Flying Lesson #16 - Excessive Magneto Drop
It's been two weeks since I have been back up in the skies. I had to cancel the last three flights due to bad weather. It was windy today also, but my CFI and I decided we needed to get me back in the air. The fuel was topped off, 5 quarts of oil, no physical damage to the plane, everything appeared normal. At run-up, I tested the magnetos and found the right magneto dropped 200 rpms. (Magnetos generate high voltage electrical energy to the spark plugs.)
Magnetos, individually, should not exceed a drop of more than 125 rpms. I am not an expert, but would you say a 200 rpm drop is excessive? My CFI said it most likely was due to lead soiling the spark plugs. He leaned the mixture for several seconds waiting for the higher combustion temperatures to burn off any deposits. He had to attempt this several times before the drop fell in the allowable limits. Still, I was a little apprehensive about flying. I wanted to feign an illness - blame my allergies.. :(
From what I've read, a 200 rpm magneto drop could indicate a bad plug, or bad spark plug lead. They say 70% of airplane accidents are pilot error due to bad decision making. Should we have flown?? In this report, the engine should be inspected before flight if magnetos fall out of allowable limits. I am sure there are shortcuts or ways around a certain problem, but should we have remained grounded and get the engine checked??
We practiced couple of slow flights, power off stalls and power on stalls. He was very impressed with my slow flights and stall recoveries. However, I do need to get in the habit of looking outside the plane and clearing my turns.
I was very disappointed in my landings today. More importantly, I am weary about getting back into that plane. I think if the magnetos drop outside of the allowable limits again, I am going to tell my CFI that I don't want to fly. I'm sure it was nothing serious but I don't have 9 lives..
p.s. Chris, if you can advise, it would sure put my mind at ease...
Hrs to date: 17.6 hours
posted at
5:31 PM
7 Comments:
It's happened to me several times. I'd say if you lean it out and it corrects the symptom then it's good to go. A lot of time the engine may foul up. It happens a lot in dirt bikes too. If leaning it out didn't fix the problem then definintly call the "NO GO" =)
at 10:40 PM
I wouldn't go up a second time if that happens because there must be something causing that problem to re-occur. Follow your instincts on that one. I hate writing songs about dead friends.
at 3:38 AM
Thanks Richard, that's what my CFI told me too. Maybe I'm the worry wort :)
Bud -- make sure my song is haunting :)
at 6:51 AM
Aymiee -
First and foremost: If you're not comfortable with the airplane at anytime, then trust your instincts and don't go. You WILL always get another chance to fly & a No Go decision is never a bad one!
As to the Mag Drop. Probably was fouled plugs. Since it did clear after leaning and running up the engine up a couple of times. I would have been satisfied. But that's me.
Now if the engine had been spittin & poppin & backfiring, or hard to start in anyway, then I'd a parked her and fetch some tools to figgure out what was up...
The problem with rental airplanes is that they get flown by everybody and some operate them correctly and some don't. If the last person to fly it, flew around all day full rich, it's pretty easy to foul plugs.
But the bottom line is this. If you don't feel right about flying, then don't! Don't ever let anyone talk you into the air... even if they have more "Experience" than you.
Don't let this experience deter you from your goal. As you saw the engine did clear up and ran well and you're here to tell us all about it. So now you have a new basis to use for your own judgment next time.
My favorite aviation quote comes from one of the flying columnists, I can't remeber his name now but it goes:
"Experience is a cruel instructor!
First you take the test, then you learn the lesson"
P.S. -
Jessica makes me CD's of new music she thinks I'll like from time to time. The latest "Daddy's Mix" has alot of a new band I really like...
"Maroon 5 "
So I got tickets for the fair Saturday for me and the gurls. I may be their oldest fan.
at 7:37 AM
Guys: My CFI just told me that both 152's (the one I flew in on Sunday)just went down for maintenance today. Yikes!!
Chris - Maroon 5 rocks!!!! Your daughter definitely has good taste. She might also like Interpol!!
And yes, experience is a cruel instructor...I'm sure being adequately prepared would help the outcome also.
at 10:49 AM
Aymiee-
Are they down for SCHEDULED MAINTENANCE. I believe that Part 135 operators have to perform 100 hour inspections. So it could be coincidence that the maint happens now.
If not, ask him what the problem is: A new Airworthiness Directive, or some problem. I always liked to know what was being done to the planes I fly and why.
at 11:59 AM
Listen to Chris, Aymiee. He not only makes sense but he digs Maroon 5. I like that mix a lot.
I'll give you haunting but I'll also give you pissed if you go down.
at 5:52 PM
Post a Comment
<< Home