Determining the height of a plane on descent?

[bbfpv]

I was out flying my quad @ 500ft in a big public park and a Southwest jet came right over the top of the park during its descent. I tried to descend and fly out of the path just to be safe because I had no clue what height it was at, and the size of the thing from the ground seemed much larger than I usually see flying around. I'm sure it was several thousand feet above me but it freaked me out a little and I'm apprehensive now w/o knowing roughly how low one can safely get w/o crashing before the runway. Does anyone know a formula for calculating the rough estimate for the HGL of a commercial jet during it's descent given the distance from the airport? I ask because I live near 2 major airports and the flight patterns change pretty regularly.

In any event, I was flying almost exactly 12 miles from the airport. Appreciate the help.

 

[Meta4]

Here's a descent profile from a recent flight I had in a 737.

The airport was at 1,171 ft ASL.
At 12 miles out the jet was approximately 3500 feet AGL, travelling at 205 mph and well out of normal Phantom range.

 

[bbfpv]

i figured as much but it looked so much closer! awesome man. appreciate the reply.

 

[Steeleagle]

Most airports keep the jets at least 3000 ft above ground until their final descent on an average 3 degree glide slope. 3 degrees is 1000 ft of altitude above ground for every three miles from the runway.

 

[SteveMann]

Does anyone know a formula for calculating the rough estimate for the HGL of a commercial jet during it's descent given the distance from the airport? I ask because I live near 2 major airports and the flight patterns change pretty regularly.

Typically at ten miles, airplanes on an IFR approach, which includes all airlines, will be at 3,000 to 4,000 ft.

You can download the IFR approach plate yourself to see the approach profile for any given runway.

Start here
https://www.faa.gov/air_traffic/flight_ ... rocedures/

Click on your state. Then find the airport and click on it's identifier. (PHX in this example).
Now select the approach you want to look at.

On this page you will find the descent profile that all airline aircraft will follow. (Lower-right corner of this approach).

 

[landmannnn]

Download one of those plane tracker apps to your phone, they will tell you the altitude. Or if you don't want to pay you can find several websites showing the info if you google plane tracker.