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HomeAircraftHelicopterHelicopter Main Discussion › strange aceleration at start up????
10-13-2005 03:40 PM  12 years agoPost 1
Luis104

rrApprentice

Caracas / Venezuela

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Yesterday after starting up the engine of my Raptor 30, the engine was acelerated very high. On my radio, the thottle was in low position (normal mode) the side sliders of my Optic (throttle and pith adjust) where in low position; and the throttle cut wasn´t working. When I saw the throttle servo, it was almost half throttle opened; after turnit of I start the engine again and it was a little acelerated, I had to trim down the throttle to fix this. On previus flights, this never has happened.

At last I start acelerating to lift of, and I notice the last half of the muffle rotating up. The muffler screw wasn´t tight enouf. After fixing this everything was fine, and I had a good flight, but I´m still worried about the strange aceleration at start up.

This is my throttle configuration (normal mode)
T-curv: 0 30 55 79 100
T-cut: -20
T- trim -25
Everything works fine with this configuration. I´ve had good flights with this configuration.

I´m using an Optic 6 with a Hitec Q-PCM 7ch RX. Is it possible that the strange aceletation was created due to some kind of interference??
If I´m not wrong, PCM technology get´s fixed to the last position it had when some kind of error or interference happens, am I right??? is this what happened? (I think this is what happened) or maybe this has something to do with the muffler untight ?????

please help. I´m new to PCM technology and I´d like to know about PCM technology. how does it works????

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10-13-2005 05:30 PM  12 years agoPost 2
Leif

rrElite Veteran

USA

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It's called a lean run.

The loss of muffler backpressure results in less fuel getting to the carb, since you don't get effective fuel pressure from the muffler pressure tap.

The result is an engine running lean, which caused the accelerated RPMs. This has nothing to do with your radio.

Fix the muffler problem completely before flying. Running lean can quickly destroy your engine.

Leif

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10-13-2005 06:18 PM  12 years agoPost 3
Luis104

rrApprentice

Caracas / Venezuela

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thankyou for your reply!!!!! everything was goor after fixing the muffler.
I still whant to know to know If the PCM technology get´s fixed to the last position it had when some kind of error or interference happens.

thankyou

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10-13-2005 06:36 PM  12 years agoPost 4
Leif

rrElite Veteran

USA

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Most PCM systems have a "failsafe" feature.

You program the behavior of the failsafe at the transmitter. It is up to you to decide what you want each servo to do if a lockout occurs. Typically, pilots will program their failsafe so that most of the servos remain in their last position except the throttle servo. That is typically set to move to a reliable idle position.

This behavior results in a "safer" behavior of the model when communciations from the TX fail. Rather than having the heli doing unpredictable things at high power out of control, the heli will go to idle, but will remain in whatever flight orientation it was in before the lockout. Since lockouts are typically a short-term thing, it is usually possible to recover once control is regained. I've seen what PPM (FM) systems do when you get a radio hit, and it isn't a pretty sight.

When the PCM receiver is initialized during power-up, it receives the failsafe program from the TX. If communications with the TX subsequently fails, the RX will perform the failsafe program.

Hope this helps explain things.

Leif

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