# Can fighter aircraft glide?

In case of engine failure, do the fighter jets have such a stable airframe so that they can glide their way through to a nearest landing strip (As it happened in the case of Gimli glider)?

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They are more likely to point it at an empty field and ejecting. Safer for all involved. – ratchet freak Jul 15 '14 at 10:15
I'm pretty sure there are accounts of dead-stick fighter landings, I saw a cockpit recording of one on youtube a while ago – falstro Jul 15 '14 at 10:28
F16 dead-stick landing – falstro Jul 15 '14 at 10:31
@Wardy just because the engine is out doesn't mean the computer and the hydraulics don't work. I don't know about the Typhoon, but most aircraft that need them (as has been mentioned in the answers below) have backup systems to allow it to be controllable (thus able to glide to a safe landing) even without engine power, and even if it's aerodynamically unstable. – falstro Jul 16 '14 at 15:42
@Wardy and so is pretty much any modern fighter, including the F16, yet it can glide because it has backup systems (like a RAT or EPU) to power computers and hydraulics when the engine fails. I don't know if the Typhoon has such systems, but most aircraft do. – falstro Jul 18 '14 at 10:05

All airplanes can glide, if they couldn't they wouldn't be able to fly in the first place. When you glide an aircraft you are converting height into airspeed, which you can use to move across the ground. How far you can go across the ground for height lost is called the glide ratio for the aircraft. Gliders have a very high glide ratio as their wings are designed to provide lots of lift at low speeds, fighters have a very low glide ratio as they are designed to provide lift at a much higher speed enabling the fighter to achieve high airspeeds efficiently.

So a fighter will glide, it just won't be able to glide that far over the ground. If a fighter has enough altitude to trade for speed and a strip close enough by it can be done (and has been done in the past) by a skilled pilot.

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The question was about fighters, and I've get to see a fighter balloon... – GdD Jul 15 '14 at 16:42
@Articuno but, but, balloons can glide, in fact they are very good at it. :p – CGCampbell Jul 15 '14 at 18:01
@CaptainCodeman: Autogyration? – keshlam Jul 15 '14 at 20:54
This is not correct. Modern fighters eg. the Typhoon, F22, etc. are designed to be aerodynamically unstable. Without computer assisted corrections to their control surfaces they can not stay in the air. – JamesRyan Jul 15 '14 at 21:32
@JamesRyan, if I understand correctly, gliding means flight without propulsion (as in the case of the Gimli Glider that the asker gives as an example). If we took it to mean the absence of any power, it wouldn't be feasible with anything but mechanically actuated control surfaces. – arielCo Jul 16 '14 at 2:23

All airplanes can glide. Some glide better than others.

A very old reference I read talked about engine-out landings in military aircraft. Their procedure was arrive at the airfield at X feet, circle once and land. Trainers like the T-33 needed 2,500 feet, other aircraft needed 3,500-5,000 feet.

An F-104, which is basically an engine with fins, needed 20,000 feet for the landing loop. So unless you have a flameout in the stratosphere (or directly overtop an airport) you would simply point it at an empty space on the ground and eject.

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I was thinking to the f104 when reading the question :) thank you for that information. – Emmanuel Jul 16 '14 at 15:57
And yet successful dead stick landings were made in the F-104. For example, see en.wikipedia.org/wiki/Lockheed_XF-104#Testing_and_evaluation. – Fred Larson Mar 11 at 17:31

Yes, all aircraft have a glide ratio. On many of the higher-performance fighters, it's 1:1 at best (1 foot altitude traded for one foot forward gliding).

Many of the newer fighter aircraft are intentionally unstable. They aren't really flown by the pilot; they're flown by a Flight Control Computer System (FLCCS) which depends on electrical and hydraulic power; the pilot tells the FLCCS what they want to do and the FLCCS uses electrical signals and hydraulics to move the flight controls. Electricity and hydraulic power are provided by generators and pumps on a gearbox driven by the engine. Ergo, engine-out (especially on a single-engine bird) means they can lose the FLCCS which means they are, effectively, giant "lawn darts."

I spent multiple years as a Crew Chief on F-16's with Uncle Sam's Air Force. As a single-engine plane, we jokingly said that, when the engine went out, it was in "lawn dart mode."

The F-16 does have backup systems. The aircraft battery will supply power for a couple minutes, depending on what all you're using. The hydraulic accumulators will provide hydraulic power for a minute or two, assuming you don't get too crazy. And the Emergency Power Unit (a small, monopropellant turbine in the right strake of the aircraft) will start promptly after losing the engine, providing electricity and hydraulic power for several minutes as necessary (the battery and accumulators keep you under control while it spins up). Ergo, if you lose the engine, you lose propulsion but you still have electricity and hydraulic power. So you can still maintain control of the airplane.

We had more than one occasion, in my time, where we had an F-16 engine conk out (we were playing with brand spankin' new Block 50s with a new model of engine) and the pilot managed to glide the plane in without injury or damage to the aircraft. They were near the base when it happened, the EPU fired (so they were able to maintain control of the aircraft), the glide ratio was sufficient to reach the runway and the tailhook (yes, Air Force birds have 'em) caught the cable and stopped them safely.

So, the short answer is yes, modern fighter planes can glide. Different planes have different ratios, some of them little better than a rock thrown at altitude. And, even if they're designed to be inherently unstable, they have backup systems such that the pilot can maintain control in an engine-out situation.

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I don't believe you glide ratio 1:1. Even space shuttle had around 4:1 and it had higher higher wing loading and lower aspect ratio than most fighters. Also don't forget that aircraft needs thrust/weight higher than drag/lift (inverse of glide ratio) and modern fighters have thrust/weight just around 1, older had less. The wikipedia page lists F-104 with thrust/weight 0.54 at MTOW and lift/drag (glide ratio) 9.2 and that plane was extremely inefficient at slow speeds. – Jan Hudec Jan 15 at 17:18
Agreed, an F-104 in "clean" configuration has much better than 1:1. Ditto for the F-16. Load it up with external stores (increased aerodynamic drag and increased weight) and watch that drop. Additionally, glide ratio varies with speed. Faster = lower glide ratio. The Wikipedia page on the the Space Shuttle indicates that glide ratio varies from 1:1 (hypersonic) to 4.5:1 (approach speed). For an F-16, with external stores, at high speed, 1:1 is not far off. When the engine dies on an F-16, first orders of business are: punch external stores and decelerate to more efficient speed. – Meower68 Jan 16 at 15:04
True, at max speed the lift/drag ratio equals weight/thrust, otherwise you'd still be accelerating. However when you need to glide, you are going to do it at best glide speed, so that is the relevant number and when you write “lift/drag ratio” without further qualification, most people will assume it's the best achievable lift/drag ratio. – Jan Hudec Jan 16 at 15:15
Increased weight shouldn't have a big effect on the glide ratio and should only increase the speed for optimal gliding, I think. External stores still increase drag of course. – JulianHzg Apr 17 at 22:13
@JulianHzg weight per se (without additional drag) does not affect glide ratio $E$, but for sure the speed for $E_{max}$ ;-) – yankeekilo Apr 20 at 17:59

If the shuttle can glide to a landing, so can a fighter aircraft. Gliders have speed brakes to control the glide path angle, and the fighter can vary the angle of attack, which works in much the same way. Also, it can slalom towards the field, so if the pilot picks a landing site close and long enough, the landing is no big problem. Landing gears are normally designed to fall out with gravity alone if the locking mechanism is unlocked. However, I doubt the pilot will be able to deploy all the high lift devices, so the touchdown speed will be rather high.

On modern fighter aircraft with artificial stability, the avionics and hydraulic pumps need to work, or the aircraft will not be controllable by a human pilot. In that case, ejection is probably the safest option if all engines fail. If the glide takes more than only a few minutes, hydraulic pressure will have been lost shortly after the engine(s) and any auxiliary power unit (EPU) stop running, and even if the battery-powered flight computer still gives the correct commands, the actuators will not work anymore. Fighters need to be light, so running times of EPUs are only a few minutes, mostly.

For a successful flare, an aircraft needs a minimum L/D of approximately 5, so it will fly even if no more altitude can be spent during the landing rotation. The only aircraft I ever "met" which did not fulfill this criterium was the European return vehicle project "Hermes" before it got winglets. They were added to make the transition between final approach and touchdown flyable. Hermes was never built, so all these landings happened purely in a computer.

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If the shuttle can glide to a landing, so can a fighter aircraft - why is that true? Are you saying that what a shuttle can do a fighter can do? I think you're missing a premise in there. I don't think the shuttle being able to glide to a landing logically implies that a fighter aircraft can do so also. – user2168 Jul 15 '14 at 19:50
Shuttle aerodynamics are so awful that any fighter aircraft can beat it hands down in gliding characteristics (if the wing stations are not stuffed with ordnance, that is). – Peter Kämpf Jul 15 '14 at 19:53
Okay, so you're saying "1. The shuttle can glide to a landing. 2. Things with better aerodynamics than the shuttle can glide at least as well as the shuttle. 3. Fighters have aerodynamics that are better than the shuttle. 4. Therefore, fighters can glide to landing." ? – user2168 Jul 15 '14 at 19:55
The shuttle was often described as having "the aerodynamics of a highly polished brick." Exaggeration of course, but it makes the point that it's one of the worst anyone has voluntarily flown. – keshlam Jul 15 '14 at 20:56
Any aircraft that can fly can glide, provided that the controls are working, and if an unstable fighter design, the [stabilizing] computer is also working. If the controls aren't working, the best glide ratio in the business ain't gonna help. – Phil Perry Jul 16 '14 at 13:22

One of the most important things I learned ( in my opinion) when I played around with flight simulators is that all planes can glide. Every aircraft has a "glide plane" which is basically an angle of approach to the ground where you won't stall. The angle depends on the physical characteristics of the plane (wings, etc.). So if you lose power, you can always glide to the ground. The problem is whether your glide plane is wide enough to allow you to reach an airport. You can think of the glide plane as basically telling you that you will drop X feet every Y minutes. So if you want to land at airport you have to time it right (you can also point the nose down to increase speed and approach the ground faster, if you don't have enough glide path left to circle the airport completely.)

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