Calling V1 Early vs Vmcg

[ImbracableCrunk]

I recently had a snowy takeoff where V1=Vmcg.

http://www.pprune.org/tech-log/469538-b737-v1-vmcg-snow.html

My airline has a policy of calling V1 five knots early. So, if V1=Vmcg and we call V1 five knots early, that sounds like a recipe for runway excursion. Am I nit-picking?

If your airline calls V1 early, does it take Vmcg into consideration?

[BOAC]

I don't understand! Are you saying your airline actually LOWERS V1 by 5kts?? Is this company/regulatory approved? A very dubious practice. Surely IF V1 is called 5 kts early it is advisory and not actionable? IE In the situation you describe, no continued take-off would surely happen until V1? Re-assure me! I can see some perf guys getting quite edgy here.:eek:

[aerobat77]

on such a rare accasion you may with this technique indeed run into problems. the v1 of course cannot in none case be lower than actual vmcg. on lightweight like in the other thread said a derate may help.

the idea of calling v1 early is that when you at the exact v1 speak out "vee one" you are actually slightly above this speed finished the call. thats why many carriers replaced this call out with the callout "go" speaking it out at the actual v1. and this means- starting speaking go means we go.

but thats hairsplitting , there are some margins in it .generally when v1 is at or very close to vmcg it might be a good idea to abort until positivly above vmcg. 99,99% ever tried a go with an engine failure at exactly vmcg=V1 whenever on a simulator, so barely anybody can say how a real 737 on a snowy runway will handle at such a situation- and it might be not pretty.

[ImbracableCrunk]

I don't understand! Are you saying your airline actually LOWERS V1 by 5kts??

Yep. It bothers me, too.

I talked with a safety guy about this. . . he definitely danced about that very point. It went something like this: "Weellllll, we don't really lower V1, we just call it early." I'm not sure how they rationalize this. But it drives me batty.

I also worry about how this affects Accelerate GO distance if you've now got 5 more knots to cover on 1 engine.

[BOAC]

I suspect confusion is the simple answer here - what does your OM say about aborts/speeds? Surely the -5 call is merely a 'heads up'?

[FE Hoppy]

One of the airlines I work with calls V1 5 kts early. After discussion their reasoning was thus:

The Captain is responsible for deciding.
He is prompted to decide by the call of "V1" to which he responds with "Taking off".
The call "Taking off" is a comitment to go.
If an engine fails at the same time as the co-pilot is saying "V1" the captain could still stop and he will have initiated the first action below the actual V1 speed.
If the engine failure occurs while he is saying "Taking off" the actual speed will already be at or very close to V1 and he will continue the take-off.

Note that the language this company uses is not English and therfore the call "taking off" is much shorter that the english translation.

So the concept is to limit the action to V1 by having the captain decalre"taking off" at V1.

I have no opinion either way :hmm:

[Max Angle]

Seems to me that all you are doing is ensuring that the V1 call is completed AND understood by the PF by the time the speed reaches V1 which is entirely as it should be.

I believe the 777 makes an auto call (or at least has an option to do so) for V1 for the same reason, can any 777 drivers comment on when the call is started? I suspect it is about V1 -5kts depending on the rate of acceleration .

[ImbracableCrunk]

Company manual.

After “V1” call, the Captain’s hand should be
removed from the thrust levers.At 5 kts below V1, call, “V1.”Most of the reject takeoff discussion is from the FCTM, but this paragraph is slipped in:


Since V1 is the maximum speed for initiating an RTO, the decision to stop
must be made prior to V1. To account for reaction time, V1 is called 5 kts
prior to the actual V1.Most, if not all CAs remove their hand from the TLs at the V1 call.

[8che]

IBC,

Not sure which FCTM your reading but thats absolute garbage with regard V1 auto call out.

The B777 calls V1 at precisely V1 as entered in the FMC.

From the manual....

"Takeoff V1 Airspeed"

"The voice unnunciation VEE ONE sounds when airspeed reaches V1 during takeoff"

[Bob T]

A good starting point for this discussion might be to first read the approach taken by the certification authorities when defining these speeds.

Google 'EASA CS25' and then read paragraph CS 25.107 for their interpretation on VEF and V1.:)

[de facto]

A disguised call out for VEF or V event?what next?a call out for VLOF?
My airline uses this call out also,i dont agree with it but i go along.
Could be a problem if you reject at your company call of V1,ie your engine failed VEF at the real v1-10kts and you reject at the real v1-5.
You will therefore be below your VMCG...nose wheel stearing always a bonus in this scenario...
If you decide to continue at v1-5 (your airline v1) rather than stopping,this extra distance will increase your VR point therefore decrease your obstacle clearance...already low as 15ft by regulations..
Short runway was it?

[ImbracableCrunk]

8che wrote:
IBC,

Not sure which FCTM your reading but thats absolute garbage with regard V1 auto call out.

Nothing I quoted was from FCTM.

I've flown 737 with the automated callouts. I think it will call V1 early, if required, so that it can complete that call and make the Vr call on time. Nothing to back that up on, but it's something I noticed.

[8che]

Your post indicated you were quoting from a FCTM.

Most of the reject takeoff discussion is from the FCTM, but this paragraph is slipped in:


Any how allowing for misunderstood posts I wasnt aware that the B737 had an optional auto VR call as well as a V1 call.

Boeing have not to my knowledge ever designed a system that calls a V1 other than your V1 calculation.

[ImbracableCrunk]

I was responding to BOAC's question as to what was in the company manuals. Slipping something into the manuals from outside of the FCTM is what worries me.

As far as V1 and Rotate calls, you're right. I flew temporarily in Asia, and I'm back home, so I'm getting my variants and procedures a bit crossed. None has an automated Rotate call, but I still seem to remember that it was advanced so Rotate could be called on time. Not important, really.

I am worried about a V1 below Vmcg.

[Nubboy]

Contaminated runway, no FLEX so TOGA, V1 called and you decide to reject, but still below Vmcg, no problem. Symmetrical thrust (depending on reverse selected). Should stay on the runway.

However, V1 called and you loose an engine and still decide to go. TOGA thrust on one side only. Still less tham Vmcg..............

[ImbracableCrunk]

However, V1 called and you loose an engine and still decide to go. TOGA thrust on one side only. Still less tham Vmcg..............

And the airport was Ketchikan, Alaska. PAKT. Mountains on one side, slope down to the water on the other.

pakt - Google Maps (http://maps.google.com/maps?hl=en&safe=off&q=pakt&gs_upl=0l0l1l385l0l0l0l0l0l0l0l0ll0l0&bav=on.2,or.r_gc.r_pw.r_cp.,cf.osb&biw=1366&bih=624&um=1&ie=UTF-8&ei=2aPrToG1FoTKiQKGxJTUBA&sa=X&oi=mode_link&ct=mode&cd=3&ved=0CBEQ_AUoAg)

[Denti]

The auto-callout V1 on the 737 starts at V1 minus 2 kts. Recently had the interesting case where it called V1 and the speed stayed at V1 -2kts for several seconds, so in fact after the autocallout was finished we were still not at or above V1.

[have another coffee]

Google 'EASA CS25' and then read paragraph CS 25.107 for their interpretation on VEF and V1.

If you google you might as well look up how the certification is being done on vmcg.

From a practical standpoint;
1) The weight might be more favourable in comparison to the Vmcg testing:ok:
2) Most probably not at extreme (unfavourable) c.g.:ok:
3) Nosewheel steering still operative (and effective?):cool:
4) Do a risk assesment on crosswind (B.A. medium to poor:})
5) Take a moment in the simulator to asses how long the VVVVVVV oooonnnneeee call takes in relation to your acceleration and when you will decide to stop or go in this call ;)
6) What is 30 feet from the centerline in the end:uhoh:

In my memory Boeing has an excellent article on t.o. margins (runway available) in relation to V speeds. Google helps here as well.

One of those magic traps introduced by a combination of certification criteria with performance optimising tools. :D

[aviatorhi]

Said article (http://www.smartcockpit.com/data/pdfs/flightops/aerodynamics/Performance_Margins.pdf).

IMHO the 5 knot "early" call is nothing to worry about. Just a precaution against rejecting late (which can be disastrous) vs. deciding to go with a failure prior to V1 (which, even at 10 knots prior, still gets you off the runway with a good bit of clearance).

[PEI_3721]

aviatorhi, take care with your assumptions. The margins discussed in the Boeing document generally relate to time, which translates to distance.
In the diagrams showing V1, none of the options / margins changes the value of V1, which in some applications of ‘calling V1 early’ might happen.

CS 25 AMC section refers to the accuracy of published data; for V1 this is 1.5 kts, or less if it results in a change of 100ft or more in the performance distances.

From limited experience, small speed changes around the value of Vmcg can result in significant changes in the ability to control the lateral deviation, e.g 1 kt below a demonstrated Vmcg at limiting cg, etc, was the difference between a controllable 30ft deviation, and the side of the runway at the lower speed.

In aviation we often learn by knowing what the unknowns are; if we don’t know, then don’t do ‘it’.

[aviatorhi]

PEI, you're worried about getting everything down to the n-th degree and it's just not going to happen. In the big picture (and in the real world) when you're within 5 knots of V1 you might as well be at V1 as far as decision making is concerned (since we are not lowering V1, just the V1 call). Above all else, though, don't forget to fly the aircraft, if you need to reduce power and/or stop above V1 because it can't be controlled then do so.

As you mentioned, there are a lot of variables in aviation, but contrary to what you said, not all of them can be known/accounted for (there are simply too many).

Your last statement is rather confusing though. A greater level of understanding and learning is achieved from perceptions (experience) and grouping those perceptions into insights (understanding). Too often pilots become mired and obsessed with minor and unimportant aspects of an issue. Reminds me of the phrase "losing sight of the forest but finding the trees".

There is a Boeing training video which goes into great detail of what all the V speeds are and how they effect you, as well as how being above/below them effect the aircraft.

Finally, while Vmcg is a concern as far as flying the aircraft, short of the engine falling off the wing or simply disintegrating it will continue to produce some power for several seconds after the point of "failure" as it spools down. In the case of an engine fire, full (or nearly so) power. We can throw what ifs around all day to get this thing down to the n-th degree, but still, at the end of that day, 5 knots early (for the call) is not a big deal.

[aerobat77]

gents, again- the idea of starting the callout a little early is to reach the actual v1 speed when you have spoken out the "vee one" phrase. and since its a little slippery procedure e.g lufthansa as well their daughter companies do not call out "vee one" but "go" at the actual v1 speed. spelling go is faster than vee one and the procedure is that when when you start to hear the go the procedure is just to go.

so the guy the thread opener spoke to is spot on- not the v1 is lovered but just the callout is spoken a second earlier , thats all the secret about this whole discussion.

"Weellllll, we don't really lower V1, we just call it early."

[ImbracableCrunk]

so the guy the thread opener spoke to is spot on- not the v1 is lovered but just the callout is spoken a second earlier , thats all the secret about this whole discussion.

"Weellllll, we don't really lower V1, we just call it early."

Yes, that might have been the intent, but in practice it's treated as though V1 has been lowered. Captains remove their hand from the TLs at V1-5.

[PEI_3721]

Aviatorhi, re ‘not worrying about getting to the nth-degree’.
‘Worrying’ (a state of constant concern) is an essential aspect of aviation safety; it’s not about how much you can get away with – its considering what safety margin there is, are you within that margin and is there something spare for the unknown.

The early V1 problem isn’t one of technical prowess or moral principles, it about attitude.
With an “I know better” attitude – ‘that little bit doesn’t matter, it’s not a big deal’; … then what does matter? For that you have to be able to define the limiting point and thus you need to know how the issue is derived and the consequences of any deviation.

You learn through perception, but how do you know that all perceptions and experiences are justified, or of high quality to be kept as valid experience. Perceptions have to be ‘explored’, checked, and compared before you can claim insight, understanding, and knowledge.
An ‘I know better’ attitude is a major obstruction in this process – ‘those little checks and comparisons don’t matter’.
Similarly, ‘it won’t happen to me’ attitude - it’s just not going to happen:- invulnerability?
Experience should tell you that ‘it’ happens, and when it does you have to be prepared; this means not having to considering whether you act or not at a particular speed. Continuing when ‘just below’ V1 may result in a visit to the edge of the runway, hitting runway light or clipping a wing; stopping ‘just above’ V1 may end up in the mud – plenty of time to consider the correct action then.

An assumption that the engine will ‘probably’ continue to produce thrust after failing is pure supposition – in an event, you don’t know; and what about prop malfunctions, critical engine, crosswind, or a very wet runway, you have to consider the worst case and plan for that. Some, but not all are built into the regulations.

… "losing sight of the forest but finding the trees".
When walking through a forest, knowledge of the trees (a hazard) is useful for avoiding them.
Conversely, knowledge of the clear spaces provides a safe path through the forest.
I prefer to look for both.

[aerobat77]

Yes, that might have been the intent, but in practice it's treated as though V1 has been lowered. Captains remove their hand from the TLs at V1-5.

thats maybe not so good. basicly you should be "stop orientated" until positivly above V1 when something bad happens.

on the other hand such discussions are here mostly provided with pure theoretical knowledge by published and written down procedures on the internet . but an actual situation in real live is not just procedures and written down technical knowledge. and aircraft was not able , is not able and will not be able to fly by just theoretical procedures at such critical situations.

having an engine failure at nearly V1 with simultany a vmcg very close to this speed is of course a serious and a very rare thing. like said- 99.99% never had this in their entire career. when it happens its up to the PIC what he does and nothing that can be written here will help you.

by the book and a pure theoretical discussion he may be slightly wrong removing his hand ( and decide to be "go" orientated) 5 knots early.

by real live he will be jugded by the outcome of this situation when truly at nearly exact the edge of v1 and simulatany vmcg very close to this speed an engine suddenly blows , whatever he does, putting his hand back on the lever and abort or try to go.

best regards

[aviatorhi]

PEI,

As I stated... maintain control of the aircraft, this thread is discussing absolutes regarding an environment which is not absolute. The CAs responsibility is to maintain control of the A/C if that means putting their hands on the throttles after the V1 call, well, so be it. Making the call prior 5 knots prior is acceptable as far as decision making is concerned. Remember, AVIATE, NAVIGATE, COMMUNICATE.

[RainingLogic]

I suspect calling V1 prior to V1 is about getting ahead of the call out, given all the evidence of bad decision making on the roll.

With the preponderance of flex, putting all the runway behind you folks, it's become more critical to get the RTO performed at exactly the right time, as you have taken away all safety margin ahead of you.

Wouldn't a max take off, with miles of runway ahead of you preclude the need for such 'tweaking' of the call outs?

[RAM777]

i was flying 747 classics n in our company we had a standard practice of reducing v1 by 5 knots but then there was a limit it was never below Vmcg,offcourse v1 can never be les then Vmcg

[corporate-pilot]

offcourse v1 can never be les then Vmcg

I could be wrong but I'm sure an ex C130 guy told me this isn't the case on the Herc.

[safetypee]

corporate-pilot, this may have been a particular military application where ‘at risk’ periods are accepted.
There was (still is?) a few rare civil applications which use a Vstop and Vgo for contaminated operations. This results in a small speed range in which a safe stop cannot be achieved and it is also unsafe to go because of the Vmcg limit, i.e. the operation accepted the risk of an overrun; thus it would be limited to specific runways.

[john_tullamarine]

particular military application where ‘at risk’ periods are accepted

A number of examples exist in practice.

For instance, STOL certification is not embraced by civil regulators as far as I am aware. MIL, on the other hand, requires this capability for some platforms to do what they need to do.

It follows that the military spend a lot more time and effort on flight test work up to operational release than is necessary for civil Types.

Horses for courses.

[aerobat77]

iwas flying 747 classics n in our company

ram777, that is with your now 27years age without any doubt a stunning performance ! what do you fly now? 747-400, A380 leftseat ? :cool:

[A37575]

Seems to me that all you are doing is ensuring that the V1 call is completed AND understood by the PF by the time the speed reaches V1 which is entirely as it should be.

Precisely. I have observed literally hundreds of V1 calls in the simulator and thinking about it now, I would say the vast majority were called three to five knots after the ASI needle had gone through V1. This is due to the rate of acceleration and the PM not calling until V1 or shortly after. I have never seen V1 called before the ASI needle reached V1 - so the error is always when the speed is accelerating fast.

Despite tolerances built into the V1 speed I believe a call 5 knots prior to V1 of V1 is a commonsense pragmatic approach. Anyone aborting within 10 knots of V1 is asking for trouble based upon past history of the dangers of high speed aborts. Personal opinion only, of course:ok:

[A37575]

Remember, AVIATE, NAVIGATE, COMMUNICATE.

Maybe I am the classic grumpy old man but I bloody HATE that hackneyed phrase which has been regurgitated for years and years and bloody years. It reminds me of some religious liturgy mouthed by the faithful masses to ward off the Evil Eye:ugh:

[aviatorhi]

@A37575

Sorry about that, I have the same pet peeve with with the phrase "be professional" (or any variation thereof).

Anyway, the point I was making is that regardless of what anyone verbally states in the cockpit flying the airplane comes first. The example I like is when I see pilots driving past Vr (and approaching V2 quite rapidly) and still not rotating... only because the guy next to them missed the Vr call.

[BOAC]

Everyone seems to forget/ignore/?not know? (whatever) the fact that the V1 and Vr calls by PNF are not 'action' calls but backup and crosscheck calls and that PF is EXPECTED to KNOW when he/she is at V1 and Vr and take action accordingly.. That's what the 'F' in PF means.

[ImbracableCrunk]

So, can we agree that V1 should not be called below Vmcg in a B737?

[BOAC]

One sincerely hopes that is writ in your SOPs? Oh yes, I forgot, when your lot call it they don't mean V1, do they, they mean V1-5/'gee here comes V1', so that's ok and I guess it is ok to call it (but not with me).:confused:

Why not ask your FOI if he is happy with this?

[Denti]

@IC i would agree, however the automatic callout on the 737 comes early as well.

[Basil]

I think: AVIATE, NAVIGATE, COMMUNICATE is a great prioritisation; a bit like: Protection, Location, Water, Food gives you something well thought out to start with.
And AVIATE, NAVIGATE, COMMUNICATE at least discourages those whose first instinct in an emergency is to start talking to ATC.
Just my humble opinion, of course.

p.s. Never called V1 at anything other than V1.

[ImbracableCrunk]

BOAC wrote: One sincerely hopes that is writ in your SOPs? Oh yes, I forgot, when your lot call it they don't mean V1, do they, they mean V1-5/'gee here comes V1', so that's ok and I guess it is ok to call it (but not with me).http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/confused.gif

Why not ask your FOI if he is happy with this?

My thought is that since some CAs take their hands off of the TLs at the V1 call like they've been burned, it's not a, "Here it coo-ooomes," but rather a limit.

I thought I'd do the relatively anonymous thing and ask the PPRUNE Tribe for thoughts before I go beyond annoying a few instructors.

[aerobat77]

So, can we agree that V1 should not be called below Vmcg in a B737?

well, basicly of course yes. V1 or above by regulations ist the speed where you must continue the take off. and how do you want to manage this when you are still below vmcg and simply not able to hold the aircraft on the runway with a failure on the one side and toga on the other?

I thought I'd do the relatively anonymous thing and ask the PPRUNE Tribe for thoughts before I go beyond annoying a few instructors.

no, i dont think you will annoy them when you go for an open discussion about this and ask about their opinion . the same should be true when you ask your captain in a calm minute at cruise .

but i can only recommend you not to go with the attitude that they are wrong because you confirmed this by pprune.

[Tee Emm]

The example I like is when I see pilots driving past Vr (and approaching V2 quite rapidly) and still not rotating... only because the guy next to them missed the Vr call. What a coincidence. Saw the same thing recently in simulator. PM called 80 knots as per SOP and received "check" standard acknowledgement from PF.

PM then failed to call V1 and VR (on purpose) to see if PF rotated on his own bugged ASI. PF did SFA and simply stayed on the runway until at V2 plus 35 knots (no, that is not an exaggeration) the runway end was fast approaching. Even then student did not rotate until the over-run when he dragged aircraft airborne around 180 knots (VR 130 knots!)

This problem with both new and experienced pilots is more common in simulator training than many people realise. It should be emphasised in early training that these are support calls - not action calls. One classic similar thing I saw was training overseas pilots in the simulator. The airline that was paying for their training encouraged lots of talking in the cockpit under the guise of lots of talking meant good CRM - which is rubbish of course.

One of the host airline SOP was the PM would call the word 'Stabilised" when the captain had set the thrust levers to 40 percent N1 immediately prior to pressing TOGA. It was an unnecessary call but as I said the company liked the idea of more or less fly-by-mouth "support" calls.

A note was passed to the PM saying don't call "Stabilised". Now you aren't going to believe this but it happened. The experienced 737 captain released the brakes and pushed the thrust levers to 40 percent N1. The 737 slowly trundled down the runway at 40 percent N1. About 30 seconds later with the ground speed showing around 45 knots and a thousand feet of runway behind the aircraft, the captain looked across the cockpit and said in an accusatory voice "Hey! You forgot to call `Stabilised`....

Proof positive that even experienced captains can make a fool of themselves. Airmanship? Belongs to another era.

[Basil]

TM,
PM then failed to call V1 and VR (on purpose) to see if PF rotated on his own bugged ASI.
Once reached my bugged Vr and commenced (slow) rotation. At my bug +10 PNF called 'Rotate' :confused:
Yes, my bug was set 10kn too low and neither of us had noticed :\