Crosswind Landings

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smhusain_1
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Joined: Sat Jul 19, 2008 1:16 pm
Location: Brampton, Ontario, Canada

Crosswind Landings

Post by smhusain_1 »

I have only heard of crabbing into wind as the desired method of approaching a runway for a crosswind landing in a commercial jet aeroplane, and after flare, aligning the longitudinal axis with the runway centreline by application of the rudder and opposite aileron if necessary if the wing drops. If any different technique is used for heavy jets, please continue with this input.
Another technique such as the wing down method with opposite rudder application is the favoured method for light aeroplanes.

Correcting the speed bug or Vref plus headwind component is also very controversial when gusts are affecting the wind velocity. In PIA we used 1/2 of the headwind component plus full gust as the addition to Vref. However, this does not apply universally here in North America as only the gust component is added to the Vref for business jets.

In Close and Gusty by Ross Detwiler, Business and Commercial Aviation Magazine Oct 2010
"We all know to increase airspeed in gusty potential wind-shear conditions. But the question is how much? When experiencing a large and abrupt decease in airspeed, the ground speed stays constant.
If an airplane has a normal approach reference airspeed of 120 kt and is flying into a 20-kt headwind, its ground speed is 100 kt. If that same airplane loses 20 kt of airspeed due to sudden decrease of 20 kt in the headwind, it loses no groundspeed. Even though the airspeed has decreased to 100 kt, the aircraft is now flying into a zero wind, which results in a 100-kt groundspeed. This doesn't mean that nothing is wrong. Airplanes fly based on airspeed, not ground speed. Airspeed should be increased until the groundspeed is equal to the desired reference speed of 120 kt. When flying into a 20 kt headwind, that will result in an airspeed of 140 kt. When the airplane suddenly loses the headwind, it would be flying at airspeed of 120 kt, the normal reference speed. Using this procedure, if a shear is encountered, care must obviously be taken in the application of the required back pressure, but the point is that there will be enough airspeed left to make the required correction without stalling the airplane."

In a landing accident of a Gulfstream business jet ( Global 5000) with a weight of around 77,000 lbs on Nov 11, 2007 at Fox Harbour Aerodrome, Nova Scotia in Canada on a runway 4500 feet long and served only by a APAPI, the aircraft undershot runway 33 by seven feet and six inches. The captain adopted the wing down method for cross wind correction and continued in this manner even after flare to correct for the crosswind, stretching the glide by not adding power as the auto throttles came off at 35 feet. He also used an incorrect Vref by not sufficiently correcting for the wind of approximately 18 Kts headwind and gusting to 25-30 Kts. Vref was corrected to only plus 5 kts for the wind. The accident did not result in fatalities but the aircraft was destroyed.

The investigation accident board however took the view that the eye to wheel height at touchdown mattered and few crew are aware of that. The eye to wheel height is when the aircraft is in the landing attitude and not in the horizontal plane sitting on the runway as is commonly thought. Also the APAPI glideslope was incorrectly aligned by a .04 degree from the classic 2.5 degrees. Previously the crew flew the Cessna Citation series which has a lesser eye to wheel height.

This accident is covered in B & CA of Sept 2010.