V2

[ozziekiwi]

Hello Guys n Gals,

I have just written a book about my 40 years on and off in the airline industry.
the book is finished and I had it proof read by a retired airline official who told
me that some of the explanations are not correct.

These are the explanations in question that I sourced from Google
and I would appreciate any comments to put me on the right track
(excuse the pun)


V1, is the speed beyond which the takeoff should no longer be aborted.



ROTATE, is the speed that the nose wheel of the aircraft leaves the ground.


V2 is the speed at which there is sufficient airflow over the control surfaces to actually control the aircraft.



He told me that the definition of V2 in particular troubled him.(He is not
a pilot)



I'm not interested in any sarcastic comments but just the good oil, the ridgy
didge stuff would be highly appreciated.


The book will be printed in the new year and will go on Trade Me,
Facebook, selected bookshops in NZ and BNE as well as E-Bay.
It goes back from recent times to the 1950's, in NZ with NZ, UT,
NM and ZQ, as well as Brisbane with AN.


Anyway thank you everyone so much for your help


Ozziekiwi

[Berealgetreal]

https://www.legislation.gov.au/Details/F2005C00327

Speeds:
V1 means the take-off decision speed;
V1 (wet) means a reduced V1 established for use on a wet or contaminated runway;
V2 means the initial climb out speed which is not less than the take-off safety speed;
VR means the speed at which aeroplane rotation is initiated by the pilot during take-off;
VS means the minimum speed in a stall or the minimum steady flight speed.

[ozziekiwi]

Thanks very much B R G R. I appreciate the research that you did for me.
Happy a very Happy Christmas and a Great New Year

Cheers

Ozziekiwi

[compressor stall]

In English for the masses, I'd say

V1 is a speed before which if you have an engine failure or major failure you have to stop. If the problem happens after this, you have to keep going as there's usually not enough room to stop.

Vr is the predetermined speed that the pilot pulls pack on the stick or control column to lift the nose into the air

V2 is a speed the aircraft needs to fly faster than to climb out safely

[ozziekiwi]

Thanks for that Compressor Stall

[MACH082]

V2 is the takeoff safety speed. It's the minimum speed at which the aircraft can fly, remain in control and comply with obstacle clearance requirements under 20.7.1b.

I remember in the turbo prop world some checkies would mark you down for not reducing to V2 in the second segment. This is idiotic and entirely incorrect. If you have an engine failure at a speed faster than V2, you'd maintain that to a limit. If you were slower than V2 you'd accelerate to that speed.

[EJECT EJECT]

V2 is the takeoff safety speed. It's the minimum speed at which the aircraft can fly, remain in control and comply with obstacle clearance requirements under 20.7.1b.

I remember in the turbo prop world some checkies would mark you down for not reducing to V2 in the second segment. This is idiotic and entirely incorrect. If you have an engine failure at a speed faster than V2, you'd maintain that to a limit. If you were slower than V2 you'd accelerate to that speed.

Spot on.

http://www.airbus.com/fileadmin/media_gallery/files/safety_library_items/AirbusSafetyLib_-FLT_OPS-TOFF_DEP_SEQ07.pdf

[Centaurus]

Hello Guys n Gals,

Rather than using corny Americanisms of "Guys n Gals" why not try normal English language such as (for example) "Hello Readers":ok:

[LeadSled]

Folks,
Don't like your definitions of V1 much, mostly they reflect misinformation/misconception/misunderstanding that is all too common.

Boeing, derived from the certification standards of FAR 25 etc., and various FAA flight test guides in the last 30 or so years.

V1 --- the speed at which the takeoff must be continued, if the stopping has not already been commenced.

There is no decision at V1, it is go.
The decision to stop, and the initial actions to stop must be before V1.
Before you start ripping into me, I suggest you do your very basic homework, because too many company manuals fit the "misinformation/misconception/misunderstanding that is all too common."
So do the investigations of a number of not so successful rejected takeoffs.
Tootle pip!!
PS: Airbus words (not operator interpretation of) may seem a bit different, but the result is the same.

[aussie1234]

Leadslead is right. If you hear/ call V1 and haven't already started the reject actions, it's GO

[aussie1234]

Plus your v2 definition sounds more like the definition for Vmca and I think if memory serves me correctly V2 is usually 1.1 Vmca.

And your rotate definition is more rotation. When rotate is called we start the rotation proceedure but the nose wheel hasn't left the ground yet.

[megan]

LeadSled has it. Misconceptions of V1 abound. It is not a decision speed, it is the speed at which the first action to stop takes place - applying brakes, reducing thrust, deploying speed brakes. The decision to stop therefore takes place prior to V1, see (a)(2) below. Interestingly, even Civil Aviation Order 20.7.1B gets the V1 definition completely wrong, so no wonder confusion exists.
The official definitions

§25.107 Takeoff speeds.

(a) V1 must be established in relation to VEF as follows:

(1) VEF is the calibrated airspeed at which the critical engine is assumed to fail. VEF must be selected by the applicant, but may not be less than VMCG determined under §25.149(e).

(2) V1, in terms of calibrated airspeed, is selected by the applicant; however, V1 may not be less than VEF plus the speed gained with critical engine inoperative during the time interval between the instant at which the critical engine is failed, and the instant at which the pilot recognizes and reacts to the engine failure, as indicated by the pilot's initiation of the first action (e.g., applying brakes, reducing thrust, deploying speed brakes) to stop the airplane during accelerate-stop tests.

(b) V2MIN, in terms of calibrated airspeed, may not be less than—

(1) 1.13 VSR for—

(i) Two-engine and three-engine turbopropeller and reciprocating engine powered airplanes; and

(ii) Turbojet powered airplanes without provisions for obtaining a significant reduction in the one-engine-inoperative power-on stall speed;

(2) 1.08 VSR for—

(i) Turbopropeller and reciprocating engine powered airplanes with more than three engines; and

(ii) Turbojet powered airplanes with provisions for obtaining a significant reduction in the one-engine-inoperative power-on stall speed; and

(3) 1.10 times VMC established under §25.149.

(c) V2, in terms of calibrated airspeed, must be selected by the applicant to provide at least the gradient of climb required by §25.121(b) but may not be less than—

(1) V2MIN;

(2) VR plus the speed increment attained (in accordance with §25.111(c)(2)) before reaching a height of 35 feet above the takeoff surface; and

(3) A speed that provides the maneuvering capability specified in §25.143(h).

(d) VMU is the calibrated airspeed at and above which the airplane can safely lift off the ground, and con- tinue the takeoff. VMU speeds must be selected by the applicant throughout the range of thrust-to-weight ratios to be certificated. These speeds may be established from free air data if these data are verified by ground takeoff tests.

(e) VR, in terms of calibrated airspeed, must be selected in accordance with the conditions of paragraphs (e)(1) through (4) of this section:

(1) VR may not be less than—

(i) V1;

(ii) 105 percent of VMC;

(iii) The speed (determined in accordance with §25.111(c)(2)) that allows reaching V2 before reaching a height of 35 feet above the takeoff surface; or

(iv) A speed that, if the airplane is rotated at its maximum practicable rate, will result in a VLOF of not less than —

(A) 110 percent of VMU in the all-engines-operating condition, and 105 percent of VMU determined at the thrust-to-weight ratio corresponding to the one-engine-inoperative condition; or

(B) If the VMU attitude is limited by the geometry of the airplane (i.e., tail contact with the runway), 108 percent of VMU in the all-engines-operating condition, and 104 percent of VMU determined at the thrust-to-weight ratio corresponding to the one-engine-inoperative condition.

(2) For any given set of conditions (such as weight, configuration, and temperature), a single value of VR, obtained in accordance with this paragraph, must be used to show compliance with both the one-engine-inoperative and the all-engines-operating takeoff provisions.

(3) It must be shown that the one-engine-inoperative takeoff distance, using a rotation speed of 5 knots less than VR established in accordance with paragraphs (e)(1) and (2) of this section, does not exceed the corresponding one-engine-inoperative takeoff distance using the established VR. The takeoff distances must be determined in accordance with §25.113(a)(1).

(4) Reasonably expected variations in service from the established takeoff procedures for the operation of the airplane (such as over-rotation of the airplane and out-of-trim conditions) may not result in unsafe flight characteristics or in marked increases in the scheduled takeoff distances established in accordance with §25.113(a).

(f) VLOF is the calibrated airspeed at which the airplane first becomes airborne.

(g) VFTO, in terms of calibrated airspeed, must be selected by the applicant to provide at least the gradient of climb required by §25.121(c), but may not be less than—

(1) 1.18 VSR; and

(2) A speed that provides the maneuvering capability specified in §25.143(h).

(h) In determining the takeoff speeds V1, VR, and V2 for flight in icing conditions, the values of VMCG, VMC, and VMU determined for non-icing conditions may be used.

[Traffic_Is_Er_Was]

The decision to stop, and the initial actions to stop must be before V1.

I would contend that the decision to stop must be before V1, but the actions can be at V1, as that by the definition quoted is what defines V1.

[PPRuNeUser0184]

From my operators performance manual:

V1:
"The maximum speed in the takeoff at which the pilot must take the first action (i.e. apply brakes, reduce thrust, deploy speedbrakes, etc) to stop the aeroplane within the accelerate-stop distance. V1 also means the minimum speed in the takeoff, following a failure of the critical engine at VEF, at which the pilot can continue the takeoff and achieve the required height above the takeoff surface within the takeoff distance"

V2:
"Takeoff safety speed. The target speed to be attained at the screen height, assuming an engine failure during the takeoff. This speed must be at least 1.13 times VS in the takeoff configuration"

[LeadSled]

Traffic etc.,
That may well be your contention, but as I said, lots of misconception around.
I wouldn't be quoting your "contention" at an accident investigation, if I were you.
KZ Kiwi,
Same answer, despite years since the problem became known, and major training campaigns to get the message across were commenced, there is still plenty of what you quote in evidence.
I even had a CASA FOI tell me, quite recently, that because CASA has (demanded) approved (which CASA legally doesn't, they "accept") similar wording in a manual, therefor it was legal.
My question about whether CASA had a Legislative Instrument "legally" amending the laws of basic physics (as it applies to the dynamics of takeoff certification) of it, unsurprisingly, went straight through to the keeper.
Tootle pip!!

[Traffic_Is_Er_Was]

Leadie, so who is correct? Boeing, or the FAA? You contend they are different. My contention agrees with the FAA def as supplied by Megan.

[pilotchute]

This explains the V1 pretty well.

http://https://youtu.be/KlpJTGAv2Oc (https://youtu.be/KlpJTGAv2Oc)

[megan]

The youtube clip

KlpJTGAv2Oc

[Andy_RR]

I thought V2 went ballistic and ended with a bang...

[Lead Balloon]

I think everyone in this thread, and the FAA and Boeing, are actually in heated agreement on what V1 should mean operationally: A decision to stop must have been initiated (past tense) at or before V1, otherwise you must continue. So if the toes hit the brakes at the same time as reaching V1, you can continue to stop even though you've reached V1 (and, on my reading of the FAA and Boeing words, even if you exceed V1 during the stopping action, provided the stopping action was initiated at or before V1).

The definition in CAO 20.7.1B seems the one that's out of step.

However, in fairness to the CAO and as I noted above, the FAA and Boeing words don't seem to rule out the possibility of exceeding V1 but continuing stopping, providing the stopping action was initiated at or before V1. So maybe there is the potential for (another) decision to be made at V1. What happens if your stopping action was initiated at or before V1, but fails? Your toes hit the brakes but they fail and have no effect. Wouldn't you have another decision to make? To 'un-make' your decision to stop?

[compressor stall]

I'm sure the OP's readers won't be able to put his book down with this level of detail.

[pilotchute]

Megan,

My link not good enough?

[megan]

pilotchute, for some reason when I tried your link it kept coming up with error messages, hence my post. Working like magic now though. Will delete it if you wish.

[pilotchute]

pilotchute, for some reason when I tried your link it kept coming up with error messages, hence my post. Working like magic now though. Will delete it if you wish.

No that's fine I was just a little curious.

[LeadSled]

Folks,
Lead Balloon puts it well, and there is no divide between Boeing (or Airbus) and the FAA certification rules.

There might be lots of detail in how a number is derived, but in the cockpit KISS is the golden rule, and for V1, it is the go speed, NOT the decision speed.

I have been "up front" for two critical EFATOs ( and a few less critical for stopping) one a go, one a stop, both involving instantaneous mechanical re-arrangement of an engine (always an outboard to maximize directional problems - as dictated by our old mate Murphie) KISS is the ONLY consideration.

Tootle pip!!

PS: If you listen carefully, the Boeing video has it right.

[Lead Balloon]

During the Sim ride in the video, the commentary says "you must initiate maximum braking by V1". Is that correct?

Is "initiating" maximum braking the same as actually achieving maximum braking?

What happens if you "initiate" maximum braking "by" V1 but you nonetheless exceed V1? Do you have another decision to make?

[megan]

V1 is defined as the pilot's initiation of the first action (e.g., applying brakes, reducing thrust, deploying speed brakes)Is "initiating" maximum braking the same as actually achieving maximum braking?You're playing with words. Initiating is not the same as achieving, and should be obvious - look up a dictionary if in doubt.What happens if you "initiate" maximum braking "by" V1 but you nonetheless exceed V1? Do you have another decision to make?No. Continue the reject. The aircraft accelerating past V1 with the thrust from the good engine/s prior to them achieving idle/reverse is taken into account. Note that reverse though is not on its own taken into account when the aircrafts reject ability is certified, it's just a "bonus" item.

[Lead Balloon]

I'm not playing with words. I'm focussing on what appears to be a possible source of confusion.

So you've confirmed that you have the same view as I have as to the distinction between "initiating" and "achieving". And you have the same view as I have as to the possibility of exceeding V1 during a 'normal' take off rejection action.

Let us assume that you "initate" maximum braking at or before V1, but you detect that you are "achieving" no braking and you exceed V1. Do you really "continue to reject"?

[LeadSled]

Megan,
Please go and look up the proper certification definitions, please, not popular shibboleths. It is really quite important in the understanding of what V1 actually is, as opposed to popular misconceptions.
Please use authoritative documents, not common "text books", FCOMs etc.

Let us assume that you "initate" maximum braking at or before V1, but you detect that you are "achieving" no braking and you exceed V1. Do you really "continue to reject"?

That is when you are really on your own, but by that time the thrust levers will long since be at idle ( or should be) ----- there are a number of instance over the years of something like this, not necessarily an engine failure, sorry, but I don't have references, but the outcome was never a happy one.

Tootle pip!!.

[megan]

Please go and look up the proper certification definitionsI posted the proper certification definitions earlier on, may have passed you by, me posting the complete FAR 25.107 Takeoff speeds definitions not good enough for you?popular shibbolethsWhich of those did I quote? I was answering Lead Balloons question What happens if you "initiate" maximum braking "by" V1 but you nonetheless exceed V1? Do you have another decision to make? His post askingLet us assume that you "initate" maximum braking at or before V1, but you detect that you are "achieving" no braking and you exceed V1. Do you really "continue to reject"? came after my post. And your answer that in that case you're on your own is spot on.

Please read what is posted and the order in which the posts are posted. ;)

[Lead Balloon]

You are "on your own"? Really? That's the collective wisdom of the experts? Really?

That might explain all those crumpled, busted and wet airframes in the video.

On my reading of the FAR definition and its underlying rationale, and on my understanding of the laws of physics, the answer to my question seems obvious: If you decide to reject and "initate" maximum braking at or before V1, but you detect that you are "achieving" no braking and you exceed V1, you 'unmake' your decision to reject.

Otherwise, the outcome is a certain overrun and another crumpled, busted or wet airframe, is it not?

[AerocatS2A]

So you are proposing that braking is initiated but the brakes don't work?

I can't think of anyone who would brake without simultaneously retarding the thrust levers. Or are you suggesting that in a reject you would apply the brakes, analyse whether they are working or not, then retard the thrust levers, see if that worked, then pop the spoilers? At each point in time you make a new decision?

[Lead Balloon]

So you are proposing that braking is initiated but the brakes don't work?For the third time: Yes.

The assumptions of my question were that the reject decision was made at or before V1, braking was initiated but the brakes don't work at all and you're now over V1. If you like, add the assumption that the thrust levers were also retarded at or before V1.

But you're over V1.

Are you proposing that the only option is to look ahead and crash visually? Is that not the inevitable consequence of being over V1 and not taking off?

Absolutely no option to advance the thrust levers for the good engine/s?

[AerocatS2A]

Well if the stop things don't work then you're on you're own, do whatever you think is the safest option. You're now outside the certification parameters and there are no right or wrong answers.

[megan]

Absolutely no option to advance the thrust levers for the good engine/s?And how long do they take to spool back up, and how much runway do you eat up in the process?

You're between a rock and a hard place.

Has there ever been a reject where the brakes failed to work?

[Lead Balloon]

Gosh. Questions in response to questions. I'm not the expert. You are, aren't you?

I realise you don't want to say it, but you're implicitly saying that the only option is to continue rolling down the runway with the thrust levers retarded, and look ahead and crash visually. I'm merely testing that position.

Certified 'big jet' engines these days must go from not much thrust to 95% rated thrust in 5 seconds or less: FAR 33.73(d):(b) From the fixed minimum flight idle power lever position when provided, or if not provided, from not more than 15 percent of the rated takeoff power or thrust available to 95 percent rated takeoff power or thrust in not over 5 seconds. The 5-second power or thrust response must occur from a stabilized static condition using only the bleed air and accessories loads necessary to run the engine. This takeoff rating is specified by the applicant and need not include thrust augmentation.In the conditions assumed in my scenario, will the engines really have spooled down to idle in the period between you initiating braking and retarding the thrust levers, and realising the brakes aren't working?

You've initiated braking and retarded the throttles at or before V1. Let's say 2 seconds later you realise the brakes aren't working.

The good engine/s didn't spool down to idle in those 2 seconds.

Let's say another second to advance the the thrust levers.

Note the 3 second margin that's built into the V1 certification data.

Are you still going to leave the thrust levers retarded and just look ahead and crash visually?

[MACH082]

You guys need to get a room seriously.

If serious **** happens and you haven't heard V1 - stop. If your hands off the thrust levers - go!

If it's not a critical failure I'd rather get airborne and land with all the runway in front of me than reject at high speed with the end of the runway much closer than I'd like. Even if an engine dumped its guts.

[Lead Balloon]

In the scenario I provided you have heard V1. At or before the point at which you heard V1, you initiated braking and retarded the thrust levers.

2 seconds after you initiated braking and retarded the thrust levers you realise the brakes are not working. You are now over V1 and the engines are spooling down.

Do you:

(1) un-make your decision to reject, advance the thrust levers and attempt to take off, or

(2) look ahead and crash visually.

Those seem to me to be the only options. The availability of (1) would seem to me (as a non-expert) to depend mostly on how much the good engine/s would have spooled down in the seconds between retarding the thrust levers and the realisation that the brakes have failed (2 or 3 seconds), and how long it would take the good engine/s to deliver sufficient take off thrust after advancing the thrust levers a second later.

Somebody in PPRuNeland must have experience in how much a 'modern big jet' engine spools down in 3 seconds and how long it takes to return to full thrust if the thrust lever is advanced at second 4. (And by 'modern big jet' I don't mean a B707...).

[Tankengine]

How do you know the brakes are not working after your two seconds?

[MACH082]

Lead balloon,

In that scenario you're having a pretty bad day. You'd have full reverse available (in fact you've probably already deployed them when you said stop) on whatever engine(s) are turning and you'd then run through the recall items for loss of braking.

Once you've committed to stopping, you've committed.

[Tinstaafl]

If it's a balanced field length I'd suggest it's rather unlikely to get get airborne in the distance remaining if, two seconds after applying brakes - which would also be somewhere in the reverser deploy process, and speed brakes activated - you then try to reverse those actions. You would be crashing off the end of the runway at high speed

V1 stop is a maximum effort manoeuvre. Two seconds of no braking + the time recognise and use the emergency braking is likely to result in rolling off the end of the runway - but at a significantly lower speed than crashing trying to get airborne.

[LeadSled]

Lead Balloon,
My "you are on your own" was intended to mean ---- there is no one answer, 'tis up to you.
However, I would be doing my best to stop, including making certain that the apparent lack of stopping was not caused by failure of spoilers to auto deploy, failure to properly close thrust levers/throttles (you might be amazed what is on some flight recorders/what I have observed in the sim.) or "relying" on auto-brakes.

Megan,
If you read the definition as a anything other than the the GO speed, if the rejected takeoff has not already been commenced, you ain't reading it right.

As to what is built into the derivation of V1, there have been all sorts of changes over the years, far too many to go into here, all to try and make a real world rejected takeoff more likely to succeed, without unacceptable payload penalties, but that doe NOT, in any way, change what the pilot in command is going to do, has to do, on the day it happens for real.

I would suggest I have quite a good handle on this particular issue, including membership a some "interesting" working groups, going right back to SFAR 422B, which is probably before many of you ( and FAR 25) were born.

As I said in my first post, there are still too many FCOMs/text books/training manuals etc., that vary from misleading to just plain wrong.

Tootle pip!!

[megan]

If you read the definition as a anything other than the the GO speed, if the rejected takeoff has not already been commenced, you ain't reading it right.I don't think I've suggested otherwise, have I? I posted, "V1 may not be less than VEF plus the speed gained with critical engine inoperative during the time interval between the instant at which the critical engine is failed, and the instant at which the pilot recognizes and reacts to the engine failure, as indicated by the pilot's initiation of the first action (e.g., applying brakes, reducing thrust, deploying speed brakes) to stop the airplane during accelerate-stop tests." Ergo, if you reach V1 and have not already initiated a reject (brakes, power, speed brakes) yes it's GO.

Though I did work with a guy who did a successful reject after V1 (RAAF Herc) after a bird strike at Darwin. Distance to run markers on the runway undoubtedly aided his decision making in the circumstance, he had doubt as to the damage sustained and if it was flyable.

Perhaps he had the Electra N5533 accident in mind.

[LeadSled]

Megan,
There is no direct correlation between the approach of many military arms and civil certification of takeoff performance.

The existence of and use of runway distance markers on military airfields --- of no relevance to civil operations ---- is evidence of that.

A common military alternative (I can't speak to RAAF practice) to the civil V1 approach is to have a maximum takeoff rejection speed, which, at light weights on long runways, can be at least rotate speed, and theoretically beyond. This usually included "takeoff monitoring", which means checking acceleration on the roll by timing passing runway distance markers.

You continue to re-quote various items that go into certifying V1, but the point I want to make, yet again, is what must happen in the flight deck, the niceties of what go into the establishment of V1 are not important to the pilot in command handling a critical engine failure.

KISS is the only thing that is important --- and getting it right!!

Tootle pip!!

[megan]

There is no direct correlation between the approach of many military arms and civil certification of takeoff performance.The military approach.
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA319982

[smiling monkey]

Spot on.

http://www.airbus.com/fileadmin/media_gallery/files/safety_library_items/AirbusSafetyLib_-FLT_OPS-TOFF_DEP_SEQ07.pdf

That's specific for the bus, I'd take it. For the airplane I fly, if you were single engine above V2 +10, the crossbars would pitch up to bring you back down to V2 + 10. All other speed scenarios are the same as the bus.

[FGD135]

Ok, everybody, how about we get the thread back to where it started, and attempt to give the OP some suitable and sensible answers. The last few pages have contained overly dry and technical definitions which we can safely assume would not be suitable for his target audience.

The OP quite rightly assumed that, of all the places in the world, this was the one that should have given him exactly the answers he needed, in exactly the wording appropriate for the audience. We can do far better. I believe the following is more along the lines of what he was looking for:

V1:That speed attained during the takeoff roll, after which, an aborted takeoff will likely result in the aircraft coming to a stop at a point beyond the end of the runway. The pilots use this speed to dictate whether, in the event of a significant failure during the takeoff acceleration, they should abort or continue the takeoff. V1 is the first of three milestone speeds that the aircraft must achieve during every takeoff. The others, in order, are Vr and V2.

Vr:The "rotate" speed. On reaching this speed during the takeoff acceleration the pilot initiates the pitch up that causes the aircraft to leave the ground. This pitching action is known as "rotation".

V2:That speed attained during takeoff at which the aircraft has a comfortable margin above speeds such as the stalling speed, where the controllability of the aircraft is not assured. V2 is the last of the three milestone speeds that an aircraft achieves during the takeoff and occurs a few seconds after becoming airborne. The others are V1 and Vr.

[+TSRA]

ozziekiwi,

Here are the explanations I obtained direct from Beechcraft and Bombardier when developing ground schools for the 1900D and DH8 (Classic and Q400). Couple years old now, but like weather, I don't think aircraft performance changes much:

Vcef is the highest speed at which the aircraft can be accelerated, experience a loss of the critical engine, and continue or stop in the computed minimum field length. Vcef must be demonstrated to be at or above Vmcg.

Because most pilots are not test pilots, most regulators require that 1 second of acceleration be added to Vcef. Vcef + 1 second = V1.

V1, therefore, is both the maximum speed at which the pilot must take the first action to stop the aircraft within the accelerate-stop distance (ASDR) and is also the minimum speed, following a failure of the critical engine at Vcef, at which the pilot may continue the take-off to achieve a height of 35' AGL by the end of the Take-Off Distance Required (TODR).

Vr is the speed at which rotation begins. Although some books define it as when the nose wheel leaves the ground, it is not. It is the speed at which rotation may begin. Performance data for first segment climb begins not at Vr but at a speed known as Vlof - Lift Off Speed.

Vr must be demonstrated during flight testing be be not less than 5% above Vmca, to result in at least the minimum Vlof demonstrated during flight testing, and must permit acceleration to V2 prior to reaching 35' above the runway. Furthermore, manufacturers must demonstrate that Vr will not result in an increase in TODR if rotation is begun 5 knots lower than published Vr during one-engine acceleration or 10 knots lower than established Vr during all-engine acceleration.

Vlof, on the other hand, must be at least 5% above the one-engine inoperative minimum unstick speed (Vmu-oei) and 10% above the all-engine operative minimum unstick speed (Vmu-aeo). The minimum unstick speed is literally the minimum speed at which the aircraft will first become airborne - those cool pics of tails being dragged down a runway and the aircraft becoming airborne at stupid low speeds.

V2, while defined as the "take-off safety speed" is actually a factor of the stall speed, specifically it is:
- 1.2 x Vs for two and three engine aircraft.
- 1.15 x Vs for four engine aircraft.

So while V2 is does ensure the aircraft can be controlled, it is more closely linked to achieving a speed as close to the maximum lift/drag coefficient to enable maximum first segment climb performance, thus ensuring close-in obstacle clearance.

Let me explain why V2 is not specifically linked to aircraft control - All "V" speeds must be demonstrated to be at or above Vmcg/Vmca (where applicable). Where they are shown to be below Vmcg or Vmca, the applicable speed is arbitrarily raised to the next highest speed (normally). So while all V-speeds do ensure the aircraft can be controlled, only Vmcg/Vmca specifically deal with it. All the others deal with other performance factors.

Hope this helps to generate some technical discussion!

[compressor stall]

Fdg135. Not quibbling with your words but your average Jo(e) will probably skip reading a definition paragraph that long. Technical accuracy is not the agenda here. I'm guessing that if the non pilot reader remembers that v1 is a stop / go speed, vr is a pull the nose up speed and V2 is an after takeoff speed then the author's job is done.

[LeadSled]

Compressor stall,
Put another way, you are saying we should perpetuate misinformation for the sake of ????

Technical accuracy is not the agenda here.

Why not? It is just as easy to get it right (technically accurate) as to get it wrong. Or are you dedicated to that new phenomena, "truthiness", which is something that sound like it could right (like a CFMEU robophone campaign) but isn't.

+TRSA,
Once again, homegrown interpretations, and the "1 second" you mention is both wrong and nothing to do with "test pilots" ---- when the "technically accurate" definition is simple and straightforward ----- but doesn't fit the per-conceived prejudices/ learned errors that ------ as is so clear in this thread, abound, despite years of trying to get the correct definition across.

Tootle pip!!

[Band a Lot]

I am with compressor stall, a person in the industry will have a good idea of the definitions (as we can see they vary!) the general public with some interest need only a basic definition - direct them to any FAA, Boeing or other definition web page but keep it simple.

V1 - the maximum speed during a take-off event that a take-off should be aborted, in the event of a malfunction or unforseen event. To continue a take-off after this speed would bring the aircraft to a stop beyond the end of the runway.

Vr - is the speed pitch input is given to become airborne.

V2 - the minimum target speed for controlled flight during a take-off event.

** Who at a speed 5 knots above V1 and then hitting a flock of birds that completely and instantly removes all vision on all windows except co-pilot side window will continue on to Vr and V2 speeds if there is 5 km clearing after runway finishes?

Me, I will apply brakes even after rotation(Vr) if 5km of flat cleared dirt lays in front of me.

[compressor stall]

Leadsled. Good science and technical communicators know how to tailor information to their audience, otherwise the audience will zone out through lack of interest or technical ability to comprehend.

Having a thorough technical understanding and grasp of the minutiae is fantastic, but one doesn't need to tell anyone that to get simple points across. In fact repeatedly doing so sometimes leads some to wonder the psychological motivations for such repeated pontification.
Notice professors who have weekly radio slots are good communicators as they can generalise highly technical concepts in bite sized chunks. They are not out to spread misinformation, they are selling a concept with deliberate simplifications. If I am explaining gravity to my younger kids, technical accuracy is NOT my agenda. The agenda it is their understanding and being able to understand it again the next day. So I talk Newtonian, not general relativity. Is this truthiness (whatever the #%^€ that is) or perpetuating misinformation?

[+TSRA]

LeadSled,

What else I agree there are more simple definitions out here, let me reiterate that those are not my definitions but those direct from aircraft manufacturers.

Perhaps I should rephrase that the data is adjusted for "normal pilot reaction time" which is defined by these manufacturers/regulators to be "1 second." Other manufacturers may be different and these ones may even have changed their definition, both of which I alluded to at the beginning of my post.

Also, I fear that in reducing a definition to its lowest level for the sake of the lowest common denominator is assuming a reader doesn't want to know the intricacies and does them a disservice.

I am a firm believer that there are two types of aviation books - technical and stories, and never should the two mix or dilute one another.

[LeadSled]

a person in the industry will have a good idea of the definitions (as we can see they vary!)No "they" don't vary, what varies is the degree of misunderstanding, misinterpretation, and so forth.

I have lived through (quite literally) the whole development of performance standards certification from SFAR 422B on, and it is a pity that efforts over the years to eliminate flawed understandings has been obviously so unsuccessful.

Part of the history: In the '70s and early '80s, there were a series of rejected takeoff accidents, some with seriously fatal consequences to passengers, crew, and in several very sad cases, people on the ground.

Among other things, this resulted in a major study by the ATA, which also included a number of non-US airlines, of which Qantas was one.

The study was to find out what pilots really knew about aircraft performance, what they had learned, where and how they had learned, been examined etc.

A core finding was a fundamental misunderstanding of V1, its derivation, and what it means in the flight deck.

As we see here, in this thread, there is wide deviance from the actual definitions. Some of you have talked about manufacturer information, used to derive manual information. What you really mean is somebody employed by a manufacturer, with an imperfect knowledge of the subject, has passed along, in good faith, a flawed explanation, which has been "interpreted" by the airline person, and something has wound up on a manual, and treated as gospel by probably generations of crews. But it was wrong.

There were several good examples of that in Qantas manuals back in the 60s, it was only when a pilot who had professional qualifications and experience in aircraft certification, arrived on the scene, the errors were corrected.

Specifically, in one case, the "Qantas" explanation of "geometry limited" on takeoff was completely wrong. There were other, they all had one thing in common, the information was not derived from source, but were misconceptions built on misunderstandings by pilots whose executive positions did not qualify them as performance engineers.

In the early days of the B707-338C in Qantas, the instructions for trimming were quite wrong. That one I remember very very well.

And, up to and including the B767 program, sometimes even the performance engineers get it wrong.

At about the same time, in parallel, but not directly related, an AFAP tec. team was looking at the whole issue, including military approaches, because at the time there was much interest in performance monitoring and "wet runway" operations ---- is the aircraft really accelerating "by the book", but that is a whole other subject.

Back to V1, the disturbing outcomes of the flawed knowledge clearly illustrated why a mindset on the flightdeck contributed to disastrous rejected takeoffs.

A major retraining program, originally designed by Delta, was taken up by all members of ATA, and most members of IATA, and was carried out through briefings and changes to simulator renewal or cyclic training programs, and I well remember the Qantas program, and the resistance of quite a few pilots (and not necessarily the older pilots) to having their fondly held misconceptions about V1 disturbed.

Bottom line: The certification definition is as I have said, the meaning on the flight deck is as I have said, and a proper first principles understanding of that part of certification allows no other definition.

Tootle pip!!

PS 1: A Boeing have always been happy to admit, their aeroplanes go better than they stop.
PS 2: Most pilots are most paranoid about runway length, and accelerate/stop distances, but the record show that a very significant number of rejected takeoffs result in loss of directional control, and leaving the side of the runway.
PS 3: There were some quite fundamental errors in the RR book "The Jet Engine", I don't know if they have been corrected in later editions. D.P Davies, in "Handling the Big Jets", even misinterprets his own ARB certification requirements, and largely ignores (except where he criticizes) the US certification of the B707. In my opinion (having flown both extensively) the ARB modifications to a B707 for a British C.of A were dangerous.

[Band a Lot]

Ok we need to disagree 3 pages with many examples most meaning the same in less words.

I call that varied, but the longest cut and past explanation is probably the most accurate description - but I can not be sure I only read about half of it. Surprisingly not finishing reading it didn't kill me.

If this OP is going to write his 40 odd years in the airliner industry in such detail, the pre-flight will take 20 pages.

What's the difference between a pre-flight and a Daily? In case the reader needs to know if its possible to do one and not the other or both need to be done we should define them.

[LeadSled]

What's the difference between a pre-flight and a Daily?Band a Lot,
I trust those who need to know, actually do! In a court/AAT, the difference is not trivial --- as people I know have found out to their great cost.

Indeed, the difference is a favorite of CASA counsel setting out to prove a defendant or witness is incompetent, and any other testimony should be considered in light of an incompetent answer to the above question.

As to the rest of the thread, I guess we will just have to accept that years of attempted education has failed, that fact just bounces off devout beliefs (obviously not limited to aviation) and there will undoubtedly continue to be avoidable accidents, as a result.

Tootle pip!!

[Band a Lot]

Getting back to "they do not vary" and I know wiki can be wrong. I don't think their statement is. "V1 is defined differently in different jurisdictions:"


V1 definitions[edit (https://en.wikipedia.org/w/index.php?title=V_speeds&action=edit&section=5)]

V1 is the critical engine failure recognition speed or takeoff decision speed. It is the speed above which the takeoff will continue even if an engine fails or another problem occurs, such as a blown tire.[9] (https://en.wikipedia.org/wiki/V_speeds#cite_note-Peppler-9) The speed will vary among aircraft types and varies according to factors such as aircraft weight, runway length, wing flap (https://en.wikipedia.org/wiki/Flap_(aircraft)) setting, engine thrust used and runway surface contamination, thus it must be determined by the pilot before takeoff. Aborting a takeoff after V1 is strongly discouraged because the aircraft will by definition not be able to stop before the end of the runway, thus suffering a "runway overrun".[33] (https://en.wikipedia.org/wiki/V_speeds#cite_note-33)


V1 is defined differently in different jurisdictions:

The US Federal Aviation Administration (https://en.wikipedia.org/wiki/Federal_Aviation_Administration) defines it as: "the maximum speed in the takeoff at which the pilot must take the first action (e.g., apply brakes, reduce thrust, deploy speed brakes) to stop the airplane within the accelerate-stop distance. V1 also means the minimum speed in the takeoff, following a failure of the critical engine at VEF, at which the pilot can continue the takeoff and achieve the required height above the takeoff surface within the takeoff distance."[7] (https://en.wikipedia.org/wiki/V_speeds#cite_note-faacfr-7)
Transport Canada (https://en.wikipedia.org/wiki/Transport_Canada) defines it as: "Critical engine failure recognition speed" and adds: "This definition is not restrictive. An operator may adopt any other definition outlined in the aircraft flight manual (AFM) of TC type-approved aircraft as long as such definition does not compromise operational safety of the aircraft."[8] (https://en.wikipedia.org/wiki/V_speeds#cite_note-TCAIM-8)


Given that a simple definition would be fine (with a disclaimer). And correctly a difference between pre flight and daily would do the reader no harm.

[LeadSled]

V1 is the critical engine failure recognition speed or takeoff decision speed.

Band a lot,
The above is quite simply wrong, a very dangerous "definition", as the accident record so clearly shows, and inconsistent with the further definitions you have posted.
You have even chosen to ignore the history I posted, as it does not correspond with your learned errors.
I am quite simply wasting my time with any further attempts to correct your misconceptions, I just hope you are not, and never likely to be, the Captain of a HICAP RPT aircraft, or any aircraft where a V1 is likely to be critical to the risk management of flight operations.
Tootle pip!!

[Band a Lot]

Oh Leady,


I think it was you that made the blunt statement along the lines, there is NO different interpretations and or definitions of these terms.

So I simply cut and pasted others in my last post (no me but from Wikipedia).

So you appear wrong - yes it appears FAA has a definition of V1, Transport Canada have a different definition, a Flight manual might have a different one and who ever wrote that other definition in Wikipedia has their definition (rightly or wrongly - they maybe from Canada with a older flight manual and thus it is correct).

Band a Lot " a person in the industry will have a good idea of the definitions (as we can see they vary!).

LeadSled "No "they" don't vary, what varies is the degree of misunderstanding, misinterpretation, and so forth."

Simple question asked simple.

Do FAA and Transport Canada have the same definition for V1?

or

Does the definition of V1 vary between FAA and Transport Canada?

[Band a Lot]

Ever heard sayings

More than one way to skin a cat,

When in Rome do as the Romans do?

* The first is very true if you ask a few cat skinners, most have their own way (I don't like cats so more dead the better)

* The second is often a legal requirement, $999.99 says you don't chew gum in Singapore!


So in a big plane with "too" pilots and too islels (wide body) in Canada, you as Captain will argue to the death of all - "your definition" is the only one and that is final- I am Captain and I am right. seems like a captain of a RJ in a recent - oh you play soccer?

""I just hope you are not, and never likely to be, the Captain of a HICAP RPT aircraft, or any aircraft where a V1 is likely to be critical to the risk management of flight operations.""

Mutual, but sadly I expect not. Mate check many words on many different things on many dictionaries or regulators sites.

Things vary, only a fool till death will not accept that and die killing all with a Lead balloon!!

Enjoy your NY.

[Band a Lot]

P.S I work in Aviation with tools, I often find a good aviation Tool.

TOOL tal PIP.

[Traffic_Is_Er_Was]

Bottom line: The certification definition is as I have said, the meaning on the flight deck is as I have said, and a proper first principles understanding of that part of certification allows no other definition.
But you have given us no definitions. You have just pooh-poohed everyone else's, and made the assertion that only your interpretation is correct.

[Lead Balloon]

I think he did provide a definition, at post #9:V1 --- the speed at which the takeoff must be continued, if the stopping has not already been commenced.

[Traffic_Is_Er_Was]

Which he indicates is a definition arrived at by Boeing (a manufacturer who has derived it from the FAR's etc - even though he has discounted any other manufacturers interpretations of the derivation).
There is no decision at V1, it is go.
This is correct. From the FAR, the decision to stop must be made BEFORE V1, thus V1 is NOT a decision speed, so the first part of below is correct, however his interpretation that:
The decision to stop, and the initial actions to stop must be before V1.
The second part of this is incorrect, as the FAR clearly states states that V1 is the speed achieved AT WHICH the brakes are applied, not the speed reached immediately after.
If Leadies main issue is with V1 being referred to as a "decision" speed, then he is correct, there is no decision at V1, you are committed. However, V1 has to be defined somehow, and I think the FAR is quite explicit, and even the quoted Boeing one is a little vague. If Boeing certificate to the FARs why not just use the FAR one? Surely that is the correct one?

[Lead Balloon]

I agree that the second bit is incorrect, if assessed against the FAR. It seems to me that the FAR definition anticipates initation action before or at V1. It seems to me that the Boeing definition quoted by Leaddie anticipates that as well. Perhaps Leaddie is misinterpreting the Boeing definition?

That said, I also agree that the Boeing definition is vague. What does "stopping has ... been commenced" mean? Does it mean deceleration has commenced? I don't think that is what the FAR definition anticipates. There's a difference between initiating action to stop and that action starting to take effect.

That's why it seems that you don't 'unmake' a decision to reject, even if you exceed V1 after initiating stopping action before or at V1.

[john_tullamarine]

Some thoughts (from a pilot with a reasonably extensive professional design engineering and certification background) –

There are two sets of rules in play -

(a) Certification (eg FAR 25, ANO 101.5/101.6 and antecedents, now all long gone to the rules graveyard somewhere ..)

(b) Operations (eg FAR 121, CAO 20.7.1B)

plus ayres and minor variations in other codes.

It would be nice if both sets of rules in each of the various jurisdictions were neatly aligned but that is not always the case .. engineers and pilots don’t always think the same way and confusion sometimes is the result. CASA has some certification experienced engineering/pilot folk in the operations regulatory arena so, perhaps, we might see things progressively improve.

We have the historical baggage associated with older local requirements (now defunct – the old 101 series of Orders, especially those with many dot subordinate identifiers in the callout). All but the very much older folk (probably Leaddie, due to the performance engineering folk with whom he came in contact in his early airline years and, perhaps, Stallie) in the PPRuNe sandpit will have no knowledge/recollection of these at all. These long preceded 101.5/101.6, themselves also gone to the archives and, I daresay, most here will not have any recall of their content either.

For many years, especially in respect of 101.5/101.6, these local requirements modified either the US or UK rules in various ways and caused the Industry all sorts of nuisances (until Ron Yates' Report pushed the rule makers to change things somewhat and those local rules were binned). Then, to confuse matters, 20.7.1B purported to talk operational implementation of the certification bases, occasionally introducing disjoints along the way. Add to that the penchant of pilots to produce 101 answers for most questions and the scene is set for OWTs.

It might be useful to keep the two sets of rules a little separate .. if you want to consider certification, then talk FAR 25 (or whichever set might apply in the circumstances). Ideally, the operational rules would look to flying the aeroplane in a manner compatible with the certification basis rather than confusing pilots’ minds in respect of (occasionally incorrect/incompatible) certification detail.

I see various posters quoting liberally from the FARs. Be VERY careful when you do this other than in a generic and, preferably, qualified way. The certification rules have varied GREATLY over the years, in keeping with technological capability BUT one generally doesn’t see retrospective application of new rules. That is to say, if you are looking at Aeroplane ABC, then you MUST check the TCDS to determine what version of the rules applied to its design and certification and then talk that version of the rules rather than the current set. In general, it is not valid to infer that a revised or new rule (not applicable to the particular frozen design standards defined for the original design) will apply, or be relevant to, that particular aeroplane. It follows that the rules applicable to one aeroplane may be quite different in detail to those applicable to another. This is quite relevant to a discussion on scheduled speeds where rules and interpretation has varied somewhat over the years.

Several posts query exceeding V1 with the reject commenced immediately prior to V1 .. once you start the reject, regardless of the speed, there necessarily will be a short period of (reducing) continued acceleration before things get sorted out (ie the brakes are actually doing their thing in earnest) and the speed starts to reduce very rapidly. In the case of the idealised sudden engine failure reject, engine rundown characteristics, timing and sequence of crew actions, etc., are very relevant to this observation. Once the levers are closed, boards up, and brakes on full song, deceleration will be very high in most cases (those who flew the 727 with the nosewheel brakes option will know what I mean) .. but it does take a finite time for this all to occur. The 2 second delay introduced at FAR 25 A/L 42 (and ANO 101.6 A/L 62 if I recall correctly ?) provided some much-needed, if small, fat for pilot comfort and rational reality

For a normal (dry runway) reject, reverse is held in reserve .. in any case, by the time significant reverse is achieved, the brakes have done the bulk of the deed and reverse has the main benefit of adding noise to all the other excitement. On the other hand, in the case of a slippery runway surface, reverse might become very important to the pilot’s wish list.

The current “how it is done” description lies within FAR AC 25-7 which can be found at https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC%2025-7C%20.pdf

Page 32 of this document indicates Section 25.107(a)(2) was revised to remove the reference to “takeoff decision speed” from the definition of V1. V1 is the speed by which the pilot has already made the decision to reject the takeoff and has initiated the first action to stop the airplane … this should be taken to be the likely current FAA thoughts on V1.

Keep in mind, when reading the FARs, that one always has to read the applicable ACs to get the behind-the-scenes FAA story on what they thought the rules should mean.

If things go significantly awry, for whatever oddball reason (eg, in keeping with some concerns expressed in this thread - no brakes) and the certification boundary condition expectations cannot be met in reasonable measure, the whole thing then is very much in the lap of the Gods. Leaddie’s post #29 is pertinent.

A similar oddball case is the low speed (Vmcg-limited) V1 critical fail reject in the presence of a significant adverse crosswind .. continuing, with the aircraft out of control directionally, is not a good option and a post-scheduled V1 reject might be the way to go (ie stop). Another example is the airborne Vmc case where the pilot fails to apply the necessary bank inputs … and over we go. A read of the Darwin Braz mishap is useful, and sobering, for this one.

However, whatever the situation, if you are well outside the postulated certification parameters, then the performance capabilities of the aircraft on a critical runway probably aren’t going to give you a nice outcome ... if the initial OEI reject decision is reversed on a critical runway, the runway head speed probably isn’t going be useful. Sometimes we just have to accept that the Gods are mischievous on occasion and we might not make it home. Certainly, the certification rules don’t give guarantees .. only probabilities.

Keep in mind that the basic certification idea is a single major failure to contend with. Sure, historical reality tells us that the real world doesn’t always mirror the certification idealisations as nicely as we might like to see, but the further we get away from the test conditions .. the further we get away from a potentially happy outcome. Refer Aerocats’ #34.

Note the 3 second margin that's built into the V1 certification data. Refresh my memory as to the story here ?

2 seconds after you initiated braking and retarded the thrust levers you realise the brakes are not working. You are now over V1 and the engines are spooling down. You will be WELL over V1. What to do ? All depends on a heap of things which defy analysis in an instant on the fly. Retracting the gear/ground looping might be an option if all else appears to be covered in blood. If you have another 10,000 ft or so ahead, you may be having a somewhat better day. In any case, I doubt that one would take anything like two seconds to recognise a significant brake failure ...

What does concern me is the apparent thinking that all this is black and white. That just ain’t the case. The certification standards presume certain conditions etc. and, to be sure, generally those presumptions work out reasonably well in practice as we don’t have aircraft falling about us day in day out.

However, one should not lose sight of the fact that the certification performance rule book presumes an idealised, prescribed world – it has to do that if there is to be any repeatability in testing - albeit with a bit of fat here and there to provide some protection for innocents abroad. Now, if the real world on the day varies significantly from that postulated .. don’t be surprised if you don’t see the aeroplane match the book. If the delta is significant and not your way, then don’t be surprised to see tears at the end of the day.

The present Industry thought about V1 (viz., in general the outcome is far more likely to be happy if the takeoff is continued from V1) endeavours to incorporate real world, historical, statistical reality while generating cockpit simplicity for SOP. IT DOES NOT GUARANTEE a happy outcome ALL the time .. but, certainly, most of the time things will end well.

If, on the day, the boundary conditions vary significantly from those presumed, and were not amenable to pretakeoff planning (I'm sure we all do think about the what-ifs and how we might handle them ?) the Commander gets to earn his/her pay in a very short time .. win (hero/heroine), lose (scapegoat), or draw (lives to fly another day, albeit with sweaty palms at the time).

The thread discussion, however, is invaluable, as it encourages thinking and provides an opportunity for newchum education.

It has been my observation that the majority of endorsement courses and recurrent training probably don’t give enough detail to the details and the limitations .. which is why some of us, with a foot in both camps, have approached pilot training from a quite different starting point. Those of you who are fortunate enough to have very experienced ops engineers (especially those with significant heavy aircraft operational experience) associated with your operation and training are, indeed, most fortunate. Do heed their technical counsel.

[Lead Balloon]

Note the 3 second margin that's built into the V1 certification data. Refresh my memory as to the story here ?It's mentioned in the video linked at post #17.

I may have misinterpreted what is said, but there's 3 seconds of something built into the number.

[john_tullamarine]

Didn't have time to look at the video first time through .. boy, but that's an old training video .. I can recall it being introduced, guessing now, around the early 80s ? As I recall, Boeing led an Industry study group on rejects and the video was one of the outcomes. Nonetheless, it's pretty good gen. Memory is a bit ragged on this .. if the video is the one referred to in the link at the bottom of this post, it will have been developed somewhat later. However, I seem to recall having seen it during recurrent training sessions in the 80s at AN - perhaps that might have been later in NZ - doesn't really matter.

Ref the three seconds .. all OK, the long-established one second time sequence to reconfigure expeditiously for the reject (which had been the basis for most certifications for many years prior to A/L 42 - watch guys in the sim and be startled at how many take somewhat longer to achieve the reconfiguration to throttles closed, boards up, and max braking .. and that's with them primed for action .. ) plus the A/L 42 two second pad at V1 to provide a bit of a pad for things such as crew startle response and so forth ie acknowledgement that one second really didn't cut the mustard. If my recollections are correct, the original 707 certification program introduced the one second timing ?

I would hesitate to call it a margin. At best it's a bit of fat to acknowledge that the typical reject crew is going to be hard pressed to get the thing stopping in under three seconds ...

Main thing for all to keep in mind, that time pad disappears VERY rapidly and a tardy PF can find him/herself eating up stopping distance with considerable ease before the reconfiguration is completed ...

Another useful reference is https://flightsafety.org/files/RERR/TakeoffTrainingSafetyAid.pdf

[Lead Balloon]

Is 'a bit of fat' an esoteric engineering unit of measurement, JT? Sounds to me like a colloquialism for 'margin'...

Whatever it is, it's built into the number.

Given that I'm 'on my own' because the scenario I brought up is outside the certification parameters, my decision to unmake the rejection decision on discovery that my brakes have failed will depend on the spool up time for the good engine/s that have been spooling down for only a few seconds, noting that I'm over V1...

[john_tullamarine]

High tech engineering term .. all part of the in-house jargon.

.. but, as you wish, good sir .. I think our thoughts are in formation.

As to no brakes .. rather you than me ... unless one were looking off the end at Edwards ...

[AerocatS2A]

It appears that Lead Sled is largely arguing that the stopping must have been commenced prior to V1.

The decision to stop, and the initial actions to stop must be before V1.

The main problem with this is that without further definition, "before V1" is meaningless.

How much before V1?

I assume that if I suffer an engine failure and take stopping action AT V1 (i.e., V1 - 0 seconds) then I'm not complying with Lead Sled's interpretation. However if I take action at V1 - 1 second then I am. Presumably I'm also complying if I take action at V1 - 0.0000000000000000001 seconds. The latter is of no practical difference to being "at V1" so the phrase "before V1" is meaningless and has no distinction from "at V1" without further definition, e.g., by V1 - 1 second.

[AerocatS2A]

Another thought: Although V1 is not a decision speed, from a practical point of view it should be a decision speed*. The monkeys up the front have just two things to do, make a decision and then action the decision. Assuming they have a healthy sense of self preservation, the actioning of the decision will be as soon as possible after the decision has been made. The monkeys don't necessarily know how long it will take between making the decision and actioning it though, and they therefore don't have the information required to know whether or not they will be taking action by V1. Far better for V1 to be the fastest speed a stop decision can be made, allowing for some standard reaction times. That way all the monkey needs to know is that if they are not at V1, they can decide to stop.

*I'm not saying the current V1 should be treated as a decision speed, I'm saying that V1 should be redefined and recalculated to be a decision speed.

[Band a Lot]

At V1 and above, decision/s still need tobe made to continue or "try" abort.

* a critical engine (uncontained) failure at V1 - One must ask oneself. Will Ireach the required height above the takeoff surface within the takeoff distance? Or has this failure given me a lot more drag than I got in the SIM last week? A727 the other day may well have been better aborting above V1 than soldier on.

* Just hit V1 and God Dam it a 747 just pulled onto the my runway, right before my expected rotate point. Excuse me old chap, I am now at V1 would you mind moving off my runway? -------------Do you copy?

*V1 - Dear thrust reverser please retract, I am committed to take off and am getting dizzzy.


I think John has said it well - read the book but it isn't a bible, too many variables. But at V1 and above the "better option" is often, but not always to continue with the take off. The option is always there to abort at any speed above V1, but it will have levels of pain/hurt attached in many cases.

So V1 is where the preferred decision changes - below the preference is to stop, above preference is to continue with take-off.


Either way pick the one that will cause least fatalities, better still none.

Aerocat, what is the error of the ASI? so even V1 has a tolerance of acceptance.


the scale errors at the major graduations of the scale must not exceed ± 4 knots up to the maximum speed of the aircraft.

[john_tullamarine]

Another thought or two, if I may ..

It appears that Lead Sled is largely arguing that the stopping must have been commenced prior to V1.

Recommended practice from both the current Design Standard (via AC interpretation) and the older Industry video are similar in that, if one hasn't commenced the first action (ie levers closing/closed or size 12s on the pedals - ideally simultaneously) then one is probably better off keeping on going ... Leaddie, as a younger chap, was drilled in this philosophy. Further, within the higher pre-V1 range, typically taken as above 80KIAS, one only rejects for major problems.

That doesn't mean one discounts thinking .. there are foreseeable situations where it is sensible to reject from higher speeds and take a lesser hurt than going. Far too many variables to be other than vague.

The main problem with this is that without further definition, "before V1" is meaningless.

The situation doesn't lend itself to precise definition. The recommended practice is as above .. if you haven't already commenced the stopping sequence by V1, then it is generally better to keep going.

from a practical point of view it should be a decision speed

Which is what it was under previous versions of the Standards. We really are getting into splitting hairs. The main concern is to have a routine procedure which will cover most events .. with the Commander paid appropriately to call a different shot should unusual circumstances dictate.

The history of overruns led to adoption of the present philosophy. That you, or others, may disagree, is fine.

At V1 and above, decision/s still need to be made to continue or "try" abort.

Of course, the occasional situation may call for such a non-SOP decision. The problem is that the line pilot generally has little, if any, basis for making the decision on rational, technical grounds.

a critical engine (uncontained) failure at V1

Commander's call. Generally can only be on the basis of a gut feel.

a 747 just pulled onto the my runway

Little likelihood of stopping in most situations. Between a rock and a hard place, I suggest.

Dear thrust reverser please retract

For most installations, pulling the buckets is commitment to stopping for just the concern you express.

but it will have levels of pain/hurt attached in many cases

Which is why most of us would like information on the ASD-limiting speed, regardless of other considerations .. so that a pre-takeoff consideration of what the level of hurt might be .. might be made.

what is the error of the ASI

Too much precision just gives the crew a headache. Reasonable accuracy and best efforts probably is a more useful goal.

[Band a Lot]

My reverser comment was the recent one side self engaged - if that happened at V1 we aint going!

We have an allowable 4 knots on the gauge but zero on V1, not even a conditions variant.

Now what would the call be on this famous crash be if they had Tail Cam? it happened in the "fat Zone".


At 14 h 42 min 31 s, the PF commenced takeoff. At 14 h 42 min 54.6 s, the PNF called.


one hundred knots, then V1 nine seconds later.


A few seconds after that, tyre No 2 (right front) on the left main landing gear was
destroyed after having run over a piece of metal lost by an aircraft that had taken off five
minutes before. The destruction of the tyre in all probability resulted in large pieces of
rubber being thrown against the underside of the left wing and the rupture of a part of
tank 5. A severe fire broke out under the left wing and around the same time engines 1
and 2 suffered a loss of thrust, severe for engine 2, slight for engine 1.

[Lead Balloon]

The history of overruns led to adoption of the present philosophy.This is why I find the responses to my scenario so interesting.

My 'take' on the introduction to the video, and your comment above, JT, is that the main safety issue was take offs that should have been continued rather than rejected, not vice versa. Yet when I give a scenario in which stopping action is initiated prior to or at V1, but the action fails, and the aircraft is now over V1, no one can bring themselves to say: Maybe the safer option is balls to the wall on the good engine/s and continue.

Let me change my scenario. Trundling down the runway the critical engine fails at V1. It is therefore not possible to intiate stopping action before or at V1. On my understanding of the collective expert wisdom, the decision must be to continue the take off - that decision having been made prior to or coincident with the critical engine failure at V1.

The only difference between the above and my original scenario is that the thrust levers were retarded at or before V1 in my original scenario.

Can I suggest that during the three seconds from the point at which the thrust levers were retarded until the thrust levers were advanced (amateur pilot Lead Balloon having realised the brakes were not working):

(1) the aircraft has exceeded V1

(2) the aircraft hasn't decelerated much, and is nearly as far down the runway as it would have been if the thrust levers for the good engine/s had not been retarded, and

(3) the good engine/s would not have spooled down that much and will spool back up to take off thrust 'quite quickly'.

However, I concede that number (3) is the critical variable. And this is where one of the points you (JT) made earlier becomes very important: Against which standard is the aircraft (and its engines) certified?

I can understand why spool up times would weigh heavily on the minds of the crews of e.g a B707. But 'modern big jet engines' are a little more responsive than P&W JT-3Ds - I posted the current FAR standard earlier.

For example, my understanding is that a version of the B777 will roll at 30kts with both engines at idle, unless the crew rides the brakes to keep the taxi speed down. My understanding is also that a B777 will take off and fly on one engine with the OAT 50c. Lessons learnt on B707s and early B747s may not be directly transferable to aircraft fitted with engines certified to the contemporary standard.

(And can I note how impressed I am with BaL's google skills? :ok:)

[Stationair8]

What was the first aircraft in Australia to have V1 & V2 speeds, the DC-4, Electra?

Didn't DCA want the TAA Twin Otters to have calculated V1 and V2 speeds, or they wouldn't let them go on the register?

[LeadSled]

What was the first aircraft in Australia to have V1 & V2 speeds, the DC-4, Electra?

Folks,
Anybody remember the Caribou Ansett bought for PNG --- DCA insisted on applying "modern" takeoff performance criteria, which made the airplane useless for the intended purpose in the highlands, but the DC-3/C-47 soldiered on for years after the Caribou was sold, as DCA only applied the old Developmental Air Services rules to the Dak.

Typical of bureaucratic application of arbitrary criteria. The problem with commons sense is that it is so uncommon.

John T,
Many thanks for your contribution, so many of the posters not only have no idea of the developments of the standards since the original SFAR 422B, but are totally resistant to any modification of their chosen misinterpretation, and I just shake my head at the cut and paste brigade --- they found "it" printed somewhere, so "it", or more accurately, their interpretation of "it" must be correct.

Never let the facts stand in the way.

All,
The point I have been trying to make, all along, is that, despite changes over the years, including the details of how an actual number is derived, the cockpit meaning of V1 should be very clear, and KISS must prevail.

V1 is NOT a decision speed.

Tootle pip!!

PS: "small" changes are not trivial, the Australian unique rules John T mentioned, that were swept away in mid-1998, by the only so far successful regulatory reform of CASA rules (CASR Parts 21-35) saved Qantas a fortune --- because payloads at limiting range out of mid-length runways increased by 50% or more for the B767. In particular, we were no longer required to comply with the Australian unique requirement, in calculating performance, to allow for a 2 second ALL ENGINE acceleration beyond V1, then transition stopping and finally full stopping.
Unsurprisingly, this Australian unique requirement , had it been applied universally since the dawn of the jet age, would not have changed the outcome of even one single flight, but Hey!!, you can't be "too safe", can you??

[Band a Lot]

"Let me change my scenario. Trundling down the runway the critical engine fails at V1. It is therefore not possible to intiate stopping action before or at V1. On my understanding of the collective expert wisdom, the decision must be to continue the take off"


I agree with that 100%. But if any other event has/is happening because of or independent flow the engine failure - the definition of V1 is out the window and you are on your own, untested territory.

V1 is a certification process with a perfectly serviceable aircraft with 1 failed engine and no other defect.

The affixation of MUST take-off at V1 or above with an engine failure, an engine surge, blown tyre and airframe damage is not justified under the definition/s of V1.

The concord captain had this affixation (V1 must go) but was fully aware they had more wrong than just one engine failure. None of us were there to see what the crew had to deal with during that take-off roll, but if he was not adamant he must take-off he may have elected to abort. If he did abort, all on board may well have still died in a probable fiery crash some distance from the end of the runway.

There is a chance some may have survived, notably the four in the hotel far from the runway.

[john_tullamarine]

We have an allowable 4 knots on the gauge but zero on V1, not even a conditions variant.

I have it in mind that the Standard for I/F ASI is 5 knots but won't bother to dig that out to confirm/correct just now .. certainly, there is (and must be) a tolerance.

The usual calibration will result in a lesser error .. normally, the operational application is to apply the design tolerance as a "between gauges" figure. Like many things, we can split hairs all day .. in current practice, V1 should be called marginally early so that the call is completed by the observed V1 reading. A small error will be accommodated by certification tolerances and I certainly wouldn't be losing too much sleep over this particular concern.

Now what would the call be on this famous crash be if they had Tail Cam? it happened in the "fat Zone".

As most would be aware, there were various tales about this and that with the mishap aircraft.

However, the takeoff mishap, very clearly, was way outside the certification expectations and parameters. Evidently the Commander flew the failures exceptionally well but far too many things were against him and the outcome was predictable and is well known.

Some days it doesn't pay to get out of bed .. problem is, we don't have a crystal ball to identify the days in question.

Again, the Design Standards DON'T give you any guarantees .. only reasonable probabilities based largely on historical data. Unless the situation is well and truly outside the gameplan, there is a good chance of a successful outcome, given a competent (and, where necessary, innovative) crew.

For the small percentage of folks who find themselves up that well known creek without a paddle .. life's risks sometimes catch up with us and exact a dreadful toll.

Yet when I give a scenario in which stopping action is initiated prior to or at V1, but the action fails,

I, for one, have no problem with your scenario.

However, it is well outside conventional certification expectations. Unless there be significant spare runway (hence my Edwards reference) the likely outcome is not going to be nice regardless of however the Commander might play the cards on the day. As to what is the best call .. as so often, it depends. Nothing wrong with having the discussion, though.

the decision must be to continue the take off

That will be the normal SOP. However, as a wise checkie once emphasised to me at the debrief ... "Young John, keep in mind that the manual has an admonition on the front page in invisible ink .. 'To be read with a modicum of commonsense'".

We necessarily need to keep the routine balanced against the extraordinary. SOP intentions probably will provide an acceptable outcome on the great bulk of occasions .. so we stick routinely with SOP. On those occasions when the Commander is called upon to earn his/her salary, SOPs just may not cut the mustard and the Commander may have to be a bit innovative.

Lessons learnt on B707s and early B747s may not be directly transferable to aircraft fitted with engines certified to the contemporary standard.

That may be a fair comment. However, the underlying problem is that the sorts of scenario you postulate generally have not been tested and, hence, the crew on the day probably doesn't have much to go on other than gut feel. So long as that is understood, then the folks in the sharp end just make the best play they can out of a bad hand.

What was the first aircraft in Australia to have V1 & V2 speeds, the DC-4, Electra?

Both predate my Industry involvement slightly (although I did fly and loved the Goose in the late 70s). We would need someone a bit older who was involved in the early to mid 50s (good heavens, I still had to discover girls at that stage of my life ..) to recall the precise sequence.

Prior to the PAMC changes to performance - which were around this time (as I recall the F27 was probably the first to run the recertification gauntlet) aircraft performance was scheduled to older standards.

My guess is that the DC4 wouldn't have been reworked - although I did some engineering work on the Air Express ex-QF DC4s at Essendon, I just can't recall what the cockpit procedures were. However, the turboprops certainly were redone. So the Electra and F27 (flew both) had the normal schedules. I just gave Centaurus a call (he flew Viscounts for 34SQN) and he confirms they had the normal schedules. As to which may have been the first in country, that would require some homework in the archives. Likewise for the Twin Otter question.

we were no longer required to comply with the Australian unique requirement

Actually, that wasn't a local requirement. The Australian change reflected the FAR25 design change as discussed in earlier posts.

V1 is a certification process with a perfectly serviceable aircraft with 1 failed engine and no other defect.

Not exactly the case and has varied through the years but close enough for the purposes of this discussion.

The affixation of MUST take-off at V1 or above ..

Not exactly the Industry viewpoint .. suggest a review of the video cited earlier which is still reasonably valid vice the rulebook.

but if he was not adamant he must take-off he may have elected to abort.

At the time, the crew could not have known the full story - although they certainly would have known that they had a nasty situation on their hands. I suggest that it is most unlikely that a disciplined crew would reject for the situation faced. In hindsight, knowing the details which came to light during the investigation ... perhaps ... but that's information not available to those in the front seat at the time.

Again, I can only urge folks not to read things as being hard and fast black and white. It is all based on reasonable probabilities and what might be a reasonably reliable (not necessarily the best) way to achieve an acceptable outcome on the day when only part of the story's details are to hand.

[Band a Lot]

Sorry John I meant elected V1.

As per Concord they elected middle ground @ 150kts, but this then has no tolerance by crew.

A failure like QF32 either side but close to V1, would be a case of not having a good day.

[Slippery_Pete]

Good discussion, and I really value the ops engineering insights from JT.

My humble opinion on this: while I find the technical descriptions and changes in the orders over time very interesting, most of the very pedantic consideration is academic and not useful practically.

I wouldn't expect to find any pilots in Australia flying transport category who don't understand the concept that you must have started doing something to stop by V1.

The discussion about V1-1 or V1-0.000001, and deciding to go after commencing a stop - all a bit of a waste of time. The stress which occurs with a V1 stop/go will, for 99% of pilots, not afford the required headspace to do something like change the mind. In the sim when you're expecting - maybe yes.

If the runway speeds are brake energy limited, it might be better to commence a stop above v1 and risk a brake fire. If runway length was limiting, it would probably be best to go. All interesting to discuss, but who is going to have that sort of headspace available to decide when it all turns to ****?

As someone said earlier, KISS.

The only reason I'd actually commence a stop after v1 would* be if the aircraft is definitely not going to fly - like a structural or controllability failure.

[Band a Lot]

"The only reason I'd actually commence a stop after v1 wouldn't be if the aircraft is definitely not going to fly."


No that makes sense to me, no point accelerating to a certain crash. But very hard to know in that short time. Increasing vibration on any control surface would do it for me.

[megan]

Critique the decisions made here. L-1011 abort following lift off when the stall warning/stick shaker activated.

http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR93-04.pdf

Re Concorde had it attempted an abort from the report Consequences of Aborting the Takeoff

Two simulations of a possible acceleration-stop were performed, one based on the aircraft’s speed when the rotation was commenced (that is to say in fact the first moment when the crew could have been warned by unusual sensations), at 183 kt, the other at 196 kt, when the FE said what can be understood as “stop”.

The simulations were conducted with the following hypotheses:
• braking on seven wheels, to take into account the destruction of tyre No 2,
• braking torque available at nominal value until the maximum energy indicated in the Flight Manual (70 MJ), increased by 10%,
• use of thrust reversers on engines 1, 3 and 4. With this set of hypotheses, it appears that the residual speed of the aircraft at the end of the runway would have been 74 kt for a takeoff aborted at 183 kt and 115 kt for a takeoff aborted at 196 kt. These figures show that an aborted takeoff would have led to a runway excursion at such a speed that, taking into account the fire, the result would probably have been catastrophic for the aircraft and its occupants. The relevant speeds for the take off were V1: 150 kt, VR: 198 kt, V2: 220 kt. They ran over the metal strip, which precipitated the event, at 175 kt, 25 kt past V1.

Was there not some discussion that an abort, and the trajectory the aircraft would have taken, would may have lead to a collision with a 747, and was the presumed reason he rotated some 11 kt early?

[Band a Lot]

Wow that's ballsy after take-off!!

It paid off in that case.

As with Concord the fact of heavily on fire certainly had a high probability on not ending well for all on board. Only with luck not more than 4 people were not killed (6 others injured with burns I assume) in the hotel it crashed.

I don't recall the 747, but the pilot at 150kt was committed to take regardless even though the upper speed of V1 from memory was 164 kt (11 kt over then if upper limit used).

[Judd]

Good discussion, and I really value the ops engineering insights from JT.

Agree wholeheartedly. Over many years I have read countless articles on the subject of V1 and its ramifications. What stuck firmly in my mind was the potential danger of over-run in any limiting length runway rejected take off nearing V1.
This observation came to the fore during the numerous simulator sessions I attended during my career where pilots invariably cocked up rejected take offs on marginal length runways especially wet surface. It could have been due to the surprise factor for example, or delays in extending speed brakes and even rejected a take off because of a gut feeling that something was not quite right. Even though nothing wrong with the aircraft.

I quietly came to the conclusion from the time I had my first command that 15 knots below V1 I would continue the take off. Screen height might be compromised but statistically I felt I would not hit a tree branch during climb-out. To this day I remain comfortable with that policy regardless of legal ramifications.

I kept my thoughts to myself about all this because to inform a co-pilot during the before take off safety brief would only invite pursed lips and eyes rolling in terror at such a heinous decision requiring a dobbing in to management. The CVR was kept in the dark for obvious reasons.

in short, my decision in this matter of V1 was based upon reading world wide accident reports of fatal high speed aborts which need not have occurred but for mis-judgement by the pilot. In other words learning from someone else's experience, which is no bad thing:ok:

[Band a Lot]

Judd I assume you are talking just an engine failure event "with no extras"?

Or regardless 15 kt below you will continue to blast of regardless of all else.

P.S. 15 Kt below on a craft on fire will be almost certain death in the Concord or other scenario (tail wind!).

[john_tullamarine]

Re a personal pad on V1 .. not at all uncommon. Indeed, in the analysis of the mishap in the earlier link (megan #84), the operator had a definite policy to shade the call below V1 ..

Another caveat to keep in mind. If the takeoff is at very low weight with a minimum speed schedule (ie looking at the Vmcg-limited V1 situation or even a bit higher with a strong crosswind (as it turns out on the day .. from the wrong side), choosing to use a lower than scheduled V1 just might see the aeroplane out of control for the critical OEI failure and very smartly off into the grass. In general, a real-world-Vmcg-on-the-day directional departure is sufficiently rapid to bring tears to the eyes ..

There are strategies available to minimise this sort of risk but, however you might choose to approach the problem, one should be aware of it at the very least and not needlessly expose the operation to the risk.

[Band a Lot]

Off track a bit (sorry) John did you play with the Nomad? and its certification?

I seem to recall your name in a thread about them??

I learned lots about how to operate that aircraft at a conference in NZ ( blue line was your friend) a very interesting seminar and regulator present.

[john_tullamarine]

Finished uni on a cadetship (with then Supply) for the Bend. Spent some time following as a design engineer/aerodynamicist on the Nomad program before heading off to DCA. Did some mod climb test work on the N24As up north some years after. Years later back again to head up field support after djpil headed off to the US for some fun and games.

Some enthusiastic operators in the NZ arena. Do you recall any factory names from the conference ?

Although I had various involvements with aspects of its certification over the years, a far better chap for Nomad certification questions is djpil who spent many years on the program, ending up in lofty engineering heights ... Apart from that, he's an all round good sort of chap who would be more than happy to field questions.

[Slippery_Pete]

A good example of pressure vs decision making is a subtle engine failure on final in a turboprop.

If done correctly while the levers are back on idle, the speed loss which occurs before recognition and corrective action can be significant.

I've seen this stuffed up many times where crew instinctively begin to run out of airspeed, and eventually start decide to push up the operating engine and go around. As the loss of control approaches, the only thing to be done is reduce the operating engine power.

Every transport pilot understands that reducing power on the operating engine will increase controllability/decrease Vmca, but so few have the brain space to implement this - only sim instructors or examiners on type who've seen it over and over and who are regularly exposed.

This is why V1 concepts have to be kept simple - knowing and understanding something is completely different to being able to reliably apply deep knowledge in high pressure/low time available situations.

[john_tullamarine]

A good example of pressure vs decision making is a subtle engine failure on final in a turboprop.

.. much the same observation for a jet .. standard exercise is to fail one on mid finals and see how long before the troops pick it up .. certainly sorts those who have a good scan from the rest.

... but so few have the brain space to implement this - only sim instructors or examiners on type who've seen it over and over and who are regularly exposed.

This is why V1 concepts have to be kept simple - knowing and understanding something is completely different to being able to reliably apply deep knowledge in high pressure/low time available situations.

Hole in one, good sir, methinks

[Band a Lot]

"Some enthusiastic operators in the NZ arena. Do you recall any factory names from the conference ?"


No don't remember that's got to be over 20 years ago now.

The enthusiastic operators stunned factory reps including Alison and CAA- when several operators of the Nomad said "regardless of what is left ahead, any engine failure below Blue Line during take-off we will abort!"

[john_tullamarine]

No don't remember that's got to be over 20 years ago now.

That's around my time in field service. Do the names Tiz Quagliatini or Terry Steen ring any bells ? One or both of those fine chaps (the field service reps) ought to have been in attendance.

.. "regardless of what is left ahead, any engine failure below Blue Line during take-off we will abort!"

Certainly a useful consideration for FAR 23 aircraft other than with a gazillion foot long runway ... especially for the N24A, which was probably the subject of the conference comments, and was very much OEI WAT-limited.

I always had much the same view in light twin flying years ago .. unless the weight was low, the overrun hazardous, and the terrain ahead for climb quite benign. Raised a few eyebrows during GA instrument rating renewals when my brief was along the lines of .. "touch a throttle prior to x ft on the altimeter and I'll close the other one and land ahead". Strange .. never had an examiner test my mettle on that one. I tell a fib .. Al B. pulled an engine at liftoff on my Partenavia endorsement at EN, years ago .. stopped with plenty to spare.

One caveat, the US government Nomads were, as I recall, transport certificated.

[megan]

A good example of pressure vs decision making is a subtle engine failure on final in a turboprop.

If done correctly while the levers are back on idle, the speed loss which occurs before recognition and corrective action can be significant.

I've seen this stuffed up many times where crew instinctively begin to run out of airspeed, and eventually start decide to push up the operating engine and go around. As the loss of control approaches, the only thing to be done is reduce the operating engine power.Sort of like F-27 FNH.Just prior to turning for finals, trouble was experienced in the pitch-lock mechanism of the no. 1 prop. The prop was feathered and the approach was continued with full flaps, but without immediately increasing power on the remaining engine. The high rate of descent was not arrested during the turn, resulting in a slightly low altitude. Power was added and speed reduced to control the descent rate, but the crew were unable to maintain runway heading. An overshoot was attempted, but the speed had dropped below minimum control speed. The left wing dropped as full power was applied to the no. 2 engine. The wing struck the ground and the aircraft crashed, coming to rest 740 feet abeam the runway threshold. Fuel tanks ruptured and caused a fire, which was quickly extinguished.

[john_tullamarine]

Sort of like F-27 FNH.

Not really. Joe was caught out by the certification basis for the aircraft prior to the changes to incorporate the PAMC report recommendations. He well and truly knew he was OEI .. just didn't have the background knowledge that OEI plus AEO landing flap was a bad idea if you intended to play with thrust on the operating engine.

Once the changes came in OEI was limited to approach flap for missed approach considerations and made OEI landings a bit more comfortable. There is an old thread on the mishap -

http://www.pprune.org/pacific-general-aviation-questions/484781-ansett-f27-crash-lst-1965-a.html

[Band a Lot]

Both those names ring bells John, but that could have been post conference too. It was a well attended meeting and my first Nomad experience (doing a export C of A on an aircraft my company just brought).
These statements were the point of much discussion with some similar comments and views to the ones about V1 here.
The CAA attendants took their caps off and the topic was discussed openly. That certainly would not happen in Australia today. That conference is probably why I am so adamant reaching V1 does not mean my decision is made, and I will continue take-off.

Rather I should take-off but is there a better reason to stay?

[john_tullamarine]

I think the present Industry view that one should keep going unless there is an overwhelming reason to suspect that the bird just isn't going to fly ... is about right .. caveat is that we are talking FAR 25 aeroplanes rather than puddle jumpers. For the latter stopping usually is more attractive than going.

[Band a Lot]

That statement John we will "usually" agree with you 100%.

And thanks for your input, you write and explain well - things I have trouble with, and many of my era of education also. But I will take the blame as I never tried at English, I regret that now.

[djpil]

"Do you recall any factory names from the conference ?" In Queenstown in the early '90s. Somewhere I have a photo of attendees. From memory, Arthur and Tiz not Terry.

[Band a Lot]

92-93 would be my guess, I went with a few from Dunedin.

[Band a Lot]

Just for Leady's benefit that photo will contain 1 red head. So copy and paste that photo at will.

Just so it can be on the internet! and then ridiculed referenced when not fit a direction of a posters wish.

Google is good and cut and paste is fine, but to bag on cut and paste on legal and government web sites as well, still refuses

Just a stick shaker moment & to do it on 2 threads is what many call 6 dix, can not be that much with 1.

[john_tullamarine]

From memory, Arthur and Tiz not Terry.

Arthur M was in the office on my watch .. may have gone to FS afterwards, though.

[LeadSled]

In general, a real-world-Vmcg-on-the-day directional departure is sufficiently rapid to bring tears to the eyes ..John T,
Ain't that the truth, as the statistics so clearly illustrate.
Anything with an RB211 in particular, always ran down (thrust decay) much faster than anything from GE or Pratt --- but with any, getting the thrust levers back on the stops is absolutely critical to staying on the runway.
Had an outer quit at just over 90Kt. on a light aircraft( No!, Not a FAR 23 aircraft, a B744) one night, Veeery interesting!! Particularly the QAR afterwards.
Of course, for those of you who actually know something about the subject, accountability for a crosswind in working out a Vmcg limited V1 does vary between certification organisations.

we were no longer required to comply with the Australian unique requirement
Actually, that wasn't a local requirement. The Australian change reflected the FAR25 design change as discussed in earlier posts.
Yes, it was ----No other country had applied the requirement, even if it did appear elsewhere, no other certification authority applied it.
As to the FAR , of course, because the effect of the CASRs 21 to 35 being made law was to adopt FAR 25 as a certification standard

but to bag on cut and paste on legal and government web sites as well, still refuses
Band a lot,

I assume this applies to my comments.

Quite simply, if something is wrong, the fact that it appears on " legal and government web site" (whatever that is?) doesn't make it right, if it is wrong, it is wrong. Or are you suggesting Government publications are faultless??

On one of my early posts, I made the point that there had, over the years, been a lot of material that incorrectly defined V1, or resulted in persons reading the material misunderstanding the correct meaning of V1. That much such erroneous/misleading material often enough appeared in "official documents" ( such as DCA examination papers) didn't make it right.

I took the trouble to give some of the history of trying to correct large scale misconceptions about V1. I even took the trouble to nominate a few other errors in what are generally regarded to be authoritative documents/sources.

Was it you (??) but somebody even claimed, but was corrected by Lead Balloon, that I had failed to define V1.

For the absence of doubt, I will repeat the correct definition of V1, based on aircraft certification standards, AS IT APPLIES IN THE FLIGHT DECK:

V1 --- The speed at which the takeoff must be continued, if the abort has not already been commenced.

This is not a "Boeing" definition, it is "the" definition of V1, based on FAR 25, and in one form or another, appears in the relevant ACs that constitute the flight test standards applicable.

Tootle pip!!

PS: John T, I would have put myself under the heading of "drummers" rather than"Drumees".

[john_tullamarine]

Yes, it was ----No other country had applied the requirement

All some years ago now as we get greyer and greyer ...

However, I'm wondering if you were thinking of the narrow runway operational demonstration defacto certification exercises ... ICAO came up with the recommendation and Oz was certainly the first to introduce that - I was involved with the first few aircraft to do the work.

For the ASDR two second delay, that appeared in FAR 25 A/L 25-42 (January 1978 at 25.109(a)) and CAO 101.6 A/L 62 (I probably have some old files somewhere which would note the date .. but not to hand). Recollection is that the two were near enough concurrently introduced. That change required the consideration be applied both to the OEI/AEO cases .. makes sense, really, as the concern was the high probability of overrunning the scheduled distance in the case of any delay due confusion or whatever and the AEO case looms significant in the pilot's mind .. see http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgFAR.nsf/0/72EBFC4FEFA87CB38525667200489C09?OpenDocument

To the best of my recollection - that might be subject to error, of course, it wasn't made retrospective here (one of our PPRuNe number was the then CASA TP at the time and would remember better than I regarding the details).

You make specific reference to the 767. A quick look at the US TCDS suggests that the frozen design standard for that Type excluded A/L 42 ... makes sense as the presumed project start would have predated 1978.

However, as the Australian examples would have come in post A/L 62 as a FOT certification, I presume that the aircraft would have been caught by the local requirement here. If that is the case, I understand your comments.

For your further commentary ... if you can recall some specifics to verify the position, I would appreciate clarifying the point in my mind.

As to the FAR , of course, because the effect of the CASRs 21 to 35 being made law was to adopt FAR 25 as a certification standard

Not relevant as the changes referenced long predated the CASRs. ANO/CAO 101.5/6 effectively required the foreign Standard with local changes to tinker a bit ... very much the bane of the Industry in many respects. Eventually sorted out post the Ron Yates' Report although not all the players thought that was a good idea.

[RHLMcG]

Sorry for my ignorance but what is "FOT"?

[compressor stall]

First of type

[john_tullamarine]

Expanding on Stallie's answer, one of the problems occasionally seen (and I presume from Leaddie's comments that this applied to the 767 - I neither flew, nor had any engineering involvement, with that very lovely passenger's machine .. enjoyed many pleasant pax legs around the network back in the days when the cabin crew had time to look after details such as wine, meals and nibbles) was consequent to a datal out of step regulatory change.

Typically, an aircraft missed a rule change in the country of manufacture (eg with FAR 25 A/L 42 in this case) due to the date of design standards freezing (ie where the OEM and FAA agree that the aircraft design will be subject to whatever version of the rules) occurring prior to the rule change effectivity.

Unfortunately, the first example of the aircraft might then have been imported to Australia after the date of an equivalent rule change here (in this case, ANO/CAO 101.6 at A/L 62). The importer then was subject to the local rule and had to run around a bit (read "spend money") to sort things out.

It always bemused me that local rule changes didn't have a suitable savings clause to provide a "get-out-of-jail-free-card" to cover this silly sort of situation where the local importer would be pushed to additional certification cost solely due to the datal mismatch.

My view was bolstered by the occasional inconsistency .. eg with ANO/CAO 101.22, for lighties, for years we used A/L 2 which worked fine .. in the main, for piston aircraft. Then it was raised to A/L 3 to cover turbines .. no good, it caused some problems for Nomad, as I recall .. so up to A/L 4 to address that concern.

Silly thing was that A/L 4 created some problems for the piston fraternity .. so the Regulator ended up accepting subsequent work to A/L 2 for pistons.

For the life of me, I couldn't see any philosophical difference between the .22 and .6 situations had a similar philosophical concession applied for datal mismatch problems.

However, I was just an engineering Industry grunt so not for me to get too worked up about things over which I had no control ...

[LeadSled]

I neither flew, nor had any engineering involvement, with that very lovely passenger's machine .. enjoyed many pleasant pax legs around the network back in the days when the cabin crew had time to look after details such as wine, meals and nibblesJohn T.,
It was also the best 150T fighter, as far as the bloke (or blokess) occupying L1 was concerned. It was right up there with the Electra as far as getting in and out of Wellington was concerned
Unfortunately (or as my wife said, "About bleeding time") I have "recycled" much of my old library, but the "two second all engine acceleration past V1" really sticks in my mind, because it had caused such a serious reduction on payload, a commercial penalty not suffered by or imposed on our competition ---- and something I pushed very hard at the time, because reactionary forces in CASA were exploring every angle to prevent the mid-1998 legislative changes and CASR introduction, including putting pressure on the operators to intervene against the changes at a political level.
It was a very close run thing that we got the changes at all, despite the efforts of "all the usual suspects" in CASA, some of whom are still writing "letters to the editor" decrying the changes to this day.
Tootle pip!!

[megan]

Let us assume that you "initate" maximum braking at or before V1, but you detect that you are "achieving" no braking and you exceed V1. Do you really "continue to reject"? Seems like you're wasting a worry Lead Balloon. As was said, you'll be on your own, and the very first to have experienced NO brakes. The following was not a brake failure per se (as in no brakes), but an inability to absorb the degree of heat generated.The investigation of one recent RTO incident which was initiated “very near V1”, revealed that the overrun was the result of 8 of the 10 wheel brakes failing during the RTO. The failed brakes were later identified to have been at advanced states of wear which, while within accepted limits, did not have the capacity for a high energy RTO.

This was the first and only known accident in the history of commercial jet transport operation that can be traced to failure of the brakes during an attempted RTO.

https://www.faa.gov/other_visit/aviation_industry/airline_operators/training/media/takeoff_safety.pdf

[Lead Balloon]

But it ended up with an overrun....

The weird thing is that when I look at the video and the other materials, it seems to me that the overarching concern is RTOs that ended up with overruns but would not have if the take-off had instead been continued. And I keep giving scenarios in which the aircraft is over V1 and I just keep getting told "continue stopping" or "you're on your own" but not a third (and to a layperson like me - obvious) option.

I note the definition quoted by LeadSled does not prohibit the un-making of an RTO decision. That definition only says in effect that you must continue the take-off if you haven't initiated stopping at or before V1. It does not say that you must not continue the take-off even if you exceed V1 after initiating stopping action.

"You're over V1: You must continue the take-off!" Got it.

"You're over V1: You must continue to reject!" WTF?

That's why it seems to me to boil down to the spool up and spool down times of 'modern' engines. However, this may turn out to be a theoretical rather than practical point.

[john_tullamarine]

Very important to keep in mind that the performance "rules" are based on, and make the presumption of, some set of standardised conditions.

If well on one side or the other of whatever switch point is relevant (Vef for a critical reject), things are fairly easy. If at the switch point then, for a critical runway in this case, everything is based on real world conditions reasonably approximating standardised certification conditions .. otherwise the end result may involve some tears.

A dynamic V1 exceedance during a critical reject is pretty well guaranteed and is part and parcel of the AFM data .. one ought not to worry too much about that distraction. Main thing is that the initial reject action be commenced not later than V1 for there to be a reasonable probability of matching the AFM figures. SOPs are based on probable outcomes .. in general, the normal stop/go decision will give the better probability of a successful outcome.

If, on the other hand, something else significant happens during the exercise and is not covered by the certification assumptions, then the commander is well and truly on his Pat Malone and makes whatever decision appears best at the time ... One example we talk of from time to time is the min weight, min speed schedule critical failure in the presence of a strong crosswind. There is a good chance that the aircraft will be out of control directionally and keeping going is not a sensible option ... a case where a reject decision above V1 may be the only sensible option.

[galaxy flyer]

I had a chance to test a plane for a harmonic vibration which occurred late in the take-off roll. The PF on these high tests was a TPS grad, TC and FAA DER, so well qualified, the test was run up to V1-10, close the throttles and let it roll. Every time, while an FTE took measurements, we neatly ran right up to the computed V1. Lesson: a plane has a a lot of energy approaching V1 and acceleration doesn't stop just because the power was closed.

GF

JT: retired last week, doing some outside business.

[john_tullamarine]

With a fuel cut plus one x throttle rundown, rather than two x throttle rundowns, the speed overshoot may not be quite as much .. but the point is made. For the near V1 failure, the priority is getting into the stopping act with the minimum delay. I can only admire those folks who have time to keep a close eye on the ASI at the same time as doing everything else ..

Best fortune with the post retirement part time work situation.

The previous mob likely to give you a jolly out to this year's Air Show ? Must be time for a wine or three ?