Gross weight vs Glidespeed

[Airpiraterob]

you can do all 3 and have absolute maximum weight savings

on an additional note, if you were wanting to loose alot of altitude, the common idea is to do the forward slip on approach. Thats good and everything however in a glider they slow to minimum sink speed...or a few knots less even very close to the stall and then do the forward slip. you drop like the preverbial rock towards a black hole. and in any headwind at all you loose the altitude and dont gain any distance. i tried to replicate this in a c150 once and well....it didnt work too well.

 

[dmspilot00]

Vnugget... you deleted your post, I thought what you said brought up an interesting point. Did you find evidence to show that you were wrong?

Also I wanted to point out something about that weight-change airspeed formula. That formula can be used with almost all speeds from stall speed, landing speed, and glide speed.

When you do use it (especially to calculate stall speeds), if you want an accurate answer you should start off with Calibrated Airspeed (KCAS), apply the formula, and then convert the answer back to indicated. Usually there will be a chart/graph to convert between the two. Near stall speed the difference between KCAS and KIAS in a 172 is significant.

The same formula can be used to calculate speeds under a G load, btw.

 

[VNugget]

I was right, but I found out that Airpiraterob already said it, so my post that said "_______, and no one has said this" was rendered quite.... dumb. (In case anyone missed what we're talking about, it's the point that a heaver (but otherwise identical plane) would, in real life, have more parasite drag to contend with, and thus haver a lower (L/D)max, and therefore not be able to glide as far.)

But, I have something else to attack now.

GeorgeTG said, Beware of the fact that L/D max is not the best glide speed.
Best glide is achieved at the tangent to the power required curve.

There is no contradiction there. Note that the Thurst required (which is identical to the total drag) curve is NOT the same as the Power required curve. Keep in mind that Power = Thrust * Velocity.

Best glide does occur at the lowest point on the Thrust required curve, which is (L/D)max (proof here), which does coincide with the tangent of the Power required curve.

Minimum sink, on the oher hand, occurs at the lowest point of the Power required curve, NOT at (L/D)max. This is because the glide angle is multiplied by the vertical component of velocity, just like the thrust req'd curve is multiplied by velocity to get the power req'd curve.