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How NOT to mount a GoPro camera (on a -9)

scard

Well Known Member
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I've seen this so many times and thought I would give it a whirl. So I spent a few minutes in the shop with my spare fuel cap. We all travel with one, right? Picture worth a thousand words:

cap1.JPG


Looks like this on the airplane, was rotated about 40deg from straight on.

cap3.JPG


Every change obviously requires a flight test, or two, or however many it takes, no matter how small. To our amazement, this configuration increased the clean stall speed (no flaps) by 12 knots! Our airplane stalls beautifully at about 52kts clean. With the camera there, it was stalling at 64kts! You could tell something wasn't right while slowing through 80kts. By 70kts it felt down right mushy. This is not what our RV feels like at all. Of course the first indication was the noticeably longer takeoff roll. The effect on stall speed with flaps down was far less.

Maybe the -9 wing is very unique with the effect of this mount, but I've seen this setup so many times. Please be sure you really flight test it.

Now, just as a thought exercise, I wonder just how long the mount stud would need to be to not have the huge adverse effect on stall characteristics?

We're still amazed at the effect. Experiment carefully as I will continue to do :).
 
So, when it did stall, was there any tendency to try to enter a spin??

There would have been no value in me exploring it that deeply. I have a rudder the size of Texas that gives tons of control, I didn't take it that deep. Once we proved that this was clearly an undesirable configuration, the flight test was terminated. Once back over the field at 6k', I did have to evaluate the safest configuration to get it back on the ground, which was full flaps. Sound familiar? Boy, we were right back in phase I in an instant.

I'm going to say it again, there must be people out flying around that haven't even tested the basics since I'm the first that I can find to report adverse effects (that are huge).
 
Seems like I read that the great air show pilot and Hollywood movie pilot Art Scholl was experimenting with different camera locations on the wing of his camera plane while shooting air scenes for the Top Gun movie and may have affected the air flow such that he couldn't recover from an inverted spin. I'm thinking neither he nor his camera plane were ever found.

If it could happen to him, it could happen to us.
 
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Scott, I have wondered about how the camera would change the flight characteristics. If tiny little vortex generators can make as much of a difference that they do make, a camera bigger than all of them combined will for sure be felt.

I have seen many videos, including one posted today flying up the coast of Florida and no reported problems. I appreciate you reporting the issues you had. I am really interested in others experiences too.

A month or so ago, someone posted a video of little strings all over his wings and how they changed in flight and what happened as they went into a stall. Maybe with that video a place could be found on the wing or other part of the plane that wouldn't cause an increase in stall speed.

I am still building so I don't have the experience with the fuel caps other than the few times while doing the tanks to know how solid they are mounted. Is there a chance that the camera could cause the catch to fail and you end up with an open fuel tank?

This will be interesting. Thanks for reporting what you experienced in your flight. I bet it was puzzling and took a bit of time to understand what was going on.
 
I am still building so I don't have the experience with the fuel caps other than the few times while doing the tanks to know how solid they are mounted. Is there a chance that the camera could cause the catch to fail and you end up with an open fuel tank?

This will be interesting. Thanks for reporting what you experienced in your flight. I bet it was puzzling and took a bit of time to understand what was going on.

The caps aren't a concern yet. The plastic in the camera mount are going to fail before the cap pops out. Force given an aerodynamic area are pretty easy to test doing zero knots on the ground. Math is easy, surviving is sometimes a little harder :).

The beauty of having a very proven airframe with which you have a perfect relationship for 7+yrs in the hands of pilots that are perfectly in tune with the exact expected performance of that airframe, to within a knot or two, is that it took no time at all to see that something significant was different. There was no puzzle to solve except for what just changed (obvious). Now how to get back on the ground with the most margin possible.

Keep 'em coming, the percent performance change amazed my little brain.
 
GearPro Tests

I have been testing a GearPro mounted using wingtip screw with camera pointing at the airplane. Did two flights without turning the camera on just to test the mount and location. So far, no effect found on flight characteristics but have had NO good in flight video yet. It fogs up inside the case! Have tried two desiccant strips and then four desiccant strips. The 4-strips help but still get fogging on the inside lens of the case. Have Ant-Fog spray ordered to try next.

Your experience tells me that I need to flight test other mounting locations that I have planned before putting the camera(s) into full use.

My ContourHD camera has been flight tested in all its possible mounting locations before actually using it to record wanted video. NONE of the locations that I use have are on top of the wing that did not use a location on the wing tip. ContourHD forward facing on wingtip works as does under wing using tiedown mount bolt hole. Tiedown bolt hole looking forward does not work for formation flying as all you get is the wheel pants of the aircraft in front. Looking back works fine.

Thanks for sharing the additional test location that I had not thought about. I know it is one that I will not use based on your test data. Yes I do carry as spare fuel cap in my tool kit.
 
I've used the NFlightCam mounting spud and swivel (ball joint) mount for the GoPro, mounted on the outboard aftmost fuel tank screw, upper wing surface, and noticed no change in handling or performance.

I have a friend who mounted a GoPro on the *bottom* of the wing (don't know the exact location) who reported a "huge" change in yaw. We surmised that it might have been mounted closer to the wing surface, resulting in disturbed airflow closer to the boundary layer, and thus created more of an effect than the NFlightCam (and my positioning) putting the camera higher and thus further from the boundary layer on top.

But that's all speculation...I just know my location works just fine with no adverse effects.
 
The first time I mounted the GoPro was underneath the right wing to get a glimpse of my gear legs during all flight phases. I mounted it on the inspection cover for the bellcrank. I did not notice any flight characteristic changes but then I did not test for any. WiFi control of the unit was not good in this position.

I then moved it to the left wingtip for some inflight pics/movies. First thing I noticed during the takeoff roll was the need for more right rudder. The same with all stages of flight. Stalls were normal with a slight tendency to drop the left wing first with the feet off the rudder. Using normal rudder technique stalls were a non issue.
 
Thanks for the post. When I read it this morning, I though you were joking about the change in stall speed! Very interesting to read that is was not a joke and the effect is real.

Greg
 
Scott - thanks for the report. I've mounted a camera to my wing on a few occurrences.

You're reminder is that these things affect the performance of our aircraft. Often we have more than enough performance margin but a camera can reduce that envelope.

Imagine that vacation into a back country air strip in the mountains. Sounds like a great chance to record video. Mountain flight, short grass runways, passenger and cargo, and altitude all push the airplane toward the edges of the envelope. The camera(s) may have shrunk that same envelope.
 
Interesting that you should mention this scenario...

You're reminder is that these things affect the performance of our aircraft. Often we have more than enough performance margin but a camera can reduce that envelope.

Imagine that vacation into a back country air strip in the mountains. Sounds like a great chance to record video. Mountain flight, short grass runways, passenger and cargo, and altitude all push the airplane toward the edges of the envelope. The camera(s) may have shrunk that same envelope.

Just to provide some additional emphasis to your point, for many years the CAP here in Colorado has used a training video to train its search and rescue aircrews. The video was taken from a restored L-19 Bird Dog with a wing-strut-mounted video camera, that unfortunately recorded their own demise in the 1970s, after departing a mountain airport for a sight seeing trip. The crash site and the video footage from the camera were not discovered/recovered until many years later.

The resulting crash was attributed to several factors - mostly from climbing into rising terrain and getting into a position they could not safely get out of, but I never really stopped to think about the potential impact of the camera mount on the aircraft's performance, and how that may have contributed to the crash. And this occurred back in the '70s when the Go Pro was perhaps a thought in someone's imagination, so the camera equipment was most definitely larger that what we have available to us today.

Scott - thanks for posting your results, because this is real eye opener about how seemingly small the change might be, and how dramatically it may affect flight performance in different flight configurations. I too will be making some mods that will require extensive flight testing, so I find this sort of info very helpful.
 
Go Pro

There was a Formation Aerobatic Team , the French Connection ( flew Cap 10s)
A camera was added to one of the planes wingtip and the cable duct taped to the wing going back to the fuselage, changed the stall speed/characteristics . One plane stalled before the pivot turn on a formation hammerhead and hit the other ,ending the French Connection .
Shows that small changes to the airfoil can make a big change in airflow .
 
not just cameras......

I often wish I had a nice video of 'someone' who has tuft tested an entire Rv.

frequently in magazines ( you know, those glossy, paper...never mind!)

you'd see someone wind yarn around the wing, run long lines of tape from root to tip, and then snip the yarn, giving nice, long, even patterns to show the flow.
I always wondered if they took into account how all the spanwise tapes altered the flow over the wing!!!

No doubt best to make very small, incremental changes when doing that type of thing, as you are truly a 'test pilot' each time!

kudos to Scott for taking note, and sharing with us 'old, not-so-bold' pilots.
 
Vortex Videos

I found the post I was looking for. Steve M posted a link to a video showing strings as they move in flight and stalls. These two videos are very interesting and give a whole new thought process for mounting a camera or anything for that matter.

http://www.vansairforce.com/community/showthread.php?t=110713&highlight=vortex

http://www.youtube.com/watch?v=qeSoO3nXjjI&feature=youtu.be

http://www.youtube.com/watch?v=ECTCVgiBHjA&feature=youtu.be

Those two videos are well worth watching if you are going to stick a camera on your wing. Maybe a fairing around the camera would help. Maybe building it into the front edge of the wing tip? It is about the same size as a landing light - mount the camera behind the lens?

Great thread - thanks Scott. This may save one of us from learning the hard way.
 
Airshow pilots have been advised by various FAA personnel that any addition of cameras to the aircraft exterior must be logged and flight tested in and out of phase 1.
 
Think of it as a spoiler, that is right where it is siting, down close to where the attached flow is for the top of the airfoil. You could probably put it on a streamlined pylon that raised it a few inches above the wing with negligible impact on aerodynamics, although the drag component would still be there. Even less impact on bottom of wing.

In any case, they should be tested exhaustively.
 
There was a Formation Aerobatic Team , the French Connection ( flew Cap 10s)
A camera was added to one of the planes wingtip and the cable duct taped to the wing going back to the fuselage, changed the stall speed/characteristics . One plane stalled before the pivot turn on a formation hammerhead and hit the other ,ending the French Connection .
Shows that small changes to the airfoil can make a big change in airflow .
This didn't sound right to me so I had to look it up. According to the NTSB report, both aircraft made the hammerhead turn just fine, although the wingman started early and ended up ahead of the leader after the turn. The report also concluded from the camera footage that the camera did not affect airframe performance enough to affect the formation flight.

http://planecrashmap.com/plane/fl/N86KB/
 
Some airfoil shapes are very sensitive to any disruptions. Rutan discovered this with flying into rain with the Vari-eze. Just flying with an accumulation of bugs splattered on the leading edge had some serious affects. There was a Quickie that had a leading edge pinstripe that significantly disrupted the airfoil after being painted. A camera on the wing surface is fairly localized as opposed to being the entire length of the wing, but it can, as Scott points out, a significant disruptor of the airflow. I'm wondering if the unique Roncz airfoil on the -9 is more sensitive than the other models.
 
can't bend my brain around this

and would love to hear some aerodynamicists weigh in. My first roadblock to acceptance is in trying to imagine that an object capable of disrupting such a small % of span-wise flow on one wing could change stall characteristics so drastically. I can't make myself picture it. Guess I'll wait for the yarn tuft video :confused:

Secondly, I can't grasp how an asymmetrical change that raised overall stall speed by almost 25% didn't produce a violent spin entry as stall was approached. The modified wing would had to have let go long before the other. Scott describes not wanting to explore the stall, even armed with a large rudder, and I understand the reluctance (!) but this would be a situation of Russian proportions: "In Go-Pro motherland, stall explores you!"

My brain's refusal to believe what is posted is no one's problem but my own. No flames. But I just can't comprehend how this happened as described - and would love a sound explanation of the mystery. Have skin in the game since I've taped a Contour to my wing and empennage many a time with no untoward effects and want to keep doing so without hurting myself.

-Stormy
 
There was a Quickie that had a leading edge pinstripe that significantly disrupted the airfoil after being painted.

Interesting, Bruce. Van's also makes a point in the preview plans about paint seams near the leading edge?making sure there's not too much of a "step" in paint thickness.

I think I'll limit the GoPros on my first flight to inside the canopy!
 
bottom of the wing

Mounting a camera and other airflow disturbing device is much safer when done on the underside of the wing.
 
Airshow pilots have been advised by various FAA personnel that any addition of cameras to the aircraft exterior must be logged and flight tested in and out of phase 1.

Mike im interested to hear more about this. What the procedure the FAA is reccomending on an experimental if you already have your AWC? I personally have 6 different cammera positions that I can play w/ 3 at a time...some external, some internal...
 
wingtip

I put my go pro on the upper surface of the fiberglass tip with no noticeable effect. I used the standard base and swivels in the waterproof housing.

Don
 
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