Crosswind With Gust Landings
Mungo Man, another interestingly worded SOP.
Perhaps the following is a pedantic review, but confusion often comes from ill structured SOPs when under high workload and in time pressured situations.
The text encourages the assumption that all wind reports are mean winds; a reasonable view, but perhaps it does not consider errors in reporting wind *.
Is the mean calculated (computation) or just an eye-ball figure by the observer? In some circumstances the mean wind may have included gusts (the max and min) of a varying wind *.
The commander is allowed to use judgement in gusts, but what is assumed about the ability to judge, what are the risks, how might these be countered.
IMHO, the management have relinquished their responsibility and passed it to the commander – unfair, the commander is someone who they should be protecting - his safety is their safety. Everyone has a safety responsibility which should not be given up.
My interpretation of the text describing the max demonstrated crosswind associates the gusts with an airspeed increment for the approach, but some people might associate this with a crosswind gust – already stated in the previous text.
Whilst airspeed increments in gusting conditions reduce the risk of low energy situations during the approach, crosswind gusts require increased control activity, perhaps encountering a limiting situation close to the ground or even on the runway – more rudder required as speed reduces (until wheel side force helps the situation).
In strong gusting crosswinds, a prudent commander might reduce the crosswind limit by half of the gust increment.
Who in the airline has made the ‘considered’ judgement that the max value is not limiting, how did they determine this – fact or supposition? If this is the manufacturers wording (certification speak), then who can discount that the real ‘limit’ might be a few knots higher?
And where is the advice for operating on a wet runway?
Perhaps the following is a pedantic review, but confusion often comes from ill structured SOPs when under high workload and in time pressured situations.
The text encourages the assumption that all wind reports are mean winds; a reasonable view, but perhaps it does not consider errors in reporting wind *.
Is the mean calculated (computation) or just an eye-ball figure by the observer? In some circumstances the mean wind may have included gusts (the max and min) of a varying wind *.
The commander is allowed to use judgement in gusts, but what is assumed about the ability to judge, what are the risks, how might these be countered.
IMHO, the management have relinquished their responsibility and passed it to the commander – unfair, the commander is someone who they should be protecting - his safety is their safety. Everyone has a safety responsibility which should not be given up.
My interpretation of the text describing the max demonstrated crosswind associates the gusts with an airspeed increment for the approach, but some people might associate this with a crosswind gust – already stated in the previous text.
Whilst airspeed increments in gusting conditions reduce the risk of low energy situations during the approach, crosswind gusts require increased control activity, perhaps encountering a limiting situation close to the ground or even on the runway – more rudder required as speed reduces (until wheel side force helps the situation).
In strong gusting crosswinds, a prudent commander might reduce the crosswind limit by half of the gust increment.
Who in the airline has made the ‘considered’ judgement that the max value is not limiting, how did they determine this – fact or supposition? If this is the manufacturers wording (certification speak), then who can discount that the real ‘limit’ might be a few knots higher?
And where is the advice for operating on a wet runway?
Join Date: May 2004
Location: The center of the earths surface
Posts: 290
Likes: 0
Received 0 Likes
on
0 Posts
Guidence of the wise and adherence to for fools.
Cross winds:
This quote! PEi 3721:
Maximum demonstrated crosswind is what has been shown to be safe, beyond that aircraft handling is unknown.
This is incorrect from my understanding of the certification requirements.
If the Aircraft is placarded with the words "Max Demonstarted Cross Wind 25Kts:
On the day of crosswind certification demonstration, the Captain/crew/pilots/test pilots/monkeys/ whatever! on this day may well have been Demonstrating in 25, & maybe 35 kts, maybe even 30 gusting 40,whatever! they being the demonstrating Crew/Captain for this exercise may enter in the little box Eg 25Kts, as the Captain/test pilot will recommend this as a good average for the average pilot:
In the comments section he may write, and you could quite reasonably expect to see something written like: (wind 30-40kts, no handling surprises, good predictable directional control with rudder in these conditions a safe average of 25kts is acceptable)
IT DOES NOT MEAN: QUOTE! "Maximum demonstrated crosswind is what has been shown to be safe, beyond that aircraft handling is unknown"
****e: 26kts and my wings fall off.
Many a time with a company SOP limiting at max demonstrated, yet routinely operating into scheduled destinations in "scheduled seasonal" windy conditions, the wind would be a steady 30-35kts, at a particular time of the year for a month or two, no one ever diverts, nor cancels flights! does this mean we are operating unsafe! NO, if on the other hand, it becomes more than just wind with the odd "gentle" gust, ( low vis, drifting sand, gusts of 30-40kts) on top of the wind, then as has happened to most of the other pilots and myself, power up and get the hell outa Dodge.
If the aircraft is placarded with MAX CROSSWIND OPERATING LIMIT 25Kts, This is an aerodynamic/performance limitation and it needs to be more closely, "stringently adhered to".
Rules, what do we do with them? "the generation of the now" have no idea on how to use professional discretion.
This quote! PEi 3721:
Maximum demonstrated crosswind is what has been shown to be safe, beyond that aircraft handling is unknown.
This is incorrect from my understanding of the certification requirements.
If the Aircraft is placarded with the words "Max Demonstarted Cross Wind 25Kts:
On the day of crosswind certification demonstration, the Captain/crew/pilots/test pilots/monkeys/ whatever! on this day may well have been Demonstrating in 25, & maybe 35 kts, maybe even 30 gusting 40,whatever! they being the demonstrating Crew/Captain for this exercise may enter in the little box Eg 25Kts, as the Captain/test pilot will recommend this as a good average for the average pilot:
In the comments section he may write, and you could quite reasonably expect to see something written like: (wind 30-40kts, no handling surprises, good predictable directional control with rudder in these conditions a safe average of 25kts is acceptable)
IT DOES NOT MEAN: QUOTE! "Maximum demonstrated crosswind is what has been shown to be safe, beyond that aircraft handling is unknown"
****e: 26kts and my wings fall off.
Many a time with a company SOP limiting at max demonstrated, yet routinely operating into scheduled destinations in "scheduled seasonal" windy conditions, the wind would be a steady 30-35kts, at a particular time of the year for a month or two, no one ever diverts, nor cancels flights! does this mean we are operating unsafe! NO, if on the other hand, it becomes more than just wind with the odd "gentle" gust, ( low vis, drifting sand, gusts of 30-40kts) on top of the wind, then as has happened to most of the other pilots and myself, power up and get the hell outa Dodge.
If the aircraft is placarded with MAX CROSSWIND OPERATING LIMIT 25Kts, This is an aerodynamic/performance limitation and it needs to be more closely, "stringently adhered to".
Rules, what do we do with them? "the generation of the now" have no idea on how to use professional discretion.
I believe the wind passed by ATC when cleared to land is the average (with gust bearing in mind the definition of a gust is 10 kt or more from the mean wind speed) over the last two minutes.
You can of course ask ATC for the "instant" wind.
You can of course ask ATC for the "instant" wind.
Join Date: Dec 2008
Location: Netherlands
Posts: 96
Likes: 0
Received 0 Likes
on
0 Posts
Flying at crosswinds near or at the demonstrated value is not without risk. Most pilots will not do this on a weekly basis and training simulators are not very good in representing the effects of gusty winds on the airframe. Furthermore the way the certification works makes you wonder how realistic demonstrated values are to the airline pilot. I have studied this topic for many years now and analysed numerous accident/incidents related to crosswind. The gustiness of the wind played a very important role in the vast majority of these cases. There has been little progress in solving some of the important issues.
Some recommended reading material:
Crosswind Certification - How does it affect you?
http://www.nlr.nl/id~5114/lang~en.pdf
and
Safety aspects of aircraft operations in crosswind
http://www.nlr-atsi.com/downloads/NLR-TP-2001-217.pdf
Some recommended reading material:
Crosswind Certification - How does it affect you?
http://www.nlr.nl/id~5114/lang~en.pdf
and
Safety aspects of aircraft operations in crosswind
http://www.nlr-atsi.com/downloads/NLR-TP-2001-217.pdf
hoggsnortrupert, I’m not sure where I am on your scale of assessors; probably in all categories, and particularly after a poorly judged crosswind landing one might as well be a monkey.
Whilst the certification requirements may not be precise, they do, with additional flight test guidance, provide a basis for determining crosswind conditions suitable for an ‘average’ pilot – on an average day, etc, etc, - all things being equal – except they rarely are.
The manufacturer’s tests involve ‘considered’ opinion; however, in my experience not by an individual but as a team effort. Both crewmembers have probably flown the test, and in alternate directions for a given crosswind. After which the air and ground-station data is reviewed, then discussion with AeroD, airworthiness, training, and occasionally the certification authority.
The manufacturer may have flown landings in conditions beyond ‘the max demonstrated’, but in circumstances where the conditions were unstable or data unavailable. This experience is often used when considering the results of actual tests – either a lenient or a more restrictive judgment. However, what might be known to a test crew is unlikely to be available to a line pilot, thus operation beyond max demonstrated is best treated as ‘handling unknown’.
Crosswind certification is one (if not the only) area where there is no margin at the limiting condition; compare with Vmo-Vne, Vref-Vs, or runway length required. Most flight operations provide the crew with considerable protection from the randomness of the environment and occasionally their own judgment; crosswinds can be very unforgiving.
Pilots who land in cross winds/gusts greater the max demonstrated, in the circumstances which you describe, are not necessarily ‘unsafe’ – that’s a relative term, but they are, perhaps unknowingly, accepting high risks.
Often high risk operations are successful, and this is used to redatum a pilot’s norm – a biased, habitual behavior.
We rarely understand all of the risks taken in an operation or the effects of ‘so called’ risk alleviating procedures; it might only require a small change in the conditions to invalidate what a pilot has assumed from previous inappropriate use.
You correctly respect a hard ‘limit’, but interpret max demonstrated as something with margin; I disagree.
As explained above and in previous posts the as-yet-undetermined ‘hard limit’ may only be at max demonstrated +1kt; thus any landing above max demonstrated might have unacceptable risk with severe consequences.
Rules, what do we do with them? "the generation of the now" have no idea on how to use professional discretion.
Rules don’t prevent crews from exercising discretion; they enable discretion, which can be exercised on the safe side of the rule (limit), without bias, and being fully aware of the assumptions being made.
Whilst I would agree that many pilots, both old and new, fail to comprehend this, it is not necessary to encourage pilots to take risks to exercise their discretion.
Discretion (prudence, judgment, carefulness, caution, responsibility) is not intended to identify risk taking opportunities; it is to minimize risk, thus maximizing safety.
Refs:
CS 25 Certification of Large Aircraft (FAR similar).
AC 25-7A Flight test guide for certification of transport category airplanes.
Whilst the certification requirements may not be precise, they do, with additional flight test guidance, provide a basis for determining crosswind conditions suitable for an ‘average’ pilot – on an average day, etc, etc, - all things being equal – except they rarely are.
The manufacturer’s tests involve ‘considered’ opinion; however, in my experience not by an individual but as a team effort. Both crewmembers have probably flown the test, and in alternate directions for a given crosswind. After which the air and ground-station data is reviewed, then discussion with AeroD, airworthiness, training, and occasionally the certification authority.
The manufacturer may have flown landings in conditions beyond ‘the max demonstrated’, but in circumstances where the conditions were unstable or data unavailable. This experience is often used when considering the results of actual tests – either a lenient or a more restrictive judgment. However, what might be known to a test crew is unlikely to be available to a line pilot, thus operation beyond max demonstrated is best treated as ‘handling unknown’.
Crosswind certification is one (if not the only) area where there is no margin at the limiting condition; compare with Vmo-Vne, Vref-Vs, or runway length required. Most flight operations provide the crew with considerable protection from the randomness of the environment and occasionally their own judgment; crosswinds can be very unforgiving.
Pilots who land in cross winds/gusts greater the max demonstrated, in the circumstances which you describe, are not necessarily ‘unsafe’ – that’s a relative term, but they are, perhaps unknowingly, accepting high risks.
Often high risk operations are successful, and this is used to redatum a pilot’s norm – a biased, habitual behavior.
We rarely understand all of the risks taken in an operation or the effects of ‘so called’ risk alleviating procedures; it might only require a small change in the conditions to invalidate what a pilot has assumed from previous inappropriate use.
You correctly respect a hard ‘limit’, but interpret max demonstrated as something with margin; I disagree.
As explained above and in previous posts the as-yet-undetermined ‘hard limit’ may only be at max demonstrated +1kt; thus any landing above max demonstrated might have unacceptable risk with severe consequences.
Rules, what do we do with them? "the generation of the now" have no idea on how to use professional discretion.
Rules don’t prevent crews from exercising discretion; they enable discretion, which can be exercised on the safe side of the rule (limit), without bias, and being fully aware of the assumptions being made.
Whilst I would agree that many pilots, both old and new, fail to comprehend this, it is not necessary to encourage pilots to take risks to exercise their discretion.
Discretion (prudence, judgment, carefulness, caution, responsibility) is not intended to identify risk taking opportunities; it is to minimize risk, thus maximizing safety.
Refs:
CS 25 Certification of Large Aircraft (FAR similar).
AC 25-7A Flight test guide for certification of transport category airplanes.
Join Date: Sep 1999
Location: Scotland
Posts: 417
Likes: 0
Received 0 Likes
on
0 Posts
Well said PEI3721. Discretion to step outside SOPs / "limits" is something that is exercised and understood by more modern pilots than the previous poster suggests. Whilst the quantity of printed procedures we have is greater than that of 20/30 years ago, they have been included to avoid repeats of other pilot's misfortune.
More rules don't necessarily make more robots. It's unfair to suggest the rule-conscious pilot has no initiative.
More rules don't necessarily make more robots. It's unfair to suggest the rule-conscious pilot has no initiative.
Join Date: Feb 2006
Location: Rapunzel's tower
Posts: 441
Likes: 0
Received 0 Likes
on
0 Posts
Old thread resurrection
Hi there
I’ve been handed a topic about crosswinds from my (ATC) boss and noticed this thread.
Here’s an excerpt from CAP789 (UK) - Requirements and Guidance Material for Operators...I think it’s current?...
Crosswind Limits for Take-off and Landing
It is not sufficient to repeat a statement in an AFM that
a particular crosswind component has been found to be acceptable; operators' limitations should be stated in unequivocal terms and account taken of the effect of gusts and surface conditions. Limits in excess of any figure mentioned in the AFM will not be acceptable. In addition, consideration should be given to any reduction in limits due to narrow runways.
So what do your SOPs state with regard to (a) max crosswind component for dry runway, (b) max crosswind for wet, or worse, runway, and (c) what about gusts for either dry or wet, or worse, runway????
Is there a percentage degredation for wet runways? I’ve heard of +15% for landing distance (unless runway is advised of “slippery when wet” - in which case landing distance is further increased) but what about gusts? Anyone have a rule of thumb for dry and wet runways???
Also, does a 15% increase in landing distance equate to a 15% reduction in crosswind limit???
Is the same true for “narrow” runways?
Over to you.....
I’ve been handed a topic about crosswinds from my (ATC) boss and noticed this thread.
Here’s an excerpt from CAP789 (UK) - Requirements and Guidance Material for Operators...I think it’s current?...
Crosswind Limits for Take-off and Landing
It is not sufficient to repeat a statement in an AFM that
a particular crosswind component has been found to be acceptable; operators' limitations should be stated in unequivocal terms and account taken of the effect of gusts and surface conditions. Limits in excess of any figure mentioned in the AFM will not be acceptable. In addition, consideration should be given to any reduction in limits due to narrow runways.
So what do your SOPs state with regard to (a) max crosswind component for dry runway, (b) max crosswind for wet, or worse, runway, and (c) what about gusts for either dry or wet, or worse, runway????
Is there a percentage degredation for wet runways? I’ve heard of +15% for landing distance (unless runway is advised of “slippery when wet” - in which case landing distance is further increased) but what about gusts? Anyone have a rule of thumb for dry and wet runways???
Also, does a 15% increase in landing distance equate to a 15% reduction in crosswind limit???
Is the same true for “narrow” runways?
Over to you.....
Join Date: Jun 2002
Location: Wor Yerm
Age: 68
Posts: 4
Likes: 0
Received 0 Likes
on
0 Posts
Gusts do not apply during planning. But they do have to be taken into account for landing (and takeoff). given the additional company restriction I’d ask for instaneous winds. If these were beyond the company limit just before landing (not necessarily at MDA/DH) even if fully stabilised I’d go around. If instaneous winds were not available I’d divert. This is obviously the company’s intention and it’s what you are paid to do and must have been budgeted into their operating costs. That the aircraft is still within its crosswind limits and other operators of the same type are landing is irrelevant.
A lot of this depends what is explicitly written in your OM A. My current company has a blanket statement that damp runways are wet for performance purposes. My previous company had bespoke options for certain performance limiting grooved runways.
Regarding crosswind limits, my previous company had fixed limits written into the performance manual, with a written calculation method to factor in gusts. My current employer defers to the manufacturer guidelines in the Flight Crew Training Manual which gives the Captain a measure of discretion regarding gusts.
The crosswind limits decrease based on the braking action on the runway, but the landing distance available doesn’t come into it.
Regarding crosswind limits, my previous company had fixed limits written into the performance manual, with a written calculation method to factor in gusts. My current employer defers to the manufacturer guidelines in the Flight Crew Training Manual which gives the Captain a measure of discretion regarding gusts.
The crosswind limits decrease based on the braking action on the runway, but the landing distance available doesn’t come into it.
good egg, first to reiterate some previous points. Crosswind ‘max demonstrated’ is in the Operating Manual as advisory information. The AFM contains limiting conditions as hard aircraft limits (rarely for manual landing, always for autoland).
Previously, aircraft manufacturers published advise according to what had been tested for manual landing, usually on an opportunity basis. This might only relate to dry runway, or steady wind. However with increasing focus on runway excursions, manufacturers might now provide expanded advice on interpreting gusts, wet or contaminated runways, width, etc.
The message is to read the small print in the manufacturers documents.
There are several safety publications with advise on wet crosswind restrictions, but the manufacturer should always be considered first. Then assess other factors as per landing distance, how wet is ‘wet’, what form of contamination, type of runway surface, width; all relate to crosswinds.
Wet smooth concrete may be like like ice. High-friction porous surfaces are generally good, providing that they are not contaminated with rubber or dust . Grooving should not be included in assessments unless you are sure that the grooves are clear and provide good drainage, which may not the case after a heavy downpour.
IMHO advice given re crosswind component should be treated as a limit, and further restriction applied for gusts, particularly as the actual variation is unknown; ATC reports are not absolute, wind not measured at the threshold, only an average, etc.
If you don’t know, not sure - how wet, what gust, width; give yourself more margin.
TA, #33, does the U.K. CAA agree with that view? IIRC there was a policy statement that there is no such thing as ‘damp grooved equals dry’?
Jw, #35, re landing distance; except when using credit for reverse to stop, and reverse affects directional control - fin blanking etc, or an aircraft type tends to lift a wing in crosswinds without sufficient aileron input.
Previously, aircraft manufacturers published advise according to what had been tested for manual landing, usually on an opportunity basis. This might only relate to dry runway, or steady wind. However with increasing focus on runway excursions, manufacturers might now provide expanded advice on interpreting gusts, wet or contaminated runways, width, etc.
The message is to read the small print in the manufacturers documents.
There are several safety publications with advise on wet crosswind restrictions, but the manufacturer should always be considered first. Then assess other factors as per landing distance, how wet is ‘wet’, what form of contamination, type of runway surface, width; all relate to crosswinds.
Wet smooth concrete may be like like ice. High-friction porous surfaces are generally good, providing that they are not contaminated with rubber or dust . Grooving should not be included in assessments unless you are sure that the grooves are clear and provide good drainage, which may not the case after a heavy downpour.
IMHO advice given re crosswind component should be treated as a limit, and further restriction applied for gusts, particularly as the actual variation is unknown; ATC reports are not absolute, wind not measured at the threshold, only an average, etc.
If you don’t know, not sure - how wet, what gust, width; give yourself more margin.
TA, #33, does the U.K. CAA agree with that view? IIRC there was a policy statement that there is no such thing as ‘damp grooved equals dry’?
Jw, #35, re landing distance; except when using credit for reverse to stop, and reverse affects directional control - fin blanking etc, or an aircraft type tends to lift a wing in crosswinds without sufficient aileron input.
