What is optimum v1 and improved v1

[de facto]

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...

[JammedStab]

Originally Posted by AirRabbit

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.

Originally Posted by AirRabbit

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]

Originally Posted by JammedStab

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.

Originally Posted by JammedStab

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]

Originally Posted by AirRabbit

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.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/Wiringcargodoorl...es/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

Originally Posted by AirRabbit

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]

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.

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.

[AirRabbit]

Originally Posted by de facto

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 …

Originally Posted by de facto

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]

Originally Posted by AirRabbit

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-boe...-certification (strongly suggested reading).

Originally Posted by AirRabbit

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]

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]

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]

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]

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]

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]

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]

Originally Posted by AirRabbit

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.

Originally Posted by john_tullamarine

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.

Originally Posted by john_tullamarine

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]

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]

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]

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]

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]

Originally Posted by john_tullamarine

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.

Originally Posted by john_tullamarine

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]

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..