Generally you can get less than 0.2 IPS with most electronic
balancers.
The amount of vibration varies with rotor systems and airspeed and how
good you are in using the balancer. You have to balance for three
conditions:
1 100% rpm no collective pitch
2 Hover
3 forward flight
In that order. If you try any other order you will never get all
three conditions to balance. Note that tracking problems also shows
up as vibration so fix tracking first.
Most people think that anything below 0.2 as smooth and 1.0 and above
as real rough.
0.1 IPS today may be 0.3 next week since bug splatters will affect the
balance of the tail rotor. I used to balance a Hughes 269 tail rotor
and the difference between 0.1 and 0.2 IPS was 0.1 grams which is only
a few bug splatters.


On 21 Jan 2007 07:55:46 -0800, "subhash" wrote:

can anybody tell me where is the documentation or mil-std or
airworthiness directive for determining helicopter main rotor and tail
rotor vibartion limits.

i have a bearingless main rotor and hingeless tail rotor aircraft. i
want to know what are the limits of tail rotor vibrations for a
hingeless tail rotor helicopter ? is it different from articulated
rotors? how about the mail rotor lateral and vertical vibration limits.

i searched mil-std-810f, mil-std-810d as wee as aeronautical design
standard ADS-27A -SP.

The information i got was not clear.

thank u.