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Aileron flutter


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I have a high-time (1500-odd hours) 160. Recently we have run into a problem at >100 KIAs which we think is (incipient?) aileron flutter. Rattle clatter, vibration in stick and wing shake. A bit on the scary side. We found that the aileron hinges were pretty sloppy, so we tightened them up with fatter pins which dealt to most of the hinge slop. However, a subsequent test flight showed the problem was no better (arguably a bit worse), so we looked at the aileron cables. These also seem to be a bit on the sloppy side and will be replaced.

 

Has anyone run into this sort of thing?

 

I have since heard that cables are supposed to be replaced at 1000 hours ..... ?

 

 

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it is strongly recommended that you positively identify the cause of and solve the problem before proceeding further. If it is flutter, you will get very few chances before the surface fails. Check with the factory.

 

Have you recently painted or otherwise changed the mass of the ailerons or Elevator?

 

Are these surfaces mass balanced?

 

Cheers

 

John

 

 

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it is strongly recommended that you positively identify the cause of and solve the problem before proceeding further.

Agreed. Good idea. That's why I am replacing the hinges and cables. I was just wondering if anyone else has had a similar experience.

 

Have you recently painted or otherwise changed the mass of the ailerons or Elevator?Are these surfaces mass balanced?

This is a factory-built J160C. No to both questions.

 

 

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Ian ,

 

The symptoms you describe are unusual and should not be tolerated . Some simple checks will reveal where the problem is , such as having someone hold the control column firmly while another tries moving the aileron ( in the up,down and neutral positions ) Also remove the perspex cable clamp inspection cover under the wing ,to ensure the cable clamp is the correct one for that particular cable, and is firmly located . Another check would be to unbolt the spherical bearings at each end of each control cable and check for full travel ,any sloppiness or uneven resistance in the cable . Maximum 'slop' should not exceed 3 mm . Also check for control column looseness , and any movement in yoke at rear of column where the aileron cables attach . Any one ,or a combination of these faults ,will result in 'flutter' and should be rectified..... " before next flight " . At these hours I would also be checking the wing root ,and strut attachment bolts , by firmly shaking the wing to detect any movement .

 

Bob

 

 

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The symptoms you describe are unusual and should not be tolerated ... Some simple checks will reveal .....

Done all that. That's why I am replacing the hinges and cables.

 

 

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I think the system relies on being fairly "playless". Thee ends of the outer cables must be secured properly. The push pull cables will wear. Holding each aileron one at a time with someone else applying a reasonable force on the control stick would be a good check for play and security. Nev

 

 

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I think the system relies on being fairly "playless". Thee ends of the outer cables must be secured properly. The push pull cables will wear. Holding each aileron one at a time with someone else applying a reasonable force on the control stick would be a good check for play and security. Nev

That's pretty much what was done except we held the stick and moved the aileron. Aileron hinges wear too.

 

 

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Either way will prove the hinges. You would do an elementary version on each preflight. ALL controls should be checked for full and free movement, and that they move in the correct sense. Seems a bit basic but some get complacent. Nev

 

 

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I have had this problem in a J230. The problem I had was caused by the actual aileron adjustment, if both ailerons are both adjusted too high then when one if under fight load the other will vibrate as when they are adjusted high there is more play in the cable, see the jab manual for the adjustment and make sure that the aileron are correct, you will need to get an average as it depends on the quality of the build. I am a level 2 and after adjustment the test flight showed the problem solved. This was on a low hour aircraft.

 

 

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Replacing the pins did make a big difference - the hinge slop (rattle the aileron up and down at the hinge) is just about all gone. The replacement wires were 2.4 mm and the ones they replaced were something like 2.2. There is still appreciable slop aileron <-> stick, so I will replace the cables and see where that gets us. I have bought new hinges, but replacing them is a major PITA. If replacement cables sort the problem I will defer hinge replacement until winter .....

 

 

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The original stuff looks like spring steel (it's magnetic). The replacement wires we have put in for now are bronze. We had some suitably sized (fatter) bronze wire. It's not going to wear out or break in five minutes and I will be replacing the hinges anyway in the not too distant future.

 

 

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The right size and correct wire is the type used in model planes for the servo control rods. My plane also had the incorrect size wire in it, the aileron adjustment was the problem in mine, if you hold the aileron in one hand and the shaft of cable in other and move aileron for play you will see that there is more play in the upper position than in the neutral position or low position. If the ailerons are both high it will vibrate.

 

 

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The right size and correct wire is the type used in model planes for the servo control rods. My plane also had the incorrect size wire in it, the aileron adjustment was the problem in mine, if you hold the aileron in one hand and the shaft of cable in other and move aileron for play you will see that there is more play in the upper position than in the neutral position or low position. If the ailerons are both high it will vibrate.

It wasn't me flying - the plane is having some hours flown off after a mod (changing to a 912ULS) and it's the test pilot who tells me this. The problem did not go away when the hinge wires were replaced, although that did get rid of just about all the hinge slop. So we're doing the cables too. The 912 thing has worked out well so far, although both time and cost estimates were ludicrously optimistic as one expects in aviation ......

 

 

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Ian ,Was the flutter there before changing to the Rotax ?

Bob

Not that I was aware of ..... any time one got over 100 KIAs things rattled and buzzed. I did not identify anything as incipient flutter. I wasn't in the habit of flying at over 100 KIAs because that was over 3000 rpm and I couldn't be bothered with everything sounding like it was working so hard. The slop in the aileron cables is for real so that will get fixed. I can't see how the Rotaxification has anything to do with it.

 

 

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I have a high-time (1500-odd hours) 160. Recently we have run into a problem at >100 KIAs which we think is (incipient?) aileron flutter. Rattle clatter, vibration in stick and wing shake. A bit on the scary side. We found that the aileron hinges were pretty sloppy, so we tightened them up with fatter pins which dealt to most of the hinge slop. However, a subsequent test flight showed the problem was no better (arguably a bit worse), so we looked at the aileron cables. These also seem to be a bit on the sloppy side and will be replaced.Has anyone run into this sort of thing?

 

I have since heard that cables are supposed to be replaced at 1000 hours ..... ?

Hullo Ian. If your J160 is a few years old, it will likely have been manufactured without aileron hinge gussets. On my aircraft, I noticed cracking of the gel coat, this indicating that the pre-mould strip that the aileron hinges mount to, was flexing excessively.

In conversation with Jabiru, I proposed fitting triangular support wedges beside each aileron hinge. The reply was, "we build them that way now and we will send you some wedges free of charge".

 

Pages 168 to 172 of the J160 Constructors Manual will fully explain what I am referring to.

 

Cheers Fred

 

 

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The gussets will not fix the flutter problem in the ailerons nor will replacing the aileron cables , I would turn the both left an right aileron cable rod ends in two turns, two turns in will not effect anything easl but lift the ailerons up out of the air flow an should stop the flutter.

 

 

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The gussets will not fix the flutter problem in the ailerons nor will replacing the aileron cables , I would turn the both left an right aileron cable rod ends in two turns, two turns in will not effect anything easl but lift the ailerons up out of the air flow an should stop the flutter.

We lifted them a bit more than that - used up all the adjustment on the cable - and it reduced the flutter considerably. Funnily enough if you read up light aircraft and aileron rigging/flutter everyone talks about droop not lifting. Go figure. Anyway we have looked at the amount of aileron cable play on a couple of other Jabs on the field. Both were appreciably less than what I have, so we expect that the new cables to sort things.

 

 

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