Live mag check

pmanton

pmanton

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PoA Supporter
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Jun 7, 2008
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4,696
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Indian Hills Airpark Salome, AZ
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N1431A
Since I learned to fly in 54 I have been shouting "Clear". Never in all those years have I had someone yell "No" and run away from the front of the plane.

About that time, I learned to quickly switch the mags off and back on while at an idle before shutdown. Never did the plane keep running-----until a couple of days ago!

Wow what a wake up. A couple of years ago I bought a second plane. A 1959 Forney. It's a later version of the Ercoupe. They had used shielded wire left over from WW 2. They used a single ground point for both mags which was tied to the engine case. The ground had failed there.

I have done 2 annuals on this plane and didn't spot the lead about to part. I'm glad it happened to me, and not on someone else's plane that I had worked on.

I live on an airpark and my wife came out to help me put the plane away. I told her not to touch the prop since it was hot.
I then proceeded to turn the prop to put the tow bar on. CLICK went the impulse coupling !!!!:eek:

So keep shouting "Clear" and making those live mag checks. You never know when they'll pay off.

Paul
Salome, AZ.
 
Good post. I just want to add that, to me, yelling “clear prop” is only half the exercise. The other half should be a full sweep of the area to verify nobody’s around. The “clear prop” is just a way to get them to jump so I can spot them better before turning the key. Kids, dogs, cars, non aviation folks, etc don’t know what “clear prop” means.

It’s a pet peeve of mine that people start cranking the engine while the words are still coming out. What the hell good does that do other than tell someone what is about to kill them?
 
A lot of pilots don’t seem to understand what the purpose of ‘clear prop’ is for, but rather only do it out of pure routine. Instead of waiting a few seconds after the fact to allow for a reaction, they’ll start the engine right away. Totally useless if you’re going to do that.
 
Sometimes I've called "clear prop" and nobody around seems to notice. They don't even look over to see that the prop is indeed clear of anyone. So I've just bumped the starter, not enough to get through even one compression stroke, and that gets attention. I want people looking at the airplane so they'll holler if something I can't see--some kid or dog--is near it.

While we're at it, having dogs on an airport is insane if they're not tied up securely.
 
Dan Thomas said:
Sometimes I've called "clear prop" and nobody around seems to notice. They don't even look over to see that the prop is indeed clear of anyone. So I've just bumped the starter, not enough to get through even one compression stroke, and that gets attention. I want people looking at the airplane so they'll holler if something I can't see--some kid or dog--is near it.

While we're at it, having dogs on an airport is insane if they're not tied up securely.
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I live on an air park. Sometimes a dog wanders off.
 
Salty said:
I live on an air park. Sometimes a dog wanders off.
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They can get struck by a prop, or cause some sort of accident when they run out onto the runway when an airplane is taking off or in the landing rollout. Options for the pilot are limited.
A propstrike can mean a teardown, and the aircraft owner will want the dog owner to pony up for it.
 
I always viewed it as a habit that was meant more to make me look around before lighting the fire than to warn others.
 
Note that turning the key to off doesn't guarantee anything. I had one of those balky Bendix switches that would unground the mag after you remove the key.
 
Dan Thomas said:
They can get struck by a prop, or cause some sort of accident when they run out onto the runway when an airplane is taking off or in the landing rollout. Options for the pilot are limited.
A propstrike can mean a teardown, and the aircraft owner will want the dog owner to pony up for it.
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upload_2021-5-26_20-44-44.jpeg
 
Dan Thomas said:
They can get struck by a prop, or cause some sort of accident when they run out onto the runway when an airplane is taking off or in the landing rollout. Options for the pilot are limited.
A propstrike can mean a teardown, and the aircraft owner will want the dog owner to pony up for it.
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How would that cause a tear down?
 
Tarheelpilot said:
How would that cause a tear down?
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Sudden stoppage can crack crankshafts, accessory drive gears, and damage other stuff. Insurance companies don't like that. Lycoming has an AD on some of their engines, as it can cause partial failure of the crank gear drive pin.
https://rgl.faa.gov/Regulatory_and_...e5f8683a0a4686256e9b004bc295/$FILE/041014.pdf

Their definition of a propstrike includes "A sudden RPM drop while impacting water, tall grass, or similar yielding medium, where propeller damage is not normally incurred."

The AD calls for a partial teardown in that instance. Accessory cover has to come off, which in most cases means the engine has to come out of the airplane.

I had a crank break in flight due to a long-ago propstrike. In the old days mechanics would put a dial indicator on the crank flange and see if it was with runout specs, but cranks were breaking anyway. The distortion during a strike can be considerable and the crank bounces back, but a crack may have started.
 
Dan Thomas said:
They can get struck by a prop, or cause some sort of accident when they run out onto the runway when an airplane is taking off or in the landing rollout. Options for the pilot are limited.
A propstrike can mean a teardown, and the aircraft owner will want the dog owner to pony up for it.
Click to expand...

My personal observation about dogs is that their owners have become increasingly oblivious and considerably stupider in the last few years. There is also a manifestation of entitlement present, as there seems to be no place it isn't proper for their dog to be.
 
Country Flier said:
I think I'm the only one that when I hear a pilot yell "clear prop!" I turn, look to ensure their prop is clear, then give them a thumbs up. I don't think anyone ever does this back to me.
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I try to do it, but usually the engine is already running by the time I swing my head around......
 
Back to the OP's statement, I started in 1969 and yea, I feel kinda silly yelling "CLEAR PROP" when I know for a fact that I'm the only clown at the airport but I do it anyway. Kids and dogs aside though I've never climbed into the plane and then had some Bozo walk up to the prop and stand there with a dumb look on his face like he had no clue what was about to happen to him. To be honest, the ones that are already running are just as dangerous as the one you're about to crank over. But we err on the side of caution for a reason - because, as unlikely as it may seem, it has happened. Same reason we always treat a prop as if it's hot or pretend an empty gun is loaded. It's the one sure way to be safe.
 
Country Flier said:
when I hear a pilot yell "clear prop!" I turn, look to ensure their prop is clear, then give them a thumbs up
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I do this, too. And when I yell clear prop from that little toy window on the side of the Piper, I have already done a visual sweep of the area. Then, after yelling out of that small porthole too small for any air molecules to get in the cabin, I do another visual sweep of the area. Amazing how many people yell clear as they are already turning over the engine.... or how many don't yell clear at all.

Tarheelpilot said:
Chuck Norris might have a dog that would cause a sudden stoppage
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Chuck Norris doesn't have to comply with any ADs... he just beats the engine into submission until it complies with the AD by itself.
A roundhouse kick from Chuck Norris can put a run-out IO-360-C1C with 4,000 hours back to better than factory specs.
 
Deelee said:
I do this, too. And when I yell clear prop from that little toy window on the side of the Piper, I have already done a visual sweep of the area. Then, after yelling out of that small porthole too small for any air molecules to get in the cabin, I do another visual sweep of the area. Amazing how many people yell clear as they are already turning over the engine.... or how many don't yell clear at all.



Chuck Norris doesn't have to comply with any ADs... he just beats the engine into submission until it complies with the AD by itself.
A roundhouse kick from Chuck Norris can put a run-out IO-360-C1C with 4,000 hours back to better than factory specs.
Click to expand...

Bold of you to assume Chuck Norris gives a damn about the engine. He simply throws the plane up to altitude, jumps into the cockpit, and roundhouse kicks the prop now and then to keep it spinning.

But seriously, having trained at an airport where rich distracted parents sometimes let their kids run around the ramp untethered, I learned very early on to always take the "clear prop" routine very seriously. Once had a child(whom I saw with his parents maybe 100ft away seconds before) run right up to the front of the plane to where the cowling blocked my view of him. Luckily I wasn't quite ready to start yet, but if it was 20 seconds later and I didn't see him run up, it could've been horrific. Always keep your head on a swivel both in the plane and walking around the ramp.
 
I saw a dog once with one eye, SD. The airport guy said he was hit by a prop. I put more into keeping high S.A.. than really yelling ‘clear prop’, though I do mumble a bit to keep with the program.
 
Juliet Hotel said:
Dogs are made out of meat, not cinder block. I doubt RPM would move so much as a single RCH if dog when the prop.
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I would think that a large canine would have a greater influence on RPM than "tall grass".

From the document:
"A sudden RPM drop while impacting water, tall grass, or similar yielding medium, where propeller damage is not normally incurred."
 
donjohnston said:
I would think that a large canine would have a greater influence on RPM than "tall grass".

From the document:
"A sudden RPM drop while impacting water, tall grass, or similar yielding medium, where propeller damage is not normally incurred."
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Well I've heard of several cases of people coming into contact with spinning props, some fatal, others not. I've never heard of the engine in question having to get a teardown afterward. I can't say it hasn't happened, but I've never heard of it. I would think a person is at least as 'hard' as a dog as far as a prop strike goes.
 
Juliet Hotel said:
Well I've heard of several cases of people coming into contact with spinning props, some fatal, others not. I've never heard of the engine in question having to get a teardown afterward. I can't say it hasn't happened, but I've never heard of it. I would think a person is at least as 'hard' as a dog as far as a prop strike goes.
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I was not speaking to whether a teardown and inspection is needed in such an event. That's for other people with more knowledge than I. But if there's an AD which says that an inspection is required if there's a prop strike and it includes the definition of a prop strike, then that seems pretty straightforward to me.

Nowhere in the AD does it state "only if you've heard of this happening before".
 
Juliet Hotel said:
Dogs are made out of meat, not cinder block. I doubt RPM would move so much as a single RCH if dog when the prop.
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Juliet Hotel said:
Well I've heard of several cases of people coming into contact with spinning props, some fatal, others not. I've never heard of the engine in question having to get a teardown afterward. I can't say it hasn't happened, but I've never heard of it. I would think a person is at least as 'hard' as a dog as far as a prop strike goes.
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You might never have heard of it, but we in the aircraft maintenance industry have heard of it plenty. Your experience is not the determinative factor here; it's the dismal history of inflight engine structural failures after propstrikes that determines the need for inspection.

I know an owner that didn't see the plastic traffic cone down in front of the airplane, put there by the fueller and not removed before startup. The prop caught it. It bent a prop blade. That was enough to force a teardown. A cocker spaniel would do a lot more damage than a three-pound soft plastic traffic cone.

No mechanic wants to tell an owner that "it will be OK. No big deal" after any sort of propstrike. The owner takes off, the crankshaft or something else breaks, and he sues the mechanic. That's the climate we operate in now. In the old days they used to just let it go, but failed cranks and other stuff were common. I had a friend have a crank fail in flight. So did I. Another friend, who had his own shop, had the front end of a crank that had broken on takeoff on display in his office. In the flight school we had a couple of taxiing accidents that bent the prop while the engine was at idle; the cranks in both those engines were cracked. MY experience is a lot different from yours.
 
donjohnston said:
Nowhere in the AD does it state "only if you've heard of this happening before".
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That there. ADs are based on actual failures, or on conditions that are likely to lead to failure. There is no shortage of failures of cranks, con rods, accessory drive gearing, magnetos and a lot of other stuff that doesn't like being subjected to sharp mechanical shock. These things are not jackhammers; they are devices designed to move air. Not pavement, not dogs, not people, not water. Air, and only air.
 
donjohnston said:
I was not speaking to whether a teardown and inspection is needed in such an event. That's for other people with more knowledge than I. But if there's an AD which says that an inspection is required if there's a prop strike and it includes the definition of a prop strike, then that seems pretty straightforward to me.

Nowhere in the AD does it state "only if you've heard of this happening before".
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You're correct, the AD does not say only if you're heard of this before. Instead the AD says "A sudden RPM drop while impacting water, tall grass, or similar yielding medium, where propeller damage is not normally incurred." So I'm therefore assuming you believe having the prop come into contact with a dog (or a part of a person) will cause a drop in RPM that you would be able to reliably detect. I do not share that opinion. I don't think you'd see any kind RPM drop in that scenario.
 
Juliet Hotel said:
You're correct, the AD does not say only if you're heard of this before. Instead the AD says "A sudden RPM drop while impacting water, tall grass, or similar yielding medium, where propeller damage is not normally incurred." So I'm therefore assuming you believe having the prop come into contact with a dog (or a part of a person) will cause a drop in RPM that you would be able to reliably detect. I do not share that opinion. I don't think you'd see any kind RPM drop in that scenario.
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I hear a new episode of Mythbusters is coming out soon…
 
Lachlan said:
I hear a new episode of Mythbusters is coming out soon…
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A moose? A cow? A big deer? Sure, you'll probably be able to detect an RPM drop if you hit it. But a dog? Unless we're talking about a breed of dog that's the size of a small horse, I'd expect the blood splatter would probably be your only indication that you'd hit anything. Unless I'm reading it wrong, if the RPM doesn't drop, no inspection is required.
 
Juliet Hotel said:
A moose? A cow? A big deer? Sure, you'll probably be able to detect an RPM drop if you hit it. But a dog? Unless we're talking about a breed of dog that's the size of a small horse, I'd expect the blood splatter would probably be your only indication that you'd hit anything. Unless I'm reading it wrong, if the RPM doesn't drop, no inspection is required.
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You are entitled to your opinions. In the face of the experience of experienced mechanics and engine builders.
 
Dan Thomas said:
You are entitled to your opinions. In the face of the experience of experienced mechanics and engine builders.
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Not arguing that an inspection wouldn't be a good idea, only that it would not be required if the event in question did not cause the RPM to change.
 
Juliet Hotel said:
Not arguing that an inspection wouldn't be a good idea, only that it would not be required if the event in question did not cause the RPM to change.
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A propeller striking an object with 800 times the density of air is going to change the RPM.
 
The RPM will drop, all right, but it might immediately recover... it could be too fast to notice, but how fast the RPM drops is more important than the actual RPM it drops to.
 
Juliet Hotel said:
... I'd expect the blood splatter would probably be your only indication that you'd hit anything...
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What are you basing these expectations on? Obviously you've never hit a dog with your prop so they're not based on experience.
 
Silvaire said:
What are you basing these expectations on? Obviously you've never hit a dog with your prop so they're not based on experience.
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One of the guys at my airport hit a deer two years ago, chopped off its head, did not get an overhaul. Was it smart? Probably not. Did he have enough insurance? Probably not, and that may have made the decision for him. I'll post back if his plane falls out of the sky in the future.
 
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