# Where can I find (or how can I calculate) the glide ratio for a PA-28-181?

I'm filling out ForeFlight's new glide slope feature, and I'm trying to find the glide ratio for a Piper Archer II (PA-28-181). I know the best glide speed is 76, but can't find the glide ratio. Any help on where to find this?

Edit:

Below is the glide range graph from my PoH, and below that is the information ForeFlight is asking for. I'm not really sure how to read that graph to get a glide slope number.

• This should be in the poh. – acpilot Mar 28 '17 at 19:57
• Thanks @acpilot just updated my question with what I think is the graph I need from the PoH, but not sure how to get the glide slop number off it. – Arel Mar 28 '17 at 20:33
• About 9.5:1 on a standard day according to the graph (~11,000 gets you ~20sm). My rule of thumb for most GA planes is 8:1. I plan 7:1 to account for slop and maneuvering for landing. – acpilot Mar 28 '17 at 20:46
• Awesome! Thanks @acpilot – Arel Mar 28 '17 at 20:55
• Answered here: aviation.stackexchange.com/questions/57262/… – xxavier Feb 14 '19 at 12:38

If you were to take off from an airport at 2,000' ASL on a standard day, and climb to 7,280' ASL you would be exactly 5,280' above the ground which means exactly 1 statute mile above the ground.

If you were to cut the engine, and then use the information available in the chart, you should be able to glide about 10 statute miles which yields about a 10 to 1 glide ratio.

• Fantastic answer. Thanks. – Arel Mar 29 '17 at 1:31

You will have to obtain this from the Pilot's Operating Handbook for the particular aircraft you are flying. Piper usually has a glide performance figure in the Perfeomance section of the POH. Trying to calculate your glide distance or glide ration by other means and you are probably entering dangerous waters.

• Thanks, I updated my question with the graph I think you're mentioning, and the ForeFlight box to give some context of why I'm trying to find the glide slope. – Arel Mar 28 '17 at 20:32
• If I'm reading the chart correctly, the glide ratio varies with the ambient air temperature. Therefore a standard glide ratio is not going to apply here. I would be hesitant to trust your life to this ForeFlight feature and instead rely on a thorough examination and learn the the numbers from this chart instead of trying to create a uniform glide ratio for the airplane. – Carlo Felicione Mar 29 '17 at 1:40
• Totally agree. I just put in a 7:1 glide ratio, and will use the feature as one more tool in the event of an emergency. – Arel Mar 29 '17 at 1:56

To calculate your glide ratio, work the graph to obtain the gliding range and convert the NM to Feet. Then see how many feet you travel per 1000 feet drop. Whatever number you obtain divide by 1000.