C172 north model has dual magneto failure shortly after takeoff. Able to return land successfully. M...

Attributes
ACN	365697
Time
Date	199704
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : bdl
State Reference	CT
Altitude	msl bound lower : 1000 msl bound upper : 1000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : bdl
Operator	general aviation : instructional
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Flight Phase	climbout : initial
Flight Plan	None
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : cfi pilot : commercial
Experience	flight time last 90 days : 120 flight time total : 1250 flight time type : 1000
ASRS Report	365697
Person 2
Affiliation	government : faa
Function	controller : local
Qualification	controller : non radar
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : declared emergency other
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

After an uneventful preflight and runup in a C172 I began a standard takeoff on runway 29 at bdr. The current winds were approximately 300 degrees at 11 KTS as reported by the control tower. The takeoff itself was uneventful. At approximately 1000 ft MSL (900 ft AGL) the engine suddenly lost power to approximately 800-1200 RPM. At this time an emergency was declared and the aircraft was turned back to the bdr airport. After this was accomplished the emergency checklist was completed as far as applying carburetor heat, switching tanks and ensuring a 'full rich' mixture. We then proceeded to make an emergency landing which was successfully completed on runway 6. After taxiing clear of the runway the aircraft was secured and all the occupants exited the aircraft unharmed and the appropriate information was given to the auths. It was then later determined that a dual magneto failure was the cause of the power loss. Callback conversation with reporter revealed the following information: reporter states the actual cause was that both magnetos are tied to a single shaft and when gears stripped on 1 side then they were thrown into the other one. So much for redundancy. The mechanics contacted the FAA and it was indicated that this is the first time they had heard of such an incident. Reporter doubts it, however. This was an north model 172.

Original NASA ASRS Text

Title: C172 N MODEL HAS DUAL MAGNETO FAILURE SHORTLY AFTER TKOF. ABLE TO RETURN LAND SUCCESSFULLY. MAINT INSPECTION FOUND LACK OF REDUNDANCY CAPABILITY WITH BOTH MAGNETOS TIED TO A SINGLE SHAFT.

Narrative: AFTER AN UNEVENTFUL PREFLT AND RUNUP IN A C172 I BEGAN A STANDARD TKOF ON RWY 29 AT BDR. THE CURRENT WINDS WERE APPROX 300 DEGS AT 11 KTS AS RPTED BY THE CTL TWR. THE TKOF ITSELF WAS UNEVENTFUL. AT APPROX 1000 FT MSL (900 FT AGL) THE ENG SUDDENLY LOST PWR TO APPROX 800-1200 RPM. AT THIS TIME AN EMER WAS DECLARED AND THE ACFT WAS TURNED BACK TO THE BDR ARPT. AFTER THIS WAS ACCOMPLISHED THE EMER CHKLIST WAS COMPLETED AS FAR AS APPLYING CARB HEAT, SWITCHING TANKS AND ENSURING A 'FULL RICH' MIXTURE. WE THEN PROCEEDED TO MAKE AN EMER LNDG WHICH WAS SUCCESSFULLY COMPLETED ON RWY 6. AFTER TAXIING CLR OF THE RWY THE ACFT WAS SECURED AND ALL THE OCCUPANTS EXITED THE ACFT UNHARMED AND THE APPROPRIATE INFO WAS GIVEN TO THE AUTHS. IT WAS THEN LATER DETERMINED THAT A DUAL MAGNETO FAILURE WAS THE CAUSE OF THE PWR LOSS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THE ACTUAL CAUSE WAS THAT BOTH MAGNETOS ARE TIED TO A SINGLE SHAFT AND WHEN GEARS STRIPPED ON 1 SIDE THEN THEY WERE THROWN INTO THE OTHER ONE. SO MUCH FOR REDUNDANCY. THE MECHS CONTACTED THE FAA AND IT WAS INDICATED THAT THIS IS THE FIRST TIME THEY HAD HEARD OF SUCH AN INCIDENT. RPTR DOUBTS IT, HOWEVER. THIS WAS AN N MODEL 172.

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.

C172 north model has dual magneto failure shortly after takeoff. Able to return land successfully. Maintenance inspection found lack of redundancy capability with both magnetos tied to a single shaft.