Golf-Sierra: I'll give this a try even if here are many better qualified participants. Bear with me
First: why is airspeed so relevant? (a) It is a measure of the performance of the aerofoil/airframe (stall/buffet/structural limits), (b) It allows ground speed and track to be calculated, (c) it is a convenient way to ensure separation of aircraft within the same moving mass of air.
a) correct, airspeed is basic for all aerodynamics.
b) only partly correct, as wind data is also a necessary input.
c) hmm...ground speed would be just as convenient, wouldn't it? At least for the purpose of calculating safe separation distances.
Has anyone ever stepped back and asked - given today's technology - what is the best way to achieve (a), (b) and (c)? A 'clean sheet' approach, without the legacy of the past?
a) angle of attack is in some respects just as useful. But to replace a pitot tube it would IMHO need to have a resolution better than 0.1 degree - not so easy to combine with 100% icing resilience I guess. And most AoA sensors I've seen are relatively delicate mechanically, compared to a pitot tube.
b) For realtime navigation, you need to use ground speed and ground track. VOR, GPS, and inertial methods all work independently of airspeed and have long since replaced airspeed and compass-based dead reckoning. For planning and routeing, fact is that fuel economics depend on airspeed, so it's most reasonable to use it, always together with wind forecast data.
c) radar, TCAS, and more recently ADS-B for ensuring separation.
I find it hard to believe there is no other way (as an additional, redundant system) to measure airspeed. Even yet another pitot tube - albeit a retracting one - could provide a working alternative if all the other ones fail. But has anyone ever thought about it?
If there was an easy solution, it would surely have been found by now. But I'd be interested to hear if this issue has existed for a long time. Or are iced pitot tubes just a recent result of beancounters ordering pilots to save on heating electricity? Surely not...
