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GrassStripFlyBoy

Flap & Speed - T/O & Landing Distance

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It's Movie Night!  Here's the runway camera footage of today's flap & approach speed trials.  Appears the 15/30/40 degrees for take off all break ground about at the same distance.  Approach speeds coupled with the flap settings combine to make sizable differences in landing distance.  In very rough numbers, it's probably not a stretch to say each extra knot of airspeed is adding 100' to your landing distance.

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This is good work Darrell. Thanks.

Most interesting for me was your observation that more flaps, beyond 15 degrees, doesn't noticeably shorten the takeoff ground roll. I understood this to be the case, but you proved it.

As for the landings; excess speed is probably playing a greater role than the flap settings themselves. I think the CTSW manual only gives stall speeds at -6, 0 and 40 degree flap settings (all at max gross) with the 0 degree stall speed being 42 kts and 40 degrees being 37. Further, I think there is little difference in stall speed between the lower flap positions. If I assume 38 knots at 55 degrees and 40 knots at 60 that means the corresponding 1.3 Vso speeds would be 48.1, 49.4 and 52.0 knots as compared to your approach speeds of 45, 55 & 60. If I got this right, your Vso factors were 1.22, 1.45 and 1.5. Much of the difference in landing roll is probably attributed to the use of a greater safety factor for the approaches with less flaps.

Mike Koerner

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Great work D... compelling study.  Thank you !

At the 1:30 mark my Spaniel went nuts... she popped up and ran to the window hoping to find the rooster pheasant.  I played it again and she did it again... hilarious.  

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8 minutes ago, AGLyme said:

At the 1:30 mark my Spaniel went nuts..

This rooster has hung around all summer, occasionally perches on our well head up in the yard, should name him... such a magnificent bird.  One of the little pleasures on my property - hearing him cackle off in the distance.  Also have lots of eastern bluebirds around, built three houses for them, they're my favorite.

As far as take of performance, I'll continue to emphasis that loading / air temp / head wind are the primary drivers.  In the spring when the ground is real soft maybe I'll redo this, I think max flaps are a benefit in the softest of ground situations, otherwise 15 degrees should be the go to.

Landing I much prefer the higher flap settings.  30 degrees for standard landings, and 40 for max performance.  Only time I use 15 degrees in when I'm on the long runways and don't want to stick in on the numbers, need to expedite / make it to taxi way exits, etc.  And that has me flying a faster approach then as well.

50 knots when solo, 55 knots when dual, are what I find to be working well.  I'm comfortable with low 40's only when solo and super vigilant in the right conditions.

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