Sorry Gaz,
Density Altitude (DA) is a term that can cause confusion, especially if I try!
High DA is never a good thing for heli's. It's defined as Pressure Altitude (PA) corrected for non-standard temperature variations and whilst this is a my best definition, I think a more appropriate one would be: DA is the altitude the helicopter thinks its at and performs in accordance with this computable value.
Say you were using a landing point situated at an elevation of 3000', its possible with a low pressure and hot outside air temp to have a DA of 6000' due to pressure and temperature. Basically the heli would be working at 3000' but have the performance of being at 6000'. Higher you go the less dense the air is.
As for rotor speeds - small blades high enertia - I'm really racking my brain here but I seem to remember something like 410 with a beep range of -2 +9?? Hopefully somebody will remember.
Now I need to lie down.
Last edited by MOSTAFA; 9th September 2013 at 19:52.