I don't agree to the HV graph indicating the IAS.
Consider this .... even though the Y axis of the graph states this as IAS, and the conditions for the 'Avoid area' curve are dependent on the Density altitude and NIL wind conditions (which in any case has to be stated for its validity) doesn't it become a GS axis?
You may also like to consider the factors considered for drawing and validating the various segments of this graph.
The IAS/EAS (in case of helicopters where the compressibility plays a limited role in performance related issues) usage in the manuals are for aircraft 'performance' related factors... TAS would be valid for reasons of navigation.... generally speaking.
Nevertheless, if the IAS values read from graph are valid for a given density altitude it would mean that the TAS has been reduced to be read IAS !
Last edited by peeush; 20th Jul 2011 at 17:59.