does the flattest glide give the longest time in the air?and if not,why not?

Answer 1

As you slow the aircraft, the rate of descent will increase. When you lower the nose, the rate of descent will increase. There is a point about 20% below normal cruise that will provide the best glide for distance and time. The only way to find the best glide speed for time or distance is to look in the aircraft handbook. I once climbed my Cessna with oxygen to the highest altitude possible. With full power, a slight trim to nose up would stall the aircraft and a little nose down trim would cause a descent. The altitude was 17,500 feet MSL.

The link below is about glide speed and sink rate in a glider. You should be able to learn something there ... I did!

Answer 2

The flattest glide will shorten both the time in the air and the distance covered. The reason being: In level flight with no power, the aircraft will begin to slow, and when reaching stalling speed will drop straight down. If there is enough altitude to regain the lost airspeed, you can repeat this until you hit the ground.
When power is lost, the aircraft should be trimmed to best glide speed, and this is achieved by a slightly nose down attitude. This results in both the longest time in the air and thus, the distance traveled.

Answer 3

The answer to your question is no. The pictures from the link in the previous answer illustrate this well. Have a look at that link:

http://home.att.net/~jdburch/polar.htm

In the pictures, the Yellow plane is flying at best L/D speed, or best glide angle. The Green plane is flying slower, at the speed for minimum sink rate.

The Yellow plane has the flattest glide and will travel the farthest, but the Green plane stays in the air the longest.

This is definitely counter-intuitive, but is correct nonetheless. The reason behind this is the interaction between two different types of drag on a glider: induced drag and parasitic drag. Induced drag is caused by the creation of lift - it is higher the SLOWER you fly. Parasitic drag is caused by aerodynamic inefficiency of forward travel through the air - it is higher the FASTER you fly.

The best glide speed occurs where the sum of parasitic and induced drags are minimized. The minimum sink speed happens at a lower point - even though there is more induced drag (this causes you to glide a lower distance), the sink rate is lower because the additional drag comes from producing more lift.

Answer 4

It's not necessarily the angle of the glide but the speed of the aircraft in the glide that gives you the best glide ratio ( distance traveled forward/altitude lost). For example, the Cessna 172 (four passenger, single engine airplane) I teach in has a best glide speed of 65 knots, around 72 mph. A speed lower or higher then that number will shorten the distance available while gliding.

The best glide speed is also dependent on weight and was figured by test pilots at maximum gross weight, so the speed changes ever so slightly at a weight less then that.

Answer 5

The flattest glide is going to limit your airspeed, so you won't be covering as much ground. It will, however give you the most time in the air. The best glide angle is a compromise between the amount of ground covered and descent rate, and will be found at the aircraft's maximum lift/drag coeffiecient.

Answer 6

While I could see a correlation, the flattest glide does not necessarily mean the slowest decent.

Answer 7

No, air movement across the air foil fights gravity.
Air is never static and constant turns into the wind currents are required to maximize flight duration. One wing low, varied directions ( turns ), could keep a glider airbourne for days!

Answer 8

you want an ideal 14:1 ratio this can be scaled up or down to whatever craft needs to glide