Anatomy of a 126 km Flight


Last month I detailed my plans and preparation for an attempt at a 100km flight in a blog here.

Well yesterday the weather was ideal and my preparations (nearly) complete so I went for it and achieved a flight distance of 126km in a time of 2 hr 46 min 40 sec.

I can't attach my log file here because it's too big. It's 15MB and there's a 7MB limit. Any ideas how I can share it?

I exported the KMZ (2014-01-28%2006-32-40.tlog.kmz) to Google Earth and generated the following images showing the flight path, and the altitude/speed trace with some of the vital statistics.

3689570853?profile=original[Click image to enlarge]

The airframe is a Bormatec Maja with 2.2m wingspan. It’s not the most aerodynamic airframe, but its advantage is its payload capacity which allowed me to carry 21600 mAh 6P4S Li Ion batteries with ease.

I stripped out absolutely everything I didn't need including the obvious things like FPV cables in the wings, and thanks to some advice on my previous blog I also removed a few things I wouldn't have thought of such as the RC receiver case and airspeed sensor.

The advice I had from other DIYDrones users was invaluable but the biggest factor in improving the performance was the testing I did. For each variable I wanted to examine I would fly multiple laps at different settings then analyse the log files to find the best performing setup. I give more details on that in the original blog.

For the actual record attempt there were a few things I’d never done before. One was flying without the airspeed sensor (I had flown with it switched off, but never with it physically removed) and the other was the 4 cell batteries. Probably both those things were the cause of the trouble I had getting the plane to fly at the 13m/s (47km/hr) I wanted. Initially it was much too fast. Over the period of a few laps I adjusted the cruise throttle percentage, the cruise speed and the min and max speeds to much lower than I really wanted which bought the speed down (and pitch up) to where I wanted it.

Key Stats
• Distance: 126km (according to Google Earth)
• Duration: 2hr 46min 40 sec
• Airframe: Bormatec Maja
• Wingspan: 2.2 m
• AUW: 3.25 kg
• Battery capacity: 21,600 mAh
• Average Speed: 45.6 km/hr
• Top speed: 68.3 km/hr
• Minimum speed 40.5 km/hr
• Duration: 2hr 46min 40 sec
• Barometer creep: -6m

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  • Nothing strange about that. All aircraft have a CG range in which the will fly. In some, such as flying wings, it is rather narrow, in others it can be quite broad.

  • Hi Moglos, 

    I am wondering how a plane can have multiple CG and still fly on all of them without a problem?

    By the way, what is the motor size you were using with the prop 14 x 9? 


  • 300km

    Just a quick reply, I haven't watched your video or checked your details, but I flew with 7cm. I had trouble to start with too, it went into a flat spin a couple of times (which was actually not too bad, it was very gentle and slow with such big wings and no damage occured) and moved forward to about 4 or 5 cm and it flew well. Then through my testing I found a big efficiency improvement as I moved back to 7 or 8cm. 

  • HI Moglos, 

    What was the CG that you were able to fly with?

    We are having a serious problem with our Maja plane.

    The manufacturer told us that the CG is 7.5 cm, but it was all time heavy tail, and we were only able to balance it at CG 5cm.

    We did the first test with the pusher rear motor at CG 5cm and it was great and this is the video https://www.youtube.com/watch?v=6Y9DoGgcn98

    When we changed to twin motors, we were not able to get airborne and the plane was diving on its nose. It was at CG 5cm. We did upthrust by few degrees and it was flying good and this is the video https://www.youtube.com/watch?v=L9JsvfTBQ2Y

    But the manufacturer told us that the thrust angle should be at zero to get the longest flight duration. So, we went back and did the balance at CG 7.5 cm and the thrust at 0 degree and it was able to get airborne but with heavy tail and it crashed check this video: https://www.youtube.com/watch?v=4nufXWR6klY

    Both motors are counter clockwise.

    As you have experienced something like this, what do you think the solution should be?


  • Wow... that's impressive. Did you maintain any link to the craft while it was in the air, such as telemetry or RC? What was the maximum distance from launch that your craft went while in flight?

    @Rob, Gary: I think 10km is a good starting goal to shoot for with a multirotor. Having just built my first one I'm sure I could hit 5km fairly easily, so something higher than that is good, but I agree with Rob that 25km seems very, very difficult. I'd be interested in trying for 10km if it were a badge.

  • HI Moglos, 

    Which Motor and prop have you used in your flight? 

  • I saw some reviews of pilots and some of pilots locally have test them and the quality was not as desired.

  • 100KM

    "I did some reasearch few weeks ago and I found that Turnigy batteries are not made for long flight."

    What made you conclude the Turnigy lipos are not suitable for long flight?  I am not saying they are better than or even equivalent to the Maxamp lipos or Li-ions - just curious how you came to the conclusion.

  • MR60

    your calcs are correct.

    figure 46.2 grams for the 3400mAh NCR18650 B series.  Then add 2.4% to 6% depending on how well you add wiring/tabs to create the 3S and bind the battery together.  So figure a minimum of 980 grams for a 3S7P.

    With the cost savings, consider buying the battery welder from my prior link.  It makes the job safer and end product lighter.  Remember that zinc needs to be sized at twice copper.  I can help with that if you decide to go that way.

  • HI Moglos, 

    If I am doing right my calculation, I should be able to do it that way with the Panasonic 3250/3350 mah.

    3 batteries in series and 7 Parallel, Total 21 Batteries. The result will be like 3S  22750 mah?  isn't it? 

    The total weight will be around (47.5 x 21) = 997.5g, which is less than 1290g  by around 300g of 3S 22,000 mah lipo from maxamps.com and we need to calculate the cables for all the 21 batteries. I feel that the weight will be very approximate at the end. But the price will be a huge difference between 21 Panasonic Li-ion at 8$ each, total 168$, and the 3S lipo from maxamps at 425$

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