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I get a variation of the glide ratio with $\frac{2}{\bigl(\cos\varphi + \frac{1}{\cos\varphi}\bigr)}$ for circles flown with a bank angle of $\varphi$ when compared to straight flight at the respectiv …

Are we comparing apples to oranges again? The differences in take-off length are far too big with such similar performance numbers, and I agree that they should be closer together - if we are really c …

First, the 1000 km glider trip requires three prerequisites: Excellent weather for the whole of the trip. Strong thermals caused by lots of sun, a high cloud base and an unstable atmospheric thermal …

Yes, altitude does affect glide ratio, but only slightly. With increasing altitude, air temperature drops and with it the Reynolds number of the flow. This is mitigated, but not completely offset, by …

The curves in the top chart are gradients. The bottom chart lists these gradients over flight speed. Say you have in the top chart the y-value L/D = 36 at an x-value of 36 m/s, you do this: Every p …

This can be easily answered with a spreadsheet. Start with speed $v$ going from 20 m/s to 50 m/s. Add a column for the zero-lift drag coefficient and keep in mind that the increasing Reynolds number w …

Early biplanes did use similar airfoils. Not as extreme as the Eppler 376, but still very thin and highly cambered. When Otto Lilienthal started his glider experiments, he tried to copy storks. He exp …

When you pitch the nose down to gain speed, it feels as though you are pitching down a long way This is because the change of the cockpit angle towards the horizon is the sum of both the angle of at …

So, is the L/D [of] a cruising aircraft best when bottom is concave? If we use gliders as a reference, the bottom of the best airfoils is only very slightly concave, almost straight, in order to all …

With a given wing span, everything that reduces drag will increase the gliding range. Aspect ratio is less of a factor here because induced drag depends on wing span, not aspect ratio. But increasing …

It really depends on the aircraft. Some have plenty of rudder authority and sideslip very well, others are better at stall onset with still plenty of elevator and aileron authority. Now first to the …

Is it true, that this best glide speed is given in terms of indicated airspeed IAS and hence is independent of the elevation? Yes. The best glide speed needs you to fly at the optimum polar point, a …

If only the maximum lift coefficient suffers from the imperfections, your minimum sink speed is very close to the stall speed and the best glide speed stays unaffected. If a major mass increase (say, …

Your table looks at least partially wrong. A Boeing 707-320 never achieved an L/D of 19.4. If you have more reliable figures for fuel consumption, engine efficiency and range, you can use the Breguet …

First of all: Scaling laws. The ratio of inertial to viscous forces in the flow around the aircraft becomes larger with bigger size. This is also helped by the generally higher wing loading of lager a …