So we all know the potential issue where the pitot tube and drain hole are blocked (presumably by ice in the normal training scenario), and if you climb your airspeed will increase and if you descend, yada, yada, yada. Well I'm preparing for my instrument ride and I have this annoying need to understand things, even (or rather, particularly if) my assumptions are wrong.
To wit:
Assume you were flying along fat, dumb and happy, and your pitot tube and drain hole became clogged with ice. You're on a 3-hour cross country leg going from an area of high pressure to an area of low pressure. As you continued along, and the static pressure on the static side of the system got lower and lower, your indicated airspeed would increase, correct? (And the converse going from an area of low pressure to an area of high pressure). If so, would it be by an appreciable amount? Is it possible that it might change by 10-20 knots? I was contemplating a scenario where in cruise over a long period of time, you might not notice your airspeed dropping by that amount, or if you did you might not think much of it. Meanwhile as the pressure gets lower and your IAS keeps creeping up, you keep reducing power and unwittingly slowing down. This could eventually become an issue.
I got to thinking about this because we all know the other "high to low" scenario, which has to do with what the altimeter would indicate if you don't change the altimeter setting when going from high to low pressure. But I've never seen the scenario with the airspeed indicator addressed.
Thoughts?
To wit:
Assume you were flying along fat, dumb and happy, and your pitot tube and drain hole became clogged with ice. You're on a 3-hour cross country leg going from an area of high pressure to an area of low pressure. As you continued along, and the static pressure on the static side of the system got lower and lower, your indicated airspeed would increase, correct? (And the converse going from an area of low pressure to an area of high pressure). If so, would it be by an appreciable amount? Is it possible that it might change by 10-20 knots? I was contemplating a scenario where in cruise over a long period of time, you might not notice your airspeed dropping by that amount, or if you did you might not think much of it. Meanwhile as the pressure gets lower and your IAS keeps creeping up, you keep reducing power and unwittingly slowing down. This could eventually become an issue.
I got to thinking about this because we all know the other "high to low" scenario, which has to do with what the altimeter would indicate if you don't change the altimeter setting when going from high to low pressure. But I've never seen the scenario with the airspeed indicator addressed.
Thoughts?
