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I like flying my aircraft fast

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1.2 I like flying my aircraft fast. If I stay below Vne, I won't have to worry about structural failure, right?


Vne is assessed at or near MTOW, with the cg at, or within, the fore and aft limits for the aircraft's specified category; it does not apply if weight, manoeuvring loads or cg position are outside the specified limits. As a maximum airspeed it applies only in smooth atmospheric conditions, for gentle control movements (using no more than perhaps 20 % of the available movement) and symmetrical aerodynamic loads; even gusts associated with mild turbulence or control surface movements greater than perhaps a few degrees travel will lead to some nasty surprises, if operating close to but below Vne. Remember that dynamic pressure increases with the square of the true airspeed. At high speed the controls are very effective, with a probability of over-control applying extreme loads to the structures. Asymmetrical aerodynamic loads, such as combined rolling and pitching, reduce the maximum allowable airframe load by perhaps 30%. Take care because some aircraft control systems provide inadequate feedback of the load being exerted; i.e. a high load can be applied with a relatively low stick force.


(The effect of gust loads is expanded in the section on wind shear and turbulence.)


If an aircraft is operated within its specified manoeuvring and gust envelopes and weight and balance limits — observing the limiting accelerations and control movements, and maintaining airspeeds commensurate with atmospheric conditions — then the only possibilities of inflight structural failure relate to:


  • improper modification, repair or repainting of the structure
  • excessive free play in control surface hinges, torque tubes or control circuits
  • cumulative strain in ageing aircraft, eroding the designed safety margin, remembering that structural fatigue may not have been adequately assessed at the aircraft's design stage
  • failure to comply with the requirements of airworthiness notices and directives
  • poor care and maintenance of the airframe.



Flight at airspeeds outside the design flight envelope (or when applying inappropriate control loads in a high-speed descent or, indeed, at any time) is high risk and can lead to airframe failure.


Be aware: deliberately exceeding Vne is the realm of the test pilot — who always wears a parachute! The following text is an extract from an RA-Aus accident investigation report:


"(Witnesses) observed the aircraft in a steep dive at what appeared to be full power. The port wing appeared to detach from the aircraft …


That wing had the attach points intact but had pulled the mountings out of the top of the cockpit. This action would have released the door, which landed close to the wing. The wings were intact but the ailerons were detached. There was no delamination of the fibreglass structure. The ailerons were not mass-balanced.


The aircraft was a conventional design being a high-wing, monoplane of composite construction. While the fuselage was a proven design the pilot/builder had designed his own wing, including the aerofoil section. The workmanship was excellent and there is no evidence of any lack of structural integrity.


The eyewitnesses reported seeing "a sort of shimmying" from the aircraft. It is believed that this 'shimmying' was aileron flutter, which led to the detaching of both ailerons. This same flutter condition would account for the massive forces required to detach the wing from the aircraft in the manner that occurred. Flutter could have been triggered by the wing aerofoil design combined with the manoeuvre the pilot was conducting, or from the aileron control design …


The aircraft suffered a massive inflight structural failure almost certainly caused by severe aileron flutter and the aircraft speed in the dive. Any flutter would have been exacerbated by the lack of mass balancing."


Taken from John Brandon's Tutorials:





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  • 8 months later...

The aircraft was doomed when the ailerons were lost. I think subsequent uncontrolled manoevers would have produced the high g forces to to rip off the wing. Controlling surfaces are hard to design because there is no math formula to go on. Size, shape, weight, balance, position all need to be tweaked to prevent flutter, by trial and error and a fearless pilot. The front canard of a Varieze is a good example. It is the most tested light aircraft around, including extensive wind tunnel testing. A canard origionally designed and already being home built had problems develop and a second canard was designed. I never took my a/c to vne but saw one pilot describe a twisting motion at vne. It's very light and would at first pass as something from a model plane. It is advertised as incapable of spinning but has been spun during testing with great difficulty. The recoverey is also difficult requiring I think about 20 turns. Not a good a/c for low level aerobatics.



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  • 3 weeks later...

Surprised that there hasn't been discussion about Va here. When I ask pilots about where, in moderately rough air, they keep their IAS in aircraft like RV's - the answer is often - 'just in the top of the green arc,ie just below Vno.' Va isn't very well understood. Pilots more often than not think of it as a fixed IAS - not a varying number based on your gross weight/clean stall speed. happy days,



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