How to deal with "Bumpy Air"

by Robert Vess

  Flying in gusty wind conditions or in hot air with noted thermal activity can impart tremendous loads upon the airframe.  It is not uncommon to experience load factors (g-loads) ranging  from  -1.5g to +3.5g or more when flying in “bumpy” air.  For some aircraft, the structure is not capable of withstanding much more than this!  And if there is any damage from a less than ideal landing or other undesirable operation or handling, the safety factor can be reduced significantly.


  When an aircraft experiences a gust, the effect is an increase (or decrease) in angle of attack that is proportional to the ratio of gust intensity to the airspeed.  And a sad fact is that a small plane encounters the gust more rapidly than a larger one due to obvious relative scaling .  So our model aircraft are “jolted” by this aerodynamic impulse more than their full-scale counterparts which cycles the structure more violently.  Another factor at play with our models is that an aircraft with a lighter wing loading will experience a larger vertical acceleration (g-loading) for a given gust intensity and thus will experience more structural stress!  So, it suffices to say that our aircraft are more vulnerable to the effects of air turbulence and gusts, particularly when one considers the fact that model structures are also generally less validated and tested than the “big boys”.  You couldn’t afford a model jet that was designed/built using full-scale certification practices!


  So what can we do about this?  Well, we can’t control the atmospheric conditions but we can control how we operate within them.  The increase in g-load due to gusts is directly proportional to the speed at which you are flying.  So, when it’s clear that gusty winds or bumpy air is present, just SLOW DOWN.  Every percent you decelerate from the initial speed is a percent reduction in load factor due to a given gust intensity.  This is really the only recourse you have to protect your prize aircraft from potential, unexpected structural failure.  It’s as simple as that! 

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