King Air = pressurised turbo prop
Pressurised turbo prop = increased operating altitudes
Increased operating altitudes = increased difference between IAS/TAS
For that type of aircraft people generally talk about speeds in terms of TAS hence the questions. 180kts IAS does not necessarily equate to 180kts TAS (or GS for that matter) and therefore if you are only thinking at 180kts you might be quite uncomfortably behind the aeroplane - especially on descent...!
Anyway you probably get the drift by now...!
