What is optimum v1 and improved v1

[ssongzzang]

I am about to fly B737. Our company uses ACARS for many things.




My question in using ACARS is there are two options for TODC V1 OPT (Default is balanced), Improved and Optimum.




So, whtat is optimum v1 and improved v1 ???

[777boeings]

Never heard of ACARS being used for performance calculations. Unless your operations department are doing the calculations and then transmitting the results to you via ACARS.
Also never heard of 'Improved V1'. Are you sure you don't mean 'Improved V2'?

[MarkerInbound]

There are programs where the flight crew enters W&B information and current conditions, sends it off and back comes the TO information. There can even be a "LOAD" function where the information goes straight into the FMC.

It's better to think of it as "improved climb." V2 increases to improve the climb gradient, V1 gets bumped up to make use of a longer runway to get you to a higher Vr and V2. It allows a higher TO weight so you can carry more fuel or payload.

[de facto]

Your chosen (optimized V1 ) will be between a MIN V1 limited by VMCG and a MAX V1 limited by runway lengh,brake energy limit...
In summary,

• Range of V1 can be used to optimize both performance and takeoff safety.

• Within the allowable V1 Range, all Federal Aviation Regulations related to Maximum Takeoff Gross Weight, Field Length Limits, are satisfied.

• V1 within the allowable range can be chosen to maximize margins on either Go or Stop.

• Statistical evidence from RTO accidents and incidents might lead us to consider a Reduced V1 Policy.

[AirRabbit]

Oh jeez …

• Range of V1 can be used to optimize both performance and takeoff safety.
• Within the allowable V1 Range, all Federal Aviation Regulations related to Maximum Takeoff Gross Weight, Field Length Limits, are satisfied.
• V1 within the allowable range can be chosen to maximize margins on either Go or Stop.
• Statistical evidence from RTO accidents and incidents might lead us to consider a Reduced V1 Policy.

I hope we’re not going to jump back into that long, drawn out discussion on the acceptability of flight crew members “adjusting” V1 to suit their desires on any given day. While it is true that there can be a range of airspeeds within which V1 can be selected if ALL the variables are available and taken into consideration … it is critical to know and acknowledge that this is where a little knowledge can be dramatically misused.

Of course, it is true that IF the flight crew is provided all of the performance charts that go into determining airplane performance, AND they are trained, both initially and recurrently, on how to take all the prevailing conditions (weather, runway condition, runway length, runway slope, current winds, etc.) as well as have accurate information regarding the gross weight of the airplane, the condition of the tires and brakes, and the performance of the engines under the prevailing conditions … they may be able to put all this information into those charts and determine a reasonably accurate V1 “range” … which would then provide them information about a reasonably accurate maximum speed at which a rejected takeoff could be accomplished and stop safely on the runway remaining … AND be able to determine a reasonably accurate minimum speed at which an engine failure may occur and be able to safely continue the takeoff with the remaining engine(s) operating at maximum rated thrust and get safely airborne within the remaining runway distance. The problem that is likely to occur is actually recalling what actions must be taken at what speeds … and then the clincher … what to do if an engine failure occurs BETWEEN those 2 points – can you stop … can you go? The reason a singular V1 speed is selected and used is to know that if something happens prior to that speed, you can safely STOP … and if something happens after that speed, you can safely GO.

Must we be so focused on allowing the flight crew to be "masters of their own destiny" that we're not just willing to allow, but in some cases, encourage pilots to take a rather simple performance understanding and complicate it to the very maximum - putting virtually everything into a much more critical place than it really needs to be?

[Denti]

With OEM provided performance software there is no need for all that chart business, the database takes care of all possible permutations according to the pilots wishes and prevailing conditions. Do I want that 170+kts improved climb V1 and reduce thrust by 32% or rather use that oh so much slower 110kts V1 with more thrust and that rarely used flaps 25 setting?

Of course there is only one optimum speed, depending on what kind of optimum is preferred, but there are many more possible and legal combinations of configuration and speeds. And nowadays it takes just a few seconds to consider them all.

As to the OP: you have to ask your company what is their aim for an optimum speed, with my outfit it is to use the highest possible thrust reduction for example. Improved usually refers to improved climb speeds and can allow even higher thrust reductions, albeit at the cost of higher speeds which can be quite taxing on the undercarriage if the runway is in a bad shape.

[AerocatS2A]

Air Rabbit, you are overcomplicating things. V1 is always different because weight is always different. Using a different V1 speed on different take-offs is normal regardless of whether there is a choice of V1s or not. The only thing that needs to be remembered is the V1 speed chosen for that particular take-off. I find it easy to remember because we bug it on the ASI.

On the topic of choosing a V1 from a range of speeds. This is also simple. We kind of do it in our company in that there is a range of V1 speeds available from our performance data, it is not really a choice though because the company has already decreed that we are to us the lowest V1 available. When we do the performance we have a V1 associated with our actual weight and a V1 associated with the max allowed weight for the conditions. All V1s in between are valid, we use the lowest, very simple.

[de facto]

On the topic of choosing a V1 from a range of speeds. This is also simple. We kind of do it in our company in that there is a range of V1 speeds available from our performance data, it is not really a choice though because the company has already decreed that we are to us the lowest V1 available. When we do the performance we have a V1 associated with our actual weight and a V1 associated with the max allowed weight for the conditions. All V1s in between are valid, we use the lowest, very simple.

Exactly.

Air rabbit,

By the way these few lines were taken directly form Boeing Engineering on "range of V1".
So Jeez to you from me and the boeing guys.

[AirRabbit]

Originally Posted by AerocatS2A

Air Rabbit, you are overcomplicating things. V1 is always different because weight is always different. Using a different V1 speed on different take-offs is normal regardless of whether there is a choice of V1s or not. The only thing that needs to be remembered is the V1 speed chosen for that particular take-off. I find it easy to remember because we bug it on the ASI.

On the topic of choosing a V1 from a range of speeds. This is also simple. We kind of do it in our company in that there is a range of V1 speeds available from our performance data, it is not really a choice though because the company has already decreed that we are to us the lowest V1 available. When we do the performance we have a V1 associated with our actual weight and a V1 associated with the max allowed weight for the conditions. All V1s in between are valid, we use the lowest, very simple.

Originally Posted by de facto

Air rabbit,
By the way these few lines were taken directly form Boeing Engineering on "range of V1".
So Jeez to you from me and the boeing guys.

I am fully aware that V1 is “always different” – and surely weight is big factor – but runway length, temperature, tailwinds, etc., all get thrown into the mix. I don’t have ANY problem with selecting a single V1 that is within that range of legitimate V1 speeds (emphasis on “legitimate”), and then using that valid, singular, V1 speed, the way it was intended to be used. My post was to question whether or not we were launching, yet again, on the theme that pilots should have the ability to select whatever V1 they wanted to use … some were saying that they regularly use a V1 speed that is a significantly less number than the computed V1, simply to ensure that if a problem occurred, they would have sufficient runway to stop. Others said they often selected a V1 speed that was significantly higher than the computed V1, this time however, to ensure that if a problem occurred, they would have sufficient runway to safely continue the takeoff. The fact is, if one of those two values IS, in fact, selected, and the problem that actually occurs mandates the “other” action, the result would likely be less than optimum.

If your company uses an approved method, regardless of that method, to determine a single V1 speed (again, a legitimate number), if a problem were to occur, the proper action taken would allow either the safe rejection of the takeoff OR the safe continuation of the takeoff – regardless of where, during the takeoff, that specific V1 speed is reached, I'll have to eat my fair share of "crow" - its not fun, but I've done it many times before ... actually too many! Almost any pilot will likely confirm that experiencing a problem during takeoff on 15,000-foot runways is not a huge problem regardless of what decision is made. But IF the runway is one of those that gets a bit more performance critical, ANY tendency toward a more cavalier approach to the decision of whether to GO or to STOP is infinitely more important. Hindsight is only valuable to those who are here to recognize it. The very best way to ensure the safest of outcomes is to use the proper decision making on EVERY takeoff on EVERY runway ALL THE TIME. V1 is NOT a decision speed. V1 is the point at which that decision must have been made – note the past tense - and action initiated - whether to Go or Stop. It is intended to be the point from which a continued takeoff can be safely conducted or the point from which a rejected takeoff can be safely conducted – depending on what decision had been made (and already in action) when the airplane reaches that specific airspeed. If your company procedures provide a V1 “range” … fine … I guess. I’ve not seen any such “ranges” being spit out by any computer or offered in any book or manual, but I have been out of the day-to-day grind for about a year now (with my time largely spent on issues involving training or simulation matters) and perhaps V1 speed ranges are becoming more prevalent – although I would still argue that within that range – the flight crew should select ONE speed and treat it as the defined V1 speed. If V1 speed ranges do exist, then it must be true that any number within that range of numbers MUST have been determined to provide the same airplane performance (either continued takeoff or rejected takeoff) and do so within the runway remaining at the point the airplane reaches any specific speed within that range. If that is true and a specific number is selected and used the way V1 is intended to be used … I’ll not argue with that.

While it probably doesn’t make any difference to some here (insults notwithstanding), the fact is that I personally know quite a few folks at Boeing (including some who were at McD previously) – and several other manufacturers as well – some of them for a good majority of my professional career. None of them would disagree with what I’ve said here - as what I've said is the way I was originally trained and the way I have always conducted training or evaluations. If you are interested in additional information on this particular subject, I would recommend the “Pilot Guide to Takeoff Safety,” which is available for a fee from the US National Technical Information Service in either hardcopy or microfiche. Their website is here: NTIS - National Technical Information Service

[AerocatS2A]

Air Rabbit, I don't see anyone here suggesting the use of Vspeeds outside the range of valid speeds for the day. You write a lot of words to fight a straw man.

[JammedStab]

Oh oh, Mr. Air Rabbit....what if I decided just for argument's sake to increase my min V1speed to Vr on a very, very long runway while at a fairly light weight for a personal preference reason because I felt that the engineers and FAA had not provided me with what I thought was a sufficient margin of safety.

Would you provide an argument against it in one relatively short paragraph. Can you see any reason on how this is unsafe. Theoretical question only

[AirRabbit]

AerocatS2A - You don't read it on this thread ... but there has been significant verbiage posted on precisely that theme! All I was saying is that I hoped we weren't headed down that same path yet again. Not all threads contain topics never before discussed. Stick around and you'll see that my posts here don't even begin to use A LOT of words ... and perhaps you'll eventually recognize that throwing insults - even the benign versions - don't necessarily get the accolades one might think. Take care.

[AerocatS2A]

Air Rabbit, I've been around long enough to see exactly how things work here. There were no insults, benign or otherwise. And actually by trying to head off a discussion topic you've managed to start it up (see JammedStab's post!)

JammedStab. How do you know your increased V1 gives you enough stopping distance? I know you said you are at a very light weight and the runway is very long, but how, legally, have you quantified the stopping distance required? You can't use a V1 that has not been derived from performance data. If you have arbitrarily increased your V1 without the back up of hard performance data then you are in no mans land.

[AirRabbit]

Originally Posted by JammedStab

Oh oh, Mr. Air Rabbit....what if I decided just for argument's sake to increase my min V1speed to Vr on a very, very long runway while at a fairly light weight for a personal preference reason because I felt that the engineers and FAA had not provided me with what I thought was a sufficient margin of safety.

Would you provide an argument against it in one relatively short paragraph. Can you see any reason on how this is unsafe. Theoretical question only.

I guess you didn’t notice the comment I made …

Originally Posted by AirRabbit

Almost any pilot will likely confirm that experiencing a problem during takeoff on 15,000-foot runways is not a huge problem regardless of what decision is made.

But, since you asked a theoretical question let me give you a theoretical answer … if you were on a “very, very long runway,” in an airplane “at fairly light weight,” and felt the engineers and the FAA had not provided you with what you thought was a sufficient margin of safety, I’d say you had very little understanding of what “V-speeds” really mean, and suggest you go back to school. Oh … sorry ... maybe you wanted a more serious response --

Would the circumstance you described be an “unsafe” situation … very probably not. However, humans are creatures of habit. The more often a pilot makes a cavalier decision without negative consequences the greater the chance that pilot will make yet another cavalier decision at some point. Taking that statement and adjusting it to fit the question you asked ... The number of times a pilot arbitrarily selects a V1 speed that is different from what the performance numbers indicate is appropriate and nothing happens, the greater is the potential of that pilot making another decision that is contrary to safety considerations.

[AirRabbit]

AerocatS2A – if I misunderstood your comment “…you write a lot of words to fight a straw man…” I certainly extend an apology for presuming that it was a rather mild-mannered slam.

I have noted, to a remarkable degree that there are some here who just don’t like to have anything they post questioned or corrected without getting all full of themselves. The moderators here do a brilliant job of keeping unnecessarily sharp comments from staying around very long – but even the best of them have times where minor ones slip by. Normally, my skin is rather thick and the really pointed jabs don’t get much of a rise out of me … this week however has been an exceptionally terse week – and, much to my chagrin, very well may have taken its toll … sorry.

[JammedStab]

Originally Posted by AirRabbit

But, since you asked a theoretical question let me give you a theoretical answer … if you were on a “very, very long runway,” in an airplane “at fairly light weight,” and felt the engineers and the FAA had not provided you with what you thought was a sufficient margin of safety, I’d say you had very little understanding of what “V-speeds” really mean, and suggest you go back to school.

I am by no means an expert on V-speeds and performance and more schooling would be great. Perhaps you could be the teacher.

I am concerned that the FAA and engineers did not give me a sufficient margin of safety because I have been told(subject to your confirmation) that VMCG is based on zero crosswind or perhaps 7 knots for aircraft certified in the U.K.

So if I am using min V1 and I have an engine failure at V1 with a crosswind from the adverse side, what safety margins has the FAA given me? Could it be that I'm in what Aerocat describes as no man's land by strictly following what people say is legal and therefore must be the safe way.

Originally Posted by AirRabbit

V1 is the point at which that decision must have been made It is intended to be the point from which a continued takeoff can be safely conducted or the point from which a rejected takeoff can be safely conducted

Is it really. Can you guarantee that in a 30 knot crosswind or a 5 knot crosswind.

[john_tullamarine]

I am concerned that the FAA and engineers did not give me a sufficient margin of safety

What is built into the machine is based on historical statistics and an implementation of what is reasonably able to be achieved by the Industry state of the art at the time of the relevant regulatory revision.

Important point - certification, including AFM performance data, doesn't give you a guarantee or get-out-of-jail-free card that things will always work out well.

All the system does is give you a machine which has demonstrated compliance with a somewhat artificial (but, nonetheless near-real-world) set of requirements.

If you use the certification data intelligently, then you will have a very high probability of getting from A to B without undue mishap - no more - no less.

Indeed, if you have an adequate understanding of how the design and certification animals work, then you may well choose to introduce additional conservatisms according to your own philosophies. Certainly, I have done just that in my flying, design, manufacturing and test work, operations engineering, maintenance management, etc. - I like to be able to sleep soundly without worrying unduly about this and that.

In a commercial short term sense, that might result in increased costs or reduced revenue but that's fine if you see a cogent reason to do so and can justify the decision to whomever might be relevant.

I have been told that VMCG is based on zero crosswind or perhaps 7 knots for aircraft certified in the U.K.

That's the story. Vmcg provides a line in the sand for some of the performance work. It certainly doesn't guarantee that you will negotiate a Vmcg failure event successfully on each and every occasion. Indeed, if you can so arrange without putting yourself unduly at risk in another area, you will be better off applying a pad above the limiting speeds for the reasons which obviously concern you.

Could it be that I'm in what Aerocat describes as no man's land by strictly following what people say is legal and therefore must be the safe way.

First, there are lots of places which constitute no-man's-land.

Second, what is legal is not necessarily the safest option generally or on the day. Just because I am permitted to do something .. doesn't mean that so doing is sensible or safe on the day .. road speeds limits intended for favourable conditions but applied without thinking in adverse conditions spring to mind.

Third, while one doesn't intentionally plan on operating outside whatever might be the fence around the legal paddock, there is nothing to preclude your operating more conservatively within the bounds of that paddock ...

I am always distressed by those who insist on playing about with Vmca, aggravated stalls, and suchlike ... these things are of use to provide certification boundaries. For routine operations, better to give oneself a bit of extra fat for mum and the kids ....

As a wise checkie (who was, for flying, one of a number of valued role models) once observed at the end of a line check on the 727 .. "Young John, always keep in mind the words which are etched on the front page of the operations manual in invisible ink ... 'To be used with a modicum of commonsense'. Thanks for more than a few lessons along the way, Brian and the others ...

[JammedStab]

Originally Posted by john_tullamarine

Important point - certification, including AFM performance data, doesn't give you a guarantee or get-out-of-jail-free card that things will always work out well.

If you use the certification data intelligently, then you will have a very high probability of getting from A to B without undue mishap - no more - no less.

Exactly correct. What I am pointing out is that blanket statements such as "V1 is the point at which that decision must have been made It is intended to be the point from which a continued takeoff can be safely conducted or the point from which a rejected takeoff can be safely conducted" while at the same time stating that some sort of a pilot modification of V1 is potentially very dangerous behaviour is not correct.

Well the second part is correct, it is potentially dangerous(or allowing higher risk) for a pilot to modify V1 outside of allowable limits. But there is just as much of a hidden danger in my opinion in the way the aircraft have been certified.

Therefore the statement of "The more often a pilot makes a cavalier decision without negative consequences the greater the chance that pilot will make yet another cavalier decision at some point. Taking that statement and adjusting it to fit the question you asked ... The number of times a pilot arbitrarily selects a V1 speed that is different from what the performance numbers indicate is appropriate and nothing happens, the greater is the potential of that pilot making another decision that is contrary to safety considerations" applies just as much in this case when we follow the rules as when we don't. Most of us just don't realize it.

[de facto]

My post was to question whether or not we were launching, yet again, on the theme that pilots should have the ability to select whatever V1 they wanted to use … some were saying that they regularly use a V1 speed that is a significantly less number than the computed V1, simply to ensure that if a problem occurred, they would have sufficient runway to stop.

I definitively do not agree with such reasonning.
It would just require a longer take off run if the engine failed at V1 to accelerate to Vr hence invalidating your climb segments.

I would recommend the “Pilot Guide to Takeoff Safety,” which is available for a fee from the US National Technical Information Service in either hardcopy or microfiche. Their website is here: NTIS - National Technical Information Service

Quite a good read,i regularly share it with my fos and recommended last year on this same forum.

de facto

Join Date: Apr 2010
Location: Home soon
Posts: 1,354
Of course,google "take off safety guide" you should find the document.
If you cant ill have a look in my files when i get home.
Last edited by de facto; 25th Oct 2013 at 05:49.

[AirRabbit]

First - John Tullamarine – thank you, sir – not only for the very appropriate and very accurate comments, but also for validating my earlier comments about the competence and professionalism of our moderators!

Second – JammedStab –

Originally Posted by JammedStab

Exactly correct. What I am pointing out is that blanket statements such as "V1 is the point at which that decision must have been made It is intended to be the point from which a continued takeoff can be safely conducted or the point from which a rejected takeoff can be safely conducted" while at the same time stating that some sort of a pilot modification of V1 is potentially very dangerous behavior is not correct.

Well the second part is correct, it is potentially dangerous(or allowing higher risk) for a pilot to modify V1 outside of allowable limits. But there is just as much of a hidden danger in my opinion in the way the aircraft have been certified.

Therefore the statement of "The more often a pilot makes a cavalier decision without negative consequences the greater the chance that pilot will make yet another cavalier decision at some point. Taking that statement and adjusting it to fit the question you asked ... The number of times a pilot arbitrarily selects a V1 speed that is different from what the performance numbers indicate is appropriate and nothing happens, the greater is the potential of that pilot making another decision that is contrary to safety considerations" applies just as much in this case when we follow the rules as when we don't. Most of us just don't realize it.

Well, at least you agree with the fact that “…it is potentially dangerous (or allowing higher risk) for a pilot to modify V1 outside of allowable limits.” Now, for the first part of the statement you quoted. I’m presuming that you believe that V1 is selected because it is the speed at which the decision to continue or to abort is made … right? No, actually, what I said is true and accurate … V1 is the speed from which a continued takeoff can be safely conducted or the point from which a rejected takeoff can be safely conducted – and to do this, the decision to continue or to abort must be made prior to reaching that speed … simply, if V1 speed is reached, immediately followed by an event that mandates a Go/No Go decision, and the pilot decides to reject … by the time the pilot pulls the throttles to idle, prior to doing anything else, the airplane will have accelerated beyond that V1 speed – and aborting after V1 will likely cause more problems than you may think it might solve.

I’ve suggested the document, Pilot Guide To Takeoff Safety, as a good read (and apparently de facto believes the same way), I’d suggest you read page 2-10, where it says …

One common and misleading way to think of V1 is to say V1 is the decision speed. This is misleading because V1 is not the point to begin making the operational Go/No Go decision. The decision must have been made by the time the airplane reaches V1 or the pilot will not have initiated the RTO procedure at V1. Therefore, by definition, the airplane will be traveling at a speed higher than V1 when stopping action is initiated, and if the airplane is at a Field Length Limit Weight, an overrun is virtually assured.

Additionally, it really does surprise me to hear that you are a pilot and simply do not trust the way airplanes have been and are certificated. If I interpret your comment correctly, you believe that you are regularly subjecting yourself, your crew, and all the passengers, to fallacies in the education, testing, re-testing, examination, verification, practice, analyses, etc., etc. that go into just airplane performance certification. If that is true, I cannot imagine your concern about the metallurgy, aerodynamics, structures, engines, wheels, tires, brakes, and the myriad of systems, systems interoperability … and on and on. The question comes to mind, why not find employment selling a product in which you really believe?

Finally, your comment about my statement concerning my belief that “cavalier” decisions seems to say that deciding to throw the rule book out the window on the basis of your own gut feelings is every bit as logical as choosing to follow the established performance standards. Is that correct? Even if it is only partially true, I would surmise that you are, indeed, in the wrong profession.

Third – de facto –

Originally Posted by AirRabbit

My post was to question whether or not we were launching, yet again, on the theme that pilots should have the ability to select whatever V1 they wanted to use … some were saying that they regularly use a V1 speed that is a significantly less number than the computed V1, simply to ensure that if a problem occurred, they would have sufficient runway to stop.

Originally Posted by de facto

I definitively do not agree with such reasonning.
It would just require a longer take off run if the engine failed at V1 to accelerate to Vr hence invalidating your climb segments.

Well, in reading your statement, I’m not sure if you agree with me or with those who advocate selecting an arbitrary V1 speed. You seem to agree with being able to select a V1 speed that is less than the “real” V1 … because you presume that if an engine were to fail precisely at the original, accurate, V1 speed and you’ve already decided to continue the takeoff, the only concern would be a rather minor problem with climb segments. Of course, that is a possibility – but, depending on the myriad of other potential scenarios, the outcome is at least as likely to have significantly more dire consequences. And, whether you choose to believe it or not, the more a person makes decisions that appear to be satisfactory, it is quite true (and verified) that the more likely it will be that the same person will make other, similar decisions in the future. There is never any guarantee that bad things will never happen and that you will always be absolutely safe in everything and anything you do. The same is true with operating an airplane … and, I have always thought that it is well-known that the amount of effort that has gone into, and will continue to go into, flight procedures, have all been designed to provide the very best possibility for a satisfactory result. Why would anyone throw that out the window in lieu of their own preferences? Perhaps you or one of your colleagues will be found to have an IQ well north of 200 or be recognized as the next Einstein – but until that happens, I’ll continue to make my aviation operations decisions based on the rules, regulations, and my knowledge and my understanding of from where that information came.