Ok this is all good to know. I got to see (hear) Battson’s AOA in action and it seemed intuitive having the audible beeps.
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4-place Landing Techniques
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Last edited by Nev; 02-01-2021, 03:45 AM.Nev Bailey
Christchurch, NZ
BearhawkBlog.com - Safety & Maintenance Notes
YouTube - Build and flying channel
Builders Log - We build planes
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I'm curious why people say the profiled tail doesn't do well with VG's on the underside. I have them and it seems to do very well. What is it that people think isn't good?
My tail has always stalled before my wing at typical CG, which is fairly forward. So, making the tail more effective has allowed me to fly slower.
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I have the same question Bobby. I have 100 hours on her now. I'm still in the early stages of learning. Goal this year is CONSISTENT 500 foot, hard surface landing distance with airframe friendly touchdowns. Like Whee, I can slow it down with plenty of control left. My issue is the high rate of descent and transition at the bottom. I plan to go into some narrow backcountry runways and over nose visibility is a must for my comfort level. VG's are on the short list. Want to establish a baseline first. Lots of slow flight and landing practice to go.Last edited by John Bickham; 02-05-2021, 05:55 AM.Thanks too much,
John Bickham
Los Lunas, NM Mid Valley Airpark E98
BH Plans #1117
Avipro wings/Scratch
http://www.mykitlog.com/users/index....er&project=882
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Well... perhaps a test is in order. I put VG's on my wing (A wing) and tail (profiled) at the same time. It reduced my stall by 5 knots or so and made it much much more stable at slow speed. I really liked the results so I just left it that way. But, perhaps it's worth a test to remove them from the profiled tail and see the difference.
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I really liked the results so I just left it that way. But, perhaps it's worth a test to remove them from the profiled tail and see the difference.Nev Bailey
Christchurch, NZ
BearhawkBlog.com - Safety & Maintenance Notes
YouTube - Build and flying channel
Builders Log - We build planes
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swpilot3, we should meet somewhere and do some testing. I don’t have VGs on my plane and haven’t felt the need for them but I’m thinking about adding them. I’ve never noticed my tail stalling either. I’m obviously not pushing the limits of the airplane. A wing and profiled tail.
Mark Patey did an interesting VG test and posted it to YouTube. His method for observing if the tail stalled vs the wing was simple. I’d never though about the mechanics of the tail stalling vs the wing during power off stalls. I thought about doing the same test if I install VGs and a elevator gap seal.
I’m pretty sure lsilverone has a flat tail on his BH.Scratch Built 4-place Bearhawk. Continental IO-360, 88" C203 McCauley prop.
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I've been reading a lot of articles and trying to deepen my understanding of aerodynamics. I can't for the life of me envision how VGs could make aerodynamics worse. Does anyone have an idea of how VGs could make feel and performance of the horizontal stab worse? Too much adhesion? I can't see a scenario where VG's create less adhesion. Why would a profiled stab make any difference as it relates to VGs?
Does anyone know of any documentation that shows a negative effect of VGs?
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Originally posted by swpilot3 View PostI've been reading a lot of articles and trying to deepen my understanding of aerodynamics. I can't for the life of me envision how VGs could make aerodynamics worse. Does anyone have an idea of how VGs could make feel and performance of the horizontal stab worse? Too much adhesion? I can't see a scenario where VG's create less adhesion. Why would a profiled stab make any difference as it relates to VGs?
Does anyone know of any documentation that shows a negative effect of VGs?
Scratch Built 4-place Bearhawk. Continental IO-360, 88" C203 McCauley prop.
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Originally posted by whee View Post
if I remember correctly lsilverone felt like VGs on the tail of his Patrol made it very pitchy. I could see that being possible since VGs can improved the effectiveness of flight controls. Making light controls lighter may not be favorable to some.
Mike
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I’ve been thinking about elevator authority and how many of you guys say it runs out when doing max performance landings. This isn’t something I’ve noticed and I can only think of two reasons: 1. I’m not flying the airplane close enough to the edge to notice. This is the mostly likely reason. Still, I don’t know how I could land the plane any slower; I already feel like a slatted cub that lands tail first and plops the mains down from 4ft up.
2. My longerons are extended 2†in the tail section. Perhaps this little bit of extra leverage is enough to make a difference in elevator authority?Scratch Built 4-place Bearhawk. Continental IO-360, 88" C203 McCauley prop.
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I watched Battson’s video of his Bearhawk performing at a STOL competition last year (and won), and I noticed that on very short finals the elevators appear to be at maximum upward deflection against the stops. This is with the CG at nearly the forward limit (1 POB vs 2 POB). A question in my mind is whether this is the perfect scenario where the elevators lose authority just before the main wings stall. Either way, the fact that the Bearhawk outperformed others on the day implies that even without VG’s, it’s holding enough pitch authority to fly at a slower speed than other STOL aircraft.
I’m very curious to know with VG’s under the tailplane, does it provide enough authority to get into an undesirable pitch attitude at slow speed, or does it just improve the already great slow speed handling ?Nev Bailey
Christchurch, NZ
BearhawkBlog.com - Safety & Maintenance Notes
YouTube - Build and flying channel
Builders Log - We build planes
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I feel that the VGs and gap seals did in fact increase control authority and certainly improved the slow speed handling. I don’t feel that you can get yourself into an undesirable pitch attitude as a consequence of these additions, you simply run out of elevator in most slow landings, even with the VGs. All of these approaches and landings are power on, it’s the only way to make it happen when you’ve run out of elevator, like Jared mentions. As has been discussed elsewhere, the real game changer will be double slotted flaps. I started down the path last fall, after speaking to the gent that just sold the 4 place with them on it. It’s certainly not that difficult to do but it will cost a good chunk of change. Still contemplating it though.
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Originally posted by whee View Post
if I remember correctly lsilverone felt like VGs on the tail of his Patrol made it very pitchy. I could see that being possible since VGs can improved the effectiveness of flight controls. Making light controls lighter may not be favorable to some.
It was a Bravo with the profiled stabilizer.
It was not pitch sensitive at a middling CG location, in fact I didn't even realize there were VGs installed until after the flight. We did not get a chance to fly with full aft CG.
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