On Sep 30, 9:42*am, BeechSundowner wrote:
On Sep 29, 9:29*pm, D Ramapriya wrote:

Thanks, especially for the above bit. Don't know if it's because
someone once told me or something I'd read somewhere but I was under
the impression that when flying and if you didn't have external visual
references of the ground, there's NO way that a pilot can know the
airspeed of his aircraft.

Visually, you are correct and even "sensually" (feeling), while IMC
there is no way to tell speed or what direction the nose of the plane
is pointed (up, down, right or left). *The instrumentation is the only
source of information you have telling you what direction the ground
and sky points to.

With regards to airspeed, there are other clues to be watched for
airspeed besides the airspeed indicator and one is engine RPM.
Generally speaking, under normal flight attitudes, the engine RPM will
increase as you point down which subsequently means your airspeed is
building. *You hear this increase just as if you hear the engine noise
level go down, that would normally indicate the nose of the plane is
pointed up and your airspeed is decreasing.

Even under the hood as one approaches the stall or slow flight in
general aviation airplanes the controls are really soft -- little bits
of pressure make for large excursions. One should not depend on those
kinds of clues when there is no outside visual reference (that by the
way is LOT different than being in IMC) but it from a sensation
standpoint is pretty much like waving an oar in air instead of in
water. At cruise speeds the yoke has a certain 'stiffness' that is is
largely gone at lower airspeeds. Absent a working airspeed gauge
because you might have driven the pitot tube into a seagull of
something, the link between manifold pressure, RPM, and pitch attitude
is a pretty reliable indication of airspeed for a given airplane
configuration.