Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


Not mass balanced & cable failure

Not mass balanced & cable failure

Not mass balanced & cable failure

I found that many certified LSA aircrafts and some standard FAR 23 certified don't have mass-balanced surfaces. I'm interested in how they are designed to show freedom from flutter, especially control surface flutter and if these aircrafts can handle a disconnected freefloating surface emergency (due to cable failure, for example).

If they are not prone to develop flutter in normal operation, how things may change if, for example, the aieron cable fails?

Thank you very much!

RE: Not mass balanced & cable failure

Hi SteveJeff4567 :

Some manufacturers under the LSA rules, have made ​​some aircraft without mass balancing in the ailerons control system.
Even have conducted studies and tests showing that it is not necessary such mass balance.
It is clear that the tension in the control cables of the system must be the recomended by the factory and
without any free play in the system because if that happens, may occur catastrophic effects.
Anyway in this case counterweights was installed later in the ailerons....

I enclose two links of the Hamburg Institute of Technology reports that may help you.



RE: Not mass balanced & cable failure

Ok, in generally, how at risk to flutter is a control cable failure? The study doesn't seem to take care about this problem.

RE: Not mass balanced & cable failure

Hi SteveJeff4567:

You are right. The study does not take into account even the risk of losing some cable tension or cable break.
The control cable without correct tension or failure may be one of the flutter issue specially if the ailerons
are not mass balanced. Remember the flutter ia a very complex phenomenon.
Read specially from page 4 of this NTSB report
This report is a good approximation to the truth.

RE: Not mass balanced & cable failure

Not really the main topic of this thread, anyway, actually the study posted above, this one, take into account the risk of losing some cable tension and as I found in the study there is no flutter even at low cable tension. So, it is somehow confusing. If there's no flutter at low cable tension, what caused those crashes?surprise The NTSB report says that low cable tension.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close