Call V1 3 to 5kts prior

[Pugilistic Animus]

thank you Mutt,

I know that optimized speeds are available, but what if you have an 'older type' 737-200, 727, DC-9 etc.... that was granted certification under older rules---is such data available?

or do you/could you do it on a ad hoc basis--- optimize your V speeds? if you have BFL and UBFL data or is it too cumbersome or do any other caveats apply?

PA

edited to say---that I was thinking more of the older types in my original question---but I now know how to at least ask the question

[Jaxon]

3 to 5 knots before V1 is the only way for the two humans to react in accordance with the actions/decisions required at or before V1.

[john_tullamarine]

I'm on an ASD RWY for a given set of condition

Not quite sure what you mean here .. unless, perhaps ASD-limiting runway.

It still appears that you are trying to mix distances in the one calculation .. (mind you, it is late at night and I might be just a tad thick and not understanding where you are coming from ..)

For a given calculation (ie runway, OAT, W/V etc ...) if you are using BFL then you just calculate the various cases and the worst ( ie lowest weight) gives you the answer

If you have the (AFM) ability to unbalance the calculations (some AFMs don't give you the option so it is BFL whether you like it or not)

(a) you don't necessarily use ALL the TOD/TOR/ASD for the various cases .. some AFMs give you opportunity to calculate each separately (which means you can) while others (most) have a combined method of calculation which restricts the opportunity for playing around with the numbers

(b) by iterating the calculation (doing it repeatedly with variations in the input parameters) you can end up with the best weight for the day. Generally only one of the cases will determined the critical calculation


could you do it on a ad hoc basis

If, by ad hoc, you are looking at the pilot doing the calculations and optimising the RTOW, then that would depend on what data he/she has available (whether simplified ops manual stuff or detailed AFM) ... refer back to the earlier comments if you have suitable data.

Main thing is .. generally it is too long winded for the line pilot to run a full AFM calculation (not to mention plain tedious and boring) .. however, regardless of whether the calculation is AFM, ops manual simplified data .. or just looking up some RTOW tables ... the degree of unbalance (which is the same as saying V1/VR ratio) applies to all the calculation cases simultaneously .. ie you can't have different degrees of unbalance for the TODR, TORR, and ASDR by running the calcs for varying V1/VR as the calculation case varies .. would give inconsistent answers.

Or am I still missing the point which is of concern to you ?

[Callsign Kilo]

SOP with my airline - V1 call must be completed by V1. Something to do with Boeing studies into average reaction times when a decision to abort the take off at or just before V1 is made.

[Pugilistic Animus]

Professor Tullamarine, Sir---I think I need a little time to properly formulate my question---I don't think I know what I'm trying to ask myself---but something's confusing me---I'm trying to think how to properly formulate my query--with Mutt's reminding me of optimizing V-speeds---I THINK --that I mean to ask--from the engineer's view--not the line pilot's---how do do your own optimal analysis-?-when you have BF and UBF data---but no optimum data?


Thanks again,
PA

edited to write, I did indeed , mean ASD-limited----I think that Ssg in his various permutations, diminished my intelligence a bit---a made me a little fet

[TheChitterneFlyer]

Anyone would think that Take-Off Performance is an exact science; which at best is an averaged set of numbers that will give some guidance as to where you 'might' actually stop if it all goes pear-shaped.

Hey, three to five knots is probably a good range that an 'averaged fleet' might achieve; within a couple of hundred yards of that vital bit of runway that allegedly guarantees you stopping within the remaining 'stopway'... hence, eating dirt! Given that you and I have the same aeroplane, both of them will differ by an incalculable amount; therefore, does it really matter? During my Performance Course, many many years ago, I recall that a couple of seconds or so were factored into the numbers to allow for pilot recognition/response time of an engine failure... why beat yourself around the head with trying to get the words out in time when the response time has allready been factored-in? So what, if you're a couple of milli-seconds overdue in making the call; don't anticipate it... just do it! There will, in all probability, be a difference of a couple of knots between the ASIs anyway! Perfectionism is one thing... but let's not take it too far!

TCF

[Pugilistic Animus]

TheChitterneFlyer

Jet piloting IS AN EXACT SCIENCE---WE ---sometimes get it--- Tight, Tight---and maybe right down to the wire---hence the big bucks

PA

[Pugilistic Animus]

Wow, everyone seems to be an expert in error analysis----jus' compute[numerically, graphically, or functionally]--the second derivative of the relevant function---in order to find the ZERO SLOPE tangent to the curve and find the min and max tolerance values of your funtions---if you have an equation handy take the second derivative and set that equal to zero---do that for many hundreds of functions and report that data as---xxx0 units +/-.0023units--then submit that analysis to Boeing or Airbus--so that Mad Flight Scientist can then build a flight test schedule with their test pilots--once airworthiness certification of the ship and the AFM is done place---submit that data to performance experts like, Mutt, John Tullamarine, or Old Smokey--where they can then use the data to meet the air carrier requirements--so that the plane can be used to make money---You might require some rest afterward--but then YOU can do whatever the HELL you like at V1---until then

Get it, Got it, Good,


Those Slick Engineers!!!
PA

[Pugilistic Animus]

Airmen/Women

IF BY VI THE THRUST LEVERS [LET'S ASSUME THAT THIS IS THE FIRST AFM REQUIRED STOPPING ACTION--UUM KAY]---ARE NOT {{RETARDED}} THEN FOR SAKE YOU GO! GO! GO!

[TheChitterneFlyer]

Pugilistic Animus; been there; got the T-Shirt but the 'exact science' bit is a tad over the top.

I too have seen the very end of many runways; the fact still remains that at MAUW and a couple of knots prior to V1 and you call 'STOP'... you're into the stopway; no argument there I trust!

By the way, where do the 'big bucks' appear in the equation?

[Pugilistic Animus]

That's why those foolish Inginears--Dem Bums!--include the stopway in the EMDA or ASDA sometimes the EMDA is the ASDA--but no te preocupes--they'll pay for the bogies--don't pay for the bogies with your life---the NTOFP already had reductions in it do put more out on the other side ---tight--tight

re: pay don't you see the lil 'crackle tooth' smiley

[john_tullamarine]

when you have BF and UBF data---but no optimum data?

OK .. optimum is what the point of the calculation is all about. When you start with a particular runway, you don't know what the optimum is going to be .. although, for a Type with which one is familiar, an educated guess is not out of the question ..

(a) first determine the goal. Is it maximum weight ?, a certain pad of (ASDA-ASDR) ? ... whatever

(b) second use the AFM charts or software, as appropriate, to iterate TOW for the conditions until the goal is achieved

Repeat this for the range of conditions (usually OAT and W/V) desired

The specifics of how one goes about the actual calculations will be determined by the presentation in the AFM or the degree of flexibility associated with the software input.

Am I getting closer ?

[mutt]

optimize your V speeds? if you have BFL and UBFL data or is it too cumbersome or do any other caveats apply?

In theory, yes, it can be done by input selection, but you would have to list the speeds with the weight.

During my Performance Course, many many years ago, I recall that a couple of seconds or so were factored into the numbers to allow for pilot recognition/response time of an engine failure..

But do these regulations APPLY TO YOUR AIRCRAFT! Its all to easy to remember what we were taught in Perf A, but the reality today is quite different.

Mutt

[Pugilistic Animus]

JT and Mutt---between the two of you-I have my question answered in sufficient detail---I just like learning this stuff--I don't have an opportunity to use this stuff right now---but I enjoy the topic a good deal--thank you both for the responses I've learned a lot


Thanks,

PA

[TwinJock]

Yip. I think that each operator has their own way of looking at this. The problem comes when you are involved in a high speed abort situation, and things do not go well for you. The bean counters will be the first to kick you in the wallet!

My technique on the B777 - the ENGINE FAIL call is inhibited at V1 - 6 kts, which I think is the 1 second included for recognition of the failure. I remove my hand from the thrust levers at about 6kts below V1 speed. When you ask for guidance from the company however, it is stated that you hand should only be removed from the thrust levers at V1.

Mmmmmm!

[Pugilistic Animus]

read the thread!---why does everyone know more than Boeing

[cptpilot737]

We call " GO " 3 knots before V1, Company procedure......

[Pugilistic Animus]

why does EVERY ONE know more than MR. BOEING

[Jaxon]

why does EVERY ONE know more than MR. BOEING

It sounds like you figure you are the torch bearer of sanity.

Boeing is safe (and unambiguously correct) in making the firm statement about passing V1 and lever position/continued takeoff, but making a firm directive upon when a human should make a callout for affecting this purpose is not, nor ever will be, a hard and fast scientific calculation.

We want the pilot flying to know when his option to reject has expired (yes, of course, at and after V1). The only way for that thought to actually hit that pilot's brain in a timely fashion is for the non-flying pilot to get the sound waves in motion toward his ears BEFORE V1 in enough time for his ears to send that signal to his brain and for his brain to have sufficient time to register and recognize that call out. Some small margin before V1 is obviously required to do that to be the most accurate and compliant with the V1 decision.

Boeing takes responsibility for the science of their creations, beyond that, they merely help as much as reasonably possible and within their own lawyers' restrictions against exposure from creating over-reaching and rigid rules in the area of human factors.

[airfoilmod]

Pooge

Doesn't Bill say Brakes on levers back by V1??

Airfoil