Call V1 3 to 5kts prior
 

What's up with some of these US airlines that have procedures where you call V1, 3 to 5kts prior ?
What do you think ?

nothing's up when your fence height is ZEEERO

No clue--ssg must be their DFO--or CP:}

Some don't have a call at V1 at all....only 'minus five' and 'rotate.':}

It's all to do with the fact that V1 is a maximum 'brakes on' speed if you decide to carry out an RTO. If the decision process starts at V1 and the decision is then made to RTO, the brakes on speed would be above V1.

Boeing state that the decision to carry out an RTO must be made prior to V1 and the first action (thrust levers closed, brakes on) must be carried out at, or prior to, V1.

Different carriers cater for this in different ways. Some call V1 slightly early, others will always use the WET V1 figure, even on a bare/dry runway. Ours just emphasises that the decision to RTO has to be made prior to V1 and that the RTO must be commenced by V1.

As an airmanship point it is always important to know what your limiting performance criteria is. Eg, if you are climb limited you will have some spare stopping performance in hand but if you are field length limited then a V1 RTO will leave you in very close proximity to the wrong end of the runway.

The logic is that if you start saying "v1" 3 -5 seconds prior to hitting the speed, the pilot flying knows that you have reached V1 when you finish saying "v1". If you start to call v1 once you reach v1, by the time you finish saying it you are past it and therefore no longer in a position to make a "go-no go" decision.

Anyhow, that's the idea.

Read some of Old Smokey's Posts and You'll know that's bad:=

Calling V1 at V1 has more to do with pilot incapacitation then stopping---the PF should reference his his/her own ASI

I dunno about others, but we say "Vee One" at V1, 'Vee Rrrr, Rotate to XXX degrees" at VR, and call out V2 as it passes. Target climb V2+10.

No need to call anything prior, and it all happens soon enough.

never thought it neccesary to call V are and Vee two---some SOPs require it though

Calling V1 at-5 kts is standard practice with my airline.

As already stated, to ensure that a reject is not started above V1.

By the time you have said it it's too late to stop (unless you are 'ssg') :eek:

Quite a few aircraft in our fleet call V1 on their own (V1-autocall), only call the PM has to do in that case is "Rotate". If we do not have automatic V1 calls we have to do it ourselves. No response on either call is required, but at V1 the CPT has to remove his hands from the thrust levers, and on "Rotate" of course rotation has to be started.

Personally i was trained to start saying V1 3kts earlier, however that is not SOP in my current company so i just do what they require.

LaGuardia Takeoff
 

If you took off from LaGuardia you would understand this procedure. Runway is short and a nice pool of water is waiting for you at the end. Totally makes sense.

Last time I plugged in the numbers in the MCDU, we had only 6 feet of accelerated stop distance remaining if we decided to abort exactly at V1. Do I want to abort in the case right at V1? I don't think so. Remember this is based on perfect conditions.

We've got several calls that I'm not sure are necessary, including the V2 call. However, at Vr, we not only call it out, but also add "Rotate to XXX degrees," as part of the standard callout. It's printed on the TOLD card anyway, as our target engine-out pitch attitude, but the SOP is to call it out verbally, anyway.

I'm one of those who responds with a thank you or precedes with a please. I don't see that as extraneous or out of line, but I've sure met a few who had a fit because those "extra words" were apparently just too much to handle. When I say "Set reduced thrust," and the FE responds "reduced thrust set," I reply "thank you." It's not in our standard callouts. I did it in the sim and got loudly berated by the check airman. That individual felt that any extra syllables might bring down the four horses of the apocalypse and perhaps a small infestation of rodents. I don't think common courtesy is out of line.

I sat down with an old salt FE one day who said "You can call me anything you like but I expect a please and thank you." I respect that, and try to give it anyway. Even if it's an extra word.

As Bananasx2 states the problem comes from being field limited. If you are and you call V1 early do, you enough runway to accelerate to Vr and clear the screen height in the event of an engine failure between your artificially reduced V1 and Vr? Possibly not. I think the Boeing verbiage is that a stop must be initiated by V1 but the mechanics of it allow for a certain amount of 'thinking time'. There is a value laid down but I can't lay my hands on it currently and it is therefore understood that the aircraft may accelerate beyond V1 by a certain margin before the stop is initiated. I have seen written in several manuals that a stop initiated at V1 on a limiting runway may result in the aircraft not coming to rest on the paved surface. This is due to the calculations being made for a perfect aircraft, on the perfect day, by the perfect pilot and we all know there is no such thing as the perfect aircraft or the perfect day!

Yes, with the current price of fuel we are using Flex takeoffs. Obviously, if anything seem out of place we go to TOGA. No questions asked.

It is not the first time I takeoff from short runways and a pool of water (aka LGA) and every time the software gives you performance numbers right on the edge for the most optimum Flex temperature. 2 weeks ago, I remember the accelerate stop distance remaining being 1 feet! You can imagine how our briefing went...

It's to cover the time it takes to remove your hand from the throttles to the yoke.

Well on the 'Bus the autocall is a couple of knots or so before V1, and it's NOTHING to do with incapacitation.... It's just that if you are length limited it stops you from over running if you start the abort at V1 - it takes a couple of seconds to even DECIDE to stop - by then you're V1 PLUS X kts and you're possibly stuffed...

v1
 

I think 2 seconds of reaction time should be allowed for in the v1 calculation. Dont know where I got it from but it came up when I read the discussion.

Not much but at least something

Please cite a reference for "Boeing," since your claim is contrary to the governing FAA regulation. Note that the FAR already mandates that V1 is corrected for realistic reaction times, determined via flight testing:
For those who choose to call V1 3-5 knots or 3-5 seconds (per shazzmo) prior to actual V1, you risk that in the limiting case of accelerate and fly with an engine failure at LESS THAN V1 but AFTER the call, you will not get off the ground in time because of the additional acceleration time without the engine. If you KNOW what the limiting factor is in your specific circumstances, you MIGHT want to take that risk. If you do not KNOW the limiting factor for THIS runway/weather/TOGW case, you may want to reconsider...

On the Boeing 737's with the AUTO V1 callout, the call is made exactly two knots before V1.


kme...thats probably where you got the figure.

Boeing Flight Crew Training manual as issued to our Airline.

Gentlemen....
 

The issue of V1 is a touchy one. Many operators have different policies, based on their individual experiences.

One thing to note, depending on when the aircraft was certified, the V1 issue is different. As stated above, we're supposed to have something like two seconds reaction time...and still be able to get it stopped. But, this is based ont the new certification standards (both JAA and FAA).

I'm not sure about the NG737, but the older ones were certified under the old system...whereas, you really need to be transitioning to the 'stopping mode' at (or before) V1. Under the old certification standards, any speed above V1 (in an abort scenario) is not good (e.g. two seconds after reaching V1).

The Bus, on the other hand, even though it was produced under the old set of standards, meets the new criteria. That is, you can actually 'initiate' the abort at V1...and still have runway to get it stopped. "Initiate" means, you recognize the need to reject the takeoff (at V1), and promptly do the drill. Again, under the old certification standards, you don't have this.....under the old standards, you really need to have the stopping process going for you as you reach V1.

I can't remember exactly when this certification change occurred, but I'm thinking it was around the early nineties. Again, not sure about the 737NG, as it may still be certified under the original 737 certification rules.

From a practical standpoint, we're talking about only a couple of knots. Sure, as stated above, screen height is affected to some degree, but not significantly...i.e. not nearly the difference of 35 feet vs. 15 feet (dry vs. wet).

Of course, this is all based upon a 'balanced field length'. Some might define 'balanced field length' as "You're dead if you stop; you're dead if you go!" Again, in practice, if bad things happen near V1, you need to be "go minded" as Boeing and Airbus (both) recommend. Who defines 'near V1' is why we have stripes on our shoulders.

Fly safe,


Pantload

Boeing Go /No Go videos

Part 1

http://www.youtube.com/watch?v=raCnJgDnijw

Part 2

http://www.youtube.com/watch?v=WhVVA...eature=related


3 Seconds decision time....?

Accelerate stop go distance remaining of less than 6ft :\....that could prove interesting

Taking the liberty of knocking of 3-5 kts from your performance calculation, to my opinion defeats the whole purpose of calculation.
If you move your V1, it will help you to stop, but it won't help you if you continue your takeoff with an engine failure that could have happened between that -5kts and V1. So what do you do when you are obstacle limited but have enough runway in front of you. Do you call V1 after V1 ?
I'd rather get off the runway while on the ground, than hit the building while in the air.
These procedures go against the whole performance calculation that was designed by the builders engineers, and give the freedom to airlines and pilots to interpret a given situation to their own standard.
Where do you draw the line ?

V1 is scheduled after Vef. The time gap depends on the certification standard. The gap is already in the calculation so you need to make the first action to stop at or before V1.

If you make the decision to go before V1 you will compromise your screen height.

If you make the first action to stop after V1 you will compromise your stopping distance.

This is for the engine failure case only, and when at your max take off weight balanced field length limited.

Other cases will be different.

It is possible to include stopping distance allowance to hedge the stopping case and of course line up allowance must be used where necessary.

It's just not black and white.

I totally agree with TQ.
If you choose to tweak the numbers for a balanced T/O, then you better think about the other end of that equation too. :hmm:
If you continue with an EF at V1-5, then you need abit more than your ASD to get to your 15' screenheight at rwy end.

Interesting...
 

Well, you are not knocking off 3 to 5 knots from your calculations. You're simply calling V1 in a timely manner to ensure that you do not initiate the rejected takeoff at a speed above V1. In point of fact, you're respecting V1, not changing, modifying, etc.

Again, the issue is dependent on when the aircraft was certified. Under the old certification, you really don't want to allow the aircraft to attain a speed above V1 before the stopping actions are initiated. If you call V1 at V1...have an engine failure at V1...and you try to stop (assuming you're field-length limited), you've got a problem....because, before you know it, you're going V1 plus a couple...then, you initiate the rejected takeoff drill....BIG PROBLEMS!!!!!

We're talking only a second or two in time.....makes a big difference for 'stopping'...not much difference in 'going'. According to engineering data, even if you lose an engine at, say, V1 minus 2 or V1 minus 3...and continue the takeoff...you'll find the reduction in screen height is reduced minimally...like maybe ten or so feet. (Still above the 15 foot wet-runway figure)

But, if you lose one at V1 minus 2, and you try to stop...you'd better hope you do things very quickly...you'd better hope the brakes are in good shape (not worn to just above minimum limits)...you'd better hope the runway surface at the other end of the runway is not contaminated...or full of rubber or other crap....in other words....if you reject at V1 (and you're field-length limited), things have to be perfect for you to stop before the end of the runway.

In contrast, losing one at V1 minus 2 and continuing the takeoff will have minimal consequences. This is why the manufacturers say, as you approach V1, you need to be more 'go minded' and less 'stop minded'.


PantLoad

Bubi...that's what I thought. No doubt using full power, would give you more room at V1 to make a decision, which has been the main argument against flex for some time.

Not "the" arguement. Just your argument. Of course, it's a lone argument and you keep getting banned, only to pop up under a different rock each time...and it's a weak argument with no foundation. Doubtless you'll keep making it, though.

You're on the ignore list as of...now.

Re all those discussing "reaction times". You emphatically do not have two seconds reaction time at V1.

25.107(a)(2) requires that V1 be not less than Vef (engine failure) plus pilot reaction time.

Therefore the reaction is to the engine failure - not to the point at which V1 is attained. And the time is not necessarily two seconds either - it's however long the test pilots took during certification testing. (AC25-7A directs that the time used for calcs be not less than one second).

The notion of a two second reaction time is likely coming from a reading of 25.109, which states ...

Yet a review of AC25-7A reveals that it states quite categorically that the 2 second distance allowance is not a "pilot reaction" time and must not be considered as extending the decision-making and reacting process past V1 ...

(Section 11(c)(3) of AC25-7A chg1, page 80-6, for those who wish to see it in its full context)

So AT V1 you MUST have taken the first action to stop the plane (if you're going to abort) and you have two further seconds to complete ALL the actions required to stop the plane if you are to achieve the OEM's calculated stopping performance. Any slower timings and you are not guaranteed to remain on pavement.

=====

Given all that, it makes perfect sense for the V1 call-out to begin before V1 - for it to be useful, the fact that V1 has been passed must be processed by the PF at the point of V1, if not before. If the PNF starts to call "Vee-one" as V1 is attained then by the time he has finished, and the PF has processed the info - perhaps 0.5 seconds for reasonable human reaction times - it's already too late.

@PantLoad:
While a perfectly respectable hope - any margin is worth having in a max energy RTO - the numbers are, at least in theory, good for "fully worn" brakes, and must be demonstrated with 90% worn brakes in the max KE case.

Question????
 

Mad Flt Scientist:


With regard to brake condition at the beginning of the RTO, is the old certification standard with worn brakes? I have to research this, because I thought the old standard was with new brakes...the new standard is with (I can't remember)...either 50% or worn-to-limits brakes.

Please correct me...I'm not sure...but, I'm thinking that was changed, too, along with the V1 standard. (You usually have a pretty good handle on details like this.)


PantLoad

Sorry, I missed that your whole post had an "old cert rules" qualifier in the second para.

The new rules require worn-to-limit brakes (or a correction to that state). As to the old regs ... wait one.

OK, the max KE demo with 90% worn brakes came in with Amdt 25-92 in 1998. Prior to that the Accel-Stop para (25.109) had NO max KE requirement. (Though other paras may have applied, at least in part - 25.1301 "performs its intended function" comes immediately to mind as one candidate para)

The fully worn requirement is actually 25.101(i) and also came in with Amdt 25-92. Again, one could have argued about other regs. But there's nothing explicit.

Mad Flt Scientist
 

Yep, you came through again!!!! Thanks. You're usually very good for posting the details.

It was in the early nineties, as I recall, a major carrier in the U.S. had an RTO accident...short/wet runway, non-standard grooving, a lot of rubber at the end...anyway, while they hung the captain, a lot of procedures changed. One new procedure that was implemented was that of a reduced V1 when on wet runways. Of course, another change in the SOPs was that of calling V1 five knots early...stressing the importance of (in the case of rejecting the takeoff) beginning the RTO procedure no later than V1 (in essence, not allowing the aircraft to accelerate above V1).

I remember the political nonsense (feel free to substitute another eight-letter word), as I was at the seminar held by Boeing that addressed this particular accident.

At the end of the seminar, there was a Q & A session...a couple of Boeing test pilots and engineers were running this thing...and, I had a bunch of questions...several questions they didn't like hearing, much less answering. My relationship with my company (my job) and with Boeing were never the same after that. In fact, my boss explicitly told me in front of everyone to sit down and shut up.

But, while the captain of the aircraft involved in the accident certainly had some blame coming to him, he was the victim of a stacked deck of cards against him. I had to make that point to Boeing. (Of course, they already knew this...I just wanted them to know that we all knew it, too!)

The accident was a fatal one...the captain has to live with this for the rest of his life. But, as a result, several SOPs have changed; runways are now getting standard grooving; runways are being steam cleaned more often. And, hopefully, things like this will not happen again.

Thank you, again, for this post and all your other posts which are quite informative.


Fly safe,

PantLoad

In flight testing, the v1 one has a 2 sec decision, and a 2 sec reaction built into it. so why would you take an extra 5 sec off? why not go with the flight manual?

CattleFlyer - All I said is if something doesn't feel right during a Flex takeoff you can go to TOGA at anytime. Additional thrust is available and I will use it if necessary. I have not read your previous posts but you seem to point out that Flex takeoff are not safe - wrong. Read more about balance fields. You will have a better understanding of the concept of V1.

Flight testing has no such thing, nor do the certification rules. And, as explained above, the flight manual is predicated on not just recognition but reaction having started at V1. Which means if AT V1 is when you start the "V1 process", you're already behind the aircraft.

It's very simple.

Pilots with zero reaction time, able to pronounce "vee-one" in zero seconds are right to call V1 at the time they see their ASI pass through one.

Others, who somehow fail to meet the criteria have to cater for it. Personally I call "GO!" 3kt before V1, per SOP.

Do I see v9.0 here?

Save on some fuel? Do I read that right? You are talking about flex/derate take offs right? Last time I checked, fuel burn wasn't the considered factor for flex/derate take offs.

I thought I had heard all the calls that airlines make, but calling the target attitude during the rotate call is surely one of the most ridiculous ones out there. The attitude changes that much to have to have a reminder at a time when the pilots should be concentrating on their job of flying the airplane? For the 2 minutes or so a modern pilot actually flies, that is? And will the PNF be smart enough to adjust the figure for an engine failure? And what about the flight director, which has been programmed to give the best attitude soon after lift off anyway? Is the PF so ignorant he even needs this call? If he does not know what attitude to rotate to what is he doing in the seat?
Talk about flying with your tongue! What would you do if there was a genuine need to make a callout of a malfunction or error? The pilot is already expecting the garbage call, and will tune it out. If the PNF is wrapped up in this call, will she see anything going wrong elsewhere?
Keep the calls to a minimum. Only call when there is a non-standard situation, so the call will be heard and listened to. Extraneous calls of the bleeding obvious reduce safety by being a distraction and reducing situational awareness.
I surely wish the airlines would stop mucking about with the manufacturers' operational procedures.