Welcome Guest. Sign in or Signup

4 Answers

CARB HEAT & MAGNETO CHECK ON GRASS

Asked by: 1564 views Student Pilot

Hi guys ,just a quick question.

Why are we discouraged from doing a carb heat & dead cut check during  engine run-up on grass? 

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.

4 Answers

  1. Best Answer


    Kris Kortokrax on Feb 29, 2020

    That’s a good question. You should ask the person who told you this. Have that person show you something to justify his procedure.

    I learned to fly at an airport with only grass runways. Later, I flight instructed at an airport with only a grass runway. We always checked carburetor heat during runup and I always did a grounding check for the magnetos. Never had any problems.

    +1 Votes Thumb up 1 Votes Thumb down 0 Votes



  2. KDS on Feb 29, 2020

    As Kris wrote, it would be good to ask the person who told you that.

    However, I’ll take a stab at what the person’s answer will be.

    Carburetor heat is unfiltered air. They may be concerned about ingesting debris such as newly mown grass.

    For the dead cut check (what I would call the broken p lead check), the concern may be that a backfire could set the grass on fire.

    Hopefully you’ll get back with us after asking those questions and let us know what he or she said.

    +1 Votes Thumb up 1 Votes Thumb down 0 Votes



  3. Kris Kortokrax on Feb 29, 2020

    If your instructor is concerned that the engine will ingest newly mown grass, he is unfamiliar with the plumbing on the engine. The inlet for air for carburetor heat is behind the prop. The air then flows through scat tubing to the muffler and then through the muffler shroud, where it picks up heat, then through more scat tubing to the carburetor. It is unlikely that blades of grass (if they were able to be picked up and blown into the opening behind the prop) would survive the journey to the carburetor.

    As to a backfire setting the grass on fire, if the mag grounding check is done at idle (as it should be), the engine will not backfire. If the engine did backfire, I would be much more concerned about blowing out the seams on the muffler. Just for kicks, take a lit propane torch and touch it to the grass for the split second that a backfire would last. See what kind of fire you could ignite.

    +1 Votes Thumb up 1 Votes Thumb down 0 Votes



  4. ayavner on Mar 03, 2020

    Another possibility here is not so much the risk of ingesting or setting fire to grass, but the fact that if you are on a grass/dirt strip, there may be concern about throwing stones or nicking the blades at the higher RPM used for the run-up checks. Only other thing I can think of.

    0 Votes Thumb up 0 Votes Thumb down 0 Votes


The following terms have been auto-detected the question above and any answers or discussion provided. Click on a term to see its definition from the Dauntless Aviation JargonBuster Glossary.

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.