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.