By: wawkrk
- 6th August 2007 at 17:08Permalink- Edited 1st January 1970 at 01:00
You are describing the Jakarta incident unless you are confused with the Air Canada 767 incident on 23/7/83 where the plane glided 45 miles from 35,000 feet to land at Gimli.
No, I remember very clearly reading the story as told by the F/O or could it have been a Flight Engineer then.
He spoke about the grinding noises coming from the Rollers as they tried to re-start one by one.
I think BA had to fly in support equipment because of the primitive facilities at the African airfield. Even no steps to leave the aircraft.
The passengers formed a club afterwards to keep in touch.
The whole incident was miraculous and a huge credit to the crew that they survived.I am sure I did not mix it with Jakarta where the facilities are not so bad I remember.
I am familiar with the Gimli incident where they landed at the race track.
By: Newforest
- 6th August 2007 at 17:27Permalink- Edited 1st January 1970 at 01:00
You are describing the Jakarta incident unless you are confused with the Air Canada 767 incident on 23/7/83 where the plane glided 45 miles from 35,000 feet to land at Gimli.
No, I remember very clearly reading the story as told by the F/O or could it have been a Flight Engineer then.
He spoke about the grinding noises coming from the Rollers as they tried to re-start one by one.
I think BA had to fly in support equipment because of the primitive facilities at the African airfield. Even no steps to leave the aircraft.
The passengers formed a club afterwards to keep in touch.
I cannot find any other incident with British Airways in Africa, hope someone else can provide further information if it happened.
By: Levsha
- 6th August 2007 at 19:28Permalink- Edited 1st January 1970 at 01:00
I've never heard about the second BA flight which lost all engines over Africa, but I have heard about a similar incident regarding a KLM Boeing 743 losing all engines after flying over an erupting volcano in Alaska sometime in the late 1980s.
I believe it went into something of a steep dive upon losing power but recovered power after leaving the dust cloud.
By: wawkrk
- 6th August 2007 at 20:43Permalink- Edited 1st January 1970 at 01:00
I seem to remember the incident over Africa was caused by Mt.St.Helens in Washington state. The massive explosion sent out a volcanic dust cloud which circled the earth. Even cars in the UK were covered in the red dust.
This happened in 1980.
wawkrk
By: wawkrk
- 6th August 2007 at 20:54Permalink- Edited 1st January 1970 at 01:00
I must have a vivid imagination.
Can only find incidents involving a DC-8 and a B727 connected with Mt.St.Helens.I was so certain about it but obviously wrong.
wawkrk
By: bexWH773
- 6th August 2007 at 21:23Permalink- Edited 1st January 1970 at 01:00
I must have a vivid imagination.
Can only find incidents involving a DC-8 and a B727 connected with Mt.St.Helens.I was so certain about it but obviously wrong.
wawkrk
Although I am well known over in historic for my er Canberra fetish (as I was so informed today LoL) I also happen to like in a big way 2 of Boeings Big Birds, 747 - xxx & the 707 - xxx and I thought Id studied all the 747 incidents and I was beginning to wonder if Id missed one. Glad its cleared up at last. Bex
By: Schorsch
- 6th August 2007 at 21:24Permalink- Edited 1st January 1970 at 01:00
FLYBYDONNI
It wouldn't be able to glide 1200 miles, that's here to North Africa
If an a/c wanted to glide for best range then it will fly at the best lift:drag ratio which is Vimd or velocity for minimum drag, if we remain here the glide angle will remain the same, however if the a/c is heavy then Vimd will be higher by a factor proportional to the square root of the weight increase.
So if we increase speed to a new Vimd the only thing that changes is the time in the air, you should maintain the same glide angle and the same distance covered on the ground, you'll just meet the ground a bit quicker.
This is for still wind conditions, if we had a headwind then the best result would come by increasing your speed, the opposite for a tailwind.
There are graphs to work out the best speed to fly in certain conditions.
The 744 as with any plane will have a glide ratio worked out from the above, it could be something like 1:10, this means for every 1,000ft lost in height it will travel 10,000ft horizontally, again if you do the maths 33,000ft will give a Horizontal distance of 330,000ft which works out about 63 miles in still wind conditions.
Hope this helps too
Dean
I'm totally confused as to how you can have a higher rate of decent but have the same glide angle and travel the same distance. Sorry, Deano, my poor little brain isn't understanding!
Is there any way reply 9 can be explained in a different way so that stupid and simple people like me can vaguely comprehend it? :confused:
Paul
The weight determines the lift coefficient. Depending on that the optimum speed changes. Actually, a very light aircraft would achieve a less desirable glide ratio than a heavy one, although the lighter one has overally less drag.
The problem with glide ratios is that it puts lift (=weight in unaccelerated flight) in relation to drag.
That is basically what Deano said: To have more lift at best lift coefficent the speed has to be increased. The glide ratio will stay the same, but with the higher speed the vertical speed is higher.
By: Deano
- 7th August 2007 at 00:10Permalink- Edited 1st January 1970 at 01:00
Schorsch has explained it but Paul if you visualise a right angled triangle as pictured below, then look at the formula of
Vimd or minimum drag speed (which is the speed we have to fly at for best glide ratio) will be higher by a factor proportional to the square root of the weight increase.
This formula is basically saying that if we increase our weight then to obtain the best glide ratio or Vimd (minimum drag speed), we have to increase our speed by a factor proportional to the weight increase. Remember regardless of what our Vimd speed is we will still travel the same distance specified on that triangle provided we glide at that new Vimd speed, so the glide angle as shown on the triangle stays the same, as does the distance, we will just travel along the path of the glide path line on the triangle faster, meaning we will have a higher rate of descent.
Does this make it any clearer? (cos I'm confusing myself now LOL)
By: Schorsch
- 7th August 2007 at 06:53Permalink- Edited 1st January 1970 at 01:00
I always like to use formulas! :D
CD = CD0 + f*CA²
(f is a factor, which is in our region of interest constant)
So basically:
CD ~ CA²
or in words
drag is proportional to the square of lift.
CA = W/(rho*v²*S)
S: wing area (constant), rho: air density (independent of weight), v: airspeed, W: weight
W1=500klbs (which is something like the lowest possible flying weight of a B747).
W2 = 850klbs (which is something like maximum weight for any B747-200 at altitude)
rho=.5 kg/m³ (~28000ft)
S = 5500ft²
v: 250KIAS = M0.66 = 200m/s TAS
CA(W1=500klbs) = 0.45
CA(W2=850klbs) = 0.77
When you look at the graph above, you'll see that Ca of W2 is actually outside the y-axis limit. I actually think it must be close to buffet onset boundary.
If we increase airspeed to 290KIAS, we have for W2:
CA = .57 with M=0.77.
Posts: 170
By: wawkrk - 6th August 2007 at 17:08 Permalink - Edited 1st January 1970 at 01:00
You are describing the Jakarta incident unless you are confused with the Air Canada 767 incident on 23/7/83 where the plane glided 45 miles from 35,000 feet to land at Gimli.
No, I remember very clearly reading the story as told by the F/O or could it have been a Flight Engineer then.
He spoke about the grinding noises coming from the Rollers as they tried to re-start one by one.
I think BA had to fly in support equipment because of the primitive facilities at the African airfield. Even no steps to leave the aircraft.
The passengers formed a club afterwards to keep in touch.
The whole incident was miraculous and a huge credit to the crew that they survived.I am sure I did not mix it with Jakarta where the facilities are not so bad I remember.
I am familiar with the Gimli incident where they landed at the race track.
Posts: 8,846
By: Newforest - 6th August 2007 at 17:27 Permalink - Edited 1st January 1970 at 01:00
I cannot find any other incident with British Airways in Africa, hope someone else can provide further information if it happened.
Posts: 2,814
By: Levsha - 6th August 2007 at 19:28 Permalink - Edited 1st January 1970 at 01:00
I've never heard about the second BA flight which lost all engines over Africa, but I have heard about a similar incident regarding a KLM Boeing 743 losing all engines after flying over an erupting volcano in Alaska sometime in the late 1980s.
I believe it went into something of a steep dive upon losing power but recovered power after leaving the dust cloud.
Posts: 170
By: wawkrk - 6th August 2007 at 20:43 Permalink - Edited 1st January 1970 at 01:00
I seem to remember the incident over Africa was caused by Mt.St.Helens in Washington state. The massive explosion sent out a volcanic dust cloud which circled the earth. Even cars in the UK were covered in the red dust.
This happened in 1980.
wawkrk
Posts: 170
By: wawkrk - 6th August 2007 at 20:54 Permalink - Edited 1st January 1970 at 01:00
I must have a vivid imagination.
Can only find incidents involving a DC-8 and a B727 connected with Mt.St.Helens.I was so certain about it but obviously wrong.
wawkrk
Posts: 1,060
By: bexWH773 - 6th August 2007 at 21:23 Permalink - Edited 1st January 1970 at 01:00
Although I am well known over in historic for my er Canberra fetish (as I was so informed today LoL) I also happen to like in a big way 2 of Boeings Big Birds, 747 - xxx & the 707 - xxx and I thought Id studied all the 747 incidents and I was beginning to wonder if Id missed one. Glad its cleared up at last. Bex
Posts: 3,718
By: Schorsch - 6th August 2007 at 21:24 Permalink - Edited 1st January 1970 at 01:00
The weight determines the lift coefficient. Depending on that the optimum speed changes. Actually, a very light aircraft would achieve a less desirable glide ratio than a heavy one, although the lighter one has overally less drag.
The problem with glide ratios is that it puts lift (=weight in unaccelerated flight) in relation to drag.
That is basically what Deano said: To have more lift at best lift coefficent the speed has to be increased. The glide ratio will stay the same, but with the higher speed the vertical speed is higher.
[ATTACH]156013[/ATTACH]
This is the drag over lift for the B747-200.
Posts: 9,823
By: J Boyle - 6th August 2007 at 22:09 Permalink - Edited 1st January 1970 at 01:00
The only transport that can glide 1200 miles is the Space Shuttle.:D
Posts: 2,623
By: Deano - 7th August 2007 at 00:10 Permalink - Edited 1st January 1970 at 01:00
Schorsch has explained it but Paul if you visualise a right angled triangle as pictured below, then look at the formula of
Vimd or minimum drag speed (which is the speed we have to fly at for best glide ratio) will be higher by a factor proportional to the square root of the weight increase.
This formula is basically saying that if we increase our weight then to obtain the best glide ratio or Vimd (minimum drag speed), we have to increase our speed by a factor proportional to the weight increase. Remember regardless of what our Vimd speed is we will still travel the same distance specified on that triangle provided we glide at that new Vimd speed, so the glide angle as shown on the triangle stays the same, as does the distance, we will just travel along the path of the glide path line on the triangle faster, meaning we will have a higher rate of descent.
Does this make it any clearer? (cos I'm confusing myself now LOL)
Dean
Posts: 3,718
By: Schorsch - 7th August 2007 at 06:53 Permalink - Edited 1st January 1970 at 01:00
I always like to use formulas! :D
CD = CD0 + f*CA²
(f is a factor, which is in our region of interest constant)
So basically:
CD ~ CA²
or in words
drag is proportional to the square of lift.
CA = W/(rho*v²*S)
S: wing area (constant), rho: air density (independent of weight), v: airspeed, W: weight
W1=500klbs (which is something like the lowest possible flying weight of a B747).
W2 = 850klbs (which is something like maximum weight for any B747-200 at altitude)
rho=.5 kg/m³ (~28000ft)
S = 5500ft²
v: 250KIAS = M0.66 = 200m/s TAS
CA(W1=500klbs) = 0.45
CA(W2=850klbs) = 0.77
When you look at the graph above, you'll see that Ca of W2 is actually outside the y-axis limit. I actually think it must be close to buffet onset boundary.
If we increase airspeed to 290KIAS, we have for W2:
CA = .57 with M=0.77.