REFLECTOR: Runway length

David Staten Dastaten at earthlink.net
Wed Aug 2 17:20:06 CDT 2006


Beta is not reverse... and should not be confused as being synonymous 
with the concept of reverse thrust..

Beta range, which is more descriptive of turbo-prop installations, is a 
pitch setting at anything less than used for flight.

In turbo props, flight idle is the lowest power setting usually desired 
in flight, except in extenuating or emergency circumstances. However, 
since turboprops are governed to run at a fairly constant RPM and at the 
flight idle pitch setting, there may be enough thrust to cause 
acceleration on the ground and result in riding the brakes. Power/thrust 
is a result of increasing fuel flow to increase torque (and then 
increasing the pitch to use that torque).

So for ground ops you lift the thrust lever up and over the flight idle 
stop and into the beta-range to allow adjustment of thrust on the 
ground. In the air, this power setting (if even permitted in flight by 
the type certificate) can result in extremely high descent rates 
(sometimes desireable, sometimes not).

With piston power, simply pulling the engine back to an idle setting 
accomplishes the same effect if not more, than beta-range in a turboprop.

Now.. reverse thrust (which you COULD consider a component of the beta 
range)... that might be nice to have.. but have to be careful not to FOD 
the engine or prop.

Lawrence J. Epstein,MD wrote:

> What we need are props that go to full “Beta”.
>
> LJE
>
>  
>



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