A Level 1 AOA clarification

"David CL Francis" wrote in message
...
I think Peter that an aircraft will climb if trimmed to the same angle of
attack that it was using in level flight.

Well, ignoring for a moment that I never meant to suggest anything about
what happens if you simply increase power without changing anything else
when just above stall speed... (my comments were simply about what
additional power *allows*...not what it *causes*)

You can't make that generalization. Changes in power affect elevator
authority (affecting trim), as well as necessary rudder input (changing
drag). It is entirely possible that when just above stall speed, an
increase in power will result in an increase in angle of attack, an increase
in drag, or both.

What you can say is that if the pilot maintains the same angle of attack,
but increases power, then the airplane will climb (I don't believe that
added drag from rudder will ever be MORE than the added thrust, but I could
be wrong about that). But that's not really what I was talking about.

It does this as long as the lift is slightly less and the speed drops to
produce _less_ drag and lift, leaving more engine power and thrust to
climb.

At an airspeed just above stall, a reduction in speed results in MORE drag.
There is a reduction in parasitic drag, but there is a greater increase in
induced drag, with a net increase in total drag (and that's ignoring drag
caused by the rudder and any other control surfaces that require a change in
position).

When climbing extra work must be done against gravity. That extra work can
come from increasing power or from reducing speed and therefore drag.

The extra work comes ONLY from a net surplus of power. A reduction in speed
is only guaranteed to produce a net increase in power available if the new
airspeed is higher than Vbg. It can sometimes also produce a net increase,
if the old airspeed was sufficiently higher than Vbg, and the new airspeed
is close enough to Vbg, even if less than, but you need to know more about
the old and new airspeeds in that case to say for sure what happens. More
importantly, a reduction in speed is guaranteed to produce a net decrease of
power available if the OLD airspeed is lower than Vbg (as it is when just
above stall speed).

Nitpicking point: wings do not create thrust! :-) You meant lift of
course.

Yes, of course. Thank you.

Pete