43

I suspect this heavy depends on the type of the aircraft, so lets assume we are considering a small airplane. Absolutely right, it does vary widely. The parameter you're asking about is called glide ratio and it is directly related to another parameter called lift-to-drag ratio or L/D ratio. This is a fundamental characteristic of the aerodynamics of a ...


40

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 experimented with different airfoil shapes by using exchangeable ribs on the gliders and by testing model wings on a rotation test stand (Rundlaufapparat). There ...


29

No, there's no way an airliner can glide 1000km, this is because its wing is designed for fast cruising speeds, and it's much heavier compared to the lift generated than a glider. Gliders are light and have huge wings for their weight, which means they can get lifted by powerful air currents. An airliner is not going to be able to do that. The longest ...


27

I'm aware that under zero power it is a glider, but there are gliders that sustain flight and have enough lift to climb etc. This statement is a bit incorrect. Gliders don't climb like aircraft as they are constantly falling to the ground unless they catch a thermal, wave lift or ridge lift, in which case they can ride the updraft to gain altitude. In ...


20

You keep it clean: adding flaps adds drag. You can see this in Section 3 of the Cessna POH, which includes a Maximum Glide (distance) diagram. In the C172S POH that I checked, it notes that maximum distance is achieved with: SPEED 68 KIAS PROPELLER WINDMILLING FLAPS UP ZERO WIND (A tailwind would extend your range, but only in one direction.) ...


19

Attempting a tight turn, while low and slow, is an almost certain recipe for disaster. Your first option of landing with a tailwind is possibly preferable - there is no inherent danger landing with a tailwind - it'll extend your landing, and is not ideal. However, it is much safer than trying to maneuver into a position with a headwind with only part of the ...


19

There are very small jets that for hype-related reasons are called wingsuits. As current jet technology (and propeller technology) is easily capable of producing (from a human-portable frame) enough thrust to lift itself and a human-sized load, there is no obstacle to creating a true powered wingsuit. The reaction surfaces are very small in relation to the ...


19

As an ex-hang-glider pilot... Two other answers have covered the basic concept of gliding - namely that you're constantly descending, and to stay aloft you need to be in air that's rising faster than you're descending. Early hang gliders and paragliders had no problems staying up in normal ridge lift with glide ratios of 7ish:1. Before that, they were just ...


16

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 gradient. No precipitation or shielding by cirrus clouds anywhere along the route. Or you limit your trip to a back-and-forth along a mountain ridge. A good ...


16

"Glide performance" is measured by "Lift-to-drag ratio": In aerodynamics, the lift-to-drag ratio (or L/D ratio) is the amount of lift generated by a wing or vehicle, divided by the aerodynamic drag it creates by moving through air When you look for examples you'll see that for the most part larger airliners do indeed have a more ...


15

This is more an addendum than an answer, regarding "birdlike" airfoils. Ignoring the fact that birds can modify geometry, chord and camber of their wing when required, what can at best characterize a bird's wing airfoil, in addition to camber, is maximum thickness' location, very close to the leading edge, and constant minimal thickness between ...


14

As glide ratio is the same as the L/D ratio, the increase in drag due to the addition of floats will reduce it. The Beaver's POH gives the effect of addition of floats in the glide ratio: DHC-2 Beaver's Glide ratio; image from DHC-2- Beaver POH Note that at their configuration for best glide ratio, there is a drop in about 10% in glide ratio for the ...


13

There are plenty of smaller power planes that achieve those numbers; motorgliders. And motorgliders with L/Ds in the high teens and low 20s are pretty efficient cruisers. So the real question is; why aren't all light aircraft made to be like motorgliders? Well, motorgliders have their disadvantages. The long wing span is a problem fitting in on the ...


11

As far as I know the space shuttle is no longer in use. However, the glide ratios (more than one in different configurations) can be found on the Wikipedia page: Space Shuttle Wikipedia page. There it states that “The orbiter's maximum glide ratio/lift-to-drag ratio varies considerably with speed, ranging from 1:1 at hypersonic speeds, 2:1 at supersonic ...


11

As discussed here, glide ratio is related to the L/D (lift-to-drag) ratio of the plane. When talking about commercial aircraft, "glide ratio" is typically used to mean the ratio with engines inoperative. If the jet engines aren't running, they add a lot of drag, which will decrease the L/D ratio from the typical max value. This analysis estimates the max L/...


11

To give some concrete examples: A Cessna 172 might fly at 2000 ft for a short hop, or at 12500 ft for a longer cross-country flight. My rule of thumb is about 1.5 nautical miles glide per 1000 ft altitude above ground level, thus: From 2000 ft, a Cessna would be able to glide about 3 nautical miles (3.5 statute miles, 5.5 km), and it would take about 3 ...


11

The NASA website quotes an approximate ratio of 1 The shuttle was designed with a low L/D ratio (~ 1) because during the descent the spacecraft must be slowed from about 17,300 mph to about 250 mph at landing. (Source) Note that glide ratio is normally equal to the lift to drag ratio - Wikipedia article - Aviation.SE Question


9

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 respective best speed for optimum L/D. Your initial assumptions are right: Lift: $L = c_L\,\rho\,\frac{v^2}{2}\, S\, n_z$ Load factor: $n_z = \frac{1}{\cos\varphi}$ ...


9

If you were to take off from an airport at 2,000' ASL on a standard day, and climb to 7,280' ASL you would be exactly 5,280' above the ground which means exactly 1 statute mile above the ground. If you were to cut the engine, and then use the information available in the chart, you should be able to glide about 10 statute miles which yields about a 10 to 1 ...


9

A few reasons: if we're talking glide range from altitude, then jets certainly can glide longer! They fly MUCH higher than most props do, even turboprops! Second, propellers are draggy when they're at idle- you effectively have a big speedbrake on the nose of your plane. This is the reason a lot of planes have featherable props- they can be turned into the ...


8

That ground instructor is giving you bad information. You can not make a blanket statement like "full nose up trim" and expect it to be valid for any and all situations. You are correct that the best L/D speed will yield the best glide ratio and that the speed will vary with weight. The best trim position is the one that will maintain the best glide speed ...


8

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 comparing the same thing. Take-off means that the aircraft has to gain an energy difference with a potential and a kinetic component. FAR 23.53 demands a height ...


8

Glide is measured in what's called "glide ratio". For every foot of altitude the airplane loses, how far forward can it go? Sailplanes (gliders) have a glide ratio around 40 to 1. It can be much more or less, depending on the model. The glide ratio of the Cessna 172, the most popular single engine airplane, is about 10 to 1. The Boeing 767 that lost all ...


8

Let's look at what exactly is shown by each curve: The glide ratio curve plots glide ratio (horizontal distance divided by vertical distance) against airspeed. The polar curve plots vertical speed against airspeed. The x axis (airspeed) is the same for both plots, but the y axis is different. To convert one curve to the other, we need to convert glide ...


8

Glide distance does indeed depend heavily on the airplane's characteristic glide ratio, which depends on airspeed, as the answers above describe. However, the answers above assume still air, and real air is never still. If you glide with a steady tailwind, you'll glide further than you will in still air; a steady headwind will cut your glide. (You'll get ...


7

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 point in the bottom diagram can be constructed by drawing a line (red in the example above) from the origin of the coordinate system with the gradient given by the ...


7

All standard fixed wing aircraft are able to glide. The key measure of performance in gliding is the glide ratio which is related to the lift-to-drag ratio of the aircraft. The glide ratio of a clean A320 is 17:1 which means it can travel 17 units of distance forwards for every 1 unit of distance downward at best glide speed. Using your figure of 11,000 ...


7

It depends on a number of factors including the aircraft type, its associated glide/descent ratio at max L/D, where the a/c in relation to the landing site, your current absolute altitude, other potential landing sites nearby, etc. Many of these factors should have been discussed and anticipated for in the pre takeoff briefing prior to flight and is going ...


7

Both-engine-out glide performance isn't accounted for and isn't a certification requirement (of any airplane that I'm aware of). Airliners have good glide performance as a happy side effect of design optimization for cruising at high altitudes. What does have to be accounted for is single engine performance issues; things like departure performance with an ...


6

Why is it called a mushing glide? The aircraft is not cleanly cutting through the air. It is "mushing" through the air at a high angle of attack creating lots of drag and a slow forward airspeed. In this glide, does the aircraft points its nose less (or more?) steeply? The aircraft has its nose pointed up (less steeply) than a normal glide. How does ...


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