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#1




Vn Diagrams
I have been playing around making Vn diagrams for the various airplanes
I rent from my flying club. I made one for our P28T201RT and was looking for the numbers on the PA32300. The one item for the PA32300 that would not follow the formula for calculating the lift line was Va. The book shows it as 132 kias, but the formula generates a speed of 103 kias for the intercept of the 3.8 load limit line. Can anyone explain this discrepancy? It is interesting to note that Piper does not allow any negative maneuvers in the Normal catagory, on 3.8 positive. (Cessna does, 1.52. Another reason to own a highwing! ;))) Another interesting item was that both have a Vne of 192 kias and Vfe of 108 kias. 
#2




john smith wrote
The one item for the PA32300 that would not follow the formula for calculating the lift line was Va. The book shows it as 132 kias, but the formula generates a speed of 103 kias for the intercept of the 3.8 load limit line. When is 3.8g not 3.8g? When it is 4.5g or some other number. Remember, 3.8g is a minimum figure for the normal category. I have seen VN diagrams for aircraft where the 3.8g line was extended upward to accomodate the gust loading envelope at Vno. Observe the gust envelope in the diagram at this web site: http://adg.stanford.edu/aa241/structures/vn.html It is interesting to note that Piper does not allow any negative maneuvers in the Normal catagory, on 3.8 positive. This is contrary to the required limits in FAR 23 Bob Moore 
#3




The load limit for normal catagory isn't always 3.8G. In a 747 it is around
2G and a MU2 is 3.25G. Mike MU2 "Bob Moore" wrote in message . 6... john smith wrote The one item for the PA32300 that would not follow the formula for calculating the lift line was Va. The book shows it as 132 kias, but the formula generates a speed of 103 kias for the intercept of the 3.8 load limit line. When is 3.8g not 3.8g? When it is 4.5g or some other number. Remember, 3.8g is a minimum figure for the normal category. I have seen VN diagrams for aircraft where the 3.8g line was extended upward to accomodate the gust loading envelope at Vno. Observe the gust envelope in the diagram at this web site: http://adg.stanford.edu/aa241/structures/vn.html It is interesting to note that Piper does not allow any negative maneuvers in the Normal catagory, on 3.8 positive. This is contrary to the required limits in FAR 23 Bob Moore 
#4




"Mike Rapoport" wrote
The load limit for normal catagory isn't always 3.8G. In a 747 it is around 2G and a MU2 is 3.25G. Too early for you Mike? :) 747s aren't certificated in the Normal Category...how about the Transport Category? Bob Moore 
#5




Bob Moore wrote:
john smith wrote The one item for the PA32300 that would not follow the formula for calculating the lift line was Va. The book shows it as 132 kias, but the formula generates a speed of 103 kias for the intercept of the 3.8 load limit line. When is 3.8g not 3.8g? When it is 4.5g or some other number. Remember, 3.8g is a minimum figure for the normal category. I have seen VN diagrams for aircraft where the 3.8g line was extended upward to accomodate the gust loading envelope at Vno. Observe the gust envelope in the diagram at this web site: http://adg.stanford.edu/aa241/structures/vn.html Yes, where the lift line intercepts the 3.8 load limit line is Va. Some Vn diagrams then show another linear lift line extending from the load limit line to Vno linearly back down then back down to Vne line. Va=(33*sqrt(wing loading)). But for the PA32300 this calculation yields 145 kias, higher than book value, 132 kias. Vno is 149 kias. For other aircraft the formula and book values coincide, but for some reason, the PA32300 numbers do not. I have been using this formula to generate the lift line: n=(V/Vs)**2 then plotting n (yaxis, rise) against V (xaxis, run) It is interesting to note that Piper does not allow any negative maneuvers in the Normal catagory, on 3.8 positive. Should read "... only 3.8 positive." 
#6




Bob Moore wrote:
The load limit for normal catagory isn't always 3.8G. In a 747 it is around 2G and a MU2 is 3.25G. Too early for you Mike? :) 747s aren't certificated in the Normal Category...how about the Transport Category? Must not have to know that for the ATP rating. :)) 
#7




Well it is pretty early here...MU2 is normal catagory though
Mike MU2 "Bob Moore" wrote in message ... "Mike Rapoport" wrote The load limit for normal catagory isn't always 3.8G. In a 747 it is around 2G and a MU2 is 3.25G. Too early for you Mike? :) 747s aren't certificated in the Normal Category...how about the Transport Category? Bob Moore 
#8




"john smith" wrote in message ... Bob Moore wrote: The load limit for normal catagory isn't always 3.8G. In a 747 it is around 2G and a MU2 is 3.25G. Too early for you Mike? :) 747s aren't certificated in the Normal Category...how about the Transport Category? Must not have to know that for the ATP rating. :)) Fortunately for me! Mike MU2 
#9




Mike Rapoport wrote:
The load limit for normal catagory isn't always 3.8G. In a 747 it is around 2G and a MU2 is 3.25G. Too early for you Mike? :) 747s aren't certificated in the Normal Category...how about the Transport Category? Must not have to know that for the ATP rating. :)) Fortunately for me! Sorry Mike, I hit the send key too quickly. I am reading a paper about "Radial G" and the next paragraph is: "By the same logic a large aircraft certified under FAR 25.337(b) with the minimum allowed limit load of 2.5 would be restricted to a 1.65g rolling pull up. To keep things in round numbers, the "rolling" Va, as calculated for the aircraft weight, would be about twenty percent less than the symmetrical Va." 
#10




"Mike Rapoport" wrote in message k.net... The load limit for normal catagory isn't always 3.8G. In a 747 it is around 2G and a MU2 is 3.25G. 3.28g for the TC 690/695 series as well. Tom 

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