Welcome Guest. Sign in or Signup

4 Answers

Propeller Efficiency

Asked by: 12171 views Aerodynamics, Aircraft Systems

Which statement is true regarding propeller efficiency? Propeller efficiency is the A

OPCION A: ratio of thrust horsepower to brake horsepower.

OPCION B: actual distance a propeller advances in one revolution.

OPCION C: difference between the geometric pitch of the propeller and its effective pitch.

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. Nathan Parker on Sep 05, 2012

    Efficiency has no units of measure, so you know it can’t be B or C, which have dimensions of Length.

    +3 Votes Thumb up 4 Votes Thumb down 1 Votes



  2. Eric Hawicz on Sep 05, 2012

    The answer can also be found in the PHAK, Chapter 4, on the section on basic propeller principles.

    +1 Votes Thumb up 1 Votes Thumb down 0 Votes



  3. Steve Pomroy on Sep 05, 2012

    Hi Khoda.

    Efficiency is a measure of how well a device (such as a propeller) converts an input into an output. For a propeller, the input is brake horsepower, and the output is thrust horsepower. Divide the two and you get a number between 0 and 1. This is your prop efficiency, where 0 means that all of the input is lost to waste (inefficiencies), and 1 means that the conversion is perfect (not gonna happen in the real world). Efficiency can be converted to a percent if you multiply by 100. Nathan also raises a good point about units/dimensions.

    Cheers,
    Steve
    http://www.flightwriter.com
    http://www.skywriters.aero

    +6 Votes Thumb up 6 Votes Thumb down 0 Votes



  4. superbird3000@yahoo.com on Oct 02, 2012

    The correct answer is option C.

    100% efficiency would indicate that the propeller moves forward the entire pitch of the prop in one revolution. Since nothing is 100% efficient, the prop will move somewhat less than the actual pitch, which results in a ratio. That is your efficiency (if the pitch is 42″ and the efficiency is 80%, then the actual forward movement in 1 revolution would be 33.6″). This is consistent with boat propellers as well.

    -11 Votes Thumb up 2 Votes Thumb down 13 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.