Welcome Guest. Sign in or Signup

Please could someone provide me with an easy rule of thumb/ formula for top of descent for a private pilot. There seems to be no standard formula and some of them out there and have no explanation. Thanks in advance!

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. John D Collins on Aug 04, 2015

    With modern GPS avionics, the time remaining to your destination is readily available. If you know your altitude above the airport pattern altitude, you know how many thousands of feet you need to lose. Double the number of 1000’s of feet you need to lose and use this as the time remaining in minutes when you wish to start your descent. So my home airport has a 1500 foot traffic pattern and if I am at 8500 feet, then I need to lose 7000 feet from cruise to pattern altitude, Double 7 is 14 minutes. I often add an extra minute so I can be at pattern altitude well before joining the pattern. This time assumes you will use 500 feet per minute of descent. So I would start down when I am 15 minutes from my home airport.

    +2 Votes Thumb up 2 Votes Thumb down 0 Votes

  2. Dan S. on Aug 04, 2015

    If you want to use mileage from airport to start descent in a typical single, determine thousands of feet to descend to pattern altitude. Using Johns’s example, 7*2=14 and at 2 miles per minute, start descent 24 miles from the airport. I’ll usually add 1 mile as buffer.
    If you ever fly faster aircraft, 3 times the altitude to lose in thousands of feet works pretty well. With 30,000 feet to lose, multiply 30*3, you would need to start down around 90 miles from destination.

    +1 Votes Thumb up 1 Votes Thumb down 0 Votes

  3. Mark Kolber on Aug 05, 2015

    If you want an explanation of John’s formula, a generally accepted descent rate for a non-pressuruzed piston aircraft is 500 feet per minute. It is a rate that is comfortable for most passengers, not producing too rapid changes in pressurization.

    The rest is simple math to get the time away from destination and Dan’s addition simple math to convert the time to a distance based on speed.

    You can see multiple variations on the theme, most of which are simply using arithmetic shortcuts to make the math simpler. As an example, take John’s 7000 altitude loss and notice that 7000/500 and 7×2 give the same result.

    +2 Votes Thumb up 2 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.