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Fast approach in gusty weather...

rstark
Adventurer B
Fast approach in gusty weather... 

From a frequent flier: While landing in gusty winds it looked like we were going way faster than normal. We floated way down the runway and then pounded on the runway after which the pilots slammed on the brakes! Why would this happen?

Without any winds, the aircraft flies at basically 1.3 times the stall speed. (Stall speed is the speed at which  the wings essentialy "quit working" and lift would diminish rapidly.) When you have winds and gusts, we take half of the steady state winds and then add the gust component up to a max of 20 additional knots. That number gets added to our approach speed. Flying "plus 20" looks faster if the winds are mostly crosswinds. With headwinds, they usually average out. When the wing gets down to an altitude of half of its wingspan it enters ground effect. That reduces tons of drag on the plane as it travels through the air. Now, add 20 knots, and you have a plane that wants to float and float and float... At some point you have to stick it on the runway and that appears to be what you experienced. Maybe the Pilot was trying to "flare it on" when in retrospect, he or she could have flown it down to the ground (often yielding a smooth landing). Or, sometimes you can fly final in smooth air and get hit with a big gust that adds lift and makes you float. Either way, brakes only work on the ground so getting the plane stopped is only possible once it has landed. Float a little too far, and that means firmer braking to get the plane stopped.

 

Either way the Pilot played it safe and got the plane on the ground so he or she could get it stopped.

6 Comments
David37
Explorer C
Interesting! Very good explanation of the science going on there.
Avid_SWA_Flier
Explorer C
There would have come a point at which the pilot would have had to abort the landing and go around again. Clearly, the flight crew agreed that there was sufficient runway to get the plane on the ground and bring it to a slow enough roll-out to get off the active runway. Another reason for the hard breaking can also be that the best place to exit the runway was coming up and to avoid traffic on the runway (preventing other planes from using it) the pilot worked to get off as quickly as possible. Strong and/or gusty winds, are unpredictable and can cause moment-by-moment changes in flight management. Even though the pilot can aim for a landing spot on the runway, he or she will have to fly with the actual conditions in the air, not according to where they want to land. Finally, the key to landing is airspeed, not ground speed. The pilots manage airspeed, then need to deal with whatever ground speed they've got once they touch down. I'm sure anyone in a plane will agree that dealing with slowing down on the ground is far preferred to not moving through the air fast enough to stay in the air.
RD1
Explorer C
I fly back and forth from San Jose to Las Vegas (live in Vegas, work in San Jose). Vegas has some gusty and strong winds. Approach McCarren is always fun to me (especially on a Friday with a plane full of party people). Sometimes it gets very quiet - that's when I have the most fun! I am always impressed on the landings. Sure, once in a while it feels like "we just attacked" Las Vegas, but with 50 mph gusts, I can only imagine how difficult it must be to get that bird down onto the runway. The description above describes the physics and science behind it. Thank you for explaining this in simple terms and thanks for always getting us to the ground safe.
chuchoteur
Adventurer B
Also, modern aircraft have safety systems to prevent spoilers/thrust reversers from inadvertently deploying in flight. A "firm" landing allows the aircraft systems to identify that it is on the ground, enabling optimal braking/thrust reverser/spoiler deployment. A firm contact will also mean optimum grip on the runway, which in contaminated conditions (such as standing water) will help prevent the aircraft from aquaplaning. If the correct conditions are not met, the pilots will choose to "go around". The crews will have briefed the procedure during the approach, and it is the "failsafe". A lot of pilots actually refer to a landing as a "rejected go-around"!. hence, if you go back up, you should not be worried :o) (personally, I see it as a second opportunity to check out the scenery!) :o))
Anonymous3943
Explorer C
I was flying SJC-PHX and during our descent a mircoburst formed over the airport. I was sitting in the way back (to avoid the Monday morning commuters). It was one heck of a ride in back. Suddenly I just got sucked into my seat and we climbed. After circling for a few minutes we ended up at a regional airport to wait out the storm. It was certainly an adventure, but I felt very safe in Southwest's hands.
wordtrix
Explorer C
Oct. 29, 2008 Southwest Airlines P.O. Box 36647 - 1CR Dallas, Texas 75235-1647 Re: Oct. 18, 2008 Dear Sir/Madam: On Oct. 18 I arrived at Love Field, having come from Illinois, visiting my sister who has cancer. A passenger on my flight misdirected me to the basement when I inquired as to where to pick up my luggage and when I tried to come back through, an airport employee helped me back through the security checkpoint. Unfortunately, TSA nabbed me and informed me that I would have to go back and walk all the way around the airport outside till I found Baggage Claim myself, but they would not help me find the area. By this time, having chronic asthma, I began having an asthma attack due to anxiety. Extremely upset, I found myself in the Southwest employee parking lot and it was only there that a female SW employee, seeing that I was crying hysterically and was distraught, walked up to me and offered to help. I wish I had gotten her name that night but perhaps you might post this letter on a bulletin board or somewhere where she might see it and realize how much she helped me. She personally drove me around to Baggage Claim, allowed me to use her cell phone to call my friend who had been waiting for me for 30 minutes, spoke to two police officers outside Baggage Claim about my situation, and saw to it that I found my waiting friend before leaving me. I just wanted you to know how much I appreciated her kindness and that it really amazed me how she went out of her way to sympathize and help with my situation. I doubt any of the other airlines I’ve flown would have gone above and beyond the call of duty as she did. Wherever, you are, Miss Southwest Employee, thank you from the bottom of my heart and please know that you truly made a difference in someone’s life that night. Sincerely, Terri Rimmer Fort Worth, TX TDR