H Peacock wrote:
so the problems of losing IAS when turning downwind are far more pronounced.
You were doing fine, until you got to that bit. Maybe the head-banging, though, suggests you won't want to re-consider!
There is no difference between turning down upwind and turning downwind
at a given IAS. In both cases, a high rate of turn will result in loss of airspeed due to inertia and/or increased induced drag (the amounts of each depending on how the turn is achieved), and the loss will have exactly the same magnitude in both cases.
For conventional fixed wing aircraft flown according to IAS, there is no difference between upwind and downwind turns in steady wind conditions.
Harriers and helicopters are different! A hover stationary with respect to the ground is the extreme example. Turning infinitely rapidly from a 30 kts headwind to a 30 kts tailwind produces a 60 kts loss of airspeed. Vice versa produces a 60 kts increase in airspeed. This is the effect JF got very accustomed to and very much needed to concern himself about with respect to the wind getting under the tail. BUT, the IAS is completely different in each case. Turning downwind, you're starting with an IAS of +30kts. Turning upwind, you're starting with an IAS of -30kts. Try this now without keeping the Harrier (or helicopter) stationary above a point on the ground, and arrange for it to have a +30 kts IAS in both cases, and the loss of airspeed will now be 60 kts whether turning downwind or upwind.