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Archive for the ‘Boeing’ Category

Approaching CrossWind Landings Without Being Crabby Or SideSlipping The Issue – IMRAN™

Posted by imrananwar on March 27, 2016

I love flying and I love being in the media. But I cringe when I see idiocy in news reporting of aviation topics.

One recent example was the otherwise decent news organization CNN posting a video of what was an excellent crosswind landing by a commercial airliner as “Airplane makes bumpy sideways landing” as if some major accident almost happened.

I wish my aviator & news anchor friend Miles O’Brien was around CNN to educate the idiots in media reporting on aviation, who can’t tell the difference between a well-executed high crab-angle (to compensate for strong crosswinds) landing and a bad bumpy landing.

These reporters would probably report a video of a chef doing a flambé dish as a dangerous kitchen fire almost destroying a home. Idiots!

But that raises another question that one of my followers asked me on my FaceBook post…. Why do pilots use crabbing, versus sideslip, when landing?

Like everything in flying, it is one of those topics that can bring out many different opinions that can even sometimes vehemently agree. Neither is perfect, one is preferred or at least recommended by airliner manufacturers like Airbus, though a combination of both is usually needed.

Keep in mind, I am barely a hobby pilot, much less some sort of aviation expert. But, this topic gets a lot of confusing responses. Only the high-wing versus low-wing debate gets people more riled up (which is just slightly less than the old Mac versus Windows flame wars! {Note: I STILL love MacOS and still despise Windows though it has become much less puke-worthy since W7)}.

Here is my explanation. Let me know in your comments if you agree, disagree, or have more insight to add. 

IMHO, as a perpetual student pilot, there are 2 primary ways to make crosswind landings.

Crabbing (nose pointed to the side but body moving in straight line along the runway centerline) appears “more scary” in videos like this but provides wings level. That is the recommended approach from manufacturers like Airbus.

The other option, Sideslip (or cross-control, with the nose pointed straight down the runway centerline) is the wing low approach, because one wing is lower as the plane is not wings-level.

More and more planes are designed with their control surfaces and engines seeming to be closer and closer to the ground.

e.g. Thanks to my late beloved father’s giving me experiences as a child most people even in developed countries did not have until later in life, I first flew in Pakistan International Airline PIA Boeing B707 (and later derivation B720) airliners as a 6-years old unaccompanied child in 1969, and many major airliners had 4 jet engines then and until much later.

As the designs moved to two much more powerful engines instead of four, their size and closeness to the ground also increased. So in modern planes the bank angle becomes a much greater issue to keep in mind to avoid striking the wingtip, engine, or even control surfaces on the runway.

However, neither approach may be enough to be used alone in strong crosswinds like 30 knots.

In a crab-only landing the crab angle of 10-15 degrees may not be de-crabbed quickly enough to avoid side-loads on the landing gear causing structural damage.

In a sideslip-only landing the 10-15 degrees of bank angle will most likely cause a runway strike. (These angles are given as examples for illustrative purposes only. Please check your own aircraft’s manuals for specific information).

So, in such situations the best pilots are likely using a combination of the two methods based on the plane, the airport, the runway, runway conditions (dry vs wet or contaminated), the approach speed, etc.

I hope that helps explain why we often see commercial planes using wings level crabbing approaches for typical crosswind landings.

Keep in mind I am a perpetual student pilot and do not even play a commercial pilot on TV. Feel free to add your thoughts in the comments below.

Enjoy the story of my aviation journey at: http://imran.com/adventure/flying/flyingnew.php 🙂

IMRAN

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