Bearhawk STOL mods

[schu]

I can see a little difference, but not gobs as you can see the upper windshield of both aircraft all the way down, though the bearhawk seems to have gotten into a deeper flare.

It would be much easier to tell with a cockpit camera or even better flying the approach in both.

schu

[Battson]

I can see a little difference, but not gobs as you can see the upper windshield of both aircraft all the way down, though the bearhawk seems to have gotten into a deeper flare.

It would be much easier to tell with a cockpit camera or even better flying the approach in both.

schu

I have video of the Bearhawk with the double slotted flaps landing in a deep flare, you can easily see the difference in that case. At least 8 or 10 degrees flatter deck angle and a wonderful sight picture all the way in.

I have also flown slow approaches in both planes in that last video, as PIC, and the Maule is better - but not 8 to 10 degrees better. Just a handful of degrees. But then again, that does make a difference, especially given there is no weight penalty with that design of flap hanger - it should bolt straight on.

There is a small weight penalty, I think, with the double slotted flaps. However it was very small. You make up for that very small weight penalty by how much it lightens your wallet...

[zkelley2]

If you want to do a wheel landing or a true 3 pt instead of tail first, a couple degrees will be a few knots which will be many 10s of feet shorter rollout. But most importantly you'll be able to see that log or that big hole.

[schu]

Well, when someone can get to it, we can look and see what it will take to redesign the hinge. It's just an alternate mount that can be fabricated and we loose a few degrees of deck angle on landing, that would be for sure worth it.

I have access to a bunch of actual aeronautical engineers that I do contract IT work for, so I actually have what I need to go down this road, except for my wings on the table as they are still crated. Pehaps in a few weeks.

[AKKen07]

I spoke with the guy who did the double slotted flaps for that BH. He would be happy to figure out and make whatever mount mods you need and stick it all together for you. It all just added up to more than my budget - by a lot!

[500AGL]

Unless I'm mistaken, you guys are talking about doing the same thing I mentioned that Shane Madson had done with his cub, with designing a lower hinge point, allowing the flap to roll back as it deploys. Both the Maule and the Husky use this dropped hinge point.

[schu]

I never realized that the husky has this. My good friend just bought a husky. This article shows how far down the hinge point is.... https://aviataircraft.com/wp-content...yRevisited.pdf

[500AGL]

Yeah, the husky’s are scalp slicing headache making implements of blood sourcing. 😬

Bear in mind that the greater the hinge offset, the greater the throw is required for the control arm. So to get the same angle of flap deployment you’ll need to adjust the bell crank size. This will also affect the pull required on the flap arm. It’s a typical snowball that just requires forethought. Easily achieved.

[svyolo]

You might be able to also offset the actuating arm attach point on the flaps, and keep the stock bell crank.

[whee]

Yeah, the husky’s are scalp slicing headache making implements of blood sourcing. 😬

Bear in mind that the greater the hinge offset, the greater the throw is required for the control arm. So to get the same angle of flap deployment you’ll need to adjust the bell crank size. This will also affect the pull required on the flap arm. It’s a typical snowball that just requires forethought. Easily achieved.

The Husky hinges are dropped significantly, like a really long way. That dropped hinge would interfere with the rear passenger door on a BH. The Maule hinge appears to be dropped about an inch. I think maybe I could make that hinge clear my door, and hopefully I won’t scalp myself on it.

Also worth noting, the max deflection of Husky flaps is 30deg. Sometimes, depending on the flaps design, a large deflection angle is not necessary.

[500AGL]

I agree Whee. There is a point where the flap lift is offset by the drag of the barn doors. Sometimes you want just one half of that equation. Other times you take both and want more.
My goal would be to have 2-3 notches of progressively better lift, before dropping into the 4th notch and getting the whole anchor.
Maybe the notches should not be spacely evenly. Set the plane up and fly it with progressively deeper settings until you find the sweet spot, and use that as the last notch before the full air brake.
pb

[Bcone1381]

Threads like this can make me start thinking different is always better. My interests lead towards frugal performance gains, so I'll keep mine as Bob designed it. So I ask this next question out of curiosity.

What is the drawback of the Cessna Flap design which is able to the Fowler action without an exposed hinge by using flap tracks?

[Battson]

Semi fowler flaps with a *long* track, like the Cessna, put a lot of torque on the rear spar. The risk is cracks developing in the wing skin.

[schu]

Threads like this can make me start thinking different is always better. My interests lead towards frugal performance gains, so I'll keep mine as Bob designed it. So I ask this next question out of curiosity.

What is the drawback of the Cessna Flap design which is able to the Fowler action without an exposed hinge by using flap tracks?

I would say the only drawbacks are weight, cost, and the rollers have a tenancy to eventually fail.

While there is no perfect airplane, and I'm glad to not have to deal with fuel bladders, spring gear, and cessna parts, the flaps are something they absolutely got right, as well as the trimmable stab on the 180.

[svyolo]

I still think really big fowler flaps and a THS (trim-able horizontal state) might go together. The change in center of pressure is so great with the flaps, you need the THS to handle the trim change. A big THS can be much more powerful than the elevator, which makes its' function (electric or manual) required.

I always read this thread, but cost/benefit has me sticking with stock flaps. I like the stock performance compromise, but always willing to learn.

[whee]

Post 1962 Cessna 182s don’t have a THS, they have a trim tab on the elevator. They do have the same semi-flower flaps as the earlier 180/182. So, the Cessna semi-Fowler’s and THS don’t have to exist only with each other.

I think several have said this before, I know so have; For the vast majority of pilots/builders a stock BH will do everything you need or want without issue or complaint. The few of us that want to fine tune our aircraft to exactly fit our niche have the opportunity to do so and that’s why we entered the EAB world and built our airplanes. Otherwise we could have bought a Maule, or Cessna, or... and made it work like we could make a stock Bearhawk work.

I’d love to have Cessna style flaps on my airplane but the wings have to be designed for them and I don’t know that they are. It would probably be easier to just put Cessna wings on a BH fuselage than it would to re-engineer the wing and flap mechanism to a Fowler.

[svyolo]

My thinking on the upgraded flaps has really come full circle in the last year. On a a/c with plain flaps the difference between clean and full flaps stall speed might be 10% or so. On a plane with big fowler TE flaps, as well as full span LE slats (I think the two go together as well), that difference is more on the order of 30-40%. Putting the flaps ups and down is a procedure that takes 1-5 minutes. On a go around, when light, exceeding flap limits is pretty easy to do. I used to assume that flap limit speeds were for structural reasons, but the more i think about it, they might be for controllability as well.

The more powerful the flaps, the more care you need to take putting them up and down. Putting those more powerful flaps on a manual handle, with a single pilot, might add more risk than the potential reward is worth, or at least increase the workload at exactly the time and place I don't want or need it (tight confines, lots of terrain).

[zkelley2]

Are you talking about a asymmetric deployment? Otherwise, I can't think of any controllability issues.

[Battson]

You can easily control a Bearhawk with fully asymmetric deployment, I have flown with one flap down and one up for 45 minutes (long story, already posted here). Passengers didn't even notice...

[svyolo]

Asymmetric deployment is a different issue, but also relevant. But not the topic I am talking about. It is also not something that came to me immediately. It is something that I thought about over a year or two. I tried to think about it in a way to describe it. Someone with experience flying with very powerful, high lift devices will be able to understand it easily. Someone without that experience might think I am smoking crack.

I have tried to think of analogy to explain it. Maybe the best is the Piper Aerostar and Mitsubishi Mu-2. Both were, by far, best of class airframes. Both had, by far, the worst safety records for a long time. There was nothing wrong with either airframe. The pilot training in the US was not adequate to cover the performance, and handling characteristics of either.

The more powerful the high lift devices, the greater the transition from cruise to approach, or vise verse. Going from flaps 40 to zero with simple flaps is a lot different than doing the same with fowler flaps and slats. The workload is probably 10- 20 times greater, and longer. I don't think I want to manage that while trying to fly my way out of a canyon.

[svyolo]

Again, I don't know a great way to describe it. If you modify the aircrafts flaps so that the stall speed goes down another 10%, it doesn't just affect that speed. It also affects the lift/drag at all other speeds while the flaps are deployed.

You might be shocked at the amount of time a 2 pilot crew spends managing speed/flaps on an airplane with flaps that change the stall speed by 30- 40 %. On a bush plane that has flaps that change the stall speed by 20%, it might be more workload than I want to manage as a single pilot that only flies 5-15 hours a month.

I wish I had a better way to describe it.

[zkelley2]

I think I have an awful lot of experience with high lift devices, leading edge slats, very large fowlers(that have more surface area than an entire 73 wing). I have no idea what you're talking about controllability wise. The workload a flap speed induces is no different than any other type of flap. Especially if you've ever seen how they are implemented on small airplanes. It's very different. There's literally no input from the pilot on the current slat designs, and the fowlers are only good for about 4kts typically. Which while over 10% of stall speed, isn't much. I think you're WAAAAAY over thinking this.
If I blindfolded you and put you in the airplane and we went flying in a cub with the pstol flaps, you'd never know what type of flaps were on it from a function in the cockpit point of view. The retract and deploy exactly the same. A lot of people do them 100% at once. As in no flaps or ALL the flaps.

[Battson]

Svyolo - you are probably overthinking it.

[svyolo]

Yeah, I might be. But I think I will keep it simple.