Flap Mechanism

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The Wag Aero Sportsman 2+2 is designed as a four place aircraft, however the “+2” refers to two children or one adult for the back seat. When determining the routing of the flap cables, consideration had to be given on the location of these cables to keep clear of the back seat passengers, thus a side mounted cable system was needed.  The flaps are engaged by pulling a Johnson Bar Lever between the front seats that pulls the cable that run down the centerline under the floorboards until they reach behind the baggage panel and are then directed upward and over to the right side of the fuse where they terminated to a pivoting bell crank.  The bell crank cable was attached to a “Y” connection from cables routed from each wing.  As my previous post described, I found that this cable geometry limited the flap travel and it was later greatly simplified by removing the bell crank and using only one cable from the Johnson Bar.  The return springs in the wings provided the means of retraction and are assisted greatly by the thrust of the airstream.

The Northstar Wing instructions advise to set the maximum deployment angle to 52 degrees down. While that seemed extreme, the actual angle was between 40 to 45 degrees when the air load was applied.  The Northstar flaps are massive and one difficulty is being able to pull on that much flap. Your airspeed is very important and the slower the aircraft, the easier it will be to get that last notch of flaps engaged. The larger wing area and the Fowler like flaps help the aircraft fly much slower, so it takes some getting use to  as when you can pull on that last notch of flaps.

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