Custom flap handle

[Battson]

For a long time, I have wanted to modify the standard Bearhawk flap handle. I think the original handle is perfectly suited as Bob designed it, where you are using a little flap occasionally flying from place to place (delivering engines) noting that Bob apparently enjoys slipping in flapless on some landings. It's small, light, simple, and out of the way.

So why do I want to change it?

I've found the original lever is simply too short for the recreational backcountry flying, which I enjoy the most. There is insufficient leverage and the pull force is too high for the last two notches are. After repeated use it quickly becomes tiresome. Yes - before you ask - I am always well below the flap speeds when I select a notch, as slow as possible But in some extreme cases, I need to actuate the flaps perhaps 150 times during the course of 30 or 40 landings, perhaps in as little as three or four hours elapsed time. What's more, 2/3rds of those flap movements are at the higher end of the force scale (3rd and 4th notch). Most days flying are not nearly that severe, but still that short lever makes it harder than other aircraft. I use full flaps and land slow for every single landing I make, except for strong crosswind days.

On a number of occasions I have strained my back by jerking the handle once I tire (Latissimus Dorsi) - on one occasion the strain was so bad, I could hardly use the flaps at all for several days. I had to seriously change the way I flew an approach during that time, to avoid repeatedly straining my injury. Notwithstanding my particular circumstances, that last notch is a distraction during an unwelcome critical part of any difficult approach. The small diameter (T11) bar is also difficult to grasp with big hands, and on a hot summer day with sweat on my palms, it's slipped from my hand on a few occasions. But not to worry, the solution was so easy to install!

That's why I decided to make this change. Your circumstances may vary. For most people, they might never want such a change.

What does the change include?

A picture is worth a thousand words...


Here are some words anyway.... I overlapped a larger radius tube on the end of the existing flap handle (welding per AC43.13B). The extension is 6" long with a 2.5" overlap on the existing handle. That gives about a 50% longer handle overall. I lengthened the push-button by welding another equal diameter section onto the end, but first I pulled out the end plug to reuse on the longer button, it was just Loctited in. I welded in a section of the original gauge tube into the end on the extension, so the button has a snug-fitting guide to slide within. The button is now six inches further forward on the floor, which means I have to lean down further when I retract the flaps. To combat this, I added a second way to press the button. To do this, I put slot in flap handle and screwed a thumb-tab onto the innermost tube. This is located where the tip of the original flap button was. With this addition, I can retract the flaps without reaching further forward than before.

So how does it work? I haven't flow it yet, but the reduction in force is obvious. You could easily calculate the reduced kilogram (or Newton) force required, but let me put it in simple terms. Whereas before I could feel the springs growing tighter, now the handle has zero feeling. I don't notice any increase in resistance while I put each notch of flap on. I will report back again after I've flown it this weekend.

It sits above my fuel selector, but there is room for fingers in between without a pinch. The length is about the same as the floorboards / carpeted area, or just a fraction shorter.


The new flap handle clears the dash with a big thumb resting atop the button. Again this was a 6" extension.


At full flap, the handle is right in front of the pilot, handy to the throttle, and to the joystick. It's also in-view, which is good. Incidentally, the control sticks can still go to full travel without interfering with the flap handle, or the pilots knee. As before this change, there is no accounting for passenger's knees... Note the flap handle is offset toward the passenger seat.


Operationally, this change means I have to observe the existing rules as closely as before. The longer stick will make it easier to select another notch of flap, while flying above the speeds listed in the POH. But then again, the pilot can exceed the operational limits just by lowering the nose at any time..... so PIC's responsibilities don't change whatsoever due to this mod. I am certain that this mod will be favourable in a backcountry flying situation, however I will confirm / deny after the weekend.

[Battson]

P.s. the black is not necessarily the final colour, it's just the colour I had left, of my best quality etch primer.

[whee]

Looks great! Looking forward to a flight report.

[Battson]

So I've flown about 10 to 15 hours with this mod now.... It's been a huge week for backcountry flying!

After a minor tweak to get the design right, it's working perfectly. I needed to add a second spring (which fits inside the original spring) to account for the extra weight / friction of the longer button.

Long story short, this mod makes setting up an approach into an effortless and relaxing task, it's so much more enjoyable!!
I cannot believe nor overemphasize what a big difference it makes to the usability of the flaps. I would recommend this mod to anyone who'll be using the flaps often, I am absolutely thrilled with the mod.

I added the button "thumb tab" half way down the handle, but practically, I found I never ever use it. Perhaps that's just because I am tall and can reach easily.

[haribole]

Hi Battson, would you happen to have the sizes of the springs you used? I am having a hard time getting the right spring. I did extend the flap handle as yours, but the flap does not stay engaged and slips down to the first notch.

[Battson]

I just took the existing spring down to hardware store and bought a few other springs which fitted inside the original, then install and test to find the one which works.

Be aware that unmodified flap handles (where the quadrant goes through the notch in the handle) have a known issue whereby there's not enough clearance and the pin only partically engages with the quadrant, I don't think this has been fixed on the kitset yet (9 years later :P), based on the latest Bravo kits I have seen. You can easily fix it by opening the flap handle to increase clearance around the pin with a file. See the drawing linked below.
See my initial advice about this issue here: https://bearhawkforums.com/forum/saf...t-interference

[Flygirl1]

Thanks for sharing. I get it. At the moment 3 notches of flaps seem to be an impossibility for me. The last and only time I tried, ( only have 5 hrs now ) I broke two finger nails and lost the original 2 notches of flap when it slipped and slammed back down. This is in the Patrol, so not sure how far we can extend, but based on your experience, any will be an improvement. Also glad to hear somebody has WX good enough to fly. Consider yourself lucky!! Donna P.S. I sprayed flex seal on the sticks and flap handle. It's a little grippier than just paint.

[Battson]

Thanks for sharing. I get it. At the moment 3 notches of flaps seem to be an impossibility for me. The last and only time I tried, ( only have 5 hrs now ) I broke two finger nails and lost the original 2 notches of flap when it slipped and slammed back down. This is in the Patrol, so not sure how far we can extend, but based on your experience, any will be an improvement. Also glad to hear somebody has WX good enough to fly. Consider yourself lucky!! Donna P.S. I sprayed flex seal on the sticks and flap handle. It's a little grippier than just paint.

I hear you, my wife couldn't grab more than two notches either! That was a big part of the motivation for this change.

[huntaero]

Looks good, Thanks for sharing. I haven't flown a Bearhawk yet but always thought it was a little short, I am use to the Cessna's and full flap can be a handfull even with their long handle.

[whee]

I added the button "thumb tab" half way down the handle, but practically, I found I never ever use it. Perhaps that's just because I am tall and can reach easily.

So just to clarify, no need for the "thumb tab"? Seems like it would get used but I don't want to add it if it's not going to get used.

[Battson]

So just to clarify, no need for the "thumb tab"? Seems like it would get used but I don't want to add it if it's not going to get used.

Yeah I never used it once.
The pull forces are so high down there - it's easier to reach for the top of the bar.
The first two notches don't need the button depressed anyway, as the bar comes up. After that the top is within easy reach. Going back down, you have to bend at the waist a little, but that's what comes naturally.

I would start without the thumb tab. You could always add it later, if you changed your mind. No extra welding, just drill a couple of holes and tap.

[Sebastian]

Battson

I enjoyed your post even though I am late to the conversation and can't see the picture for some reason. I get the jest of the modification you made.
Since you fly backcountry a lot have you found that the flaps would be easier to operate if all the notches were ramped like the first two positions? Do the last two positions need to be locked in the way they are for some reason my mind doesn't comprehend?

CJ

[Battson]

Battson

I enjoyed your post even though I am late to the conversation and can't see the picture for some reason. I get the jest of the modification you made.
Since you fly backcountry a lot have you found that the flaps would be easier to operate if all the notches were ramped like the first two positions? Do the last two positions need to be locked in the way they are for some reason my mind doesn't comprehend?

CJ

Hi CJ,

I have not ramped the detents for the last two notches, although it's a thought worth considering. I think it comes down to personal preference, I can't see any reason why not to ramp the detents for the last two notches.

[JimParker256]

Hi CJ,

I have not ramped the detents for the last two notches, although it's a thought worth considering. I think it comes down to personal preference, I can't see any reason why not to ramp the detents for the last two notches.

I thought that the reason for the "ramped" first two notches were so you could grab "lift" flaps for short/soft field takeoffs, without being in danger of pulling the 3rd or 4th notches (which are definitely "drag" flaps). But hey, I've been wrong before!

[Battson]

I thought that the reason for the "ramped" first two notches were so you could grab "lift" flaps for short/soft field takeoffs, without being in danger of pulling the 3rd or 4th notches (which are definitely "drag" flaps). But hey, I've been wrong before!

I think the first two notches are ramped so you can grab the first two notches without having to reach forward and push the button first, which is hard to reach with the handle on the ground?? The first notch basically does nothing to the flaps, it just tensions up the cables and torque tubes.

You definitely want to "pop" almost full flaps to force the plane off the ground for a max performance take-off. I set two notches before I roll, then pull everything on. I use a countdown to get the rough time to "pop", depending on weight, DA, etc. You can feel the sweet spot between lift and drag in the flap handle when you pull it, and you can tell if you were early or late.

You have to bleed the flaps off almost immediately, perhaps 2 seconds after lift-off at most, the exact timing depends on how well you timed your "pop". If you left full flaps you would not have a good climbout. Yes full flaps is a draggy configuration, but also adds lots of camber to the part of the wing exposed to propwash. That redirects all that wash air into ground effect. I imagine this is creating an air cushion which the plane flies upon (only just flies! more like awkwardly staggers), because the speeds are too low for the wing alone to be lifting the aircraft. I imagine the new flaps which span right up to the fuselage will measureable improve this part of the performance envelope (short take-off).

"Pop" is a funny choice of word, because the plane does anything but pop up off the ground. It's like coaxing a teenager out of bed at 5am, you need to coerce it, and it doesn't want to go with you. If you are popping two notches of flaps and the plane is getting airborne readily, then the plane was actually ready to fly several seconds ago.

[Battson]

I should add that the above technique is good for minimising ground roll, like when you're running out of gravel bar and approaching the water. It may not provide best obstacle clearance (Vx climb type of scenario) if you have ample runway ahead but also need to clear the trees at the end of it!!

[Sebastian]

Battson

Thanks for the response. I can see by your response that I will have a lot of practicing ahead of me to get the timing down for a quick liftoff. I am curious about what kind of minimal distances you have found you need to lift off and clear a 50' obstacle consistently.
CJ