I have a question based on flight track logs on https://flightaware.com.

In one of the logs I'm looking at, it says that at time 08:16:15 PM the altitude was 36,000 ft and plane speed was at 473 mph. At time 08:16:58 PM, the plane descended to 35,400 ft.

I did some rough calculations and realized that the speed 473 cannot be along the vertical plane. Then, what is this speed? Is it along the descent path? Also, what angle do planes make with the vertical plane when descending? Where can I get this information?

  • 1
    $\begingroup$ Why would you even think that is vertical speed? (Assuming that flightaware is accurate in both time and altitude) A difference of 600 feet in 43 seconds works out to a descent rate of 850 fpm, which is completely normal. $\endgroup$ – abelenky May 4 '18 at 16:20
  • $\begingroup$ Normal takeoff pitch (“longitudinal axis against horizon”) angle is, as a rule of thumb, about 15 degrees; normal takeoff flight path angle („height/distance“) maybe 10 degrees (note: an aircraft rarely points where it goes in the vertical plane; most aircraft - unless there is very strong wind - usually point above where they go). After takeoff, climbing to cruise altitude, both angles will be lower. For descent, it’s about 0-3 degrees pitch, and -3 degrees flight path angle. Every single flight will deviate from the above, but as an average order of magnitude, this should work quite well. $\endgroup$ – Cpt Reynolds May 4 '18 at 19:31

473 would be the horizontal speed.

Pitch angle is limited to 30 degrees in the US per FAR, https://www.faa.gov/regulations_policies/faa_regulations/

More than that the flight is considered Aerobatic and parachutes are required.

| improve this answer | |
  • $\begingroup$ Then, the vertical speed must be (36,000 - 35,400)ft / (08:16:15 PM - 08:16:58 PM) sec = 837 ft/min. Isn't this too small? $\endgroup$ – Teodorism May 4 '18 at 16:22
  • 1
    $\begingroup$ 600 ft in 43 seconds? Seems reasonable. I descend in my small 4 seat plane at 500 ft/min, just to avoid too much ear popping. Jets are more or less constant 8,000 foot air pressure in the cabin, can do higher rates without too much discomfort for the passengers. $\endgroup$ – CrossRoads May 4 '18 at 16:47
  • $\begingroup$ Isn't that too small for what, exactly? Descending from 36,000 ft would take approximately 30-35 minutes. That is a very normal descent. You can hear and feel the engines throttle back right when you hear "This is the captain: we've begun our initial descent, and will be on the ground in about 35 minutes" $\endgroup$ – abelenky May 4 '18 at 16:54
  • 1
    $\begingroup$ Rather than linking to the entire set of FAA regulations, can you link to the specific one that you've referred to? (I assume 91.307?) $\endgroup$ – Pondlife May 4 '18 at 18:08
  • 1
    $\begingroup$ 30 degrees up is very rarely reached on a normal commercial flight, 30 degrees pitch down virtually never. $\endgroup$ – Cpt Reynolds May 4 '18 at 19:22

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.