Old 07-09-2023, 07:13 AM
  #15  
1wife2airlines
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Originally Posted by JohnBurke View Post
Boeing (and MD, before) has been deadset against landing the MD11 in a crab or with any sideload, understandably so. The 747 has had guidance for decades to go ahead and take the crab rather than fight the mass close to the ground or risk striking an outboard nacelle. I forget the number, but the MD11 can take about 12 degrees of bank before a strike with full strut extension, but only five when fully compressed...so it needs to be landed flat.

Just recently Boeing revised their position and came out to say it's better to land crabbed than to cause any instability in the flare or risk getting into an oscillation in the flare. The MD, perhaps more than any other aircraft, is particularly subject to problems in the last 50' of altitude when landing...most of the losses have occurred there, and it has one of the highest loss rates for any transport category aircraft type. Consequently, the landing is a fairly critical time, and of that, the point from 50' to touchdown represents the moment that determines success or crash (everything else is set up for that, and in all the business we practice stable approaches. It's just that on the MD-11, it can be a perfectly stable approach, lost in the last 50').

Sideloading the gear is never preferable, but all things being relative, it's preferable to throwing a wing down, especially on airplanes with pods or nacelles below the wing. It's common to "kick out" the crab and make a transition in the flare, but on the more sensitive types, it can also destabilize the landing, and in some cases, it's preferable not to go there, or visit with great caution.

I realize the discussion is specific to the Challenger, but it's run somewhat afield into a discussion of crosswind technique. Let's not even get into a talk about conventional gear.
"Kicking out the crab" is just applying rudder to align with the runway. As you do that the upwind wing will rise so you apply aileron to keep wings level or maybe put that wing down a little. It's just a slip in the flare. It's worked for me in the 767 and smaller, even the T-38 which was designed to land in a crab but can be decrabbed the same way.
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