Airborne Video Recorders, Cameras, and Systems

HELICOPTER VIBRATION IN ANCHORED CONDITION

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Birdy
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Re: HELICOPTER VIBRATION IN ANCHORED CONDITION

Postby Birdy » Sun Feb 28 2016, 03:25

Controls are direct link FS.

Yes, 1 per is either track, mass or chord.
But the 2per id assume are airodynamic because at hover, its dead smooth.
If it was mechanical, wouldnt it be there all the time?
The only thing that changes between hover and forwards is the disc AOA, and to a lesser extent, the angle between the disc and frame.
Flying spanner
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Re: HELICOPTER VIBRATION IN ANCHORED CONDITION

Postby Flying spanner » Sun Feb 28 2016, 04:58

Sounds like pretty normal control feedback to me. Some helicopters use the friction on the swashplate to isolate the control forces from the head. If yours has friction maybe it's a bit loose.

If you wanted some sort of aerodynamic reason why it's smooth in the hover and not in forward flight. Here it goes, control forces are generated by the couple that is made by the centre of pressure and the centre of gravity of the blade. In the hover the change of force in this couple would be limited (little feedback). After and through translation there is a large change in this couple between the advancing and retreating blades and you would get a 2per feedback. If there is nothing to isolate this you will feel it in your stick. Thats my thoughts and ramblings anyhow.
Birdy
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Re: HELICOPTER VIBRATION IN ANCHORED CONDITION

Postby Birdy » Sun Feb 28 2016, 07:18

Thanx FS.
Is what you discribe the same as feathering inertia, or just the 2per as in the old Hui, only on a mich smaller scale?

The only friction on the cyclic is for locking down.
Besides, i dont like any friction on any control.
If i sneeze, the machine jumps. ;)

I dont see the small amont of shake as an issue, but if there was somethn i havent thought of, id like to know.
As you say, its more n likely just the usual inherant 2bl 2per.

Thanks again for your time.
Flying spanner
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Re: HELICOPTER VIBRATION IN ANCHORED CONDITION

Postby Flying spanner » Sun Feb 28 2016, 08:07

Birdy,
The Huey gets 2pers induced into the airframe. They do not get control feedback because they are hydraulically boosted controls. So you feel a chatter through your airframe, not your stick alone.

Because you have a direct link to your head, with no isolation whatsoever. Any feedback (2:1's that you can't help) from the head is going to be at your stick.
Birdy
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Re: HELICOPTER VIBRATION IN ANCHORED CONDITION

Postby Birdy » Sun Feb 28 2016, 08:41

Yep, i savvy that mate, just wanted to be sure there wasnt something id missed. :)

Early on i had a pare of not so smooth rotors.
The collective origionaly had friction, but i replaced it with an adjustable trimm spring.
The first thing i noticed flying on the spring was how much smoother the ride was, then i twigged, wen i saw the collective 'bouncing' slightly on the spring.
Wound friction onto the collective and it stopped bounceing, but then i could feel it through the machine again.
As you say, transfered.;)

And the Hui realy rattled, my eyeballs were still bouncing wen we landed. :(
ashimaero
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Re: HELICOPTER VIBRATION IN ANCHORED CONDITION

Postby ashimaero » Mon Feb 29 2016, 02:19

ashimaero wrote:Hi,
A helicopter is anchored , and its lateral vibration is high
Track is well within the limits and tried many mass balance but still its not reaching low level of vibrations.
Could anybody suggest what should be look upon?
Its a hinge less rotor with precone....

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