Cross Wind T/O and Landings
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you can't quit flying the thing the moment the wheels touch! (actually it was the dastardly fbw, not the pilot that decided to halve the aileron inputs on touchdown - oh how glad I am I don't fly these things)!
https
and the monarch (second clip) demonstrates what happens on rotation in a cross wind with no aileron applied
Linking the second video to the second, does the FBW suddenly double the aileron input when the wheels leave the ground on rotation? If so, I can understand that great caution would be required for the amount of roll input during rotation on the Airbus
https
Last edited by midnight cruiser; 29th Aug 2018 at 19:29.
Rough old day.
The landing at 09.45 into the 2nd clip I thought was a very good effort indeed. Maybe lucky between the gusts? That P/F had control of the thing and nailed the C/L through out. Very rare these days, a cross wind landing like that.
Some of those touch downs, the P's/F were extremely lucky they weren't trying that in a B707 for e.g., as they would not have got away with it. Not their faults as obviously they haven't been trained to do the job correctly in those conditions. Attempting to touch down, without any attempt to decrab and with the down wind wing down, is just not acceptable. Begs the question as to the standard of the check and training at these outfits.
Full marks to the people who went missed. Nothing wrong with that.
The landing at 09.45 into the 2nd clip I thought was a very good effort indeed. Maybe lucky between the gusts? That P/F had control of the thing and nailed the C/L through out. Very rare these days, a cross wind landing like that.
Some of those touch downs, the P's/F were extremely lucky they weren't trying that in a B707 for e.g., as they would not have got away with it. Not their faults as obviously they haven't been trained to do the job correctly in those conditions. Attempting to touch down, without any attempt to decrab and with the down wind wing down, is just not acceptable. Begs the question as to the standard of the check and training at these outfits.
Full marks to the people who went missed. Nothing wrong with that.
Last edited by Dan_Brown; 29th Aug 2018 at 21:02.
Folks,
All very interesting.
Those of us who "fly the aeroplane" do exactly that, and clearly at least the Boeing manual referred to does NOT say no aileron. Indeed, those B737 words sound very familiar to me.
Anybody who doesn't understand why a crosswind component effects Vmcg is not, I hope, flying real aeroplanes.
Going right back the B707, Boeing had a "menu" of takeoff data for the customer, who could, within the minimum certification standards for their national authority, choose what conditions reduced the performance on takeoff.
One was drag from spoiler rise, when using enough aileron to keep the wings level.
Another was blanketing of the downwind wing in a strong crosswind.
And, of course, the Vmcg implications of a crosswind, and its possible limitation on calculating a Vmcg limited V1.
And so it went on, and the choice of airline operational managements was "interesting', unless imposed by regulation, few included anything in takeoff calculations that would reduce the payload. Delving into detailed performance certification can be fascinating, if you are that way incline.
Whether you are or not, read the AFM/FCTM VERY carefully, read what it actually says, and not what somebody else tells you it says.
Tootle pip!!
All very interesting.
Those of us who "fly the aeroplane" do exactly that, and clearly at least the Boeing manual referred to does NOT say no aileron. Indeed, those B737 words sound very familiar to me.
Anybody who doesn't understand why a crosswind component effects Vmcg is not, I hope, flying real aeroplanes.
Going right back the B707, Boeing had a "menu" of takeoff data for the customer, who could, within the minimum certification standards for their national authority, choose what conditions reduced the performance on takeoff.
One was drag from spoiler rise, when using enough aileron to keep the wings level.
Another was blanketing of the downwind wing in a strong crosswind.
And, of course, the Vmcg implications of a crosswind, and its possible limitation on calculating a Vmcg limited V1.
And so it went on, and the choice of airline operational managements was "interesting', unless imposed by regulation, few included anything in takeoff calculations that would reduce the payload. Delving into detailed performance certification can be fascinating, if you are that way incline.
Whether you are or not, read the AFM/FCTM VERY carefully, read what it actually says, and not what somebody else tells you it says.
Tootle pip!!
Vmcg is a certification speed, established by flight test demonstration, showing (usually) a specified maximum lateral deviation from the runway centreline, or projected ground track at the time of engine failure.
It could be said that if conditions specified for determination of Vmcg are not present then the speed is not Vmcg.
It is a speed to help in scheduling takeoff performance, it makes no claims as far as handling characteristics during crosswind takeoffs at crosswinds beyond those used for Vmcg determination.
Handling qualities during takeoff at maximum crosswind is a different problem to Vmcg.
This was (is??) at least partly addressed by the Oz regulatory authority, in some cases, to ensure, by flight test, that aircraft would not deviate past the runway edge following an engine failure at maximum crosswind.
Of course crosswind does not have any effect on Vmcg.
Vmcg is a certification speed, established by flight test demonstration, showing (usually) a specified maximum lateral deviation from the runway centreline, or projected ground track at the time of engine failure.
It could be said that if conditions specified for determination of Vmcg are not present then the speed is not Vmcg.
It is a speed to help in scheduling takeoff performance, it makes no claims as far as handling characteristics during crosswind takeoffs at crosswinds beyond those used for Vmcg determination.
Handling qualities during takeoff at maximum crosswind is a different problem to Vmcg.
This was (is??) at least partly addressed by the Oz regulatory authority, in some cases, to ensure, by flight test, that aircraft would not deviate past the runway edge following an engine failure at maximum crosswind.
Vmcg is a certification speed, established by flight test demonstration, showing (usually) a specified maximum lateral deviation from the runway centreline, or projected ground track at the time of engine failure.
It could be said that if conditions specified for determination of Vmcg are not present then the speed is not Vmcg.
It is a speed to help in scheduling takeoff performance, it makes no claims as far as handling characteristics during crosswind takeoffs at crosswinds beyond those used for Vmcg determination.
Handling qualities during takeoff at maximum crosswind is a different problem to Vmcg.
This was (is??) at least partly addressed by the Oz regulatory authority, in some cases, to ensure, by flight test, that aircraft would not deviate past the runway edge following an engine failure at maximum crosswind.
I hope you are not actually a pilot, you clearly know very little about Vmcg certification, and what you do know is in error.
Could I gently suggest you do a bit of homework on the subject, even the different requirements either side of the Atlantic at different periods.
Your last line is particularly interesting, as Australia (thank goodness) has not had its own unique airworthiness requirements since 1998, where the last of the ratbag local impositions were buried in an unmarked grave, and as for Vmcg speeds, have been as per FAA since a long time ago --- as opposed to those who wanted to impose BCAR methods.
I can tell you from actual experience, in a B747-238, with only a 25 kt. X-wind, and a full de-rated takeoff, the "wrong" engine losing thrust at a Vmcg limited V1 resulted in demolishing some runway lights.
Tootle pip!!
PS: The details of how a particular type an variant is certified (FAA) will be found in the flight test guide that FAA and the manufacturer settle as part of the certification process. Tracking the history of certified approach Vref speeds is a good case in point, it has been a long, long time since Boeing used 1.3Vs as the basis for Vref.
Last edited by LeadSled; 4th Sep 2018 at 02:32. Reason: PS added
zzuf,
I hope you are not actually a pilot, you clearly know very little about Vmcg certification, and what you do know is in error.
Could I gently suggest you do a bit of homework on the subject, even the different requirements either side of the Atlantic at different periods.
Your last line is particularly interesting, as Australia (thank goodness) has not had its own unique airworthiness requirements since 1998, where the last of the ratbag local impositions were buried in an unmarked grave, and as for Vmcg speeds, have been as per FAA since a long time ago --- as opposed to those who wanted to impose BCAR methods.
I can tell you from actual experience, in a B747-238, with only a 25 kt. X-wind, and a full de-rated takeoff, the "wrong" engine losing thrust at a Vmcg limited V1 resulted in demolishing some runway lights.
Tootle pip!!
PS: The details of how a particular type an variant is certified (FAA) will be found in the flight test guide that FAA and the manufacturer settle as part of the certification process. Tracking the history of certified approach Vref speeds is a good case in point, it has been a long, long time since Boeing used 1.3Vs as the basis for Vref.
I hope you are not actually a pilot, you clearly know very little about Vmcg certification, and what you do know is in error.
Could I gently suggest you do a bit of homework on the subject, even the different requirements either side of the Atlantic at different periods.
Your last line is particularly interesting, as Australia (thank goodness) has not had its own unique airworthiness requirements since 1998, where the last of the ratbag local impositions were buried in an unmarked grave, and as for Vmcg speeds, have been as per FAA since a long time ago --- as opposed to those who wanted to impose BCAR methods.
I can tell you from actual experience, in a B747-238, with only a 25 kt. X-wind, and a full de-rated takeoff, the "wrong" engine losing thrust at a Vmcg limited V1 resulted in demolishing some runway lights.
Tootle pip!!
PS: The details of how a particular type an variant is certified (FAA) will be found in the flight test guide that FAA and the manufacturer settle as part of the certification process. Tracking the history of certified approach Vref speeds is a good case in point, it has been a long, long time since Boeing used 1.3Vs as the basis for Vref.
The history of changes to Vref is not that exciting, suggest you follow up on why Vsmin, was finally replaced by Vs1g, not that is of any relevance to this thread.
For Crosswind takeoff:
Exactly at Vlof you will be side slipping, then if you neutralize the flight controls immediately, you will track the runway in a proper crab
Exactly at Vlof you will be side slipping, then if you neutralize the flight controls immediately, you will track the runway in a proper crab
Moderator
zzuf, I hope you are not actually a pilot ..
Now, I have known zzuf for, probably, near on 40 years. Might I suggest that the good LS discontinue the line of argument lest you, surely, lose, as lose you will if the discussion revolves around certification. As to whether zzuf can fly, as I recall, I have only ever flown with him once .. and I got out of the aircraft, shall we say, green with envy .. now, why couldn't I fly half that well and that on one of my best days ? For interest, he had never flown the particular aircraft Type previously, it was a mongrel of a day .. and he flew it like it was on rails out on a nice nil wind morning at dawn with a big high sitting over the place ... I think he qualifies as a more than passable stick and rudder chap.
Of course crosswind does not have any effect on Vmcg.
Zzuf is, naturally, absolutely correct. However, he is talking about the certification animal and it, quite correctly, has no interest in the wind on the day.
Anybody who doesn't understand why a crosswind component effects Vmcg is not, I hope, flying real aeroplanes.
Leaddie, on the other hand, is talking about handling problems on the day when the wind might be whatever .. and Vmcg, as she is wrote in the book, might not be all that relevant to the pilot's immediate problems if the speed schedule is on the minimum .... in such conditions, with an unfavourable and strong crosswind, the pilot might well find himself below the speed at which he can control the aircraft directionally. One circumstance in which the aircraft operation might well be perfectly "legal" but the bird heads off into the weeds regardless of what the pilot might be doing .. unless the pilot be sufficiently astute to recognise that the takeoff needs to be rejected albeit above V1.
For interest, the following rules of thumb are probably not far from the mark -
(a) for a twin, be prepared for the defacto-real-world-"Vmcg"-on-the-day to increase by around half a knot per knot of crosswind, or more. This is based on OEM data for one particular twin jet (with which zzuf was familiar many years ago, as a yellow-coloured example). Note that this has no effect on the certification Vmcg, only the pilot's real world handling problems.
(b) for a quad, probably in the one knot/knot plus region...
Now, I have known zzuf for, probably, near on 40 years. Might I suggest that the good LS discontinue the line of argument lest you, surely, lose, as lose you will if the discussion revolves around certification. As to whether zzuf can fly, as I recall, I have only ever flown with him once .. and I got out of the aircraft, shall we say, green with envy .. now, why couldn't I fly half that well and that on one of my best days ? For interest, he had never flown the particular aircraft Type previously, it was a mongrel of a day .. and he flew it like it was on rails out on a nice nil wind morning at dawn with a big high sitting over the place ... I think he qualifies as a more than passable stick and rudder chap.
Of course crosswind does not have any effect on Vmcg.
Zzuf is, naturally, absolutely correct. However, he is talking about the certification animal and it, quite correctly, has no interest in the wind on the day.
Anybody who doesn't understand why a crosswind component effects Vmcg is not, I hope, flying real aeroplanes.
Leaddie, on the other hand, is talking about handling problems on the day when the wind might be whatever .. and Vmcg, as she is wrote in the book, might not be all that relevant to the pilot's immediate problems if the speed schedule is on the minimum .... in such conditions, with an unfavourable and strong crosswind, the pilot might well find himself below the speed at which he can control the aircraft directionally. One circumstance in which the aircraft operation might well be perfectly "legal" but the bird heads off into the weeds regardless of what the pilot might be doing .. unless the pilot be sufficiently astute to recognise that the takeoff needs to be rejected albeit above V1.
For interest, the following rules of thumb are probably not far from the mark -
(a) for a twin, be prepared for the defacto-real-world-"Vmcg"-on-the-day to increase by around half a knot per knot of crosswind, or more. This is based on OEM data for one particular twin jet (with which zzuf was familiar many years ago, as a yellow-coloured example). Note that this has no effect on the certification Vmcg, only the pilot's real world handling problems.
(b) for a quad, probably in the one knot/knot plus region...
Thankyou zzuf and JT you have been most informative and I have learned a lot from your posts. Its a great thing about Pprune that pilots of significant experience pass on their knowledge to those of us who are willing to receive it.
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Recent addition to our manual, hope it sheds some light,
Recommended crosswind technique during takeoff
At regular intervals we receive questions concerning the correct technique for crosswind takeoffs. Especially the
text concerning “large control wheel inputs” in FCTM 3.12 leaves room for interpretation.
In this Plane Fact we will look into the effect of raised flight spoilers during the takeoff roll and the allowance for
flight spoiler deployment in the takeoff performance calculation. The following information is compiled from
information we received from Boeing.
In FCTM 3.12 guidelines are given for crosswind takeoffs. The following quotes are relevant for the preferred
takeoff technique:
“Throughout the takeoff roll, gradually increase control wheel displacement into the wind only enough to
maintain approximately wings level”
"Large control wheel inputs can have an adverse effect on directional control near V1(MCG) due to the
additional drag of the extended spoilers."
“Note: Excessive control wheel displacement during rotation and liftoff increases spoiler deployment. As
spoiler deployment increases, drag increases and lift is reduced which results in reduced tail clearance, a
longer takeoff roll, and slower airplane acceleration."
Relevant for the understanding of the FCTM text is the fact that drag caused by excessive spoiler deflection can
only be limiting when the takeoff is continued after V1 with an engine failure or a loss of thrust. Excessive
spoiler deflection during a normal two-engine takeoff will lead to reduced tail clearance, a longer takeoff roll
and slower airplane acceleration, but the impact on performance will be negligible compared to a takeoff with
an engine failure.
An engine failure during the takeoff roll will cause extra drag due to required rudder and aileron inputs. Boeing
states it to be impossible to define what "large control wheel input" or "excessive control wheel input" values
are since conditions and speeds will vary. Boeing advises to use enough control wheel input to keep the airplane
on centerline with approximately wings level. Any input beyond that would be considered 'excessive'.
The FCTM technique of using only enough control wheel inputs to maintain wings level will minimize the
performance impact of spoiler deflection during the takeoff roll, and immediately following liftoff. Boeing did a
study of the effect of crosswind on takeoff roll and concluded that the drag effects of extended spoilers on the
upwind wing are offset by the positive effect of the crosswind on the same wing. In other words; the airflow to
the upwind wing is at a higher speed than the actual measured airspeed because the lateral component of the
wind is bigger at the wing. The resulting increase of lift counteracts the effect of the increased drag. As a result
the correct use of control wheel inputs (including flight spoiler deployment) will not have a negative effect on
takeoff performance calculations.
The technique to gradually increase control wheel displacement into the wind only enough to maintain
approximately wings level should not be limited to a certain maximum. Boeing does not recommend setting
limits to control wheel roll inputs on takeoff as crews must be ready to apply as much correction as necessary in
the event of takeoff upset events such as strong gusts or wake turbulence encounters.
The correct application of con
Recommended crosswind technique during takeoff
At regular intervals we receive questions concerning the correct technique for crosswind takeoffs. Especially the
text concerning “large control wheel inputs” in FCTM 3.12 leaves room for interpretation.
In this Plane Fact we will look into the effect of raised flight spoilers during the takeoff roll and the allowance for
flight spoiler deployment in the takeoff performance calculation. The following information is compiled from
information we received from Boeing.
In FCTM 3.12 guidelines are given for crosswind takeoffs. The following quotes are relevant for the preferred
takeoff technique:
“Throughout the takeoff roll, gradually increase control wheel displacement into the wind only enough to
maintain approximately wings level”
"Large control wheel inputs can have an adverse effect on directional control near V1(MCG) due to the
additional drag of the extended spoilers."
“Note: Excessive control wheel displacement during rotation and liftoff increases spoiler deployment. As
spoiler deployment increases, drag increases and lift is reduced which results in reduced tail clearance, a
longer takeoff roll, and slower airplane acceleration."
Relevant for the understanding of the FCTM text is the fact that drag caused by excessive spoiler deflection can
only be limiting when the takeoff is continued after V1 with an engine failure or a loss of thrust. Excessive
spoiler deflection during a normal two-engine takeoff will lead to reduced tail clearance, a longer takeoff roll
and slower airplane acceleration, but the impact on performance will be negligible compared to a takeoff with
an engine failure.
An engine failure during the takeoff roll will cause extra drag due to required rudder and aileron inputs. Boeing
states it to be impossible to define what "large control wheel input" or "excessive control wheel input" values
are since conditions and speeds will vary. Boeing advises to use enough control wheel input to keep the airplane
on centerline with approximately wings level. Any input beyond that would be considered 'excessive'.
The FCTM technique of using only enough control wheel inputs to maintain wings level will minimize the
performance impact of spoiler deflection during the takeoff roll, and immediately following liftoff. Boeing did a
study of the effect of crosswind on takeoff roll and concluded that the drag effects of extended spoilers on the
upwind wing are offset by the positive effect of the crosswind on the same wing. In other words; the airflow to
the upwind wing is at a higher speed than the actual measured airspeed because the lateral component of the
wind is bigger at the wing. The resulting increase of lift counteracts the effect of the increased drag. As a result
the correct use of control wheel inputs (including flight spoiler deployment) will not have a negative effect on
takeoff performance calculations.
The technique to gradually increase control wheel displacement into the wind only enough to maintain
approximately wings level should not be limited to a certain maximum. Boeing does not recommend setting
limits to control wheel roll inputs on takeoff as crews must be ready to apply as much correction as necessary in
the event of takeoff upset events such as strong gusts or wake turbulence encounters.
The correct application of con
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that's not correct. It does not say that - in fact, quite the opposite
Anyway, the manual doesn't tell you to pull the stick to make the houses get smaller, turn the wheel to roll, or push the levers to make engines go faster, but you do it because it's called flying the aeroplane! (difficult for me to speak for Airbus, but I greatly doubt a small roll input would be anything but beneficial). What a sorry state the profession is in if Airbus philosophy has reduced pilots to automatons who are reduced to passengers if their programming (ie manuals) doesn't have an algorithm for the task at hand! (ooh, here's one - how about a stall ..... stick forward - who'd have thunk it)
(You might guess I'm not an Airbus fan)!
Anyway, the manual doesn't tell you to pull the stick to make the houses get smaller, turn the wheel to roll, or push the levers to make engines go faster, but you do it because it's called flying the aeroplane! (difficult for me to speak for Airbus, but I greatly doubt a small roll input would be anything but beneficial). What a sorry state the profession is in if Airbus philosophy has reduced pilots to automatons who are reduced to passengers if their programming (ie manuals) doesn't have an algorithm for the task at hand! (ooh, here's one - how about a stall ..... stick forward - who'd have thunk it)
(You might guess I'm not an Airbus fan)!
JT at al,
With the very greatest of respect, I actually know what I am talking about in these areas --- something that Lookleft is unlikely to accept.
I stated in an earlier post that, to determine how Vmcg (or anything else) for an FAA type and variant was established you have to consult the flight test guide for said type and variant.
This is not the same as a text book definition of Vmcg, as I am certain you would agree.
As to "stories" about special DCA "rules" that said a VH- registered aircraft has a Vmcg that ensured it would stay on the runway in the most adverse crosswinds, I heard that quoted many years ago, but never found any proof. Indeed, I never came across anybody in DCA who would have had the background to conduct such tests, and I have no idea what might have gone on at Moses lake with the B707-138A/B in all its variations.
I never flew the B707-138A/B ( along with the RR powered B707-300 the only significant variants of the B707/720 I haven't flown) so there could have been some sodding around with the numbers there, but the certification of Vmcg for the B707-320B/C with JT3B-3D engines with large blow in fan cowl doors was quoted by Boeing as good to 7kt crosswind,--- straight from the FAA guide and from the mouth of one of the pilots on the flight test program --- and the Limitations (mandatory) section of the manual for a VH-registered aircraft was the same as an N-registered aircraft.
The same was (mostly) not true if it was a G-registered aircraft.
Likewise, most of the V speeds for a G registered aircraft differed from the US/AU Limitations speeds. Again, thank that opinionated and short tempered little Welshman -- who did sign my first flight test approval, although, I might add, not Experimental Flight Test, just "post production/maintenance".
"Back in the day", at YMML on a cold and wet and windy (from the WSW) we used to see the "safety advantages" of applying a crosswind component to the Vmcg, when you had a Vmcg limited V1.
I would be able to use RW 27, with a bit of a crosswind.
In contrast, my oppo mate in a BA B747 of otherwise similar model would have to use RW16, because he couldn't use RW27, because of the "crosswind enhanced" Vmcg limited V1 could not be accommodated on the much shorter runway. So he was faced with a significant crosswind, on a wet runway, much longer taxi distances, and substantially longer track miles in the air.
Such was the result of a certified Vmcg being a variable based on crosswind component.
Again, "back in the day", Qantas had some truly excellent people, for those of us with an engineering background (and I don't mean LAME) who had gone flying, there was a wealth of information available for the asking. Some of us made full use of it. I have always been rather sceptical of OWTs and "conventional wisdom", preferring the check the facts.
Indeed, over many years of instructing, I have always made clear to my students the clear difference between "my opinion" --- to hopefully be considered of some value by the student/candidate , and something stated as a fact, and therefor non-debatable ---- I would always give the student/candidate a reference, so they could check the facts for themselves. It was remarkable, at times, how strongly OWTs and "conventional wisdom" would be defended, in the face of the facts.
Tootle pip!!
PS: Were you every involved with B727 -100/200 certification, the V speed "demonstrations" must have been hairraising ---- I am happy to have only read about them.
With the very greatest of respect, I actually know what I am talking about in these areas --- something that Lookleft is unlikely to accept.
I stated in an earlier post that, to determine how Vmcg (or anything else) for an FAA type and variant was established you have to consult the flight test guide for said type and variant.
This is not the same as a text book definition of Vmcg, as I am certain you would agree.
As to "stories" about special DCA "rules" that said a VH- registered aircraft has a Vmcg that ensured it would stay on the runway in the most adverse crosswinds, I heard that quoted many years ago, but never found any proof. Indeed, I never came across anybody in DCA who would have had the background to conduct such tests, and I have no idea what might have gone on at Moses lake with the B707-138A/B in all its variations.
I never flew the B707-138A/B ( along with the RR powered B707-300 the only significant variants of the B707/720 I haven't flown) so there could have been some sodding around with the numbers there, but the certification of Vmcg for the B707-320B/C with JT3B-3D engines with large blow in fan cowl doors was quoted by Boeing as good to 7kt crosswind,--- straight from the FAA guide and from the mouth of one of the pilots on the flight test program --- and the Limitations (mandatory) section of the manual for a VH-registered aircraft was the same as an N-registered aircraft.
The same was (mostly) not true if it was a G-registered aircraft.
Likewise, most of the V speeds for a G registered aircraft differed from the US/AU Limitations speeds. Again, thank that opinionated and short tempered little Welshman -- who did sign my first flight test approval, although, I might add, not Experimental Flight Test, just "post production/maintenance".
"Back in the day", at YMML on a cold and wet and windy (from the WSW) we used to see the "safety advantages" of applying a crosswind component to the Vmcg, when you had a Vmcg limited V1.
I would be able to use RW 27, with a bit of a crosswind.
In contrast, my oppo mate in a BA B747 of otherwise similar model would have to use RW16, because he couldn't use RW27, because of the "crosswind enhanced" Vmcg limited V1 could not be accommodated on the much shorter runway. So he was faced with a significant crosswind, on a wet runway, much longer taxi distances, and substantially longer track miles in the air.
Such was the result of a certified Vmcg being a variable based on crosswind component.
Again, "back in the day", Qantas had some truly excellent people, for those of us with an engineering background (and I don't mean LAME) who had gone flying, there was a wealth of information available for the asking. Some of us made full use of it. I have always been rather sceptical of OWTs and "conventional wisdom", preferring the check the facts.
Indeed, over many years of instructing, I have always made clear to my students the clear difference between "my opinion" --- to hopefully be considered of some value by the student/candidate , and something stated as a fact, and therefor non-debatable ---- I would always give the student/candidate a reference, so they could check the facts for themselves. It was remarkable, at times, how strongly OWTs and "conventional wisdom" would be defended, in the face of the facts.
Tootle pip!!
PS: Were you every involved with B727 -100/200 certification, the V speed "demonstrations" must have been hairraising ---- I am happy to have only read about them.
Last edited by LeadSled; 7th Sep 2018 at 07:12. Reason: minor change.typo
Moderator
With the very greatest of respect, I actually know what I am talking about in these areas .
I know who you be and, indeed, I respect that background. However, I wasn't aware that you were in the certification expert club ?
This is not the same as a text book definition of Vmcg,
Generally, for any given certification, the final Design Standard detail required for this and that will be as frozen by the relevant Regulator.in conjunction with the applicant. Indeed, were that not the case, no certification would get anywhere .. As we are both aware, the bulk of the rules have changed and developed over the years in light of accident experience and Industry state of the art capabilities. .. which is as things should be, I suggest. Certainly, as we remind the new chums regularly in PPRuNe, the relevant Design Standards must be reviewed to have a beginning notion of what might have transpired during the workup of the particular Type/Model.
As to "stories" about special DCA "rules" that said a VH- registered aircraft has a Vmcg
I presume that we are talking about the narrow runway width program, going back now probably 30 years or more ? Certainly, I was involved on the Industry side with several of the aircraft which went through the early process. I have to say, the activities were a little eye-opening and suggested to me that the standard runway width protocols (ICAO) used previously were a tad average in their lack of any engineering or flight standards rigour. I, for one, am of the view that the local Regulatory approach had much merit .. certainly, I went from being a non-believer to being the devout little wide-eyed engineer during the programs.
While I was on the outside, looking in, as it were, I knew the folk involved with the workup very well. Indeed, a main aim of the test program was to see what the aircraft could, or could not, do in the Vmcg environment and limit the operation for narrow width runways to suit whatever capability might be disclosed during the flight test program. I still have some "interesting" videos of some of the work we did on the several aircraft with which I was involved.
that ensured it would stay on the runway in the most adverse crosswinds, I heard that quoted many years ago, but never found any proof.
'twas the case, indeed .. I was there. Eventually, the early requirements were codified somewhat in an appropriate CAAP along the way.
Indeed, I never came across anybody in DCA who would have had the background to conduct such tests
That's fine. However, I did, and there certainly was a small group of folk at the time who knew what was what and what they were doing. I knew several of the test pilots quite well (one had actually done my initial twin training some years prior albeit that a well-known Industry instructor signed it off ..).
It transpired that I ended up on the long lens video at the runway head for each set of tests ... and, in the way of understatement, those aircraft which were Vmcg challenged certainly tripped the light fantastic during the testing.
was quoted by Boeing as good to 7kt crosswind,--- straight from the FAA guide
I have little specific knowledge of the 707 certification (one of my regrets is that I didn't bid onto it with the AN freight program but them's the breaks).. The 7 kt probably relates to the BCAR rules at the time.
The same was (mostly) not true if it was a G-registered aircraft.
As I recall from reading this and that .. there were a couple of US aircraft which the Brits required to be reworked to account for the 0/7 kt difference ?
"Back in the day", at YMML on a cold and wet and windy (from the WSW) we used to see the "safety advantages" of applying a crosswind component to the Vmcg, when you had a Vmcg limited V1.
Indeed and I am totally in agreement with an operational hat on. However, Vmcg, ie the certification animal, remained the same as it is a certification animal and knows naught of the real world. What was occurring was an operational adjustment of the AFM numbers to account for real world reality in a conservative manner. No doubt, I suspect, Wal Stack's good offices were behind such things .. wonderful chap with a wonderful turn of phrase when telling a tale.
Such was the result of a certified Vmcg being a variable based on crosswind component.
Now, as suggested above, I don't have any specific 707 background. However, are you referring to the AFM data ? .. or company operations data ?
[Note - Without chasing up all the cert basis ins and outs, the CAR 4b generic words were a bit vague re Vmcg - .. air speed, shall be selected by the applicant, but it shall not be less than the minimum speed at which the controllability is demonstrated during the take-off run to be adequate to permit proceeding safely with the take-off, using normal piloting skill, when the critical engine is suddenly made inoperative]
It was remarkable, at times, how strongly OWTs and "conventional wisdom" would be defended, in the face of the facts.
One of the reasons a few of us push the anti-OWT barrow in PPRuNe.
Were you every involved with B727 -100/200 certification
Flew both, and adored the -100, but no specific exposure to the certification program. The -200 ? well I did get one absolute greaser out of the beast .. but only the one. Had many of the other sort, though ...
I know who you be and, indeed, I respect that background. However, I wasn't aware that you were in the certification expert club ?
This is not the same as a text book definition of Vmcg,
Generally, for any given certification, the final Design Standard detail required for this and that will be as frozen by the relevant Regulator.in conjunction with the applicant. Indeed, were that not the case, no certification would get anywhere .. As we are both aware, the bulk of the rules have changed and developed over the years in light of accident experience and Industry state of the art capabilities. .. which is as things should be, I suggest. Certainly, as we remind the new chums regularly in PPRuNe, the relevant Design Standards must be reviewed to have a beginning notion of what might have transpired during the workup of the particular Type/Model.
As to "stories" about special DCA "rules" that said a VH- registered aircraft has a Vmcg
I presume that we are talking about the narrow runway width program, going back now probably 30 years or more ? Certainly, I was involved on the Industry side with several of the aircraft which went through the early process. I have to say, the activities were a little eye-opening and suggested to me that the standard runway width protocols (ICAO) used previously were a tad average in their lack of any engineering or flight standards rigour. I, for one, am of the view that the local Regulatory approach had much merit .. certainly, I went from being a non-believer to being the devout little wide-eyed engineer during the programs.
While I was on the outside, looking in, as it were, I knew the folk involved with the workup very well. Indeed, a main aim of the test program was to see what the aircraft could, or could not, do in the Vmcg environment and limit the operation for narrow width runways to suit whatever capability might be disclosed during the flight test program. I still have some "interesting" videos of some of the work we did on the several aircraft with which I was involved.
that ensured it would stay on the runway in the most adverse crosswinds, I heard that quoted many years ago, but never found any proof.
'twas the case, indeed .. I was there. Eventually, the early requirements were codified somewhat in an appropriate CAAP along the way.
Indeed, I never came across anybody in DCA who would have had the background to conduct such tests
That's fine. However, I did, and there certainly was a small group of folk at the time who knew what was what and what they were doing. I knew several of the test pilots quite well (one had actually done my initial twin training some years prior albeit that a well-known Industry instructor signed it off ..).
It transpired that I ended up on the long lens video at the runway head for each set of tests ... and, in the way of understatement, those aircraft which were Vmcg challenged certainly tripped the light fantastic during the testing.
was quoted by Boeing as good to 7kt crosswind,--- straight from the FAA guide
I have little specific knowledge of the 707 certification (one of my regrets is that I didn't bid onto it with the AN freight program but them's the breaks).. The 7 kt probably relates to the BCAR rules at the time.
The same was (mostly) not true if it was a G-registered aircraft.
As I recall from reading this and that .. there were a couple of US aircraft which the Brits required to be reworked to account for the 0/7 kt difference ?
"Back in the day", at YMML on a cold and wet and windy (from the WSW) we used to see the "safety advantages" of applying a crosswind component to the Vmcg, when you had a Vmcg limited V1.
Indeed and I am totally in agreement with an operational hat on. However, Vmcg, ie the certification animal, remained the same as it is a certification animal and knows naught of the real world. What was occurring was an operational adjustment of the AFM numbers to account for real world reality in a conservative manner. No doubt, I suspect, Wal Stack's good offices were behind such things .. wonderful chap with a wonderful turn of phrase when telling a tale.
Such was the result of a certified Vmcg being a variable based on crosswind component.
Now, as suggested above, I don't have any specific 707 background. However, are you referring to the AFM data ? .. or company operations data ?
[Note - Without chasing up all the cert basis ins and outs, the CAR 4b generic words were a bit vague re Vmcg - .. air speed, shall be selected by the applicant, but it shall not be less than the minimum speed at which the controllability is demonstrated during the take-off run to be adequate to permit proceeding safely with the take-off, using normal piloting skill, when the critical engine is suddenly made inoperative]
It was remarkable, at times, how strongly OWTs and "conventional wisdom" would be defended, in the face of the facts.
One of the reasons a few of us push the anti-OWT barrow in PPRuNe.
Were you every involved with B727 -100/200 certification
Flew both, and adored the -100, but no specific exposure to the certification program. The -200 ? well I did get one absolute greaser out of the beast .. but only the one. Had many of the other sort, though ...
Many years ago the executive of the Oz aviation regulatory authority found that the then current runway width requirements for transport category aircraft were inhibiting growth opportunities for some sectors of the industry.
They directed both the flying operations and airworthiness branches to review the current standards and develop set of standards which would permit these aircraft to operate on “narrow” runways.
The overriding requirement was that the level of safety was maintained.
The airworthiness branch concluded that the only way to maintain the required safety level was to ensure, as far as possible, that the aircraft remained on the runway during both normal and abnormal operations. This required a review of all runway handling characteristics, and all MEL items which could adversely affect aircraft controllability.
This meant the aircraft must remain within the confines of the runway during:
1. Critical engine failure, with a continued takeoff at Vef min and maximum approved crosswind limit;
2. A refused takeoff as above; and,
3. A one engine inoperative approach and landing from a position significantly displaced from the runway centreline at about 500 feet on final approach.
This all required flight testing with the usual requirements for Vmcg tests, such as a calibrated weather station, means of measuring lateral deviation from the runway centre line, disconnecting nosewheel steering, and critical engine shutdown by turning the fuel off. In some cases a throttle chop was an acceptable means of compliance, provided there was a data correction method, approved by the original certification authority.
I carried out the flight testing of, IIRC, 10 aircraft types both jet and turboprop. This was done with company pilots in the RHS. The items which were non-issues were the refused takeoffs and asymmetric landings.
The big issue was staying on the runway during the continue takeoff.We developed a workup method which gave us a good feel for the sensitivity of aircraft handling, to reducing the crosswind component, or increasing Vef and hence V1. I don’t recollect any aircraft which would stay on the runway with a failure at Vmcg and maximum cross wind.
The operators were given the option of how to fit their aircraft with the runways they wished to use. For example if runway length was not limiting they could overspeed V1 and have a higher crosswind limit. For some aircraft a derate which reduced Vmcg may have been an option but I don’t think it was ever used.
This system is still used by Oz CASA, and anybody who Googles CASA Narrow Runway will find all the info. The A380 was limited to 65m runway until a successful narrow runway approval request resulted in clearance to 45m.The procedure was adopted fully or in part by some other regulatory authorities.
This thread is really about crosswind handling, and unfortunately I haven’t much to offer as I used the same techniques for all the aircraft I tested.
Takeoff: keep the wings comfortably close to level with minimum necessary lateral control input, rotation was a bit more difficult to sort out due to yawing moments from both the crosswind and engine asymmetry. But as the book says, all this should be easily accomplished by the average pilot.
The only landing technique used was to fly the approach with drift, during the flare use rudder to align with the centre line, when that stuffed up a bit of bank (within the near ground bank angle limits) and touch down on the upwind wheels.
During my involvement in this exercise I have flown literally hundreds of fuel off engine failures at speeds around Vmcg, with both zero crosswind (as required for Vmcg determination) and with up to limiting crosswinds as required for CASA runway width testing.
It is important to note that FAR part 25 Vmcg testing is a zero crosswind test, FAR part 25 crosswind testing is all engines operating. There is no part 25 certification requirement to blend the two issues, and you all may be operating aircraft which will depart the runway with the critical V1min engine failure. While FAR part 25 has a number of “catch all” paragraphs to weed out unsatisfactory characteristics which may be noticed but don’t have a specific requirement, they are yet to be used in this case. I imagine that the FAA standards development folk have a bunch of statisticians who claim this is ani extremely unlikely event, akin to a double failure, so no accountability necessary.
It should also be noted this was not an exercise in re-determination of Vmcg. The requirements for Vmcg are clearly spelled of in FAR part 25 and the test methods in AC 25- XX ie about 25-7d at the moment. Don`t forget to check the amendment status you are interested in as FAR part 25 Amendment 42 bought in a lot of changes including maximum permitted rudder forces and centreline deviation limits.
Some lessons:
Turboprops have much worse handling qualities than jets in these tests, also the undercarriage layout on many means that a wheel will depart the runway with less deviation than similar jets.
If you wish to get a feel for where your aircraft fits in the scheme of things, get the following information:
1. What was the certification basis? This will show if it is a zero wind Vmcg or a 7kt crosswind Vmcg.
2. What was the lateral deviation determined when Vmcg was tested, the lesser the better.
3. Was the limit pushed to achieve the minimum possible Vmcg to minimize takeoff distance requirements.
This has been put together quickly, from memory as I am far from home with no access to relevant documents.
This was a complicated, time consuming project and only the surface has been touched on. For example I have made no mention of the flying operations and airworthiness systems engineering staff inputs.
They directed both the flying operations and airworthiness branches to review the current standards and develop set of standards which would permit these aircraft to operate on “narrow” runways.
The overriding requirement was that the level of safety was maintained.
The airworthiness branch concluded that the only way to maintain the required safety level was to ensure, as far as possible, that the aircraft remained on the runway during both normal and abnormal operations. This required a review of all runway handling characteristics, and all MEL items which could adversely affect aircraft controllability.
This meant the aircraft must remain within the confines of the runway during:
1. Critical engine failure, with a continued takeoff at Vef min and maximum approved crosswind limit;
2. A refused takeoff as above; and,
3. A one engine inoperative approach and landing from a position significantly displaced from the runway centreline at about 500 feet on final approach.
This all required flight testing with the usual requirements for Vmcg tests, such as a calibrated weather station, means of measuring lateral deviation from the runway centre line, disconnecting nosewheel steering, and critical engine shutdown by turning the fuel off. In some cases a throttle chop was an acceptable means of compliance, provided there was a data correction method, approved by the original certification authority.
I carried out the flight testing of, IIRC, 10 aircraft types both jet and turboprop. This was done with company pilots in the RHS. The items which were non-issues were the refused takeoffs and asymmetric landings.
The big issue was staying on the runway during the continue takeoff.We developed a workup method which gave us a good feel for the sensitivity of aircraft handling, to reducing the crosswind component, or increasing Vef and hence V1. I don’t recollect any aircraft which would stay on the runway with a failure at Vmcg and maximum cross wind.
The operators were given the option of how to fit their aircraft with the runways they wished to use. For example if runway length was not limiting they could overspeed V1 and have a higher crosswind limit. For some aircraft a derate which reduced Vmcg may have been an option but I don’t think it was ever used.
This system is still used by Oz CASA, and anybody who Googles CASA Narrow Runway will find all the info. The A380 was limited to 65m runway until a successful narrow runway approval request resulted in clearance to 45m.The procedure was adopted fully or in part by some other regulatory authorities.
This thread is really about crosswind handling, and unfortunately I haven’t much to offer as I used the same techniques for all the aircraft I tested.
Takeoff: keep the wings comfortably close to level with minimum necessary lateral control input, rotation was a bit more difficult to sort out due to yawing moments from both the crosswind and engine asymmetry. But as the book says, all this should be easily accomplished by the average pilot.
The only landing technique used was to fly the approach with drift, during the flare use rudder to align with the centre line, when that stuffed up a bit of bank (within the near ground bank angle limits) and touch down on the upwind wheels.
During my involvement in this exercise I have flown literally hundreds of fuel off engine failures at speeds around Vmcg, with both zero crosswind (as required for Vmcg determination) and with up to limiting crosswinds as required for CASA runway width testing.
It is important to note that FAR part 25 Vmcg testing is a zero crosswind test, FAR part 25 crosswind testing is all engines operating. There is no part 25 certification requirement to blend the two issues, and you all may be operating aircraft which will depart the runway with the critical V1min engine failure. While FAR part 25 has a number of “catch all” paragraphs to weed out unsatisfactory characteristics which may be noticed but don’t have a specific requirement, they are yet to be used in this case. I imagine that the FAA standards development folk have a bunch of statisticians who claim this is ani extremely unlikely event, akin to a double failure, so no accountability necessary.
It should also be noted this was not an exercise in re-determination of Vmcg. The requirements for Vmcg are clearly spelled of in FAR part 25 and the test methods in AC 25- XX ie about 25-7d at the moment. Don`t forget to check the amendment status you are interested in as FAR part 25 Amendment 42 bought in a lot of changes including maximum permitted rudder forces and centreline deviation limits.
Some lessons:
Turboprops have much worse handling qualities than jets in these tests, also the undercarriage layout on many means that a wheel will depart the runway with less deviation than similar jets.
If you wish to get a feel for where your aircraft fits in the scheme of things, get the following information:
1. What was the certification basis? This will show if it is a zero wind Vmcg or a 7kt crosswind Vmcg.
2. What was the lateral deviation determined when Vmcg was tested, the lesser the better.
3. Was the limit pushed to achieve the minimum possible Vmcg to minimize takeoff distance requirements.
This has been put together quickly, from memory as I am far from home with no access to relevant documents.
This was a complicated, time consuming project and only the surface has been touched on. For example I have made no mention of the flying operations and airworthiness systems engineering staff inputs.
Last edited by zzuf; 7th Sep 2018 at 18:13.
A designer may be familiar with the relevant FARs (in the case of the US) but would really need to refer to all the various ACs in order to have your airframe meet the legal specifications.
Moderator
but would really need to refer to all the various ACs
One can't make much sense of the FARs in isolation without poring over the associated ACs and other bits and pieces .. It's not necessary to observe the AC words .. but only a chap with lots of time and, probably, money on his hands would bother getting into the ensuing arguments .. far easier to take the simple road.
Now that Zzuf has chosen to disclose his background, there are other threads in PPRuNe on the narrow runway saga which flesh some things out a tad more .. Interestingly, his FTE offsider at the time, having gone off to play with B777 and like toys for however long, is back in-house and looks after this stuff in the present world.
One can't make much sense of the FARs in isolation without poring over the associated ACs and other bits and pieces .. It's not necessary to observe the AC words .. but only a chap with lots of time and, probably, money on his hands would bother getting into the ensuing arguments .. far easier to take the simple road.
Now that Zzuf has chosen to disclose his background, there are other threads in PPRuNe on the narrow runway saga which flesh some things out a tad more .. Interestingly, his FTE offsider at the time, having gone off to play with B777 and like toys for however long, is back in-house and looks after this stuff in the present world.
The following advice is from the book Handling the Big Jets by D.P Davies, who joined the British Air Registration Board in August 1949 as Chief Test Pilot and carried out the certification testing of the world's first jet transport aircraft in 1950.
Page 177 headed Reduced Roll Freedom on the Ground.
"During the rotation on the ground, the outer part of a swept wing, because it is aft of the main gear (which is the pivot of the manoeuvre), rotates closer to the ground and the wing tips and flaps can get very close indeed. Under these conditions only a few degrees of roll freedom may exist before something scrapes the runway.
Life is more complicated yet, because it must also be remembered that swept wing aeroplanes roll hard with yaw. The control of this roll has to be nicely matched by the lateral control, bearing in mind the possibly dis-continuity in roll against lateral control application when the spoilers take effect.
So take care when operating in cross winds. On take-off, set in a little into-wind aileron control quite early in the take-off run whether or not you feel it necessary; this will stop the down wind roll which will otherwise occur just before lift-off. Then, throughout the rotation and lift-off, make sure you keep the aeroplane substantially level laterally. On landing, don't get too active on the ailerons close to the ground. Apply enough but not too much and bear in mind the approximate spectacle angle at which the spoilers start to augment roll control. Avoid the divergent lateral oscillations which can develop and eat up your roll clearances in no time"
............................................................ ............................................................ ............................................................ ............................................................ ............................................................ .................................
There is much more good gen about cross-wind operations in the next few paragraphs to be found on page 178.
In 1967, Flight International made the following comment in their review of Handling the Big Jets. "...this is no dry textbook. It is a tremendous, but notably readable, vade-mecum of jet transport flying qualities and design characteristics intended primarily for pilots who have yet to make the transition to jets, but which is packed with information of value to the most experienced of captains."
Interestingly, it has been my experience as a flight simulator instructor that almost no pilot I have talked to in the past 25 years has even heard of, let alone read this marvellous book. It was first published in 1967 and reprinted in November 1999. With the now unprecedented shortage of airline pilots around the world, flying school operators would be doing a great service to their students to ensure they first read Handling the Big Jets before embarking on an airline pilot career.
Page 177 headed Reduced Roll Freedom on the Ground.
"During the rotation on the ground, the outer part of a swept wing, because it is aft of the main gear (which is the pivot of the manoeuvre), rotates closer to the ground and the wing tips and flaps can get very close indeed. Under these conditions only a few degrees of roll freedom may exist before something scrapes the runway.
Life is more complicated yet, because it must also be remembered that swept wing aeroplanes roll hard with yaw. The control of this roll has to be nicely matched by the lateral control, bearing in mind the possibly dis-continuity in roll against lateral control application when the spoilers take effect.
So take care when operating in cross winds. On take-off, set in a little into-wind aileron control quite early in the take-off run whether or not you feel it necessary; this will stop the down wind roll which will otherwise occur just before lift-off. Then, throughout the rotation and lift-off, make sure you keep the aeroplane substantially level laterally. On landing, don't get too active on the ailerons close to the ground. Apply enough but not too much and bear in mind the approximate spectacle angle at which the spoilers start to augment roll control. Avoid the divergent lateral oscillations which can develop and eat up your roll clearances in no time"
............................................................ ............................................................ ............................................................ ............................................................ ............................................................ .................................
There is much more good gen about cross-wind operations in the next few paragraphs to be found on page 178.
In 1967, Flight International made the following comment in their review of Handling the Big Jets. "...this is no dry textbook. It is a tremendous, but notably readable, vade-mecum of jet transport flying qualities and design characteristics intended primarily for pilots who have yet to make the transition to jets, but which is packed with information of value to the most experienced of captains."
Interestingly, it has been my experience as a flight simulator instructor that almost no pilot I have talked to in the past 25 years has even heard of, let alone read this marvellous book. It was first published in 1967 and reprinted in November 1999. With the now unprecedented shortage of airline pilots around the world, flying school operators would be doing a great service to their students to ensure they first read Handling the Big Jets before embarking on an airline pilot career.
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Sometimes you just cut to the chase: back in the day was trained to use cross controls TO THE EXTENT REQUIRED to keep the wings level/rolling down the centreline and maintain that cross control on rotation until well clear of the ground when aerodynamics - as if by a miracle - will gradually ease off/eliminate the cross controls.
Been lucky using same for 29 years - if it ain't broke don't fix it IMHO.
Only times I've been truely caught out and immediately "scared" was training new Captains when they seemed to have the right idea on a croswind take off only to either not be aggressive enough in maintaining the wings level OR, worse yet, backing off the cross controls when initiating rotation and wondering why the downwind wing headed south bigtime.
Good thing was tended to only happen once as they scared the sh*t out of themselves as well!
Cheers.
Been lucky using same for 29 years - if it ain't broke don't fix it IMHO.
Only times I've been truely caught out and immediately "scared" was training new Captains when they seemed to have the right idea on a croswind take off only to either not be aggressive enough in maintaining the wings level OR, worse yet, backing off the cross controls when initiating rotation and wondering why the downwind wing headed south bigtime.
Good thing was tended to only happen once as they scared the sh*t out of themselves as well!
Cheers.