Welcome Guest. Sign in or Signup

3 Answers

Use of Mag switch

Asked by: 5972 views General Aviation

Would I harm a general aviation aircraft engine, like in a Cessna 172, when shutting it down, if I turn off the Mag switch immediately after moving the mixture to the cut-off position before the prop has completely stopped?

Ace Any FAA Written Test!
Actual FAA Questions / Free Lifetime Updates
The best explanations in the business
Fast, efficient study.
Pass Your Checkride With Confidence!
FAA Practical Test prep that reflects actual checkrides.
Any checkride: Airplane, Helicopter, Glider, etc.
Written and maintained by actual pilot examiners and master CFIs.
The World's Most Trusted eLogbook
Be Organized, Current, Professional, and Safe.
Highly customizable - for student pilots through pros.
Free Transition Service for users of other eLogs.
Our sincere thanks to pilots such as yourself who support AskACFI while helping themselves by using the awesome PC, Mac, iPhone/iPad, and Android aviation apps of our sponsors.

3 Answers



  1. Jason Schappert on Oct 22, 2010

    Will this cause harm…. generally no.However OVER TIME (quite a bit of time) this is going to be hard on the mags (fly weights and other internals)Best practice is to turn the switch to off after the prop has stopped turning
    Jason

    +1 Votes Thumb up 2 Votes Thumb down 1 Votes



  2. Curtis Ide on Oct 23, 2010

    Quick add-on – It’s good to let the mags run until the engine is completely shut down to help ensure you burn/expend all the fuel that is coming into the engine.  Helps keep those bottom sparks plugs clean.

    +1 Votes Thumb up 1 Votes Thumb down 0 Votes



  3. Brian on Oct 24, 2010

    Jason, would you mind elaborating on how that internal damage is caused? I am not well versed on magnetos and would be curious to understand this. Thank you.
     
    One more add from me — SAFETY! The mag switch grounds the magnetos and pulling the mixture empties the engine of all fuel. Combine, these two things prevent the engine from inadvertently starting. Leaving fuel in the engine now leaves you with only a 1/4 inch wire between life and death if that prop gets spun. Just a little corrosion on just the right spot on just the wrong day and… Well you get the idea. 
     
    Fly safe,
    ~Brian

    +1 Votes Thumb up 1 Votes Thumb down 0 Votes


Answer Question

Our sincere thanks to all who contribute constructively to this forum in answering flight training questions. If you are a flight instructor or represent a flight school / FBO offering flight instruction, you are welcome to include links to your site and related contact information as it pertains to offering local flight instruction in a specific geographic area. Additionally, direct links to FAA and related official government sources of information are welcome. However we thank you for your understanding that links to other sites or text that may be construed as explicit or implicit advertising of other business, sites, or goods/services are not permitted even if such links nominally are relevant to the question asked.