Aircraft: Piper Cherokee. Injuries: None. Location: Allentown, Pa. Aircraft damage: Substantial.
What reportedly happened: During the initial climb on an instructional flight, the engine lost partial power. The CFI performed a forced landing into a cornfield.
During a subsequent test-run of the engine, the engine would lose all power if only the right magneto was selected.
Laboratory examination of the right magneto revealed that seven teeth from its drive gear were fractured and exhibited single-sided bending fatigue, consistent with applied force in one direction over a period of time.
At the time of the accident, the engine had accumulated about 2,300 hours since overhaul, which had been completed about seven years prior. The magnetos had not been replaced or serviced since they were installed during engine overhaul.
The engine manufacturer recommended overhauling the engine every 2,000 hours or 12 years, which would have included replacing the magnetos with new or overhauled units. Additionally, a service bulletin issued by the magneto manufacturer recommended inspecting the magnetos every 500 hours; however, there was no evidence that an inspection was ever performed during the 2,300-hour life of the failed magneto.
Probable cause: The failure to perform magneto inspections per the manufacturer’s recommendations and failure to comply with the engine manufacturer’s recommended time interval for engine overhaul, which resulted in defects in the magnetos going undetected and the failure of the right magneto during initial climb.
NTSB Identification: ERA13LA025
This October 2012 accident report is are provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
Indeed from 200 feet it should have been safely possible to return to the runway. The pilot seems to have caused the off airport landing not the (single) Mag. failure. The good thing they walked away, likely poor choice of landing site , Great job of landing the airplane.
Anyway, most of your planes have bad nylon teeth, so it’s best to do your pre-takeoff mag check, and remember you have another mag, if one stops turning, due to missing teeth.
If you have an engine fire, the nylon fails, too, becoming brittle and burnt.
I’m posting a second time, just to check the “follow-up” box.
FBO maintainece is actually the cause of the mags nylon gear failure, not the cure!
After the E-gap is set, the mag is mounted on the engine, and the external timing must be set. The nylon gears must be locked during the mounting, so that the internal E-gap is not lost. When the locking tool is in place, sometimes people inadvertently turn the prop, stressing or even stripping the nylon teeth. The teeth can flex, and re-bound slightly, so that the mag can work, but it is degraded, and the teeth can fail at a later time. I believe in self-maintenance by the pilot owner-operator. My own plane fires at 50,000 Volts, and no compromised nylon teeth on the mags!
If this report is a correct interpretation of the NTSB findings then the blame should be on the shoulders of the operator, the CFI for the off airport landing as what has been commented on by Brett.
In addition the TBO had nothing to do with the mag failure. I’d be willing to bet the engine itself was probably within specs!
You could fault the owner or AP who worked on the aircraft for not doing a 500 hour inspection of the mags, however this failure could have happened at any time. The fact is it appears the mag lasted almost 2300 hours.
I could speculate although a 500 hour inspection didn’t appear to be done, I would be willing to bet the mags were opened up and points checked, gears visually checked, timing set, cap cleaned. Unless the gears have failed there would not be any evidence of such and it can happen in a very short period of time.
The engine problem was the result of a mag failure. The accident/ damage was the result of the PIC’s failure.
From reading the entire NTSB report it seems that the mags had never been opened and were incorrectly manufactured. Lucky it reached the hours it did. Owner failure to properly maintain the aircraft for one.
The FAA always has to blame someone for an accident. I’m sure they went after the maintenance persons who did maintenance on this aircraft. No reason the airplane would not have flown on one mag. The real blame for this accident and others like it should be laid on the shoulders of the FAA. There are great new ignition sources that are available, but the FAA in its “wisdom” makes it so hard and expensive for manufacturers to make changes to their products. Magnetos are old farm tractor technology. Even though they are generally dependable, I wonder why the automobile, outboard motor, and even the lawn mower manufacturers don’t use them on their products?.
I second what Brett said particularly in light of the test run of the engine after the fact. While pushing mags for 2300 hours does seem somewhat long in the tooth the odds of both mags going belly up at the very same time is so remote that as a practical matter the 500 hour inspection is really not that critical. Doing a proper mag check before take off is the key and don’t put the aircraft somewhere other than on an airport unless it is necessary.
Sorry, but I would retitle this article “CFI Scraps Rented Cherokee”. I thought one of the BIG purposes of having dual ignition was to be able to continue flight to a safe landing on one mag.
If the CFI cycled the ignition switch, selected the bad mag and believed the engine was toast, maybe the emergency landing was the result of a reasonable decision-making process. However, I assume a Cherokee will maintain a reasonable altitude on one mag which should have allowed a trip around the pattern to a normal landing. YMMV.
I agree with the title change. Yes there was a maintenance error but reading the full narrative discloses that the Left Magneto was also put together incorrectly but it was still working. One must wonder if the CFI was low time and did not know how to properly respond. More importantly was a mag check actually done during preflight runup? I find it doubtful that a magneto would break in the minute or two it takes from completion of a check to initiating takeoff. Possible but not very likely.