Runway behind you - a way to save time?
 

I was a bit surprised very recently to find myself in the back of a 738 with 170+ pax taking an unfamiliar and hesitant taxying shortcut to a point 2300 feet down the runway (estimated from Google Earth). The take off roll was approximately 35 seconds and we rotated after about 4000 feet of roll with 1800 feet of runway remaining after the wheels left the ground (some 30 minutes late on final sector of the day I might add).

For what little time and fuel was saved in missing out the usual additional 2300 foot taxy, I personally would have preferred to have left the ground with 4100 feet remaining.

I have always believed that runway behind you is one of the most useless things you can equip yourself with before committing aviation.

Am I being unfairly critical?

Prudence is a positive trait the last time I checked.

This should be in tech log I would say.....

And being SLF I should not really comment, however I would say the following....

If your not happy with the taxi instruction you have the right to decline as pilot in command (you are in charge of safety of the plane) and request an alternative - if what is offered does not suit you dont take it.

If you were RHS, and you were uncomfortable with the decision made by the PIC the discussion should not be here but with PIC. It will always be unfamiliar the first time !

In general I would expect your right that the more distance you have for takeoff roll the safer, but economics does not always work like that - it will be a calculated judgement of safety over economy to a reasonable level I would speculate.

Sorry for my 2p worth.

Oh not this old chestnut again :rolleyes:

Listen, you got airborne, so there was enough runway in front of you to accelerate and do so. The performance calculations would have been done from the intersection, so if you had needed to stop there would have been enough runway in front of you to decelerate and do so. End of story.

Performance A calcs work, so let's just stop this nonsense about runway behind you, altitude below you, fuel in the tanks etc and move on to something that hasn't been done to death millions of times on this forum.

PIC
 

Slip and turn,

In short, yes, you are being unfairly critical.
You were a passenger and the PIC (well, probably both flight crew) made a decision that adhered to policies and law, therefore I think you are being a tad arrogant to assume that you would have 'made a better decision' by taxying the extra kilometre.

I don't tell everyone how to do their job. Do you? :oh:

In a Cessna 172 on a major airfield, do you taxy to the start of a 4km long runway, just in case? That would be ludicrous wouldn't it? Sure, not quite the same, but shows the logical progression of your thoughts. Intersection takeoffs are quite common because the aircraft simply does not need the extra bitumen in order to get airborne. V1/V2 are still within limits, so it's wasted runway...

Just my thoughts, let the professionals make that decision I say.

Matt

A tad arrogant? I can understand why many people could make that the default judgement. I do indeed see that some latenight moderator has made his or her judgement, and fairly stuffed the thread into touch, pronto-like :rolleyes:.

I am actually sick of seeing pilots hesitating during taxy at simple airports making up their mind where to go next. I don't mind a performance based decision smartly executed, if that's what it it might have been, but it wasn't.

Personally I think this was another late pilot at another simple airport where the big picture of taxyway layout and intersections between two parallel runways, one used as a taxyway by the jet traffic, just happened to escape him. We dillied and dallied and ultimately did nothing more complicated than leaving the apron on the exact same perpendicular that the aircraft entered on, crossing the parallel inactive directly from the apron, to arrive at the main runway at the exact point the aircraft left the runway when it arrived 30 minutes earlier on the reciprocal. Even when we reached the main runway it seemed someone was in two minds which way we would turn - right for takeoff or left for backtrack and take-off. Maybe it was just me of course having flown from this one too many times :p.

None of this is dictated by Smalltown's ATC of course - the airline often expresses its own runway preference 'on the fly' and as there's usually not much else occuring, take-off clearance is also often given early whilst taxying out.

As 2 or 3 or even 5 minutes surely can't be that valuable at the end of the day, I can only assume that perhaps a slot time was about to expire ...

Apologies to all the professionals - I missed the key " myself in the back of a 738 "

I will duck out now with head held low - my intentions were good but misplaced.

regards,

Jof

At busy airfields with several intersections ATC will frequently offer an intersection take-off to expedite traffic. Hundreds of flights each day take-off from such intersections without any problems. Keep in mind at that at a large airfield the length of runway remaining from such intersections is probably more than the full length of that at the aircraft's destination..

If only I had the powers to know what was going through other people's minds I might be able to make such pronouncements.

The reason for hesitation during taxying are many and varied - and if it is a matter of working out where to go next, I'd rather that than the aircraft heading off across a runway or whatever.

As for your concerns about the intersection take-off, I suggest you write to the Ops Director of the airline concerned expressing your views - and your professional competence for doing so - and I am sure that your concerns will receive the consideration they deserve.

PS - I guess it wasn't at LCY this time!

If your not a pilot then I suggest trawling through the tech log section and reading about balanced field take offs/flex take offs and intersection departures. Other keywords you will find of interest will be accelerate stop distance available or ASDA and TODA. Lots of light reading for the uninitiated that will hopefully enlighten you as to how commercial aircraft can expedite departure from an intersection and safely get airborne.

It must be a huge inconvenience to see the obvious incompetence displayed while assessing the performance of the flight crew from your seat in 36F!!!

On these occasions where you have experienced such hesitations in taxiing could you provide a little more detail please. Ideally of the airfield layout, the notams of the day regarding taxiway operation whether any additions were mentioned on the latest ATIS and how these related to the ATC taxi instructions provided. It would also help if you could describe the flight crew's familiarity with the airfield. Only so we can sit in the comfort of our own homes and judge the professionals with the same information you must clearly have had.

As for intersection take offs...Perf A calculations and NO airline SOP's countenance using runway ahead after V1 for stopping, so if the calculations show it is within the aircraft performance to use ANY intersection and it will save some time there is no valid reason why it cannot be used. ATC permitting of course (in fact often it is at their request!). Runway behind and fuel in bowsers are all wonderful generalisations of single engine flying. They do not apply in the commercial world where the decisions are much more considered and calculated.

Also as for 2,3,5 minutes not being important...safety is the primary concern following that is commercial expediency. Sometimes by not being able to take the intersection you may need to wait 15 minutes while 4 aircraft arrive and 2 depart from the full length. Did you have the big picture on the occasion or your intersection departure? Was the full length even available on that occasion?

So many questions slip and turn, and so many answers which I'm sure were clear to you from the cabin!

Happy flying.

Jazzy

I appreciate that there are a lot of you in aviation and interested in aviation who when down the back are blind, insensitive or just not very interested in where you are headed other than what it says on your ticket. That's just unluck on your part :p. I obviously think I have abilities that some of you are loathe to credit :8.

Anyway, this was no ATC instruction, and as such it can only have been some time-saving measure, and frankly guys and girls you are welcome to your own views of how it might have been rationalised.

At the end of the day, pilots are tired and want to get home, and I suppose if a slot expiry was imminent then there's the main reason.

It was actually still quite warm, probably 20 degrees, and there was no wind to speak of, but this runway is not elevated.

The runway direction for departure is rarely an issue unless there is a 5+ easterly component. So the airport layout gives the pilot just three potential taxying options:
(a) to the end of the runway via the parallel inactive (main taxiway a la Gatwick)
(b) to the end of the runway via backtrack from the entry point he actually used
(c) what he did.

For those who've added it up, this is indeed an 8000+ feet runway, like Gatwick, but with fewer entry points (just two at each end).

I just don't think that leaving a quarter of the runway behind you when you are not light is good practice. Last time I flew this route I wouldn't have been surprised. There were only about 30 pax, the take of roll lasted only 20 seconds and we launched up to FL400 pretty damn quick. We used the same runway but as we were on time, we went from the end. This time it was 170+ pax.

If a problem had occurred just before V1 then perhaps less than 40% of the runway would have remained available to stop.

Now, I know that even more heavily laden, the same aicraft might well regularly operate from runways 2000 feet shorter and where the temperature and elevation might be higher, but is it right to deliberately shorten your own runway to save time?

Why did I have the answer to this question once drummed in as a straight "No", and others have it marked as "It depends whether commercially you need to save 5 minutes" etched into their psyche? Or indeed 5 seconds in Spitoon's world? :ok:

Slip and Turn
From your post I take it that you are an aviation professional. Am I correct?

Part-trained/studied, but not earning my living in aviation. I pray that facilitates your next utterance, Mr Oscar :p

Slip and Turn you are missing the point completely!

No matter how perceptive you think you are unless you have all the information ON THE DAY, for that departure you have no idea what factors were affecting the aircraft performance or the reasons for the choice of departure point.

ADD's, packs on or off, peformance corrections with CDL items in addition to the actual airfield information rather than your perception of what is a 'normal' departure are the components that go to make the decisions.

Even with that information whether you think it is bad practice to save a couple if minutes or not is immaterial as long as the aircraft was operated in accordance with the performance calculations.


In a perf A aircraft whether you get airborne with 1000ft of runway ahead or 6000ft makes no difference. V1 is V1, there IS enough runway to stop if the decision is made to do so by that speed and beyond it irrespective of how much runway is still left you are going to fly over it!

I truly hope you are not an aviation professional because if you are you really need to go and have a close look at the books again, both Perf A and SOP's.

If you are not then please avoid your back seat speculating as to the inappropriateness of the crews's actions and let the people in the front with the information pertanant to your flight make their decision.

Asking a legitimate question as to whether the runway behind is just to save time and if it has safety implications is entirely fair. That has been clearly answered. Now you are arguing that the decisions made were not good practice...that to I hope is now clearly answered also.

Jazzy

Edited to add that my post crossed with Slip and Turn's regarding his aviation background. I think Eff Oh makes my point, finish your training, and leave commenting on the professionalism of the professionals until you join their ranks whereupon you'll find unless we have ALL the information...we don't!

Well if you know what is coming why did you start this nonsense thread?!?

You clearly don't know what you are talking about, so why do you continue to argue to the contrary??

How about waiting until you are fully "trained/studied" before commenting in such a way?

Sorry don't really get that. :rolleyes:

Foxtrot-Oscar ... ?

Do buck up, Eff Oh ...

JD
;)

Ah got you now! Thanks for that. Comedy at it's best. :E

Moderators- this thread is a piss take, isn´t it? A fishing expedition, by a dabbler in aviation, who from his seat in 21A can make judgements on his Captain´s decision on where to take off, and can tell from the movement of the aeroplane what is going on in the Captain´s mind? Who said ´there are no stupid questions, just stupid answers´? Look at this! This thread is quite clearly idiotic. The poster is arrogant in the extreme, and knows better than his crew. Rejected wannabees don´t have to inflict their bitterness on every crew that has the misfortune to fly with such a smart-arse sitting in the cabin! Delete this idiocy- not just close it! It is an embarrassment.

Ah thought we'd lost you there Mr Oh :ok:

But we seem to attracted the famous Rainboe himself now. And we all know if he doesn't like something, he says so. Good afternoon, Sir :ok:

Listen, I don't get up each morning and think 'whose good work can I criticise today?' ... sometimes in the course of the day, I just notice things done differently. I also know that once I am approaching flying speeds in something weighing 60+ tonnes and which normally uses most of 3000 feet or so to land and stop reasonably, that I'd rather have that and more available just prior to V1 than something only half as convenient. My sloppy '3000 to stop' may even have been there too in this case just before V1, but I reckon it would have been tight.

So what we have here is an observation of something unusual for this type at this airport. You'll have to take my word for that because I am not going to name the venue. The entry point used was unusual. Consequently, the rotation point was much further down the runway than is usual and a couple of seconds or 3 earlier just before V1, the picture of the end of the runway arriving would not have been much improved.

Unusual operations are usually a good enough reason to ask a question, so I did.


I'd be interested in some Performance calculations if anyone has the will. Let's be conservative: if anyone is feeling kind enough to provide some numbers to chew on, then what might they be for say 60 tonnes, NIL wind, temperature 15 degrees, and let's say sea level with 1022hPa? Runway dry of course. Qualify it with your packs and any other niceties. Anyone?

PS I am not a rejected wannabe, Rainboe.

<<You'll have to take my word for that because I am not going to name the venue.>>

Why on earth not? It might help people to explain things to you.

I fell about at your mention of 20 seconds roll then up to FL400!!! Apart from jet fighters and the odd clockwork mice bizjets I think I've only seen one commercial aircraft get airborne in 20 seconds and that was a Dash 7. In busy airspace not too many aircraft "launch up to FL400".

Heathrow Director, I do appreciate you've pretty much seen it all, but those 738's are blessed with an enormous amount of available thrust and if a captain wants to make a point of getting a nearly empty one heavenward in double quick time then if someone like me :8 is watching the second hand, they may indeed register a number as low as 20 seconds from application of what sounded like a goodly amount of power at one end of the runway to last rumble from wheels about halfway down. And with one as empty as ours, launching in not at all busy airspace up to FL400 is what the locos apparently do with their derring at every opportunity :p

Slip and turn...how much of this thread are you reading and just how much are you understanding?


You know what? :confused:

Why would you rather have something more available than the performance calculations require?

Apparently now you have moved on from:

to:

That was a quick change, without actually learning anything more about the situation you first described!

The rotation point was a couple of seconds BEFORE V1?????

You really need to read some more about aircraft performance!

Why on earth do you care about the picture of the end of the runway? This is not a Cessna 150 you were traveling in! Unless that picture involves a truck driving out in front of you it does NOT matter. The calculations will tell you if with the associated power and flap settings you can achieve the performance requirements for a Perf A airacrft on that runway from that intersection, NOT your perception from row 30 of how much runway is left.

I'd be interested too, but without an aircraft type and an airfield I think you'll find it pretty hard to get any!

Please Slip and Turn if you genuinely are training to be involved in flying aircraft take a very long hard look at the tripe you are writing, go and have a look at some threads or books about aircraft performance and see if you think it is appropriate to re-write some of your posts!

Jazzy

Wow, this thread really shows on of the most irritating things that I know as a professional pilot. When someone takes a step in to the flightdeck after landing saying something like: "that was a bit wiggly, wasn't it?"
A pilot for a serious airline would never do an intersection takeoff if he didn't know that he could make it safely. And what u described as hesitation of backtracking/lining up it is standard procedures, since the intersection distances are calculated from a different point than where the rapid exit taxiway centerline turns off the runway. We always have to make a slight "backtrack turn" to get the distance that is calculated.
The biggest time-saving is not won at the shorter taxi, but mostly from being able to get out before inbound traffic or other take-offs.

Now im gonna have to rush to work.
My first take off for the day will most certainly be an intersection-takeoff with my B738. (It always is at this base, pretty sure I don't need 3500meters)

Slip and Turn

If you are genuinely concerned about this matter, why don't you address it to the Director of Flight Safety at the airline you flew with? You would then at least be able to name the airport, the exact flight you took and you might even get a reply. I take it you also disembarked without raising your concerns to the flight crew?

Or do you simply like riling feathers by posting anonymously here?

JazzyKex, I am not going to engage with your lengthy dissection save for two things:
1. to say that you misunderstood my sentence that led you to believe that rotation was before V1. My poor English grammar I guess. Sorry about that.
2. to say that our exact progress down the runway as measured by me was by looking out the side window at known reference points, and the picture at the front is imagined.

You have the type, its the trusty 738. I've given you an airfield elevation - sea level more or less as makes very little difference. You don't need a name. There are no airfield related restrictions to be factored in.

If time and time again I feel brakes graunching (protesting) at the end of a landing roll on 25 at Stansted which has included use of reverse thrust on touch down, and that's apparently necessary in order to make the last fast turn off, then I can start making some assumptions can't I? I go to Google Earth and find the approximate median of the all the rubber marks at touchdown, and measure the distance between the rubber and the SR Technics fast turn off, I can hazard a guess that stopping one of these things from flying speeds with no wind to speak of uses up most of 3000 feet more often than not. Sometimes of course, it can't be done with any comfort remaining so we sail past to the end exit point.

So I am not one to unconditionally accept that if I possess Perf A calcs in my sweaty hand or programmed into my machine, QED I can leave 2300 feet behind me when I start to roll. If I notice that my wheels leave the ground with only 1800 feet of runway remaining, I might perhaps wonder if those Perf A calcs I relied upon were yer actual gospel. They might have been ... just ... if it is further a fact that another 1200 feet used post V1 to wheels off is typical. I don't know. Sounds feasible, if a bit tight.

Maybe the Performance figures do easily show that just before V1 I can indeed stop well inside my imagined/roughly estimated 3000. I don't doubt the theoretical feasibility of that either.

But my question wasn't "is it ok/legal?". I suppose the gist of my question was, to borrow a word from 11Fan's first take on the thread, "Is it prudent?"

Why did the crew of one flight out of very many similar flights decide to do something different which relied on reduced margin for errors/failures/safety with corresponding gain that could only be measured in time/economy?

Couldn't this entire slanging match been avoided by just one poster pointing out that, as 99% of airlines use Reduced Thrust for Takeoff :-

(1) If the full length had been used, the thrust reduction would have been MUCH greater, emulating a Field/Obstacle limitation, and

(2) As a reduced length was used, the thrust reduction would have been MUCH less, emulating THE SAME Field/Obstacle limitation.

In short, either of the Takeoff choices would have been operating to the same safety tolerances.:ok:

Sometimes.......................:ugh:

Regards,

Old Smokey

Guys, we are wasting our time here. He's not listening. :ugh: :ugh: :}

You would think so Old Smokey, but then the OP is well known for being an argumentative besserwisser.

The ensuing 'match' is obviously the very purpose of the thread.

I like Old Smokey's "sometimes" although I rather think he's referring to the way that sometimes threads really do make him want to bang his head, not how sometimes the two take-off choices yield the same safety tolerances :}

Sometimes, you just get the feeling that the pilot is slightly lost on the ground, or in two minds ... Rainboe mocks the feeling, as if SLF can't possibly know what is grinding the cogs. I imagine it's the same feeling you get when it's not your usual chauffeur who picks you up and he dithers at how to get around the usual obstacles and jams. Whereas your normal chauffeur just gets on with it before you even dream of looking up from your broadsheet in the back and saying "Don't dither man, get on with it!" :p ... never been there myself of course :E.

Besserwisser? Now I'll have to look that up.

Here we go again...

Thank you for clarifying that the rotation was after V1.

As for the rest of your post, you are still not grasping the concept that no matter how perceptive you consider yourself to be you did not know the circumstances surrounding the decision to use an intersection on the day you quote.

How do you conclude that margins were reduced in any way?

Did you see the performance calcs? If so were was they adhered to? Unless that is the case then I cannot see how any 'margin for error' has been reduced.


It is a little more complex than using a generic 738 on a generic airfield. If you want to find out if your crew were being negligent as you apparently think they were then we need to know FOR THAT FLIGHT the exact weights, configs, flap settings and the power settings they used and compare them to what you think they should have used! Ideally we need to see their company take off performance manual and the loadsheet...see Slip and Turn, it isn't enough to google the tyre marks unless you know which ones are yours!!!!


So what are you going to accept? Assuming your training continues and you intend to fly a commercial aircraft which manuals are you going to choose to ignore and which to obey? If the performance manual is not prudent enough for you then I suggest you ask why JAA regulations allow their use when clearly looking out of the side window at fixed points is far more accurate.

Sorry I forgot your back seat judgment is better than the perf calcs...


Are you trying to say that because on landing in Stansted using some reverse and after hearing some brake noise you pass a turn off occasionally that equates to RTO braking performance?

Please tell me that isn't what you are trying to say...

Slip and Turn, when no safety is compromised how do you intend your flight is conducted if not with regard to time/economy?

If you do get into the seat of a commercial aircraft you'll find that safety, time and economy are very much at the forefront of your daily thoughts!

The brakes certainly would protest at such a landing not to mention the various buildings and hangars etc you would be ploughing through on your landing roll :p

BTW is the airport in question Edinburgh? I have seen and been in countless intersection departures from there without incident.

Yes Old Smokey it probably could but clearly our friend doesn't trust the concept of Perf A and has little understanding of its use and I suspect One Outsider is closer to the truth...

Anyway it's giving me somewhere to rant while watching some very mediocre ladies tennis! :ok:

Oh dear, really rocked your boat I see, JazzyKex !

I simply estimated that at least half the rubber put down at Stansted was by 738s. It was an estimate ... you know that e-word you use for all your load weights apart from the fuel I guess?

Yes if you want to make things deliberately complicated for a rough answer then by all means include some flap settings/configs/whathisnots.

My training isn't continuing, JazzyKex. I'm a "don't-wannabe". Workplace politics are bad enough on the ground without walking into a job which places you in the thick of some of the worst workplace politics, but expects you to be constantly at the top of your game with regard to safeguarding lives down the back.

Are you a wannabe, JazzyKex? Cos you seem to have a great knack of getting hold of the wrong end of various sticks. You are right about the tennis however :ok:

No boat rocked Slip and Turn and no sticks grabbed by the wrong end either.

I'm not trying to make the calculations complicated...just to explain that to assume that anything was being done without prudence would require you to know exactly what the circumstances were.

As for the estimates made for loads...just assumed weights for the men and women which err on the side of safety in the same way the Perf calcs have factors of safety built in with assumptions about aircraft performance.

As has been mentioned before safety is the priority and has been built into the system of performance calculations to negate the need for second guessing the validity of the data once it has been gross error checked.

As for choosing to be a 'don't wannabe' fair enough. I can't say that I've encountered any politics in the flight deck though. We leave that on the ground and in the hands of those that prefer their perch behind a desk rather than up front where we spend more of our effort in considering the expediency of intersection takeoffs!

Here's hoping Azerenka can stop it being an all William's final....

From post # 1.

Yes, as a matter of fact you are. Intersection takeoffs are done every day all over world and they are completely safe.

Offending a Profession
 

Slip and Turn,

I think what you will find is that whilst there is no penalty in asking a question, there is certainly going to be a backlash when you make accusations of unprofessionalism with extremely limited and subjective evidence.

To assume that pilots are tired and just want to get home 5 minutes earlier by compromising safety and performing intersection takeoffs contrary to policy is absurd.

To assume professional 738 drivers are 'confused on the taxyways' simply due to taking a different non-direct route to get to the TO runway is equally absurd. Were NOTAMs in effect? Was there garden maintenance vehicles near Taxiway F? How can you tell from one side of the back of the aircraft?

Credit where credit is due mate, these pilots are highly (and completely) trained professionals operating under strict safety regulations which are first priority ALWAYS. To assume that an intersection takeoff and indirect taxi equates to a tired and confused pilot is naive and offensive.

Please feel free to ask the question you asked, but be respectful of the answer, or don't assume incompetence/unprofessionalism straight away. That's offensive. :yuk:

End rant. :*

Matt

Folks, this whole stupid thread has been a trolling expediton, with a troublemaker knowing how to tweak sensibilities here.

Don't feed the troll! I don't think I have read such stupidity on this board before. It is designed to cause a hysterical reaction. Ignore.

No, no, Rainboe, you can learn a lot from knobbers like this. First of all you can learn to persist in illogical arguments, despite the fact that your question has been answered by professionals. You might think those exams you took and the every-day use of Perf A calcs are important but, as you can see you're wrong. So, from Mr K.Nob you can learn how an aircraft REALLY gets airborne by counting the number of seconds (whilst seated in row down-the-back) and comparing it to how it usually feels. He's done this many times, so what would the operating crew know. What's even better, is you can also learn all about auto-brake settings. Not from the landing weight, vacating distance, turnround time versus brake temps etc but, no; now you can learn using Google Earth.

On second thought, you're right. S&T you are a tw*t. You've got your answer now piss off to some Microsoft forum and discuss how real professionals do it.

If you do a search on him/her then you will see a trend of posts with a common enough link. Lots of posts on BA038, Turkish at Schipol, Ryanair depressurisation, ground collision, Coventry incident and the like. Trolling no doubt to get a rise and or research a story as Rainboe points out.