Helicopter pitch change when orbiting around a fixed point??
Today I was given a lecture about flying a recce of a confined landing site or flying an escape out of a steep sided mountain valley, starting at an into wind position and turning down wind..
I was told that in order to maintain airspeed whilst turning down wind, the pilot must change the aircraft's attitude. I have observed this previously and figured that it is some sort of optical illusion given that you are flying in relation to the ground, and not in relation to the air. For example a rate one turn flown at 60kts on the ADI has no pitch change, it just looks like an egg over the ground if there is any wind. He went on to say that this is only because we are operating at low airspeeds (40kts). I would say "Low airspeed relative to the wind."
The lecturer went on to say that when flying this circular pattern, if no pitch change was made, then the aircraft would run out of airspeed as it went down wind.
An example was given of a 40kt pattern with a 30kt wind. He quoted 1/2x4500kgx(70^2-10^2) as the energy change that the aircraft requires to make it round the turn to downwind without losing airspeed. He is working on ground speed, which surely has no effect on us as long as we are still flying? The only problem if we don't pitch change and use lever is that we will lose position around the confined area, or hit the mountain side.
So...
What are people's thoughts on this? Can you please say let me know if you are a test pilot, engineer, aerodyanamics expert or pilot.
Many thanks..
al