We are trying to tune a flyingwings Falcon 5 mapper pro flying wing. This may be a very silly question but is there an obvious way to slow down ground speed in auto?

We have trim_throttle set at 30 and min set to 12m/s and max to 18m/s. Into wind we achieve the desired ground speed of <15m/s thus allowing our camera (A6000) sufficient time between shots (i.e. >3s). With a tail wind things get silly with speed exceeding 25m/s and thus the camera cannot shoot fast enough. Now it is windy (up to 25km/h gusts), but sometimes we need to fly missions in these conditions and waiting for a less windy day is not practical. 

Moving the trim_throttle down to 30 has improved things but how low can we go with this? (note there is an airspeed sensor to help prevent stall). Are flaps an option on a flying wing ?

We did try flying crosswind but the success is marginal.

Maybe we ask the impossible but I thought I would ask :) Any suggestions would be welcome.

 

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Hi Darrel,

The speed you define in your mission is the airspeed.

In my experience, the only way to get the exposure rates you want is to limit the 'AUTO' settings on your camera. This is where the bottleneck comes in. You have to optimize your camera settings. I don't think there is a wing that will fly slow enough to give a 75% cover at 100m relative altitude and still carry a 600g camera with a 16mm lens with the setting left on auto. Here is how I use my Sony on my Skywalker:

I plan my missions for 100m relative altitude, 15m/s airspeed with a 75% overlap, side and forward. I launch in FBWA mode, make sure all goes well and gain some altitude. When I switch to auto, I have to bring the throttle back to the center else the plain maintains the PWM setting of the throttle. It has to be far enough back for the AP to take control of the speed. From there it maintains airspeed pretty well. I try to fly my mission 90 degrees on the wind direction. This creates a larger yaw in the pics but gives the same ground speed on the legs.....in theory:)

For my camera :

1. I use the fastest SD card I could find.

2. I store JPG - best quality your camera can manage - the raw files are huge and takes time to move to the SD card. The down side is that you can not fiddle much with the pics afterwards.

3. I use shutter priority mode at 2000 or 2500 or higher on bright days.

4. I keep the ISO on auto - I found this not to have such a great time impact, same with white balancing.

5. The big culprit is auto focus. I use manual focus.I do a manual focus before launch. This is not as easy as it sounds but not impossible. I hook my camera up to Playmemories on my ipad via wifi to have a nice big screen to check the focus. Even then its not always as crisp as it can be. Did a job this morning that I redid the flight since I was not happy with the first flight's focus. 

You will get a bit more time for exposure and processing if your camera orientation is 'in length' and not facing forward but it will increase your leg count and flight time.

Good luck

Thanks Antonie for sharing your setup. We have flown Skywalker 1900 for the past four years with some success but we have moved to the flying wing to get the camera front first. We fly missions of ~45 minutes on average and with our overlap and forward lap set at 70% this configuration means fewer lines.

We do not shoot in auto. We use a samyang 12mm lens which is manual, so all setting are made on the ground. The problem, as I am sure you know, is that with this setup flying at 12m/s and an altitude of 120m we only have ~4s between shots based upon the distance. When the groundspeed reaches 20m/s plus this interval is too short for the camera.

We managed to slow things down by lowering the trim_throttle to 30 but I think we will try to get this lower. Plotting groundspeed(GPS speed) vs throttle shows that it lowers to this level on the downwind leg but obviously does not go lower. Airspeed (from the sensor) varies much less of course).We will try 20 and see what happens.

We will also try crosswind again - last time we may have had problems with the general pid settings.

Thanks

Buddy, my point is that your camera takes to long to take the pic. The A6000 should manage an exposure at 1 second if not less. I use a QX1 at 1.65 seconds with a 20mm lens and a A6500 at one second with a 16mm lens. Maybe the issue is with your lens.

Good luck

OK maybe I am being too pessimistic about the camera. I must confess that I have not used the A6000 before. When using the A5100 we tried to set a max of 3s between shots - this is not the exposure time but the time between shots. If it can shoot repeatedly at 2s intervals for say 40 shots then maybe there is no problem(camera has a U3 sd so that should not be a limitation, but not sure what size the buffer is). I will be testing this soon (not today as the wind has now dropped). 

I'm using the same setup you and Antonie are. The camera manages to shoot at 1 per second. I have to agree with Antonie that your hold up is the camera for some reason.

Thanks Darrell,

I was basing my concern on recommendations not on actual experience!  I have been trying to use a DrotagX for geotagging and it recommends a minimum of 3s between shots (this could not be achieved at the ground speeds measured). I did a flight yesterday without the drotag and the camera had no problems shooting close to 1s intervals so I was overly pessimistic about the camera performance. The drotag will not keep up at that rate however, so my problem has not really gone away - I guess everything is a compromise :(

The other way you can slow down a flying wing is to increase the reflex in the wing and move the CG forward. This will create more drag and extra lift (to a point) 

For example when launching a flying wing it is normal to add 15% up elevon to give a stable launch at a low airspeed that would not normally be possible. What we do is adjust the CG  to a point in front of the defined location and add the Up trim with a 2 position switch. When at the correct safe height we switch the extra Up trim out and the plane flies normally. you can leave it in but the angle of attack will be greater and this may affect your images as they will be slightly "keystoned"

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