Magneto failure shortly after takeoff forced pilot of small aircraft to return land.

Attributes
ACN	138950
Time
Date	199003
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : roc
State Reference	NY
Altitude	agl bound lower : 400 agl bound upper : 400
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : roc tower : ord
Operator	general aviation : personal
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Fixed Gear
Flight Phase	climbout : initial climbout : takeoff landing other
Flight Plan	None
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : private
Experience	flight time last 90 days : 5 flight time total : 209 flight time type : 105
ASRS Report	138950
Person 2
Affiliation	government : faa
Function	controller : local
Qualification	controller : non radar
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other other : unspecified cockpit
Resolutory Action	other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

At runup, engine performed well. Shortly after liftoff right magneto distributor gear teeth failed catastrophically. Engine lost power sufficiently so that level flight could not be maintained. After examination a mechanic indicated that his examination showed that failure of the gear teeth affected the timing for both magnetos because of random pulses from the right magnetic. I would suggest development of a solid state sensor which could detect asynchronous timing between the magnetos and which would then shut down the failed magnetic (i.e., the one which provided worse performance). The mechanic suggested that I could have switched to the left magnetic to maintain power, but I did not have sufficient altitude at the time of occurrence to experiment. A solid state device could have achieved the proper result almost instantaneously. A report of this incident has been made to the FAA. The engine was about 3 hours after its most recent 100 hour inspection at the time of the part failure.

Original NASA ASRS Text

Title: MAGNETO FAILURE SHORTLY AFTER TKOF FORCED PLT OF SMA TO RETURN LAND.

Narrative: AT RUNUP, ENGINE PERFORMED WELL. SHORTLY AFTER LIFTOFF RIGHT MAGNETO DISTRIBUTOR GEAR TEETH FAILED CATASTROPHICALLY. ENGINE LOST POWER SUFFICIENTLY SO THAT LEVEL FLT COULD NOT BE MAINTAINED. AFTER EXAMINATION A MECHANIC INDICATED THAT HIS EXAMINATION SHOWED THAT FAILURE OF THE GEAR TEETH AFFECTED THE TIMING FOR BOTH MAGNETOS BECAUSE OF RANDOM PULSES FROM THE RIGHT MAG. I WOULD SUGGEST DEVELOPMENT OF A SOLID STATE SENSOR WHICH COULD DETECT ASYNCHRONOUS TIMING BETWEEN THE MAGNETOS AND WHICH WOULD THEN SHUT DOWN THE FAILED MAG (I.E., THE ONE WHICH PROVIDED WORSE PERFORMANCE). THE MECHANIC SUGGESTED THAT I COULD HAVE SWITCHED TO THE LEFT MAG TO MAINTAIN POWER, BUT I DID NOT HAVE SUFFICIENT ALT AT THE TIME OF OCCURRENCE TO EXPERIMENT. A SOLID STATE DEVICE COULD HAVE ACHIEVED THE PROPER RESULT ALMOST INSTANTANEOUSLY. A REPORT OF THIS INCIDENT HAS BEEN MADE TO THE FAA. THE ENGINE WAS ABOUT 3 HRS AFTER ITS MOST RECENT 100 HR INSPECTION AT THE TIME OF THE PART FAILURE.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.