MK Airlines B747 crash at Halifax
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The inner bogies are certainly well back of the outer bogies but I haven't been able to find a scale drawing of the undercarriage of a B-747 Classic.
Plate 11 in D P Davies's "Handling the Big Jets" (3rd ed) is very instructive. It shows a 747 Classic undergoing high-AOA takeoff tests with a deliberate tailscrape. The hindmost four wheels of the inner (centre) bogies are the only wheels in contact with the runway as the extreme tail scrapes the ground.
Rockhound
Plate 11 in D P Davies's "Handling the Big Jets" (3rd ed) is very instructive. It shows a 747 Classic undergoing high-AOA takeoff tests with a deliberate tailscrape. The hindmost four wheels of the inner (centre) bogies are the only wheels in contact with the runway as the extreme tail scrapes the ground.
Rockhound
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I read the early pages of this thread some time ago, came back to the thread today. Could not be bothered with the intervening pages, no doubt much of the same. Found the early pages depressing in that almost all contributors knew little about flying and clearly f...al about the the 747, despite quoting a "747 pilot says" his quoted sayings being mainly rubbish.
Tailstrikes are almost unknown on T/O, a possible hazard on landing if one is not careful with the AOA (means Angle of Attack or Pitch Attitude for many contributors who lack this this basic knowledge) on landing above 12 degrees is really pushing your luck. .
Boeing at the bequest of BA designed an over- rotation warning for TO, installed nowhere else and later abandoned
Now I see people drawing maps on this thread. The Canadian Accident investigators are internationally acknowledeged as being amongst the best in the world. Just wait for their report, meanwhile don't embarrass yourself by trying by guess the out come
If I was sober, I could go on for hours, but trying to type accurately is becoming tedious.
It is threads like this, and there are many of them, that make PPrune look faintly ridiculous.
Some time ago there was a pompous thread, with which at the time I did not agree, that said make this forum for real airline professional pilots only. I now think that maybe he had a point.
Time for bed for me.
rockhound
The dimensions of the 747 undercarriage are laid out on the dimensions page of the AFM.
Tailstrikes are almost unknown on T/O, a possible hazard on landing if one is not careful with the AOA (means Angle of Attack or Pitch Attitude for many contributors who lack this this basic knowledge) on landing above 12 degrees is really pushing your luck. .
Boeing at the bequest of BA designed an over- rotation warning for TO, installed nowhere else and later abandoned
Now I see people drawing maps on this thread. The Canadian Accident investigators are internationally acknowledeged as being amongst the best in the world. Just wait for their report, meanwhile don't embarrass yourself by trying by guess the out come
If I was sober, I could go on for hours, but trying to type accurately is becoming tedious.
It is threads like this, and there are many of them, that make PPrune look faintly ridiculous.
Some time ago there was a pompous thread, with which at the time I did not agree, that said make this forum for real airline professional pilots only. I now think that maybe he had a point.
Time for bed for me.
rockhound
The dimensions of the 747 undercarriage are laid out on the dimensions page of the AFM.
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Are you sure these ruts are 747 wheel tracks?
1. To the naked eye they are constant depth. Imagine the impact of the landing gear at about 150 knots - I think the divot would be somewhat larger.
2. They appear to be at a slight angle to each other.
3. The berm is basically undamaged except for the lights.
4. There are four similar ruts towards the right hand end of the berm - but the spacing is wrong for these to be caused by the other pair of bogies.
TP
1. To the naked eye they are constant depth. Imagine the impact of the landing gear at about 150 knots - I think the divot would be somewhat larger.
2. They appear to be at a slight angle to each other.
3. The berm is basically undamaged except for the lights.
4. There are four similar ruts towards the right hand end of the berm - but the spacing is wrong for these to be caused by the other pair of bogies.
TP
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TyroP,
No, I, for one, am not sure, hence my earlier questions. But if the aircraft didn't make those tracks, what did? We know, from what the TSB has released, that the tail section struck the berm, so the undercarriage couldn't have been very high above the ground. The wheels must have been spinning at a great rate, which would cushion the impact with the berm, wouldn't it? And looking at that photo in Davies's book (I don't have a scanner so cannot post a copy. Could someone do so, please?), one can imagine most of the wheels clearing the berm. Still, I admit it is difficult to understand why the berm, if it was struck by the tail section of the aircraft, appears relatively undamaged. Also, why do the (tire?) tracks (appear to) begin only just in front of the berm?
Rockhound
No, I, for one, am not sure, hence my earlier questions. But if the aircraft didn't make those tracks, what did? We know, from what the TSB has released, that the tail section struck the berm, so the undercarriage couldn't have been very high above the ground. The wheels must have been spinning at a great rate, which would cushion the impact with the berm, wouldn't it? And looking at that photo in Davies's book (I don't have a scanner so cannot post a copy. Could someone do so, please?), one can imagine most of the wheels clearing the berm. Still, I admit it is difficult to understand why the berm, if it was struck by the tail section of the aircraft, appears relatively undamaged. Also, why do the (tire?) tracks (appear to) begin only just in front of the berm?
Rockhound
There seems to be a debris field (or possibly absorbent material) before the berm that may be covering a longer track before the berm.
Perhaps instead of lights on the top of the berm, it's a localiser array.
Earlier in this thread is an observation that this end of the runway is not visible from the opposite end which may explain why the localiser array had to be elevated.
Perhaps instead of lights on the top of the berm, it's a localiser array.
Earlier in this thread is an observation that this end of the runway is not visible from the opposite end which may explain why the localiser array had to be elevated.
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>The aviation industry teaches us to be go -oriented at high >speed.
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>>That is exactly why these pilots died in this particular accident, >>because they were go-oriented at V1, at the end of a chain of >>events.
Perhaps this go-oriented thinking did end up making this situation worse, but this type of thinking likely prevents many more accidents due to high speed overruns from happening. Accidents that we are never aware of because they never happened.
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>>That is exactly why these pilots died in this particular accident, >>because they were go-oriented at V1, at the end of a chain of >>events.
Perhaps this go-oriented thinking did end up making this situation worse, but this type of thinking likely prevents many more accidents due to high speed overruns from happening. Accidents that we are never aware of because they never happened.
Here's a link to an airliners.net photograph showing the relative position of inboard and outboard gear assemblies. When unloaded the outboard gear hangs lower but the inboard is further back.
With apologies aforehand for my armchair analysis I am going to stick my neck out a bit further and make a guess as to what happens when the centre gear of a fully loaded 747 suddenly encounters a steep gradient which I'm estimating at 4-5m high and very solid. The gear assembly fully compresses and then punches up into the aircraft up just aft of centre, breaking its back. The rear section snaps down and on impact with the object, separates from the front but is carried forward by momentum. All this happens in less than a second.
landing 747-200
With apologies aforehand for my armchair analysis I am going to stick my neck out a bit further and make a guess as to what happens when the centre gear of a fully loaded 747 suddenly encounters a steep gradient which I'm estimating at 4-5m high and very solid. The gear assembly fully compresses and then punches up into the aircraft up just aft of centre, breaking its back. The rear section snaps down and on impact with the object, separates from the front but is carried forward by momentum. All this happens in less than a second.
landing 747-200
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Punkalouver, I basically agree with you. However it appears that in this accident, the normal go response to V1, that works 99% of the time, may have failed them in this instance, mainly due to the fact that they were some distance further down the runway than originally intended, when they arrived at V1.
On most takeoffs (especially field limited takeoffs), you have to reach Vr sometime after you reach V1. In this case it looks like they came very close to making Vr at the berm (well past the end of the runway), but not quite.
Again, I think the go-no-go decision a pilot is forced to make regarding V1, at the point when these pilots discovered that they reached V1 at reduced power, is going to be a 50-50 guess at best. The reason is because too much information (i.e. runway distance remaining, time to spool up the engines to max power from a lower power setting, time remaining to accelerate to Vr, runway distance to cover to reach Vr, etc.) has to be processed in too short a period of time to easily make the correct decision. It's also possible that neither decision will save the day, especially if you're just too far down the runway at the problem discovery time.
Again, the best solution is to avoid getting into this situation in the first place (arriving at V1 too late), and this is the primary lesson that I'm taking home from this accident.
On most takeoffs (especially field limited takeoffs), you have to reach Vr sometime after you reach V1. In this case it looks like they came very close to making Vr at the berm (well past the end of the runway), but not quite.
Again, I think the go-no-go decision a pilot is forced to make regarding V1, at the point when these pilots discovered that they reached V1 at reduced power, is going to be a 50-50 guess at best. The reason is because too much information (i.e. runway distance remaining, time to spool up the engines to max power from a lower power setting, time remaining to accelerate to Vr, runway distance to cover to reach Vr, etc.) has to be processed in too short a period of time to easily make the correct decision. It's also possible that neither decision will save the day, especially if you're just too far down the runway at the problem discovery time.
Again, the best solution is to avoid getting into this situation in the first place (arriving at V1 too late), and this is the primary lesson that I'm taking home from this accident.
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With all of Canada's open space..what a stupid place to build an earth wall.Surely frangible ILS antenna posts would be better.I think Sharjah should have invested in a bulldozer to flatten the over-runs of its airfield too.It might save lives.
But then it always amazes me that airport planners go around finding big flat open spaces,and the first thing they do is build an enormously tall tower.What's LHR's new one going to be..300feet?!You wouldn't get me up in that thing for love nor money.
But then it always amazes me that airport planners go around finding big flat open spaces,and the first thing they do is build an enormously tall tower.What's LHR's new one going to be..300feet?!You wouldn't get me up in that thing for love nor money.
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broad reach ….. when the centre gear of a fully loaded 747 suddenly encounters a steep gradient which I'm estimating at 4-5m high and very solid. The gear assembly fully compresses and then punches up into the aircraft up just aft of centre, breaking its back. The rear section snaps down and on impact with the object, separates from the front but is carried forward by momentum. All this happens in less than a second. ………
TyroPicard 2. They appear to be at a slight angle to each other.
TyroPicard 2. They appear to be at a slight angle to each other.
http://www.amazon.com/gp/product/cus...Fencoding=UTF8
http://www.amazon.com/gp/product/cus...Fencoding=UTF8
The corresponding photo on the cover of the -200 book does not give such a good view.
It seems almost impossible that the aircraft could have been at such a nose-up attitude high that the front bogies left no sign of impact on a berm 4 m high. But how else can you explain what the photo of the berm shows?
Question: Assuming it was at such a nose-up angle, and nearly at flying speed (and therefore on the ground), what would you expect to see in the way of tracks before the berm?
On the flat ground before the berm I suggest you would see very little because there was little load on the ground - the plane was almost flying. As the leading wheels of the trailing bogies start up the slope of the berm I would expect a large load on the rear wheels and for the tracks to start a bogie length before the slope of the berm starts.
I suggest that is exactly what the photo shows.
The slight divergence of the wheel tracks as they go up the berm might be associated with the progressive collapse of the undercarriage as suggested by broad reach.
Cheers,
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Even if you point a 747 vertically upwards the wing gear is nowhere near 4 metres above the body gear. From the side, on the ground, each pair of bogies looks like this: OOOO no overlap but not much of a fore/aft gap.
And at 150 kts flying basically level they would make a big hole, not dainty little 3-inch ruts like a Chelsea tractor might.
The Canadians state "the tail hit the berm". No mention of gear. At a high angle of attack, tail close to the ground, I reckon the gear would clear the berm.
TP
And at 150 kts flying basically level they would make a big hole, not dainty little 3-inch ruts like a Chelsea tractor might.
The Canadians state "the tail hit the berm". No mention of gear. At a high angle of attack, tail close to the ground, I reckon the gear would clear the berm.
TP
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If it was 12 hrs 6 min from TAKE OFF in Lux, it must have been at least an hour and probably more from report. Is it really legal to roster a 21 hour (at least!) duty even using Ghana regulations??
it does at least go some way to explain how some of the problems detailed on the other thread could have arisen -and dare I say it, how MK have crashed no fewer than three other heavies in the last 12 years
it does at least go some way to explain how some of the problems detailed on the other thread could have arisen -and dare I say it, how MK have crashed no fewer than three other heavies in the last 12 years
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Just a post to say thanks to PickyPerkins for the detailed analysis of the wheel ruts in the photo of the berm. It was an excellent presentation which I think has led to some interesting further analysis about this plane's position as it passed over/through the berm.
Unlike some others, I think that this kind of theory exploration is an excellent topic for a forum such as this. There are some first class aviation brains who have contributed to this thread. It would not surprise me at all if The Canadian Transportation Safety Board's enquiry into this crash itself might develop some new lines of reasoning as a result of reading some of the informative posts on this thread.
Unlike some others, I think that this kind of theory exploration is an excellent topic for a forum such as this. There are some first class aviation brains who have contributed to this thread. It would not surprise me at all if The Canadian Transportation Safety Board's enquiry into this crash itself might develop some new lines of reasoning as a result of reading some of the informative posts on this thread.
Last edited by McGinty; 2nd Dec 2004 at 20:54.
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Well, for starters, ShotOne, it may well have been.
The FAA for example under 14CFR121, allows a 24 hours duty period for an augmented crew...2 Captains, one First Officer, two Flight Engineers.
Just off hand I can't remember the allowed number of landings, but if memory serves correctly, 4.
I personally know of only one crew that was stretched to this limit, and this was due to MX.
But, to actually roster as a matter of course, seems foolhardy to me.
Twist the tail of the tiger....expect to be severely bitten.
The FAA for example under 14CFR121, allows a 24 hours duty period for an augmented crew...2 Captains, one First Officer, two Flight Engineers.
Just off hand I can't remember the allowed number of landings, but if memory serves correctly, 4.
I personally know of only one crew that was stretched to this limit, and this was due to MX.
But, to actually roster as a matter of course, seems foolhardy to me.
Twist the tail of the tiger....expect to be severely bitten.
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TyroPicard Even if you point a 747 vertically upwards the wing gear is nowhere near 4 metres above the body gear. From the side, on the ground, each pair of bogies looks like this: OOOO no overlap but not much of a fore/aft gap.
http://www.airliners.net/open.file/664530/m
Below a photo of all fully extended bogies is superimposed on the photo of the berm. The width of the tires, the spacing between the wheels on each bogie, and the spacing between the bogies all match. I have no answer as to why the outer bogie ruts do not show up
Cheers,
Perhaps you're right, Picky. But, just perhaps, there's a little window of AOA where the outboard gear is dangling but still a foot or so above the inboard gear which itself, along with the tail, is only a foot or so off. Just think what might be anybody's gut instinct as the berm looms up in the lights. Do absolutely anything to get over it, right? i.e. pull up even more.
Assume for a minute that might have happened. Desperate yes, but by this time could you expect anything but? It would get the nose and the wings up higher but it would put the tail down, right? And it would put the inboard gear, which is slightly aft of the centre of lift, down as well, right into the berm.
There have been a few posts that seem to suggest the impact of the rear fuselage with the berm should have destroyed the berm. I've forgotten most (sorry, all) of my physics but there are many more tons of earth and concrete in that berm than there are in the tail of an aluminium 747. An aircraft which, granted, can take a lot of punishment but of an entirely different sort.
You whack that centre gear up into the fuselage on a protrusion like the berm and you break the aircraft's back. The rear, with elevators still trying to raise the nose, pressing the tail down, hits the berm and that's it.
This was the result of actions taken or not taken minutes before, as the aircraft prepared for takeoff. I humbly submit that the real issue, and whatever lessons are to be learned, lies in those actions, not in all this discussion of the berm which, as I think I mentioned earlier could, at other airports around the world, well have been houses.
P.S. something that occurred to me a few days ago but thought not worth mentioning. If you're sluggishly airborn and seriously needing speed, what do you do? Get the gear up!? Suppose retraction was initiated before the end of the runway. How does a -200's gear cycle in retraction? Do the outboard bogies fold in first or do they all retract simultaneously? Do the outboard bogies first - or simultaneously - correct the angle of the dangle, so to speak, to bring the wheels into the wells? I am going wildly off track perhaps but if I were designing undercarriage I would try to ensure that the "gear up" sequence" first reduced drag by aligning front and rear wheel sets in the bogie before folding them up into the wing.
IF that's the case, it might be an explanation for the lack of outboard gear tracks up the berm.
Assume for a minute that might have happened. Desperate yes, but by this time could you expect anything but? It would get the nose and the wings up higher but it would put the tail down, right? And it would put the inboard gear, which is slightly aft of the centre of lift, down as well, right into the berm.
There have been a few posts that seem to suggest the impact of the rear fuselage with the berm should have destroyed the berm. I've forgotten most (sorry, all) of my physics but there are many more tons of earth and concrete in that berm than there are in the tail of an aluminium 747. An aircraft which, granted, can take a lot of punishment but of an entirely different sort.
You whack that centre gear up into the fuselage on a protrusion like the berm and you break the aircraft's back. The rear, with elevators still trying to raise the nose, pressing the tail down, hits the berm and that's it.
This was the result of actions taken or not taken minutes before, as the aircraft prepared for takeoff. I humbly submit that the real issue, and whatever lessons are to be learned, lies in those actions, not in all this discussion of the berm which, as I think I mentioned earlier could, at other airports around the world, well have been houses.
P.S. something that occurred to me a few days ago but thought not worth mentioning. If you're sluggishly airborn and seriously needing speed, what do you do? Get the gear up!? Suppose retraction was initiated before the end of the runway. How does a -200's gear cycle in retraction? Do the outboard bogies fold in first or do they all retract simultaneously? Do the outboard bogies first - or simultaneously - correct the angle of the dangle, so to speak, to bring the wheels into the wells? I am going wildly off track perhaps but if I were designing undercarriage I would try to ensure that the "gear up" sequence" first reduced drag by aligning front and rear wheel sets in the bogie before folding them up into the wing.
IF that's the case, it might be an explanation for the lack of outboard gear tracks up the berm.
Last edited by broadreach; 2nd Dec 2004 at 21:05.
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"..... not in all this discussion of the berm which, as I think I mentioned earlier could, at other airports around the world, well have been houses"
BR, my local strip is 10,000 feet long and 300 feet from the 06 end the builders left a 12ft high solid bank of rock
..... travel a further 50 feet and the ground flattens out and remains suitable for a "very serious crash over-run" if it was ever required for a couple of thousand feet minimum! ...... but you would never get there! 
..... the 12ft high rock bank would kill you first ...... To this day, I've never understood why they left the rock there 
If you have lots of open space why on earth leave an imoveable obstacle at the end of the runway?
BR, my local strip is 10,000 feet long and 300 feet from the 06 end the builders left a 12ft high solid bank of rock
..... travel a further 50 feet and the ground flattens out and remains suitable for a "very serious crash over-run" if it was ever required for a couple of thousand feet minimum! ...... but you would never get there! ..... the 12ft high rock bank would kill you first ...... To this day, I've never understood why they left the rock there If you have lots of open space why on earth leave an imoveable obstacle at the end of the runway?