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Demonstrated X wind a pointless figure ?

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Demonstrated X wind a pointless figure ?

Old 6th Feb 2016, 15:09
  #61 (permalink)  
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No, I don't think it is - it's rather subject to handling technique, and I'm not aware of there being any standard result for predicting crosswing limits on paper.

I think that what the manufacturers know is what their flight test department worked out.

G
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Old 6th Feb 2016, 15:19
  #62 (permalink)  
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G

But that is going to be relative to the day in question that the tests are carried out? How strong the winds that day, the direction, are they steady or gusting? If gusting to what factor? Shear conditions.

Do they take the aircraft up on a 40KT wind day decide what the limit is and then knock half of it off ? I am not clear how they arrive at those figures.
Others have talked about enough rudder authority to maintain the runway centreline yet when I think about it it is commonplace at FL360 in a small jet to track an airways with 100 KTS cross

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Old 6th Feb 2016, 15:26
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PilotDAR answered the OP pretty conclusively three pages ago, why the argument?

GF
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Old 6th Feb 2016, 15:51
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Tracking an airways doesn't use rudder at-all, regardless of crosswind component - that's just geometry.

Do conditions change things - a bit. But, you'll generally shoot for steady conditions, and I don't think that in the last 50 feet shear changes very much on a standard open grass + tarmac airfield.

The limit will either be the worst seen, or the point the test pilots decide it's become unviable (as I said, around CHR5.) And of course, anything based upon pilot opiinion is, to some extent, subjective - it can't not be.

G
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Old 6th Feb 2016, 16:15
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the idea of having castoring main wheels after a crosswind touchdown is a worse nightmare than anything I've ever dreamt.
I remember reading an article written by an engineer who was in the Tower in the 1950s, observing circuits and crosswind touchdowns on an airliner which had just been fitted with a new experimental castoring wheel system.

I can't remember the aircraft or any of the finer details, except that he said it had been one of the most hilariously entertaining interludes of his life.
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Old 6th Feb 2016, 16:49
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Light aircraft such as the Beech 18, Stinson 108, Cessna 180 and this Piper Cub were fitted with experimental X-wind landing gear:

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Old 6th Feb 2016, 16:57
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..and of course, the Boeing B-52 left the factory with a landing gear capable of being dialed in with a 20-degree crab:
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Old 6th Feb 2016, 18:09
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Others have talked about enough rudder authority to maintain the runway centreline yet when I think about it it is commonplace at FL360 in a small jet to track an airways with 100 KTS cross
G
didnt actually say that rudder authority kept the aircraft tracking a fixed line airways but can see how you read that from the post ))

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Old 6th Feb 2016, 18:55
  #69 (permalink)  
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I did wonder if you'd just had a bit of a brainstorm!

G
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Old 6th Feb 2016, 21:44
  #70 (permalink)  
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Sometimes I wonder whether rather than demonstrated the test pilot asses the aircraft ability to handle crosswinds and instead uses a grading from Good to medium good to average to medium poor or poor and not fix an out of the hat number at all
Every time I have flown a flight test to demonstrate directional control, I have actually flown the aircraft in the 0.2Vso required crosswind, or greater. I could not state that the design requirement continues to be met, if I did not demonstrate that during a flight test. This has involved flights as long as an hour to fly to a runway with proper wind measuring equipment, and the required value for the day. I don't pick the wind speed to be tested to (and the resulting statement for the flight manual supplement, it will be 0.2Vso.

It is not a level of difficulty thing, either I could control the aircraft in that wind, and keep it on the runway with normal use of the flight controls, or I could not - it's pass or fail. If fail (which I have not personally experienced), a change in the rudder might be required. This has been done with Cessna 206, for example, with the installation of certain STOL kits or float kits.

I expect that a pilot who is of average skill on an aircraft, will at least do the aircraft the honour of using full control application if needed to maintain control. So if I can maintain control using full rudder on the runway, I will expect that an average skill pilot will be able to as well! When I was trained in the turbine DC-3, the training pilot specifically instructed me preflight, to roll the control wheel left and right its full travel, just so I was reminded that it goes nearly one whole turn around stop to stop. I expect that he expected me to use full aileron if needed, without being instructed to do so at the moment by him.

I recall only two occasions where I ran out of control during a crosswind landing. One was a Piper Arrow I, and the other the prototype Zenith 701. In both cases, I ran out of aileron on short final, and elected to not continue the landing. Neither was a formal flight test for crosswind capability.

As for test pilot super skill on a type during testing, perhaps some, but not me. Excepting only a C 172, I have never flown a crosswind test on an aircraft type in which I had more than 100 hours total flying experience at the time. Thus, I would rate my skills on that type as "average" for the purpose of that testing. In most cases, I was flying the test with only a couple of hours on type. I'm not offered the luxury of amassing hundreds of hours on a new type before testing it, rather I insist on an hour or two to get familiar (which is usually during more mundane testing anyway).

I do myself the favour of not attempting the crosswind test in very gusty conditions, that is not required for certification, why make it difficult for myself?

I have never flown a plane with "crosswind gear". Any I've known of have either been de-modified, or had the system locked out. I guess that there's a message in that! If it were a good idea, we'd be seeing them in service!
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Old 6th Feb 2016, 23:55
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I have never flown a plane with "crosswind gear". Any I've known of have either been de-modified, or had the system locked out. I guess that there's a message in that! If it were a good idea, we'd be seeing them in service!
The only airplane I ever flew with x/wind gear was a DC3, it was really easy to land with a strong x/wind once you got used to approaching and landing with the airplane pointed at an angle to the runway.

It was sold to another operator ( Keir Air Transport in Edmonton. ) who changed it back to normal gear and gained 1600 or maybe 1800 pounds of payload....my memory is vague as to the exact weight saved.

Bottom line is the x/wind gear really did work, however the DC3 is so easy to fly if you needed x/wind gear you really should not fly period.
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Old 7th Feb 2016, 11:17
  #72 (permalink)  
 
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Others have talked about enough rudder authority to maintain the runway centreline yet when I think about it it is commonplace at FL360 in a small jet to track an airways with 100 KTS cross
Also not a lot of side loads on the undercarriage to worry about here! Seems a bit of a strange, irrelevant, comment to put in the discussion, especially for a pilot with your experience!
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Old 7th Feb 2016, 13:06
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Others have talked about enough rudder authority to maintain the runway centreline yet when I think about it it is commonplace at FL360 in a small jet to track an airways with 100 KTS cross

Pace: Did you really mean to say this!!!!?
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Old 7th Feb 2016, 14:46
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Pace
Others have talked about enough rudder authority to maintain the runway centreline yet when I think about it it is commonplace at FL360 in a small jet to track an airways with 100 KTS cross
I think you have just had a brain fart.
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Old 7th Feb 2016, 15:30
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Pace is a perfectionist. He likes to track the airways with the fuselage perfectly aligned with the centreline.
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Old 7th Feb 2016, 18:50
  #76 (permalink)  
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I was purely pointing out not in a very clear way obviously that tracking a runway centre line from way out with the aircraft high on approach is no different to tracking say a VOR radial with a strong side wind so maybe a rubbish point to make )) got to do something to keep the thread alive ))

But if you want to beat me up over it ))

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Old 7th Feb 2016, 22:12
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I was only joking Pace.
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Old 7th Feb 2016, 22:25
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At the risk of being a pedant (or thick or both) again!

I was purely pointing out not in a very clear way obviously......
After an immediate double-take I got that but , with all due respect, what then, DOES this mean, in the context of x-wind landings?

If you cannot hold the runway centerline during final approach, completing the landing may be difficult.
I am a newbie PPL.

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Old 7th Feb 2016, 22:33
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If I may presume to reply in the absence of the original writer, I think that what was meant was that if it was not possible to maintain the extended centreline whilst making an unbalanced wing down approach (I.e. not a balanced crabbed approach) without being blown off to one side, then unless the crosswind component diminishes in the flare and hold off (as is often the case) then the final outcome is unlikely to be a success.
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Old 7th Feb 2016, 23:59
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"MAX demonstrated" says it all. => No point in discussing that.

But.... Flying does NOT STOP at landing.

With some taildraggers, I have been able to land well above the demonstrated MAX crosswind component just to find myself stuck on the runway. There was often no safe way to taxi back.

Landing is always somewhere "into" the wind with a crosswind component.

To taxi back, you have to turn around and taxi with a tailwind.
Some taildraggers, really, really do not like to taxi in strong tailwinds.
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