A C172 in cruise at 2500 ft declared an emergency and diverted due to loss of power caused by a fail...

Attributes
ACN	482285
Time
Date	200008
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : ggg.airport
State Reference	TX
Altitude	msl single value : 2500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	general aviation : instructional
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Navigation In Use	other
Flight Phase	cruise : level
Flight Plan	None
Person 1
Affiliation	other
Function	instruction : instructor
Qualification	pilot : cfi pilot : commercial pilot : instrument
Experience	flight time last 90 days : 160 flight time total : 600 flight time type : 300
ASRS Report	482285
Person 2
Affiliation	other
Function	instruction : trainee
Qualification	pilot : student
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other controllera other flight crewa
Resolutory Action	controller : issued advisory controller : provided flight assist flight crew : declared emergency flight crew : diverted to another airport
Consequence	other other
Supplementary
Problem Areas	Flight Crew Human Performance Maintenance Human Performance Aircraft
Primary Problem	Aircraft

Narrative:

Training flight in a C172 at 2100 ft cruise climb to 2500 ft when loss of RPM occurred. Violent shaking under the cowling and engine roughness was observed. We were able to sustain altitude at vy and 1800 RPM. Oil temperature and oil pressure remained constant -- no rise in temperature or loss of pressure. My first thought was fouled magnetos or a bad cylinder. We declared an emergency, as RPM's decreased and vibrations increased -- failure was imminent. Longview approach confirmed thompson airport was in our vicinity and we made a landing approximately 10 mins after initial loss of power occurred. It was determined by a mechanic that the rods on the #3 cylinder had snapped -- probably due to the exhaust valve not opening.

Original NASA ASRS Text

Title: A C172 IN CRUISE AT 2500 FT DECLARED AN EMER AND DIVERTED DUE TO LOSS OF PWR CAUSED BY A FAILED CONNECTING ROD.

Narrative: TRAINING FLT IN A C172 AT 2100 FT CRUISE CLB TO 2500 FT WHEN LOSS OF RPM OCCURRED. VIOLENT SHAKING UNDER THE COWLING AND ENG ROUGHNESS WAS OBSERVED. WE WERE ABLE TO SUSTAIN ALT AT VY AND 1800 RPM. OIL TEMP AND OIL PRESSURE REMAINED CONSTANT -- NO RISE IN TEMP OR LOSS OF PRESSURE. MY FIRST THOUGHT WAS FOULED MAGNETOS OR A BAD CYLINDER. WE DECLARED AN EMER, AS RPM'S DECREASED AND VIBRATIONS INCREASED -- FAILURE WAS IMMINENT. LONGVIEW APCH CONFIRMED THOMPSON ARPT WAS IN OUR VICINITY AND WE MADE A LNDG APPROX 10 MINS AFTER INITIAL LOSS OF PWR OCCURRED. IT WAS DETERMINED BY A MECH THAT THE RODS ON THE #3 CYLINDER HAD SNAPPED -- PROBABLY DUE TO THE EXHAUST VALVE NOT OPENING.

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.

A C172 in cruise at 2500 ft declared an emergency and diverted due to loss of power caused by a failed connecting rod.