Welcome Guest. Sign in or Signup

2 Answers

CAS TAS MN

Asked by: 2040 views Instrument Rating

When climbing at a constant Mach number below the tropopause trough an inversion, what will happen with CAS and TAS?

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.

2 Answers

  1. Best Answer


    John Hobbs on Mar 02, 2019

    Using my handy E6B calculator (my own)

    At IAS 110 kts (similar to CAS) at 4000 ft, and 10 C, TAS is 118 kts on a certain day. (29.80 inHg)
    If temp goes up to 14 C, TAS goes up to 119.
    Increasing altitude to 4500 ft, TAS goes to 120 kts
    Increasing temp to 19 C, TAS goes to 121 kts
    Increasing altitude to 5000 ft, TAS goes to 122 kts, 5500 ft to 123 kts

    This seems like pretty big temp inversion?

    TAS is calculated using air density, specifically the SQRT(Barometric pressure@seaLevel) divided by the Barometric pressure@altitude) x’s EAS (close to IAS at lower altitudes).

    So it depends, however TAS trends up.

    +1 Votes Thumb up 1 Votes Thumb down 0 Votes



  2. John Hobbs on Mar 07, 2019

    Using my handy E6B calculator (my own), just now corrected for slight error.

    At IAS 110 kts (similar to CAS) at 4000 ft, and 10 C, TAS is 117, not 118 kts on a certain day. (29.80 inHg)
    If temp goes up to 14 C, TAS goes up to 118, not 119.
    Increasing altitude to 4500 ft, TAS goes to 119, not 120 kts
    Increasing temp to 19 C, TAS goes to 120, not 121 kts
    Increasing altitude to 5000 ft, TAS goes to 121, not 122 kts, 5500 ft to 123 kts

    https://www.hobbsdronephotography.com/e6b

    +1 Votes Thumb up 1 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.