What is optimum v1 and improved v1 [Archive]

AirRabbit

5th Jun 2014, 21:53

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

6th Jun 2014, 03:29

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

6th Jun 2014, 04:29

de facto

6th Jun 2014, 08:19

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.:E

AirRabbit

6th Jun 2014, 22:39

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.

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 (http://www.ntis.gov/)

AerocatS2A

7th Jun 2014, 00:32

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

7th Jun 2014, 02:14

AirRabbit

7th Jun 2014, 02:22

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

7th Jun 2014, 02:38

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

7th Jun 2014, 03:38

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 …
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

7th Jun 2014, 04:02

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

7th Jun 2014, 05:40

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.

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

7th Jun 2014, 06:18

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

7th Jun 2014, 07:10

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

7th Jun 2014, 07:57

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

7th Jun 2014, 21:29

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 –
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 –

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.

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.

de facto

7th Jun 2014, 21:37

JammedStab

7th Jun 2014, 23:05

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?

There are all kinds of examples of aircraft that met certification standards that have in fact failed with serious consequences. From the aft cargo door failure leading to 346 deaths on a Turkish airlines DC-10, to the Concorde fuel tanks to a main cargo door on a United 747 near Hawaii to a United DC-10 in Sioux City. Certification has worked well but is no absolute guarantee. However, I have accepted the risks just like crossing a street. What I don't accept is an absolute guarantee of safety. Your statement of following V1 as certified is the safest course of action of course as a general rule. All I stating is that there is something quite significant out there that many are unaware of. That under a critical engine failure scenario with min V1 being slightly higher than VMCG, it is not nearly as safe as you state to just continue.

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.

You will notice that I started off the conversation by stating that this was just for arguments sake. But, if I am in the wrong profession, please tell me how it is any less cavalier for the authorities to certify that an aircraft is supposedly safe to continue with an engine failure at V1 when there is what we frequently experience ie. a significant crosswind.

AirRabbit

8th Jun 2014, 04:05

There are all kinds of examples of aircraft that met certification standards that have in fact failed with serious consequences. From the aft cargo door failure leading to 346 deaths on a Turkish airlines DC-10, to the Concorde fuel tanks to a main cargo door on a United 747 near Hawaii to a United DC-10 in Sioux City. Certification has worked well but is no absolute guarantee. However, I have accepted the risks just like crossing a street. What I don't accept is an absolute guarantee of safety. Your statement of following V1 as certified is the safest course of action of course as a general rule. All I stating is that there is something quite significant out there that many are unaware of. That under a critical engine failure scenario with min V1 being slightly higher than VMCG, it is not nearly as safe as you state to just continue.

You will notice that I started off the conversation by stating that this was just for arguments sake. But, if I am in the wrong profession, please tell me how it is any less cavalier for the authorities to certify that an aircraft is supposedly safe to continue with an engine failure at V1 when there is what we frequently experience ie. a significant crosswind.

I almost don’t know how to respond to this… however …

I think you’re letting us know that you’re of the opinion that the airplanes currently in service around the world are plagued with flaws in design, construction, and certification, and most in this industry are “whistling in the dark” by blindly accepting that the existing certification standards are, at the very least, insufficient to find, let alone correct, those hidden flaws and discrepancies – or – stating that all of the governmental and individual airplane manufacturer efforts, plans, checks, examinations, inspections, considerations, alterations, etc., etc, is a “cavalier” approach to airplane certification. I wonder … have you ever read through the theory and requirements of airplane design and construction? Have you ever reviewed, even casually, the specific standards that are required to be met, and the lengths to which everyone must go – all while under strict supervision and regular checking – in order to have the work they have completed be approved for their specific contribution to the process that takes an airplane from a pen-and-paper design to being a functional airplane in flight? There isn’t anything man-made that is perfect – and I think you probably recognize that most humans understand and accept this fact. If you are so highly skeptical of the man-made processes that have been put into place to govern the design, development, construction, examination, certification, and all of the limitations and requirements that have been placed on each to be authorized to conduct the kinds of operation that each is qualified to perform – I would, indeed, and most respectfully, suggest that for your own peace-of-mind, select a different line of work. Additionally, and I think, significantly, equating the exceptionally rare occurrence of a failure of a portion of an airplane (as you described) with the kind of errors that would be deliberately thrown into the mix by not following the established procedures, goes well beyond the realm of realism and borders on something like paranoia.

With specific reference to one of your statements … “a critical engine failure scenario with min V1 being slightly higher than VMCG … is not nearly as safe as you state to just continue” … let me offer the following:

If the engine were to fail – calling into play the VMCG issue – and if the failure were to occur prior to V1, the established standards would call for the pilot flying to reject the takeoff. Of course the airplane would be below VMCG but that should not be an issue in controlling the airplane as the controls used would be the nosewheel steering and wheel brakes.

However, on the other hand, if the engine failure were to occur after V1, again, the established standards would call for the pilot to continue the takeoff. Of course until reaching VMCG the pilot would have to maintain directional control through the use of the same nosewheel steering (either rudder pedal or “tiller” depending on the degree of asymmetrical thrust encountered with the failed engine) which is what the pilot would have been using up to that point. The only question would be if the right seat pilot was making the takeoff and the asymmetrical thrust was significant enough to override the capability of rudder pedal control of the nosewheel position – which may require the left seat occupant to assist with directional control for the period during which aerodynamic control was still building – and when built sufficiently, aerodynamic control would be able to be achieved by either pilot.

In either scenario, I think the airplane design and proper training on the use of the available systems and correctly using those systems would provide for a safe and hopefully uneventful conclusion to the scenario you have proposed.

JammedStab

8th Jun 2014, 15:04

I wonder … have you ever read through the theory and requirements of airplane design and construction? Have you ever reviewed, even casually, the specific standards that are required to be met, and the lengths to which everyone must go – all while under strict supervision and regular checking – in order to have the work they have completed be approved for their specific contribution to the process that takes an airplane from a pen-and-paper design to being a functional airplane in flight? .

No I have not read the endless information about certification and have no intention of doing so. I have read plenty of accident reports though such as the ones I mentioned earlier. While your blind faith in certification is commendable, the line of thinking has had multiple failures over the years including but not limited to the accident I started earlier.

1) Air France Concorde: "in-service experience shows that the destruction of a tyre during taxi, takeoff or landing is not an improbable event on Concorde and that such an event may cause damage to the structure and systems. However, such destruction had never caused a fuel fire.
The accident which occurred on July 25 2000 showed that the destruction of a tyre - a simple event which may recur - had catastrophic consequences in a very short time without the crew being able to recover from the situation.
Consequently, without prejudice to further evidence that may come to light in the course of the investigation, the BEA and the AAIB recommend to the Direction Générale de I'Aviation Civile of France and the Civil Aviation Authority of the United Kingdom that the Certificates of Airworthiness for Concorde be suspended until appropriate measures have been taken to guarantee a satisfactory level of safety with regard to the risks associated with the destruction of tyres.” http://www.bea-fr.org/docspa/2000/f-sc000725a/htm/f-sc000725a.html

2) United 811 in Hawaii - Contributing to the cause of the accident was a deficiency in the design of the cargo door locking mechanisms, which made them susceptible to deformation, allowing the door to become unlatched after being properly latched and locked. Also contributing to the accident was a lack of timely corrective actions by Boeing and the FAA following a 1987 cargo door opening incident on a Pan Am B-747. http://www.ntsb.org/Wiringcargodoorlite/Additional%20Aircraft%20Accident%20Reports_files/AAR92-3.pdf

3) United DC-10 Sioux City - The Safety Board considers in retrospect that the potential for hydraulic system damage as a result of the effect of random engine debris should have been given more consideration in the original design and certification requirements of the DC-10 and that Douglas should have better protected the critical hydraulic system(s) from such potential effects. As a result of lessons learned from this accident, the hydraulic system enhancement mandated by AD-90-13-07 should serve to preclude loss of flight control as a result of a No. 2 engine failure. Nonetheless, the Safety Board is concerned that other aircraft may have been given similar insufficient consideration in the design for redundancy of the motive power source for flight control systems or for protecting the electronic flight and engine controls of new generation aircraft. http://www.airdisaster.com/reports/ntsb/AAR90-06.pdf

4) Turkish DC10 - Following the American Airlines event, the FAA had written, but not released, an Airworthiness Directive aimed at correcting the cargo door failure. McDonnell-Douglas developed three service bulletins for modification of the cargo door, and proposed to the FAA that rather than issue an AD, the FAA allow the manufacturer to issue the service bulletin as mandatory (an unprecedented action for an urgent safety issue of this magnitude). The FAA concurred with this proposal, and the service bulletins were issued, but their incorporation was not mandated by the FAA. Many carriers voluntarily incorporated the service bulletin modifications, and retrained ground personnel on the proper operation of the door closure mechanism. At the time of the accident, Turk-Hava had only incorporated two of the three service bulletins, although airplane maintenance records reflected that all three had been incorporated. The lack of the final modification, and the fact that the modifications had not been mandated by the FAA was viewed as a major factor in the chain of events leading to this accident.http://lessonslearned.faa.gov/ll_main.cfm?TabID=1

With specific reference to one of your statements … “a critical engine failure scenario with min V1 being slightly higher than VMCG … is not nearly as safe as you state to just continue” … let me offer the following:

If the engine were to fail – calling into play the VMCG issue – and if the failure were to occur prior to V1, the established standards would call for the pilot flying to reject the takeoff. Of course the airplane would be below VMCG but that should not be an issue in controlling the airplane as the controls used would be the nosewheel steering and wheel brakes.

However, on the other hand, if the engine failure were to occur after V1, again, the established standards would call for the pilot to continue the takeoff. Of course until reaching VMCG the pilot would have to maintain directional control through the use of the same nosewheel steering (either rudder pedal or “tiller” depending on the degree of asymmetrical thrust encountered with the failed engine) which is what the pilot would have been using up to that point.

Really, with a 30 knot crosswind from the adverse side. Based on all those certification test done on calm wind mornings and evenings. As well, I would suggest staying off the tiller. Most aircraft recommend using it for lower speeds only.

AirRabbit

8th Jun 2014, 18:11

AirRabbit

8th Jun 2014, 19:54

Air rabbit,

I really have no idea what you are blablaing about.
I never wrote that one should use a different V1 than given from his perf data.
I never said that V1 was a decision speed as i know it is a speed at which the first action must have been made,a definition that was changed a few years back.

Your way of discussing is quite abnoxious and no wonder you get burnt here now and then...jeeezzz,but then dont come and moan back here people put you back into place...

I was referring to the post you had made …

Quote:
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.
Your lead-off statement was “I definitively do not agree with such reasoning.” And, as I said, “…I’m not sure if you agree with me or with those who advocate selecting an arbitrary V1 speed…” – I wasn’t able to determine the “reasoning” with which you were definitively not in agreement.

But, notwithstanding that question, you also said “It would just require a longer take off run if the engine failed at V1 to accelerate to Vr, hence invalidating your climb segments...” and by “IT” I was, and remain, under the impression you were describing the selection of a V1 that was less than the V1 speed described in the regulations (- and, with some hesitancy, I understand that there may be some newly developed and distributed software that yields a “range” of V1 speeds, although I’m not at all sure how the various parameters are addressed in such a V1-speed range -). If you were not making such an acknowledgement – I did, indeed, misunderstand your comment – and I’ll offer you my apologies for my misunderstanding.

However, if you were making that acknowledgement, as you would certainly know, as you have stated, V1 is NOT a decision speed – so if an engine failure were to occur AT V1, regardless of what the V1 value was determined to be, the procedures should remain consistent, and I would presume that would require that the takeoff would be continued. I am presuming (again) that if the V1 selected was within a range of “acceptable” V1 speeds, selection of any of those speeds should provide the same safety factors. If not, I cannot see why such an authorization would be granted. So, the fact that “…it would require a longer take off run if the engine failed at V1 to accelerate to Vr, hence invalidating your climb segments…” seems to be at odds with the premise that selection of any of the V1 speeds within an “acceptable range” of V1 speeds would provide the same safety factors. If, indeed, selection of a V1 speed that would “…invalidate your climb segments…” that selection doesn’t seem to be a viable alternative, I have trouble understanding why the operator would suggest and why the regulator would approve such a procedure. Under the “traditional” method of determining V1 speed, if the engine were to fail precisely at the computed V1 speed, with the decision to continue the takeoff having already been made, the climb segments determined should be able to be met. THAT is what the selection of that speed is designed to ensure, and the understanding is that any engine failure after the decision is made to continue, very well may not provide the same climb gradient as would have been achieved with all engines operating, but it acknowledges that, with such an engine failure, the gradient would be lessened with each knot closer to V1 that the engine actually failed – with the minimum climb gradient being able to be met with the engine failure occurring at the most non-favorable point along the takeoff run – AT V1. Again, THAT is what the selection of V1 speed is designed to ensure.

Now – with regard to your comment that my discussions are “quite abnoxious” … I guess the only thing I can say is that I regret you find my comments so personally difficult or irritating, and I would recommend that you simply not read them in the future. Also, I feel that I know what place I occupy – whether some here agree with my opinion or not – and I assure you, having someone not agreeing with me is not unfamiliar. I know that I attempt to comply with all the forum’s procedures and policies … as John T regularly says … “play the ball, not the opponent” and that is what I attempt to do.

JammedStab

8th Jun 2014, 21:40

JammedStab:

You cited 4 terrible accidents dating back to 1974. Statistics (if you believe in such mundane things) say that there are approximately 100,000 airline flights per day – and if you throw in charter and cargo flights the number doubles. And I am fully aware that there were many more accidents than those you cited – although, as I think you would agree, not ALL of those additional accidents could be attributable to design/manufacturing/structural defects. So, given these numbers during the 40 years of time since the Turkish DC-10 accident, there were more than 14.6 billion flights, and during this time there were 497 airline accidents - not an estimate. With these numbers, it is easy to see that the ratio of accidents to flights is astonishing low … about 1 accident for each 29.4 million flights – a rather low average by anyone’s estimation. Of course ONE accident is one too many. But, again, we’re dealing with humans. Humans are fallible. Accidents DO happen. I’m not happy about it – nor is anyone I know happy about it. But to offer some kind of comparison outside of the aviation community, you might be interested to know that in the US – a reasonably modern country with reasonably modern safety standards – there is 1 automobile accident for every 30 automobile trips every year. I would have provided a similar data comparison for Europe or the world had I been able to find the relevant data. But, basically, the US data for automobile accidents should show the relative safety ratio to that ratio in aviation, even after using the actual number (497) of airplane accidents over that 40 year history, is a robust 29.4 million to 1 … and that is with a ratio of 40 years to 1 year.

You are of course, absolutely correct. The overall certification system has resulted in an extremely safe system and I have never denied that. And yes, there are other types that have been certified incorrectly and crashed such as the Comet and ATR-72. And in order to respond to the "that was 20 or 40 years ago argument", it sure was fortunate that the 787 battery fire happened on the ground. The result, a decertification of a recently certified aircraft where the authorities who really not particularly aware of how the whole system worked just decided to trust Boeing's good word. http://aviationweek.com/awin/faa-boeing-grilled-about-battery-certification (strongly suggested reading).

As I said, accidents do happen – sadly – but they happen, regardless of the reason. However, to say that aviation accidents (particularly with the substantially reduced number that could be even remotely attributed to a structural or mechanical problem) are a result of “cavalier” decisions made by the certification portion of the industry is so far out of bounds as to logically be classified as “non-playable,” and certainly should not be cited as any logical justification for making individually preferred decisions by flight crew members.

As stated above, the overall system is safe. How often does an engine failure occur at V1 which happens to e very close to VMCG. Not often. But it is going to happen some day when there is a strong crosswind and at minimum, there will be an excursion, perhaps worse as the crew attempts to do what you and the certification authorities say is the only safe thing to do.

Think of all the expensive hoops that the certification authorities make companies do to get certain things done. Try getting an EFB installation approved. They even do decompression tests on the darn things. Yet, everyday, hundreds of airliners are taking off in strong crosswinds and exposed to what is in fact a significantly higher VMCG than what their performance figures tell them. Why don't the authorities just mandate a higher V1 based on the crosswind component? It would just be another entry on the newly updated OPT or paper graph chart to get new V-speeds based on some engineering analysis. I believe engineering analysis based on technical information from actual tests done in the '60's is all that is done for slippery runway numbers. While that is not certified information but it proves that it can be done. But maybe this would frequenly cut into payload and cost the industry money which might be a cavalier attitude.

AirRabbit

9th Jun 2014, 03:56

JammedStab:

It seems to me that your real concern is the problems that may be caused by some crosswind value that you believe will negate any of the otherwise computed speeds that are typically used for takeoff performance. I know that I could cite several regulatory requirements, but that is almost too much work. My suggestion, should I be so bold, would be to check either the AFM or, to be sure that you have the most appropriate information, I’d check the airplane manufacturer’s published table for maximum wind limits for takeoff and landing. I’ve done that for the B-737. This table includes reference for runway contamination in terms of braking action. Actually, for Boeing equipment you can check “on-line” under the “technical site” for the specific airplane. Here is what that table says for the B-737:

Wind Limits for T/O & Landing
Braking Action vs. Maximum Crosswind limit
Good = 35kt
Medium good = 30kt
Medium = 25kt
Medium poor = 20kt
Poor = 15kt

One of the easier plans I might suggest would be to refuse to takeoff if the crosswind reported (or computed by you at the end of the runway) exceeds the appropriate value. The fact that these numbers are listed in the manufacturer’s “limitation” section should provide sufficient reasoning should any “non-aviator” want to criticize any “no go” decision based on these numbers. Regardless, with the information provided here, I think you might feel a bit better in making whatever decision you make with respect to taking off with some level of crosswind.

JammedStab

10th Jun 2014, 14:37

Well then, I guess the safest course of action will be to always continue if an engine fails at V1 in a strong crosswind a the certificating authorities have taken that into consideration.

Wouldn't you agree John T.

FE Hoppy

10th Jun 2014, 16:36

Cheeky ;-)

After I left the mob one of my old Tristar mates sent me an email asking why we(civilian operators) could carry more out of a dusty place than they could despite using the same equipment.

A quick check of the certification standard used to calculate VMCG revealed all. Good job we never lost a donk at V1 given the average x-wind.

AirRabbit

10th Jun 2014, 22:11

JammedStab:

I’ll attempt to make my point one additional time. Of course you know that you are free to take what I say and check it’s validity, believe it, not believe it, or refuse to read any of my subsequent posts – or virtually any other course of action you choose.

It should be obvious to any pilot having a commercial or higher grade certificate that the amount of control provided by aerodynamic controls alone to maintain directional control during the takeoff is going to be dramatically insufficient initially and will become more sufficient as airspeed is increased. In fact, there is point at which such aerodynamic controls will become sufficient so as to be able to provide directional control without having to depend on the nose wheel control to assist in controlling direction. This airspeed, the minimum airspeed at which directional control can be maintained through aerodynamic controls ALONE (no longer needing nose wheel steering) while still on the ground, is called the minimum aerodynamic control airspeed on the ground. The accepted term for this is called the velocity - minimum control ground, or Vmcg.

Most airplanes with multiple engines do not provide forward thrust along a centerline (and we can discuss/argue what is and what is not actually “centerline” at a later point, if required) and, as such, logically, should a multi-engine airplane experience the loss of an engine during takeoff, the continued control of the direction in which the airplane is traveling toward the takeoff point will be affected. The directionality of an airplane during the initial application of power for takeoff is controlled by the pilot by controlling the position of the nosewheel, and is dependent on retaining sufficient weight on that nose wheel to prevent nose wheel “scuffing” and sufficient nose wheel movement - affected by either rudder pedal or "tiller" input. The force with which the nose wheel is held onto the runway surface can be supported by a forward control column position as soon as aerodynamic effect on the elevator(s) is achieved, and will assist in assuring that nose wheel will maintain sufficient contact with the runway surface to resist any tendency - through wind or thrust asymmetry – to deviate from the intended ground track during the takeoff roll. Should the airplane experience the loss of an engine very early in the takeoff, resulting in an asymmetrical thrust situation … and the pilot decides to reject the takeoff, that pilot can immediately correct any asymmetrical thrust problem by pulling all throttles to idle. Having virtually zero thrust on all engines prevents an asymmetrical thrust situation – and doing so would allow the pilot to continue to maintain directionality with nose wheel steering inputs. Obviously, there is a point during the takeoff acceleration where deciding to reject the takeoff may result in a runway “over-run” at the departure end. This is the reason that instructions are given to the pilots to designate a speed at which they should no longer attempt to reject the takeoff (where deciding to continue the takeoff is considered to be more safe than attempting to reject the takeoff ) and allowing the crew to then deal with the problem once safely airborne.

V1 may not be less than speed at the point the critical engine fails (Vcef) PLUS the speed gained during the time interval between the instant 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. Also, Vcef may not be less than Vmcg, where Vmcg, is defined as the minimum control speed on the ground, with one engine inoperative (the critical engine on two engine airplanes), takeoff power on other engine(s), using aerodynamic controls only for directional control.

Also, according to the regulations, Vmcg, the minimum control speed on the ground, is the calibrated airspeed during the takeoff run at which, when the critical engine is suddenly made inoperative, it is possible to maintain control of the airplane using the rudder control alone (without the use of nosewheel steering), as limited by 150 pounds of force, and the lateral control to the extent of keeping the wings level to enable the takeoff to be safely continued using normal piloting skill. In the determination of Vmcg, assuming that the path of the airplane accelerating with all engines operating is along the centerline of the runway, its path from the point at which the critical engine is made inoperative to the point at which recovery to a direction parallel to the centerline is completed may not deviate more than 30 feet laterally from the centerline at any point. Vmcg must be established with (1) The airplane in each takeoff configuration or, at the option of the applicant, in the most critical takeoff configuration; (2) Maximum available takeoff power or thrust on the operating engines; (3) The most unfavorable center of gravity; (4) The airplane trimmed for takeoff; and (5) The most unfavorable weight in the range of takeoff weights.

There are also limitations on taking of and/or landing with crosswind conditions – providing limitations for the maximum crosswind limits. As I indicated in an earlier post, most manufacturers provide several, graduated maximum crosswind limits, based on the level of contamination of the runway surface, as described in terms of universally understood braking action (see my earlier post in this thread).

john_tullamarine

10th Jun 2014, 22:33

I guess the safest course of action will be to always continue if an engine fails at V1 in a strong crosswind a the certificating authorities have taken that into consideration.

We are at risk, chaps, of ending up in a willy waving competition, methinks .... and that would be a great pity.

(a) life and aeroplanes is about risk, not absolute guarantees

(b) the certification standards match an aeroplane design to a wide-ranging set of parameters which, at the time the Design Standard was frozen for the particular certification, were considered to provide for an adequate level of safety (ie reasonable minimisation of risk) based on reasonable statistical considerations

(c) if you are operating at the extreme limits of the acceptable envelope, one needs to be very considerate of the background which went into the certification approval.

(d) if, as we appear to be, considering Vmcg -

(i) the figure is a boundary condition line in the sand for other considerations and, as it turns out, only looks at a low (or nil for the older UK Standards) crosswind situation

(ii) if you find yourself

- committed to a Vmcg-limiting takeoff (not a general circumstance in the overall scheme of things), AND
- you have a critical failure, AND
- the crosswind is significantly above the certification requirement AND
- that crosswind is from the unfortunate side of the aircraft ...

it just wasn't your day. Perhaps one ought not to have put oneself in the situation unless there were no sensible alternative(s) ... ?

You may well be in the situation of having to reject from a speed above V1 - the possible/probable alternative option being to have a tiptoe through the tulips event .. or worse.

No guarantees, chaps, only probabilities and a modicum of pilot commonsense ...

Now, what might the thinking pilot do to minimise this already minimalistic likelihood of disaster ?

For instance if the conditions are super critical - very short runway, min weight, min V1, strong crosswind, wet conditions, aft CG, etc -

(a) are you able to defer the takeoff until a later, more suitable time ?

(b) is there an alternative runway which might not be so critical ?

(c) is derated thrust an available and workable option ? What is the ASDA/TODA balance for the particular runway ?

If, however, you must go (and that's a part of the command decision process), one should have mentally rehearsed the possible need for a post-V1 reject.

Personally, I'd be far more worried about the idiot in the other car on the drive to the airport .....

de facto

10th Jun 2014, 23:30

Air Rabbit,
I’m not sure if you agree with me or with those who advocate selecting an arbitrary V1 speed…” – I wasn’t able to determine the “reasoning” with which you were definitively not in agreement.
I agreed with you.
and by “IT” I was, and remain, under the impression you were describing the selection of a V1 that was less than the V1 speed described in the regulations
Nope.
- and, with some hesitancy, I understand that there may be some newly developed and distributed software that yields a “range” of V1 speeds
It is my understanding,hence my initial post concerning boeing sentence taken from their engineering doc stating:
• Statistical evidence from RTO accidents and incidents
might lead us to consider a Reduced V1 Policy
Please google : range of V1 performance boeing engineer operations course.
It comes as second result..

JammedStab

11th Jun 2014, 00:12

There are also limitations on taking of and/or landing with crosswind conditions – providing limitations for the maximum crosswind limits. As I indicated in an earlier post, most manufacturers provide several, graduated maximum crosswind limits, based on the level of contamination of the runway surface, as described in terms of universally understood braking action (see my earlier post in this thread).

This information is for an all engines operating scenario and has nothing to do with an engine failure scenario which does not consider crosswinds or contamination in terms of directional control. Ask any airliner test pilot if the maximum demonstrated crosswind component published numbers were considered with an engine failure during the takeoff roll.

if, as we appear to be, considering Vmcg -

(i) the figure is a boundary condition line in the sand for other considerations and, as it turns out, only looks at a low (or nil for the older UK Standards) crosswind situation

(ii) if you find yourself

- committed to a Vmcg-limiting takeoff (not a general circumstance in the overall scheme of things), AND
- you have a critical failure, AND
- the crosswind is significantly above the certification requirement AND
- that crosswind is from the unfortunate side of the aircraft ...

it just wasn't your day. Perhaps one ought not to have put oneself in the situation unless there were no sensible alternative(s) ... ?

You may well be in the situation of having to reject from a speed above V1 - the possible/probable alternative option being to have a tiptoe through the tulips event .. or worse.

No guarantees, chaps, only probabilities and a modicum of pilot commonsense ...

Now, what might the thinking pilot do to minimise this already minimalistic likelihood of disaster ?

For instance if the conditions are super critical - very short runway, min weight, min V1, strong crosswind, wet conditions, aft CG, etc -

(a) are you able to defer the takeoff until a later, more suitable time ?

(b) is there an alternative runway which might not be so critical ?

(c) is derated thrust an available and workable option ? What is the ASDA/TODA balance for the particular runway ?

Thank you for the information.

If, however, you must go (and that's a part of the command decision process), one should have mentally rehearsed the possible need for a post-V1 reject.

Thanks John,

This IS the point that I have trying to get across which flies in the face of the idea that it is always safest to continue and always less safe to reject after V1.

Based on today's reliable engines, the exact situation is unlikely to happen, but does the setup happen frequently? How many airliners will takeoff with a strong crosswind today.

I'm only trying to provide some more information that many(as we can see) have not considered.

john_tullamarine

11th Jun 2014, 00:43

This information ... has nothing to do with an engine failure scenario which does not consider crosswinds or contamination in terms of directional control.

Are you sure of that ? Perhaps you can cite appropriate references to support the contention ?

it is always safest to continue and always less safe to reject after V1.

Almost always the case and, by far, the preferred habituation for crews on a simple risk management basis.

However, not if, for whatever reason, control is lost or there is some other circumstance which precludes a sensibly safe continued takeoff.

The commander should consider such events as part of his general development and preflight considerations

How many airliners will takeoff with a strong crosswind today.

Many will of course.

However, the Vmcg concern with crosswind generally is not a problem in routine line operations. It presents in very limited circumstances and only for a quite small range of speed in excess of Vmcg - the centreline deviation characteristic curve rapidly moves out of the problem area .. which is why we don't fuss too much about the topic in routine operations ..

aterpster

11th Jun 2014, 01:00

J.T:

Personally, I'd be far more worried about the idiot in the other car on the drive to the airport .....

Yes sir!!

That was always the biggest risk factor of driving some 65 miles across the wild lands of the greater Los Angeles area as opposed to any risk that could, or would, occur once safely on the airline property.

I would qualify that somewhat, though, with layover taxis or hotel vans. :)

john_tullamarine

11th Jun 2014, 03:16

with layover taxis or hotel vans

.. or layovers generally. Hopefully all the players concerned have suffered severe and debilitating specific amnesia in respect of such matters ...

CL300

11th Jun 2014, 06:24

John and Air Rabbit are spot on and correct; like in all segments of life there is some educated people; who learned the ins and outs of all the problematics; well outside the box of REQUIRED knowledge.

And this is where the problem lies within this discussion. For most of the pilots being trained , there is only one V1, the one given on that take off, on that day on that condition, for a balanced field condition, most of the time; and FMC/performance programs etc are giving this exact number with more or less 100% accuracy ( if the data are entered correctly by the crew). BUT, and there is a BUT. This specific V1 presented was chosen from the performance charts by the operator from the manufacturer after certification; this process is totally opaque for nearly 100% of the crews flying the plane, they just have to stick to the said numbers, the rest is the test pilot world and has NOTHING to compare to a day to day ops.

For the rest, and no contest here, since it is not the same league at all; please speak among yourselves at the bar, bitching on whoever you want, ppruners, Chief Pilot, other idiots in the field; but just do you job : STICK TO THE MANUAL, and FLY the NUMBERS!! This is what you are paid for...( Hopefully)

JammedStab

11th Jun 2014, 06:51

However, the Vmcg concern with crosswind generally is not a problem in routine line operations. It presents in very limited circumstances and only for a quite small range of speed in excess of Vmcg - the centreline deviation characteristic curve rapidly moves out of the problem area .. which is why we don't fuss too much about the topic in routine operations .

Thanks. I guess it would take engineering information and analysis to know how much of a range in excess of the published Vmcg that this would extend. Something that would be very interesting to see.

This information ... has nothing to do with an engine failure scenario which does not consider crosswinds or contamination in terms of directional control.

Are you sure of that ? Perhaps you can cite appropriate references to support the contention ?

The only thing I can find is FAA AC25-7B FLIGHT TEST GUIDE FOR CERTIFICATION OF TRANSPORT CATEGORY AIRPLANES. In the explanation below, no mention is made about an engine inoperative scenario.

Section 7. Ground Handling Characteristics

(a) Landplanes.
1 There must be a 90-degree crosswind component established that is
shown to be safe for takeoff and landing on dry runways.
2 The airplane must exhibit satisfactory controllability and handling
characteristics in 90-degree crosswinds at any ground speed at which the airplane is expected to
operate.
(c) Crosswind Demonstration. A 90-degree crosswind component at 10 meters
(as required by § 25.21(f)) of at least 20 knots or 0.2 VSR0 (where VSR0 is for the maximum
design landing weight), whichever is greater, except that it need not exceed 25 knots, must be
demonstrated during type certification tests. There are two results possible:
1 A crosswind component value may be established that meets the
minimum requirements but is not considered to be a limiting value for airplane handling characteristics. This “demonstrated” value should be included as information in the AFM.
2 A crosswind component value may be established that is considered to be
a maximum limiting value up to which it is safe to operate for takeoff and landing. This “limiting” value should be shown in the operating limitations section of the AFM.
(2) Procedures.
(a) Configuration. These tests should be conducted in the following
configurations:
1 At light weight and aft c.g. (This is desirable; however, flexibility should
be permitted.)
2 Normal takeoff and landing flap configurations using the recommended
procedures.
3 Normal usage of thrust reversers. Particular attention should be paid to
any degradation of rudder effectiveness due to thrust reverser airflow effects.
4 Yaw dampers/turn coordinator On, or Off, whichever is applicable.
(b) Test Procedure and Data. Three takeoffs and three landings, with at least one landing to a full stop, should be conducted in a 90-degree crosswind component of at least 20 knots or 0.2 VSR0, whichever is greater, except that for airplanes whose certification basis includes amendment 25-42, it need not exceed 25 knots. For each test condition, a qualitative
evaluation by the pilot of airplane control capability, forces, airplane dynamic reaction in gusty crosswinds (if available), and general handling characteristics should be conducted. The airplane should be satisfactorily controllable without requiring exceptional piloting skill or strength. Wind data from an inertial navigation system (INS), tower, or portable ground
recording station should be corrected to a 90-degree crosswind component and to a height of 10 meters.

For my aircraft, the AFM states "M A X I M U M C R O S S W I N D
The maximum crosswind component for takeoff and landing is 30 knots
reported wind at a 10-meter (32.8-foot) height. This component is
not considered to be limiting on a dry runway with all engines
operating."

CL300

11th Jun 2014, 10:13

LFMAO

11th Jun 2014 06:51
JammedStab

For my aircraft, the AFM states "M A X I M U M C R O S S W I N D
The maximum crosswind component for takeoff and landing is 30 knots
reported wind at a 10-meter (32.8-foot) height. This component is
not considered to be limiting on a dry runway with all engines
operating."
Last edited by john_tullamarine; 11th Jun 2014 at 08:24. Reason: Wind Velocities -§ 25.237.

For interest, my edit was solely to replace the underlining with italics for readability. JT

I love forums....

I did not realized that you were admin on this thread, sorry mate...That looked awkward at first glance ..apologies....You are completely right..

john_tullamarine

11th Jun 2014, 10:14

engineering information and analysis to know how much of a range in excess of the published Vmcg that this would extend

Can only speak to those few test programs where I have had some involvement with Vmcg related exercises.

A principal measure, post failure, is the tracking deviation from centreline. As the speed reduces from the normal sort of routine speeds one uses, the deviation tends to be relatively stable until one gets near to Vmcg when it starts to increase. In the last few knots, and my observations put this in the 5 kt or so range, the deviation diverges quite rapidly to the point where it is outside the required measure.

Obviously, there may be variation with different Types but I imagine that my observations will not be too far away from the norm.

In the explanation below, no mention is made about an engine inoperative scenario.

Like a lot of certification stuff, one needs to read a bit between the lines for intent and, as you have done, refer to the ACs to find out what the FAA might have thought was relevant. One needs to keep in mind that the bulk of certification performance work relates to OEI rather than AEO.

Such items such as the following offer some insight -

(a) No takeoff made to determine the data required by this section may require exceptional piloting skill or alertness

(b) There may be no uncontrollable ground-looping tendency in 90-degree crosswinds, up to a wind velocity of 20 knots or 0.2 VSR0

(c) There must be a 90-degree crosswind component established that is shown to be safe for takeoff and landing on dry runways

(d) The airplane must exhibit satisfactory controllability and handling characteristics in 90-degree crosswinds at any ground speed at which the airplane is expected to operate.

(e) The applicant should demonstrate that exceptional skill is not required to maintain directional control on a wet runway with a ten-knot crosswind from the most adverse direction. For demonstration purposes, a wet runway may be simulated by using a nose wheel free to caster on a dry runway. Symmetric braking should be used during the demonstration, and both all-engines-operating and critical-engine-inoperative reverse thrust should be considered.

If your concern lies with a thought that the OEI case doesn't consider cross wind components, the above requirements would scarcely be satisfied ?

(I took the liberty of editing your post to replace the underlined text with italics .. I was getting a headache trying to read it)

JammedStab

11th Jun 2014, 23:00

John and Air Rabbit are spot on and correct; like in all segments of life there is some educated people; who learned the ins and outs of all the problematics; well outside the box of REQUIRED knowledge.

STICK TO THE MANUAL, and FLY the NUMBERS!! This is what you are paid for...( Hopefully)

Actually, I think that all transport pilots should be made aware of this potential serious controllability issue.

I have provided a link to a British Airtours crash many years back where this issue was discussed by the AAIB. On a 707 training flight during takeoff in a crosswind, the instructor closed the thrust lever of an engine at a critical moment. While there were other issues that led to the crash, the company policy of Engine out training in crosswinds was discussed.

http://www.aaib.gov.uk/cms_resources.cfm?file=/6-1978%20G-APFK.pdf

I have deleted some text from the quote to save typing as I could not copy and paste. Therefore this is not a completely direct quote below but I did put it in italics.

It states that For UK certification, Vmcg is established with a 7 knot crosswind component from the adverse side, the 'trade' for higher value varies considerably between types. A good conservative rule of thumb is to add 1.3 knots to Vmcg for every one knot of crosswind above 7 knots up to a maximum component of 15 knots around maximum landing weight. Further extrapolation is not advised because the greatly increased V1 will then be incompatible with the VR and V2 speeds. The 15 knot limit would 'lift'(increase) Vmcg by 11 knots for a Boeing 707.

Think about what they are saying. For every 1 knot of crosswind above the certified certified amount of crosswind that the aircraft had its Vmcg established(which is zero for most aircraft we fly), add 1.3 knots to Vmcg(each aircraft is different and aircraft weight is a factor as well) This value of 1.3 knots is what the CAA calls conservative but it makes the point. And even if for your own aircraft it is 30% less, this is still a 1 knot increase in VMCG for every knot of crosswind.

For the 707 under the conditions calculated by the CAA(near max landing weight), the Vmcg increased by 11 knots for what would be the equivalent of a 15 knot crosswind(23 knots in this case) for most certified airliners because Vmcg was determined with no crosswind for most airliners.

The CAA also does not go beyond, in this case 23 knots of crosswind(7 knot for certification in the UK plus 15 knots crosswind in addition), because as they state, Vmcg will be above Vr. Something to think about in your next strong crosswind takeoff. At Vr, you may be below your VMCG even if Vr is quite a bit above V1. And there is no real way of figuring out the particular details for your aircraft.

john_tullamarine

12th Jun 2014, 02:24

This is a pet concern of most of us who are both pilots and ops engineers. I refer those interested to a search on the Vmcg topic across PPRuNe .. plenty of discussions.

However, one ought not to be unduly pessimistic about life, death and the universe in respect of Vmcg - for most considerations it is a boundary condition for other performance items.

As to Rules of Thumb -

(a) for twins (based on such formal OEM data as I have obtained) Vmcg should increase with crosswind at around 0.5kt/kt (specifically for rear fuse mounted engines but, probably, not too far off the mark for twins in general - alternatively pad towards the quad figure)

(b) for quads probably in the order of 1kt/kt or slightly more.

Main point is that book Vmcg is at the extreme low end of the routine operating scale so the small region where one might be exposed due to an increased crosswind is not visited much in routine operations. Add to this the observation that the situation and aircraft configuration probably will be less critical than for the book figure and one can be a little more comfortable.

Certainly one could take the view that the combination of a Vmcg limiting takeoff with a failure and in strong crosswinds is a rare event. In any case, it can be mitigated simply by the commander's saying "no way, Jose, we'll have a cup of coffee and wait for better conditions".

Vmcg and crosswind is a problem for very light takeoffs from very short runways without any clearway to play with. Most of the time this doesn't apply.

Where you have a bit more runway to play with, the easiest way to mitigate the risk is to schedule the speeds for a higher weight within the range permissible for the runway.

At Vr, you may be below your VMCG even if Vr is quite a bit above V1.

But only for a restricted region of the envelope as mentioned above in reasonably strong crosswinds with the "wrong side" failing. In general, this isn't a problem at all.

And there is no real way of figuring out the particular details for your aircraft.

The rules of thumb above are useful in the real world.

Bergerie1

12th Jun 2014, 03:50

JammedStab
Sorry to be pedantic but it was being operated by British Airtours, an off-shoot of BEA. It was not BOAC!
Rather like the subjects being discussed on the thread on simulator training in cross-winds, it is essential for instructors to understand their machine's limitations. On that thread it is the limitations of the simulator as well as those of the aircraft. In this accident at Prestwick the instructor did not understand the certification standard for VCMG in a crosswind.

JammedStab

12th Jun 2014, 05:48

Air carrier name changed.

Thanks for the replies. At this time, I appreciate the responses.

JammedStab

13th Jun 2014, 13:29

Another European CAA has recognized the danger of assuming that V1 in a crosswind guarantees a safe outcome if a properly flown continuation of flight is performed with an engine failure at V1.

While air carrier commercial operations may have a small likelihood of this being an issue due to the good fortune of engine reliability, it appears to be a higher risk in the training environment.

http://www.transport.gov.mt/admin/uploads/files/1_OSC%20Circular%20no%2002_02.pdf

4. Performance Considerations
4.1 Training Captains must only simulate engine failure on take-off in crosswind conditions when they are certain that the speed at which the simulated failure is initiated will, in the prevailing conditions, allow an adequate margin of control.
4.1.1 Certifications under JAR-25 make no allowance for crosswind components in the calculation of VMCG. As general guidance, therefore, Training Captains in aeroplanes so certificated should not simulate engine failure below thegreater of:

(a) VI
and
(b) VMCG incremented by 1 kt per kt of crosswind component (to a maximum of 10 kt).

If (b) is the greater value, VI should not be increased but the engine failure
initiated at the appropriate speed above VI.
4.1.2 The advice of manufacturers’ training departments should be sought before engine failures are simulated in crosswind components greater than 10 kt, and in any case engine failures should never be simulated in crosswind components exceeding 15 kt, or on slippery or contaminated runways. Crosswind conditions make it difficult to monitor the trainee’s rudder input and to correct any degree of wrong or inadequate movement.