Abstract:
The deformation of the flexible structure under aerodynamic loads at
subsonic high speeds due to the aeroelasticity phenomenon was not
considered in aircraft design until recently. Further studies showed that the
deformation might lead to structure instability and unsafe operation.
In this study, an aircraft already in operation, from the subsonic high speed
group, was investigated for the effect of these aeroelasticity phenomena. The
design specification data of the study Aircraft was used through reverse
engineering to analytically calculate the aerodynamic loads & review the
effects of the aeroelasticity on the Aircraft wing at ten speeds within the n-V
diagram limits.
The aerodynamic loads were investigated for the effect of trim. It was found
that the Lift along the wing span increased under the trim condition. This
subsequently increased the wing forces and moments
The computed divergence and flutter speeds when compared with the design
speeds agreed within 97% to 95% respectively.
The wing structure stability analysis showed a stable structure within the n-V
limits, but the skin near the wing tip has a safety margin of 30 % only. The
skin safety margin decreased to 12% when the maximum limit speed was
increased by 5%. It is believed that the Aircraft skin is a problem and might
lead to unsafe situation.
It is recommended to address this problem at current operation and future a/c.
At the current operation level to make the pilots more aware of the situation
through and notices to avoid operation near the maximum limit speed. The
notices can be through placards or retrofit of an oral warning system. At the
redesign level to include the outcome of the researches in progress and use of
the smart material
