Thread: Finding speed of best gliding?

Hello CT-friends,

I fly a CT2k and a CTSW 2007. The flight manual of the CT2k has very little performance data. The only given value is Vy which should be 78 kts at 0° Flaps.

I wonder if this will be the speed for the best gliding as well? For my understanding of aerodynamics the best gliding will be reached with negative flaps. In Germany we have -12° and I ask myself, what will be the speed for the best gliding with this configuration?

I will use this question for my own challenge and will try to find the speed by myself. My Idea for that is to find the maximum speed at which a higher angle of attack with unchanged power setting will lead to loosing altitude. If I find this airspeed, it will be the one at which the lift/drag ratio has is maximum and for that it will be the speed fot best gliding.

What do you think? Am I wrong? Any other ideas?

Kind regards

Markus

Hallo Marcus,

I've asked myself the same question, and I've tried different speeds with engine off while airborne ( over the runway at high altitude !!! ) , and I've found the best speed for my CT2K to be at around 105 km/h. The flaps -12 at that speed it's not the best setting, instead use 0 flap ( I guess that due to poor lift at negative settings and slow speed , you are forced to increase angle of attack , thus leading to increased induced drag , thus altering the gliding ratio ).

best glide in my ctsw seems to be 62kts and 15 degrees.

i don't know why you would think best glide comes with reflexed flaps, best glide is best L/D, at reflex you ave low lift and low drag.

you are looking for the configuration and pitch attitude that results in the highest lift with the lowest drag.

CTSW best glide speed 63 kts. In engine out procedures section in manual it lists 15° flaps.

Try this link to obtain the glide speed for yourself, if you want.

Test Card - best glide speed

Glenn, thank you very much for this interesting link.

The performance data for the CTSW are well known. But I have a CT2k which has longer wings than the CTSW.

The point I like to discuss is my approach to find the best L/D ratio.

My guess is:
If I fly straight and level at the speed with the best L/D ratio, any increase in angle of attack will lead to loosing altitude. Because the plus of drag will overcome the plus of lift. This in mind, it should be very easy to find this speed using nested intervals technique. If I am faster than the best glide-speed, the ship will climb when AOA is increased. The exercise will be to find the highest airspeed, at which the ship will respond with sinking when AOA is increased.


Right??

i think the easiest way to find best l/d is to look for minimum sink first. best glide will be close to minimum sink and that is easy to spot.

try different flap settings with a closed throttle and trim fro the lowest vertical speed. in the ctsw you can easily see that 15degrees @ 62kts is far better glide then you can get with more or less flaps

I am not sure if your plan will equate to a windmilling or stopped engine, because most drag is not directly opposed to lift. The worst case would be to test your method and see what value you obtain. That value should be close to the best rate of climb speed since that relies on minimized drag for best performance. In real-world situations, it is very difficult to maintain an exact airspeed. Therefore, your calculations will be optimistic. I would follow the instructions of the link to set up a test plan and compare the two values.

I hope I'm not just stating the obvious. I have been a lurking student pilot on this forum for quite a while and I've just graduated to being a lurking pilot. I'm still a newbie at all this!

My instructor showed me that the way to determine best "endurance speed" (so that's the one with the most glide) was to start in slow flight and increase the revs in small, regular increments and note the resultant rise in speed. The increment that showed the greatest increase in speed was the best glide/endurance speed. I suppose this could be repeated at various flap setting and the results compared.

I hope that helps.

endurance equates to min sink while best glide equates to max distance

glenn,

i wasn't suggesting my plan as best method but just a quick way to confirm that best glide is with 15 degrees.

"endurance equates to min sink while best glide equates to max distance "

Thanks for the correction. This is always a great place to learn.