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Old 15th Jul 2009, 10:52   #21 (permalink)
 
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This discussion jogged a faint memory so I went looking and found this which is an extract from here,

"2004 Flight Operations Symposium Questions May 9 – 12, 2004, Bell Harbor Convention Center"


20. Are the published crosswind guidelines piloted simulations?

<Answer>. The 737 classic, the 757, the 767 and the 777 takeoff crosswind guidelines are based on piloted cab simulations assuming an engine out refused takeoff maneuver at an adverse loading condition using normal piloting techniques. The published crosswinds were selected to provide adequate airplane control. The 737NG and 747 takeoff crosswind guidelines are based on engineering analysis and simulation studies assuming the same
engine out refused takeoff maneuver.

The 737 classic, 737NG, 747-400, 757, 767, and 777 landing crosswind guidelines are based on piloted cab simulations at an adverse loading condition using normal piloting techniques. Both all engines operating and engine out landings were considered. As above, the published crosswinds were selected to provide adequate airplane control.

21. What is the difference between the crosswind guidelines and the demonstrated crosswind data in the airplane flight manual?

<Answer>. The AFM "demonstrated" value is simply the highest crosswind conditions that were encountered during the airplane flight test program. The recommended crosswind limits were determined by analysis and piloted simulator evaluation, not by flight test.

An interesting comment, the last sentence.

Regards,
BH
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Old 15th Jul 2009, 16:19   #22 (permalink)
 
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"Demonstrated Crosswind Component" is NOT a limit unless it is listed in the limitations section of the POH. Since the certification must be flown 'as an average pilot', I have heard from reliable sources that the test pilot is not supposed to make any compensation for the crosswind and just plunks it down. A test of the landing gear strength really if you think about it. With good pilot skills you should be able to handle at least up to the DCC,
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Old 15th Jul 2009, 16:34   #23 (permalink)
 
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Quote:
I can't seem to get a definitive answer to this. What does "Max demonstrated X-wind" actually mean?

Is it:
A) Most crosswind the aircraft has been landed in without kicking off drift (crab technique).
B) Most crosswind the aircraft has been landed in with drift kicked off (crab technique).
C) Most demonstrated using wing down method.
D) None of the above.
As I understand from an old test-pilot friend some years ago.

....Using the maximum crosswind available during the certification phase for the aircraft, and, using the cross-wind landing technique as described in the Aircraft Flight Manual / FCOM.
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Old 15th Jul 2009, 17:06   #24 (permalink)
 
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Quote:
"Demonstrated Crosswind Component" is NOT a limit unless it is listed in the limitations section of the POH.
That is either a tautology or not always true... As far as the manufacturer is concerned, it is not limiting. It may or may not be a limit to any given operation depending on what regulations apply to that operation.
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Old 20th Sep 2011, 16:12   #25 (permalink)
IGh
 
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Old Demo'd X-wind vs NEW Enhanced X-wind

EXCERPTS -- from AAR:

Attempted Takeoff in Strong and Gusty Crosswind Conditions ... Boeing 737-500, N18611 … AAR-10/04. [CO1404 / 20Dec08]

2.4.2 Crosswind Guidelines and Limitations ...

"… The NTSB concludes that, because there are no standards for the development of enhanced crosswind guidelines for transport-category airplanes, Boeing did not adequately consider the dynamic handling qualities of the 737 during takeoff or landing in strong and gusty crosswinds; it is likely that the enhanced crosswind guidelines developed by other manufacturers are similarly deficient. Therefore, the NTSB recommends that, once realistic, gusty crosswind profiles as asked for in Safety Recommendation A-10-110 are developed, the FAA develop a standard methodology, including pilot-in-the-loop testing, for transport-category airplane manufacturers to establish empirically based, type-specific maximum-gusting-crosswind limitations for transport-category airplanes that account for wind gusts. Further, the NTSB recommends that, once a methodology is developed as asked for in Safety Recommendation A-10-112, the FAA require manufacturers of transport-category airplanes to develop type-specific, maximum-crosswind takeoff limitations that account for gustiness.

"The NTSB recognizes that implementation of the preceding recommendations will be a relatively lengthy process involving significant research, and, thus, will involve delays in the safety-enhancing benefits of the limitations. Therefore, the NTSB recommends that, until the actions described in Safety Recommendation A-10-113 are accomplished, the FAA require manufacturers of transport-category airplanes to provide operators with interim crosswind takeoff guidelines that account for wind gusts…."

Conclusions …
Findings …

13. … tower local controller followed established practices when he provided the accident pilots with the runway 34R departure end wind information with their takeoff clearance, he did not (nor was he clearly required to) provide information about the most adverse crosswind conditions that were displayed … therefore, the pilots were not aware of the high winds that they would encounter during the takeoff roll….

19. … simulator training did not replicate the ground-level disturbances and gusting crosswinds that often occur at or near the runway surface, and it is unlikely that the accident captain had previously encountered gusting surface crosswinds like those he encountered the night of the accident, the captain was not adequately prepared to respond to the changes in heading encountered during this takeoff.

20. Because there are no standards for the development of enhanced crosswind guidelines for transport-category airplanes, Boeing did not adequately consider the dynamic handling qualities of the Boeing 737 during takeoff or landing in strong and gusty crosswinds; it is likely that the enhanced crosswind guidelines developed by other manufacturers are similarly deficient.

4. Recommendations …

Once realistic, gusty crosswind profiles as asked for in Safety Recommendation A-10-110 are developed, develop a standard methodology including pilot-in-the-loop testing, for transport-category airplane manufacturers to establish empirically based, type-specific maximum-gusting-crosswind limitations for transport-category airplanes that account for wind gusts. (A-10-112)

Once a methodology as asked for in Safety Recommendation A-10-112 has been developed, require manufacturers of transport-category airplanes to develop type-specific, maximum-crosswind takeoff limitations that account for wind gusts. (A-10-113)

Until the actions described in Safety Recommendation A-10-113 are accomplished, require manufacturers of transport-category airplanes to provide operators with interim crosswind takeoff guidelines that account for wind gusts. (A-10-114)

Work with U.S. airline operators to review and analyze operational flight data to identify factors that contribute to encounters with excessive winds and use this information to develop and implement additional strategies for reducing the likelihood of wind-related runway excursions. (A-10-115)

= = /\ = = END Excerpt from AAR-10/04 = = /\ = =

View Status by Addressee
Response Date: 10/14/2010
Response:
CC#201000393: - From J. Randolph Babbitt, Administrator: The FAA is investigating these issues to determine whether an Airplane Flight Manual limitation and standardized mean/gust crosswind values, for use by airline operators, would be feasible and appropriate.

Last edited by IGh; 20th Sep 2011 at 16:32. Reason: Added FAA's initial response
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Old 20th Sep 2011, 22:48   #26 (permalink)

 
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The most x wind at a 90 degree angle that you can be assured of maintaining control-ability of the aircraft during take off and landing.

Certainly this number is well below the test pilot max numbers, given they have to assume a variety of pilot experience and ability, not to mention runway conditions, gusts, weight of aircraft, etc.
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Old 23rd Sep 2011, 01:25   #27 (permalink)
 
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whenrealityhurts re “…you can be assured of maintaining control…”
There is no such assurance in a max demonstrated crosswind; you have no idea how much margin there is from a limit condition – primarily because the manufacturer has not been there.
In addition the test only assumes an ‘average’ pilot, a task which does not require undue skill or strength – experience and ability are not defined. How do pilots judge themselves before a max crosswind landing, how many times have they done it before, and what is their currency? Not known, and often misjudged.
Furthermore, the manufacturer does not have to consider runway conditions, but most do now publish guidance for wet conditions. The manufacturers’ tests may not record the type of runway surface – lateral friction characteristics; this might affect the ability to stay on the runway; as might tyre conditons.
Also, the manufacturer may measure the wind speed with a more sensitive system than used by ATC, thus the ‘tower’ wind might be differ, and in operations the accuracy of wind reporting can be ‘significantly’ different.
Then there are gusts … !
See #10 to #13.
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Old 24th Sep 2011, 17:44   #28 (permalink)

 
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Safetypee - Obviously you don't have a clue on how they determine speeds, maneuvers, braking distances during the flight test process.
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Old 24th Sep 2011, 19:40   #29 (permalink)
 
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wrh

please give a specific example in the post by safetypee where you note an error allowing you to make that statement. I'm curious.

and, by the way, max demonstrated means precisely that - the maximum demonstrated value. no margin, no pad, no "test pilot extra", nada.
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