Airbus A320 Glide Ratio ?
Airbus A320 Glide Ratio ?
What is the airbus a320's glide ratio ??? Anyone?
thanks OXO !
Probably not dissimilar to most other airliners, which is about 12:1. that's more than adequate for something that spends most of its time nudging Mach 1, where actually having the wings not provide much lift would be an advantage for maximum speed and structural integrity, but not quite so useful without power and flaps when trying a landing! Note that there's a big difference between some stats you'd read for this, because with a full load of baggage, px and fuel, the glide ratio will be affected.
If you can get enough airspeed in a dive and keep the aircraft clean until the last minute, it's technically not that hard to glide an aircraft in with a ratio such as that, but of course the moment you flair, the airspeed will drop rapidly, although with the amount of inertia an airliner has, that would help quite a bit. The real problem is that most airliners use their flaps to slow their descent and increase their lift, which is not an option when you have no engines to overcome the massive drag you get with the flaps deployed, so most airliner dead stick landings would have to be done at high speed because of the lack of power available to deploy the flaps and the lack of power to overcome their drag if you could get them down. With the flaps up, airliners can maintain their speed quite well in a dive, which is why they have drag inducing flaps and speed brakes which get used in their descent from cruise altitude (to stop them overspeeding, which they can quite easily do, a Boeing 727 is known to have passed Mach 1 once in an emergency dive some years ago). Descending from cruise in an airliner is often done with the engines providing very little thrust at all and it's not unusual for an airliner to have to begin its descent for landing about 50 miles away from where it intends to land, so you can see that they don't exactly drop like a stone with some speed on the clock.
There are several well known incidents where airliners have had to glide in when they've lost their engines, some attempts more successful than others. For example, an Air Canada Boeing 767 glided to safety on an old airbase (Gimli, Manitoba) which was actually in use as a drag strip at the time of the incident (1983). In that incident, the aircrew misinterpreted a cockpit warning and assumed incorrectly that a fuel pump had failed and shut down the engines at 41,000 feet (which equates to about a 100 mile gliding range, all things being equal). With so much height available, they had plenty of options as far as where to go was concerned, but in most airliners, if the engines stop, the lack of available power to drive the hydraulics which operate the control surfaces can make life hard for the pilots, and so most airliners are equipped with a deployable emergency Ram-air turbine (usually located near the front of the fuselage in clean air). The ram-air turbine can be used to power a limited number of systems, although sometimes the crew will have to choose which ones they want, so it's not a perfect solution. This sort of thing is what makes the US Air crew's performance all the more admirable, because if you try that sort of thing in something like FSX, it probably won't take into account the lack of hydraulic power for the control surfaces unless you have a sophisticated payware add-on aircraft that models all that kind of stuff. Another thing which makes the NYC river forced landing impressive, is the fact that on such a short flight, it is doubtful that the crew would have had enough time to dump their fuel to reduce their weight and would therefore have been forced to come in quicker than in a normal landing, especially if doing it without flaps, so they might very well have been clocking 180 knots on the descent.
You might be interested to know that in my own copy of the SOPs for the A320/321/330, there is actually nothing listed with regard to losing both engines, it merely deals with what to do if you lose one engine, which is kind of odd, because it does have a procedure page for ditching and evacuation when on the water. You should note these are usually airline specific so mine might be different from what US Air uses (mine are for a European airline - I've deleted the name of the airline which appears on mine, because these are not supposed to be widely circulated although they are based on what you get from Airbus Industrie, so they're not exactly top secret) I've scanned the single engine failure after V1 procedure pages for you, just in case you are curious about the kind of thing the P2 guy would be looking at if he was consulting the A320's SOPs book (note that the ECAM is the engine and crew alerting system, which displays on a screen in the cockpit and the FADEC is the digital engine control system):
Other famous attempts to glide airliners include:
A British Midland Boeing 737 which crash-landed at Kegworth in the UK in 1989 (again when the crew shut down an engine in error after misreading the instruments). In that incident the aircraft landed short of the runway at East Midlands Airport and ploughed across a motorway ending up with the tail section broken off on the road's embankment. 47 of the 118 people on board the aircraft were killed, but somewhat miraculously, nobody on the ground was injured despite the motorway being fairly busy at the time. The airline was criticised for several errors, not least of which was the one made by the crew in shutting down their remaining good engine after one engine failed and they thought it was the other one (this was caused by them being confused by the then new glass cockpits coming into use on next generation 737 models), but primary criticism centred around the fact that the aircraft flew over several perfectly reachable airports before trying to land at East Midlands because the British Midlands engineers on the ground wanted the crew to try and get the aircraft back to where their repair facilities were. Which is a an unbelievably stupid thing to have done.
A British Midland Canadair C-4 Argonaut airliner also glided in for a crash landing on my home town of Stockport in 1967 (in fact my dad was one of the first people on the scene and rescued some of the survivors from the burning wreck). There are conflicting reports as to whether the crew attempted to glide it in or whether it was out of control as it crashed, the pilot had no recollection of the crash and the other crew died, so there was very little conclusive evidence, although my dad, who witnessed the crash, has told me the pilot had what he thought was a good stab at landing given what little space he had in which to try it. One of the legacies of that particular crash was the autopsies on those killed in the crash, which revealed that most of the victims survived the crash but broke their legs, making it impossible for them to escape from the burning wreckage. This led to several improvements in future airliner design and as a result airliner crash landings are considerably more survivable these days than they were back then.
A United Airlines DC-8 ran out of fuel en route Portland Oregon in 1978 after the crew failed to adequately communicate their desperately low fuel state to air traffic control, who did not bump them up the landing queue because they were unaware of the seriousness of their condition, as a result it ran out of fuel on final approach and ploughed into a residential area in a semi-controlled glide. 10 of the 189 people on board were killed, nobody on the ground was hurt, but the casualty figure is misleading, as several survivors were very severely injured. Interestingly (and almost like something from a movie), among the survivors was a criminal being transported by an air marshall, who uncuffed the prisoner in preparation for the crash landing. The prisoner was seen to go back into the wreckage more than once and help numerous passengers before making an escape. He was urged to turn himself in and told that his heroic actions would see him treated favourably, and sure enough he did turn himself in several days later and the authorities kept that promise. This is thought to be the initial basis for the movie 'Accidental Hero'.
As you can see from the fatalities on a few of those examples, it's not as easy as some people might think to get an airliner down in one piece when the rubber band conks out, but as one example shows, it's not unknown. Of course when you fly a glider, every landing is dead stick, but our gliders don't weigh 80,000 kilos and have swept wings designed to work best at Mach .85! So, along with the general populace who don't have some sort of pilot's licence, even we'll have to acknowledge that it was a great bit of skill demonstrated earlier in the week by that US Air crew.
If you can get enough airspeed in a dive and keep the aircraft clean until the last minute, it's technically not that hard to glide an aircraft in with a ratio such as that, but of course the moment you flair, the airspeed will drop rapidly, although with the amount of inertia an airliner has, that would help quite a bit. The real problem is that most airliners use their flaps to slow their descent and increase their lift, which is not an option when you have no engines to overcome the massive drag you get with the flaps deployed, so most airliner dead stick landings would have to be done at high speed because of the lack of power available to deploy the flaps and the lack of power to overcome their drag if you could get them down. With the flaps up, airliners can maintain their speed quite well in a dive, which is why they have drag inducing flaps and speed brakes which get used in their descent from cruise altitude (to stop them overspeeding, which they can quite easily do, a Boeing 727 is known to have passed Mach 1 once in an emergency dive some years ago). Descending from cruise in an airliner is often done with the engines providing very little thrust at all and it's not unusual for an airliner to have to begin its descent for landing about 50 miles away from where it intends to land, so you can see that they don't exactly drop like a stone with some speed on the clock.
There are several well known incidents where airliners have had to glide in when they've lost their engines, some attempts more successful than others. For example, an Air Canada Boeing 767 glided to safety on an old airbase (Gimli, Manitoba) which was actually in use as a drag strip at the time of the incident (1983). In that incident, the aircrew misinterpreted a cockpit warning and assumed incorrectly that a fuel pump had failed and shut down the engines at 41,000 feet (which equates to about a 100 mile gliding range, all things being equal). With so much height available, they had plenty of options as far as where to go was concerned, but in most airliners, if the engines stop, the lack of available power to drive the hydraulics which operate the control surfaces can make life hard for the pilots, and so most airliners are equipped with a deployable emergency Ram-air turbine (usually located near the front of the fuselage in clean air). The ram-air turbine can be used to power a limited number of systems, although sometimes the crew will have to choose which ones they want, so it's not a perfect solution. This sort of thing is what makes the US Air crew's performance all the more admirable, because if you try that sort of thing in something like FSX, it probably won't take into account the lack of hydraulic power for the control surfaces unless you have a sophisticated payware add-on aircraft that models all that kind of stuff. Another thing which makes the NYC river forced landing impressive, is the fact that on such a short flight, it is doubtful that the crew would have had enough time to dump their fuel to reduce their weight and would therefore have been forced to come in quicker than in a normal landing, especially if doing it without flaps, so they might very well have been clocking 180 knots on the descent.
You might be interested to know that in my own copy of the SOPs for the A320/321/330, there is actually nothing listed with regard to losing both engines, it merely deals with what to do if you lose one engine, which is kind of odd, because it does have a procedure page for ditching and evacuation when on the water. You should note these are usually airline specific so mine might be different from what US Air uses (mine are for a European airline - I've deleted the name of the airline which appears on mine, because these are not supposed to be widely circulated although they are based on what you get from Airbus Industrie, so they're not exactly top secret) I've scanned the single engine failure after V1 procedure pages for you, just in case you are curious about the kind of thing the P2 guy would be looking at if he was consulting the A320's SOPs book (note that the ECAM is the engine and crew alerting system, which displays on a screen in the cockpit and the FADEC is the digital engine control system):
Other famous attempts to glide airliners include:
A British Midland Boeing 737 which crash-landed at Kegworth in the UK in 1989 (again when the crew shut down an engine in error after misreading the instruments). In that incident the aircraft landed short of the runway at East Midlands Airport and ploughed across a motorway ending up with the tail section broken off on the road's embankment. 47 of the 118 people on board the aircraft were killed, but somewhat miraculously, nobody on the ground was injured despite the motorway being fairly busy at the time. The airline was criticised for several errors, not least of which was the one made by the crew in shutting down their remaining good engine after one engine failed and they thought it was the other one (this was caused by them being confused by the then new glass cockpits coming into use on next generation 737 models), but primary criticism centred around the fact that the aircraft flew over several perfectly reachable airports before trying to land at East Midlands because the British Midlands engineers on the ground wanted the crew to try and get the aircraft back to where their repair facilities were. Which is a an unbelievably stupid thing to have done.
A British Midland Canadair C-4 Argonaut airliner also glided in for a crash landing on my home town of Stockport in 1967 (in fact my dad was one of the first people on the scene and rescued some of the survivors from the burning wreck). There are conflicting reports as to whether the crew attempted to glide it in or whether it was out of control as it crashed, the pilot had no recollection of the crash and the other crew died, so there was very little conclusive evidence, although my dad, who witnessed the crash, has told me the pilot had what he thought was a good stab at landing given what little space he had in which to try it. One of the legacies of that particular crash was the autopsies on those killed in the crash, which revealed that most of the victims survived the crash but broke their legs, making it impossible for them to escape from the burning wreckage. This led to several improvements in future airliner design and as a result airliner crash landings are considerably more survivable these days than they were back then.
A United Airlines DC-8 ran out of fuel en route Portland Oregon in 1978 after the crew failed to adequately communicate their desperately low fuel state to air traffic control, who did not bump them up the landing queue because they were unaware of the seriousness of their condition, as a result it ran out of fuel on final approach and ploughed into a residential area in a semi-controlled glide. 10 of the 189 people on board were killed, nobody on the ground was hurt, but the casualty figure is misleading, as several survivors were very severely injured. Interestingly (and almost like something from a movie), among the survivors was a criminal being transported by an air marshall, who uncuffed the prisoner in preparation for the crash landing. The prisoner was seen to go back into the wreckage more than once and help numerous passengers before making an escape. He was urged to turn himself in and told that his heroic actions would see him treated favourably, and sure enough he did turn himself in several days later and the authorities kept that promise. This is thought to be the initial basis for the movie 'Accidental Hero'.
As you can see from the fatalities on a few of those examples, it's not as easy as some people might think to get an airliner down in one piece when the rubber band conks out, but as one example shows, it's not unknown. Of course when you fly a glider, every landing is dead stick, but our gliders don't weigh 80,000 kilos and have swept wings designed to work best at Mach .85! So, along with the general populace who don't have some sort of pilot's licence, even we'll have to acknowledge that it was a great bit of skill demonstrated earlier in the week by that US Air crew.
Last edited by Chock on Sun Jan 18, 2009 10:05 pm, edited 8 times in total.
Chock
Another interesting data brought to me by a friend Meteorology professor here in Brazil, (he got the METAR for the airfield and other nearby) and the weather didn't make the things easier for the crew of Flight 1549:
Cya
Edit: sorry, took the wrong day..., the right one is here (also not better, he had tailwind on ditching...):
Another interesting data brought to me by a friend Meteorology professor here in Brazil, (he got the METAR for the airfield and other nearby) and the weather didn't make the things easier for the crew of Flight 1549:
...
Cya
Edit: sorry, took the wrong day..., the right one is here (also not better, he had tailwind on ditching...):
KJFK 151951Z 33010KT 10SM BKN034 BKN055 M07/M14 A3024 SLP238
152051Z 01007KT 10SM BKN040 BKN250 M07/M15 A3026 SLP246;
KLGA 151951Z 34013KT 10SM BKN035 M06/M14 A3022 SLP234
152051Z 36008KT 10SM SCT044 M06/M15 A3025 SLP242
Last edited by Polewka on Sun Jan 18, 2009 8:27 am, edited 3 times in total.
René
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PT-REP
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@Chock
> Note that there's a big difference between some stats you'd read for this, because with a full load of baggage, px and fuel, the glide ratio will be affected.
sorry, that's incorrect.
the glide ratio is independent of the weight or mass of the aircraft. it only depends on its shape, and mostly on the shape of the wings, e.g. whether the flaps are deployed, the landing gear is down etc.
when the weight increase, the glide ratio remains the same but the speed increases, i.e. the descent speed increases, but the glide ratio (angle) is the same.
(up to a point, of course. if you reach speed where the aerodynamic rules start changing, e.g. close to mach speed, the glide ratio does change because the air flow around the wings gets disrupted).
The airbus A320 has a glide ratio around 17.
Boeing B707-320 19.4
Boeing 767-200 19.0
Douglas DC-8 17.9
Boeing 747-100 17.7
Douglas DC-10 17.7
Airbus A320 17.0
Lockeed Tristar L1011 17.0
Douglas DC-9 (1966) 16.5
Boeing B727-200 16.4
Douglas DC-3 14.7
deploying the flaps will decrease the glide ratio but also reduce noticeably the air speed, and that's very important (to have a slow speed) when you ditch. even with the flaps down, you can flair and do a soft landing. that's what the pilot did in the hudson. he had the flaps down.
> Note that there's a big difference between some stats you'd read for this, because with a full load of baggage, px and fuel, the glide ratio will be affected.
sorry, that's incorrect.
the glide ratio is independent of the weight or mass of the aircraft. it only depends on its shape, and mostly on the shape of the wings, e.g. whether the flaps are deployed, the landing gear is down etc.
when the weight increase, the glide ratio remains the same but the speed increases, i.e. the descent speed increases, but the glide ratio (angle) is the same.
(up to a point, of course. if you reach speed where the aerodynamic rules start changing, e.g. close to mach speed, the glide ratio does change because the air flow around the wings gets disrupted).
The airbus A320 has a glide ratio around 17.
Boeing B707-320 19.4
Boeing 767-200 19.0
Douglas DC-8 17.9
Boeing 747-100 17.7
Douglas DC-10 17.7
Airbus A320 17.0
Lockeed Tristar L1011 17.0
Douglas DC-9 (1966) 16.5
Boeing B727-200 16.4
Douglas DC-3 14.7
deploying the flaps will decrease the glide ratio but also reduce noticeably the air speed, and that's very important (to have a slow speed) when you ditch. even with the flaps down, you can flair and do a soft landing. that's what the pilot did in the hudson. he had the flaps down.
This is something we always try to explain non-glider pilots when answering one of the most asked question: "Why do you have water ballast?"loupiote wrote:when the weight increase, the glide ratio remains the same but the speed increases, i.e. the descent speed increases, but the glide ratio (angle) is the same.
Cya
René
Team Brasil
PT-REP
Team Brasil
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There was one succesfull field landing in 1991 by SAS and luckily nobody was killed. Bit more work for the crew than with gliders...
Wikipedia:
"On December 27, 1991, SAS flight 751, a MD-81, OY-KHO "Dana Viking" crash landed at Gottröra, Sweden. In the initial climb both engines ingested ice breaking loose from the wings, which had not been properly deiced before departure. The ice damaged the compressor blades causing compressor stall. The stall caused repeated engine surges that destroyed both engines, leaving the aircraft with no propulsion. The aircraft landed in a field and broke in three parts. No fire broke out and all aboard the plane survived. Captain Stefan G. Rasmussen was later decorated by the Danish Queen for his performance. This incident was mentioned on The History Channel's True Action Adventures episode "Against All Odds" which first aired in the United States on April 2, 1997."
Wikipedia:
"On December 27, 1991, SAS flight 751, a MD-81, OY-KHO "Dana Viking" crash landed at Gottröra, Sweden. In the initial climb both engines ingested ice breaking loose from the wings, which had not been properly deiced before departure. The ice damaged the compressor blades causing compressor stall. The stall caused repeated engine surges that destroyed both engines, leaving the aircraft with no propulsion. The aircraft landed in a field and broke in three parts. No fire broke out and all aboard the plane survived. Captain Stefan G. Rasmussen was later decorated by the Danish Queen for his performance. This incident was mentioned on The History Channel's True Action Adventures episode "Against All Odds" which first aired in the United States on April 2, 1997."
I can remember an "outlanding" of a Focker F-100 in a farm in 2002, due to fuel problems (leak). Plane was almost empty (24 pax) and (obviously) without fuel. Pilot landed with gear down (to absorb energy) and due to the light weight could land at 90-100kt using about 150m to stop. Only 1 fatality: a cow the plane hit during the landing...
Cya
Cya
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René
Team Brasil
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Interesting info on Hudson river landing...
Beim Zeitpunkt der Entscheidung hatte der Pilot
- Gleitwinkel 1:9 nach La Guardia (+180° Kurve)
- Gleitwinkel 1:17 nach Teterboro
- Gleitwinkel 1:23 zum Aufsetzpunkt im Hudson (incl. 2 mal 90° Kurven)
And another birs strike accident (flew to Paris last year with such Fokker):
Beim Zeitpunkt der Entscheidung hatte der Pilot
- Gleitwinkel 1:9 nach La Guardia (+180° Kurve)
- Gleitwinkel 1:17 nach Teterboro
- Gleitwinkel 1:23 zum Aufsetzpunkt im Hudson (incl. 2 mal 90° Kurven)
And another birs strike accident (flew to Paris last year with such Fokker):
Look the METAR of La Guardia, a few posts above, about 13kt (24km/h) from 340º I think (if I can decode it correctly).
Cya
P.S.: there is a video of the landing: http://video.nytimes.com/video/2009/01/ ... crash.html
Cya
P.S.: there is a video of the landing: http://video.nytimes.com/video/2009/01/ ... crash.html
René
Team Brasil
PT-REP
Team Brasil
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