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Sidney Schwartz

Am I too crabby?

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I just finished a flight into KBNA in a Mike Stone 727. We landed R31. Winds were 340 at 11. The autopilot maintained a steady crab angle of about 15 degrees. Screen shots here....http://sidneyschwartz.homestead.com/temp.html/The little white triangle on the glareshield marks the centerline of the panel...that's normally what I would line up with the centerline of the runway in a no-crosswind landing.Not being a pilot--much less a 727 pilot--I have no idea if this crab angle is realistic or excessive. I wouldn't think that an 11 knot crosswind at 30 degrees would have such a pronounced affect on a big ol' plane like that. Is that the way it really is?Sidney Schwartz [KPDX]MyTraffic/Radar Contact/FSMeteo/FSSE/FSassist/FDC

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Just elaborating a bit, the size of the aircraft isn't a factor here -- what counts is your speed. The faster you fly the less will a crosswind component knock you off course. Since you're flying relatively slow on final the crosswind component will have a greater effect than during cruise. At any rate, you set whatever heading "into the wind" that it takes to keep you on course. Even though it's called "crabbing" the plane is flying perfectly straight relative to the air. (Think of the aircraft as a fish swimming straight ahead within a moving body of water -- it won't know that there's a current unless it has to relate to the seabed which is not moving). So, crabbing is just a heading correction to compensate for wind drift. Relative to the ground, however, you are indeed "crabbing". Actually, if there's a headwind component to the crosswind you'll need to set a higher crab angle since it'll take you longer to get to the airport (lower ground speed) and the crosswind will affect you longer. Put more eloquently, when you make less headway (forward movement relative to the ground) the crosswind component will constitute a greater part of the total movement. Then, when you're about to touch down you'll need to "uncrab" by kicking rudder and bank slightly into the wind. This is the tricky part -- getting the plane lined up with the runway at the last moment. If you get it right the wheels will touch and provide grip and traction before you start drifting off course.best regards,Hans Petter

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Thanks Hans and Matthew for the replies. Flying virtual planes has given me a great deal of respect for the folks who fly the real ones :-). Sidney Schwartz [KPDX]MyTraffic/Radar Contact/FSMeteo/FSSE/FSassist/FDC

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