Caribbean B738 at Georgetown on Jul 30, 2011, overran runway
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They could have achieved taxi speed well before the runway end, stowed reversers. F/O starts his after landing flow, selecting flaps up, then arriving at the turn-off point at runway end, find nil braking on a flooded, ungrooved runway.
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I have considerable NG time as part of my 30,000+ hours. I will assume there is HUD installed. There were massive failures-mechanical-electronic-intellectual, or simply horrible pilot skills. The -800 is an easy dream to fly, and 7,500ft is more than enough for it in almost any circumstances. The HUD makes it easy, even in bad weather.
“For info for non pilots reading the 738 can be stopped in approx 3000ft or 1000m after touchdown with flap 40 and autobrake max on a dry runway.”
Plus some small print.
Providing the aircraft crosses the threshold at Vref at 50 ft, touches down within 1000 ft (HUD / Autoland distances are longer), at the assumed touchdown speed (Vref -7?), and that the spoilers / airbrake / reversers are deployed without delay (1sec buffer) and maximum braking used until stopped. And that the tyres and brakes are in reasonable condition, the runway surface and friction characteristics are as assumed by the performance chart, that the wind is as reported, and no doubt a few other minor items such as aircraft weight and all systems remain serviceable.
In practice, because the aircraft and flying techniques do not meet the accuracies above, an aircraft operation is planned to stop within a certification distance consisting of a ‘theoretical’ minimum (similar to the above) plus a factored safety margin. However, even this distance is often exceeded in overrun accidents due to a combination of factors, dominated by false belief, assumption, inappropriate action, or unknown / unreliable values.
“… long runway ... plane off the end. How ? Why ?” Not even a HUD will answer those questions.
Plus some small print.
Providing the aircraft crosses the threshold at Vref at 50 ft, touches down within 1000 ft (HUD / Autoland distances are longer), at the assumed touchdown speed (Vref -7?), and that the spoilers / airbrake / reversers are deployed without delay (1sec buffer) and maximum braking used until stopped. And that the tyres and brakes are in reasonable condition, the runway surface and friction characteristics are as assumed by the performance chart, that the wind is as reported, and no doubt a few other minor items such as aircraft weight and all systems remain serviceable.
In practice, because the aircraft and flying techniques do not meet the accuracies above, an aircraft operation is planned to stop within a certification distance consisting of a ‘theoretical’ minimum (similar to the above) plus a factored safety margin. However, even this distance is often exceeded in overrun accidents due to a combination of factors, dominated by false belief, assumption, inappropriate action, or unknown / unreliable values.
“… long runway ... plane off the end. How ? Why ?” Not even a HUD will answer those questions.
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Missed Approach
Funny how everyone here is doing the "armchair" quarterback talking about what happened here. In the interview with the Captain he is talking about "saving lives"? Why didn't they do a go around and take a hold until the weather improved? I fly the 737-800 into 7000 foot runways and when it is wet we use Autobrake max and flaps 40. That equates to about a 138 knot ref speed roughly at 140,000 pound landing weight.
Lets wait and see the final report before jumping to conclusions!
If in doubt-Go Around! Thats what we train for in the "box" every 6 months!
Lets wait and see the final report before jumping to conclusions!
If in doubt-Go Around! Thats what we train for in the "box" every 6 months!
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There is a big difference between dry stopping distance, wet stopping distance, and flooded runway stopping distance. When downpours happen, the runway can have areas of ponding where the water may be more than 1/4"deep.
All bets are off then as braking may be close to zero.
Ask any pilot who has experienced it, it feels like ice, like someone gave the aircraft a big push in the back.
Add to that, the particular runway has "good" areas where constant use has left a relatively clean surface, but the lesser used areas have a kind of moss coating that is greasy and slippery. Once off the beaten track so to speak, braking can be very variable. The far (eastern) end of R 06 does not see much use other than the odd taxiing aircraft after a long roll-out.
There have been several attempts at improving the runway surface in the past,and its 10 years since I was last there, but the policy used to be, do not stow (idle) reverse until down to a walking pace.
The last 1500' of the runway was not a place to try to slow from, say, 60kts. Depending on conditions you might have your hands full.
I used to operate there in L-1011s and the "relax" point was not until down to a walking pace with a decent bit of runway left!
Being a wee bit long or a wee bit fast was not an option.
All bets are off then as braking may be close to zero.
Ask any pilot who has experienced it, it feels like ice, like someone gave the aircraft a big push in the back.
Add to that, the particular runway has "good" areas where constant use has left a relatively clean surface, but the lesser used areas have a kind of moss coating that is greasy and slippery. Once off the beaten track so to speak, braking can be very variable. The far (eastern) end of R 06 does not see much use other than the odd taxiing aircraft after a long roll-out.
There have been several attempts at improving the runway surface in the past,and its 10 years since I was last there, but the policy used to be, do not stow (idle) reverse until down to a walking pace.
The last 1500' of the runway was not a place to try to slow from, say, 60kts. Depending on conditions you might have your hands full.
I used to operate there in L-1011s and the "relax" point was not until down to a walking pace with a decent bit of runway left!
Being a wee bit long or a wee bit fast was not an option.
Last edited by ZQA297/30; 2nd Aug 2011 at 07:42.
but the policy used to be, do not stow (idle) reverse until down to a walking pace.
Just to qualify my comments I did say "dry runway" and "stopped within" - the latter obviously assumes that the aircraft is on the ground first and travelling at the recommended speed! 
You do wonder sometimes if the landing performance criteria for landing on wet runways is really up to it if "average" pilots are taking it off the end.
I don't suppose somewhere like Georgetown would be up to providing up to date braking action reports for the runway, especially when wet.
On a slightly different tack, many years ago in the USA they put experienced pilots in the simulator ostensibly for some other reason but then gave them a major failure close to v1 on a field length limited runway. Something like 75 % went off piste at the end which led to the conclusion that maybe the take off performance criteria needed re-assessing (not sure whether they did).
Maybe the same applies to landing on slick runways. Personally I never relax till the machine is stopped.
I don't suppose somewhere like Georgetown would be up to providing up to date braking action reports for the runway, especially when wet.
On a slightly different tack, many years ago in the USA they put experienced pilots in the simulator ostensibly for some other reason but then gave them a major failure close to v1 on a field length limited runway. Something like 75 % went off piste at the end which led to the conclusion that maybe the take off performance criteria needed re-assessing (not sure whether they did).
Maybe the same applies to landing on slick runways. Personally I never relax till the machine is stopped.
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Significant?
In the image here. http://www.pprune.org/rumours-news/4...ml#post6612041 For what it's worth, has anyone noticed and is it significant that the gouges in the grass show only TWO tracks for landing gear? Unless a main gear rolled over the nose gear track and obscured it, the nose gear wasn't on the ground at that point.
A Trini colleague walking past my desk pointed that out to me.
A Trini colleague walking past my desk pointed that out to me.
Azumi, the only two tracks are pretty correct IMHO cause they only depicted the 2 wheels on the right main landing gear.... the other 2 from the left one even the nose one, are out of photo range.
The nose ones due to the angle of the ravine, and according to some remaining speed, could be still out of ground contact (inertia too).
The nose ones due to the angle of the ravine, and according to some remaining speed, could be still out of ground contact (inertia too).
I'm puzzled by all the interpretations here
In the recently referenced Photos of tire tracks, my first reaction was the RH gear in an obviously foreshorten photo (and not nose and single tire track)
I have seen the absence in other accidents of LH gear track where the gear was sheared off in the first ditch after it left the runway, so is this the case here ?
I have heard that slap retractions are automatic if the hydraulics are breached, could this be part of the explanation. It seems like all the info that is needed to investigate this accident is available on-site, so why are we guessing?
In the recently referenced Photos of tire tracks, my first reaction was the RH gear in an obviously foreshorten photo (and not nose and single tire track)
I have seen the absence in other accidents of LH gear track where the gear was sheared off in the first ditch after it left the runway, so is this the case here ?
I have heard that slap retractions are automatic if the hydraulics are breached, could this be part of the explanation. It seems like all the info that is needed to investigate this accident is available on-site, so why are we guessing?
Here is a Thought:
I did my initial DC-10 type rating with AA at DFW. My simulator instructor was a truly wonderful character called Frank Meyers. I think Frank first flew the DC-2 when he joined AA.
On an early exercise in the sim he had us taking off from a runway at Waco, Texas which exactly met Performance A requirements. He failed No.3 just before V1 and we both ended up just off the end of the runway.
"Right gentlemen" said Frank "Let us have a look at your seat position".
Now I tended to have my seat quite low and I sat a bit back from the rudder pedals (just like I did in a sailplane). Frank pointed out that in this position I could only get my ankle muscles on to the brake pedals whereas if I sat a bit higher and a bit closer, I could bear down with my thigh muscles etc and get much more pressure on to the brake pedals and much quicker.
I have to say that I did not really feel comfortable with having my seat in this new suggested position but it worked really well. I was easily able to stop next time we tried the Waco trick and from that time on I taught a hell of a lot of young men Frank's trick.
Can YOU apply FULL BRAKING in your present position?
I did my initial DC-10 type rating with AA at DFW. My simulator instructor was a truly wonderful character called Frank Meyers. I think Frank first flew the DC-2 when he joined AA.
On an early exercise in the sim he had us taking off from a runway at Waco, Texas which exactly met Performance A requirements. He failed No.3 just before V1 and we both ended up just off the end of the runway.
"Right gentlemen" said Frank "Let us have a look at your seat position".
Now I tended to have my seat quite low and I sat a bit back from the rudder pedals (just like I did in a sailplane). Frank pointed out that in this position I could only get my ankle muscles on to the brake pedals whereas if I sat a bit higher and a bit closer, I could bear down with my thigh muscles etc and get much more pressure on to the brake pedals and much quicker.
I have to say that I did not really feel comfortable with having my seat in this new suggested position but it worked really well. I was easily able to stop next time we tried the Waco trick and from that time on I taught a hell of a lot of young men Frank's trick.
Can YOU apply FULL BRAKING in your present position?
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Why are we guessing?
Lomapaseo, "Why are we guessing?".
Well, were bored and have nothing better to do.
OK, that's not entirely correct. Some people like to "stir the pot", aka Boeing vs Airbus, ect.
Seriously, by nature we are an inquisitive lot. We search for answers, and barring that, propose some hypotheses of our own. Any "official" report is y-e-a-r-s down the road, yet "we" as a group, often flying these exact planes, have concerns. After every accident and mishap I have seen here, I put, or at least try to put myself into the operating pilots position, and mentally try to see what I would do. "Cargo Fire" over the North Pacific ( maybe get more life insurance ), ect. And NO, I can't exactly replicate what the pilot's in question actually do, as I don't have all the "facts" as "they" saw them. Maybe "they" saw a TRW on the LOC, and decided to cut in short, and didn't give themselves time to get stabilized, ect. I'm not saying that happened here, by any means, but these type of things do happen, and often the pilots aren't around to give their side of the story. More often than not they're dead. So, even though there are a lot of factors that I can't take into consideration, I try at least to learn from the experiences of others, in my own way.
Also, there is a wealth of information and experience in the heads of those on this forum. Personal experience flying the same type of plane, sometimes the exact plane. Personal experience flying into a particular field, airspace, ect. You can learn a lot, I almost always do.
You can also be misled. There are those on this forum that have NO credible experience, yet speak as if they do. How can you tell?. Often, you can't. I suspect they're are "news" types that are looking for a sensational pilot perspective. They may get it from a 16 year old kid, who flies an X-box, with a Forum tag of "OldSalty727". If that name exists I apologise in advance...
These are just my thoughts on "why we guess".
Well, were bored and have nothing better to do.
OK, that's not entirely correct. Some people like to "stir the pot", aka Boeing vs Airbus, ect.
Seriously, by nature we are an inquisitive lot. We search for answers, and barring that, propose some hypotheses of our own. Any "official" report is y-e-a-r-s down the road, yet "we" as a group, often flying these exact planes, have concerns. After every accident and mishap I have seen here, I put, or at least try to put myself into the operating pilots position, and mentally try to see what I would do. "Cargo Fire" over the North Pacific ( maybe get more life insurance ), ect. And NO, I can't exactly replicate what the pilot's in question actually do, as I don't have all the "facts" as "they" saw them. Maybe "they" saw a TRW on the LOC, and decided to cut in short, and didn't give themselves time to get stabilized, ect. I'm not saying that happened here, by any means, but these type of things do happen, and often the pilots aren't around to give their side of the story. More often than not they're dead. So, even though there are a lot of factors that I can't take into consideration, I try at least to learn from the experiences of others, in my own way.
Also, there is a wealth of information and experience in the heads of those on this forum. Personal experience flying the same type of plane, sometimes the exact plane. Personal experience flying into a particular field, airspace, ect. You can learn a lot, I almost always do.
You can also be misled. There are those on this forum that have NO credible experience, yet speak as if they do. How can you tell?. Often, you can't. I suspect they're are "news" types that are looking for a sensational pilot perspective. They may get it from a 16 year old kid, who flies an X-box, with a Forum tag of "OldSalty727". If that name exists I apologise in advance...
These are just my thoughts on "why we guess".
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B737 accident at CJIA
Maybe there was a problem with flaps, maybe it was not going to full 40. so the crew may have attempted to cycle it without success and in the confusion while on final approach may have inadvertently left the lever in the "UP" position with the flaps stuck partially extended. On short final the flap may have slowly started to follow the lever position (UP). This may not have been realised and the pilot (unknowingly) compensated by adding more power to maintain his speed, or the auto thrust system automatically doing so. This would explain the assumed somewhat long and fast landing, and no "Config" warnings since flaps may have been still partially extended (20 or so). On rollout the flaps continued to retract finally reaching full up position just before running off the runway……..plausible, since an inexperienced co-pilot may not necessarly pick this up...Captain flying
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That doesn't sound a very plausible scenario.
Firstly, it assumes a crew cycling the flaps while on approach - hardly conducive to a stabilized approach.
Secondly, if they were approaching with the flaps not fully extended and hoping that they would extend somehow, then they should have been considering the flaps failed landing distance - which since they overran it seems unlikely.
Had the scenario of flaps retracting during the final stages of the approach been possible, then there wouldn't have been a need to add power - if anything, the cleaned up config would need less power. It'd also be needing more AOA, though - something you'd think might be noticeable.
Depending on the system architecture, having the handle in the wrong position might be the input to a config warning, rather than the surface itself. Either are plausible. Would need to know the system specifics to know if thats a plausible suggestion.
Firstly, it assumes a crew cycling the flaps while on approach - hardly conducive to a stabilized approach.
Secondly, if they were approaching with the flaps not fully extended and hoping that they would extend somehow, then they should have been considering the flaps failed landing distance - which since they overran it seems unlikely.
Had the scenario of flaps retracting during the final stages of the approach been possible, then there wouldn't have been a need to add power - if anything, the cleaned up config would need less power. It'd also be needing more AOA, though - something you'd think might be noticeable.
Depending on the system architecture, having the handle in the wrong position might be the input to a config warning, rather than the surface itself. Either are plausible. Would need to know the system specifics to know if thats a plausible suggestion.