Category Archives: Field Tests

Death of a Good LiPo

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It’s a sad day today.

We went flying, as usual, at our usual spot. However, I made a fatal mistake regarding where I positioned myself.

Although we were told by Kanesh to not allow the plane to fly behind us, the reality is that weather conditions and pilot competence is not perfect.

As I was flying several rounds around the field, the wind picked up, causing the plane to fly directly over my head. Because I was standing right beside the road lined with trees, this meant that my view of the plane ended up being blocked by the foilage.

Because the Skysurfer had a tendency to roll to the left, I would normally hold the aileron stick to the right to correct this. With the plane being out of direct line of sight (and also because the white plane was flying against white sky), I lost orientation and let go of the stick, causing the Skysurfer to roll over and enter a nosedive at nearly full throttle.

The good news was that the plane missed the trees and flew between openings in the canopy, so that spared us the effort of rushing to get bamboo poles to try to recover the plane.

The bad news was that the plane crashed nose first into Old Holland Road, a proper paved driveway made of rock solid asphalt. This caused the foam at the nose area to disintegrate, crushing the battery inside. It also destroyed the FPV camera (cracked and dislodged the lens from the PCB)

It is truly sad that because of my incompetence, a brand new battery (that is famous in the drone racing scene)was destroyed. On the bright side, no servos were damaged. All the nose needed was a bit more fibre tape and it was back in action with a new battery.

Skysurfer Returns

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Over the past few day as I did my revision during recess week, I could not help but think about the plane’s inability to fly on monday. Sure, it was beaten up and the aircraft’s nose has already been compressed inwards, but this could not have contributed to it not being able to fly afterwards. After all, past experience with the plane taught me that all it takes is balancing of the CG before the plane is airworthy again.

To verify that what caused the plane to crash was actually the CG, I went out to old holland road again this morning(1st October 2020). The wind at the time of my arrival was calm, perfect for flying. However, rain was imminent in the distance (buildings started disappearing) and that caused the wind to pick up speed again. I had to act fast and got to work as soon as I could.

The first few flights involved throwing the plane without throttle to see if will glide. Once I was satisfied, real tests began.

The first powered flight was rather shaky. Using a lighter 1500mAh battery meant that the aircraft was tail heavy and I had quite a challenge controlling the plane. Note how in the onboard camera footage, the plane had a tendency to pitch up, and a hard landing caused the camera to be ejected from the canopy (no damage though):

However, it wasn’t long before the 1500mAh battery was expended (somehow, running the motor also caused quite a bit of voltage sag), leaving me with only the heavier 2200mah battery to fly with. That being said, it balanced out the CG perfectly!

I intended to stay for a while longer since the first storm in front of me had blown away (and MSS’s lightning website did not report any lightning activity) but a bigger storm behind me was brewing and I started hearing thunder in the distance (upon checking the MSS website,  massive lightning activity was reported around the Tuas area), so I had to pack up and call it a day.

Rise…and Fall of the the Skysurfer

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This session marks the third flight of our original Skysurfer. As it had been already tested and trimmed in previous sessions, we were expecting to do 1 or 2 warm up flights before mounting the node for tests.Unfortunately, Singapore being just 1 degree north of the equator means that weather conditions vary greatly from day to day. Below was footage of the second flight of the day that ended in a crash

The crash here was entirely due to pilot error: as the white plane was flying against white backdrop of clouds, the pilot over-banked the plane during a turn, resulting in it going inverted. Not realising this, he pushed the elevator forward with the intention of gaining altitude but that caused the plane to nose down instead because of its inversion, hence leading to a crash.

Note that the plane was also rather wobbly throughout the flight. This was because the last time the pilot flew was about 3 weeks prior and had zero stick time on the simulator due to school commitments.

As this crash occurred at significant speed (evidenced by the loud thud), it broke the plastic gears of the elevator and rudder servos, causing quite a bit of downtime as we replaced them (we brought spares, thankfully) and taped up broken pieces of foam.

Second Attempt…and Second Crash

After patching up the plane and waiting out a passing drizzle, we were ready for another go. We noticed this time that the plane’s CG had shifted: it could no longer fly with the battery right up in the nose as this would lead to a 737MAX nose down at launch. We suspect that this might be due to the additional layers of fibre tape used to hold the nose together after the first crash.

Shifting the battery eventually got the plane to a flyable state. Here is some onboard FPV footage(please excuse the choppiness; it was downscaled from 60 to 30fps):

For reasons unknown, the onboard camera stopped recording before the crash occurred.

Here is footage from the ground:

From the footage, it seems as though this crash was caused by the battery shifting forward mid flight, throwing the plane’s centre of gravity off balance. We deduced this to be the likely cause because as the plane pitched down towards the end of the video, the pilot reported having zero control despite having the control stick pulled all the way back.

After this, the plane no longer could fly as well as before. besides the CG being off, the wind was also picking up speed, which led to it being significantly more difficult to control the plane in flight. This, coupled with the fact that on the field for quite some time already (around 3 hours), we decided to call it a day, having about 2 out of 4 batteries left untouched.

With that, we strapped the collector node to a quadcopter belonging to Kanesh since the plane was no longer flyable. Below are two graphs – the first is of the data actually saved to the SD card of the ground node. The second is of the data transmitted from the ground node to the collector node (on a UAV). It worked as expected (after dealing with a timezone display issue where the timezone was assumed to be GMT+0730) – the sampled data matched the collected data!

Data from Ground Node

Data from Collector