anjum_jabiru

Gosh No! Would not want to risk it lest the mag fails and the otherwise smooth running engine shuts down last moment. And if the mag was to fail, it could fail on the finals anyways, hence what would be the benefit of that check? Once you are up there you will have to come down at some point. It is possible to avoid take-off but not possible to avoid landing with a failed mag.

Yes, my instructor has now put a new one in as he did not wish to take any chances.

The most likely cause then is probably an overheated magneto, which worked alright after it cooled down a bit.

It seems to be an issue with the Jabs.

{{ title }} The above article seems to suggest that it is very much possible for fuel to foul the spark plugs.

I agree with Jetboy that the mags may not run when hot and run once again when they are back to normal temperature. But what could have made them hot in the first place. Taxiing about 400m at a low rpm from start up is highly unlikely to make them that hot.

I was thinking in terms of an overflow. I had similar problems from a motor bike and the engine would not start. But when the excess fuel evaporated it was good to go. (As you can see, I am not a mechanical engineer.)

The question really is that - Is shutting off both mags at the same time on finals (with ROM around 1800) cause any damage to the magnetos? The reason for asking is that after doing a full stop landing and parking the aircraft, a few minutes later when wanting to go up again after a break, the right magneto seemed to be giving some problems. After starting the engine with both switches / magnetos on in the Jab LSA, I taxied to the holding area to perform the pre-take off checks. While doing a pre-take off check at 1800 RPM, on shutting "off" the left switch / magneto, the engine shut down completely, although the right magneto was switched to "on" position. This sort of a thing has never happened before. On doing the checks a second time to make sure that I had done the checks correctly, the engine shut down again on switching "off" the left switch / magneto in the Jab LSA. I then restarted the engine leaving both magnetos on as usual and taxied back to the parking area. I told my instructor, who also maintains the aircraft himself about the problem. When he performed the checks, the mags seemed to be ok and the engine did not shut down. However as a precautionary measure he changed the right magneto on the aircraft as it had behaved inappropriately. As Dick Gower rightly pointed out - "If the mags are off and the prop windmilling there is a risk of plug fouling from all of the fuel that is still passing through the engine without being ignited." [Thanks Dick for your contribution. I see that you don't post often but when you do, it makes a lot of sense!] In that case I am wondering if the magnetos were actually ok but it was plug fouling of the spark plugs supplied by the right magneto which actually led to the problems. And once I taxied back to the starting point, the plug fouling might have cleared up, as any excess fuel might have got burnt up, hence the problem was never repeated!

Hi Biggles, I am not very sure. I will find out next time and let you know buddy :)

It is the school's aircraft. The cylinder head temps are touching the 150 mark just after a climb to 1000' AGL, and hover just under that mark for a while. I guess I am a bit over cautious (or you may call me obsessive) and would like the needle to point exactly in between the 100 - 150 mark, hence I try and get it there whenever possible. It does not overheat but I don't like the idea of the needle hovering just under the 150 mark for a long time in cruise flight.

It is generally pretty bumpy where I fly most of the time. Hence I tend not to go above the cruise speed which is about 90 knots in a Jab LSA (upper limit of green arc). Field Elevation is about 1000' and I fly at around 2500' - 3000'. Since the minimum height should be 1000' AGL and if I am flying at 2500' (ie 1500' AGL), it leaves me with only 500'at my disposal in which I need to cool the engine down without losing any more altitude. The aim is to keep the cylinder head temperature between 100 - 150 'C... And then what? Climb back up to 1500' AGL?!

Thanks for contributing your posts. On the same note what would would you do if you were flying at say at 2000 feet AGL and your engine became too hot at cruise speed. Would you rather put the nose down and allow the speed to build up into the yellow arc (thus stressing the airframe), allowing more air over the engine to cool the engine down, or would you rather reduce the power and raise the nose to maintain altitude but sacrifice your speed a little (still remaining in the green arc)? It seems like a catch 22 to me. - My instructor has suggested that I lower the nose to improve airflow over the engine, in the Jabura LSA that I fly. But that would mean increasing the engine power to maintain altitude, which would in turn generate more heat. Sorry if I sound confusing. The choice is between raising the nose and decreasing power vs lowering the nose and increasing power. Have your pick. - On the contrary if the engine is running cold, I believe pulling the carb heat out would solve the problem with icing as directed by my flight instructor.

I guess that the whole point of the exercise was to demonstrate that if everything goes quiet and the propeller stops there is no need to panic and crash the plane. Unlike GA the final approach in ultralights is almost always like a glide approach from a safe height above the runway. It is debatable if it was the right decision had the landing gone wrong, but my guess is that a CFI would never do it unless he was confident of his student's flying skills and his own ability to salvage the situation.

Roscoe & Happy Flyer - Yes, there seems to be not much point in posting these issues here or bouncing of ideas and getting the opinions of other people. Just to let you know that opinions of different people tend to differ on the same issues. I wonder if you have heard anything about group discussions and brain storming. 1 to 1 teaching may or may not be the best form of learning strategy as one is limited to the opinion of a single person rather than sharing ideas and experiences of other people who may have been involved in a similar situation. I adore my CFI as he is a lovely person, experienced pilot and an excellent teacher. If my CFI shuts the engine off to check the student's reaction in a controlled environment and see if they can bring it down safely then I believe this is the best form of training.

I am wondering if it could be the problem with the actual switch rather than the mags. Later on the engine was running fine when it was started with only 1 mag at a time to check for faults. Is it possible for mags to work when the engine has been started in idle and then quit on a higher rpm? It somehow does not make sense to me that it should work fine sometimes and then quit on some occasions. Either the mag should work or not work. Is it possible that it might be the switch might be faulty?

Hi Guys I had my passenger endorsement test done today. On late finals my instructor reached out and shut off both mags at around 1800 rpm, to check if I can bring it home safely. All went well until I decided to go up again after passing my endorsement rating. During the pre-take off run up and mag checks, as soon as I switched off the left mag on the Jab with engine running at 1800 rpm, the engine quit. Believing it to be some form of oversight on my part I repeated the checks and the engine quit again as soon as I switched off my left mag. I then decided to restart the engine using both mags as usual and end the flight. My question is - Is it possible that if someone switched off both mags simultaneously with the engine running at 1800 rpm in mid flight, this could result in any form of damage to the magnetos or the engine? Thanks again for your input.

If they are accepting dvla then looks like they have dropped it for ppl.

RAMPC is not much different from the requirements of PRIVATE Aus road medical. I am a GP who conducts Driver Medicals routinely and have had a look at RAMPC. And PRIVATE Driver Medicals in Aus are very similar to those in UK. I was a GP in UK for 4 yrs before moving to Australia :) But yes, if RAMPC was to go then it would mean less paper work and less cost to everyone except his GP.

Never. I am only talking of dire emergency.

Yes, that is why I am talking to you guys so that I can learn something. I always thought that it is very useful in case of an emergency if you suddenly lost sight of the horizon. Just wanted to make sure why the slip/turn coordinator worked with the switch off. I was unaware they worked independently of each other, and only the slip indicator was functional with the switch off. I have now been enlightened.

Frank & Russ - I followed Russ's advice and contacted Jabiru. Frank was correct. The slip indicator is not power driven and hence will continue to move even with the switch turned off. The turn indicator is the one that actually requires the gyro / power and the switch is to power the turn indicator.

It is definitely for the gyro as I can only hear the whirring when switched on, which stops after a few seconds once all switches are off. I think it is for the turn indicator / to improve accuracy of the slip and turn coordinator.

... And die young leaving their women behind to have fun with other real men

Thanks. This sums it up :)

Now that you mention it, I am sure of the ball moving (slip indicator) but can not recollect the miniature white aeroplane (turn indicator) moving or not. I think you may have nailed it. It must be the ball that moves but not turn indicator. I will check it the next time I take it up and let you know.