Mags left on accident

[pelmet]

If you are going to re-position a prop a bit, why not just move it backwards unless there is a problem doing this with a specific engine. If you need to pull the prop through in the direction of rotation such as when looking for a hydraulic lock on certain engine types or another reason, then make sure the park brake is on(and it works) or aircraft chocked(both main gear if park brake is not on), or tied down securely. Then it takes a very short time to check mags off, fuel off, throttle closed and mixture lean.

Occurrence No. : A13W0159 Occurrence Type: ACCIDENT

Class : CLASS 5 Reportable Type:

Date : 16-10-2013 Time : 10:00 MDT

Region of Responsibility : WESTERN

Location : WHITEHORSE, 8 NM N, YUKON


Aircraft Information:

Registration : C-GBPO Operator :

Manufacturer : CESSNA Operator Type: PRIVATE

Model : U206 G CARs Info:

Injuries: Fatal : 0 Serious : 0 Minor : 0 None : 1 Unknown : 0

Occurrence Summary :

A13W0159: The privately operated Cessna U206F, C-GBPO, was having the prop turned over by hand due to the cold temperature. The mags had inadvertently been left on and the engine started with no one at the controls. The pilot attempted to get in and control the aircraft but was not able. The aircraft ran out of control into trees and down an embankment where it came to rest. There was substantial damage to the wings, propellor and the nose gear collapsed.

[Bobby868]

The assumption is that the mags were left on by accident. . . That's not the assumption I would come to. Wouldn't be the first time a pilot had a dead / low battery, tried to hand prop the plane and it started and got away on the pilot.

[Liquid Charlie]

Then it takes a very short time to check mags off, fuel off, throttle closed and mixture lean.

mixture off

Pretty basic airmanship for small aeroplanes -- this aeroplane was obviously set for engine start with no throttle friction set

[pelmet]

The assumption is that the mags were left on by accident. . . That's not the assumption I would come to. Wouldn't be the first time a pilot had a dead / low battery, tried to hand prop the plane and it started and got away on the pilot.

Actually....the assumption is always that the mags are on regardless of switch position. That is why...as posted initially.....If you are going to re-position a prop a bit, why not just move it backwards unless there is a problem doing this with a specific engine. If you need to pull the prop through in the direction of rotation such as when looking for a hydraulic lock on certain engine types or another reason, then make sure the park brake is on(and it works) or aircraft chocked(both main gear if park brake is not on), or tied down securely. Then it takes a very short time to check mags off, fuel off, throttle closed and mixture lean.

Friction tight is a good additional idea as subsequently posted.

[oldtimer]

Some mechanics caution against rotating the engine in the opposite direction of normal rotation in the belief that the brushes in the generator/alternator will be damaged.
I remember years ago that a chap was looking to purchase a Piper Super Cub which sat unused in a hangar for about 6 monthe. To check compression, he pulled the prop through a couple of times and the engine started. Scared the crap out of him because he was fat enough that the prop hit his beer belly and he was afraid it would spill his beer. Just kidding but the prop did hit his protruding belly, doing no damage.

[KISS_MY_TCAS]

Similar to alternator brushes, you can also potentially damage the vacuum pump by forcing the vanes to travel in the direction opposite to normal rotation.

I had a T182 in idle cut off fire on me once pulling a prop through with the mags left on when the impulse coupling snapped. I was complacent, haven't pulled a prop through without looking at the magneto position ever since.

[pelmet]

Similar to alternator brushes, you can also potentially damage the vacuum pump by forcing the vanes to travel in the direction opposite to normal rotation.

I had a T182 in idle cut off fire on me once pulling a prop through with the mags left on when the impulse coupling snapped. I was complacent, haven't pulled a prop through without looking at the magneto position ever since.

Could be true. I knew that would come up and that is why I made sure to say....."If you are going to re-position a prop a bit, why not just move it backwards unless there is a problem doing this with a specific engine".

I do fly aircraft with no alternators or vacuum pumps.

That being said, I'm not sure how much damage would be caused by a small backward movement on a 182 type aircraft such as to remove a cowl plug, but if rotating forward.....I suggest performing the initially posted actions first.

Just looking at the mag switch prior to pulling through in the forward direction of rotation is not enough.

[PilotDAR]

These accidents are obviously never good, and this sounds like it could have been much worse in many ways. A pilot now has a first hand shock as to why to do everything right. We are well reminded to also do everything right.

I have had several shocks while hand starting planes, with the worst being a confirmation from the pilot occupying the seat, that the mags were off. It started as I pulled it through, and my angry glare at him as I eyed him through the prop disc was replied by him holding up the keys, which he had removed from the ignition switch of the running engine.

There are just so many ways to get in trouble doing this, at least make sure the plane cannot move!

A 206 might have a three blade prop. That next blade is there alarmingly sooner than hand propping a two blade.

Very worn alternator brushes and vacuum pump vanes are subject to damage rotating backward, but if they are damaged, they were just about done anyway. They are not a reason to not rotate backward.

[Heliian]

It is good practice to never turn the blades backwards for many reasons and to always treat the piston engine as if it was ready to fire. This incident sounds like a failed start attempt, wouldn't be the first, I remember one on a float equipped cessna where the plane blasted across the lake and into the trees leaving the pilot to watch helplessly as he was stranded on the shore.

[DonutHole]

I believe that particular ac had a starter which could be damaged if rotated backwards...

[iflyforpie]

No, you can't damage an engine by rotating it backwards unless it says so in the manual. MAF turns their 206 engines backwards as SOP for every preflight with no known problems. Vacuum pumps that fail by catching a vane on the housing full of chatter marks were going to fail anyways a few hours later. For the geared sky tech starters, you just need to be carful that you don't turn it too fast or overload the starter drive.

[PilotDAR]

I believe that particular ac had a starter which could be damaged if rotated backwards

That is entirely possible. Some starter drive, and starter motor combinations will not allow the engine to be manually turn backward. If this is the case, you just won't be able to. Trying won't hurt it. But yes, if it necessary to reposition a blade, forward will be the only way to go. Then, yes, all cautions apply....

[Liquid Charlie]

OK -- the one thing that confuses me -- well setting dementia aside -- why would anyone pull a prop through by hand if the intention were not to hand spank it in the first place -- is this one of those urban legends that has become SOP because someone had a dream -- back in the day when I was falling off floats or sitting under an engine tent blowpotting we never pulled and engine through by hand - in fact the company frowned on it and would not allow it on the round engines -- a "size 3 hat and an 18 neck" was far more likely to cause damage than rolling through a few blades on the starter -- flat engines we just started --

round engines I always started in idle cutoff as I did as well for warm flat engines -- but it's been a very long time so things change and time marches on

[oldtimer]

L C Where did you come up with that expression Size 3 cap, size 18 neck? I remember the first time I ever heard that expression was from a pilot with Chuipka Airways/Calm Air in Lynn Lake in the late 60's.
It is one expression I have copied and used ever since.

[PilotDAR]

If I must start a very cold engine, which is ill advised, but sometimes you gotta do it, I may decide to pull it through by hand, with a prime. The purpose will be to get the stiff oil in the engine moving, and circulating a little bit. If the engine has primers to each cylinder, or good induction priming, the prime charge can be drawn into the cylinders, and act to thin the oil to lessen the starter torque required to start it. A primed engine which pulls through more easily, will start with less starter load, and fewer turns. Thus, a successful normal battery start is much more likely, and safer.

But, this is not standard flying club apron technique. That should be proper preheating, and external power starts if required and possible. These techniques are when you're stuck somewhere in the back country, and you're trying to carefully prevent things getting worse and being stranded. At those times, I'm thinking Swiss cheese holes lining up already so I will sure be tying down, chocking, and any other safety actions I can apply.

[Liquid Charlie]

--- Red Lake -- about in the same time frame --

[Doc]

The rule USED TO BE treat every prop as if the mags were on. Has this changed? Treat every gun as if it's loaded....for the same reason.
Treat every beer glass, as empty.

[Maynard]

I flew the 207 which i believe is the same as the 206, IO520? cant remember....I can remember never turning the engine by hand...what i don't get, if they were turning over by hand because of the cold weather, why not use the starter with the Mix I/CO....? A good battery will pull through enough blades rather than doing it by hand. Pretty easy engine to start hot or cold...

[pelmet]

I'm thinking Swiss cheese holes lining up already so I will sure be tying down, chocking, and any other safety actions I can apply.

If it is too big a deal to tie down, set the brake and get chocks.....at least have throttle closed with tension set and mixture lean, that will solve most of your runaway problem if the engine starts.

[PilotDAR]

that will solve most of your runaway problem if the engine starts.

Generally, yes. However, there is also a regulatory requirement, and it does say, qualified person at the controls, or restrained from forward motion. So control positions are only a part of a solution.

[pelmet]

that will solve most of your runaway problem if the engine starts.

Generally, yes. However, there is also a regulatory requirement, and it does say, qualified person at the controls, or restrained from forward motion. So control positions are only a part of a solution.

The thread is about repositioning or pulling a prop through for reasons other than intending to start the engine which is what happened in the case of the accident. I'm not aware of any regulatory requirement to have a qualified person at the controls for this activity.

[ragbagflyer]

Why is there no CADORS file for this occurrence? It looks like the OP is a TSB report.

[Maynard]

Forgive me if I'm being ignorant, but assuming the aircraft was shut down normally (mixture cut off), how would one turn the propeller blades and get a start up with no fuel? Even if it came to life on fumes, it would surely stop before driving into the trees...

The thread is about repositioning or pulling a prop through for reasons other than intending to start the engine

[ragbagflyer]

Maybe the aircraft needed some serious repair work.

[PilotDAR]

Forgive me if I'm being ignorant, but assuming the aircraft was shut down normally (mixture cut off), how would one turn the propeller blades and get a start up with no fuel? Even if it came to life on fumes, it would surely stop before driving into the trees...
PilotDAR wrote:
The thread is about repositioning or pulling a prop through for reasons other than intending to start the engine

I agree with the observation about the mixture being set to idle cutoff.

That quote is really attributed to someone else. I don't know why the prop was being pulled through, but it sure seems odd if that was being done with the mixture set rich, but no intent to start the engine. But, odd things happen, I guess....