Squawk Box

May 2018 Issue




Cessna 172 SDRs

The following information is derived from the FAA’s Service Difficulty Reports and Aviation Maintenance Alerts.

threshold plane

Cessna Model 172R Skyhawk
Brake System Failure

Pilot found a brake anomaly. Checked aircraft and found that the anchor had detached from bulkhead assembly (p/n 0513488-11), causing the brake system failure.

Part total time: 8076.0 hours


Cessna Model 172N Skyhawk
Loose Magneto Points

Engine would not start. After inspecting magneto, found misfire on test stand. Opened magneto for inspection and found loose contact point where riveted to ground. The points (p/n 4371) were installed as part of a 500-hour inspection repair and had approximately 25 hours in service.

Part total time: 25.0 hours


Cessna Model 172M Skyhawk
Buckled Firewall

During annual inspection, found lower firewall buckled on right side near nose landing gear reinforcement plate.

Part total time: 2176.0 hours


Cessna Model 172
Plugged Fuel Vent Lines

Pilot made a precautionary landing due to a rough-running engine. Pilot checked fuel and heard a “wooshing” sound when opening the right tank fuel cap. Pilot thought he corrected a venting problem and took off. Aircraft lost power on climbout. Investigation revealed a plugged fuel system main vent line, plugged vent interconnect line at left tank and a restricted right vented fuel cap (p/n c156003-0101).

Part total time: 2500.0 hours


Cessna Model 172N Skyhawk
Loose Carb Pump Discharge Nozzle

The student was recovering from a power-on stall demonstration. The throttle stuck open at full rpm and the student could not reduce power. The instructor declared an emergency and returned to the field, where he executed a dead-stick landing and coasted to a taxiway to be towed in. Evaluation revealed the pump discharge nozzle had come free from the carburetor and was found in the carburetor heat box. A small crimp noticed in the nozzle indicates it jammed in the butterfly valve, causing the carburetor to be in its full-power setting.

Part total time: 381.0 hours


Cessna Model 172
Failed Piston Pin

Visible metal was found in the engine oil and oil filter media during scheduled maintenance. The engine was disassembled and inspection revealed the #5 piston pin had failed and appeared to be the source of the metal. The crankcase, crankshaft, camshaft and connecting rods were all sent to various certified repair stations for further inspection and re-certification. The cause for this failure is undetermined.

Part total time: 145.0 hours