Demonstrated X wind a pointless figure ?
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Demonstrated X wind a pointless figure ?
Is there any practical value to a demonstrated X wind figure or is it only of value to novice pilots ?
I once landed a Seneca at double its demonstrated X wind and that made me realise it was no where near the actual limit of the aircraft
So why register it at all ?
Pace
I once landed a Seneca at double its demonstrated X wind and that made me realise it was no where near the actual limit of the aircraft
So why register it at all ?
Pace
I once landed a C 172 on a day where it was blowing 35 kts with a 25 kt cross wind component. With the wing way down and full rudder I held some crab right to touchdown and made a relatively uneventfull landing. However the aircraft almost overturned when I went to turn off the runway. My decision making that day left something to be desired.......
Anyway to answer the question, demonstrated X-wind component means at that wind velocity or less, the aircraft can be landed without requiring more than normal levels of skill or special maneuvering. When dealing with higher x-winds the pilot will need to make a personal assessment of the situation and their skill and currency levels.
The bigger issue IMO is that too many pilots seems to struggle to make an acceptable landing with a cross-wind significantly less than the demonstrated value.
In my limited experience of looking into demonstrated cross-wind components, the value seems to acrue to the manufacturer, who has to tick a box during the certification process.
They mostly only test up to the maximum value required by EASA/FAA - 20% of Vso, which results in ludicrously low values in the case of gliders.
Most gliders will handle much stronger cross-winds and some manufacturer's handbooks admit as much. On the other hand, some powerplanes I've flown feel right on the edge at the handbook crosswind value.
BPF's comment is very valid though. It's not just the landing but what happens afterwards. Many years ago, someone took my favourite rental 172 (i.e. cheap) to Lethbridge and landed in a gusty 50 kt Chinook wind. No cross-wind problems, since the runway was into wind. Thngs went to pieces when he turned round to backtrack and ended up inverted!
They mostly only test up to the maximum value required by EASA/FAA - 20% of Vso, which results in ludicrously low values in the case of gliders.
Most gliders will handle much stronger cross-winds and some manufacturer's handbooks admit as much. On the other hand, some powerplanes I've flown feel right on the edge at the handbook crosswind value.
BPF's comment is very valid though. It's not just the landing but what happens afterwards. Many years ago, someone took my favourite rental 172 (i.e. cheap) to Lethbridge and landed in a gusty 50 kt Chinook wind. No cross-wind problems, since the runway was into wind. Thngs went to pieces when he turned round to backtrack and ended up inverted!
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I would say it is pointless. It could be accurate, it could be wildly inaccurate there is little way of knowing.
The aircraft owner becomes a test pilot as soon as this demonstrated figure is reached and may be far short of what is possible.
Also, can the original "demonstrated" be updated? Or is the figure cast in stone for that make/model?
The aircraft owner becomes a test pilot as soon as this demonstrated figure is reached and may be far short of what is possible.
Also, can the original "demonstrated" be updated? Or is the figure cast in stone for that make/model?
Not quite pointless.
It's just a minimum figure that the Test Pilot(s) established during the flight testing .
It could have just been the strongest crosswind that blew during the Certification process!
MJ
It's just a minimum figure that the Test Pilot(s) established during the flight testing .
It could have just been the strongest crosswind that blew during the Certification process!
MJ
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We know how it was arrived at and when. The point is, how relevant, accurate a guide it is.
My a/c has a "demonstrated" 12knots the day it was certified 55 yrs ago, I, with just 250 hrs have little problem with 20knots, I am sure that in the hands of someone who can fly, an even higher figure could be achieved. So what is the point of the 12knots figure?
My a/c has a "demonstrated" 12knots the day it was certified 55 yrs ago, I, with just 250 hrs have little problem with 20knots, I am sure that in the hands of someone who can fly, an even higher figure could be achieved. So what is the point of the 12knots figure?
Going out on a limb a bit here but I guess it might have something to do with the claim culture in some societies as well. Some pilots get in trouble before they even get near the demonstrated number and the wording may have been chosen to avoid claims after such incidents. You could also argue that it makes the aircraft more flexible to operate. Yes, you are in a sense operating as a test pilot once you venture above that number but as long as the rest of the paperwork doesn't say anything that converts it into a hard limit, you're able to legally operate in some serious crosswind conditions if you so desire. In the end it is up to you as a pilot to make the decision whether to land or divert to another, better placed, runway. The max demonstrated value in the books should at that point be a serious warning but if you are familiar with the aircraft and your own personal limits then the responsibility is yours to make that call.
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"Demonstrated" crosswind tells you exactly that and it usually specifices for which kind of pilot (some old POH says usual, some say average, it depends on when it was written). It just gives you an idea how crosswind sensitive the bird is and what is usually safe. But, these are writings in old POH, new ones often tell you "max allowed crosswind" or "standard ops max limit crosswind" and these wordings do have an impact on air incident investigations as well as insurance coverage. In the case of "demonstrated" it is a hint, in case of "max certified" it is a setting for allowed POH operational limits. In first case and an incident you underestimated your skills, a mistake, in second case you violated operational limits. And be asured, a 1955 C172 will be case 1, while an after1986 C172 may be case 2.
It worries me somewhat, not least on PPrune where there's some track record of such behaviour, when people start publishing what seems like authoritative information from long experience - but on closer scrutiny is substantially nonsense.
For example:-
Is indeed true, but then subsequently
Is untrue - the concept of an average pilot exists in some airworthiness standards, albeit using other forms of words, but is not and never has been used in aircraft manuals: either civil or military. The anonymous poster then says something that actually is close to true, such as:-
Neither of those terms are in use, nor ever have been. Recent civil manuals do not list "max allowed" or "permitted", that exists in some pre-1970s manuals, and military manuals. More recent civil manuals use "maximum demonstrated" - which essentially means what the company test pilots achieved without scaring themselves, with the caveat that certification standards require this to exceed some minimum values, normally referenced to stall speed.
This next is also substantially untrue:-
I'm sure there's one or two obscure cases somewhere - but the POH crosswind limits are not normally discussed in BOI/AAIB reports, nor in insurance claims.
Chickenhouse - I'm not sure who you are, although I can guess. But for goodness sake stop playing stupid games. This is the third time in the last few weeks [that I have spotted] when you have posted substantially untrue information, phrased with great authority - and such things can cause damage, and have done before. Show a bit more responsibility.
G
For example:-
"Demonstrated" crosswind tells you exactly that
it usually specifices for which kind of pilot (some old POH says usual, some say average, it depends on when it was written).
But, these are writings in old POH, new ones often tell you "max allowed crosswind" or "standard ops max limit crosswind"
This next is also substantially untrue:-
these wordings do have an impact on air incident investigations as well as insurance coverage.
Chickenhouse - I'm not sure who you are, although I can guess. But for goodness sake stop playing stupid games. This is the third time in the last few weeks [that I have spotted] when you have posted substantially untrue information, phrased with great authority - and such things can cause damage, and have done before. Show a bit more responsibility.
G
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Is there any practical value to a demonstrated X wind figure or is it only of value to novice pilots ?
I once landed a Seneca at double its demonstrated X wind
I once landed a Seneca at double its demonstrated X wind
When your glider wing is knee high, you will find quite a bit less crosswind down there – the trick lies in dealing with the change in wind in the last few feet.
Just remember not to turn out of a crosswind. There's no aileron control when the wind is spanwise.
I scrubbed a flight in a 172 because of a 25 kt wind down the runway. The downwind taxi would have been problematic.
Just remember not to turn out of a crosswind. There's no aileron control when the wind is spanwise.
I scrubbed a flight in a 172 because of a 25 kt wind down the runway. The downwind taxi would have been problematic.
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I scrubbed a flight in a 172 because of a 25 kt wind down the runway. The downwind taxi would have been problematic.
There's no aileron control when the wind is spanwise.
I believe the EV 97 Euorostar states in the POH that beyond the 10kts DCC, rudder & aileron in-effectiveness could give problems. I know it's a different "certification" issue but you can't change the physics if the testing is reliable.
As an afterthought, it would be more useful if manufacturer's did actually state at what component the aircraft cannot be controlled safely during the landing phase, rather than the "test pilots" findings on a particular day. I'm sure that this figure could be accurately defined using modern aerodynamics software.
Last edited by PA28181; 31st Jan 2016 at 22:24. Reason: Punctuation error
Demonstrated Crosswind is the point at which YOU become the test pilot.
Maybe your test works out - maybe it doesn't. What's your "Right Stuff" component?
If an accident or incident is a loss of control, of a type that suggests crosswinds were a factor (runway excursion, for example), investigators will most certainly look at the actual conditions, compared to the aircrafts's published characteristics.
And may well include the winds and aircraft procedures as factors in the accident - if not the primary cause.
ASN News » Report: Fokker 50 runway excursion when tired crew lands outside crosswind limits
Accident: Carpatair AT72 at Rome on Feb 2nd 2013, runway excursion on landing, main and nose gear collapsed
In the second, expressed as:
"- the conviction of the commander that due to his experience and skills he could still manage a safe landing despite critical winds."
Ooops - wrong.
Maybe your test works out - maybe it doesn't. What's your "Right Stuff" component?
If an accident or incident is a loss of control, of a type that suggests crosswinds were a factor (runway excursion, for example), investigators will most certainly look at the actual conditions, compared to the aircrafts's published characteristics.
And may well include the winds and aircraft procedures as factors in the accident - if not the primary cause.
ASN News » Report: Fokker 50 runway excursion when tired crew lands outside crosswind limits
Accident: Carpatair AT72 at Rome on Feb 2nd 2013, runway excursion on landing, main and nose gear collapsed
In the second, expressed as:
"- the conviction of the commander that due to his experience and skills he could still manage a safe landing despite critical winds."
Ooops - wrong.
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If you had had an accident on landing and killed a passenger, especially if it had been in the US: would the demonstrated cross wind number have featured and carried any weight in the subsequent law suit?
This is the very point I am making! In my case it was flying into Denham and the wind was fairly steady and directly across.
Strangely I had little expectation of landing and was more expecting to go around back into the air.
It surprised me when it settled quite nicely onto the runway.
But your point is valid! If your aircraft has say a demonstrated 15 KTS do you decline an approach and landing because its 20 KTS?
If for any reason you mess up and go off the runway could that demonstrated figure be used against you for even 1 KT over?
Pilots can mess up below the demonstrated X wind limit as well as way above and damage the aircraft.
As demonstrated is way off the actual limit I wonder what the point is of having a demonstrated figure at all ? and what use it is to anybody
addendum
regarding the incident posted above ( Fokker 50) please note it states that they exceeded the OPERATORS limit not the manufacturers demonstrated X wind figure. maybe the two were the same maybe not
Maybe Ghengis can explain? As a limit set to a percentage of rudder authority at a given speed might be more accurate and meaningful
Pace
Last edited by Pace; 31st Jan 2016 at 22:43.
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Chickenhouse - I'm not sure who you are, although I can guess. But for goodness sake stop playing stupid games. This is the third time in the last few weeks [that I have spotted] when you have posted substantially untrue information, phrased with great authority - and such things can cause damage, and have done before. Show a bit more responsibility.
English comprehension certainly isn't.
Moderator
Great discussion, albeit with some speculation.
To answer the OP's question, for a current certification basis airplane. demonstrating compliance with the requirement for crosswind control is required:
Thereafter, presenting that demonstration of compliance in the flight manual is required:
And to the standard:
So it's not a secret conspiracy to "limit" what a pilot does with a plane, but the required presentation of information that the authorities consider appropriate to provide for the pilot.
It is useful to indicate to a pilot how much extra effort and precision they might have to apply to their flying as they approach, and possibly exceed that value. If they cannot manage the "demonstrated" value, perhaps some additional practice is warranted, as it is a "average skill" value - I think we might be expecting the test pilot to do even better!
Quick rules of thumb: If you cannot hold the runway centerline during the initial phase of the takeoff, perhaps abort, and rethink if you need to takeoff that runway at that time. If you cannot hold the runway centerline during final approach, completing the landing may be difficult. Maybe continue with caution, prepared to go around and look for somewhere else to land.
To answer the OP's question, for a current certification basis airplane. demonstrating compliance with the requirement for crosswind control is required:
Sec. 23.233
Directional stability and control.
[(a) A 90 degree cross-component of wind velocity, demonstrated to be safe for taxiing, takeoff, and landing must be established and must be not less than 0.2
.]
Directional stability and control.
[(a) A 90 degree cross-component of wind velocity, demonstrated to be safe for taxiing, takeoff, and landing must be established and must be not less than 0.2
Sec. 23.1585
Operating procedures.
(a) For all airplanes, information concerning normal, abnormal (if applicable), and emergency procedures and other pertinent information necessary for safe operation and the achievement of the scheduled performance must be furnished, including--
(1) ..... (2) The maximum demonstrated values of crosswind for takeoff and landing, and procedures and information pertinent to operations in crosswinds;.......
Operating procedures.
(a) For all airplanes, information concerning normal, abnormal (if applicable), and emergency procedures and other pertinent information necessary for safe operation and the achievement of the scheduled performance must be furnished, including--
(1) ..... (2) The maximum demonstrated values of crosswind for takeoff and landing, and procedures and information pertinent to operations in crosswinds;.......
...These procedures must be able to be executed consistently by pilots of average skill in atmospheric conditions reasonably expected to be encountered in service....
It is useful to indicate to a pilot how much extra effort and precision they might have to apply to their flying as they approach, and possibly exceed that value. If they cannot manage the "demonstrated" value, perhaps some additional practice is warranted, as it is a "average skill" value - I think we might be expecting the test pilot to do even better!
Quick rules of thumb: If you cannot hold the runway centerline during the initial phase of the takeoff, perhaps abort, and rethink if you need to takeoff that runway at that time. If you cannot hold the runway centerline during final approach, completing the landing may be difficult. Maybe continue with caution, prepared to go around and look for somewhere else to land.
I think that there's a few aeroplanes where "demonstrated limit" is simply the worst that could be achieved before the aeroplane was certified and the certification team were well aware that they'd not reached the aircraft's limits - nor probably were particularly worried by that fact.
G
G