Hiller Bump

[rdworx]

Hovering or turning hard stops etc.... I thought at first it may be moisture in the blades after sitting for 2 years, but we flew it for 40 minutes twice and the bump never left. It is shaking the instrument panel and tail noticably enough that one of the guys standing by the hanger said it was bad when we landed the last time. Any ideas?

[adam32]

Check the center bolt on the rear cross tube on the landing gear...

[bossman]

Hovering or turning hard stops etc.... I thought at first it may be moisture in the blades after sitting for 2 years, but we flew it for 40 minutes twice and the bump never left. It is shaking the instrument panel and tail noticably enough that one of the guys standing by the hanger said it was bad when we landed the last time. Any ideas?

Totally clean the head. Remove all old grease and re grease with the same ammount of pumps in all fittings. Check the blades and make sure the end caps and weights are still there and that something has not built a nest somewhere. More than likely, it is the grease in the head and grips. After sitting tied down at an angle, the grease tends to settle to one side. Depending on the type grease used when you parked the helicopter.

[adam32]

Hey Bossman, would that make the tailboom shake? I would think it would be more of a cyclic vibration if its a grease problem?

[bossman]

Hey Bossman, would that make the tailboom shake? I would think it would be more of a cyclic vibration if its a grease problem?

With the Hiller, as is with most small receip helicopters, anything can cause the tail to shake. What you need to look for is; is it a side to side shake, or an up and down shake. Tail rotor problems are most often felt in the peddals as a high frequency. The way that the "bump" was described, would lead me to believe that it is a main rotor or head problem. Could be wrong, but after sitting for two years grease tends to break down. I would totally disassemble the head, swash plate, grips, etc. and re pack all bearings. Do not take a chance and let the problem escalate. Another thing to look at would be, what kind of dampers does it have? If they are the oil filled type make sure the oil levels are equal. You'd be surprised at how much difference 6 ounces of oil makes. Remember that when you track and balance you deal with adding a washer here or there, so a difference in oil levels and amount of grease has a great effect.