DJ 419 ADL SYD 1500/10th Nov

[grange.guzzler]

Captain

Given that the preceeding QF had not even lined up when you arrived at the holding point, what did you save by taking the significantly shorter intersection departure. The time to taxy to full length (23) would be about as long as the minute and a half you had to wait at the HP.

GG

[go_dj]

Well son we like ontime departures, can't be dawdling along
taxiways like browns cows can we. :D

[splatman]

Laugh my ass off :D

Now thats what I call an appropriate reply!

Well said go_dj, after all, if the RTOW says its approved, then I would say the rest of the decision making lies with the crew involved.



:ok:

[Cactus Jack]

Yeah, hilarious. Then you guys go straight up to F410 every time, whether there are headwinds or not.

Runway behind you, air in your fuel tanks and altitude above you.

[loungelizard]

Hey Grange,
Why dont you go and refamil yourself with the definition of V1, where and how it's measured or were you observing from a piston prop where you have to start on the clearway before the threshold to get any performance, and then you prob dont know what I'm asking anyway !!!!

[Sperm Bank]

God almighty here we go again.BORING,BORING,BORING

Grange, the crew worked out the RTOW figures well before they arrived at the holding point. As you would well know?????????
Most times we are cleared for t/o without too much hassle. If there are a/c on final and nothing much to be gained the crew might request the full length on approaching delta. The figures GUARANTEE we will stop before the end of the runway if rejecting prior to V1. So there is NO intellectual (or otherwise) case for not performing intersection departures. All performance figures are as I say GUARANTEED.

There may be any number of reasons why a crew may decide not to use an intersection departure. It's up to the individual Capt in addition to a discussion with the f/o. So grange why the interest?

[Doctor Smith]

He was just pissed that they might have got away a little sooner.:}

Like we do with T3 departures on 34R YSSY when they amble down to T6.:} :}

[amos2]

It's the difference between being a Pro or not!

[Cactus Jack]

Actually LL, on the 737NG Boeing use Balanced Field Length Figures. They are only applicable if the TODR = ASDA.

Otherwise the figures can be manipulated to achieve a higher V1 if a greater TODA / ASDA is available. But I'm sure you already knew that. Moral to the story, had the guy used a greater runway length, he could have achieved a higher V1 speed.

Probably not a good idea to throw stones at our piston bretheran just because they sling off at a Virgin aircraft. I've seen many other operators do just the same.

[Col. Walter E. Kurtz]

or a schoolgirl.............nya nya ne nya nya!!

Why don't you guys have the balls to have a go on the ramp? Now THAT would be worth watching!! biting, scratching and screaming.

Better still, single warrior combat:

QF's best Vs DJ's best, caged of course, by the old firestation at YSSY.

Decide once and for all, then never utter a word again!:}

[splatman]

Still laughing my ass off :D

Cactus you may think that I work for DJ but I dont. But I do find it amusing that the spirit of competion is so fierce amongst the two groups that this type of stuff gets posted.

No slurs on the professionalism on either side PLEASE, I'm sure the RTOW would have been consulted and the decision for an intersection at Delta was a professional one.

Hey Col Kurtz, you could sell tickets to that event if it ever occured!

Mind you, this is the type of stuff little boys get sent to their room for! :E

[The Bullwinkle]

SPLATMAN,

Just don't send them to their room when they are watching a Spiderman DVD......................................

[blueloo]

Sperm Bank said:

The figures GUARANTEE we will stop before the end of the runway if rejecting prior to V1. So there is NO intellectual (or otherwise) case for not performing intersection departures. All performance figures are as I say GUARANTEED

Do they Guarantee you will perform 100% as expected to stop the aircraft according to the appropriate and expected stopping methods? Or that another fault which may have caused the RTO will allow you to stop in the appropriate conditions....Or that some other influence will not affect the a/c's stopping ability ?

I always thought many RTO's ended in prangs due a/c not stopping in time despite the aircraft performance figures GUARANTEEING that the aircraft will stop.

Seems like a very confident and or (more likely) stupid statement to make IMHO.


I could be wrong of course, but then again, I am not Guaranteeing that I am correct :D


[BTW my comments are w.r.t. "Guarantee", not about full length or interesection departures as the figures will? adjust V1 based on length available. ]

[loungelizard]

Your point Cactus !!!??????

I dont give a hoot if he flys a jet, piston, toyota crown or leyland P76. Stupid posts taking the piss out of people making a professional and appropriate judgement call, require a stupid fu#king reply. !!!

[Cactus Jack]

You just answered yourself LL with that post.

I'm not convinced that GG was "taking the piss" as you so eloquently put it. He had a valid question, and he has a right to it. Same with me.

Since you don't seem to wish to understand my point I will courteously spell it out for you.

Taking full length is an airmanship decision which allows a higher V1 speed, and often greater margins.

LL, your post towards GG was insulting, as was your last to me. You should learn some manners. Have a nice day....

[Sperm Bank]

Amos, "the difference between being a pro or not" Given your anti DJ slant on most things I think most discernable intelligent people would laugh whole heartedly at your comment. It is is a farcical thing to say and you know it.

Blue loo, stupid is as stupid does. How much study and research have you done on RTO's? I wont descend to your level by brandishing insults such as stupid. Many RTO's end up in an incident MAINLY because the crew do not perform them correctly eg rejecting AFTER V1 (has happenend plenty of times), taking too long to reject and working out incorrect data to name a few. The FACTS are that if an a/c continues the t/o even with a failure BEFORE V1, it will generally be able to continue and return to land normally. MOST operators in the world use intersection departures when they are available. It saves time and money and does not in any way jeopardise safety. I have a document with 45 a/c accidents detailing mistakes by crews close to or after V1. I am not aware of any accidents where the crew decided to continue before or after V1 and didn't make it back sucessfully.

No one can predict what each individual pilot will do during a reject. You will notice some of the more experienced drivers taking their hands off the thrust levers just before V1 is called. They know that statistically it is better to take a problem into the air.

So with regard to your comment "seems like a very confident (or more likely) stupid statement, it is neither. It is simply the FACTS. A/C can SAFELY depart from ANY intersection the RTOW/ RWY analysis manual determines.

[Beer Can Dreaming]

Cactus jack, Im not going to wade into an airmanship argument with anyone but interesting that you mentioned Balanced Field Length.

Yep, intersection or not BFL is the worse possible case.(Accelerate Stop Distance Required [ASDR] = Engine out distance to reach 35 ft).
Some guys still insist on pushing things closer to the limit unnecessarily but still the decision rests with the PIC, although its still legal.
Even though legal some guys consider this wreckless and mention the word "cowboy" but each to their own.

I see international airline guys do it all the time, take the "F" intersection on the western side of Rwy 16R (Syd) and hold for five mins before the cabin is ready when there is no traffic between them and the full length.
With some 600m of runway wasted you see these guys disappear from sight over the hump only to reappear on TCAS struggling away over BBay.

If someone wants to take the intersection which in this case was legal then so be it.
Others may judge but dont know the facts (ie: pax numbers/weight etc).

[Pass-A-Frozo]

I still like the brown cow remark :E

[cunninglinguist]

If the use of an intersection lowers the V1 to below balanced field, without any other gain, then I defy anyone to come up with a good explanation as to why that is good airmanship.
Runway behind you is just as useless to a heavy as it is to a lighty if the V1/VR split is 20 knots! ( or whatever figure you care to pick )

As was mentioned previously, the figures in the book ( albeit with good margins ) are arrived at by test pilots, not Jo Average ( or below average ).
The amount of RTOs that turn into runway over runs/accidents is quite alarming, regardless of the reason.

At the end of the day why would you want to reduce the safety margins for no gain ?

[Hugh Jarse]

So I assume de-rated takeoffs are poor airmanship as well gentlemen/ladies?:E

[FatEric]

The individual take off charts used by my airline are based on max V1 – also known as overspeed Vspeeds.

Therefore, for those concerned about rejects – using the full length achieves nothing. The aircraft will come to rest at the same point along the runway. The only savings made out of full-length departure being reduced take off EPR.

If your aircraft is at a weight such that 1500m of runway is required – why not take an intersection with 2500m remaining instead of 3000. You lose nothing.

“At the end of the day why would you want to reduce the safety margins for no gain”

This scenario does not necessarily reduce safety margins and it can result in gains – avoiding an extra 5 mins taxi time and a 2 min wake turb wait has just saved your company money.

And besides, safety margins are reduced every day you go flying – it is a business.

[blueloo]

Sperm Bank said in his first post and here it is again.

The figures GUARANTEE we will stop before the end of the runway if rejecting prior to V1. So there is NO intellectual (or otherwise) case for not performing intersection departures. All performance figures are as I say GUARANTEED

Sperm Banks second post:

Many RTO's end up in an incident MAINLY because the crew do not perform them correctly


But wait a minute, you just said the figures Guarantee we will stop before the end of the runway...................hmm I wonder if they really do .


As i gaze back at my now rather tatty and old trevor thom performance manual, it rambles on about assured performance of transport category a/c. (no mention of guaranteeing anywhere i might add) But WAIT, a disclaimer in the book - However, as with many other critical situations in aviation, the aeroplane can only perform to its certified standard if operated correctly by the pilot

It also mentions other factors may affect this assured performance....

So yes the figures are assured to be correct. Are they Guaranteed ? No I dont see it written in my companys manual nor a reference to the figures being guaranteed in the CAO's. I also see a training text book indicating that factors may influence the assured figures. So who is correct???


Who knows eh. Yet I still dont Guarantee that I am correct.

[grange.guzzler]

Some interesting responses. Thanks to all who took the effort, but as yet the original question has not been answered.

go-dj departure was on time.

Splatman No argument about the RTOW approval. The question asked was “what was saved “ it wasn’t time as we could have gone to the full length in the time we waited.

Cactus The adage is an oldie but a goodie. BTW after 5000+, I ceased being a piston bretheren about 15,000 hrs ago.

Lizzie About the time I was coming to grips with V1/V2, delta V, overspeed V2, second segments and 20.7.1 (b) etc, you were probably just starting to use pastels and crayons.
Just cos the book says you can do something does not make it the most sensible course of action. If there is some compelling reason to shave the margins go for it. However if there is NO advantage, why put yourself closer to the edge.
To follow your rationale, we should be lobbying CASA to have the 30 minutes mandatory reserve abolished, after all we never need it, and it really is a waste carrying all that extra weight. Heavens, it would even make our intersection departures safer because of the lower weight.
Refer to the incidents I will detail at the end of this.

Sperm Bank Yes I do well know that the RTOW figures have been calculated before you go.
If you believe the “guarantee” bit, I have some really good real estate spanning Sydney Harbour you may wish to invest in.
Refer to the comments above, to the reptile.

Dr Smith refer to go_dj comment.

Amos 2 Glad I am not a lone voice

Col. Walt I am neither QF or DJ and although I really don’t give a fig as to the outcome, I would put my voice to the DJ cause in a fight to the death.

Blueloo and cunning linguist Thanks

Beer Can Dreaming The point is, nothing was saved/gained and a safety margin was removed.
Hugh When you use a derate you still have the option of calling in the extra thrust if required (not necessary by certification, but available none the less) whereas when you have left the extra bitumen behind you, there ain’t no way to retrieve it. From an engine longevity point of view, good airmanship WHEN conditions permit. (something gained, as opposed to the current question where nothing was gained other than about ¾ mile unbraked rolling wear on the dunlops)

Fat Eric In my experience that is a unique way of handling V1 unless you are also using an overspeed V2. Are you working in areas where an improved second segment is required.
Would suggest you analyse what you wrote re coming to stop at the same point on the runway.
Are you suggesting that reduction of EPR where available is not a good move. Refer to comment above for Hugh.
In this case there was no extra time to go full length as DJ had to wait for the preceding QF.

Incident 1 Rome /CIA. MD80. Takeoff 300lbs below max for conditions. Wind shifted from slight head to moderate downwind about ½ way down the runway. By the time acceleration stagnation was noted there was insufficient runway to stop from SPEED BELOW V1. Takeoff continued clearing opposite end approach light by an estimated 20 feet. Not the 35 feet GUARANTEED by RTOW for takeoff at heavier weight.
Had intersection been available and used, catastrophe.

Incident 2 MD 80. Highspeed reject ABOVE VR. No control response to elevator input. Had intersection been used overrun inevitable.

Incident 3 Limiting strip. Takeoff continued with inadequate elevator response and stability due excessively forward Cof G. Control barely maintained until cabin load shifted aft. Had an intersection been available and used, catastrophe.

I can vouch for all these incidents as they have all happened to me.

I’ll continue to take the full length thanks, unless there are significant reasons as to why not.
I would rather be a live chicken than a dead cock.

GG

[whipping boy]

Why does QF always use Juliet in ML,when full length is apparently better,why does QF always use A7 in BN when full length is better and if it was a northerly in AD which intersection do you use?

[grange.guzzler]

Whipping Boy

Who knows why QF do anything in particular???
Perhaps you miss the point with this situation though. Nothing was gained by using the intersection. Time was near enough the same. (Give or take 20 seconds)
Departure was from 23.

GG

[DIVINE WIND]

Sounds like you all have such an exciting job. Yeah, this is really a thrilling topic.:ouch:

[loungelizard]

Wooooff Cactus, if you were insulted by that, I would hate to be the poor human stealing your next car park. And actually Cact, I did have a nice day. Talking about airmanship and insults, why dont you ask Grange why he did not just add the crew name and the amount of Pax's to the original heading.
DJ 491 ADL/SYD 1500/10 Nov. It would have been much more PROFESSIONALLY appropriate and use of basic AIRMANSHIP to state something as "737 ADL intersection dept" rather than plaster Airline, flt no, time and date all over a public and worldwide forum.

Grange, take a note of the comments above and thanks for the thought and I hope the crayons and pastels for your sake go back to the early 60's.

[MoFo]

GIRLS. GIRLS.

All this is unbecoming. Try to act with a little decorum to your fellow aviators. Whogivesa**** ?

[loungelizard]

How very true MOFO, but it's good to see who takes the first big bite eh.!!!!!

[longjohn]

I have said it before and I will say it again.

It is sad to see the respect that existed between crews now dissappear with the arrival of the LCC. I cannot put my finger on 'why' but it would seem that there it a definite level of animosity between the two 'major' domestics in Australia. I so not recall this being so in the Ansett days.

[Watchdog]

At the end of the day, if the paperwork says it works you wont lose your house if there is a prang.....but at the court case, the man in the black robe, wearing the curly white wig asks you, as you are a professional, exercising your duty of care, to justify your actions....if you are confident that you can convince the court...go for it. (all BS aside, we all know that if time and cost was irrelevant we'd go the full length, etc) :cool:

[cunninglinguist]

Actually Fatman, the difference between intersection and full length wake turbulence is 1 minute, or zero minutes if you're in a real aeroplane.

The difference between taxiing intersection and full length at AD RW23 is as stated about 30-45 secs, maybe you are still remembering your ab-initio instructor saying " never taxi above walking pace " ??

" safety margins are reduced every day you go flying, it's a business " thanks for that, If I ever leave my current position that sounds like a doosy of a line to use at an interview.:ok:

In our airline, we actually strive to increase safety margins every day, a bit old fashioned I know, but it seems to work.

[FatEric]

Cunninglinguist,

It is the arrogance and condescension in your reply that makes pprune such a happy little place.

I will respond to your post with more manners.

Although the example given at the start of the thread was referring to ADL, I was thinking more in general terms.

For example, in WSSS where I operate, runway 20r is occasionally used for dep. In the A/C I fly, using full length is never required. Obviously we use it in the wet or for heavy takeoffs.

BUT – normally it is unnecessary. At most departure weights, using the 1000 m intersection will result in the same EPR setting, the same V speeds or less, the same flap setting and the same terrain clearance – i.e., water.

However, it saves a couple of minutes taxi time at the very least, and more importantly a couple more minutes taxi time following the usual line of SQ 777’s on the way to the hold – they do taxi at walking pace. It also saves brake wear and tire wear.

Can you give me an example of how your airline is striving to INCREASE safety margins? Carrying more fuel. Higher experience requirements for crew. Reducing duty periods, increasing rest periods. Lowering the allowable takeoff weight of the aircraft.

I am keen to know.

[oicur12]

So, Cunning, What if they were doing runway works and you had no choice but to use the intersection - would you go back to the gate then.

[Sperm Bank]

Good reply fatboy. Some of these know it all Australians are an embarrasment and god only knows what they would be like to fly with. "we strive to increase the safety margins every day" What a pompous load of garbage!

Long john quite correct. There is a good deal of anymosity and we certainly never asked for it. SOME of the incumbents just cant stand the fact that something new and different is undermining their little comfort zone. Very very sad!

MOFO. decorum?? some of these guys wouldn't have a clue what it means.

Jarse, still laughing at that one. yeah mate by definition some of these gurus would have to believe that derate is not safe or professional as rated thrust.

Grange. Your point is correct but as i said, they worked out the figures for DELTA and then requested a taxy clearance for DELTA. They would not have had a clue who was where at that stage. Once going around the corner and seeing the conjestion they probably could have changed their minds but obviously decided not to. Does it really matter? The answer is nothing was saved this time round. Every time I have done that departure we have been cleared for a rolling t/o so saved plenty. It sounds as though you don't believe the performance figures from the a/c manufacturer. I do belive the figures I extract from the rwy analysis manual and as a bit of insurance, our company makes us use a temperature 4 degrees below the temp we could use (at the planning stage). If there is 1 knot of taiwind we will use 5 kts etc. All built in SAFETY margins. You sound as though you have been around a bit. You would probably also know that a fully laden jumbo rejecting just before V1 can stop in a surprisingly short distance. It will probably blow all the tyres (from the heat) but the performance is quite impressive.

Blueloo. I couldn't be bothered responding to your derogatory negative attitude.

Do people have to explain every action they take or can we just go to work for the enjoyment of it? This country is descending so farcically low into the depths of sub human behaviour it defies comprehension. Pilots dobbing other pilots in for PERCEIVED indescretions, ATC dobbing pilots in for pedantic rubbish. Where are we going lads and why do you want to go there? By all means ask valid and relevant questions but for gods sake lets keep the conversation subjective and de-identified.

To the QF pilot who emailed me regarding the bat incident in Cairns, thank you very much. Informative and to the point.

[blueloo]

You just couldnt be bothered or guaranteed you couldnt be bothered?


:} :}

[splatman]

SPERMBANK

SPOT ON ! :ok:

[Next Generation]

SPERMBANK,

Well said. I think that GrangeGuzzler is probably unaware of how high performance aircraft are operated. It probably doesn't affect him in his Chieftan or Seneca.

[PPRuNe Towers]

It tooks years and many deaths to get the airframers to accept that performance figures had to be created with part worn brakes instead of brand new. Hard to believe as it defy's all logic but they fought it tooth and nail keeping proven lawyers in work for years. This happened well into the widebody era. The same for turning on allowances as we enter the runway. Elsewhere in the world we're still fighting for Vmcg/a figures to reflect snowploughed runways entirely legally cleared to only half their width.

And with that background set let's look more closely at the discussion here:

Firstly - a visit to the darker recesses of the tyre manufaturers sites will tease out the information that all bets are off on their products if taxying for more than 5 or 10 minutes dependent on number of corners taken. No guarantee due to internal tyre hysteris. Vmbe is fantasy if the tyre makers shrug their shoulders and disown you.

Secondly - V1 stop figures are just not created from the work of test pilots on the type of runways you or I know. They are operating from steam and chemically scrubbed runways. When was the last time you saw your favourite touchdown point cleaned - not swept - cleaned??

The viscious braking preventing an overrun is happening on exactly that rubber, fuel, and oil contaminated touchdown point for the opposite end. Film melts, the oil products lubricate it further and we get rubber reversion to liquid. Your performance data was not created under those conditions.

So - those guarantees? Please think about it.

Regards
Rob Lloyd

[cunninglinguist]

Chuck( fat ) Yaeger, you've just agreed with me. I said using an intersection that reduces V speeds or obstacle clearance etc is bad airmanship, you say that the intersections you use don't reduce any of these values, so whats your point?? just a bit of Oz bashing, oh, and was'nt the thread predicated on AD RW23 ??

We have check and training meetings every three months with more often than not, new and improved ideas about SOPs, looking at other airlines incidents and accidents and trying to learn from other peoples mistakes rather than making them ourselves, constantly trying to improve/standardise checking and training, looking at results from surveillance and what areas we as a pilot group are falling down in, revising and improving LOFT excersises in the SIM , yada, yada, yada.

Oicur5 and Sperm, no reply.... you are plain idiots.

Do me a favour, let me know which airlines you guns fly for so I never put my family on them, on the off chance they get you as part of the crew.

Jarse, yes, if the derate lowers the V1 to below balanced field it is bad airmanship, smartar5e

Pprune Towers, these blokes don't need clean runways, their talent/ability more than makes up for that.

NG, let me guess, 2 years ago you were in a metro??, now the RHS of a jet and you are already an expert............nice to be judged, is'nt it ?

[Dehavillanddriver]

To all you armchair quarterbacks, something to think about.....

Was the aeroplane AT the limit weight? if not there is some margin built in...typically the aeroplanes depart a couple of tonnes below the calculated limit weight because of the allowances made at the planning stage....

Secondly, in terms of obstacle clearance, there are no significant obstacles off Runway 23 at Adelaide....

Thirdly, where do you draw the line... If you were taking off from edwards Air force base with a 10 mile long runway would you always go full length in case you reject? NO? Well where do you draw the line. The people on the day made a decision based on a number of factors, the primary one being what the analysis manual said... from memory the D intersection gives you about 2300 m (I stand to be corrected though), does that mean that you would never take off from Cooly at 2000 odd metres? Or runway 27 in Melbourne - I assume that you always take full length 34 or 16 because you MIGHT need it, even though the analysis manual says 27 is OK for your operation.

Flying aeroplanes is an exercise in risk management, we as pilots make considered decisions everyday, and we make those decisions based (mostly) on sound advice from manuals, training etc.

PS grange Guzzler, people in glass houses spring to mind - without knowledge of what was going on you are making an uninformed criticism of the crew.

You are not an aviation consultant and or television commentator by any chance are you?

[Keg]

Without getting into the nitty gritty of it all there is one point Ii'd like to make.

DHD, you're absolutely correct about the 'risk' management- although I prefer to call it 'threat and error' management- with a side order of 'benefit' thrown in! ;) I guess the difference is that by going to the full length decreased the 'threat (which I acknowledge was relatively minor) with no loss of commercial benefit. All of aviation has to be weighed up in 'threat' and 'benefit'. What is the threat of the intersection take off? Is it worth the benefit (and there often IS a benefit) is the next question that has to be asked.

What is the threat of intersecction, greater than full length. What was the benefit? Increased taxi way utilisation for company aircraft? Decreased taxi time and therefore greate schedule reliability? From what I can see in GGs example, there was nil benefit. Therefore, why not lower the threat a bit from 'low' to 'virtually nil'.

[FatEric]

Cunning,

You are a twit. Oz bashing – I am an ozzie. Whats your point.
Yes, the example was ADL – I haven’t flown in oz for 2 years and have forgotten the numbers – runway lengths etc.

Is terrain clearance less from adl 23 intersection. Cant remember but if it is – so what.

CASA allow it. AN,VB,QF all allow it. The ops engineers spend a lot of time and money drawing up intersection charts to enable it. I have seen all airlines do intersection departures from DRW,SYD,MEL,ADL,BNE,CNS and others I guess. Is terrain clearance compromised. I guess so.

If you define professionalism as always doing full-length departure in a lightly loaded short flight twin jet then good for you. Most others apparently don’t.

[ftrplt]

do any operators change their V1 with de-rate? I would be most suprised.

[PPRuNe Towers]

I spend a week each year at Boeing. I see the performance courses at both grades and know many graduates of them. Without exception skilled and dedicated people but they believe in the numbers and would offer up their first born such is their faith.

However, they are not at the pointy end.

I'm glad Dehavillanddriver offered up the example of Edwards and, as you're all using the internet, I'd like you to take a look at another runway - Moses Lake. It's significant because, as yet, Airbus don't have much penetration into the Oz market.

Use the free satelite imagery viewing sites to look at the runway - all 15,000 feet of it. That's where your performance figures were derived. Note the witness marks for the tests and the parallel nature of them as the TP's sidestep to get clear pavement - it is a competiitve business and they want the best figures possible.

Once you've viewed the images here's the sum up:

They are not performing RTO's on the caked contaminated crap we face but the figures are based on those conditions you see there. We do not have the luxury of sidestepping the touchdown zone on our real life runways.

For many intersection take offs it doesn't matter if you are tonnes underweight - the touchdown zone is where we are all applying maximum braking, the tyres (remember them?) are now very hot and we are digging them into the contamination while still a more than a thousand feet from the stop lights and the antiskid has ensured we're now carrying an even coating of crap with us.

Nobody is denying these takes off's have their place in operations but a wide eyed acceptance of performance data is very dangerous. The figures are as much the domain of the marketeers as the flight test department. There is no other reason for them to spend the last generation fighting all efforts to make them reflect the real lives of folks on the line.

Finally, for those of you into the extreme sport of competitive derating - have you ever researched - or your company passed on - the reductions in N1 or EPR that actually extend engine hot end life versus the thrust settings that are mere willy waving? Some interesting work on the subject that never reaches those on the line. Again, you're viewing this on the internet and you can google your way into knowledge if you care rather than just here to enjoy taking a poke at each other.

Here's the real performance calculation:

Intersection + willy waving derate + contaminated upwind touchdown zone + long taxi with multiple turns = baffled performance engineeer telling us it was the pilots' fault coz the figures said you could stop.

Regards to all,
Rob

[Nolights-essential3]

Sorry Cactus, but your appreciation of TODR vs ASDA is scant to say the least. Firstly you are using apples vs oranges. Even if you said TODA vs ASDA, your so called 'balanced field' definition is wrong.
Lets pretend, for a moment, that you meant ASDR = TODR, I may buy into that...briefly, but thats only a definition of a Balanced Field, and operationally not all that common or desired. For instance, if you had a runway with obstacles in the 2nd, 3rd or final, and a subsequently reduced TOW for the grad., then why the hell would you want a balanced field? A long rwy like Sydney 16R for instance will bring you into a Brake Energy limit before you get to your other limits, and MTOW becomes the operational limit. Again your Balanced Field theory is devoid of reason. If you want to screw with your V1 / VR ratio to achieve this, other factors will prevent you from doing so. May I quote my boeing AFM.......
"The takeoff distances for this airplane are unbalanced because the V1 for a balanced field would normally exceed VR with anti-skid operating"
Now, 'wet' rwys can be a little more tricky, but watch your definition of 'wet' on groved rwys.
Further, and all Required / Available lengths aside, to judge the reasoning for departures from other than full length you must know all the factors effecting the performance of the airplane at the time.
What was its Actual TOW?
.....its limiting TOW - and its always nice to know if its RWY, brake temp or Obs related.
....and the margin.
So, and I hope I haven't bored you too much, the answer to why DJ did what they did is quite as simple as the ol' "Why does a dog lick its nuts?"
cheers
3