Yes, many OWTs and myths have featured in this thread.
One that has bobbed it head up, but not been addressed is the one about the act of "increasing pitch" on the prop on final approach which then "increases drag" and helps you to slow down.
There is a widespread myth about the effects of increasing prop RPM on final approach. I have heard some pilots express the view that the whole reason for increasing the prop RPM is to slow you down (!).
Some pilots seem to think that, because you are driving the blades to their fine pitch stops, this then causes drag - in the rearwards direction - which then causes the aircraft to decelerate.
To these pilots, the obvious question is: so what happens on takeoff, when the blades are again on the fine pitch stops (for the early stages of the takeoff, at least). Is the prop again causing drag, reducing the acceleration?
It must be clarified at this stage that the kind of "drag" we are talking about here is the drag that is acting in the direction opposite to that of the propeller thrust force. I shall refer to this drag as "thrust-opposing drag". It has the same effect on the aircraft as skin friction and induced drag.
The wing produces lift + drag simultaneously, does it not?
A prop cannot produce thrust and thrust-opposing drag at the same time!
Yes, there is the induced drag that the prop blades produce, but the direction of that drag is such that, rather than opposing the aircraft forward motion, it opposes the prop rotation and creates the torque force that must be balanced by the engine torque.
But we are not talking about that drag; we are talking about the thrust-opposing drag that is
sometimes provided by the prop(s).
As it turns out, there is an element of truth to the OWT which says that "increasing prop RPM on final slows you down".
Sometimes, increasing prop RPM will indeed cause the prop to commence generating thrust-opposing drag.
And sometimes not. It depends on whether the torque has gone negative or not.
Increasing the prop RPM causes a reduction in torque. If the engine torque prior to the reduction was a small positive value, then the reduction can be enough to cause the resultant to be negative.
If the resultant torque is negative, then the prop will be generating no thrust but rather, thrust-opposing drag. This situation is also known as "back-driving", "discing", "windmilling" and plain old "negative torque".
The key ingredient to this outcome was
the small positive torque that existed before the act of increasing the prop RPM.
So, what this all means is: increasing prop RPM on final may
or may not cause an increase in drag.
If an undesired drag from the prop should be experienced at any time - not just while on final approach - the remedy is simple: just increase the torque until it returns to a positive value.
To do that, just push the throttle lever forward a touch! If a turboprop, just push the power lever forward a touch!
Those levers are part of a set of controls that set the engine torque. The other part of that set are the prop RPM levers. We knew that didn't we?