Rejecting A Takeoff After V1…why Does It (still) Happen?
Old Fella
I was comparing RTOW on longish runway to a normal, end of cruise weight--and still off. Using the later posting, 60% looks like a reasonable number. In any case, Splendid Cruiser presents some good info.
SSG, Johns7023
Do try to learn and stop banging your spoon on the table. Yes, more planes of all types FLY to the scene of the crash, but THE DISCUSSION HERE IS ON REJECTED TAKE-OFFS!
Out of curiosity, at what speed did they overrun at CYVR? Good catch on the FE's part. Johns7022, you could learn something about CRM and the reason crews work better!
GF
I was comparing RTOW on longish runway to a normal, end of cruise weight--and still off. Using the later posting, 60% looks like a reasonable number. In any case, Splendid Cruiser presents some good info.
SSG, Johns7023
Do try to learn and stop banging your spoon on the table. Yes, more planes of all types FLY to the scene of the crash, but THE DISCUSSION HERE IS ON REJECTED TAKE-OFFS!
Out of curiosity, at what speed did they overrun at CYVR? Good catch on the FE's part. Johns7022, you could learn something about CRM and the reason crews work better!
GF
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GF, they went off the end at 43 knots. Full report here, and highly relevant to the discussion here - not that our wannabee microsoft driver expounding here would understand.
Transportation Safety Board of Canada - AVIATION REPORTS - 1995 - A95H0015
When comparing the energy levels of a reject compared to landing at max permissible weight need to remember the .5mv^2 formula. It's the v that's the killer.
Transportation Safety Board of Canada - AVIATION REPORTS - 1995 - A95H0015
When comparing the energy levels of a reject compared to landing at max permissible weight need to remember the .5mv^2 formula. It's the v that's the killer.
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johns7022 . . .Cadet pilot . . .
Ah yes the failing brake argument....that brakes are perfectly reliable for landings, but during RTOs your brake disks turn into marshmellows...but not on landings...only RTOs.
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The conversation has always been an RTO vs Flying it off...those are your choices...
If you do a little study on how planes are flight tested for RTOs, it's pretty much Joe Test Pilot accelerating up and down the runway to V1, then applying brakes.....then recording the distance data, checking the brakes for issues ect.
Now the manufacturer has some flight test numbers of a pilot who say just did 1000 RTOs...he's probably gotten pretty good at them...so some buffers are added to for variables such as age planes, back pilots, older brakes and tires...probably a little for mom.
So let's think about this...with all the runway in the world ahead of you, stopping distance is not the issue...and the difference between V1 to VR is say 10 knots.....do you really think that if your brakes are certified to be 100% reliable to brake from V1, at Max Gross Weight ...that another 5kts or so is going to be the difference in your brakes failing?
If your going to make the argument of not doing RTOs....the proper way to discuss your end is talk about distance, not brake failure, and why so many of you are throwing out your margins with assumed power/derated take offs.
If you do a little study on how planes are flight tested for RTOs, it's pretty much Joe Test Pilot accelerating up and down the runway to V1, then applying brakes.....then recording the distance data, checking the brakes for issues ect.
Now the manufacturer has some flight test numbers of a pilot who say just did 1000 RTOs...he's probably gotten pretty good at them...so some buffers are added to for variables such as age planes, back pilots, older brakes and tires...probably a little for mom.
So let's think about this...with all the runway in the world ahead of you, stopping distance is not the issue...and the difference between V1 to VR is say 10 knots.....do you really think that if your brakes are certified to be 100% reliable to brake from V1, at Max Gross Weight ...that another 5kts or so is going to be the difference in your brakes failing?
If your going to make the argument of not doing RTOs....the proper way to discuss your end is talk about distance, not brake failure, and why so many of you are throwing out your margins with assumed power/derated take offs.
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I have never flown anything heavy apart from a few hours once doing an MCC course. I fully appreciate the reasons for V1, runway length, brake energy etc but I can see one immediate reason for rejecting beyond V1. I am delving a long way back to my performance A exam so stand by to be corrected but I seem to remember that you can only use a maximum of 15 kts headwind component for planning purposes. If you are taking off into a headwind of 30 kts and the aircraft V1 is based on braking ability, or runway length, then surely rejecting at 10 kts beyond V1 should cause no problem as the groundspeed is (in this case) 5 kts below the V1 that the graphs have produced.
Moderator
If you do a little study on how planes are flight tested for RTOs, it's pretty much Joe Test Pilot accelerating up and down the runway to V1, then applying brakes.....then recording the distance data, checking the brakes for issues ect.
.. from which we can infer that such testing is not in your background ?
do you really think that if your brakes are certified to be 100% reliable to brake from V1, at Max Gross Weight ...that another 5kts or so is going to be the difference in your brakes failing?
.. one might consider brake capability as being a bit like a bucket of money. When you go for the RTO (and we are looking at a critical case here - GW, OAT, wind, slope, etc - clearly, the further away from the critical situation one might be, the better the situation) you start throwing out (large) handfuls of money. When the bucket is empty, it's all over. What the line pilot doesn't know, however, are the real margins inherent in the specific certification.
Point is, if one operates outside the Book, then one is venturing into no-man's land .. the statistical basis for certification provides a measure of protection for the operator and crew (and, by their being glued to the cockpit, the passengers). Outside those boundaries, the pilot (or other relevant person, eg maintainer for maintenance actions) carries a burden of having to justify his/her decisions after the event - I draw the reader's attention to any of a vast number of legal proceedings .. the Air France Concorde outcome in recent days makes for interesting thoughts ?
the proper way to discuss your end is talk about distance, not brake failure, and why so many of you are throwing out your margins with assumed power/derated take offs.
Two different considerations albeit with some linkage in terms of risk.
To talk distance is fine .. but, if the brakes have quit ... that extra distance might not be enough on the day.
For those who might take issue with Johns7022's views, the importance is that such views challenge the conventions and lead to vigorous and robust discussion .. all of which should be useful for Tech Log's educational interests.
Whether he might be right or wrong is not the point ..
If you are taking off into a headwind of 30 kts and the aircraft V1 is based on braking ability, or runway length, then surely rejecting at 10 kts beyond V1 should cause no problem as the groundspeed is (in this case) 5 kts below the V1 that the graphs have produced.
One presumes that you have the data and engineering know-how to justify such an action after the event ?
Point in question is
(a) if things are reasonably "normal", one probably is better served by sticking to the certification paddock as prescribed and described in the OEM AFM and similar documents. Well thought out SOPs provide some measure of protection after the event as well as sound risk management strategies for normal and defined abnormal/emergency situations..
Any suggestion purporting, routinely, to operate outside the norm is somewhere between very stupid and unbelievably stupid.
(b) if things go decidedly pear shaped and out of left field during the flight, then the Commander gets to earn his/her big bucks at the time. The outcome will involve consideration of knowledge (general technical and specific event-related), skill, a measure of luck .. and a bunch of other matters relevant to the specific event
Whether such decisions might cause difficulty and heartache at the subsequent enquiry is a moot point.
One needs to keep in mind that 20/20 hindsight is a wonderful thing, greatly admired by the legal fraternity, and has hung more than a few crews out to dry after the event in which they had barely a couple of seconds to make a critical, usually non-briefed, call ...
.. from which we can infer that such testing is not in your background ?
do you really think that if your brakes are certified to be 100% reliable to brake from V1, at Max Gross Weight ...that another 5kts or so is going to be the difference in your brakes failing?
.. one might consider brake capability as being a bit like a bucket of money. When you go for the RTO (and we are looking at a critical case here - GW, OAT, wind, slope, etc - clearly, the further away from the critical situation one might be, the better the situation) you start throwing out (large) handfuls of money. When the bucket is empty, it's all over. What the line pilot doesn't know, however, are the real margins inherent in the specific certification.
Point is, if one operates outside the Book, then one is venturing into no-man's land .. the statistical basis for certification provides a measure of protection for the operator and crew (and, by their being glued to the cockpit, the passengers). Outside those boundaries, the pilot (or other relevant person, eg maintainer for maintenance actions) carries a burden of having to justify his/her decisions after the event - I draw the reader's attention to any of a vast number of legal proceedings .. the Air France Concorde outcome in recent days makes for interesting thoughts ?
the proper way to discuss your end is talk about distance, not brake failure, and why so many of you are throwing out your margins with assumed power/derated take offs.
Two different considerations albeit with some linkage in terms of risk.
To talk distance is fine .. but, if the brakes have quit ... that extra distance might not be enough on the day.
For those who might take issue with Johns7022's views, the importance is that such views challenge the conventions and lead to vigorous and robust discussion .. all of which should be useful for Tech Log's educational interests.
Whether he might be right or wrong is not the point ..
If you are taking off into a headwind of 30 kts and the aircraft V1 is based on braking ability, or runway length, then surely rejecting at 10 kts beyond V1 should cause no problem as the groundspeed is (in this case) 5 kts below the V1 that the graphs have produced.
One presumes that you have the data and engineering know-how to justify such an action after the event ?
Point in question is
(a) if things are reasonably "normal", one probably is better served by sticking to the certification paddock as prescribed and described in the OEM AFM and similar documents. Well thought out SOPs provide some measure of protection after the event as well as sound risk management strategies for normal and defined abnormal/emergency situations..
Any suggestion purporting, routinely, to operate outside the norm is somewhere between very stupid and unbelievably stupid.
(b) if things go decidedly pear shaped and out of left field during the flight, then the Commander gets to earn his/her big bucks at the time. The outcome will involve consideration of knowledge (general technical and specific event-related), skill, a measure of luck .. and a bunch of other matters relevant to the specific event
Whether such decisions might cause difficulty and heartache at the subsequent enquiry is a moot point.
One needs to keep in mind that 20/20 hindsight is a wonderful thing, greatly admired by the legal fraternity, and has hung more than a few crews out to dry after the event in which they had barely a couple of seconds to make a critical, usually non-briefed, call ...
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John - Personally I am not a certified test pilot...but flight testing is more then a passing interest and something that I have studied....more to the point I have sought out personal discussions with people who were on the ground changing out brakes during the S550 ground runs at Lake Havisu and others with regard to anti lock brakes, VMO...ect.
I am not here to flout the numbers or suggest everyone willy nilly do what they want in the plane counter to good pilot practice...but when it comes to judgment calls, where it's one bad choice vs another bad choice...then the variables for those choices come into play..the more we know the more we understand, the best we can make a good decision.
If Joe Test pilot can do a V1 RTO for the given conditions....he will stop in X feet...but you will be given Y feet...a much higher number. If they tell you that your brakes will work 100% of the time from a V1 RTO....I can guarantee that 5 knots faster is not some magic wall you have crossed where you go from 100% reliability to 100% failure. It doesn't work that way.
Now maybe stalling speeds are somewhat aerodynamically absolute.....the VMO numbers you get have a 50 kt buffer with a big g force pull back..
So just for the record if you have the runway to stop, but are willing to fly a burning wreck through the air because you feel your brakes will fail, because your 5 kts over V1, I don't agree.
I am not here to flout the numbers or suggest everyone willy nilly do what they want in the plane counter to good pilot practice...but when it comes to judgment calls, where it's one bad choice vs another bad choice...then the variables for those choices come into play..the more we know the more we understand, the best we can make a good decision.
If Joe Test pilot can do a V1 RTO for the given conditions....he will stop in X feet...but you will be given Y feet...a much higher number. If they tell you that your brakes will work 100% of the time from a V1 RTO....I can guarantee that 5 knots faster is not some magic wall you have crossed where you go from 100% reliability to 100% failure. It doesn't work that way.
Now maybe stalling speeds are somewhat aerodynamically absolute.....the VMO numbers you get have a 50 kt buffer with a big g force pull back..
So just for the record if you have the runway to stop, but are willing to fly a burning wreck through the air because you feel your brakes will fail, because your 5 kts over V1, I don't agree.
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Put away the crash reports...more airliners FLY to the scene of the accident then roll to the incident on departure.
Seems it's working, isn't it? Perhaps we, the professionals, know our jobs a little better than you. Could it be?
If they tell you that your brakes will work 100% of the time from a V1 RTO....I can guarantee that 5 knots faster is not some magic wall you have crossed where you go from 100% reliability to 100% failure. It doesn't work that way.
There is nothing "magic" about being five knots faster than V1, but you do understand that V1 is not a fixed number, and has direct and critical application to a number of factors, most specifically the length of the runway in use, as well as the stopping distance available after reaching V1; you do understand this, right?
Often when we plan a takeoff, we have just enough runway to stop if we reject before V1. After V1, we do not have the runway to stop. This has nothing to do with magic. It has everything to do with the physical runway available, period, end of story.
V1 is a very, very important number, created, crafted, and calculated specifically for this takeoff, right here, right now, on this day, in this place, in this airplane, at this weight, at this temperature. It is not a magic number. It is a performance number that has very significant import with respect to our decision making process when we either reject the takeoff, or continue. Given the amount of data that goes into producing this number for this takeoff in this airplane under these conditions, what on earth makes you think you have the spice to come up with your own alternate reality on the fly? You don't; this is why we do our performance calculations before we take off. This is not mindless data; it's critical information.
So just for the record if you have the runway to stop, but are willing to fly a burning wreck through the air because you feel your brakes will fail, because your 5 kts over V1, I don't agree.
SSG is back. Again. New name, same, stupid material.
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but when it comes to judgment calls, where it's one bad choice vs another bad choice...then the variables for those choices come into play..the more we know the more we understand, the best we can make a good decision.
.. and that is why the discussions are so important.
Stimulating and provocative thoughts held by any individual need to be put on the table for other folk to contemplate. There needs to be vigorous discussion so that the new chums get a bit more depth than the typical ATPL course and endorsment program.
he will stop in X feet
That's not actually how it works and that was the point of my earlier comment.
Accel-stop test data is not real world (as those who have been involved with such testing would understand) and ought only to be viewed as (a little bit worse than) brick wall data for line operations.
Put it this way .. the first performance landing tests for which I was along in the aircraft caused me more than a touch of anxiety. To suggest that Joe Bloggs, line pilot, is going to reproduce the TP's performance .. is arrant nonsense and indicates a lack of familiarity with what goes on. By the time the test program is finished and TP/FTE/aerodynamicists have played with the results, the TP will be hard pressed to replicate the final averaged data.
I can guarantee that 5 knots faster is not some magic wall you have crossed where you go from 100% reliability to 100% failure. It doesn't work that way.
I am not too sure about guarantees in performance .. statistics is the name of the game and that only delves into probabilities, not guarantees. However, of course it is not a "switch on, switch off" situation. The problem, though, is that the line pilot doesn't have any real understanding as to just where the good starts to get bad ... hence the need to be mindful of SOPs.
Now maybe stalling speeds are somewhat aerodynamically absolute.....
Not really the case - one needs to define the conditions with a degree of precision to get a particular number for a given aircraft
the VMO numbers you get have a 50 kt buffer with a big g force pull back..
Vmo is a little bit different to most other limits and probably is not pertinent to this thread's discussion
if you have the runway to stop,
Therein lies the difficulty in respect of making that determination on many occasions
but are willing to fly a burning wreck through the air because you feel your brakes will fail, because your 5 kts over V1, I don't agree.
It all comes down to a question of what data and knowledge the pilot has .. considering that that pilot WILL be asked at the enquiry to justify his/her decision (assuming he/she lives to tell the tale). Methinks you are intent on needlessly dramatising the situation for effect ?
.. and that is why the discussions are so important.
Stimulating and provocative thoughts held by any individual need to be put on the table for other folk to contemplate. There needs to be vigorous discussion so that the new chums get a bit more depth than the typical ATPL course and endorsment program.
he will stop in X feet
That's not actually how it works and that was the point of my earlier comment.
Accel-stop test data is not real world (as those who have been involved with such testing would understand) and ought only to be viewed as (a little bit worse than) brick wall data for line operations.
Put it this way .. the first performance landing tests for which I was along in the aircraft caused me more than a touch of anxiety. To suggest that Joe Bloggs, line pilot, is going to reproduce the TP's performance .. is arrant nonsense and indicates a lack of familiarity with what goes on. By the time the test program is finished and TP/FTE/aerodynamicists have played with the results, the TP will be hard pressed to replicate the final averaged data.
I can guarantee that 5 knots faster is not some magic wall you have crossed where you go from 100% reliability to 100% failure. It doesn't work that way.
I am not too sure about guarantees in performance .. statistics is the name of the game and that only delves into probabilities, not guarantees. However, of course it is not a "switch on, switch off" situation. The problem, though, is that the line pilot doesn't have any real understanding as to just where the good starts to get bad ... hence the need to be mindful of SOPs.
Now maybe stalling speeds are somewhat aerodynamically absolute.....
Not really the case - one needs to define the conditions with a degree of precision to get a particular number for a given aircraft
the VMO numbers you get have a 50 kt buffer with a big g force pull back..
Vmo is a little bit different to most other limits and probably is not pertinent to this thread's discussion
if you have the runway to stop,
Therein lies the difficulty in respect of making that determination on many occasions
but are willing to fly a burning wreck through the air because you feel your brakes will fail, because your 5 kts over V1, I don't agree.
It all comes down to a question of what data and knowledge the pilot has .. considering that that pilot WILL be asked at the enquiry to justify his/her decision (assuming he/she lives to tell the tale). Methinks you are intent on needlessly dramatising the situation for effect ?
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For those who might take issue with Johns7022's views, the importance is that such views challenge the conventions and lead to vigorous and robust discussion .. all of which should be useful for Tech Log's educational interests.
http://www.pprune.org/tech-log/32726...-after-v1.html
Moderator
poster johns7022 is but our old friend ssg
That may well be the case, Brian, but I need to be seen to be taking a middle of the road position
perhaps the threads could be merged.
.. good suggestion and only not done as the result would be a bit too hard to follow
When we eventually catch up for that beer or twenty we can discuss such things in erudite fashion ..
That may well be the case, Brian, but I need to be seen to be taking a middle of the road position
perhaps the threads could be merged.
.. good suggestion and only not done as the result would be a bit too hard to follow
When we eventually catch up for that beer or twenty we can discuss such things in erudite fashion ..
Brian and the Learned J_T,
Funny, you two should be linking to that thread. I searched last night, after midnight EST, mind you, and reread every blessed page of it. I was searching for the "formula" for estimating speed at overrun based on a decision after V1. My learned colleague from Canuckistan verified the veracity of those estimates. Also, I was reminded of the density that afflicts the gray matter at times, the knowledge exhibited herein and the patience attached thereto and the marginal increase in my own knowledge base coming from these threads. However much said gray matter hurts whilst the threads are underway.
This thread does seem endless, one expects some learning to occur, then one wakes up and realizes, "no, learning does NOT have to occur".
J_T. I look forward to shouting some of the golden nectar. Lately, I seem to be stuck visiting Pommie Land, second trip there in two weeks this weekend. Dreadful, snowy, cold and barren! And then, there are the locals!
Funny, you two should be linking to that thread. I searched last night, after midnight EST, mind you, and reread every blessed page of it. I was searching for the "formula" for estimating speed at overrun based on a decision after V1. My learned colleague from Canuckistan verified the veracity of those estimates. Also, I was reminded of the density that afflicts the gray matter at times, the knowledge exhibited herein and the patience attached thereto and the marginal increase in my own knowledge base coming from these threads. However much said gray matter hurts whilst the threads are underway.
This thread does seem endless, one expects some learning to occur, then one wakes up and realizes, "no, learning does NOT have to occur".
J_T. I look forward to shouting some of the golden nectar. Lately, I seem to be stuck visiting Pommie Land, second trip there in two weeks this weekend. Dreadful, snowy, cold and barren! And then, there are the locals!
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Johns7022
On several occasions, I have been witness to large, really large, planes asked to meet the data, as calculated in that thick book known as "Flight Manual, Appendix 1, Performance Data". In each of those times, said Lockhed product performed exactly as advertised. Sitting in the jump seat at a USN Base Med, giving an eval. At a hair's breadth of V1, the plane gets whacked by birds. Absolutely, no time to discuss, it is a critical field length take-off, the pilot decides to stop. Once, at rest, the plane was on the numbers and we could not see the runway end out the front. An engineer went out to clear the turn around, after letting the brakes cool, which were near fuse plug limits. I cannot remember if any let go. Another time, on ice, at a NE base, landing calcs with RCR 6 (like Canadian friction reading), poor braking, more like poor to nil. Runway length 7000', LGW about 550K, getting evaluated. Calculated landing distance was 5000+ feet, we stopped abeam the 2,000 remaining boards, after standing, and I mean STANDING on the brakes and reversers.
My point in all this, is that the certification numbers are real, they are NOT to cast aside any "margins" or "pads" are not yours to play with. If you are on a field length limited take-off, options are scarce and the ideas being floated here are NOT appropriate for young, inexperienced aviators. I have attended the funerals of the similarly influenced, if not exact copies. Not happily, I assure you.
GF
On several occasions, I have been witness to large, really large, planes asked to meet the data, as calculated in that thick book known as "Flight Manual, Appendix 1, Performance Data". In each of those times, said Lockhed product performed exactly as advertised. Sitting in the jump seat at a USN Base Med, giving an eval. At a hair's breadth of V1, the plane gets whacked by birds. Absolutely, no time to discuss, it is a critical field length take-off, the pilot decides to stop. Once, at rest, the plane was on the numbers and we could not see the runway end out the front. An engineer went out to clear the turn around, after letting the brakes cool, which were near fuse plug limits. I cannot remember if any let go. Another time, on ice, at a NE base, landing calcs with RCR 6 (like Canadian friction reading), poor braking, more like poor to nil. Runway length 7000', LGW about 550K, getting evaluated. Calculated landing distance was 5000+ feet, we stopped abeam the 2,000 remaining boards, after standing, and I mean STANDING on the brakes and reversers.
My point in all this, is that the certification numbers are real, they are NOT to cast aside any "margins" or "pads" are not yours to play with. If you are on a field length limited take-off, options are scarce and the ideas being floated here are NOT appropriate for young, inexperienced aviators. I have attended the funerals of the similarly influenced, if not exact copies. Not happily, I assure you.
GF
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Guppy.
Pick any V1 for the day.... add 5kts faster, 5% faster, ect....isn't going to cause a brake failure on an RTO.
If you now want to change back to the subject of runway length available, and the pilot being able to make that judgment having passed V1..
Well I will yet again, repeat, yet again, that with a calculated balance field of say 5000 ft that day...on a ten thousand foot field...and say V1 is established roughly at 2000 -2500 feet...I think it's a safe bet with 7500 feet left over, and overrun beyond, Iowa cornfields beyond, that I will be able to stop the plane without TRs, without hammering the brakes.....
But again, if on that day, with 100 in-definate, blowing snow, forced to fly to the alternate, because this runway only has a GPS approach...you feel free to take the fire, bomb, broken tail up into the soup, pick up some ice...and fly off to your new runway trying to get your broken plane back down safely.
If your assertion is that you don't have any more runway..ever....that all your flights have derated balance field departures calculated into the weeds, forcing you take the emergency up into the air, all the time......that's a policy decision, not because your flying 737s into grass strips in Mongolia. Remember that the next time you fly out of LAX and derate your balanced field to somewhere in San Diego.
Pick any V1 for the day.... add 5kts faster, 5% faster, ect....isn't going to cause a brake failure on an RTO.
If you now want to change back to the subject of runway length available, and the pilot being able to make that judgment having passed V1..
Well I will yet again, repeat, yet again, that with a calculated balance field of say 5000 ft that day...on a ten thousand foot field...and say V1 is established roughly at 2000 -2500 feet...I think it's a safe bet with 7500 feet left over, and overrun beyond, Iowa cornfields beyond, that I will be able to stop the plane without TRs, without hammering the brakes.....
But again, if on that day, with 100 in-definate, blowing snow, forced to fly to the alternate, because this runway only has a GPS approach...you feel free to take the fire, bomb, broken tail up into the soup, pick up some ice...and fly off to your new runway trying to get your broken plane back down safely.
If your assertion is that you don't have any more runway..ever....that all your flights have derated balance field departures calculated into the weeds, forcing you take the emergency up into the air, all the time......that's a policy decision, not because your flying 737s into grass strips in Mongolia. Remember that the next time you fly out of LAX and derate your balanced field to somewhere in San Diego.
It says in my manual, at maximum brake energy (that is, an RTO using full anti-skid brakng, 33.1 million ft-lb per brake, that "Evacuate airplane, Hydraulic fire and blown fuse plugs are imminent. Leave immediate vicinity". I'd consider that a real emergency, how about you?
Please explain how a derate take-off puts the field out to San Diego or in the weeds and still complies with FAR 121 or FAR 25.
GF
Who is your recurrent training provider? The FAA would like to know.
Please explain how a derate take-off puts the field out to San Diego or in the weeds and still complies with FAR 121 or FAR 25.
GF
Who is your recurrent training provider? The FAA would like to know.
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Well then Galaxy...it sounds like Boeing Products consider an RTO at the very edge of the brake and tire capabilities.....the tires are blown, the brakes are melted..run for your lives...run for the hills....
Curious if you guys have ever done a V1 RTO in the plane....all Sim work is it?
Gee whiz guys, I have done V1 cuts in jets for YEARS..over and over, and over...still here.....not so much as a flat spot on the tires.
So maybe this is a make/model problem....
Curious if you guys have ever done a V1 RTO in the plane....all Sim work is it?
Gee whiz guys, I have done V1 cuts in jets for YEARS..over and over, and over...still here.....not so much as a flat spot on the tires.
So maybe this is a make/model problem....
Moderator
for estimating speed at overrun based on a decision after V1
Depends on a bunch of things, as always ... however, if one considers initiating a reject a little after V1, as for example in the case of startle factor, there will be three stages to consider
(a) the speed/distance overrun. For an AEO reject this will be a modest kt/sec value and, for the OEI case, something lower again. Main result is that the speed increase will normally be comparatively modest but the distance lost which is associated with the delay can be quite significant. For example, for a nominal V1=150kt increasing to, say, 160kt, we are looking at something in the order of 260 feet/sec overrun .. 4 seconds and you have burnt up 1000 ft. As I recall for the 722, a critical reject stopping distance was in the order of 1500-2000 feet or so ? One really can't afford to squander 1000 feet in anger ..
(b) the transition from go to whoa. It is probably reasonable to presume that a well trained pilot, after the startle loss, will go through the motions more or less as per training. For the sake of the argument, let's suppose that this phase is the same for a correct/overspeed initiation.
(c) once the reject is in full swing, the rate of deceleration is quite significant and driven principally by V^2 in the first approximation. What this means, for a critical ASDR runway overrun, is that the end of the expected distance can be crossed at quite a significant speed.
(i) first result is that one IS going to end up in the rough
(ii) second result is that the braking capability is almost certainly going to be significantly less .. ie the net deceleration will decrease .. and the bird ends up some moderate distance off the end of the seal in whatever state of disrepair and in whatever terrain pertains ....
Point is ... accel stop on a critical length bit of seal ... is a VERY critical operation and one had best get it right first time around ... as there is no second chance if that doesn't happen.
Gee whiz guys, I have done V1 cuts in jets for YEARS..over and over, and over...still here.....not so much as a flat spot on the tires.
.. but not on a limiting strip length, I suspect ?
Depends on a bunch of things, as always ... however, if one considers initiating a reject a little after V1, as for example in the case of startle factor, there will be three stages to consider
(a) the speed/distance overrun. For an AEO reject this will be a modest kt/sec value and, for the OEI case, something lower again. Main result is that the speed increase will normally be comparatively modest but the distance lost which is associated with the delay can be quite significant. For example, for a nominal V1=150kt increasing to, say, 160kt, we are looking at something in the order of 260 feet/sec overrun .. 4 seconds and you have burnt up 1000 ft. As I recall for the 722, a critical reject stopping distance was in the order of 1500-2000 feet or so ? One really can't afford to squander 1000 feet in anger ..
(b) the transition from go to whoa. It is probably reasonable to presume that a well trained pilot, after the startle loss, will go through the motions more or less as per training. For the sake of the argument, let's suppose that this phase is the same for a correct/overspeed initiation.
(c) once the reject is in full swing, the rate of deceleration is quite significant and driven principally by V^2 in the first approximation. What this means, for a critical ASDR runway overrun, is that the end of the expected distance can be crossed at quite a significant speed.
(i) first result is that one IS going to end up in the rough
(ii) second result is that the braking capability is almost certainly going to be significantly less .. ie the net deceleration will decrease .. and the bird ends up some moderate distance off the end of the seal in whatever state of disrepair and in whatever terrain pertains ....
Point is ... accel stop on a critical length bit of seal ... is a VERY critical operation and one had best get it right first time around ... as there is no second chance if that doesn't happen.
Gee whiz guys, I have done V1 cuts in jets for YEARS..over and over, and over...still here.....not so much as a flat spot on the tires.
.. but not on a limiting strip length, I suspect ?