After completing a personal flight with his wife, the private pilot secured the Cessna 182’s engine by placing the mixture control in the idle cut-off position.
Based on physical evidence observed after the accident, he likely moved the ignition switch toward the off position and removed the key.
The pilot’s wife indicated that, after they performed local errands and returned to the airport, the pilot was performing his preflight inspection of the airplane with the ignition key in his pocket.
Although security video at the airport in Cleveland, Tennessee, did not capture the accident sequence and the pilot’s wife, who was by the airplane’s right cabin door, did not see her husband move the propeller, she heard the propeller move and the engine starting or trying to start.
The pilot likely slightly moved the propeller and the engine briefly started. The propeller then rotated and fatally injured the pilot.
The engine did not continue operating, and the propeller stopped rotating.
Post-accident examination of the 42-year-old ignition switch revealed that it appeared to be in the off position when observed visually from the pilot’s seat, but its actual selected position was more toward the right magneto position.
The switch and key were determined to be slightly misaligned with the instrument panel placard markings.
On- and off-airframe operational testing of the ignition switch in the as-found position revealed the right magneto was hot, or not grounded.
In addition, examination of the cut surfaces of the key notches revealed relatively smooth and reflective surface features consistent with a worn surface on the flank of the notch adjacent to the key retention ridge and on the tip end of the shank opposite the notched side.
Examination of the key cylinder revealed an area with a smooth and reflective surface consistent with wear on the lower side of the key slot. The location and shape of the worn area was consistent with wear contact with the tip of the key as it was inserted and removed.
The key could be removed from the switch in any of the five positions due to the wear of the switch’s internal components, contrary to its intended function that would retain the key in any position except the off position.
Although the switch manufacturer tested all new switches to ensure this functionality when new, that test is not specified to be performed at any time as part of any inspection or checklist by the switch manufacturer, airframe manufacturer, or Title 14 Code of Federal Regulations Part 43 Appendix D.
Although the mechanic who performed the last annual inspection reported the key-to-switch integrity was satisfactory with no discrepancies, the worn condition of the ignition switch likely existed at the time of the annual inspection, which was about 31 flight hours before the accident flight.
Additionally, during the annual inspection when the mechanic installed the ignition switch after repairs, he failed to properly align the switch positions with the marks on the instrument panel placard.
Probable cause: The undetected wear of the ignition switch and key, which allowed removal of the key from an intermediate position and subsequently led to an unintended engine start-up. Contributing to the undetected wear of the 42-year-old ignition switch was the lack of guidance by the switch manufacturer and airframe manufacturer for procedures to detect lack of integrity between the ignition key and switch.
NTSB Identification: ERA18LA199
This July 2018 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
Hmm for some reason some pilots are missing this failure mode. This one has nothing to do with post shutdown mag checks. He may have done that and it would have been fine. The failure here is the key and switch were worn such that the key could be removed while in the right mag position. It is not supposed to be removable except and only when in the Off position. So, the presumed failure path is the pilot was moving the switch to off and the key extracted while in the right mag position. The pilot intended it to be in the off position and thought it was since the key came out. The check for this is to try to remove your key in all positions of the switch. If it comes out in other than off then you have a worn switch/key and you have set yourself up for a hazard that should not be there.
One unsung advantage of the Rotax 912/914 engines (and probably the other ones from them is well) is that it cannot start when the prop is rotated by hand. Each ignition is powered by a single coil on the alternator stator and it takes ~220 engine rpm to generate enough power for a spark. It’s an especially important feature considering there is no mixture control, hence no way to starve the engine of fuel for shutdown; shutting down with the key leaves the cylinders still primed and to fire. Also, backward hand-rotation of the prop is a big no-no. Both of these factors pretty much demand elimination any possibility of hand-prop starting to achieve a reasonable level of safety.
I am a long-time mechanic plenty experience with impulse couplings.
I wholeheartedly agree if it is ready to trip it will fire one cylinder and any fuel in it moving the prop.
Watching videos on YouTube of hand propping gives me the heebie-jeebies every time. If the engine doesn’t start on the first pull. The pilot repositions the prop by hand for the next pull WITH A HOT MAG!
Don’t you run a mag check during your engine run-up just before take off?
If you run a mag check during your engine run-up and you DON”T see a change in RPM when switching from BOTH to either L or R you have a hot mag, or possibly some other problem.
Switching the ignition to off with the engine running, can result in a backfire, which can damage your exhaust. If you’ve been a CFI for any time at all, you’ve seen a student do exactly this, you know what i mean.
The same goes for Carburetor Heat, and the mixture, if you put on carb heat, or lean the mixture, and don’t see some RPM drop, question whether it’s working. If you move a control, and do not observe a response, it’s time to ask questions.
That’s the very definition of a bad day
I never rotate the prop “forward” if I feel the need to reposition it.
Which I try to avoid.
And I almost always turn the mag switch to the OFF position very briefly at shut down to make sure it is working.
Of course like a Covid-19 test or an annual inspection sign off , it isn’t any good right after do it.
I always treat the thing as if it is gonna start.
I have a 1968 Piper Cherokee with Bendix mags. For years now we have done AD 76-07-12, which requires a key check at every annual as a recurring AD. This did not save us from having the switch go bad in between annuals. In this case my partner was refueling with the key out of the ignition. He switched on the Master switch to check the time on our electronic tachometer. The engine started cranking vigorously causing the line attendant to quickly panic and run. The engine did not start, but could have and the prop was dangerous just cranking. Like a gun that always needs to be treated as loaded the propeller needs to be considered hot at all times and the Master switch needs to be switched on after the propeller is cleared not before.
The new ignition switch I bought was the same as the old one so why hasn’t anybody redesigned that ignition switch?
Wow, this is a real revelation for me. I’ve been a licensed pilot and CFI for a very long time and had never been made aware of the need for a post flight mag check but I can certainly see the need for it for older airplanes [and let’s face it, most of them are older these days].
This is something for which the FAA should get the word out to ALL pilots because it could happen to anyone. When putting the airplane back in the hangar, we move the prop without giving any thought to the possibility that one or both mags could still be hot.
It’s a terrible tragedy this pilot had to learn the lesson the hard way but we can all benefit from the knowledge gleaned from this accident.
Lots of focus on the hot mag. Yes, mags are EXTREMELY dangerous when a p-lead problem or a ignition switch problem removes the ground. But, wasn’t there a serious maintenance failure in this? Yes, the switch was 42 years old. Yes, the switch was worn and the key could be removed from any position. And (oh by the way) it was recently inspected, the A&P removed the switch, then replaced it misaligned with the markings.
According to the accident report in the article, “…the mechanic who performed the last annual inspection reported the key-to-switch integrity was satisfactory with no discrepancies, the worn condition of the ignition switch likely existed at the time of the annual inspection, which was about 31 flight hours before the accident flight.”
The report goes on to say that “…, during the annual inspection when the mechanic installed the ignition switch after repairs, he failed to properly align the switch positions with the marks on the instrument panel placard.”
Oops!!
Wouldn’t a worn ignition switch that failed to ground the mags be a “safety of flight” issue AND non-conforming to the TCDS? The misaligned ignition switch would likely be non-compliant. Aircraft must be in compliance with TWO things to be ‘airworthy’. First, compliant with the TCDS + ADs + STCs, etc. And second, be “safe to fly”. In this accident, neither was true.
The root cause to this fatal mishap appears to me to be a maintenance failure. Contributing to the accident was the inadvertent movement of a hot prop.
We had an airplane in the fleet that developed this same problem. The key would slide out from any position. It made me realize that having the key in my pocket or seeing it on the glareshield did not mean the mags were grounded as the key could have come out from the both, L, or R position. Therefore the important check is to visually confirm that the key slot itself is in the off position – seeing the key on the glareshield is not enough. I was not aware that the mechanic had to align the key position with the placard and have never seen, that I know, any alignment issue with that but appreciate that information going forward.
I don’t see how a mag check would have helped this particular problem. After a mag check, the key is normally returned to both and the mixture pulled. Then returning to the ignition is where the hazard exists. If it is one of those worn out switches and the pilot applies even the tiniest amount of pulling force with the fingertip on the key as it is turned toward the off position, the key can slip out prematurely but the pilot most likely will assume it had to have traveled to the off position. What is needed is to confirm that the key has rotated three full positions from both which can be done by the feel of three clicks, usually it is heard, and visually monitoring. Then pull the key out, and visually confirm the key slot is in the off position.
Also when turning a prop, never ever have any part of your body in the path of the propeller.
My engine will not start if the mixture is closed and the throttle pulled back (fuel injected) which is how it is set after each flight. Certainly the engine won’t start unless this guy rotated the prop more than just a little bump. This story is filled with inconsistency.
An engine can start with “just a little bump”,all that is needed is to trip the impulse coupling on the mag to make the spark. If the compression cylinder is at,or close,TDC the spark WILL ignite any fuel charge in that cylinder. This can be from something as simple as a leaking primer. With a Shower of spark or battery ignition again with the cylinder properly set,only enough movement is needed to trigger the ignition. The engine will fire and rotate whichever direction is predicated by the timing at that point ,BTDC(kick-back)or ATDC normal rotation.
A high use aircraft with a crew that is in a hurry is a prime set-up for this. Watch a busy flight school or freight operation. The mixture is pulled the engine begins to die and the mags are switched off. With any fuel left in the intake or cylinder this can happen.
Rotating the engine backwards will prevent the impulse from tripping,it is very hard on dry vacuum pumps however.
As an AGI, I taught exactly this for 11 years and to something like 4,000 students. Every time we got a new hotshot CFI (and we had a lot of them come and go), they’d come to me, put their hands on their hips, and ask what the heck all this nonsense was about, why are you even bothering to check the mags when you’re finished flying?
I’d explain it to them slowly, patiently, and with words of one syllable . . . and most of the time you could see the light come on. They were amazed – “Wow! Nobody ever taught me that!”
The owner of the flight school once got the same discussion. Same response, and he had thousands of hours in all kinds of airplanes, he’d never heard of this before.
So, I see 2 problems;
1- Did this pilot ever do a mags ‘off’ check before shutdown ? If he did, he’d have seen that one mag was still ‘hot’.
2- If you need to move a prop, turn it backward. The mags won’t fire then.
He apparently never did either…sad.
As it is said, always assume the mags are hot no matter what, and always treat the prop like it’s a loaded gun. Very unfortunate accident.. the stars just went out of alignment for a few seconds.