More helicopter troubleshooting and information at http://www.heliwrench.com
Here are some tips to think about when having trouble balancing an Astar. These tips can also be used when balancing the twinstar with a few exceptions.
1. Check the yellow pitch link length. After initial rigging it should not be moved for any reason. Its measurement should be approximately 372mm bolt to bolt center line on thick sleeve installations. On thin sleeve installations (older style) it should be 378.5mm from bolt to bolt center line (On a twinstar the length is different). If incorrect length it will affect autorotation, overall ride and NR governor speed.
2. Check to make sure the blades were put on in the correct locations. Blue should be over the rotating scissors. When BLUE is placed forward over the nose of the aircraft RED is on the left and YELLOW on the right.
3. Check that the blade trim tabs are in the correct locations using a trim tab bending tool. You will find the correct tab degrees on the blade log card. Both inboard tabs are initially set to zero. Do not put back to zero unless you are starting over at nominal. These are the tabs that you are allowed to move for balancing purposes.
4. Check the rigging by turning hydraulics off while running on the ground. If the track picture changes, the main rotor controls need rigging with the appropriate rigging tool.
5. Check if you have weights on the blue blade. There should be zero. Only in rare occasions will you have weights on this blade usually because of something not correctly installed on the main rotor head. ex. frequency adapter upside down, interrupter in wrong location.
6. Make sure your interrupter is under red blade.
7. Check all main rotor head bolts for correct torque.
8. Check that windshield screws are tight.
9. Check your starflex ball joints for play (.016") max. If there is excessive play you may experience ground resonance.
10. Check that the frequency adapters have their arrows pointing up. Also check frequency adapters for wear. If you get a sudden increase in vibration and ground resonance take a very close look at them.
11. AVA lower bearing may be worn. This will cause an imbalance not track problems.
12. A starting point for weights on the blades is BLUE = 0, RED = 4, Yellow = 6.
13. Make sure to mount Lateral accelerometer on Mast. Mount vertical accelerometer at first bolt hole forward of where chin bubble meets the floor.
14. Track on ground moving pitch links looking at tip targets. Track in hover moving pitch links looking at tip targets. Adjust red and blue to yellow. DO NOT ADJUST YELLOW.
15. Adjust track at 60 knots - use pitch links. Adjust track at cruise speed or 110 knots Plot the ips from the vertical accelerometer on the tab chart. Adjust the required tab. always try to tab up. Remember up is minus on the chart. It is sometimes better to tab one blade at a time. (you can look at the tip targets as a reference but a perfect track does not mean a smooth ride)
16. Get the vertical to .2 ips. If you go lower than this the three per rev will increase.
17. If you have a balanced helicopter with a low ips reading and you still feel roughness in flight it may be caused by one of the following. - short shaft out of balance - pitch link rod end bearings - loose windshield screws - frequency adapter ball joints loose - trim tabs on the same blade in plus and some in minus - servo rod end bearings loose - Fwd tail rotor drive shaft hanger bearing mount cracked - Starter generator vibrating - engine vibration - Tail rotor out of balance.
I hope this information will help anyone having trouble with balancing an Astar. Please check your appropriate maintenance manuals before performing any work on your aircraft.
More information and helicopter troubleshooting at http://www.heliwrench.com
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