Yesterday I flew to Eugene with a friend I promised I would take flying sometime. Little did he know this would be more of an adventure than he signed up for. The flight there was fantastic. We flew IFR, because it had been a little while since I had been “in the system” and even the the weather was pretty good VFR weather, I like to keep current on at least IFR operations, even if it’s not necessarily in IMC.
Well, we arrived in Eugene, stretched at FlightCraft for a bit, watched the Seahawks kill the Rams, then went out to begin our trek home. Before takeoff, I do what’s called a runup. This is where you do your last minute checks to make sure all the radios and avionics are set, and you also runup the engine to about 3/4 power(1700 rpm in my case) and check the magnetoes. The Cessna 172 engine has a dual magneto system for reliability and efficiency. Each magneto supplies the spark for a spark plug on each of the cylinders. So each cylinder has two spark plugs. Well during the runup procedure you check the left magneto and the right magneto, to make sure that each side is working properly. Because of the redundancy, you would probably never know if one went bad unless you manually shut one side off. Well in switching to the right side, the engine lost between 200 – 250 RPMs and began shaking vibrantly. The POH (Pilots Operating Handbook) for this aircraft states, “RPM drop should not exceed 125 RPM on either magneto or show greater than 50 RPM differential between magnetos”. This can sometimes be “normal” when you have a carbon fouled spark plug. To clear the carbon fouled plug you would increase power and lean the mixture. This, in effect, would burn off the carbon or oil that has contaminated the plug. Well I did that a few times, and the right side magneto never got better. The left side however was running like a champ. I was very bummed, but I opted to taxi back and call the owner to see if he had any other ideas. After talking to him and some other pilots in the area, we all agreed that there was something wrong with the airplane, most likely a bad magneto. So we had to find ourselves a ride home. I was waiting for the Lear 31 pilots that I was talking to, to offer a ride on their way back to Spokane, but that didn’t happen. lol.
My friends wife came down and picked us up and took us back to SLE. We left Salem for a quick flight to Eugene and back at 3pm. I got back to SLE at 9pm. What a day.
Right now the plane is getting looked at and I will keep you all posted on the cause of the problem.
Tags: engine problems, KEUG, single engine, time building
September 15th, 2009 at 6:35 am
Wow…I have no idea what half this stuff means…
September 15th, 2009 at 6:54 am
Haha, well I can explain it to you in more detail if you want…
So yesterday, I had a friend of mine at the airport take me down to Eugene in his Cessna 180 to pick up the club plane. Boy that was helpful. Definitely beet driving, for sure!
Turns out it WAS fouled spark plugs. I guess it was just gunked up enough that the normal “burning off” procedure wasn’t clearing them. Bit of an inconvenience, but worked out in the end.
September 17th, 2009 at 6:42 pm
Sounds like your having a good time. When can you fly to hawaii? Just kidding.
September 21st, 2009 at 8:57 am
Interesting blog!
I own/operate a 1966 Mooney. Its a bit different owning than renting, because I’ve learned a LOT about maintenance (and have a lot to learn). One thing my mechanic suggested when I first bought the airplane was to always travel with a spare spark plug and the tools to change it. Removing and replacing plugs is one of the things an owner/pilot is allowed to do under part 43 preventative maintenance w/o A&P supervision.
Anyway in the past couple years I’ve had several fouled plugs — and no, they don’t always clear with an agressive runup. My tool kit also contains some dental-pick style tools to clean the plugs, and usually when a fouled plug occurs there is a little “dot” of hard carbon shorting the plug electrode, rendering it useless.
The trouble is, stopping to take care of the problem – even without having to wait for a mechanic and having tools available – takes 30 minutes to an hour by the time all is said and done.
I realize that clearing a fouled plug isn’t something a renter pilot can typically do, but you might have a mechanic show you how to deal with it sometime, lest this occur when you’re out in the middle of nowhere.
and good job on scrubbing the flight instead of taking off in that condition.