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Cross wind landings

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Cross wind landings

Old 22nd Feb 2006, 12:20
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Originally Posted by john_tullamarine
I can recall a quite nice line of singles which came on the market quite some years ago. The demonstrated crosswind was quite low (15 -16 kts or so as I recall) and we redid the certification for the crosswind limit. This particular design had an interlinked aileron/rudder and we ended up deciding that discretion was very much the better part of valour at around 18-20 kts if memory serves me correctly .. that few knots increase definitely presented some limitations for handling in the landing flare and roll out.
Sounds like the Mooney 201 and friends, introduced around 1980. The max demonstrated is 11 knots (exactly 0.2 Vso). I also remember 17 knots as being the number that stuck in my mind as delimiting the routine from the ... interesting landings. Crosswind take-offs were challenging too.
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Old 22nd Feb 2006, 18:00
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I think FFF is on the right track here.

I always ask (or state myself) whether people are going to use the 'wing down' or 'crab' technique if we are going to experience a serious x-wind component, as it saves me a short period of uncertainty as we approach the runway.

I have to say that 99% of those who 'crab' are, in fact, using the 'very late wing down' method, much as FFF has described. I also agree that the perfect 'crab' landing involves achieving alignment of the centreline of the aircraft with that of the runway, at the moment of touchdown (the process having started shortly before). After touchdown the wings are level, being kept that way by an appropriate amount of into-wind aileron.

I have to say (and this is personal to us all) that I prefer the 'wing down' approach as it is stable and you don't have to guess where the main gear (or nose gear, depending on how you fly) is going to end up. Also, showing my yellow streak, if you are running out of control at 200' with the wing down, you get a chance to throw it all away earlier than when you start drifting onto the grass at ten feet...
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Old 22nd Feb 2006, 21:13
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FFF and Fullwings,

Why do you mention that most crab landings are actually a combination of both crab and wing down methods. This is not true. As you straighten up using rudder you also use opp aileron into wind, however you touch down with both main wheels and with the wings level.

The main disadvantage of the wing down method is that the pax will be uncomfortable during the approach, leaning over to one side seems crazy to me.

Crosswind take offs are more limiting and demanding anyway, although most people thing the landing is the most difficult. its not.
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Old 22nd Feb 2006, 21:48
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Marsman,

Impolite sentence deleted .. keep it nice, chaps ...

You will only touch down wings level if you kick the drift off at exactly the right time, otherwise you will need a small amount of wing down. This is basic PofF. Nobody can repeatedly get this right. Neither method can ASSURE a wings level touchdown unless you never kick the drift off which I strongly recommend against. It twists the gear and even on a modern jet will result in a very uncomfortable feeling. (I've been there!)

Last edited by john_tullamarine; 22nd Feb 2006 at 21:59.
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Old 22nd Feb 2006, 21:54
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marsman: FFF and Fullwings are closer to the mark about what actually happens with most attempts at crab landings- whether intentionally or not. This is particulary true of the majority pilots. However the initial intention is for the landing to result both main wheel touching down at the same time, tracking the runway centreline.

Regarding my earlier post supercruise593 is correct regarding the "kick straight" part, after the initial "kick" most students would try and land normally, then wonder why the squeeling was occuring, as the aircraft weathercocked back into wind, and landed sideways.
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Old 22nd Feb 2006, 22:24
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Scoogee,
What say is perfectly correct however I dont believe this is repeatable several times in a row. The only way for the 'average' pilot to get the a/c on the ground is to use 'very late wing down' as described previously. This is not therefore a wings level landing. The only way to land wings level is with no x-wind or complete luck-FACT
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Old 25th Feb 2006, 08:47
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Q. Why does a B747 have 4 sets of main undercarriage units?

A. Because it needs them to acommodate the aircraft weight, particularly during Landing.

Q. Would it be advisable to use only one quarter of the undercarriage units to absorb the landing load?

A. NO!

You figure out the rest, and the preferred landing technique

Regards,

Old Smokey
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Old 1st Mar 2006, 01:51
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OS -- The 4 sets of 747 MLG bogies are there for takeoff and aborts at max weight. Landings, generally at half the weight, can be done on just the body or wing gear -- although a landing on just the body gear is best done with a minimal crosswind.

There is considerable vertical travel on the wing gear oleos; however, the limiting factor in bank is the outer engine pod.

Also the rear axles of the bogies hang down; so, there is a complex gradation of weight transfer from lift to the gear as the various axles and bogies come into contact and the oleos compress.

Bottom line is that the first gear contacting the runway does not immediately assume the entire landing weight -- assuming a reasonable descent rate.
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Old 1st Mar 2006, 07:07
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Originally Posted by eire757
Scoogee,
What say is perfectly correct however I dont believe this is repeatable several times in a row. The only way for the 'average' pilot to get the a/c on the ground is to use 'very late wing down' as described previously. This is not therefore a wings level landing. The only way to land wings level is with no x-wind or complete luck-FACT
Agreed... in a lighty. However in a heavy, kick the rudder in around 100ft to 50ft AGL and keep the wings level or with a VERY slight wing down. The inertia of the aircraft will maintain centreline and you won't have a pod strike.
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Old 1st Mar 2006, 12:03
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RatherBeFlying,

I read loud and clear where you're coming from, and agree with you.

The intent of the suggestions implied in my post was that it's always preferred to not take any part of the aircraft all of the way to it's limits (e.g. allowing one set of landing gear to do the work of four), hence the use of the words "advisable" and "preferred" in my post.

Regards,

Old Smokey
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Old 2nd Mar 2006, 20:42
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As a student my instructor insisted I use, what has been described here as the ‘combination’ xwind landing method. His view on a ‘wing low’ approach was “Why cross your controls and increase your stalling speed when you are already low and slow?”
I have read this thread with interest but have not seen any mention of this.
He did eventually teach me both, but always warned me to keep my approach speed a little higher when making a ‘wing low’ approach compared to making a ‘crabbed’ approach.
Was he wrong?
Regards,
W.B.
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Old 2nd Mar 2006, 21:35
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Neither type of approach is "wrong" or "right." Use which ever you feel comfortable with and which is sensible for the type you are flying.
Most jets with underslung engine pods aren't very good at wing down. It tends to get expensive very quickly! A Cessna is a bit more forgiving.

One question for everyone. Why is the demonstrated cross wind limit on the 152 and 150 different?

Could it be due to the difference in techniques of the test pilots? Answers on a postcard.
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Old 2nd Mar 2006, 22:43
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Try landing any of the Cessna Tailwheel types without applying sufficient into wind aileron. Crossed controls are the order of the day for almost all landings except nil wind conditions.
Transition from crab to wing down is a must, and is called the combination method. If you do not roll in aileron and apply opposite rudder, you will surely start to drift.
One advantage tailwheels types do have, is that they can be held on at any speed. It is quite possible to hold them on at 100kts, although it is a bit hard on the gear. With a X-wind at the higher speeds, you would still have to hold into wind aileron and opposite rudder to maintain your line without drift.
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Old 3rd Mar 2006, 03:04
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Wing down Vs crab? It's down to what you've been tought and what you're used to. I once checked out in a school in the States prior to renting an aircraft. The CFI insisted I did the wing down method as that is what his school did and 'it was superior'. After cocking up a couple he declared that 'I had obviously never flown taildraggers' (actually I had about 1500 hours on them) so I demo'd a perfect crab method on the other runway with 25 knots of cross wind. He conceded.

Also, what id a limit? If you look at a lot of aircraft's POH (esp American ones) the crosswind is a 'max demonstrated cross wind', in otherwords it's the maximum the manufacturer has tested to. It's up to the operator what he does with that limit - whether he want's to treat it as a limit or not. I flew a very large jet with two companies. One treated it as an absolute limit, one left it to the pilot's discretion.
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Old 3rd Mar 2006, 04:15
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Dan, I agree that
demonstrated crosswind component
is not an absolute by any stretch of the imagination.
There is a time and place for each method of dealing with X-winds. I use either as required in the 185.
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Old 3rd Mar 2006, 08:12
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Sorry for the SLF intervention,
just found this link in the spotters forum, nice demonstration of crosswind landings
http://www.youtube.com/watch_fullscr...ind%20landings
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Old 3rd Mar 2006, 11:23
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Listen, look, emulate, learn (hopefully)

KR quote:
'Keygrip however, I do not like your patronising tone a great deal, there really is no need.'

If Keygrip is who I think he is then he's the best instructor/examiner I've ever flown with, bar none. In any case he was just trying to give you some advice which will save you breaking an aeroplane, boosting all of our insurance costs and preserve what seems to be an unjustifyably large ego intact.

To (miss)quote another aviation guru ' most common cause of a broken (aeroplane) is to have been talking when you should have been listening'..... Hope this helps.

PF

PS I find that most students in both gliders and aeroplanes seem to get the combination technique quite quickly - i.e. crab + a touch of wing down in the flare etc. The wheel doesn't take all of the weight because the wings are still producing lift. When wing stops producing lift you loose aileron authority and the other wheel gently touches the ground- evey time. Works on taildraggers and twins too. Admitedly I've never tired it in a 747, or at 90 kts.
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Old 3rd Mar 2006, 13:05
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Originally Posted by Bookworm
Sounds like the Mooney 201 and friends, introduced around 1980. The max demonstrated is 11 knots (exactly 0.2 Vso). I also remember 17 knots as being the number that stuck in my mind as delimiting the routine from the ... interesting landings. Crosswind take-offs were challenging too.
Bookworm - I was thinking the same thing as I was reading John's post.

If I remember correctly, your aircraft was a later J. Out of interest - was the 17 knots transition level with full, half or zero flaps? Did you have any personal guidelines for how much flaps you'd use with different levels of crosswind?
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