Points to re-emphasise ..

(a) (unless the OEM guidance has changed in the past several years that I have been out of the training arena... please, someone, tell me if things have changed ?) there is a subtle difference between what the regulation appears to say and the practical application of the regulation. The OEMs expect the pilot to have commenced the stopping process by V1 for a satisfactory accel-stop manoeuvre. A simple legalistic read of the quoted reg implies just this.

(b) changes in regs are not retrospective. For any given reg, the TCDS MUST be checked to see what the regulatory basis for certification was .. and then you chase up the historical reg to get an idea of what the story might have been for the certification .. and, in the case of performance, one also needs to review the pertinent edition of the flight test guide to see what the FAA thought the reg might have meant.

(c) re screen height, indeed, if the takeoff is continued with a total failure prior to the scheduled Vef then the screen height will be compromised. Whether this will be significant or not depends on the circumstances.

Rulemaking - Harmonization JAR (CS) -FAR
 

For those interested in FAR the rulemaking and JAR (CS) - FAR harmonization discussion/process;following link could be of interest:
http://www.faa.gov/regulations_polic.../ACO_AP_T1.pdf

You have studied well, studi, and are to be commended.
Your airline has it right, in my opinion.
My present airline presents no particular guideance in this area, nor is any called for, as we (collectively) have been in the airline arena a very long time, and have the same general opinions as your carrier.
High speed aborts (especially at heavy weights) are the most demanding actions a Commander might take in his/her flying career and, for it to be done correctly, positive well thought out action is called for.

411A You say " your present Airline" That made me laugh as you claimed that in the Mid 70's you were a B707 Captain with Singapore Airlines and I have no reason to believe that was not so. That would make you at least 65 years old by now so please confirm that you are now grounded and are perhaps trying to supplement your income by being a Simulator Instructor??


411A, although one of the more colourful of our players in the sandpit, is entitled to the professional respect which is appropriate to his background. May I suggest that, if one doesn't have something more constructive to say, then one might hold one's counsel ?

John_Tullamarine
The circular referred to is AIC 151/1993(pink 91) 21 Oct 1993. If you try
www.ais.org.uk, it will guide you to subscribe. Of course, this circular was published before JAR's and so I recognise that amendments may have been made since its' publication.
The reference to the difference between this info. and FAR's in the accelerate-stop definitions is a mix of "Handling the big jets" and advice on take-off safety issued by the FAA in 2002, where I cannot find any mention of stopway distance used in the FAR calculations, but again I accept that this info. may be outdated, especially if JAR's and FAR's are being adjusted for similarity.
Whatever the calculation for obtaining V1, the crew should use this speed as a definite division between calling a stop or continuing with the take-off,
to do otherwise with the calculation, other than to use it properly, invites unwanted excitement.

An interesting article related to this topic has been published in Boeing's Aero Magazine no. 11 from July 2000. It can still be found on this website. The article is based heavily on the Boeing Takeoff Safety Training Aid mentioned earlier, but it includes some hands-on practice by an operator that has adopted the "decision speed" (= V1 minus 8kt) concept, with FAA approval.

tribo and skiesfull,

Thanks

studi,

One can approach the problem as an exercise in semantics or one of risk control and management.

The flight test world, in this exercise, is one of low surprise, nil startle factor and seeks to put a line in the sand regarding runway environment AFM data.

Real world and simulator study history suggests that the risk (for a accel-stop limiting runway) increases significantly as V1 is approached and exceeded. I have no problem accepting the thesis that a moderately skilled pilot, well trained and prepared for the emergency, will be able to achieve the AFM data in a controlled environment .. however, the real world doesn't replicate the certification controlled environment animal .. so one needs to be a little wary.

Semantics aside, survival is all about being sensitive to risk and risk management ... he who might blindly believe that the aircraft will do this or that might be setting himself up for a bad hair day ...

I know with which view I align.

xetroV,

I rest my philosophical case ....

It is a while since I last reviewed the videos but, if my recollection is correct, my library copies are of the Boeing and Airbus implementations of the FAA initiative.

One might expect, Millerscourt, that some would expect airline flying to end at age 60.
Oddly enough, this is not so, with many operators.
Indeed, on 23 November this year, ICAO will extend to age 65.
Still have two years to go, old boy...:ok:

john_tullamarine re 411A I would give 411A a little more professional respect if he did not try to kid us all that he was still an operating Tristar Captain!! He states that in Nov 06 ICAO will extend to 65. Well as it is only Feb that event has not happened yet!! The age 60 rule applies for US still and for most of the world. In UK because of France and Italy one is effectively reduced to the RHS if over 60. Sorry to hijack this thread but colourful 411A needs to come clean.
I would say 411A is closer to 70 than 65!!

Not suggesting that I am holding a brief for 411A or anyone else. Point is that, in this forum, we play the ball and not the player. All I am requesting is that we leave the personality discussions to other, more appropriate forums ?

AN additional 2 cents worth....

quote:

Inconsistent terminology has caused confusion about the V1 concept. An important assumption in the V1 concept today is that the decision to continue the takeoff or reject the takeoff is made before reaching V1. The accelerate-stop performance data in AFMs are based on the pilot flying taking the first action to reject the takeoff at V1.

The FAA said that the new definition of V1 states clearly that the decision to reject the takeoff must be made no later than V1. “Typically, the pilot not flying the airplane will call out V1 as the airplane accelerates through this speed,” said FAA. “If the pilot flying the airplane has not taken action to stop the airplane before this call-out is made, the takeoff should be continued unless the airplane is unsafe to fly.”

wrong or right.?
 

Just back to basics.

Most FMS, and I assume most chart data allows for a range of V1, from a V1Min to a Max V1. Not forgetting the implication of flex power.

So unless I am misreading these posts, it is suggested that a V1 speed below the published V1 min is to be used.

I agree with the post that we are not test pilots. Stick with the published data, and when the crash happens it will not be pilot error....

Bumz

Oh gosh, Millerscourt, you really are misinformed about age requirements these days.
It might surprise you to know the list of countries that do allow over age sixty Commanders now, and that list will lengthen considerably later this year.
It also might truly surprise you to learn that the flying world does not revolve around France, Italy, or even the US.

.. comment deleted ... just so I am seen to be even-handed ...

You really do need to get out more, old boy....:}

Girls, Behave !

I fly for a respectable charter outfit in the UK.

We have an arrangement with a Canadian airline where they supply to us, we supply to them during each of our respective busy seasons.

Now, a few years ago, I was an unofficial cultural and social attache to the Colonial visitors - thank you gents, you bought me ale !

There were some of their party, damn fine gents, who had passsed their 60th birthday, yet continued to operate in the left hand seat of an expensive jet over Europe.

So, my belief is that 411 may indeed be operating in the left hand seat beyond his 60th birthday, if so - well done, congratulations, you lucky barstard !

Life goes on, live with it :ok:

An interesting thread fella's (and ladies :ok: ). Lots to think about.

Recently did my Civvy licences (military at the moment) and the subject of V1 was brought up in Performance, with respect to Go/Stop at V1.

Now the answers for the exams were

"Below V1, in the event of a critical failure the take off MUST be aborted"

"Above V1, in the event of a critical failure the take off SHOULD be continued"

Now this seemed all wrong to me. The first one, of course, but why SHOULD and not MUST in the second ? The answer was that the aircraft captain retains the right to risk a high speed abort off the end.

Whether or no people agree with that statement is another thing, but the reason I mention it is because many of the guys doing these exams with no experience of commercial / military multi engine flying accepted it and moved on, whilst I thought it was vital to mention that in any case, the FO / CAPT WILL BE EXPECTING YOU TO CARRY OUT YOUR ACTIONS IAW CURRENT SOP's.

I just find it worrying that many people have little nuances or clever tricks that they feel they'll pull out of the bag in what will be the most intense and heart stopping few moments of your life. And to go off on a tangent with A level solutions that sounded good last night on PPRuNe will leave you working in direct opposition to the rest of the crew.

Brief it specifically or operate with the SOP's.

"Below V1, in the event of a critical failure the take off MUST be aborted"
"Above V1, in the event of a critical failure the take off SHOULD be continued"

I believe 'should' is correctly there because the PIC in command SHOULD continue the takeoff unless it is considered to be an unflyable malfunction, and therefore a greater emergency exists.

This last comment does appear in many SOPs you will find.

Cheers.

This is a very simple argument!

If you continue the takeoff with a failure before V1 then you cannot expect to reach your screen height by the end of the TODA.

With a failure, if you reject the takeoff after V1 then you cannot expect to stop within the TORA.

If you want to use techniques you have come up with yourself or which are not endorsed by the maufacturer, then be ready for some hard questions at the inquiry.

A bit of logic:

At V1 the abort must have been initiated.

Hence, abort must have started before V1.

In order to avoid a wrong reflex and comply with former statement (keeping in mind that a go-minded decision is the best option) I remove my hand from the levers slightly before V1.

Hence, I do glance at my speed indicator and do not solely rely on the V1 call only.

411 A is right.

Wet versus dry screen height?

If the dry screen hight has been set for safety reasons then why is the wet screen height allowed to be lower?

Answer: The regulator did not want to imply big weight penalties in case of wet.

Referring to the standpoint of the NTSB in the Southwest (latest Flight Intl) overrun this makes the use of reversers very interesting in the wet case.

The word 'should' in the definition above is there because the V1 go decision only relates to either a single power unit failure without safety margins or an all power units take-off with margins. It does not cater for either a multiple power unit failure or, perhaps obviously, a structural failure or fire. Using 'should' leaves it open to the pilot to reject above V1 in either of these events and accept a probable overrun.

While this may be arguably correct whilst sitting in the comfort of one's own living room it does tend to go wrong in practice. There have been several incidents where a surge has been misinterpreted as a structural failure and a completely uneccessary high speed abort has been called, above V1, leading in at least one instance to loss of life. I think 'should' ought be replaced by 'must'. In the case of the high speed abort the chances of getting it wrong are much higher than the chances of getting it right.

I do agree with FFP, whatever is done must be in line with the SOPs. If you don't like it - change the SOPs.

One point which should be noted .. in many of these discussions, comments suggest that a pre-V1 continue/post-V1 abort WILL compromise the distances. A necessary qualification to such statements is that the compromise will apply to the scheduled distances .. and unfactored, specifically. In the real world, the takeoff often is not limited for runway requirements and excess runway length compared to the scheduled AFM data may save the day.

The magic thought should be around the concept of lines in the sand and reference data .. which should be considered by the pilot intelligently in the circumstances of the day. By rote application of technique greatly simplifies things and reduces the incidence of strange responses to crisis .. but may not necessarily be the most appropriate or useful response on the day... and this point can be discussed as a philosophy until the cows come home ..

Well there I'm going to disagree with you, John. In the case of engine failure on take-off there's room for intelligent thought before the event but not at the instant it happens, by then all your decisions should be made. That's why its important initially to have carefully thought out SOPs and then to follow them.

Alex,

No need for disagreement as there is no basis for that.

If my previous words infer that I am suggesting seat of the pants routine decision making as the aircraft is yawing wildly while passing through 150 KIAS or thereabouts, then I apologise ... for that was not my intent.

The thrust of my comments was directed to the concept that by rote application of technique (as developed in Bat Cave exercises) generally is going to give the most reliably desirable outcome .. but not always. The knowledgeable and competent pilot ought to consider (pre-takeoff) the whole picture and determine his/her plan in the light of all the information .. a bit like the CRM philosophy when utilising the resources at hand.

Very occasionally, it will be appropriate to change that plan in the heat of the moment if the day is to be saved .. for example ..

(a) if, under post-V1 failure conditions, the aircraft is departing the side of the runway (eg near certification Vmcg in a strong crosswind .. which can easily put the real world Vmcg above the failure speed), then it would be prudent (probably) to close the throttles and do the best one can to stay on the runway and accept the possible overrun .. in lieu of rolling the aircraft into a ball at much higher speed during the runway side excursion.

(b) the O'Hare DC10 engine separation accident may have had a very different outcome had the excess airspeed been exploited .. no criticism of the crew intended as they only had a fraction of the story with which to work at the time and made the best call they could .. but it is noted that the accident report suggested that the situation only needed a few knots to keep the left wing unstalled....

(c) if a control selection results in a strange response reselection to the previous setting may get one out of whatever the problem is. One is reminded that the TP fraternity generally subscribes to the "loud noise (etc) = keep things as they are .. at least it is still flying" approach to survival.

.. and a substantial list of such examples can be generated without too much difficulty ...

History is dotted with exceptional feats where the folk in the hot seat did wondrous things .. in the heat of moment .. by keeping cool heads and being innovative ... for instance

(a) the Sioux City DC10 accident which, by rights, probably should not have got that far in the first place. Al Haynes and his offsiders earned their collective career salaries that day ...

(b) the JAL B747 .. OK, the crew didn't have a happy outcome .. but they kept the bird in the air for a long time ...

Its an interesting argument, but does it apply when you are using assumed temperature thrust reductions?
Mutt

In that case, I agree with you. The VMCG accident will happen one day, I'm afraid, and the O'Hare DC10 crash could arguably have been avoided with better training. Your other examples show the profession at its best but, unfortunately, for every incident where the crew pull a rabbit from the hat you can find another one where they underperformed.

.. ah, and that is the reason that we push SOPs, standardised training, and practised by rote responses so much .. all a matter of running the stats and playing the numbers game. For every rule we can find exceptions .. and for every unusual, but desirable outcome, we can find a bunch of unfortunate stories ... no simple "win every time" answer, it seems.

I was tought to say "Veeeeeeeeee 1. Emphazis on 1, giving about a second to prepare for the decision. 1 being said exactly at the actual V1 speed.

Knold,

You risk falling into a common trap of trying to make V1 (one of many aspects of flying which fall into this category) operationally far more precise than is warranted by the technical reality.

If there is plenty of spare runway, the reality is that a modest speed overrun probably can be accommodated.

If the runway is accel-stop limiting then there is scant pad .. especially for pre-A/L 42 certifications. Add this to touchdown zone contamination at the stopping end .. grease ... oil .... did it rain a bit half an hour ago .. etc., etc. .. and you are near guaranteed an off-the-end event.

Risk assessment and minimisation in the real world is the aim of the game .. the certification gives a baseline from which to work but makes no guarantees unless the boundary conditions can be replicated in toto.

So far as calling V1 is concerned, it should be little more than "hey offsider, my ASI indicates that I am passing the precomputed V1 .. hopefully yours says the same ?" ... the other pilot should have been keeping a very close eye on his ASI throughout the takeoff. Hence there is little point in doing other than saying "V1" relatively normally .. but timing, I suggest, should be such that the verbiage is completed by the time that the needle is at the nominated speed.... and let's not get too bogged down by IAS/CAS concerns ...

The company I fly for wrote, tested, and implemented the Reduced V1 procedure described in the Boeing magazine article. We compute V1 normally and then subtract 8 knots. The V1 call is made at the new computed speed. There was a lot of doubt in the pilot ranks at first but after one high speed RTO at KLAX we all became believers. It was obvious that another 8 knots would have put them in the sand dunes off 25R. It is just normal to us now. Like Willit Run the majority of our takeoffs are max effort, on the edge of everything. We even do over speed takeoffs and aft cg takeoffs with reduced screen heights to get that last pound of freight. Factor in old airplanes, worn tires and brakes, 59 year old reflexes and the 8 knots becomes more attractive. If I were flying short haul high powered new generation aircraft I might feel different. But if you are operating on the edge of the performance charts it is something to consider.

Of course it is more attractive with a lower V1 when stopping is the concern.
Why do people always do this?
If you set your V1 lower than than the actual, what do you do if you get a cut between "your" V1 and the actual V1?
You will have comitted yourself too early.


John, I didn't mean to come of as some german efficiency/precision expert... :}

Mutt,

It certainly does apply when using assumed temperature takeoffs. When the runway is longer than required for the weight, the thrust is reduced using assumed temperature. In effect you are using more runway than you would at normal thrust settings and the speeds would then again be critical for that particular runway length and weight.

Boeing training manual states that the call V1 should be complete by the time V1 is reached.....now how slow or fast you want to make it is up to the PNF/PM :suspect:

The technology is now available to abandon the use of the IAS for the go/ no-go decision.

Ground speed from the IRS-GPS.
Remaining distance.

It would be relatively easy to integrate the enery management and present the pilot with an easy go-nogo decision feature.

I didn't mean to come of as some german efficiency/precision expert

Pass, friend ..

The technology is now available to abandon the use of the IAS for the go/ no-go decision

Been the case for a great many years .. but the ASI is still a simple predictor .. especially if one has runway marker boards or uses the stopwatch to monitor acceleration.

Cue barit1's thread on t/off acceleration monitoring? No time to search and maybe wrongly 'attributed'?

Surely at or around V1 on balanced field figures ie flex, If you really need to go, you can always push the throttles up, and you will get off the ground a lot quicker....

ah, but therein lies a trap. If the engine is not thrust limited by some other means, you have the option of overboosting and, potentially, adding to your woes by pushing the Vmcg/Vmca up to an embarrassing value .. depending on circumstances, of course.

Investigated one fatal where this (Vmca exceedance) was a very likely major contributor to the flight's endgame ... in general, it is possibly better to set and leave the thrust alone for the takeoff .. unless there is more to the problem than a simple failure.

Sorry J_T, although the takeoff can be continued at a Flex/Derated thrust, we specifically advise crews that they can increase Flex/Derate thrust to the maximum rated thrust at any time they desire. VMC values are therefore predicated at the OAT in order to provide the required protection.

KnackeredII,
Don’t you have a buffer provided when using Derated thrust? Is there a difference in performance when using an assumed temperature of 50C rather than an actual temperature of 50C?

Mutt

In connection with Mutt's question.


http://i47.photobucket.com/albums/f1...r/e974cdf8.jpg

I'm sorry to say I didn't quite understand the table. Is the difference in IAS vs TAS due to temperature alone?

Mutt, in answer to your question, yes, there is a performance difference when using an assumed temperature of 50 deg versus full rated thrust when the actual oat is 50 deg.

For example, on a 50deg day for the CF6-80, the N1 is 106.3%. On a 25 degree day, derating to 50 degrees gives a figure of 102.1%. Why? Because even though you have derated the thrust, the fan still has to spin in the air density of the 25 degree day. The EGT to spin the fan at 106.3% on a 25 degree day would exceed the Takeoff thrust EGT limit.

Sorry to get off topic, but the question was raised...:)

I don't believe it 'better training' would have changed it. I believed the crew performed as they were trained.

There were multiple issues.. 1) the procedure they used as did many at that time was to climb at V2 or V2+20 as max speed and if you were above that speed, you increased pitch to reduce speed back to V2+20. 2) they were not aware that there was no lock-out with a hydraulic failure and when the hyd failed, the slats retracted. The combination of those factors, as I remember, created the roll for which there was insufficent control.

Both problems were addressed in the post crash findings.