Welcome Guest. Sign in or Signup

4 Answers

Most efficient cruise altitude

Asked by: 4195 views Aerodynamics, Aircraft Systems, General Aviation, Private Pilot, Student Pilot

Hi Gentlemen,
 

Is flying at low or high altitudes more efficient , and why ?

Thanks in advance ,
P.G.

 

 

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


    Christopher Arndt on Mar 15, 2013

    Assuming standard temperature and pressure, no wind, higher altitudes provide a more efficient way of flying.

    Because gravity affects air molecules as they do everything else, air is much more dense at lower altitudes. This denser air provides better performance for takeoffs and landings, however at cruise it creates a disproportionately higher amount of drag as more air molecules are interacting with the aircraft surfaces for a given volume of air.

    The higher you go, the less friction the aircraft encounters and the faster the aircraft can go if thrust remains consistent. This is limited, obviously, because aircraft engines operate better with denser air (more O2 to burn) and every aircraft reaches a point where it can not maintain a given amount of thrust to maintain airspeed.

    This is also expressed in the difference between True Airspeed and Indicated Airspeed. Indicated airspeed is increase in pressure exerted by fast moving air molecules in the pitot system. Is it NOT a measure of the absolute speed those air molecules are moving, only the pressure they exert. At sea level, TAS/IAS are the same on a standard day. TAS can be thought of as the absolute speed an air molecule is moving in relation to the aircraft, and is a function of temperature and pressure. TAS increases the higher you go.

    0 Votes Thumb up 0 Votes Thumb down 0 Votes



  2. Prodromos Galaktidis on Mar 17, 2013

    Thank you sir.

    0 Votes Thumb up 0 Votes Thumb down 0 Votes



  3. Prodromos Galaktidis on Mar 17, 2013

    Thank you sir

    0 Votes Thumb up 0 Votes Thumb down 0 Votes



  4. jacob conell on Mar 17, 2013

    Looking a the winds are important. If you have a 20kts cross wind at 3000ft it might be a 40kts tail wind at 7000ft.

    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.