Worn mags bring down Cessna

Aircraft: Cessna 177RG. Injuries: None. Location: Gila Bend, Ariz. Aircraft damage: Substantial.

What reportedly happened: According to the pilot, while the airplane was in cruise flight he heard a loud noise from the engine compartment, followed by an immediate loss of engine power.

He attempted to restart the engine while diverting to the nearest airport. The engine would not restart and he realized that he wouldn’t be able to reach the airport, so he decided to land on an interstate highway. As he approached the highway, the pilot noticed heavy traffic and decided to land on an adjacent service road. During the landing roll, the left wing hit a tree.

The post-accident examination of the engine revealed that both sets of magneto points were not opening. Inspection of the single-drive dual magneto found that the cam followers on both sets of points were worn to the point that they could no longer open the contacts.

The magneto had accumulated 603.7 hours at the time of the accident since installation and 92.56 hours since the most recent magneto timing adjustment. No further anomalies were noted during the examination of the engine that would have precluded normal operation.

Probable cause: A total loss of engine power during cruise flight due to both sets of magneto points failing to open as a result of excessive wear of the magneto cam followers.

NTSB Identification: WPR11FA186

This April 2011 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.


  1. Jody says

    This is something I see all the time as an A&P. Mags should be checked at each 500 hours, regardless of any signs of problems. JD is correct slick does not make a dual Magneto, but regardless of make or model all mags should be inspected at each 500 Hours.

  2. Jeff says

    It would be nice to know if these mags are Bendix’s or Slick’s and what model so we could check our own mags out. Mags are one of those things that we just expect to work after the mag check and they are incredable reliable, except when they break.

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