Poorly stated; corrections inserted.

At 23:10 17 May 2008, Nyal Williams wrote:
>Way back when ... there were terminal velocity dive brakes on gliders.
(I
>believe another term was DFS dive brakes, but am not sure about that).

>These brakes would hold the glider below VNe in a vertical dive. At
some
>point, as air foils became thinner, manufacturers agreed that the air
>brakes would be designed to hold the glider below VNe at a 45 deg.
descent
>angle. I believe this was sanctioned by JAR, IGC, or some such.
>
>Spoilers will place no limit on speed and [will not be effective] in a
steep or

>High Parasitic Drag Approach, whereas airbrakes can be.
>
>No one has mentioned an important difference between flaps and
airbrakes
>(whether spoilers, divebrakes, airbrakes, or your term of choice).
This
>difference is the effect had on closing them after having established
a
>stabilized descent under their use.
>
>Retracting the airbrakes causes the stall speed to be lowered and the
>glide angle to improve. If you are low and slow, retracting improves
>EVERYTHING.
>
>If you are low and slow and retract flaps, stall speed goes UP [the
lift DECREASES]
and you
>might find yourself in the woods, creek, fence, or whatever is short
of
>the touchdown point.
>
>
>At 13:53 17 May 2008, Tony Verhulst wrote:
>>user wrote:
>>> I'd continue to use them interchangeably .....
>> > If during a positive control check the pilot corrects your
call
>>> of "spoilers," look under the wing for the extra
>control surface.
>>
>>Yes, I've seen at least 2 books (FAA Glider Flying Handbook and
>Russell
>>Holtz's Glider Pilot's Handbook of Aeronautical Knowledge)where
the
>
>>writer claimed that if the ..um.. "device".. extended
top
>surface only
>>it was a spoiler and if it extended from both survaces it was an
air
>>brake. Seems dubious to me.
>>
>>Tony V LS6-b "6N"
>>
>