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HomeAircraftHelicopterHIROBOOther › Evo noise, behavior
10-15-2005 03:51 AM  12 years agoPost 1
freakyreef

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Kansas\Colorado border

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I posted this in the main, but thought some other Evo 50 owners might have some insight.
Evo 50, hyper, 600 woodies.
Here is a video clip with the noise in question. Unfortunately I didn't catch the behavior on tape. Listen to the sound of the engine, then the blades right before I start in with "Uh oh, Uh oh". I THINK I experienced blade flutter but not sure since I have never seen it before.
Here is what happened. Was in fast forward flight, gave full aft cyclic, then you hear the sound of the blades. The heli quickly oscillated. I immediatly dropped collective and brought it down fast. Post incident inspection reveals nothing out of ordinary....
Any guesses based on the sound of the engine and blades??
I didn't hear the engine wavering until I listened to the video. Any help would be greatly appreciated.
Freaky

Evo Uh oh

Walk on water long enough, eventually you will get your feet wet.

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10-15-2005 09:48 AM  12 years agoPost 2
mrNoodles

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Borlänge, Sweden

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Man that sounded like a chickendance?!

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HomeAircraftHelicopterHIROBOOther › Evo noise, behavior
10-15-2005 01:10 PM  12 years ago •• Post 3 ••
Leif

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USA

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If you put ANY full-cyclic input in conjuntion with a lot of collective you'll bog the head. Based on your description of the incident it sounds like this is what started the scenario.

At very low head speeds the Evo can start to wobble, and if you have lots of pitch this wobble can cause a boom-strike. The best recovery is to get the cyclics back to neutral and back off on the collective until the headspeed comes up. Carbon blades would help, as they're less prone to bending. You might also try tightening up the main blades a bit if they're loose in the grips.

In future, try to keep the headspeed up and be more gentle on the controls. You might put in some expo on the the cyclics. Also, if you're running without any weights in the paddles you could put the brass ones back in.

Leif

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10-15-2005 04:04 PM  12 years agoPost 4
freakyreef

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Kansas\Colorado border

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I had been doing the same manuever many times right before it happened.
I run expo and my ATV settings are mild on the cyclics. (still in beginner mode)
I am particularly curious in the sound of the engine a second or 2 before the "incident" the rpm wavered , up down up down, not from my input. I have been researching a bit last night and this morning and was wondering if possibly I suffered from the wah wah's.

Walk on water long enough, eventually you will get your feet wet.

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10-16-2005 03:41 AM  12 years agoPost 5
Leif

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USA

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Of course it's almost impossible to accurately determine what happened just from a sound recording.

Your engine bogged down as the "incident" was happening. Whether it did anything else is hard to say. Of course, it is possible to have an engine go lean during a hard maneuver for a number of reasons.

The Evo is actually very well behaved. It rarely suffers from the Woofs unless you are doing hard inputs while the headspeed is very low. If your headspeed is over 1700RPM and your dampeners are good the heli should behave itself.

Hope you get it sorted. The audio clip made it sound like a boomstrike. I've had the "machine-gun" sound on my old Nexus when performing high-G turns and horizontal pogo-style maneuvers. It definitely gets people diving for the deck and is actually a pretty cool sound. On the Nexus this symptom was the result of the interference between the tail-rotor wash, blade-tip and flybar airflows coming together. I don't get this as much with the Evo.

Leif

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10-16-2005 04:15 AM  12 years agoPost 6
freakyreef

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Kansas\Colorado border

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Thanks. I know asking for a definitive answer from a recording is asking the impossible.
I I braved the 30 MPH gusts today after my adjustments and couldn't replicate the results.
Things I did. Richened up 2 clicks, dropped the headspeed a bit (I think I was running high just from the sound...No tach yet ) After looking into my ATV settings a bit closer, forward cyclic was set at 85, while aft was set at 117. Lowered this a bit. Tightened blades
a bit.
Luckily I didn't bend the spindle from whatever it was. Hopefully it wont happen again. I am thinking a governor might be a wise investment.
Thanks for the info again. SOOO much more for me to learn!
Freaky

Walk on water long enough, eventually you will get your feet wet.

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