Sun, 3 Apr 2016 08:00 08:00

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Gary Townsend

(13-18 mph) Moderate breeze

Align Trex 550E
3 flights
Avg. flight time 00:04:30
Not specified


I decided to only take the Trex 550 today so I could further test and play with the SK720BE and GPS2.

In general the unit did its job as it did before during my 1st testing session with the setup. Also, the software update in the GPS2 definitely cured the height variation that the heli was displaying during position hold during my 1st testing session. It rescued from all orientations, but there were problems. I had my spotter with me, and we only tested the rescue system when there were no people or obstacles within or close to the flying area.

Problem 1) The height at which the hard deck was activating was varying. It was set to 9 metres, but the rescue sometimes kicked in a few metres lower than this, and on one occasion during rolling it even rescued way higher, perhaps more like 15 metres at a guess.

Problem 2) This next part is quite serious in my opinion. On three occasions the hard deck rescue activated, but height and position control didn't work, resulting in the heli flying without the pilots (me in this case) stick inputs controlling the heli. Now it is true that after a hard deck rescue is complete, the pilot then needs to flick the GPS switch to manual to take back control, and for the 1st two incidents this is what I did, but for the 3rd one I flicked the wrong switch. There are various built-in safety aspects which shut off the rescue system altogether so that it doesn't attempt a rescue in the first place when something about the heli or the system isn't right, such as very high vibration, or loss of GPS lock. The flight data shows 17 to 18 satellites so the GPS lock was very good, and the super bright LED was blue. As for vibration when it gets too high, the system is supposed to make the super bright LED flash red. I have no idea what caused the position and height control to fail after the initial/orientation part of the rescue.

I've read that other rescue systems which don't use GPS control, only lockout control from the pilot for about 2 seconds, or like the NEO whereby you regain control by moving the sticks (which I've read is a problem for some). The problem with the Skookum SK720BE and GPS2 hard deck rescue that I experienced, was that you have to manually flick a switch to take back control. This is actually a good thing when the rescue system works as designed, since the heli rescues, yaws to tail-in, and holds position (but gains altitude).

Anyway I crashed whilst locked out of control during a partial and failing rescue attempt, since the GPS was not holding the helis position or controlling the height. If it had been on a 2 second preset and given control back it wouldn't have happened, but the point is, it shouldn't need to give back control if it works correctly. I understand that it's designed to disable the rescue functionality when something is wrong, but making some kind of attempt and locking out the pilot indefinitely until a switch is flicked is dangerous, and not as designed either.

More details can be found here: http://www.helifreak.com/showthread.php?t=739789 (Someone else started the thread since they also had their SK720 and GPS setup go wrong. My post is #3)

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