Crab and Slip Landings - Maintenance Implications

[mriya225]

Dicussing the crab and slip landing methods for crosswind approaches in another online forum, has left me with more questions than answers. I know of no better place to get informed and reliable answers than here - perhaps you can help.
My concern is not the approach methods themselves, but rather, how the load stress factors for each method effects the torque arm linkages, downlock actuators and toe settings (on heavy jet aircraft landing gears). It would seem to me that a special inspection of these elements should be performed after such a landing; please advise.

Regards,
Mriya225

[BigJETS]

I would think so. I have heard that the 747 in particular, is designed for high-angle crab landing in crosswind (recommended by Boeing). Maybe it is perfected to the point that no inspection is needed?

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Rotate, Please! http://bigjets.tripod.com/flightline/

[This message has been edited by BigJETS (edited 26 July 2000).]

[For base attn]

With ref to the 747-4 Boeing req a high drag/side load landing inspection to be carried out if one of the following occurs.

The aircraft skidded or overran the runway.
It landed short.
It blew 2 or more tyres.
It skidded sufficiently for you to feel that damage occurred.

The inspections are comprehensive (wheels, shock struts, doors, trunion fittings, structure etc)& snowball if damage is found. Can't remember what Airbus req as haven't had to do one (yet)

As long as an aircraft is flown within flight manual limits no worries - keep em flying. As an aside I believe the 744 during autoland decrabs to zero degrees in stages. Once at 500' & again at 200'. Someone else may be able to enlighten you further.

[Mice]

Most of the side loadings at initial impact of a x-wind landing are taken by the tyre carcass itself, and are not heavy on the gear.
The gear is designed to take side loads of a certain magnitude, but most good operators I have seen get the a/c pretty straight immediately prior to touchdown anyway.
I have seen a film of the tyre deflections during severe x-wind landings, and it is quite informative to see the carcass deflection on touchdown. This is also apparent in side scrub of the tyre itself during pre-flight inspection on the line.
I am familiar with some Airbus types, and as per the 747, no special inspections are required in normal operation.

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When all else fails, read the manual!

[mriya225]

I appreciate the information (from all of you).

Cheers!
Mriya225

[Genghis the Engineer]

I think there's a point being missed here.

Either a crabbed or wing-down landing finishes the same way, one wing down, in sideslip, on the centreline. So they should give the same airframe loads (i.e. a one-mainwheel landing).

High sideloads only happen if the driver bolloxed up the landing and still had drift on when he touched down.

G

[mriya225]

Hey Genghis...
Does this mean I've been Khan'd??

...bolloxed up the landing, eh? I like that!I don't suppose it'd be a good idea to ask a pilot if he did that on windy days, huh? Pity - I'm dying to say it!

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It's cute, but...where are the fifth and sixth engines?

[ozone ranger]

Sorry I'm a little confused here.

On the B-727, the manual states the pilot (me) can touch down with the nose 15 degrees (I think, dont't have the manual at home with me) off runway heading in crosswind landings, still drifting sidways. I have done this more that a few times. This to avoid flaps hitting runway during stromg crosswind landings, 20kts plus.

I have always assumed (I know, I know, assume is spelled ass-out of-u-and-me)that will put a sideload on the gear, but that aircraft was built to handle such a sideload.

So how can one call a landing that the manual says is ok a pilot screw up.

So I guess my question is "What is sideload as related above?"


[This message has been edited by ozone ranger (edited 30 July 2000).]

[mriya225]

Hello Ozone Ranger,

The way I read the previous responses - you are all in various degrees of agreement. When Genghis referred to a "bolloxed up" landing - I ass-of-u-and-me'd he meant REALLY "bolloxed" http://www.pprune.org/ubb/NonCGI/eek.gif (as in: You beat the odds with that brain-dead approach, you're lucky to be alive! Now step aside while I take a count of how many rivets you blew on impact - you fool!) - that's loosely translated, of course.

I don't think anyone would argue your point - keep on keeping on! :)

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It's cute, but...where are the fifth and sixth engines?

[This message has been edited by mriya225 (edited 31 July 2000).]

[Genghis the Engineer]

With my Certification Engineer's hat on, Ozone Ranger is quite right. The undercarriage is tested to a given sideload - you can find the current airliner certification requirements at
http://www.jaa.nl/jar/jar/jar/jar.25.25.485.htm

and
http://www.jaa.nl/jar/jar/jar/jar.25.25.511.htm

You've sometimes no choice (depending upon lateral stability, and various other things) but to land with drift on - as you said the aircraft is rated to handle that up to a given limit.

G

[100LL]

Yeah but somtimes they do bollox it up,
think this is more than a few pulled rivets http://www.aeroweb.co.uk/humour4.htm
but im only a lowly LAE wannabee due tosit exams soon

[mriya225]

100LL - I dig your sense of humor!!



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It's cute, but...where are the fifth and sixth engines?

[QAVION]

"As an aside I believe the 744 during autoland decrabs to zero degrees in stages. Once at 500' & again at 200'. Someone else may be able to enlighten you further."

My manual reads slightly differently...

"At 500 or 200 feet radio altitude, depending on the magnitude of the crab angle, decrab control is added. If the crab angle is greater than 5 degrees, the decrab function starts at 500 fet and a maximum of 5 degrees crab is removed. If the crab angle is less than 5 degrees, the decrab function starts at 200' and all of the crab is removed."

So, if I have interpreted this correctly, not all crab is removed if the original crab angle is greater than 5 degrees.

Rgds.
Qavion.

[For base attn]

Qavion you have proved what I've known all along - the 744 is a darn sight more clever than me.............

[Cornish Jack]

QAVION
-400 cross wind auto-land kicks off the first 5 degs of drift and then uses forward slip for the remainder. Removal is as you say.

[vertical speed]

Whereas the 737 autolands without any rudder channel up to 15 knots crosswind-- can be interesting!