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Mysteries of Va, manuvering spped

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Va, manuevering speed, represents the maximum airspeed at which abrupt manuevers or full rudder deflection is permissible without risk of structural failure. Ok. But I read recently in the Jepperson Private Pilot manual that Va increases with aircraft weight. It states that in a heavily loaded aircraft, Va might be (say) 100 kts but in a lightly loaded aircraft it could be 90kts. This surpised me. I guess intuitively I thought g forces would be higher with a more heavily loaded plane and Va would be lower. What am I missing?

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>Va, manuevering speed, represents the maximum airspeed at>which abrupt manuevers or full rudder deflection is>permissible without risk of structural failure. Ok. But I>read recently in the Jepperson Private Pilot manual that Va>increases with aircraft weight. It states that in a heavily>loaded aircraft, Va might be (say) 100 kts but in a lightly>loaded aircraft it could be 90kts. This surpised me. I guess>intuitively I thought g forces would be higher with a more>heavily loaded plane and Va would be lower. What am I>missing?Hi, the definition of maneuvering speed you gave is common but it is not correct. The correct definition is "the speed at which the pilot can make a single application of full nose up control deflections without over-stressing the airplane."For example, if I recall correctly, the crash of the AA A300 taking off from KJFK on Nov 12, 2001, was found to be caused by continous and alternating left and right inputs to the rudder pedals, that led to vertical stabilizer separation below maneuvering speed.The maneuvering speed increases with aircraft weight just like stall speed: to have a max load of 1g (stall speed) I need faster speeds as the weight increases. Similarly, to have a max g-load of, say, 3g, I need faster speeds as the weight increases.More here:http://selair.selkirk.bc.ca/aerodynamics1/Lift/Page12.htmlMarco

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One of the best books ive read on aerodynamics is "Aerodynamics for Naval Aviators" http://www.asa2fly.com/product1.asp?SID=1&Product_ID=193&Va is based on limit load factor, say your g limit load is +3.8 gs and your airplane is lightly loaded today taking off at 2000#s, 2000 x 3.8 = 7600#s, next leg your plane weighs 3000#s, 3000 x 3.8 = 11400#s, the wing is going to produce 7600#s of lift at a speed well below the speed it will produce 11400#s of lift.

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I've never seen an easier to understand explanation than the one provided by Rod Machado in his PP manual. Here's the gist.1. Lift divided by weight equals load factor. So, for instance, if you have 2000 pounds of lift and 2000 pounds of weight you have a load factor (G-force) of 1. 2. If you suddenly (as in a sudden vertical gust) double (or triple) the lift you also double (or triple) the G-force.3. There is about a 1:1 relationship between AOA and lift. So, if you suddenly double the AOA you also double the lift and as we've seen above double the G-force.4. Normal category certification is 3.8Gs, utility is 4.4Gs and aerobatic is 6Gs.5. Most GA planes stall somewhere around an 18

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You may find it helpful to review the following:"Load Factors and Stalling Speeds" (p. 3-28ff) in the "Pilot's Handbook of Aeronautical Knowledge" (http://www.faa.gov/library/manuals/aviation/pilot_handbook/)You may also be interested in "The Myth of Maneuvering Speed," a column by J. Mac McClellan in Flying magazine (http://www.flyingmag.com/article.asp?section_id=12&article_id=527&page_number=1) and "AA587: The Perils of Flying by the Book" also at Flying magazine (http://www.flyingmag.com/article.asp?section_id=12&article_id=545&page_number=1)N.B.: The definition of "design maneuvering speed" now used by the FAA is "The design maneuvering speed is the maximum speed at which the airplane can be stalled or full available aerodynamic control will not exceed the airplane

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