Flightdeck distractions
 

Interesting article from Flight International about Flightdeck distractions.

Distractions frequently cause flapless take-offs, NASA reveals

AA

In terms of accel vs. time checks, there are a couple of things here:

1. Accel vs. time is going to be simply a function of excess thrust over weight, surely. It will not indicate where you are, or should be/have been on the runway. Unfortunately, a position on the runway is what we need to know -and is effectively what V1 gives us (assuming correct acceleration), based on ambient conditions.

The question then becomes "When we get to V1 will we be at the correct spot?' Waiting until V1 to see the result will only tell you whether things are about to go badly, or not, so:

2. We need a distance to go vs. speed check, again based on ambient conditions, at a convenient point prior to V1. Unfortunately, current wisdom has seen distance to run markers all but disappear. Bugger-they were quite useful for landing as well..

Perhaps there is a possibility of an acceleration rate check, based on ambient conditions and groundspeed, driven by GPS/RAAS and triggered when the TO/GA switches are pushed on departure? Something for the boffins...

As for the 777, yes, the airspeed trend vector is very useful, though nothing is formalised regarding its use on takeoff, other than as a windshear indicator, or did I miss something? As others have said here, it's a good crosscheck, nonetheless.

Now that might work, but I go back to a point I made earlier - it would still have to a calculated point based on inputting the same data, hence subject to the same error.
Would guard against P1 malfunctions resulting in lower than indicated thrust though. EG The 737 in Nauru or the Potomac crash.

Nice one centurian!

We used to do time check to 80kts when flying Hercs off an unimproved strip. The NAV would start a stopwatch at the beginning of the takeoff roll and at eighty knots either say CONTINUE or STOP depending on the time taken. The timing was, of course, worked out well before the take off started and was usually around 12 seconds dependent on all the usual variables.

It worked well until you rolled into a boggy spot at 90kts!! :sad:

I can't see why something similar could not be done for RPT ops.

Regards,
BH.

NO LAND 3 has the answer if you're operating EFIS with speed trend vector.

Correct! And that's because the speed trend vector will usually show predicted airspeed in 10 seconds based on current acceleration! OK, it may vary from type to type, but normally at heavy weights and at about V1, an aircraft is travelling at about 200 to 300 ft per second, so it's therefore accelerating at 3 to 6 knots per second.

Therefore, if the speed trend vector is showing (about) 30 kts predicted speed increase, then acceleration is probably OK and about 3 kts/second.

Remember though, that the above is an 'approximation' only, and to be totally accurate you'd need to get SPECIFIC figures for the type that you operate. However, like all 'rules of thumb', the 'approximation' is probably fairly accurate in practical terms for the purpose of determining whether take-off is 'normal'!

Folks

WRT integratin' the augment crew with the operatin' crew there's a lotta high spirited barkin goin' on but the fact remains that the A345 is a two person flight deck.

The SOPs taken from FCOM 3 make no reference whatsoever to CM3 or CM4, there is only a CM1 and a CM2. CM1 and CM2 are further allocated duties by reference to wether 'er not they are PF or PNF. Period. This is the way the manufacturer certified the aircraft and the regulators agreed.

The FOM, Ch 14 has some interstin' stuff regarding this and you kin bet that from AAR down they'll all be havin' a good study of it. Fer reasons of corporate confidentiality I won't be referin' to chapter 'n verse, nor will I publish it on this here forum. Suffice to say it's a document that like most of what this company writes give one more than enough rope ta let ya hang yerself with. It's airy fairy 'nuff to screw somebody over perty good, but it don't specifically define responsibilities an' it don't take in ta account what might be happenin' when the engineer is in the centre jumpseat completing the tech log with the fuel figgers or what might be gettin' handled in the cabin on behalf a the opertin' crew by one of the augmenters... say chasin' down stuff fer the CRC or gettin' the walk around done er whatever. It's a pretty grey area.

As the poet says: I ain't so wise as those lawyer guys... but I reckin' that the augmenters got a pertty good case for being let alone here.

That's ma two bits worth

Some more comment on what happened :
Airbus A380 Tail Strike Test




Unfortunately or ... fortunately :

Very interesting, thanks for posting that.

The Velocity Vector is not Enough
 

I have to admit this accident/incident bothers me tremendously as I have thought about this issue of performance assessment on the takeoff roll for some time.

The velocity vector is a useful "secondary tool" but until the specific performance specifications using the V.V. are documented and mandated by the manufacturer as a check item on takeoff roll, to my mind its' use is "vague" at best. In fact, to my mind it is only slightly better than the "seat of the pants" judgment many experienced Captains currently use to judge the rate of acceleration on a given takeoff roll on a given day.

The V. V. is based the aircraft's computed future speed based upon a current rate of change of acceleration over a given time frame projected forward ("XX speed" will be achieved in "XX time" projected forward based upon current the current rate of acceleration).

This vector is totally dependent upon the performance data criteria selected by the crew in the flight management computers given the actual a/c weight and current runway length, field elevation and airfield wx (temp, wind and QNH).

Case in point:

If I were to take off at MTOW in any given aircraft (A-319 through to A-380 or Boeing equivalent up to 747-400) on a 20,000' runway at sea level at ISA wx conditions, you would expect a max flex t/o (irrespective of weight given the runway length) and a minimal "benign/subdued/non-aggressive/etc?" velocity vector displayed on the PFD during the take off roll through 100 kts given the conditions.

Take that same a/c and put it on an 8000' runway at 6000' above sea level and the velocity vector for the same given weight on that runway would be considerable different. How much V.V. on the PFD is right at that weight on that runway length at that temp at that elevation on that day? How much is "not enough"?

Under a different scenario, what if you take the same a/c on the same day at a "simple airport" (long runway, near sea level, normal temps, etc) and make a gross input error (due to crew fatigue/distraction/etc) in the computer inputed ZFW or max TOW data to calculate the performance figures?

Unless experience tells you to expect that based upon the given aircraft type, field and wx conditions, and actual t/o weight you should expect a V1 of "XXX", a configuration of "XX" and a V.V. above 100 kts of "XX", you might be happy to see "100 kt + your comfortable "XX" amount" on the V.V. on the takeoff roll and be totally wrong in your assessment.

My point is that using strictly V.V. without some specific manufacturers numbers to match up your "seat of the pants" assessment of it's use is to my mind incorrect and should not be relied upon to assess performance takeoff criteria.

The real question is why have the manufacturers not published the performance data using the velocity vector as it is something that is easy to document (at the manufacturers level) and the display of the data ( the Velocity Vector) is already a part of the modern airline cockpit?

Why have Airbus and Boeing not provided airline crews with this easily produced and readily available data?

To my mind that is the key issue in this incident and one that Emirates, all other airlines and the regulatory authorities in every country must contemplate in assessing fault for this incident.


Dune

time CX
 

C130 operations - a long time ago in my career - on short field ops we calculated exactly that event - time to 80 kts( for example)

the nav called 'time' with the precalc'd seconds and you either had the speed 'go ' or you didnt - and 'stopped'..

it picked up runway condition / slush mud etc - not entirely relevant to civil ops but the point is there.

I notice we get bogged down starting the friggin clock when we roll the jet ( apparently so we can monitor take of thrust - or time to next coffee break or something??)

Unfortunately it seems that no matter how fool proof the engineers try and design something their model of the real world is continually tested.

I think the highlight of Dairy's post was the observation of how 'non standard' our attitudes and beliefs are with regard to how standardised we really think we are...but arent..?? sorry poor english again.

Several of these posts comment on the lack of incorporation of 4 crew into a 2 crew system - ad hoc etc.

This surely needs to be addressed? more eyes, more seen, does not make.

some really good posts guys ... keep thinking there are some excellent ideas out there..

failed to meet miserable standards he sets himself..
 

did I used to fly with you - think I repeated your post!!!

Woodja!

That's The Point
 

If it isn't in the manual, maybe it should be. Maybe the folks who write the "training manual" should pick 100 knots or something below V1. Then calculate how long it takes to get there or at what distance marker (if there are any). It looks like the guys flying this one could have used something like that.

Agree.
Might even have saved the Manchester United team at Munich
Has been promulgated countless times, after overshoots and 'just made its'
Remember particularly in the 70's when it was being considered
Military use time to distance a fair bit or speed at runway marker

Rules of thumb are enough, we're not talking 3 decimal places !

A320-200 Tunisair - near tail-strike
 

Not the same A/C, not the same WX and a different carrier and location ...... but nevertheless interesting and instructive for me to see what happens to this Tunisair A320-200 when the spoilers deploy.

YouTube - Almost tail strike Airbus A320-200 Tunisair

Apologies if this has already been posted or is deemed irrelevant.

Quote from this article :
An examination of the US confidential aviation safety reporting system (ASRS) shows that, since 2000, 55 take-offs have been carried out unintentionally in the USA without take-off configuration having been set ...

In that perspective, I must say Airbus developed an excellent concept to avoid that kind of event and I would not think any of these 55 cases came from an NG Airbus ... (?)

I wonder what the sea level stopping distance of the A345 at 360 + tonnes is from V1 at, say, ISA + 10 ?

African or European, laden or unladen?

I think Trimotor came closest to a practical suggestion here. But I keep coming back to my point that any check has to be calculated for each take-off using the same variables as the original take-off calculation. IE it will vary for type variant, weight, departure point, slope, rwy surface conditions - the list is long!
So it will be subject to the same input error and be pointless.

If the input is correct then the performance will be correct. I suggest we are concentrating on the wrong end of the problem.

We should be thinking of how to ensure the correct figures make their journey from the airport data and loadsheet...to the performance computer...to the FMS.

That is the key. So simple and yet so full of human factor traps...

WHAT is the flight velocity of...

Don't get me started Trimotor!

Velocity Vector
 

I was thinking..

What if we just look at this in simple kinematics terms (not sure of the spelling).

We can create a table that we enter with Vr, move across to TORA and find a resultant IAS 10 second trend minimum.

OK I know this is really vague but if you run the numbers it is interesting that you get a vector that can be anything from 10kts to 40 kts.

These are minimum averages and are independant of weight or conditions. A completely different input from that used in the LPC calcs.

So I start a take off with a fugure of say 25 kts in my head as a guide for this runway/Vr combination.

Just a thought.

SQ changed the procedure for checking and rechecking performance data after an investigation of contributing causes to the Auckland accident.

NOT SURE if what happened in Melbourne to EK is the same thing, but it does seem sensible to suspect this accident has a very similar genesis.

Planes don't mysteriously disappear or crash. This isn't a tv program. It's the real world. Something went wrong, and the probability rests with that something beginning with the input of erroneous data.

Not that I'd know. I wasn't there. But if I was a betting man...

On the subject of accelaration rates and what not, NO LAND 3 has the unequivocal answer. "Don't screw up the input."

Others are talking about all sorts of novel ideas. Why? Are you trying to reinvent the wheel? The analysis of performance characteristics is faultless. Got that? Faultless.

Applying the analysis by way of inputting the derived data is another thing altogether. Why make it harder? Why reinvent the wheel? The data's all there in the book. All it needs is to be accurately transcribed into the FMC. And there's the trap: all it needs...

I'm with the low viz guy :ok:

US Patent 6175315 - Aircraft takeoff acceleration indicator system

Inventors
Millard, Wayne C.
Millard, Carl W.

Application
No. 180473 filed on 11/10/1998

see Aircraft takeoff acceleration indicator system - US Patent 6175315 Claims

Claims
What is claimed is:

1. An instrumentation system for use in aircraft, during the takeoff roll from standstill to V1 speed, that continuously displays a target airspeed at which the aircraft should be if it is meeting the acceleration required to be at V1 at the anticipated distance, wherein a related computer with a database stores information on curves of takeoff acceleration graphs of the type and model of said aircraft with respect to speed versus time on said takeoff roll as well as distance;

an actual airspeed display continuously displaying the actual speed of said aircraft wherein, during the takeoff roll up to V1 speed, said computer continuously controls the progressive movement of target airspeed display in said actual airspeed display, to display the target speed at which the aircraft should be if it is meeting the computer-stored acceleration curve based on time;

and a display for continuously displaying the computed distance that said aircraft is currently lagging behind when said actual speed is less than said speed at which said aircraft should be if it is meeting said computer-stored acceleration curves.

2. An instrumentation system as claimed in claim 1, further including an instrument panel having an indicator to continuously display said actual speed of said aircraft, and a needle to indicate said target speed.

3. An instrumentation system as claimed in claim 2 wherein said indicator comprises a reference line.

4. An airspeed display as indicated in claim 1 wherein said target and actual airspeeds are displayed on a rotary dial type airspeed indicator.

5. An airspeed display as claimed in claim 1 wherein said target and actual airspeeds are displayed on a tape type airspeed indicator.

6. An airspeed display as claimed in claim 1 wherein said actual airspeed is displayed by a reference line and said target airspeed is displayed by an arrow generated from said reference line.

7. An airspeed display as claimed in claim 1 wherein said target airspeed is no longer displayed when said aircraft reaches V1.

8. The display of claim 1 wherein said airspeed display is an electronically generated readout.

9. An instrument for use in aircraft, during the takeoff roll from standstill to V1 speed, that continuously displays a target airspeed at which the aircraft should be at if it is meeting the acceleration required to be at V1 at the anticipated distance, wherein a computer with a database stores information on curves of takeoff acceleration graphs of the types and model of aircraft with respect to speed versus time on said takeoff roll as well as distance;

an actual airspeed display continuously displaying the actual speed of said aircraft wherein, during the takeoff roll up to V1 speed, said computer continuously controls the progressive movement of target airspeed display in said actual airspeed display, to display the target speed at which the aircraft should be if it is meeting the computer-stored acceleration curves based on time;

a reference line against which said actual speed of said aircraft is displayed, and a needle to indicate said target speed;

and a window in said instrument for continuously displaying the computed distance that said aircraft is currently lagging behind when said actual speed is less than said speed at which said aircraft should be if it is meeting said computer-stored acceleration curves.

10. An instrument for use in an aircraft, during acceleration of the aircraft from 0 velocity to V1, for continuously monitoring actual velocity of the aircraft versus target velocity of the aircraft required to accelerate to V1 within an anticipated distance from a standstill position comprising:

(a) input means for entering parameters affecting an anticipated distance from the standstill position required to accelerate to V1;

(b) comprising means for calculating from said parameters;

(i) a V1 value for said aircraft;

(ii) anticipated distance from aid standstill position required to accelerate to V1;

(iii) time required to accelerate to V1; and

(iv) target velocity continuously required to accelerate to V1 within said time required;

(c) means for operably storing said V1 value of said aircraft, anticipated distance from standstill position, time required to accelerate to V1, and target velocity continuously required to accelerate to V1 within said time required to accelerate to V1; and

(d) means for continuously and simultaneously displaying and monitoring the actual velocity of the aircraft and the target velocity required to achieve V1, comprising a linear readout airspeed indicator having a reference line against which said actual velocity is displayed, and wherein an arrow generated from said reference line displays said target velocity;

(e) means for displaying continuously the actual distance said aircraft is lagging said aircraft's actual position behind an anticipated position determined by the anticipated distance from the standstill position required to accelerate to V1.

Maybe this is what's needed? :}

Thanks for that. :D


Smilin_Ed already said it: It doesn't really matter what speed is chosen/SOP'd, as long as it's before V1 and you have time to react before decision time.

The military distance to go siteboards were(are?) great for what they were designed for, but are not suitable for current civil ops. For example, they'd be totally useless in a limited viz takeoff, which is very much a part of any airline's operation these days, and, if anything, is a situation that cries out for some such 'acceleration check' system far moreso than a CAVOK takeoff. Remember the days when we always did TOGA takeoffs in such conditions? (Whatever you come up with, gentlemen, let it NOT be another female voice cluttering up my headset. Miss *** RAAAS - another 'slam the stable door after the horse has bolted' extra we've had added to the system, blocks or partially overrides far too many ATC calls as it is. Hands up all those who'd like to see all her airborne calls dispensed with?)

Coming up with some sort of simple calculation for the trend arrow on the PFD is probably the most promising suggestion, although I was taught by the man who first endorsed me onto the 777 a very long time ago now (a 'personal extra' on his part, I hasten to add, that is not to my knowledge mentioned anywhere in the Boeing documentation), that anything under a 15 knot value on the trend arrow means something is seriously wrong and best you do something about it.

Any 777 pilot will know that, except on the highest AUWs and at the most marginal of conditions, the trend arrow is usually well above that, as much as double it. However, it's one of my 'little extra things' that I check on every takeoff, a bit like that last look on short finals that there really is a 'gear down' indication. (I don't care how many bells, whistles and other aural warnings Boeing have built in to the system to prevent a gear up landing, it's just another one of my 'things', part of the 'belts, braces and chastity belt' approach I take to most of my flying as the 'old' has increasingly replaced the 'bold' in my operation.)

I'd have to agree with quite a few others that the current situation during the 15-20 minutes before doors closed with an augmented crew on board is far less than ideal - (and Mutley, your 'take' of the number of people coming and going to the cockpit during that time is far different to mine). I can recall one very senior EK checkie (Robin H.) telling me, many years ago now, that he'd counted one day the number of interruptions between his taking the seat and pushing back. It was 27. I don't believe things have changed since. Just an example: on your average trip, how many people do you usually have come up to the flight deck to ask if they can close doors, even after you've called the CC who's manning the door on then interphone to give the go ahead?

After starting out with the attitude that, as augmenting crew, I'm an extra overseer on the flight deck, I'm now very much one in the 'stay off the flight deck as long as I can prior to engine start' camp. Unless you dibs the right jump seat, you're at best, very much in the way and at worst, a distraction to the operating crew.

I don't think we, the Great Unwashed, will ever see it in print, but I believe the CVR of those 30 minutes prior to engine start on this flight will make for some very interesting listening - and not just in the most obvious areas - for the investigators.

380 drvr, fair point; but that doesn't prevent a worst-case calculation being used as a rule of thumb does it? Perhaps this would then be a meaningless figure...

Gentlemen,

I think the EK SOP's regarding loadsheet and T/O data entry are foolproof. If guys mess up they clearly didn't follow the SOP's for whatever reason.
I am not saying that I never made a wrong entry, and quite often I find an error in the TO data, BUT, I trap these errors because of the SOP's!

The only thing that might to be changed is the order. I's prefer us to get the loadsheet, check the numbers and only then do the T/O figures.

In the loadsheet procedure, we check DOW, ZFW, TOW, ZFWCG and ECAM CG together. After that the F/O checks the ZFW again by himself.

For the LPC: the F/O prepares the data and writes them down, the Capt checks them and inuts them, then crosschecks with the numbers the F/O wrote down.

The weight should have been checked by both, and to finalize it, we do a GREEN DOT check.

Don't get me wrong, I'm open for improvements, but we check, crosscheck and have a final 'redundancy' in the green dot check.. how far do you want to go?

If something needs to be improved, it is the disturbances during the preparations which gets us out of sequence or skip things... If operations could be a little bit more streamlined, the fuel and tech log should be finished at least 20 minutes before departure. (considering we should get the ZFW around 40 minutes before STD). By then the loadsheet should arrive and the crew should have the following 10 minutes without anyone coming in the flight deck to brief and do the loadsheet/LPC check.

---

The A345 is a 2 man operation, and I would advise everyone to keep it that way. Recently a B747 cargo operator had almost an identical mishap, scraped the tail, but because it was a cargo, not too much fuss about it in the newspapers. In the following investigation, it came to light that the augmenting guys had 'helped out' with the T/O numbers and got it wrong. They left with speeds for 100 tons less then their actual weight..

---

Even to consider to abort a T/O around 100 kts because the acceleration 'doesn't feel right' or the trend vector is not showing what I expect should be punished by the electrical chair in modern airline operations. (slight exaguration :E )
Let me explain myself a little bit:

First of all: a jet engine does not produce the same thrust at different speeds with the same thrust settings, basic thermodynamics. Your acceleration (even in a perfect world) will initially increase, then decrease again. So you can not put a certain number on the acceleration itself.

Second: The trend vector is coupled to the AIRSPEED!! So there you are on a rather short runway, hitting a negative windshear. Your trend vector will be less then expected and according to quite a lot of guys above, a reason to stop the take off. Your groundspeed on the other hand might be a lot higher then you think and you would set yourself up for an overrun... The only good action would be to slam the TOGA and fly the windshear maneuver.

Acceleration monitoring can only be done with special equipment for that purpose only. Should be coupled to RAAS so the equipment knows what the runway is like. But again, it is dependent on weight, so as someone posted before, if the crew puts in the wrong weight, all the systems will fail to pick up the error.

The only thing that would make sense is the aircraft weighs itself. It can't be that difficult to put some kind of weight measurement in the struts of the mains. With the cg known to the aircraft, a gross error check can be made by the aircraft, e.g. only accepting TO weight that are within a preset margin of the actual measured weight. It doesn't need to be spot on, so no need for expensive very accurate 'scales'. As long as it picks up a significant error... But that's one for the manufacturers, not the operators...

The AKL incident (or accident) was a repeat of a similar SQ incident about a year earlier, in which the crew climbed out at V2 - 8kts. Both were caused by the fleet's procedure of overwriting the FMC computed figures with data from the airport analysis tables WITHOUT the requirement to check any differences with the FMC figures. It was a classic case of history repeating itself. Maybe the EK report will compare with the earlier T/O incident at JNB.
The problem may be in the method used to determine T/O performance figures rather than measures used to check the accuracy of those figures.
Personally, after "re-learning" how to obtain the numbers the SQ way, I wrote a list of V2's and EPRs for every 10 tonnes weight on the back of my clipboard and would set the V2 according to the flight planned T/O weight on the MCP during pre-flight scan checks - it gave me an instant cross-check when the co-pilot produced the figures for T/O from the loadsheet.
Methods for determining thrust/speeds vary from airline to airline for the same a/c type, few airlines seem to train such extractions well.
I would generally agree about the presence of both augmented pilots in the cockpit before departure - one is a useful extra pair of eyes, two are usually a distraction ( too much superfluous chat!).

I agree getting the figures from the OPT (performance computer) into the FMS is almost foolproof now.
However I still see gross errors on the OPT from time to time. Most commonly ZFW put into the TOW field or the wrong rwy intersection selected (and there is a trap to using the "first 4" option).

MR8,

I've been waiting for this:

TOP MARKS MR8! You are 100% spot-on!!!!! :D Pity there's a few punters here who don't realise this, and if they actually took the time to understand high-capacity transport category aircraft performance a bit better then they'd realise there's a lot more to it than meets the eye!!!

Recommended reading for those who want to find out more about the machinery that they drive - BOEING JET PERFORMANCE TRANSPORT METHODS (D61420). Yeah, and guess what........it applies to the Bus too! I know!

Spend some time 'Googling' if you don't believe me.....you WILL find the actual graph that substantiates MR8s TOTALLY correct statement!

A380-800 driver............do you want to elaborate on your concept of:

Because there's a VERY big difference between REDUCED thrust and DERATED thrust. :=

As an aside, I had to stop flying in 2007 due to the big 'C'. The stuff that you guys keep posting, the sheer diversity of opinion, and the 'ruthless' pursuit of reason amongst many (most??) of you makes me really appreciate just what ENORMOUS talent is out there in our industry, and how glad I was to have been part of it while I could!

Thanks all! :)

trite answer
 

toga every takeoff and rotate at last 2000' - should cover all the screw ups??
oui?

MR 8,

It cannot be too hard for an aircraft to weigh itself.The Merchantman (Vanguard freight conversion) used to do just this. The system was called STAN and on taxi out it used to give a gross wt check and a CG check as well.

I suspect that the main resistance to the aircraft self-weighing system would come from Commercial Dept.

As has been mentioned by others earlier in this thread, given the unrealistic standard pax weights and the totally unrealistic pax carry-on baggage allowance currently used, I don't think they want to know how much the aircraft really weighs.

Anybody in the idea, that it would be voluntary for the augmenting crew to be present in the cockpit (unless resting) might want to doublecheck the FOM before making any further statements.

With a bit of "SA" (i.e. when to be where in relation to the Engineer etc.) it can be accomplished rather easily, as suggested by Muttley C.

My thoughts go with the crew, whatever the outcome of the investigation.

Cheers

OBOGS

Ah yes but...

performance anxiety is quite real among pilots! Sit there and watch the operating captain when you are augmenting (or checking for that matter). In most cases their behavior will be subtly different than when alone. I believe thepsychs would have a term - its kind of like "mirroring' behavior between individuals establishing communications.

You can deny it till you are blue in the face but it won't change human behaviour.

I question from SLF. On a ship there is no augmenting crew. There is always only one Captain on board. Would you mind to explain who is in charge of the aircraft for the whole trip? Sorry for the stupid question, but I would like to understand the hierarchy on board in case of augmenting crew.
Thanks

No Land 3 says:
I agree that the time or distance to a selected speed has to be calculated for each takeoff, and if the correct numbers are put into the calculation all will be well. The point I was trying to get across in my original post was that some redundancy, an extra slice in the stack of Swiss cheese, can provide protection against wrong or incorrectly entered data.

If all the numbers provided are realistic and are put into the system accurately, as happens almost always, then the check is just that, verification that things are as planned. However when something goes wrong, when the passengers are all Sumo wrestlers rather than teenage gymnasts, or there is more slush on the runway than expected, or that supposedly empty container has been stuffed with a few tons of some illicit substance, or ..., then a check on time or distance to speed can save the day.

I suggested use of V1 as the check speed, simply because it is something already calculated and monitored. There is no reason in principle why some lower speed could not be used. Whatever speed might be used, the way to choose it should be decided by the owners of the SOP, taking into account input from people with appropriate ergonomics expertise and the PNF workload during takeoff.

I suggested basing the check on time rather than distance since the equipment required is miminal. Roll distance is not so easily measured, but could require extra hardware or modification of the software of existing systems. A conceptually simple system would be to adopt automotive technology and count revolutions of the landing gear wheels.

To drift slightly further from the main topic, one post a few pages back suggested that measuring time or distance to speed could give a reasonably accurate estimate of the weight of cargo and passengers, and averaged over a large number of flights be used to update the average wight of passengers and their carry-on baggage. Could the same information already be extracted from correlation of data captured by the flight data recorder and the loadsheets?

Runway Length
 

Runway length is a factor in properly determining V1.

I have written several statements and cancelled/deleted them. I wait for the report , but if the guys in the 2 front seats used 100T too little in the comp then good luck in your future jobs but dont make it a career in aviation!!! I have sadness and sympothy but no remorse, everyones life is in a pilots hands when on their a/c, i would willingly have borded this flight knowing that it could have happened to any of us, they were the poor bastrds and thank god it wasn't me? Good luck to them and GOOD LUCK to the rest of us!!

1. Time-to-V1 could indeed be a useful parameter.
With today's modern digital acceleration meters and computer power it should be quite feasible to have a computer monitor the take off run in real time too. I'd guess that it could already when 1/2 the calculated time-to-V1 has elapsed predict what the actual time-to-V1 will be, and call for more thrust if required.
2. Weighing pads on the ramp have their problems. One of them is the effect of any surface wind. Wind causes the wings to create a lift force, which can vary depending on the wind direction and aircraft deck angle. This can cause significant errors in the measured weights. This is probably one of the reasons such systems have not been successful so far.

Normally, in my experience flying for two International airlines, one Captain is designated as being " In Command " and the other will be subordinate legally, but it doesn't stop the arguments between them of course, or the unspoken dominating personality of one over the other. As has been said before, Human Nature Rules, OK ?

That is why many prefer the augmenting crew to be off the flight deck when not actually required - just easier, sometimes.