Runway behind you - a way to save time?
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Isn't it wonderful what characters we've apparently got sitting up front thesedays? They can learn multiple-choice answers by rote but few are prepared to acknowledge that if 99 of their colleagues' flights in the same aircraft at the same airport with similar loads always choose to go to the end of the runway, then the one that's half an hour late one night and goes from 2300 feet further down surely begs a question?
Of course intersection departures are in use for all manner of reasons at all manner of airports every day.
I say again, this is not a busy airfield. It is an exceptionally quiet airfield, especially at the time of day. It is an airfield where the aircrew can make ALL the choices. This crew hesitated at the intersection with the parallel runway (main taxiway) and hesitated again on reaching the active. The wheels did not stop turning the moment we left the apron, but they nearly did twice.
To counter a few long words bandied about here, I have not accused anyone of negligence, nor of 'unprofessionalism' (whatever floats your boat or sinks it) ... I have merely questioned the prudential aspects of leaving a quarter of the runway behind you when the ONLY gain is 2300 feet of taxy expense less the saving in expense of the take-off power settings used from the end, and maybe the 5 minutes (probably less) to taxy that bit further.
I have read all that has been written, even though some of it has only been written to criticise me personally as some imperfect individual because I have used airy-fairy estimates in my arguments. Yes guys I do know that you can't fly with airy-fairy estimates except maybe the passenger/baggage ones.
Most of you have resorted to clouding the question with all manner of supposed other reasons or restrictions which were not actually a factor. Others of you want me to understand that the RTO braking is something to behold and is not within my experience. Accepted.
It's a funny old forum sometimes. It is quite interesting how some pilots blow off steam by throwing personal insults around at the slightest provocation.
I think I have my answer. I think I broadly had it when I started the thread, eh? Does that really make me the besserwisser?
Due to the length of the runway, this crew, above many, looking for ways to save a few minutes when running late, had noticed that an intersection departure was a possibility.
Had they not been late, they probably would not have made the choice of an intersection departure. I mean, why would they?
Those that say ay say ay, those that say no say no ...
I think the besserwissers have it
Of course intersection departures are in use for all manner of reasons at all manner of airports every day.
I say again, this is not a busy airfield. It is an exceptionally quiet airfield, especially at the time of day. It is an airfield where the aircrew can make ALL the choices. This crew hesitated at the intersection with the parallel runway (main taxiway) and hesitated again on reaching the active. The wheels did not stop turning the moment we left the apron, but they nearly did twice.
To counter a few long words bandied about here, I have not accused anyone of negligence, nor of 'unprofessionalism' (whatever floats your boat or sinks it) ... I have merely questioned the prudential aspects of leaving a quarter of the runway behind you when the ONLY gain is 2300 feet of taxy expense less the saving in expense of the take-off power settings used from the end, and maybe the 5 minutes (probably less) to taxy that bit further.
I have read all that has been written, even though some of it has only been written to criticise me personally as some imperfect individual because I have used airy-fairy estimates in my arguments. Yes guys I do know that you can't fly with airy-fairy estimates except maybe the passenger/baggage ones.
Most of you have resorted to clouding the question with all manner of supposed other reasons or restrictions which were not actually a factor. Others of you want me to understand that the RTO braking is something to behold and is not within my experience. Accepted.
It's a funny old forum sometimes. It is quite interesting how some pilots blow off steam by throwing personal insults around at the slightest provocation.
I think I have my answer. I think I broadly had it when I started the thread, eh? Does that really make me the besserwisser?
Due to the length of the runway, this crew, above many, looking for ways to save a few minutes when running late, had noticed that an intersection departure was a possibility.
Had they not been late, they probably would not have made the choice of an intersection departure. I mean, why would they?
Those that say ay say ay, those that say no say no ...
I think the besserwissers have it
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We always plan for the intersection departure from 23L at MAN. There is loads of spare performance and we will use it if it saves time & fuel. By planning for it, we have the option. That applies whether running late, early or on time.
If the full length becomes available, then we'll use that. Either you trust the numbers or you don't. Simple really.
If the full length becomes available, then we'll use that. Either you trust the numbers or you don't. Simple really.
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The original poster should have been at an event I attended last weekend. Of the fifty odd aircraft departing only two went to the furthest extent of the runway to start their take off run. Does this suggest that the other 48 were being negligent or careless? Or could it be that they (correctly) calculated that the amount of runway before them was sufficient for a safe departure.
The was no apparent significant difference between the two that used the earlier start point than many of the others.
D.
The was no apparent significant difference between the two that used the earlier start point than many of the others.
D.
Warning Toxic!
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Give it up mate. I don't think anybody is reading your crap anymore. You persist in thinking you know better. Pilots don't taxi unless they know the way they are going. They have worked out their performance before they start taxy so they have decided where they will take off from and why. Your job is not to challenge or judge a legal decision by the commander, your job is to sit there and shut it. So shut it!
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Yessir, Mr. Vernacular, Sir! Three bags full Sir! 
BTW, shouldn't we have taken a left back there? No matter, we can still go from the intersection, can't we, Sir? Or we can even backtrack if you like, Sir?
... Or not?
If that'll be all, Sir, I'll go find my place down the back then Sir ...
BTW, shouldn't we have taken a left back there? No matter, we can still go from the intersection, can't we, Sir? Or we can even backtrack if you like, Sir?
... Or not?If that'll be all, Sir, I'll go find my place down the back then Sir ...
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Slip and Turn
I'm hoping that you realise 2 things
1) That V1 is NOT a fixed speed. It is dependant on a whole host of factors such as weight, runway state, runway length, flap setting and so forth.
2) Engine thrust is NOT a fixed setting. You can reduce thrust if you do not need all of it to save engine life. Hence if you are heavy on a short runway you use a much greater percentage of your maximum available thrust than if you are light on a long runway. However the net overall effect is the same. Put in very simple laymans terms you trade thrust for runway length depending on weight.
I really reccomend that you do some research on the balanced field concept. It is the crux of modern performance calculations. Granted it's not an easy concept to understand if explained badly, but all perf calcs are based on balanced field in one way or another.
I honestly think you have a basic misunderstanding of performance A calculations.
I will always do performance calculations based on the most limiting intersection i am likely to get. If i'm too heavy i'll take a less limiting intersection. If ATC need me to take full length for whatever reason i'll take full length. However i could take the intersection if i needed/wanted to without eroding any safety factors.
Also from your messages i believe you're talking about ryanair. I do not work for them, however i am lead to believe that their SOP's are second to none, and they will not allow anything to compromise safety.
I'm hoping that you realise 2 things
1) That V1 is NOT a fixed speed. It is dependant on a whole host of factors such as weight, runway state, runway length, flap setting and so forth.
2) Engine thrust is NOT a fixed setting. You can reduce thrust if you do not need all of it to save engine life. Hence if you are heavy on a short runway you use a much greater percentage of your maximum available thrust than if you are light on a long runway. However the net overall effect is the same. Put in very simple laymans terms you trade thrust for runway length depending on weight.
I really reccomend that you do some research on the balanced field concept. It is the crux of modern performance calculations. Granted it's not an easy concept to understand if explained badly, but all perf calcs are based on balanced field in one way or another.
I honestly think you have a basic misunderstanding of performance A calculations.
I will always do performance calculations based on the most limiting intersection i am likely to get. If i'm too heavy i'll take a less limiting intersection. If ATC need me to take full length for whatever reason i'll take full length. However i could take the intersection if i needed/wanted to without eroding any safety factors.
Also from your messages i believe you're talking about ryanair. I do not work for them, however i am lead to believe that their SOP's are second to none, and they will not allow anything to compromise safety.
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cortilla, thanks for engaging. Yes I realise those things but will admit to being terribly rusty on the finer points . I have looked at some PPRuNe archive where balanced field length/flex/de-rated comparisons are discussed, and even downloaded some 737 Perfomance charts. The reason I have not engaged much with the Performance arguments here (my mistake - laying myself wide open I guess) is because I think what I experienced was simply not normal for the operation. The performance numbers become a bit academic if airline ops have already indicated that full length take-offs are to be the norm at a particular airfield. Might that be possible or are commanders given full discretion without even occasional line recommendation on such things?
Remember that thus IS an airfield/airline combo where, once armed with the weather, the aircraft commander can usually choose (negotiate? but I really mean choose) a straight in approach even when earlier traffic may have been using the reciprocal only minutes before, and where he will 'choose' a straight-out departure on the reciprocal as often as he sees fit.
I sincerely hope it was possible on the day to rationalise our take-off using the numbers, but I do of course have a nasty feeling (which basically others have taken exception to) that SOPs or not, our 30 minutes late status may have (re-?) influenced our entry point at a late stage.
As I have laboured previously, we have never before in my memory taken off from that point, but I could be wrong
.
. I have looked at some PPRuNe archive where balanced field length/flex/de-rated comparisons are discussed, and even downloaded some 737 Perfomance charts. The reason I have not engaged much with the Performance arguments here (my mistake - laying myself wide open I guess) is because I think what I experienced was simply not normal for the operation. The performance numbers become a bit academic if airline ops have already indicated that full length take-offs are to be the norm at a particular airfield. Might that be possible or are commanders given full discretion without even occasional line recommendation on such things?Remember that thus IS an airfield/airline combo where, once armed with the weather, the aircraft commander can usually choose (negotiate? but I really mean choose) a straight in approach even when earlier traffic may have been using the reciprocal only minutes before, and where he will 'choose' a straight-out departure on the reciprocal as often as he sees fit.
I sincerely hope it was possible on the day to rationalise our take-off using the numbers, but I do of course have a nasty feeling (which basically others have taken exception to) that SOPs or not, our 30 minutes late status may have (re-?) influenced our entry point at a late stage.
As I have laboured previously, we have never before in my memory taken off from that point, but I could be wrong
.
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Firstly, as i far as i am concerend what intersection to take is always the commander's decision/responsibility (assuming that atc allow him/her to choose) Ops will never ever interfere. They don't know and don't care.
2) unless you're sat in the front with the performance books and all the rest of the information in front of you, you have no real idea what's happening. and can not judge or question the flight deck crew's decisions
3) as regard to tailwind. In my company the standard is to take no credit whatsoever for headwind and we'll take worst case scenario for tailwind if there is one (up to 10 knots). If atc will allow us to take offf via the most expedicious route (depending on inbounds) we'll take it. Some airports insist on you landing on the preferential runway up to a 10 knot tailwind. A perfect example that i'm familiar with is Ibiza. They want you to land on 24 up to a 10 knot tailwind and only then will you go on to 06, and it's perfectly safe.
Basically irrespective of what you felt was a problem, the departure would have been completely safe. Every single pilot i have ever flown with is extremely conservtive when it comes to safety. Even with the performance charts we have, we'll build some fat into the calculations and take the worst case scenario.
Understand balanced field and you'll really realise that the departure was not unsafe.
2) unless you're sat in the front with the performance books and all the rest of the information in front of you, you have no real idea what's happening. and can not judge or question the flight deck crew's decisions
3) as regard to tailwind. In my company the standard is to take no credit whatsoever for headwind and we'll take worst case scenario for tailwind if there is one (up to 10 knots). If atc will allow us to take offf via the most expedicious route (depending on inbounds) we'll take it. Some airports insist on you landing on the preferential runway up to a 10 knot tailwind. A perfect example that i'm familiar with is Ibiza. They want you to land on 24 up to a 10 knot tailwind and only then will you go on to 06, and it's perfectly safe.
Basically irrespective of what you felt was a problem, the departure would have been completely safe. Every single pilot i have ever flown with is extremely conservtive when it comes to safety. Even with the performance charts we have, we'll build some fat into the calculations and take the worst case scenario.
Understand balanced field and you'll really realise that the departure was not unsafe.
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I know I really shouldn't...but I'm bored.
And your problem with that is?
Remember that thus IS an airfield/airline combo where, once armed with the weather, the aircraft commander can usually choose (negotiate? but I really mean choose) a straight in approach even when earlier traffic may have been using the reciprocal only minutes before, and where he will 'choose' a straight-out departure on the reciprocal as often as he sees fit.
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lol spitoon if you shouldnt I should definately not.
What was it you said rainboe about preserving the language after shakespere kicked the bucket ?
Rainboe:
They have worked out their performance before they start taxy so they have decided where they will take off from and why.
They have worked out their performance before they start taxy so they have decided where they will take off from and why.
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Spitoon, I have absolutely no problem with it. I mention it only as an example to counter Forest Gump's (and others') box of chocolates ("you never know what intersection you're gonna get"). At this airfield, the commander pretty much has carte blanche up to whatever limits he sees fit. ATC will accommodate.
cortilla, thanks for the reassurance, but I maintain a degree of healthy scepticism with regard to human interface with the real world, especially when it's late and we're tired. Having looked at some numbers I am less worried now that this instance was a 'tight' fit, but I still doubt that it was planned very far in advance.
... as for taxy/taxi, taxyway/taxiway, taxied/taxyed I've been wandering around that with no better a rule than the one that says 'it's aviation, so use a 'y' unless it looks completely ridiculous!' And some days it looks more ridiculous than others
cortilla, thanks for the reassurance, but I maintain a degree of healthy scepticism with regard to human interface with the real world, especially when it's late and we're tired. Having looked at some numbers I am less worried now that this instance was a 'tight' fit, but I still doubt that it was planned very far in advance.
... as for taxy/taxi, taxyway/taxiway, taxied/taxyed I've been wandering around that with no better a rule than the one that says 'it's aviation, so use a 'y' unless it looks completely ridiculous!' And some days it looks more ridiculous than others
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s&t:
do you also critizise building engineers if you ever enter a buildings that doesn't look like other buildings? Surely, if you can tell that it looks different -- then it must be unsafe, or at least not "prudently built"? I guess it is obvious to you that the engineer chose not to put it the last few, vital supporting beams because he was late for dinner?
do you also critizise building engineers if you ever enter a buildings that doesn't look like other buildings? Surely, if you can tell that it looks different -- then it must be unsafe, or at least not "prudently built"? I guess it is obvious to you that the engineer chose not to put it the last few, vital supporting beams because he was late for dinner?
