does anyone have any suggestions what that could be?

 

 

[Doug Evans]

When was the last time ya changed ya spark plug mine used to do some thing like this went the plug start to miss fire

 

 

[flyerme]

you sure its the engine? could just be turbulence?

 

 

[facthunter]

Could just be a harmonic or the "phasing" of the prop with some part of the aircraft structure aerodynamically. Nev

 

 

[pylon500]

I think I had the same a while back.

 

My inverted 582 would be cruising nicely at around 5700~5800 when a noticeable 'bang' would come through the airframe, and then nothing would happen for a while.

 

Temps would be nominal at around 1100f° but I found if I opened up a bit, bringing the temps down a bit, it would go away.

 

This created problems sometimes in that I would start to exceed my rough air speed, and would end up climbing, sometimes 'quite' high.

 

This problem mostly showed up when flying back from Narromine, using 100ll avgas.

 

I once landed at Bathurst after a series of these events and found the plugs badly fouled.

 

Never fully determined the problem and about 40 hours later through inadvertent throttle management, the engine blew up.

 

 

Was a non oil injected grey head.

 

 

[Guest nunans]

My 503 would do this fairly readily with the standard jetting. (i take off at 3200') It was just running rich and four stroking periodically. I changed out to some slightly leaner jets and it stopped kicking, also my egt's were low on the standard jets and when i changed them the egt's came up a bit though they're still under 1100 all the time..

 

Also when I was running standard jets with the engine "kicking" the rear plugs would come out full to the top with oil on both cylinders (50:1 premix, inverted 503DCDI tail wheel)

 

Now on the leaner jets they come out brown,

 

 

[Guest Andys@coffs]

bit of carb ice that breaks off and ingested......

 

On my trike when occasionally this happened in ADL I could generally land and see a build up of condensate on the carb bodies...if there's condensate on the outside when you land you can very suspicious of ice on the inside when your flying......but in any event use one of the ice charts and a thermometer to determine the likelihood of occurence.......

 

Andy

 

 

[pudestcon]

Could just be a harmonic or the "phasing" of the prop with some part of the aircraft structure aerodynamically. Nev

I think you are on to it Nev. Or could it be a slightly out of balance prop?

 

Pud

 

 

[Guest nunans]

if it gives one kick every few minutes and only in some weather conditions how is it a harmonic or prop inbalance?

 

surely a prop balance or phasing issue would be more frequent or if it was only happening every few minutes then it would last longer than a "kick"

 

but i could be wrong

 

 

[Zibi]

I think you are on to it Nev. Or could it be a slightly out of balance prop?Pud

That's definitely not it, most of the time (as in most whole flights) the engine works completely fine.

I'm sure the kick comes from the engine / prop, as it's a trike and I don't feel anything through the control frame, more like a kick from the back.

 

It's also not a spark plug problem, as it happened on the previous set and then on a brand new one replaced just 2 weeks ago.

 

I think nunans may be onto something, as my EGTs are also a bit low (usually about 550 C range).

 

 

[turboplanner]

Difficulty is what you call a "kick", others might call a "miss"

 

I would check or replace your ignition switch and carefully check, or replace the wiring in case wiring is grounding with air buffeting etc and temporarily cutting spark to the plug.

 

Andy's thought also sounds reasonable - if you are not careful with temperature management (carb heat if fitted) the problem is a massive combustion chamber expansion with the temperature change from ice to liquid to gas to 1000 deg gas

 

 

[Sapphire]

Zibi said: It seems to happen more on cloudy days or when flying relatively close to clouds (on most days it doesn't happen

 

Icing? I got that on a Continental and cadby heat solved it.

 

 

[facthunter]

People think that two strokes won't ice up . Having the carb close to the cylinder and the fact that some of the gas going in comes back again helps it not to, but there is still the possibility of it happening as all the other factors are there. It would not take much to cause some mixture effect. If clouds are around at your level the humidity is high.. Nev

 

 

[Sapphire]

My ex Sapphire 447 had the carby jut out into the airstream. I know of one Sapphire that went down from icing. I won't fly anything anymore with single ignition and no carby heat.

 

 

[icebob]

Had the same problem and it was icing, purchased an electric de-ice kit from X-air in Ireland(has own web site), problem fixed.

 

Bob.

 

 

[Dieselten]

Carb ice.

 

 

[aviator5177]

I've noticed that my 582 every now and then will do a kind of a stronger shake as if someone would give the airframe a kick.When it happens it will be a single event like that every couple minutes or so (it doesn't start shaking all the time, just one kick, and back to normal).

It seems to happen more on cloudy days or when flying relatively close to clouds (on most days it doesn't happen at all).

 

When it happens all engine parameters stay normal.

 

Does anyone have any suggestions what that could be?

Hi mate, well I guess that there is something in the ignition system. Specially the ignition switch and kill switches. Some time arcing inside the switch can be a possible cause of this misfire. The loud bang or shake means that there is a complete cut off of the ignition to both the cylinder not just one. if one cylinder is misfiring still the engine will run, but if both stop firing for a fraction of a second, then the result will be a big shake or bang.

 

 

[Guest Andys@coffs]

Hi mate, well I guess that there is something in the ignition system. Specially the ignition switch and kill switches. Some time arcing inside the switch can be a possible cause of this misfire. The loud bang or shake means that there is a complete cut off of the ignition to both the cylinder not just one. if one cylinder is misfiring still the engine will run, but if both stop firing for a fraction of a second, then the result will be a big shake or bang.

Dual ignition........for it to do that both ignition circuits need to be suffering at the same time.....Not impossible....but unlikely

 

Don't forget dual ignition isn't ign1 = cyl 1 ign 2 = cyl2

 

rather Ign 1 =cyl 1 and 2, Ign 2 = cyl 1 and 2

 

a fault as you describe would need the earth that the ignition switches provide when off to somehow short both separate ignition lines at the same time

 

Andy

 

 

[Guest nunans]

how did you go with this zibi? have you fixed it yet?

 

 

[Zibi]

Not really,

 

As I've mentioned it doesn't happen all the time, I'd even say it's quite rare.

 

I'm leaning towards the icing theory, so I don't think there is anything I can fix.

 

 

[Guest nunans]

you could fit carb heat and see if that clears it.

 

 

[turboplanner]

Not really,As I've mentioned it doesn't happen all the time, I'd even say it's quite rare.

I'm leaning towards the icing theory, so I don't think there is anything I can fix.

It would be worthwhile for you to study the conditions and symptoms of carb icing, and maybe a few of the accident reports. That way when it happens again you'll be able to make a note of the key meteorological conditions and see if they relate to the event, and you may be able to rule carb ice in or out. If it does correlate, then maybe someone might have information on a possible carb heat kit. With a good carb heat system the return to normal is reasonably quick, and when you test it the hot air effect will change the sound of the engine slightly, so it's a comforting accessory.

 

 

[icebob]

See post number 15.

 

 

[Tex]

I had similar in my 582 Drifter using Avags on a long trip traveling at altitude and also believe it was plug fouling.

 

 

[Yenn]

I'm leaning towards the icing theory, so I don't think there is anything I can fix.

 

Zibi. Do you think that is a wise decision? I know it is an easy decision and one that I might make, but it could get worse. Whatever you do be ready for it too happen again and also to get worse. have a back door escape route. Also keep looking for the cause. It does sound like ice so keep a note of cloud conditions and temperature. Icing does happen to 2 strokes, I did a precautionary landing in a paddock next to home, rather than cross tiger country to my airstrip when I had roughness. Couldn't find any fault so assumed icing.