A little aviation trivia for ya...
- Thread starter AlexSP
- Start date
E_Dawg
Moderator
Yeah but Acadia you just change the speed... there's an easy formula to figure it out:
new best glide =
(published best glide) x square root(actual weight/max gross)
That formula also works for Va changes with weight; this means they will all glide the same distance, but the heavy acft will get there first.
new best glide =
(published best glide) x square root(actual weight/max gross)
That formula also works for Va changes with weight; this means they will all glide the same distance, but the heavy acft will get there first.
Acadia
Well-Known Member
Agreed if you adjust the speed for the weight. The above question though states that each aircraft maintains best glide per the POH. That is pretty much what 99% of pilots are trained to do (use a single best glide speed for all conditions). I know that I have never computed best glide for a given weight. I just use what ever the POH lists.
So based on the question as stated the heavier aircraft (assuming its not over max gross) will glide further than the lighter one.
So based on the question as stated the heavier aircraft (assuming its not over max gross) will glide further than the lighter one.
Acadia
Well-Known Member
[ QUOTE ]
Any glider pilot will tell you that both airplanes will travel the same distance; the only difference is that the heavier airplane will get down at a faster rate of decent. That is why glider pilot add weight to their gliders during glider races.
[/ QUOTE ]
Only if you adjust the speed at which you glide at for the weight of the aircraft. Otherwise the one with the best lift to drag ratio (L/D max) will be able to glide longer and further.
That’s what all of my aerodynamics texts claim anyway.
Any glider pilot will tell you that both airplanes will travel the same distance; the only difference is that the heavier airplane will get down at a faster rate of decent. That is why glider pilot add weight to their gliders during glider races.
[/ QUOTE ]
Only if you adjust the speed at which you glide at for the weight of the aircraft. Otherwise the one with the best lift to drag ratio (L/D max) will be able to glide longer and further.
That’s what all of my aerodynamics texts claim anyway.
flyover
New Member
Two things on this gliding stuff.
1) There must not be any glider pilots on the forum. In cross country competitions they keep the weight high if lift is good and low if lift is bad. If the lift is good they want to weigh as much as possible to go further, faster between thermals.
2) With jet transport aircraft the lighter you are the faster you come down. This is because you build up kinetic energy by raising weight to a height. The more weight at a given height the more energy you have stored. Once you've raised it you have it working for you. It will, for example, help to overcome drag, which is a constant.
When the airplane is heavier, it's harder to get down and you have to include that factor in your planning. On the airplane I fly it is quite noticable how much faster it comes down at light weights as opposed to landing at max landing weight.
1) There must not be any glider pilots on the forum. In cross country competitions they keep the weight high if lift is good and low if lift is bad. If the lift is good they want to weigh as much as possible to go further, faster between thermals.
2) With jet transport aircraft the lighter you are the faster you come down. This is because you build up kinetic energy by raising weight to a height. The more weight at a given height the more energy you have stored. Once you've raised it you have it working for you. It will, for example, help to overcome drag, which is a constant.
When the airplane is heavier, it's harder to get down and you have to include that factor in your planning. On the airplane I fly it is quite noticable how much faster it comes down at light weights as opposed to landing at max landing weight.
Acadia
Well-Known Member
I fly and tow gliders.
The simple answer is that any aircraft will get the best glide range when it maintains the angle of attack that produces maximum L/D max (most lift for least amount of drag). This translates into a particular airspeed for a particular aircraft to obtain the maximum glide ratio. Published best glide speed in the POH is usually based on max gross weight for safety reasons (if you used the speed based on a lighter aircraft while flying a heavier aircraft you could be dangerously close to a stall).
The question that started this post was very simple. It gives two identical 172's (one of which is lighter) and both maintain best glide per the POH. Without recalculating the best glide speed (which will give you maximum L/D max) the heavier aircraft will be using a speed that is more correct for the weight and will have the maximum lift to drag ratio and glide farther.
THIS IS A GOOFY LITTLE TRIVIA QUESTION.
The simple answer is that any aircraft will get the best glide range when it maintains the angle of attack that produces maximum L/D max (most lift for least amount of drag). This translates into a particular airspeed for a particular aircraft to obtain the maximum glide ratio. Published best glide speed in the POH is usually based on max gross weight for safety reasons (if you used the speed based on a lighter aircraft while flying a heavier aircraft you could be dangerously close to a stall).
The question that started this post was very simple. It gives two identical 172's (one of which is lighter) and both maintain best glide per the POH. Without recalculating the best glide speed (which will give you maximum L/D max) the heavier aircraft will be using a speed that is more correct for the weight and will have the maximum lift to drag ratio and glide farther.
THIS IS A GOOFY LITTLE TRIVIA QUESTION.