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  • Retractable Landing Light

    I know there are other threads about landing light locations, leading edge of the wing vs nose bowl vs wing tip etc. but I thought I’d offer another potential solution. I thought about all of the standard options for locating the light and had nearly settled on the wing tip location. That is until I stumbled upon a kitplanes article some months back. The article highlighted Legends MOAC super cub, a very beautiful airplane. As I made my way through the article a hinged light on the bottom side of the wing caught my eye. Only a few sentences in the article touched on this photo and the info was pretty minimal but I hung onto the words “retractable landing light.”




    I thought it was super neat and decided I had to have one. In the kitplanes article they mention that the light is actuated by a servo but that’s about all they say. So what did I do? I picked up the phone, called Legend, spent 15 min on the phone trying to sweet talking the female operator into divulging proprietary information on their design. Needless to say that didn’t work. So I called back from a different number and asked for the guys in the shop, they weren’t about to give away any secrets either. It was worth a shot
    Attached Files
    Last edited by Jhankins; 11-19-2022, 01:04 PM.

  • #2
    Not sure why the entire post isnt showing up but here’s the rest of the write up…..

    I reached out to the owner of the plane from the kitplanes article. He was very nice and seemed willing to help, he was unaware of any specifics around the light as he opted to do the factory build assist program and wasn’t present at the time of install. He said he would send me some photos but after a couple months and a few follow ups I was left empty handed. I turned to the internet, trying to find anything out there that was similar. Other than the old mechanically linked Cessna 140 and air tractor lights I didn’t have much luck. It was at this point I decided I would figure it out myself.

    I am not an engineer by any stretch of the word, I’m a 29 yr old wood scientist from east Tenneessee who can’t stand to leave a problem unsolved. I sat down, put pencil to paper, and after a few revisions came up with a design I thought would work. Total disclaimer, I have only been in the aviation world for 3 years, this is my first build, and I have next to zero knowledge of servos so I would consider this a pretty crude design.

    Although I bought one, I couldn’t see or envision how a small servo might drive the light open/closed, the visualization of that linkage escapes me. My approach was a little different and I’ll do my best to outline the major components. The doubler is .063” (is that overkill?), the light itself is from BAJA, the “inspection cover” if you will aka the portion that houses the light is .032”. I used a standard piano hinge to facilitate the pivot point. The source of motion is a linear actuator from the aviation department of Amazon. It has a max lift rating of 225 lbs, I think that would be plenty of force to open the light while in the landing configuration. Thoughts on that??? The actuator is mounted to a bracket that is riveted to the wing skin. I plan on using a 7 pin rocker switch to simultaneously raise and lower the lights in each wing.

    My question(s) for those of you much more knowledgeable than myself is how can one improve on this design? Does anyone have recommendations for making this servo actuated? That would help a lot in terms of weight reduction. Any other thoughts or recommendations you guys an gals might have are greatly appreciated.

    I can provide more detail on the bracket, install, and part information if anyone is interested.

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    • #3
      Right on Man! Can’t wait to see it flying!
      Almost flying!

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      • #4
        There was at least one Bearhawk that had a retractable light but I don't think the original builder is still around. I'll dig around and see if I can find any pictures of it.

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        • #5

          I’d have to look at my Velocity, but 225lbs on a Linear actuator seems high. We have a 20”x20” roughly belly speed break that we open on final and I don’t think ours is that high. I also had one on my Long Ez that replaced the mechanical over center mechanism. Here is a link to a similar setup and he’s using 115lbs on 4” of stroke for a 17x17” speed break. The Long Ez also has a retractable landing light but I don’t recall knowing anyone who uses a L.A. for it but I’m sure there are a few out there (along with the Cozy Mk IV) http://www.aryjglantz.com/2013/09/sp...uator.html?m=1
          Velocity also uses a L.A. for the canard trim and I have one to direct my oil cooler discharge air for heating the cabin or send it overboard. It’s a lot smaller of actuator. I could look the next time I’m at the hanger.

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          • #6
            This company makes a cowl flap for experimental aircraft. It may help in your design efforts. Turn it around and it is a landing light bay.

            Anti-Splat-Aero is very proud to offer this new revolutionary product, the “EZ Cool Flap” as a long-awaited solution to this sometimes-challenging task of climbing out without high CHTs.  This new revolutionary, retrofit electric cowl flap product will definitely help calm the fears of many RV owners and builders of these great aircraft. After watching, reading, […]


            here is their replacement servo

            Last edited by BravoGolf; 11-19-2022, 10:34 PM.
            Scott Ahrens
            Bearhawk Patrol Plans Built
            #254

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            • #7
              It’s pretty cool! But I’ll be a “nattering nabob of negativity” on this one. Why? Adds complexity and another thing to fail right when you might need it.

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              • #8
                Cessna 170-A has a retractable landing light- you could check out the parts book to get ideas- maybe salvage one
                Last edited by Paul Johnston; 11-21-2022, 03:15 AM.

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                • #9
                  I was just curious to understand what attracts you to it Jhankins ?

                  I guess there are some downsides - it's going to add more drag than a flush-mounted one, weight / complexity, and you have to cut another hole in the wing structure which makes my hairs stand up. (From a person who installed zero lights in his plane )​

                  What are the upsides which you are most attracted to, other than the cool factor of course - which I totally get.

                  Edit to add - finally got the video download:

                  Picture1.png

                  Certainly oozing cool factor, and very nice to watch it move. I would also like to comment your craftsmanship, it all looks really beautifully made.

                  I am conscious it looks like an tiny little airbrake. That flat planar shape might cause some extra considerations. No problems, just things to consider:

                  You'd want to be sure the skin has a serious doubler over a wide area, both where it attaches and where the actuator attaches. All those forces are going to be transferred into the wing skin and back through the skin to the spars. I see you've put it at the front spar which is sensible - I assume the doubler is straight onto the spar web? I suggest designing in a known failure point, something which can break easily and allow it to snap shut, so it doesn't permanently bend something that one time you forget to retract it and spend 30 minutes in cruise flight. It happens, like leaving the flaps down.

                  I think it may also make the plane fly just ever so slightly (but perhaps noticeably) out of balance at circuit airspeeds. This, based on a few tests we've done with things attached to the wing or things stuck out the window. Given it's well outboard of the aileron drive and the size of an inspection plate, perpendicular to the flow, that should be noticeable source of drag - only time will tell. Below 50 knots I doubt it will be noticeable. I guess there's a risk of a very small but perhaps noticeable affect on stall characteristics, given it is rather un-aerodynamic. Again - just something to work out in the test flying phase - no major issue, just a consideration.

                  I can imagine if there's only one fixed point on the back, to attach the actuator, I guess it will try and oscillate. Cracking is going to be a real risk both where the actuator attaches and around the rivets which hold it in place. It probably won't be a problem you see in the first 500 hours, but I would say it'll be a real risk in the first thousand hours. We have seen similar issues with some parts like cowl flaps / baffles. Again - something you can address when the time comes. ​

                  ​​
                  Last edited by Battson; 11-20-2022, 09:03 PM.

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                  • #10
                    I have to agree with Battson . I decided to install a leading edge pitot tube for the retro look. It added a lot of time that could have been spent elsewhere on the build. But I do think the retractable landing light is a cool idea
                    Scott Ahrens
                    Bearhawk Patrol Plans Built
                    #254

                    Comment


                    • #11
                      I have a friend who just had a 1946 J-3 Cub completely restored from ground up at Legend Cub. It took forever but they did excellent work. While I was there (multiple times supporting him and his checkbook), I got close up with the retractable landing light. It definitely adds the WOW factor and seems to work well on their aircraft. It does look like it would be a fairly simple installation. I will see if I can get a price on a unit in the next couple of weeks (we should be there picking up his Cub in early December). I believe they "estimated" something like $2000 for the entire unit? I will see if I can get verification of pricing and if they will sell the unit to the Bearhawk community.

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                      • #12
                        Airplane3472 they have the price listed on their website, I asked the same question and was told that the technology was only available for cub owners. I hope you have better luck! If not at least try to grab a couple quick photos

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                        • #13
                          Just out of curiosity…. Why the retractable/actuating light when you could install it in the wing’s leading edge? Just seems more durable and less can go wrong?
                          N678C
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                          • #14
                            I agree, retractable anything on an airplane is cool. I think flaps are cool. Weird, I know.

                            There was a time when retractable landing lights were common. Grimes may be the most well known manufacturer of such lights. They aren’t cheap or lightweight: https://www.aircraftspruce.com/catal...es-45-0148.php

                            As an alternative, I am curious about the utility of a low profile underwing fixed and faired light(s). How about incorporating the LED assembly into an inspection/service plate replacement? If one fixture doesn’t provide the quality or quantity of lumens in the direction of throw desired, then add multiples. Not as sexy as a retractable unit, but maybe a more elegant solution.

                            Lew

                            Can’t resist sharing a most recent example of a retractable landing light I photographed at OSH. Su-29 UAB: DF4656E6-B95A-4711-9927-EA01D6BC2595.jpg24985A9B-2075-4C8B-8766-2891B6CA91AF.jpg
                            Last edited by Light&Sweet; 11-22-2022, 08:58 AM.

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                            • #15
                              Battson thanks for posting the picture, I guess I need a couple lessons in learning how to post/attach files on the forum. What attracted me to it, other than the fact that is looks really cool is that it is different, I like the mental challenge of implementing something unpopular. I guess to an extent we all enjoy such things, otherwise we would'nt be building our own airplanes. Other than the kitplanes article I mentioned I could not find anything else like it and I guess I am sucker for uniqueness.

                              When fully retracted it is pretty much flush with the bottom of the wing skin, the perimeter of the light housing is all that protrudes from the wing, I agree it will cause more drag but it should be negligible I hope. Other than the cool factor I like that I will be able to "aim" the landing light wherever I need it. The actuator has internal limit switches that stop it when fully extended/retracted but you can stop the stroke at any position which allows me to point the lights anywhere from straight at the ground to 90 degrees perpendicular.

                              I appreciate your thoughts/comments on the doubler, they reaffirm the thoughts I had myself. I used .063 as a doubler, it extends fore all the way to the main spar and goes 3" aft of the opening. On the inboard side it extends to the rib and 3" to the outboard side. The bracket holding the actuator is hat shaped just like the fuel tank bay stiffeners, I believe it is 7" wide. I guess we think a lot alike...I was concerned about not having a failure point so I designed the linkage between the light and the actuator to be the weak spot. I 3D printed two identical brackets that are slotted, a plastic dowel goes through one slot, through the hole in the actuator shaft, and then through the other slot, it is held in place with oversized cotter pins to prevent lateral movement. The "top" portion of the slot (where the actuator shaft and dowel are positioned in the fully open position) is solid. The "bottom" portion of the slot (where the shaft and dowel are position in the fully closed position) was printed with 1/4 the density of the top slot. It should break before anything else. I will see if I can edit my original post and upload the video from youtube.

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