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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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 ...
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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 ...
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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 ...
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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 ...
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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, ...
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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 ...
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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 ...
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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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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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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. ...
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686 views

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?
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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?
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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, ...
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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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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 ...
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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 ...
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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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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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Aerodynamics and fuel consumption of a powered glider

I want to optimize the flight distance of a powered glider model airplane, without the use of soaring. I've studied some aerodynamics books, but still feel unsure about my conclusions. Please tell me ...
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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 ...
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How useful would the space shuttle OMS actually be in atmosphere?

When speaking of space shuttle landings, they always mention that it is "very poor glider, with one shot, no go-arounds." Of course this is true; however, if the Shuttle found itself in a situation ...
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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 ...
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766 views

Why is polar curve of a glider dependent on flight load?

This is my first question here. I'm just a glider in education phase and not yet a pilot, but because I'm also physicist, I'm interested in some details more than other people. My question is simple:...
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What is the effect of fuselage weight on a model glider?

I've built a model glider and wanted to see the effect the weight of the fuselage had on its performance. It flew the further with more weight which seems counter intuitive. I can exert more force ...
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Why aren't any wingsuits able to sustain flight?

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 (Edit: this is not always true. See below answers for why). So, would it not ...
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Are frisbees and boomerangs technically gliders?

Frisbees and Boomerangs are heavier-than-air, unpowered, and fly through the air. So are they technically gliders? They also rotate, so I wonder if these are actually some kind of rotorcraft-type ...
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Does it help to climb in case of a partial engine failure?

When the engines of a airplane show irregularities that do not reduce performance but indicate a possible failure of the engines, is it useful to climb to a higher level, to increase the glide length ...
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How long can a passenger aircraft glide without engine power? [duplicate]

Assuming that the aircraft is cruising at 36000 ft and lost engine power, how long could a passenger aircraft glide?
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What would be the best alternative during a dead-stick approach?

(Disclaimer: I am not a pilot so my understanding of things may be really broken) If a plane has lost engine power, has limited altitude to work with, and is upwind of a landing strip, and the pilot ...
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What is the glide ratio of a DA42?

I was looking for the best glide speed of a DA42 with both engines out, but it seems it's not in the POH. In the emergency checklist, it only mentions a speed of 85 knots to maintain on final approach ...
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How can we calculate the benefit gained from taping glider wing roots?

Most (all?) glider pilots will be familiar with the practice of taping wing roots. As most of the gliders in my glider club (and I would guess, in the world) are stored with the wings detached, the ...
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How can I calculate the glide time for a B737 with engine failure?

We talked today in our flight school about the following scenario: if I climb in my 737-800 to FL100 and then have a dual engine failure, how many seconds would it take me before I reach ground? I'm ...
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Can glide ratio be increased with bi-wing configuration?

We all know that increasing the wingspan of an aircraft tends to increase the glide ratio. Instead of increasing the wingspan, could an extra wing of the same size or less as in a bi-wing ...
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During an engine failure should I deploy 10° of flap or keep it clean?

Imagine I have an engine failure in cruise flight with a Cessna 152 or 172. Should I select 10° flap to increase glide angle? Would it give me more range to reach safety?
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Where can I find (or how can I calculate) the glide ratio for a PA-28-181?

I'm filling out ForeFlight's new glide slope feature, and I'm trying to find the glide ratio for a Piper Archer II (PA-28-181). I know the best glide speed is 76, but can't find the glide ratio. Any ...
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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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Could a big plane glide significant distances, same a ordinary glider (1000 km or about)?

Seems that a usual glider is not limited by its glide descent rate and can fly much more than this. It uses air masses that move upward to gain the altitude. Are these effects limited by the size of ...
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How is the glide ratio affected when converting a wheeled plane to floats?

I'm looking for published data that describe the effect on glide ratio when an aircraft is converted from wheeled to float configuration. I suspect that the glide ratio goes down considerably due to ...
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Where can I find glide ratios for commercial aircraft?

I know that light aircraft have poor glide ratios (typically 1:10) compared to commercial aircraft (typically 1:20 or above). I was wondering if there is a source where one can find the glide ratio by ...
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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 ...
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Does full nose up trim yield best glide in Cessna 172/152 for a given load?

I heard from a ground instructor that full nose up trim will yield best glide in a 152 and 172. As I understand best L/D, a lighter loaded plane will require a slower glide than the same craft ...
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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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Is there a way to approximate the best glide speed for maximum glide distance in a headwind during flight? [duplicate]

Flying at an airspeed corresponding to an aircraft's maximum glide ratio in calm air will maximize the distance covered for a given altitude (AGL). But in a headwind, the horizontal velocity would be ...
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What is a mushing glide?

Source: Wolfgang Langewiesche - Stick and Rudder; An Explanation of the Art of Flying Why is it called a mushing glide? In this glide, does the aircraft point its nose less (or more?) steeply? How ...
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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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How to calculate the Glide Ratio from Drag & Lift?

I know that $c_{d}=0.03 + 0.095c_{l}^2$. What is the glide ratio?
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How can the glide ratio in a balanced turn be estimated?

I am trying to estimate the bank angle/turn radius required to lose a given amount of altitude during a full orbit. This has led me to trying to estimate glide ratio in proportion to $L/D_{MAX}$ of an ...