The Value of Bench Checking

[lmcwilli]

After several weeks successfully flying my 450 X, I lost orientation one day and crashed.

I had to replace: the feathering shaft, main shaft, the 3 collective servos, and torque tube.

So, I obtained all the replacement parts (including Spektrum H3000) servos) and put it back together again.

But before flying my 450X---and after I thought I had everything adjusted properly---I figured I had better take the main blades off and bench check the heli. I put a big pipe wrench through the skids to hold it down then “flew” it. I gave it barely enough throttle to get things moving---no more that what you'd give it before you take off.

Doing this I discovered three errors:

1. The swash plate motion was reversed. When the stick moved up, the swash plate moved up. In other words, when the stick was at 0, the main blades were at maximum positive pitch and, in actual flight, would have launched the heli like a rocket!
2. The tail rotor servo motion was reversed. Moving the rudder stick right caused counter clockwise rotation and moving the rudder stick left caused clockwise rotation. So, in actual flight, instead of the tail rotor countering the heli’s tendency to rotate counter clockwise, it would have augmented the rotation. I would have had an on-the-ground “explosion” as I tried to take off.
3. I also discovered that the range of motion of the collective servos needed to be restricted. This problem manifested itself as a clicking sound as the main rotor went 'round. At maximum elevator or aeleron extent, the swash was bumped against linkages. I was easy to adjust in the Beast X.

Since most of my limited experience is with micro heli's, I've been rather casual about pre-flight checks. If I fly a micro heli like my mCPX and something looks wrong, I just land (or crash) and no harm done. With the 450X, a less-than-thorough pre-flight check---especially after a repair--- can result in a lot of harm!

[Napoleon_Tanerite]

Originally Posted by lmcwilli

After several weeks successfully flying my 450 X, I lost orientation one day and crashed.

I had to replace: the feathering shaft, main shaft, the 3 collective servos, and torque tube.

So, I obtained all the replacement parts and put it back together again.

But before flying my 450X---and after I thought I had everything adjusted properly---I figured I had better take the main blades off and bench check the heli. I put a big pipe wrench through the skids to hold it down then “flew” it.

Doing this I discovered two “minor” errors:

1. The swash plate motion was reversed. When the stick moved up, the swash plate moved up. In other words, when the stick was at 0, the main blades were at maximum positive pitch and, in actual flight, would have launched the heli like a rocket!
2. The tail rotor servo motion was reversed. Moving the rudder stick right caused counter clockwise rotation and moving the rudder stick left caused clockwise rotation. So, in actual flight, instead of the tail rotor countering the heli’s tendency to rotate counter clockwise, it would have augmented the rotation. I would have had an on-the-ground “explosion” as I tried to take off.

Since most of my limited experience is with micro heli's, I've been rather casual about pre-flight checks. If I fly a micro heli like my mCPX and something looks wrong, I just land (or crash) and no harm done. With the 450X, a less-than-thorough pre-flight check---especially after a repair--- can result in a lot of harm!

DO NOT FLY THIS HELICOPTER YET

These helis do NOT like to be held down like that, and especially with the BeastX can display weird behavior that may not be representative of how it will behave in flight. It sounds like you accidentally set the head up for leading edge control on the blades-- I've done that before too, no problem. What you need to do now is verify all mechanical connections are done properly, and then DISCONNECT 2 MOTOR WIRES (doesn't matter which two). Power on the helicopter normally, and check control function like that. Go through the whole BeastX setup procedure. Most settings will be simple verification, but pay close attention to steps G, I, J and K.

[lmcwilli]

Thanks for your suggestions.

I did go through the BeastX setup procedure with two motor wires disconnected. But somehow I overlooked the two reversal mistakes. I've still got a lot to learn.

Now that I think about it, the only thing "flying" it on the bench clarified was the behavior of the tail servo (I found the Blade 450 X manual's rudder test on page 9 to be hard to visualize). But when I fired it up on the bench, it was obvious which direction the tail rotor was pushing.

The correction of my mistake with the direction of the swash plate movement, I discovered when I reviewed the setup check on page 9 the Blade 450 X manual. That was easy to visualize. Just a dumb mistake: throttle up means swash plate up---Not.

[RodneyK]

Another thing to keep in mind on the swash plate movement is that you need to make sure that both the AR7200BX and your transmitter are giving you the correct movements for the given input. You can have the BX set up right but have servo setups reversed, so it's important to not only do the "tilt the helicopter" step to make sure the the BX is reacting correctly but also check that aileron and elevator inputs from your radio move the swash plate correctly. The same goes for the tail direction sensor and your rudder stick movements.

[Talesin]

Wait... people don't do a control surface response check before every flight? Part of my standard routine. TX on, TH on, heli power, step back until full init. Control check cyclic, collective, rudder. Set TX down, strap the battery/wire, canopy on (for the batteries that can), tilt check, rotate check, good to go.

[lmcwilli]

Originally Posted by Talesin

Wait... people don't do a control surface response check before every flight? Part of my standard routine. TX on, TH on, heli power, step back until full init. Control check cyclic, collective, rudder. Set TX down, strap the battery/wire, canopy on (for the batteries that can), tilt check, rotate check, good to go.

Sounds like a good routine to go through. Thanks.

[RodneyK]

I do, too. I was just trying to point out that just because the sensors in the BX are all set up correctly and it will be moving everything the correct way to help stabilize the helicopter, there is still the opportunity for having controls reversed.

Originally Posted by Talesin

Wait... people don't do a control surface response check before every flight? Part of my standard routine. TX on, TH on, heli power, step back until full init. Control check cyclic, collective, rudder. Set TX down, strap the battery/wire, canopy on (for the batteries that can), tilt check, rotate check, good to go.

[lmcwilli]

Yes. I learned the hard way that a reversed servo can be disastrous. After repairing my Tarot 450 FBL, I failed to notice that the tail servo was reversed. When I started to take off, the heli spun out of control and self destructed: broken main and tail blades, bent main and feathering shafts, broken servo horns, and bent swash plate control arm. Quite an impressive crash for never having left the ground!

[RodneyK]

Unfortunately, I have had several "learning opportunities" similar to that.

[EEngineer]

Originally Posted by Knuckledragger

Unfortunately, I have had several "learning opportunities" similar to that.

And when they say to disable any mixing in your TX, THEY MEAN IT......LOL

[RodneyK]

Funny how those warnings are usually there for good reason, huh?

[EEngineer]

Originally Posted by Knuckledragger

Funny how those warnings are usually there for good reason, huh?

On my RF6 simulator, I had mixed rudder as master and aileron as slave to make piro's more axial......Somehow that got into my settings for the 450X.

You should of seen the weirdness that occurred when I lifted off.......almost had to run for it....literally, as the controls seemed all FUBAR'D........

It's hard to find TH when its coming after you....ROTFLMAO

[RodneyK]

It's hard to find TH when its coming after you....ROTFLMAO

Unfortunately, I have also experienced my 450X coming right at me and know that feeling! I was hitting TH as I was hurdling over the dang thing. I have no idea how it didn't clip one of my legs, I was really lucky.

[Napoleon_Tanerite]

Originally Posted by Knuckledragger

Unfortunately, I have also experienced my 450X coming right at me and know that feeling! I was hitting TH as I was hurdling over the dang thing. I have no idea how it didn't clip one of my legs, I was really lucky.

I've gotten so used to flying helicopters that I hit the TH switch when I was about to hit a tree.... with my JET!

[EEngineer]

LOL........you should have hit the TR switch......"thrust reverse"....lol

[RedOctobyr]

Originally Posted by Napoleon_Tanerite

I've gotten so used to flying helicopters that I hit the TH switch when I was about to hit a tree.... with my JET!

I'm sorry to laugh at/near your pain, but that's hilarious

[FailureToFly]

Originally Posted by Napoleon_Tanerite

I've gotten so used to flying helicopters that I hit the TH switch when I was about to hit a tree.... with my JET!

That is a classic! I can imagine doing the same thing as it's just ingrained in me now! Uh oh...click TH...

[kutyafal]

Man, really, you should've just launched the thing upside down and all would've been fine.