King Air C90 Propeller Balence

[Fleep]

Can anyone give me some guidance on this matter,
There is no mandatory Requirement (That I can find) for carrying out a dynamic propeller balance on the C90, However the procedure for carrying this out is listed in Chpt. 61.
In this procedure it gives a range of allowable IPS. of vibe.

1. Is there a listed interval (ie. at Prop change)

2. How do I determine the IPS with out carrying out a dynamic balance ?

Thank you in advance for any input

Fleep

[Saint Jack]

Let me say from straightaway that I'm not a fixed-wing person but I believe my experience with helicopter rotor balancing gives me some limited authority to suggest an answer to your query.


Both prudence and 'best practices' dictate that you should perform dynamic propeller balancing upon installation of a new prop and reinstallation of the existing unit. Don't forget to index the prop to the flange and clearly highlight the attached balance weights so that other maintenance personnel don't move them. Subsequent to this, further dynamic balancing should be performed whenever you have a suspicion that it is required.


If the aircraft is flown by a number of different pilots, sooner or later one of them will comment on the propeller vibration level but if you're the only pilot then you may not notice the gradual rise in the vibration level and this is when it's best to establish an interval to accomplish the task. I would suggest you start at 200 hours and see what you get. If the IPS is essentially unchanged then extend the interval to 300 hours and so on.


One point to note, when you're performing the dynamic balance DO NOT stop when you reach the 'acceptable' IPS - keep going and get it as low as you possibly can - the airframe will thank you for it - a truly smooth rotor/propeller greatly enhances the reliability of structure and components.


Finally, your question "How do I determine the IPS with out carrying out a dynamic balance?" I believe the only way is to put the equipment on and do a run.

[Fleep]

Thanks for the reply Jack.
I come from a heli background also, therefore appreciate the benefits of smooth operation of rotating components.
Hartzell CMM standard practices only Recommends Prop Balance, But it does not specifically require it, Neither do Beechcraft, so this customer will always take the easy/cheaper option. Sadly!

[LASJayhawk]

Every time we hang a prop on a KA, we dynamically balance it, no ifs ands or buts. We've gotten props back fron the shop that have tested at 4+ ips.

All that shaking is hard on the airframe and the people in it.