# Questions tagged [glide-ratio]

The ratio of the forward distance traveled to the vertical distance an aircraft descends when gliding without any power.

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### Does Best L/D sink rate increase as altitude increases?

As a glider pilot, we learn that Best L/D airspeed does not change with altitude. That is, the Indicated Airspeed (IAS) to fly in order to achieve Best L/D is the same no matter the altitude or air ...
1 vote
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### IAS vs ground speed when calculating speed to fly in wind

It's common for discussions around a glider's Polar Curve to describe how to use the Polar Curve to identify the best speed (Indicated Airspeed, IAS) to fly in a given wind condition (let's assume a ...
43 views

### Does this comment thread incorrectly conflate glide ratio with lift-to-drag? [duplicate]

In the comments on niels nielsen's answer to "Why are no recent small aircraft designed to be 'characteristically incapable of spinning' as the Ercoupe was?," John K commented, "[The ...
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### With existing tech and knowledge of meteorology, can aircraft be designed to reliably improve their range or loiter using updrafts to gain altitude?

Just what the question says. I want to know if aircrafts' range, loiter time, or other measures of merit can be dramatically and reliably increased using our current understanding of meteorology and ...
41 views

### Maximise Range Vs Pitching Down while flying a Glider in a Downward Air Mass

While flying a glider, if I encounter a downward moving air mass (i.e. sink) while on final, should I fly to maximise range (best lift to drag ratio) or should I pitch downward in order to exit the ...
893 views

### Why the heavier the aircraft is, the higher the airspeed must be to obtain the same glide ratio?

I know weight does not affect glide ratio. But why does higher weight need higher gliding speed?
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### Does glide ratio improve with increase in scale?

Will the same glider have higher glide ratio if its bigger in proportion or smaller in proportion?
324 views

### How to calculate and understand glide distance?

How would I calculate my glide distance? If I am at 8000 feet would I multiply 1.5 by 8 because the ratio is 1.5 NM per thousand ft? Which would be 12 NM Also where did a ratio of 9:5 come from? I may ...
81 views

### Size of speed brakes for glider

I have a concept glider and I am trying to calculate the required speed brake area. The clean glide ratio is currently 30, and with speedbrakes, I am aiming at reducing it to something around 7. I ...
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### glide ratio of an airplane formula

Good morning everyone, I found out that the glide ratio of an airplane can be calculated by this formula : 1/tan(y) considering y the angle formed by its nose and an horizontal line. Check this photo :...
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### How does the Boeing 787 Dreamliner's glide ratio compare to other airliners?

I just saw a documentary on the design of the Boeing 787 "Dreamliner" and one of the designers said that the wings were inspired by gliders. Looking at the production version of the plane, it is ...
238 views

### Sources for Aircraft Glide Ratio

I would like to gather data on the best glide ratio of different commercial aircraft. Unfortunately, it has proven non-trivial to obtain data aside from a few lucky examples. Eurocontrol's BADA gives \$...
1 vote
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### How is half of the wing strut (high wing) [or half the aileron (low wing)] a good reference to estimate gliding distance? [closed]

Through training and still to this day, I keep on using these reference points to judge if I am at the right distance from the runway or the field I aim to land at (forced landing).
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### How to accurately test glide ratio in given configuration?

How can glide ratio be accurately measured with typical GA airplane instruments in real conditions? What, if any, specialty instruments are used for professional glide ratio testing (such as a ...
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### Best glide speed vs. best glide angle? Maximum glide range?

I have some open questions regarding best glide in a descent: I understood, that there is a best glide speed. This best glide airspeed occurs at the highest lift-to-drag ratio (L/D). This best glide ...
1 vote
225 views

### Calculating best glide speed

I recently started flying a SGS 2-33 glider. The POH lists the stall speed as 31 mph for solo flight. Min sink speed is 38 mph and optimal glide speed is 45 mph. Being an old glider with imperfections,...
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### Does altitude affect glide ratio?

Lower altitude means higher air density, which means more liff, which means a glider can maintain a given glide slope at lower airspeed. As a rule, aircraft tend to have higher peak L/Ds at low ...
688 views

### Can weight reduce a plane's glide ratio?

The FAA says glide ratio doesn't change, regardless of weight, here on page 5-7. Glide ratio is not affected by weight because, while a heavier glider sinks faster, it does so at a greater airspeed. ...
529 views

### How is a "turning polar" constructed?

To start with something familiar: here's a flight polar. As we learned, the best glide speed is found by starting at the 0,0 point, and drawing a line tangent to the sink rate line. The intersection ...
1 vote
133 views

### How much thrust can a balloon generate with wings?

I have heard that some balloons have been made with wings, angled such that they generate some forward thrust during the ascent. Balloons can also theoretically generate thrust with wings during a ...
214 views

### F1A COMPETITION GLIDER

I am working on a school project. I have looked up the airfoil database. There is a wide range of airfoils I have tried to optimize for my glider to no avail. How do i choose the best airfoil for a ...
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### How to calculate sink rate from wing measurements

First of all, sorry to bother you when I am coming from a bird rather than aircraft background. I have two questions that I'm struggling to get an answer for. Firstly, how is sink rate calculated (...
11k views

### What was the Space Shuttle's glide ratio?

The Space Shuttles glided to a landing in the atmosphere after reentry. They were not good gliders, aerodynamically speaking, so their glide slope angle was rather steep. What was the glide ratio of ...
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### For maximum glide range, should I minimize glide angle or AoA?

I'm currently taking an aeronautical engineering course in school. For an upcoming project, we're going to build balsa toss gliders and we have to design our own wings. The program we're using (Aery32)...
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### Under what engine conditions is glide performance typically determined in performance charts?

The performance section of an information manual I am using states that the glide range indicated is "power off". Does this terminology definitely imply that the engine is not firing? or ...
2k views

### Descending on a given glide slope (e.g. ILS) at a given airspeed-- is the size of the lift vector different in headwind versus tailwind?

We had a discussion with friend and we were talking about if the airplane is on approach and the one is landing with tailwind and the other one is landing with headwind, so both have the same value of ...
558 views

### What happens if I am flying at a higher Lift/Drag ratio than required?

I created for me a table from an aircraft for Mach=0.8 for alpha= 0° to 8° Actually, I an alpha of alpha=4° should be sufficient, so that my lift coefficient is enough, to counterbalance the weight in ...
214 views

### Relationship between Load-Factor AND Gliding Ratio

I am wondering about the g-load and its relation to the so called gliding ratio. I read this really good contribution here on this forum: Does lift equal weight in a climb? So the g load factor is ...
223 views

### What are the engine-out implications of giant turbofans?

It seems that turbofans for civil airliners are improving fuel efficiency by building larger and larger fans that spin slower. For example, the RR Trent 800 introduced in 1993 had a diameter of 2.8m, ...
460 views

### How does pitch relate to glide angle?

When flying a glider, you have a polar curve. As your speed increases beyond best glide, your glide angle gets steeper. Say you are flying at best glide, you are looking through a specific point in ...
128 views

### What are "secondary precessional forces" that apply to boomerangs in flight?

note: This question is about the aerodynamics of boomerang flight and how it differs in microgravity environments. Some background information available here in Aviation SE: Are frisbees and ...
6k views

### Why are birdlike airfoils not used?

Here are two airfoils (lets focus on Re 100,000): SD7043-il which is simple to build and has a glide ratio of about 60 e376-il a birdlike and much harder to build if using paper or similar due to the ...
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### Why is the L/D ratio numerically equal to the glide ratio?

*L/D is ratio of two forces, lift and drag. *Glide ratio is ratio of two distances. Can you explain mathematically how they end up numerically equal and are they always equal?
1 vote
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### Can we show through simple geometry rather than formulae or graphs that the best glide ratio occurs at the maximum ratio of Lift to Drag?

For an unpowered glider, can we show through simple geometry involving force vector diagrams, rather than mathematical formulae or graphs, that the best still-air glide ratio is achieved at the angle-...
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### Do jet aircraft have a better glide ratio than propeller aircraft in general? If so, why?

Being fond of aviation, I play with software simulators a lot. I have noticed that while jets seem to be able to glide for a long distance even at zero throttle, propeller aircraft need to be ...
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### Does Green Dot Speed Calculation include banking Angle?

I'm wondering, whether the Green Dot- speed calculation in the Airbus PFD does account for the actual bank angle of the aircraft. ...
1 vote
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### How does retracting flaps help extend the glide of an aircraft?

As per the video from Smithsonian channel BA flight 38's captain retracted the flaps of the Boeing 777 by 5 degrees to extend glide, to travel further. Why?
1 vote
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### Mushing glide vs forward slip sink rate

Source: Wolfgang Langewiesche - Stick and Rudder; An Explanation of the Art of Flying I ran across a mushing glide in Wolfgang Langewiesche's - Stick and Rudder; An Explanation of the Art of Flying ...
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### How can a designer maximize the glide ratio of an aircraft with low aspect ratio wings, other than by increasing the aspect ratio?

As I understand it, the gliding range is given by a lift to drag ratio—hence to increase the gliding range, I would want to increase the lift and reduce the drag as much as possible. To that end, ...
940 views

### Why don't smaller powered airplanes have better lift-to-drag ratios?

Many airliners have LDRs near 20, and it sounds like the electric Eviation Alice may have an LDR of 24 at 240 kts, but many small planes typically have LDRs of only 8-10. It seems like they could ...
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### Could a commercial plane like Airbus A320 glide with no working engines from 11000 meters? [duplicate]

I have heard that pilots learn in simulators to fly also commercial planes without working engines, so that they glide. And still I have the impression, the chances that a plane could float from 11000 ...
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### Is V(L/D)max equivalent to best glide speed regardless of weight, engine, height, etc.?

I've read Carson's paper on V(L/D)max, and while theoretically interesting, it does not seem to me to be useful in actually finding the V(L/D)max of an arbitrary aircraft, as it assumes knowledge of ...
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### How to calculate or design glide ratio? [duplicate]

Was interesting to watch the explanation about glider here, especially about the glide ratio. Glide ratio is defined as the ratio between altitude when it start gliding (Y-axis) to the distance it can ...
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### How does the glide ratio change with velocity in a glider with air brakes deployed?

I'm interested in how the glide ratio steepens when increasing velocity, starting from the best slope (best L/D) velocity, in a high drag configuration (air brakes fully extended on a glider). I've ...
497 views

### Does lift coefficient for maximum range change for a glider experiencing headwind?

When a glider or unpropelled aircraft experiences headwind, I understand that the flight velocity and sink velocity for the "new" maximum possible range both increase (see velocity polar from How does ...
717 views

### Is the physical MAX8 design bad because software is required for the aircraft to stay airborne? [closed]

I'm not an aviator by any means, but one thing that has come up in recent conversations with friends is that the MAX8 is inherently unsafe because alone, unpowered, the craft is not 'aerodynamically ...
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### For how long can an Embraer E195 airplane glide at malfunction?

E195 specs: Maximum Takeoff Weight 52,290 kg Max Cruise Speed M 0.82 Cruise altitude: 35000 feet Assume the weather condition is perfect (no clouds or gust winds). Also assume this airplane is fully ...
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### How can planes with the same stall speed and power-to-weight ratio have such different takeoff field length, climb rate, glide ratio, etc?

I am interested in better understanding the performance differences between different planes that seem to be similar in many important ways but that differ greatly in performance. For example, take ...