If there is a doubt...

[Ghery]

My son and I went to the airport after work to grab the Arrow and fly up to PWT for dinner. Preflight went fine and the engine fired right up. Got cleared to rwy 26 and taxied down to the run-up spot. All was going great until I checked the mags. R - OK, L - 200 to 300 rpm drop and rough (max is 175 rpm and both should be within 50 rpm of each other). Tried leaning the mixture to burn out whatever might have been fouling a plug with no success. Each time I went to L and back to Both there was a pretty good bang. Rats. Called the tower with a change of plans and went back to the hangar and put it away. Called the maintenance officer to report the problem, wrote it up in the log and went home.

Nice clear day (too hot, actually). Would have been a lovely flight to chase some of the best fish and chips in the state. However, when the run up is so bad that one's non-pilot son notices the problem, there really isn't a doubt about what to do, now is there.

Oh well, gave me time to fix a software problem on my computer and a more leisurley packing for a trip to Chicago tomorrow.

 

[SkyHog]

after stories like this - one has to wonder why people find it acceptable to takeoff without doing a runup. Just imagine the possible consequences.

It always blows my mind when I am taxiing behind someone for takeoff, and that person calls their takeoff while on the roll towards the runway, then takes off. No checks of any kind.

 

[Paul Allen]

after stories like this - one has to wonder why people find it acceptable to takeoff without doing a runup. Just imagine the possible consequences.

It always blows my mind when I am taxiing behind someone for takeoff, and that person calls their takeoff while on the roll towards the runway, then takes off. No checks of any kind.

I see it all the time. Some people are crazy. When they have an accident it makes us all look bad and it seems like every time I pick up a newspaper I'm reading about a small plane going down. I've had the same problem as Ghery and I had to leave the plane and drive a rental car home. It's not fun, but at the end of the day I'm still alive.

 

[Maverick]

I was once returning from a Civil Air Patrol mission flying a military aero club airplane. The airplane was based at the local Air National Guard base where we could not buy fuel. There was a small airport nearby where we always fueled up before returning to the base.

Anyway, I had the airplane all day and everything was fine during all my flights. I stopped for fuel and taxied for departure, did my runup and found that the left Mag was dead. I taxied the aircraft back to the ramp and called the club's maintenance officer and then made another call for a ride home. I guess my point here is that you never know when something like this might happen. I've heard some say that one runup a day is fine. If I had followed that logic I would have been flying on one Mag.

It sure was fun flying Cessnas off the 9,000 runway at Selfridge ANGB though. But alas, all good things come to an end. The club was eventually forced to leave the base for a new home at a small airport.

Jeannie

 

[Jeff Oslick]

I'm curious what they find to be the cause of the squawk. Sooo many rental/club planes that get fouled plugs, especially in the summer, because folks aren't taught to agressively lean on the ground. Here in sunny, hot SoCal my partners and I have gone through the summer so far without a single rough/bad mag check, largely (or entirely) because we are all diligent about pulling out the red knob as soon as the post-start engine checks are done. When I was renting, I couldn't get 5 flights in without finding a rough mag at runup (usually, but not always, I could clear it with a lean 30sec-1min runup at ~2,000 RPM).

 

[EdFred]

after stories like this - one has to wonder why people find it acceptable to takeoff without doing a runup. Just imagine the possible consequences.

It always blows my mind when I am taxiing behind someone for takeoff, and that person calls their takeoff while on the roll towards the runway, then takes off. No checks of any kind.

Nick -

If you're following me, and it looks like I did that, I probably did my run up during taxi. I know, some people think that's crazy, but sometimes I do it to hold my place in line, because I don't know if the guy behind me is going to take 10 minutes at the hold line to do everything. If it's dead at the airport, I'll stop and do it. But if it's towered, or there's quite a few people out. I'm doing run up during taxi.

 

[The Old Man]

I've heard some say that one runup a day is fine. If I had followed that logic I would have been flying on one Mag.

I personally use one runup per start. If it flew in and the engine wasn't shut down, it should be good to go.

I DO lean some immediately after startup and after turning off the runway on landing. So far, so good. Only once had a rough mag and then it was only about a 50rpm difference.

 

[Tom-D]

If you lost a mag in flight, wouldn't you notice it?

The act of shutting down should not harm the mag.

So, if it ran fine at the start of the day, you ran it normaly, why would it be bad durning the day with out you knowing it?

 

[Dave Siciliano]

There are several ways to do mag checks: not everyone does them in the runup area.

I do a mag check before each flight, but sometimes while waiting to cross an active or during taxi. If I'm departing north, I do the normal run up. If departing south, I have to taxi the length of the runway (7400 feet) and cross the active. This gives me plenty of time to to a pre-takeoff and runup check. If it's low IMC, I'll stop at the departure end anyway to put in nav aides, flight plans, etc. On more than one occassion, someone has blocked the taxi way doing a run up check or jets block it awaiting IFR clearance. If my run up check is already done, I'll depart from an intersection before I get to the run up area--VFR if conditions merit.

In the air, I usually turn off one mag somewhere enroute to do a lean of peak mag check. This is a much harder check of the system and plugs than a gound check. I often find a plug that is going bad early and replace it. I wouldn't do this in a rental plane. Normally, CHTs drop a little, EGTs rise and the engine is smooth but produces less power. If it runs rough, it normally points to a weak plug--sometimes CHT drops to nothing on one mag pointing to a plug that isn't firing.

Just because you don't see a runup check in the run up area, may not mean it wasn't done. Some folks are making multiple flights a day and may not do a runup before each. If someone isn't doing a mag. check at all, we'll probably be reading about them sometime--seesh!!

Best,

Dave

 

[Skip Miller]

If you lost a mag in flight, wouldn't you notice it?

I think many less-than-150-hour renters would not. And I have pulled that number out of the air.

The act of shutting down should not harm the mag.

So, if it ran fine at the start of the day, you ran it normaly, why would it be bad durning the day with out you knowing it?

True statements, but... You will never lose money betting on the lack of awareness of most people. Sadly, some of them are pilots. Tom, I bet you have made a lot of money over the years fixing problems caused by pilots who did not listen to their engines....

-Skip

 

[Ghery]

I was talking to my dad on the phone while riding in from ORD this afternoon and he was sorry we didn't get to fly. I told him that this sort of thing crops up just often enough to drive home the reasons we do all these checks before shoving the throttle forward to take off. Not the first time I've aborted a flight due to a plug or mag I couldn't clear and I'm sure it won't be the last.

Oh, and the plane had been flown over to the middle of the state and back the previous day. I don't know what his experience was with it, but he hadn't written anything in the log...

 

[tom.]

I'm curious what they find to be the cause of the squawk. Sooo many rental/club planes that get fouled plugs, especially in the summer, because folks aren't taught to agressively lean on the ground. Here in sunny, hot SoCal my partners and I have gone through the summer so far without a single rough/bad mag check, largely (or entirely) because we are all diligent about pulling out the red knob as soon as the post-start engine checks are done. When I was renting, I couldn't get 5 flights in without finding a rough mag at runup (usually, but not always, I could clear it with a lean 30sec-1min runup at ~2,000 RPM).

Here at sea level lots of people never lean it out. I've had a rough mag (drop within limits but higher than the other side) and been able to clear it with a full power runup at takeoff 100% of the time. By the way, I try to do a mag check at the completion of the flight.

Don't get me wrong, on a hot day, with a full boat, I might park it anyway if a rough mag is found. Remember, most pleasure flights are discretionary!

 

[GaryO]

Remember, most pleasure flights are discretionary!

Most???

 

[Maverick]

If you lost a mag in flight, wouldn't you notice it?

The act of shutting down should not harm the mag.

So, if it ran fine at the start of the day, you ran it normaly, why would it be bad durning the day with out you knowing it?

In my case I did not notice the in flight mag failure. Maybe it happened during my decent to land for refueling. The point is that it was dead and if I had not done the runup I may have discovered it during climb out. I'd rather know before take off.

The other point I was making is that there are pilots who feel one runup at the beginning of a day of flight activity is enough. To me that would imply that mag failures are due solely to gremlins screwing with the airplane at night while it's in the hangar. Faulty logic, things can go wrong at any time and I think it's more likely a problem will occur during use than while at rest. When it's a rental you just never know what the airplane has been through prior to your using it.

Jeannie

 

[Lawreston]

I see it all the time. Some people are crazy. When they have an accident it makes us all look bad and it seems like every time I pick up a newspaper I'm reading about a small plane going down.

I had a client who used to do general maintenance(cleaning, only) on his employer's twin. The owner had a string of very successful auto dealerships in ME, NH, and NY, and spent a lot of time flying from one city to the others to visit the businesses. On one such flight an engine failed and he died as a result of the crash.

Another of my flying friends owns a somewhat historic WACO(whose plane will be available as a model airplane kit sometime this year, rights having been sourced by the hobby/kit manufacturer). Anyway, the WACO owner told me that the auto dealers preflight routine was, "start it look at the fuel gauges, oil gauges, and take off." The NTSB investigation of the crash? "One engine was without oil. During flight, when the engine failed, pilot probably feathered the wrong engine, resulting in the flight into terrain." Gee, if Rene had only checked the dipsticks..........................................

HR

 

[Tom-D]

I think many less-than-150-hour renters would not. And I have pulled that number out of the air.


True statements, but... You will never lose money betting on the lack of awareness of most people. Sadly, some of them are pilots. Tom, I bet you have made a lot of money over the years fixing problems caused by pilots who did not listen to their engines....

-Skip

I was diging to see how many pilots here would venture a guess as to what causes most mag drops they see on a mag check.

I had a prime example here friday evening, A very pretty 182 was cracking and poping on run up, I could tell he was trying to burn it out by after several minutes it still popped and banged on one mag.

After he taxied back to the gas pumps and shut down I asked if I could help.

Upon questioning I find he is 2 hours out of a 50 hour oil change and 80 hours since a factory re-man. 2 rebuilt mags and new harnesses on a IO-520 STCed upgrade, (nice aircraft)

Inspection reveals all the bottom plug wires are loose and one is all but falling off.

Poor maintenance, and bad pilot operating habits are the cause of most every mag drop.

Lean properly, do the 50 hour plug cleanings, and I'll wager your mags drop problems go away.

 

[gismo]

I personally use one runup per start. If it flew in and the engine wasn't shut down, it should be good to go.

I DO lean some immediately after startup and after turning off the runway on landing. So far, so good. Only once had a rough mag and then it was only about a 50rpm difference.

I do pretty much the same, if I'm doing multiple landings on a flight, I generally don't do a mag check before each subsequent takeoff. I suppose that I'd do some kind of check (with the JPI you can tell a lot by switching to one mag at idle) prior to any takeoff that required max performance, but that's not a place I'd be likely to be doing multiple takeoffs. I can only think of one such situation which was a few weeks ago I discovered that the seat belt tail of my right seat passenger was hanging (and banging) outside the door right after departing from a pretty short runway on a hot day. I stayed in the pattern, landed, and did a mag check at fast idle on the taxi back to the departure end.

I don't believe there's any scientific basis for this though, I suspect that a mag or plug is about as likely to go bad during flight and landing as any other time.

OTOH, it has been my experience that with proper leaning on the Baron's IO-470's combined with fine wire plugs, ignition problems are pretty darn rare. I think I've only had one such occurance in the last several years.

 

[gismo]

If you lost a mag in flight, wouldn't you notice it?

Maybe, maybe not. When both mags are working properly and all plugs are firing, can you tell the difference between both and right only without EGT when running a C/S prop with the throttle wide open? I don't think I can.

The act of shutting down should not harm the mag.

True, although with impulse couplers there might be an opportunity for failure during shutdown or startup. Also the mag switch itself could fail when actuating it at shutdown or startup. Then again you'd have to be paying close attention to notice a failure of the switch when returning to both at the conclusion of a mag check. Also it's quite possible to foul a plug during the landing (BTDT).

 

[flyingcheesehead]

It always blows my mind when I am taxiing behind someone for takeoff, and that person calls their takeoff while on the roll towards the runway, then takes off. No checks of any kind.

This reminds me of two pilots. One was a lawyer with a 421 who NEVER did any sort of preflight. We (line guys) tried to keep him from killing himself by preflighting as much as we knew how when tugging his plane up front. (He never even went to his own hangar, always called for us to pull the plane out.) Luckily, the worst thing that's happened so far is an open baggage locker dropping engine blankets on Hampton Ave. shortly after takeoff. He's just lucky there wasn't a motorcyclist driving down there at the wrong time.

The other:

http://www.ntsb.gov/ntsb/brief.asp?ev_id=20020320X00367&key=1

Pitts, lost power shortly after takeoff and crashed into a nearby field. Pilot survived with some bumps, bruises and blood but nothing really major.

This is even worse than no runup: One of the news chopper pilots was there and is pretty sure (but not sure enough for the NTSB) that this plane was the one that DID do a runup, and the engine quit! So he started it up and took off anyway... Sheesh!

Hopefully Pilot #1 will get scared enough to get his act together without killing anyone. Last I heard, Pilot #2 hadn't bought another plane.

 

[flyingcheesehead]

I'm curious what they find to be the cause of the squawk. Sooo many rental/club planes that get fouled plugs, especially in the summer, because folks aren't taught to agressively lean on the ground. Here in sunny, hot SoCal my partners and I have gone through the summer so far without a single rough/bad mag check, largely (or entirely) because we are all diligent about pulling out the red knob as soon as the post-start engine checks are done. When I was renting, I couldn't get 5 flights in without finding a rough mag at runup (usually, but not always, I could clear it with a lean 30sec-1min runup at ~2,000 RPM).

One of my favorite club birds had what seemed like a mag problem - I'd always check the left mag first, then the right. The left mag seemed to drop a hair more than I'd really like it to, but then I'd check the right mag and it'd be fine and check the left again and it'd be fine too.

I squawked it, MO said they'd had some timing issues with that mag in the past, shop looked at it, "fixed" it. Next flight, still happening but always fixed itself. A few weeks later, it finally started hesitating a bit on go-arounds and missed approaches. I grounded the plane and got it back into the shop.

Turned out to be a bad carb. I don't know why the problem only manifested itself on the initial left mag check, but it's a good illustration why to not fly if the burn-off trick doesn't work.

 

[Dave Siciliano]

On a recent flight in the P-Baron, the left engine was running a little rough on one flight. Real noticable in a sustained climb. Then, after a bit, it just corrected itself. Have to believe it was crud on a plug or two that just burned off, but did show me it would be noticable if a plug or two wasn't firing right.



It was difficult to tell which side it was coming from; the JPI eliminated any doubt. Two plugs on one side had lower than normal CHT readings. 'Bout 30 minutes into the flight, all was well. The ground mag. check before the flight was fine.



Best,

Dave

 

[Tom-D]

The most common discrepancy I see causing a mag drops are a fouled plug, due to improper shut down procedures, second is a chafed lead due to improper clamping of the harness. Third (could be a cause of number one) no maintenance, plugs have not been out and cleaned since last annual, maybe not even then.

Very seldom do I see a problem with timing, or internal mag problems that will cause a mag drop. If I see internal mag problems I usually find some one has had the mag open, and FIXED IT.

When you shut down after you run the engine lean for 1 minute, lean properly in flight, do the maintenance required, mag drop problems do not appear.

Ignition switches are of the massive electrode type, they self clean by wipeing as they are turned on and off, and when they do fail it is to the open condition, that leaves a mag hot. NO MAG DROP.

Remember the AD on Bendix switches? It has the pilot do a check to see if the mag switch has failed, and will no longer ground the mag.

 

[Tom-D]

This ran great, but it was hard to start. The distriburator rotor was broken.

 

[Tom-D]

On a recent flight in the P-Baron, the left engine was running a little rough on one flight. Real noticable in a sustained climb. Then, after a bit, it just corrected itself. Have to believe it was crud on a plug or two that just burned off, but did show me it would be noticable if a plug or two wasn't firing right.



It was difficult to tell which side it was coming from; the JPI eliminated any doubt. Two plugs on one side had lower than normal CHT readings. 'Bout 30 minutes into the flight, all was well. The ground mag. check before the flight was fine.


Best,

Dave

Sounds to me like you loaded it up on taxi out.

 

[Len Lanetti]

If you lost a mag in flight, wouldn't you notice it?

The act of shutting down should not harm the mag.

So, if it ran fine at the start of the day, you ran it normaly, why would it be bad durning the day with out you knowing it?

Tom,

Would I notice the lose of a mag during cruise...I did once with a Tiger but it might be harder with a constant speed prop. For some reason increased CHT and decreased EGT comes to mind as a clue for an aircraft with a constant speed prop (also decreased MP but it is possible that a PIC would just bump up the throttle). I like have a CHT and EGT guage that is a little informative than the one that originally came with the plane.

Why would it go bad...fouling from lack of leaning, mechanical failure, failure of the ignition harness.

Len

P.S. Note I usually hate playing stump the dummy with Tom, Bruce, Marty, Ron & Ed.

LL

 

[Tom-D]

Maybe, maybe not. When both mags are working properly and all plugs are firing, can you tell the difference between both and right only without EGT when running a C/S prop with the throttle wide open? I don't think I can.

With both mags working properly, and all plugs fireing = NO MAG DROP, that is what I want to see.

True, although with impulse couplers there might be an opportunity for failure during shutdown or startup. .

And when it does it sheds parts into the accessory section of the engine, shortly after that it gets quite

Also the mag switch itself could fail when actuating it at shutdown or startup..

If a mag switch fails it fails to the open circuit, and you get a hot mag, no mag drop.

Also it's quite possible to foul a plug during the landing (BTDT).

99 times out of 100 that is when it will occur, combined with no leaning during the taxi in, and improper shut down procedures, causes what this thread is all about.

Mag drops causing missed flights.

 

[pete177]

This reminds me of two pilots. One was a lawyer with a 421 who NEVER did any sort of preflight. We (line guys) tried to keep him from killing himself by preflighting as much as we knew how when tugging his plane up front. (He never even went to his own hangar, always called for us to pull the plane out.) Luckily, the worst thing that's happened so far is an open baggage locker dropping engine blankets on Hampton Ave. shortly after takeoff. He's just lucky there wasn't a motorcyclist driving down there at the wrong time.

The other:

http://www.ntsb.gov/ntsb/brief.asp?ev_id=20020320X00367&key=1

Pitts, lost power shortly after takeoff and crashed into a nearby field. Pilot survived with some bumps, bruises and blood but nothing really major.

This is even worse than no runup: One of the news chopper pilots was there and is pretty sure (but not sure enough for the NTSB) that this plane was the one that DID do a runup, and the engine quit! So he started it up and took off anyway... Sheesh!

Hopefully Pilot #1 will get scared enough to get his act together without killing anyone. Last I heard, Pilot #2 hadn't bought another plane.

If your sure he's not doing things properly put a call in to the local faa office, maybe someone will come out or call to have a chat with him. If he thinks someone is watching him but doesnt know who it is it may give him the incentive to do things properly. Many people believe that the thing that gets them wont be discernable on a preflight. Either way, you just might be saving his life.
Oh, wait, you said he was a lawyer.....never mind.

 

[tom.]

Most???

Sometimes the weather is nice enough that it almost feels compulsory to go fly.

 

[GaryO]

Update

Sometimes the weather is nice enough that it almost feels compulsory to go fly.

Ahhh! That makes sense. I've been trying it imagine a scenario where a pleasure flight was compulsory.

Now if I can just get my boss to buy it ...

 

[poadeleted20]

If you lost a mag in flight, wouldn't you notice it?

On the occasion when that happened to me, yes, I did.

The act of shutting down should not harm the mag.

"Should"? Dunno. That's sort of a theoretical question.

So, if it ran fine at the start of the day, you ran it normaly, why would it be bad durning the day with out you knowing it?

Why? Dunno. But I have a couple of times shut down with everything seeming normal and had an ignition problem show up on the run-up on the next flight. So to my thinking, you gotta be dumber'n'a box'o'rocks not to do a mag check each time you get ready to take off (unless you're flying an engine that spins rather than bangs).

 

[poadeleted20]

If your sure he's not doing things properly put a call in to the local faa office, maybe someone will come out or call to have a chat with him.

One step short of that is to let the local Aviation Safety Counselor know about this. That keeps it off the legal books but gives someone a chance to talk to the guy before turning him over to the FSDO. If you don't know who your local ASC is, call the FSDO and ask the Aviation Safety Program Manager who the ASC is for your airport.

 

[John J]

I had a mag let go in cruise flight three years ago. I had completed the runup and no problems. The take off was normal and climb was fine. Everything was fine untill I was close to 2,500 feet. The engine went to a very rough state. I felt the engine was going to jump out of it's mounts. I went back to the airport pronto and set up to land on the closest runway. Long story short I had a recent annual, (less than 5 hours) and the left mag came loose on it's mounts and shifted it's timing. I did a quick check and flew in on the good one.

Lesson learned it can happen at anytime and all the emergency simulation training pays off big time when the engine gets rough.

John

 

[Tom-D]

I had a mag let go in cruise flight three years ago. I had completed the runup and no problems. The take off was normal and climb was fine. Everything was fine untill I was close to 2,500 feet. The engine went to a very rough state. I felt the engine was going to jump out of it's mounts. I went back to the airport pronto and set up to land on the closest runway. Long story short I had a recent annual, (less than 5 hours) and the left mag came loose on it's mounts and shifted it's timing. I did a quick check and flew in on the good one.

Lesson learned it can happen at anytime and all the emergency simulation training pays off big time when the engine gets rough.

John

One more for poor quality maintenance.

 

[gismo]

With both mags working properly, and all plugs fireing = NO MAG DROP, that is what I want to see.

You're not going to get a mag drop in cruise with a C/S prop, that was my point.

And when it does it sheds parts into the accessory section of the engine, shortly after that it gets quite

Quiet??? The paniced pilot's screams make up for the lack of engine noises.

If a mag switch fails it fails to the open circuit, and you get a hot mag, no mag drop.

I know you're right about that, at least most of the time, but there are ways for some mag switches to malfunction where one mag remains grounded. Quite unlikely though.

99 times out of 100 that is when it will occur, combined with no leaning during the taxi in, and improper shut down procedures, causes what this thread is all about.

Mag drops causing missed flights.

Yep. And if a plug gets lead fouled, chances are you will have to pull the plug. Carbon OTOH seems to be much easier to "burn off". BTW which do you recommend for attempting to clear a fouled plug:

1) Runnup RPM (typically around 1700 for opposed engines) and lean to peak EGT.

2) Full power with mixture set for takeoff.

3) Full power with mixture leaned (how much?).

4) Other.

IME #2 does the best job without risking the engine (as long as you can go full power without the plane moving).

 

[gismo]

So to my thinking, you gotta be dumber'n'a box'o'rocks not to do a mag check each time you get ready to take off (unless you're flying an engine that spins rather than bangs).

Or a Diesel.

 

[Tom-D]

Or a Diesel.

By the Way, I agree with Ron, It is stupid to fly with an engine that has not been tested in every way we can.

I hope we can someday certify an engine which has electronic ignition, such as the unison system.