Intermittent engine problem 3300A

[mch]

Hi all,

 

on my last flight I encountered a serious engine problem. I was flying for 3h at that time without problems but mayby an anomaly. Since I don't know much about the different modes of failure I'd like to ask if anyone recognizes the symptoms.

 

I was flying for 3h in moist air (but no rain). Almost all the time at about 2400 rpm, AVGAS, EGT at 680. Oil temp/press all the time 69/2.9, CHT about 120-130.

 

I noticed at times that all of a sudden the EGT started to change in weird way. One side would go up (720+), the other down (630-). That resulted in a difference of 100 degrees while no other parameter changed. Lits/h the same, rpm the same, CHT and oil the same.

 

This happened 3-4 times. I applied carb heat + some throttle play and everytime managed to get it back to both sides equal again at 680 EGT.

 

Then, after 3h I started to get into rain. No problem, I flew the aircraft in rain, and heavier one, before. Temp was +10 degrees so I would not have been surprised about carb ice, I actually was prepared for that. Nothing happened for a while, though.

 

Then, really ALL OF A SUDDEN, the engine began not only to run rough but began to shake violently and lost all power. I applied carb heat at once and the shaking would stop after some time (maybe 10s), so I thought, well, that was quick ice.

 

But after some more seconds the same happened again, though of course carb heat was on still. The engine was close on stopping again, with some throttle play I got it running again.

 

Since I did not know the cause of the problem I made an immediate safety landing.

 

On the ground the engine ran again quite normal.

 

I have not been at the aircraft again until now, since the airfield is 150km from my home base and I had to leave it there (in a hangar) to get back to work the next day.

 

Now I'm wondering what could have happened and where to look for problems.

 

Normally with carb ice the engine starts to loose power and begins to run rough in a more gentle manner, at least this is my experience with a C172. Carb heat removes the problem as long as it is applied (in icing condition).

 

Here the drop and shake was absolutely sudden and really frigthening - I even thought of a missing propeller tip and an unbalanced momentum.

 

I also do not understand why the problem reoccured with carb heat on.

 

In the meantime I have thought about water in the fuel. I had drained before and no problems for 3h. I will check for water once I am at the aircraft again.

 

Does anybody recognize this symptoms? What should I look for?

 

Any explanation for the EGT mismatch, which I also encountered the first time at that flight? Maybe the same cause?

 

Mike

 

J400, Germany

 

 

[alf jessup]

Mike,

 

Sounds to me like a serious dose of carby ice, probably broke off the butterfly and deadened a cylinder for a few seconds, chunks of ice have been know to hit the plug tips and close the gaps.

 

I'm guess it was carb ice but that is only my opinion.

 

I have heard of a 6 cylinder Jab motor at my local getting carby ice on taxi and I'm guessing it happens to the 4 cylinder ones also

 

Cheers

 

Alf

 

 

[alf jessup]

Mike,

 

Also forgot to mention in my last post it could have also had some ice build up in the intake area which could have broken off and went through the carby.

 

Alf

 

 

[jetjr]

Im guessing ice - the symptoms are perfect for it.

 

Running at 2400 it will become quite thick before you notice much. Its not recommended to run at these lower revs for long as it can harm engine

 

Oil temps are cool too, much below 80 also isnt recommended I think

 

Remember theres no problem in Jab aircraft (with std airbox) running heat all the time

 

There are electric heat probes availiable too. - Skycraft in UK

 

Rain usually avoided too due to timber prop damage and J200-400 leak in flight a bit

 

If using timber prop in rain you could have damaged leading edge and I have seen one bad enough to vibrate badly. front 5-8mm worn off.

 

 

[peterm]

have seen exhaust valves stick in from carbon on the valvestem in the 2200 once fixed it self after about 5 min another time had to land and take head off to free valve & put new one in,it shakes quite violently on 3 cylinders it wouldnt happen with solid tappets

 

 

[mch]

Hi Alf & jetr,

 

the carb icing was my first thought as well, but I did not realize it could build up without symptoms and then break loose like hell. If it has been so it will be difficult to proove. Yet it looks like a plausible explanation. In hindsight I should not have been prepared for icing, as I was, but used carb heat well in advance.

 

The low rev of 2400 was due to an economy flight, I must someday change my needle to one that allows me to use more power at reasonable fuel flow.It's on the agenda.

 

About rain & prop: Everytime I cross rain I check the prop afterwards for damage. None yet. Of course I do not look out for rain :) I'm living in the most rainy corner of Germany and it is quite frequent that we have local drizzle or showers here, but after 30 min of flight you are out of the bad weather.

 

jetr: What do you mean by "the J400 leak in flight a bit"? Do you mean water can get into the tanks or something else?

 

Anyway, since the engine ran smooth on the ground again I suspect that at least at the moment the prop is still OK (balance) and all cylinders are firing. But I have left the aircraft there without any checks, I will do all checks next week when I'm there again.

 

Dexter & peterm:

 

You both suggest carbon at the valve stems. I have never heard of that, I have heard of lead (AVGAS) at the valve stems, though. Since I am no motor expert, can you tell me more about how the carbon could have got there?

 

The compression check is a good idea, I would have missed that!

 

Mike

 

 

[jetjr]

My J200, and plenty of others, fitted leak at the front of the doors when flying in rain

 

Pilot can get wet and it can come into instrument panel too.

 

Newest models have rain gutters around doors which stops this as well as leaking when parked outside

 

Mine can have the floor fill up ~20mm deep in heavy rain. Need to drill a hole.

 

 

[Modest Pilot]

Carb Ice can be a real problem on Bings, a friend was flying off his intial 25 hr test flying time over the airfield in his Pulsar (3300A engine) on a fine humid day and the engine stopped dead. On landing after recovering power with carb heat there was still some ice in the carb. The engineers at Jabiru in Bundaberg advise me not to operate at below 2700rpm. I was worried as EGT's are 700F at this setting, far better to go for revs they say.

 

 

[dazza 38]

Carb Ice can be a real problem on Bings, a friend was flying off his intial 25 hr test flying time over the airfield in his Pulsar (3300A engine) on a fine humid day and the engine stopped dead. On landing after recovering power with carb heat there was still some ice in the carb. The engineers at Jabiru in Bundaberg advise me not to operate at below 2700rpm. I was worried as EGT's are 700F at this setting, far better to go for revs they say.

I agree with modest pilot, i havent flown a jabby for a long time, but alot of guys i know do.They say they perform best, if they are flown hard, high RPM. Not baby sitted (low RPM).They are more reliable, if treated that way.Just my thoughts. Cheers

 

 

[wizzard1964]

:big_grin:

 

Carby Ice and slow revs... the 3300 will sit on 3000 + RPM all day and run smoother...

 

I have a 2200 , I sit on 2900 average. ( the book says 3050 max rpm) The only time I ever slow to 2400 is on downwind..

 

My mate has a 3300, he cruises around the 3000 rpm 99% of the time. As far as I know the 3300engine tops out at 3300 rpm....

 

I've experienced carby ice on a reasonably warm day, after only around 1000ft decent.

 

I also noticed it seemed to surge a bit when I left the carby heat on for an extended period (one only)...

 

So, work it harder and use carby heat when theres moisture about, especially a change..

 

TTFN Warick :big_grin:

 

 

[PKnight]

This is a copy of a post I made on the Jabiru Owners Forum. Your problem sounds like a classic case of carb ice, may be in the induction manifold.

 

I didn't expect that to happen... -- Peter Knight, 20:09:10 06/04/10 Fri (88.105.183.89)

 

G-PHYZ is a 230hr J430 and 'normally' performs flawlessly. It has an ST Aviation electric carb heater with one element permanently ON and the other switchable. It has a temperature probe thermopasted to the carb body and a second probe in the airbox. It also has the standard Jabiru carb hot air which I use. I though the belts were very well attached to the bracers

 

I was flying from Halfpenny Green to Haverfordwest today in haze at FL60. I had used carb hot air from time to time as the relative humidity was high. When I pull Carb hot air on the airbox temperature reaches plus 50C in about 10 secs and the carb body temperature starts to rise after about 45 secs. I normally put Hot Air off after another 15 secs. The carb body temperature continues to rise for a bit as there is a bit of thermal energy still stored in the air box.

 

Anyway I was dodging a few clouds when I had that feeling that all was not quite right with the engine. Carb ice perhaps? Couldn't be that as carb body temperature was reading 15 degs C. No ice is going to form on the carb if it is that warm surely. (I was once a physicist and thought I recalled somthing about ice and 0 deg C!). Any way I applied Hot Air and left it on while I watched the carb body temperature rise to 18 deg C. Intake air temp was over 50 deg C. I done my duty so switched off Hot Air.

 

About 15 - 30 seconds later engine goes very sick and twitchy just like it is trying to eat ice cubes.

 

Bit of a pnaic as I am over the lumpy bit of Wales with no flat fields in sight so straight to 121.5. They were brilliant and gave me vectors to Swansea while I put all the carb heat on I could find together with the fuel pump and got the engine back to smooth running.

 

Landed safely at Swansea (got a free cup of tea as I was gibbering slightly) although engine was now running perfectly.

 

After discussion with Gary problem seems to be that ice can form in the induction pipes downstream of the carb. I must admit I had not realised this as I had assumed the pipes were kept sufficienty warmed by the hot air from the ram air ducts to remove this possibility. The 'gotcha' is that even with electric carb heat permanently on and the carb body temp reading 15 deg and occasional use of hot air you can still get ice forming that you cannot detect.

 

I admit that the met conditions were extreme for giving Carb icing and my cloud dodging and level changes probably made matters worse but I was very surprised at the induction ice particularly as every other indication was that the actual carb temp was OK.

 

Hope these observations help others as the carb icing seasons starts up.

 

Peter

 

 

[mch]

Finally engine checked, one general advice for MOGAS users

 

Hi all,

 

thanks for all the suggestions. I feel I should post the result of the engine check I did with a "real" aviation mechanic yesterday.

 

About one month ago I flew the jab back to my home strip on a very warm day. This was the first flight after the reported problem (enigine loosing power and shaking rather violently) and during that flight the engine made no trouble.

 

The check yesterday revealed two potential problem areas:

 

1. Compression on one cyl. (No.1 ) was sub par on leakage test. The cylinder blows slightly into the oil and also into the exhaust. The drop is not serious now but must be watched for further degradation. I have a hydraulic lifter engine and the lifters were OK.

 

2. I loose some oil in the right distributor. The leak is very small, so I did not see excessive oil consumption nor traces outside the distributor housing. I will have replaced the gasket. The oil leak could account for one ignition circuit failure if getting more serios.

 

So since we did not find a real explanation I tend to accept the carb ice theory by now. After all I expected carb ice anyway and should have used carb heating in advance, not waiting for the symptom. All spark plugs (iridium type) were in very good order after 250+ hours, no signs of wrong mixture or lead dendrites. We replaced them anyway.

 

One suggestion for MOGAS users as as side remark:

 

I used a paper fuel filter. Since I plan to run on MOGAS again (last 25h AVGAS) the mechanic suggested strongly to replace it by a filter with a solid mesh. The reason he gave is this: If one gets by accident wet fuel one may not be able to drain it if the MOGAS has ethanol in it. The ethanol can absorb quite some water. That I knew. But the paper filter can get clogged by the water up to a point where it will starve the engine. This I did NOT know. We replaced the filter.

 

Regards to all,

 

Mike

 

 

[bushpilot]

Last Friday, whilst working with a student on a flight from Cobar to Dubbo, we experienced carby icing in our J230 4 times in one hour - all whilst flying straight and level.. First sign was a noticeable drop in revs, then rough running. So best advice is to try carby heat with any of these symptoms, especially if all engine gauges look normal...

 

 

[Highlander]

I had the same problem with my jabiru J430 the last 3 times in flight.Just after take off the engine start to loose bit power,then after 10 sec the one EGT went up and the engine start to run rough.Apply carb heat and after 15 sec the engine was running normal.I climb to 2000- ft AGL and 15 min in flight 2850 rpm and fuel flow 20 liter/hour and carb heat on from first problem i notice one EGT went up and the other came down i bit.After n few sec power less and engine run rough for 10-15 sec.There after it happens once agian and i landed,Any suggestion ,was in for 50hr service and is the same after service.Time on engine 620hr.One thing that is funny is the fuel flow on take off showed 21 liter and after i turn the fuel pump off the fuel flow went up to 29 liters (should be 37 liters) and in straight and level it settle on 20 liter again.

 

Christo

 

 

[zodiacpilot]

Jabiru engine manual says carb needle transitions from cruise mixture to full power mixture at 2850 rpm. Spot on on my A3300, 21 lph at 2800-2850 rpm, 29-32 lph at 2900rpm. I can watch cht & egt change as I transition.

 

Consequently I cruise at 2800-2850 in the Zodiac, have never yet encountered carb ice at this setting.

 

 

[dmech]

Hi all,on my last flight I encountered a serious engine problem. I was flying for 3h at that time without problems but mayby an anomaly. Since I don't know much about the different modes of failure I'd like to ask if anyone recognizes the symptoms.

 

I was flying for 3h in moist air (but no rain). Almost all the time at about 2400 rpm, AVGAS, EGT at 680. Oil temp/press all the time 69/2.9, CHT about 120-130.

 

I noticed at times that all of a sudden the EGT started to change in weird way. One side would go up (720+), the other down (630-). That resulted in a difference of 100 degrees while no other parameter changed. Lits/h the same, rpm the same, CHT and oil the same.

 

This happened 3-4 times. I applied carb heat + some throttle play and everytime managed to get it back to both sides equal again at 680 EGT.

 

Then, after 3h I started to get into rain. No problem, I flew the aircraft in rain, and heavier one, before. Temp was +10 degrees so I would not have been surprised about carb ice, I actually was prepared for that. Nothing happened for a while, though.

 

Then, really ALL OF A SUDDEN, the engine began not only to run rough but began to shake violently and lost all power. I applied carb heat at once and the shaking would stop after some time (maybe 10s), so I thought, well, that was quick ice.

 

But after some more seconds the same happened again, though of course carb heat was on still. The engine was close on stopping again, with some throttle play I got it running again.

 

Since I did not know the cause of the problem I made an immediate safety landing.

 

On the ground the engine ran again quite normal.

 

I have not been at the aircraft again until now, since the airfield is 150km from my home base and I had to leave it there (in a hangar) to get back to work the next day.

 

Now I'm wondering what could have happened and where to look for problems.

 

Normally with carb ice the engine starts to loose power and begins to run rough in a more gentle manner, at least this is my experience with a C172. Carb heat removes the problem as long as it is applied (in icing condition).

 

Here the drop and shake was absolutely sudden and really frigthening - I even thought of a missing propeller tip and an unbalanced momentum.

 

I also do not understand why the problem reoccured with carb heat on.

 

In the meantime I have thought about water in the fuel. I had drained before and no problems for 3h. I will check for water once I am at the aircraft again.

 

Does anybody recognize this symptoms? What should I look for?

 

Any explanation for the EGT mismatch, which I also encountered the first time at that flight? Maybe the same cause?

 

Mike

 

J400, Germany

[dmech]

sticking ex valve will increase egt moisture will expand the carbon on the stem ,causing the sticking , this can happen regardless if hyd lifter or not jab engines get carbon build up on stem when run on leaded fuel , problem not so common when run on unleaded car fuel. old tappet engines valves stick to but not as much but still enough to burn valves