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"Engine reliability"
9 posts
pkoszegiMarch 28, 2014, 6:13am
A week ago my student on the Cora checked spark plugs and cht senders. (503 inverted engine) We flew 4 hours or so and about 15 landings since that. Yesterday we went x country. Landed safely after 140 km on a grass airport. It was 25 km/h headwind and a bit bumpy.
Than he went on a check ride with an other instructor (you cant release your student here without x check by and other instructor) the guy is a big guy together they were I think around 220-230 kg. They taxied to the runway and tried to take off, they aborted the take of half way. They taxied back and attempted an other takeoff. Well that was a long one.
On the pattern in about 1 minute later they heard a bang, engine was running, no power and weird noise and made a dead stick landing on the airport without problem (instructor handled the case).
They stopped in the middle of the airport.
As I arrived with a car and a rope to pull them back to the hangars I saw that a spark plug cable with a pug still inside it hanging down at the nose gear.
There was no damage nor the thread on the plug neither in the cylinder. There was no washer on the plug however which does not used to fall off easily. I checked all other 3 plugs. 1 of them were missing the washer, one other was very loose, the other was ok. The guy did not tighten them properly.
The spark plug after 4-5 hours and a number of takeoff simply screwed out by vibration.
I put it back, checked the engine on the ground by full rpm and there was no problem with it whatsoever. After this the plane flew an other 5-6 takeoffs and we managed back to our base airport 140 km in 1h 15 min, with a 25 km/h tailwind.

This is a story how much an engine or someone could be reliable and how much you can trust an ultralight and should be prepared at any time for dead stick landing.

PUFFMarch 28, 2014, 11:37am
Any time my plugs come out, I use a torque wrench when re-installing them.....  Properly, by the book...
I've only got the 2, so I must rely on them.  I use an inch- pound torque wrench, set to proper specs per rotax.

I would always ensure I have a decent place to crash land if I can.

Got a nick name for your student........."Sparky"....
Think I'd make a necklace out of that plug....
maxpayneMarch 29, 2014, 3:18pm
Glad it all worked out for you. I have a spring with a rubber hose over it stretched over the plugs to keep the boot on and I beleive it would prevent the plug from backing out by unscrewing.
texasbuzzardMarch 29, 2014, 6:08pm
I would also suggest that you use solid cap spark plugs especially on inverted engines if you are not already doing so.

monte
pkoszegiMarch 29, 2014, 6:33pm
The plugs were solid cap plugs... it does turn in the boot. The right thing to do is to tighten them as factory recommends and use a proper tool not one of these junks:


attachment
LarryMarch 29, 2014, 6:41pm
I wonder why the washers were not on the plugs...I don't have one on mine, but that's due to having only one and the CHT ring is between the plug and the head.
I've heard of this happening though. Glad you were able to make a good on field landing and found the problem easily fixable. Might be a good preflight item to check..
Larry
a mile of road will take you a mile, a mile of runway can take you anywhere.
RicardoMarch 30, 2014, 2:28am
Preflight: Always check the plugs for good connection and tightness. No washer's on my 447 also for the same reason as Larry's.
texasbuzzardMarch 30, 2014, 6:29pm
good idea Larry, I have always ran a washer with my cht probe.... might up my compression a bit.

monte
Hay bailApril 1, 2014, 1:21am
I have been concerned about plug back out myself, I am experimenting on my out board 1st. Drilling a safety wire hole in the plug nut along the horizontal, there are also nut locks that may work that slip over the nut but are not fixed.