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Tension Fitting (Angle and Channel) understrength mitigation

Tension Fitting (Angle and Channel) understrength mitigation

Tension Fitting (Angle and Channel) understrength mitigation

This is a question for aero stress engineers.

We have a few locations showing negative MS where an external load (modification) is attached to a fuselage through the skin into a new reinforced channel or angle type fitting. The stack-up of parts on the fuselage side consists of skin double (0.10in), original aircraft skin (varies but 0.085in typ), intercostal (0.063in) and the new reinforcement channel or angle (tension fitting).

The fastener tension analysis is conducted using 100% of the tension load on the end pad of the channel of angle fitting. BA methods (BM7024.01.03.03 Rev B) is conducted and the fitting fails in end pad bending. Typical margin is MS= -0.06.

Given the significant stack of material/parts which is there to assist in reacting the tension load l believe a valid mitigation is to show a load path for the excess tension loads. This can be done via an increase in the effective end pad thickness (lets call it tb(eff)) much in the same way a stress pad (contour pad or throat pad, depending on which version of English you speak) provides additional support.

I need some input into the viability of this mitigation approach and, if possible, a reference to quote to support its use.

Many thanks,

RE: Tension Fitting (Angle and Channel) understrength mitigation

Have you checked the LM stress memo's, which was probably the source reference of the BA manual you are using?


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