Mach overspeed 737-800
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One demotion and one suspension is a bit hard for a MMO incursion, what is MMO? it is simply 90% of demonstrated MAX speed achieved during to test flights and for which the aircraft is certified, in other word no big deal, did you exceed the Max certified MMO? NO you did not , so what is the issue?
One demotion and one suspension is a bit hard for a MMO incursion, what is MMO? it is simply 90% of demonstrated MAX speed achieved during to test flights and for which the aircraft is certified, in other word no big deal, did you exceed the Max certified MMO? NO you did not , so what is the issue?
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In China,
First, it is good of you to post your experience. I'm sure many will learn from it
My experience is Classic, so I should think we have more drag and slow quicker than the NG of which I have no experience. But maybe the similarities are similar enough. Also I think Kosmo is quoting a company manual.
Did you exec the changes? One can get massive profile changes.
Yes, but even getting to 6,000 fpm hasn't presented us with problems. So that I doubt that in it's self is a problem.
I have found that one needs to assert a zero pitch attitude to get any kind of meaningful decellerration near the limit. As others have said, the most expeditious and easiest way to accomplish this is gentle back pressure on the column to trip it into CWS P. My previous near MMO incursion I disconnected completely and although not an issue in anyway, required more chatter, more work generally so I don't see what is going to be gained by fully disconnecting the A/P.
On the Classic, 3400 fpm is not enough to decelerate unless you intervene much earlier.
Unless you exec'd your FMC changes I don't think the FMC would calculate such an abrupt profile change.
In your defence the PF did extend the speedbrake but it was ineffective. Also, there is no specific guidance on what kind of pitch attitude or V/S would actually result in adequate decellaration. So you effectively had to suck it and see from which a minor incursion doesn't seem to be too bad a result. I would have done it differently, but then my company is a strong advocate of disconnecting the A/P if it's performance in insufficient. What is your company's written policy and how strongly is this reinforced in sim and line checks?
First, it is good of you to post your experience. I'm sure many will learn from it
My experience is Classic, so I should think we have more drag and slow quicker than the NG of which I have no experience. But maybe the similarities are similar enough. Also I think Kosmo is quoting a company manual.
I then entered some descent information on the FMC.
At 40 seconds after beginning decent vertical speed was 5400 feet/Min (we know its fast)
Then the aircraft started to pitch up, but due to momentum the air speed still increased, but at a slower rate.
t 50 seconds after the decent began , at 29740 feet we had the Mach over speed warning sound at Mach 8.26, with a decent rate of 3400 feet per minute
We think the wind change contributed quite a lot to the overall situation.
In your defence the PF did extend the speedbrake but it was ineffective. Also, there is no specific guidance on what kind of pitch attitude or V/S would actually result in adequate decellaration. So you effectively had to suck it and see from which a minor incursion doesn't seem to be too bad a result. I would have done it differently, but then my company is a strong advocate of disconnecting the A/P if it's performance in insufficient. What is your company's written policy and how strongly is this reinforced in sim and line checks?
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VNAV PTH is not the Devil...................
InChina,
I had a few more thoughts after reading through this thread again. It sounds like you are out in the frontier flying for a carrier that is trying to reinvent the wheel; no SOPs, PIC manipulates the flight guidance you fly whatever somebody else selects (sorry, but that’s weird), momentary exceeding of limitations brings harsh penalties, and as the FO having to be a complete chameleon adapting to every different Captain assigned as each conducts the flight in their own way (limited to no standardization).
It is not like the NG is a new frontier in aviation and flying a two pilot turbojet crew is some new invention; Aviation Safety Action Programs (self disclosure/no penalty in the interest of safety) standardized training and cultures of non-punitive atmospheres evolve over decades of learning what works and what does not work. In many ways it sounds like your carrier is choosing not to learn from the experienced gained by other carriers or understand how other well established carriers (from all over the world) conduct their flight operations. It sounds like your carrier may be trying to start from scratch. That is a tough way to run an airline. Part of the equation is most likely cultural, and that is a hard one as individual and national pride can be barriers to safety.
The other thing I wanted to mention was the VNAV PTH discussion. I did my share of knocking the system. But we still use it successfully every day. In fact we conduct RNP RNAV approaches to challenging airports that have limited, if any, conventional navigation approaches. The RNP RNAV approach is dependent on the VNAV PTH and it works well-extremely well! It seems like many pilots responding to your experience don’t use the system and descend in LVL CHG or VS. I was surprised. We use VNAV PTH successfully every day. Having said that I will admit that there seems to be an issue with the NG nudging, and going into, the over speed clacker at high altitude. It seems to be a problem up in the middle FL300s and above.
You got burned using the system, and that may lead you to never use it again. That’s your choice of course. I criticized the system, because it is not perfect, but I still use it and in many cases rely on it. VNAV PTH works fine for me, it just needs to be monitored (should not be a surprise). You can fly any way you want to. However I did not want my post to leave the impression that VNAV PTH was completely unreliable, always prone to over speed, and should be abandoned as a means to descend. Like I said we use it successfully all the time (140+ airplanes; 1,400+ crews).
I had a few more thoughts after reading through this thread again. It sounds like you are out in the frontier flying for a carrier that is trying to reinvent the wheel; no SOPs, PIC manipulates the flight guidance you fly whatever somebody else selects (sorry, but that’s weird), momentary exceeding of limitations brings harsh penalties, and as the FO having to be a complete chameleon adapting to every different Captain assigned as each conducts the flight in their own way (limited to no standardization).
It is not like the NG is a new frontier in aviation and flying a two pilot turbojet crew is some new invention; Aviation Safety Action Programs (self disclosure/no penalty in the interest of safety) standardized training and cultures of non-punitive atmospheres evolve over decades of learning what works and what does not work. In many ways it sounds like your carrier is choosing not to learn from the experienced gained by other carriers or understand how other well established carriers (from all over the world) conduct their flight operations. It sounds like your carrier may be trying to start from scratch. That is a tough way to run an airline. Part of the equation is most likely cultural, and that is a hard one as individual and national pride can be barriers to safety.
The other thing I wanted to mention was the VNAV PTH discussion. I did my share of knocking the system. But we still use it successfully every day. In fact we conduct RNP RNAV approaches to challenging airports that have limited, if any, conventional navigation approaches. The RNP RNAV approach is dependent on the VNAV PTH and it works well-extremely well! It seems like many pilots responding to your experience don’t use the system and descend in LVL CHG or VS. I was surprised. We use VNAV PTH successfully every day. Having said that I will admit that there seems to be an issue with the NG nudging, and going into, the over speed clacker at high altitude. It seems to be a problem up in the middle FL300s and above.
You got burned using the system, and that may lead you to never use it again. That’s your choice of course. I criticized the system, because it is not perfect, but I still use it and in many cases rely on it. VNAV PTH works fine for me, it just needs to be monitored (should not be a surprise). You can fly any way you want to. However I did not want my post to leave the impression that VNAV PTH was completely unreliable, always prone to over speed, and should be abandoned as a means to descend. Like I said we use it successfully all the time (140+ airplanes; 1,400+ crews).
I find using VNAV PTH in China can be a very labour intensive operation. In fact I could probably say that about any descent to an airport in Chinese airspace. At one particular airport we go to it is not uncommon to be denied descent clearance until 10 or 20 miles past TOD, and then have to descend with a 50 knot tailwind and try to regain path. All this from a cruise altitude of 22600 feet, so large speed reductions prior to TOD are generally the order of the day.
Other places are the complete opposite where they will have you descending sometimes up to 150nm prior to your normal TOD and telling you "descent rate more than 2500fpm".
So the opportunities for using VNAV PTH for descent I find are very limited but when you do use it you have to watch it very carefully and be prepared to change modes or fly manually at any time.
Other places are the complete opposite where they will have you descending sometimes up to 150nm prior to your normal TOD and telling you "descent rate more than 2500fpm".
So the opportunities for using VNAV PTH for descent I find are very limited but when you do use it you have to watch it very carefully and be prepared to change modes or fly manually at any time.
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Hi, thanks again for the replies. Some of them are very interesting and helpful indeed.
Someone asked what cost index we were using, it was 30 but I don't think that has any effect on this particular scenario as we were in Vnav path not speed mode.
As for the information I entered into the FMC it was in the forecast page, just the airfield temperature deviation and QNH. I didn't enter any winds, the reason I asked what effect the wind would have was because in the ten seconds before we exceeded Mmo the tailwind component increased by 20 knots. I was wondering what effect that would have had on the aircraft flightpath while it was trying to slow the rate of descent and therefore stop the increasing speed, I'm thinking that contributed to the over-speed, but some replies hinted it would contribute, some said it wouldn't so I'm still not sure??? Any more thoughts?
I've checked the QAR and there was no large temperature change accompanying the wind change, so the increase in Mach number due to temperature can be ruled out in this case, but its very interesting information, thanks for posting it.
Northbeach your comments about this company were spot on, are you sure you don't also work here?
Sometime last year an aircraft in this company had a tail-strike, and as pilots most of us still don't know the exact circumstances regarding it. The local pilots in the company were actually enjoying themselves and laughing about it, the punishment and pointing out the mistakes/misfortune of others rather than asking the pilots what happened and learning from it so it could be avoided in the future. Instead the pilot leaders seem to enjoy imposing unless punishment.
As for this situation the behaviour of Vnav descent,I'll put my hand up, it caught me by surprise and its one of the reasons I posted here to try and get some more information. Its not a mode I've used much, I have more than 1500 hours on the 737 all at this company and I can truthfully say I've used it less than ten times and I've certainly not had any guidance or training regarding this. Sim training at this company is more to do with aircraft handling than operational level training. I can happily disengage the auto flight and flight directors and fly manually from 10,000 feet, we are allowed to do it regularly. In the sim we practice things like pilot incapacitated with an engine failure, but we certainly do not do any training regarding CRM or something that would have prepared me better for the Vnav behaviour. Most of this type of “training” is done by myself using the Boeing manuals etc. Also remember no SOP's at this company.
With regards to this case the airline safety board is reviewing the decision and hopefully it will be overturned. The captain I was flying with that day is a senior captain in this company and I've recently been told the chief pilot pushed the initial decision through for “political” reasons. Then two days after the chief pilot pushed our punishment through he took off with no flaps so it will be interesting to see what happens in his case. Anyway I've moved way off the point of my post...................
Someone asked what cost index we were using, it was 30 but I don't think that has any effect on this particular scenario as we were in Vnav path not speed mode.
As for the information I entered into the FMC it was in the forecast page, just the airfield temperature deviation and QNH. I didn't enter any winds, the reason I asked what effect the wind would have was because in the ten seconds before we exceeded Mmo the tailwind component increased by 20 knots. I was wondering what effect that would have had on the aircraft flightpath while it was trying to slow the rate of descent and therefore stop the increasing speed, I'm thinking that contributed to the over-speed, but some replies hinted it would contribute, some said it wouldn't so I'm still not sure??? Any more thoughts?
I've checked the QAR and there was no large temperature change accompanying the wind change, so the increase in Mach number due to temperature can be ruled out in this case, but its very interesting information, thanks for posting it.
Northbeach your comments about this company were spot on, are you sure you don't also work here?
Sometime last year an aircraft in this company had a tail-strike, and as pilots most of us still don't know the exact circumstances regarding it. The local pilots in the company were actually enjoying themselves and laughing about it, the punishment and pointing out the mistakes/misfortune of others rather than asking the pilots what happened and learning from it so it could be avoided in the future. Instead the pilot leaders seem to enjoy imposing unless punishment.
As for this situation the behaviour of Vnav descent,I'll put my hand up, it caught me by surprise and its one of the reasons I posted here to try and get some more information. Its not a mode I've used much, I have more than 1500 hours on the 737 all at this company and I can truthfully say I've used it less than ten times and I've certainly not had any guidance or training regarding this. Sim training at this company is more to do with aircraft handling than operational level training. I can happily disengage the auto flight and flight directors and fly manually from 10,000 feet, we are allowed to do it regularly. In the sim we practice things like pilot incapacitated with an engine failure, but we certainly do not do any training regarding CRM or something that would have prepared me better for the Vnav behaviour. Most of this type of “training” is done by myself using the Boeing manuals etc. Also remember no SOP's at this company.
With regards to this case the airline safety board is reviewing the decision and hopefully it will be overturned. The captain I was flying with that day is a senior captain in this company and I've recently been told the chief pilot pushed the initial decision through for “political” reasons. Then two days after the chief pilot pushed our punishment through he took off with no flaps so it will be interesting to see what happens in his case. Anyway I've moved way off the point of my post...................
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My goodness me, InChina - what fun you must be having
I assume your CP will soon be an F/O?
A few observations which may help you:
Cost Index is relevant - VNAV path will 'attempt' to fly the appropriate speed for CI30 in descent as a target.
I spent many years on 3/4/5/700 filling all the boxes on the descent page, including inside leg, collar size, date of birth, to find it STILL screwed it up
I gave up and put nothing in the box UNLESS there was a tailwind for the descent to avoid the T of D being calculated 'too late'. IF there was a tailwind, that amplified your problem putting you much closer to Mmo.
I would recommend to you, if this 'culture' of doing it 'the Captain's way' exists as you say, that you politely decline if you are unhappy - no major issus - you may be thought of by Cpt X as a 'chicken' or whatever - so what?
If you are in a position where you have to do it in VNAV, I always found LVL CHG with a sensible speed entry was a better option down to below 30k. Generally except for howling tailwinds or really late descents, the 'drag required' can be ignored (provided the speed is controlled) and the path picked up later in descent where there is a greater speed margin as said above - all this, of course, subject to any fixed altitude constraints
Have in your mind where it SHOULD descend for the expected wind conditions and chosen speed etc, and if it does not agree, fly it your way.
Good luck!
I assume your CP will soon be an F/O?A few observations which may help you:
Cost Index is relevant - VNAV path will 'attempt' to fly the appropriate speed for CI30 in descent as a target.
I spent many years on 3/4/5/700 filling all the boxes on the descent page, including inside leg, collar size, date of birth, to find it STILL screwed it up
I gave up and put nothing in the box UNLESS there was a tailwind for the descent to avoid the T of D being calculated 'too late'. IF there was a tailwind, that amplified your problem putting you much closer to Mmo.I would recommend to you, if this 'culture' of doing it 'the Captain's way' exists as you say, that you politely decline if you are unhappy - no major issus - you may be thought of by Cpt X as a 'chicken' or whatever - so what?
If you are in a position where you have to do it in VNAV, I always found LVL CHG with a sensible speed entry was a better option down to below 30k. Generally except for howling tailwinds or really late descents, the 'drag required' can be ignored (provided the speed is controlled) and the path picked up later in descent where there is a greater speed margin as said above - all this, of course, subject to any fixed altitude constraints
Have in your mind where it SHOULD descend for the expected wind conditions and chosen speed etc, and if it does not agree, fly it your way.
Good luck!
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Cost index of 30 is not helping you in this case...
InChina,
I am glad you found my synopsis useful. No, I don’t work for your company nor do I live in China. I am not a Chinese expert at all. I have spent a little time in Africa and the Middle East so I may have a “little” understanding of the challenges you face.
Your cost index will contribute to your problems. A cost index of 30 will result in a higher speed and steeper descent path than a cost index of 10. Therefore, when you go off path (it will happen) and into SPD you will be that much closer to the clacker. A few degrees off standard ISA, a bump of turbulence and you have an excursion. Lowering your cost index is not a silver bullet that will solve this problem. But it will give you more of a margin between the FMC derived descent speeds and the clacker.
Tail strikes on the -800; yes it can happen. Our most recent case was on a long flight with a heavy aircraft, a medium length runway and a disconnect from what the actual flaps were set at for takeoff and the V speeds (V speeds set for one flap setting, the flaps actually set at a different setting).
I am glad you found my synopsis useful. No, I don’t work for your company nor do I live in China. I am not a Chinese expert at all. I have spent a little time in Africa and the Middle East so I may have a “little” understanding of the challenges you face.
Your cost index will contribute to your problems. A cost index of 30 will result in a higher speed and steeper descent path than a cost index of 10. Therefore, when you go off path (it will happen) and into SPD you will be that much closer to the clacker. A few degrees off standard ISA, a bump of turbulence and you have an excursion. Lowering your cost index is not a silver bullet that will solve this problem. But it will give you more of a margin between the FMC derived descent speeds and the clacker.
Tail strikes on the -800; yes it can happen. Our most recent case was on a long flight with a heavy aircraft, a medium length runway and a disconnect from what the actual flaps were set at for takeoff and the V speeds (V speeds set for one flap setting, the flaps actually set at a different setting).
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Hi InChina,
Changing those values forces the computer to recalculate the descent profile. If it now thinks you are slightly high on this new profile, it will stupidly increase ROD in an attempt to capture the new profile rapidly. If the Barber's Pole is close - it's so easy for it to over speed. LVL CHG would have been a better mode until the margin was bigger.
Keel hauling crews for this sort of error is not the best way to educate them. I suspect there will be some floggings next - to help improve morale.
just the airfield temperature deviation and QNH.
Keel hauling crews for this sort of error is not the best way to educate them. I suspect there will be some floggings next - to help improve morale.
Last edited by rudderrudderrat; 9th Mar 2010 at 18:03. Reason: spelling
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Hi In China,
Firstly congrats on a great post, albeit in aweful circumstances.
Anyone here who says that they have no sympathy for you is an idiot. Mabye its a culture thing but that punishment is simply ridiculous and I wouldnt accept it.
If I were you, id go on the attack.
Do the responsible aviation authority know about the lack of SOPs in the company you work for ?
Did the company train you sufficiantly in the use of Vnav?
Do the company have any other safety issues that you could remind the chief pilot that the aviation authority or even the press would be interested in hearing?
Mabye talk to an aviation lawyer.
Dont take it lying down , what youve described is a minor incident made more complicated by procedures, or lack of that the company failed to put in place.
These people get very nervous when you turn the tables and play the safety card.
Good luck , and let us know how you get on
Firstly congrats on a great post, albeit in aweful circumstances.
Anyone here who says that they have no sympathy for you is an idiot. Mabye its a culture thing but that punishment is simply ridiculous and I wouldnt accept it.
If I were you, id go on the attack.
Do the responsible aviation authority know about the lack of SOPs in the company you work for ?
Did the company train you sufficiantly in the use of Vnav?
Do the company have any other safety issues that you could remind the chief pilot that the aviation authority or even the press would be interested in hearing?
Mabye talk to an aviation lawyer.
Dont take it lying down , what youve described is a minor incident made more complicated by procedures, or lack of that the company failed to put in place.
These people get very nervous when you turn the tables and play the safety card.
Good luck , and let us know how you get on
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3 things:
-normal reaction for Chinese or asian airlines
-unintentional overspeed that is immediately corrected is not an issue,just like a single "glideslope" on approach that is immediately corrected..but in asia,they dont see it that way..very SOP-oriented..they take things very literally..you got one warning,ergo you were unsafe.No understanding of airmanship..common-sense and individual thought frowned upon.There is one way to fly the plane..the way described in the book.They've killed a lot of people in crashes..its a nervous environment and they want rote automatons not pilots with airmanship.
-vnav is over-rated...vs is the best AP pitch control offering smoothest flight to crew and pax but is disliked by many who dont know any better.
-normal reaction for Chinese or asian airlines
-unintentional overspeed that is immediately corrected is not an issue,just like a single "glideslope" on approach that is immediately corrected..but in asia,they dont see it that way..very SOP-oriented..they take things very literally..you got one warning,ergo you were unsafe.No understanding of airmanship..common-sense and individual thought frowned upon.There is one way to fly the plane..the way described in the book.They've killed a lot of people in crashes..its a nervous environment and they want rote automatons not pilots with airmanship.
-vnav is over-rated...vs is the best AP pitch control offering smoothest flight to crew and pax but is disliked by many who dont know any better.
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Reply from Boeing
For those who are interested this was the reply we received from Boeing.
We have looked at the data you supplied and from the information we reviewed, we think that this is an airplane issue and not a flight crew error. Both (a captains name deleted) and I feel that the flight crew should not be punished for the brief overspeed on this flight.
Best regards,
(A Boeing Captains name deleted)
Deleted names obviously by me.
Safety review meeting to hear our appeal is tomorrow. I'll let you know the out come.
We have looked at the data you supplied and from the information we reviewed, we think that this is an airplane issue and not a flight crew error. Both (a captains name deleted) and I feel that the flight crew should not be punished for the brief overspeed on this flight.
Best regards,
(A Boeing Captains name deleted)
Deleted names obviously by me.
Safety review meeting to hear our appeal is tomorrow. I'll let you know the out come.
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Sorry to hear both of you are put in this situation...it sucks and I don't think either of you have done anything beyond Boeing SOP's.
I offer this only from my own experience, take it or leave it. I hope it helps someone who reads it...
VNAV path is good only when little change is expected in the wind on descent and/or when your cruise mach is well below Mmo. (say 0.76)
If you have a really strong headwind or tailwind I would always use VNAV speed. VNAV path, although good, never gives you that protection quickly enough. If I have 100 kts tailwind component at upper cruise levels, I descend early by 10% of that TWC. (ie 10nm) in VNAV speed. If its a HWC, 10% late. (I just use time to measure it - ALT HOLD before TOPD then when the chinese glideslope appears, start the timer...If you are doing say 480kts GS or 8nm/min, then start you VNAV speed descent 1min 15 sec after the slope appears, for the headwind, before for the tailwind.
This my own rule of thumb and everyone has a different way to do it of course but I find it picks up the profile by 15-10,000'. Then use VNAV path from there as most of the height restrictions on a star are generally below 10,000'.
It never is an exact science and I'm constantly learning new things. Hope it all works out...
I offer this only from my own experience, take it or leave it. I hope it helps someone who reads it...
VNAV path is good only when little change is expected in the wind on descent and/or when your cruise mach is well below Mmo. (say 0.76)
If you have a really strong headwind or tailwind I would always use VNAV speed. VNAV path, although good, never gives you that protection quickly enough. If I have 100 kts tailwind component at upper cruise levels, I descend early by 10% of that TWC. (ie 10nm) in VNAV speed. If its a HWC, 10% late. (I just use time to measure it - ALT HOLD before TOPD then when the chinese glideslope appears, start the timer...If you are doing say 480kts GS or 8nm/min, then start you VNAV speed descent 1min 15 sec after the slope appears, for the headwind, before for the tailwind.
This my own rule of thumb and everyone has a different way to do it of course but I find it picks up the profile by 15-10,000'. Then use VNAV path from there as most of the height restrictions on a star are generally below 10,000'.
It never is an exact science and I'm constantly learning new things. Hope it all works out...
