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Author Topic: Pre-flight Control Checks  (Read 133 times)

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Online Deerslayer

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Pre-flight Control Checks
« on: September 27, 2019, 07:30:32 AM »
Do you faithfully perform a pre-flight control check before every flight? If not, then why not? Doing so may save an airplane or prevent an injury.

When doing this check, you don't just power up, wiggle the sticks and then give 'er. Stand behind the aircraft. Go through each control motion, to its extreme, one at a time and think it through. If you have multiple Flight Modes or Mixes, verify each one. Something might have happened since your last succesful flight and now is the time to find out if things are not exactly right.

Pilots of full scale aircraft are taught from their first day to do proper checks, even before they know how to fly. Normally, the first flight of the day requires special attention. In my gliding days, one person performed and signed off on the Daily Inspection. Each flight then involves a pre-flight check by the pilot themselves.

A strange thing happened to me recently that proves the value of doing a thorough pre-flight control check:

WARNING , this is another of my looong war stories!

I had recently installed a Guardian stabilizer in my Timber X. Of course, I had thoroughly checked everything on the bench as well as at the field. Before each flight! The plane was flown a number of times over the course of several days, using my various Flight Modes and Guardian Modes. I honestly believe that I had done thorough pre-flight control checks prior to every flight, but, I am far from perfect so there is no guarantee.

So, I got ready to fly, powered up on my field table and proceeded through the control checks. Problem! Why do the Ailerons each go full Up, appropriately when functioning as Ailerons, Flaperons or Spoilerons, but do NOT go down past the Neutral point? How long has this been going on? Surely, I would have noticed this on a previous flight, although this plane has control surfaces the size of barn doors, and I had just been flying rather casually, so perhaps this is not a sudden change? Is it intermittent?

I went through several shutdown and power up cycles. Same problem. Had I messed up one of the parameters in either the tranemitter or the Guardian? No, I had not touched either. I reviewed my transmitter mixes, etc., vs the paper document I keep for each model.

Back to the bench!

The chain of command for this plane consists of:
 Pilot - Tx - Rx - Guardian - Aileron Servos
Where is the fault?

Transmitter - I had already confirmed, via its Monitor screen, that the outputs were 100% correct for all commands to Ailerons (as Ailerons, Flaperons, or Spoilerons) for each Flight Mode and Mix.

Servos - Each Aileron has its own independent servo and channel, so I unplugged one and used my servo tester to ensure that it had 100% range, in both directions. This worked OK, as was expected, but you need to cover all of the bases.
Receiver - I then plugged that one servo directly into the Rx, thus bypassing the Guardian for that channel. This worked perfectly, so now we know where the problem lies. It is within the Guardian!

Guardian - I connected it to the PC via USB, and ran its setup utility, with the plane also powered up.  All of the Guardian parameters appeared to be normal, yet there was the problem .

I removed the Guardian, connected the servos directly to the Receiver and re-checked everything. Ready to go flying now

The mystery remains; however, I still intend to solve it. This Guardian will be  connected to a test Receiver on the bench and to at least one servo. Presumably, the problem will show up there. Then, I will do a Factory Reset or such to see what happens.

I bought my first Guardian several years ago, when they first came out. This is my third one, having picked it up from a friend for a mere pittance. The others have performed flawlessly in several planes. I will find out if the seller of this latest one ever actually used it and, if so, did he notice any peculiarities. I am not complaining, just trying to understand what may be going on with this unit.

« Last Edit: September 27, 2019, 10:14:27 AM by Deerslayer »
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