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The pitot-based system cannot. It measures speed relative to the air, not ground speed. Again, the pitot A/S sensors are used for fly-by-wire FLIGHT-CONTROL, not nav.

Earlier, just after the crash, I found some comments quoting Air France pilots discussing the sequence of "automatic fault messages" received via satellite link. The thrust of the conversation revolved about a signal from the "NAV" computer which indicated a rapid change in "vertical velocity". They described the computer as being a three axis position reference using information from three sets of pitot tubes. There was also a side discussion regarding the computers software and they seemed to say that there were problems integrating the several redundant hardware devices because of it.

Inertial-guidance has been used for a long time for navigation. However, the gyros drift and the 'fix' needs to be corrected frequently. GPS is preferred for navigation.

I know that as the "Carrousel V" used on 747s for years, was made by GMs Delco electronics in South Milwaukee. Delco also had a very hush hush plant near my former home which made "things" for the military, which no one ever talked about. Your point about gyro drift is only true for mechanical gyros. Modern tech uses a "ring" of fiber optic cable with laser light circulating in both directions. You use an inferometer to measure changes in the phase relationship between the two signals. Presto, you have a velocity signal which can be integrated and differentiated to get position and acceleration signals, all without moving parts and bearing friction (the cause of gyro drift!), and all internal to the plane. Three axis Ring gyros are now available as integrated circuits and are so cheap now they are showing up in RC toys.

GPS is fine as long as you can lock on to a signal, flying through a thunderstorm is not the best condition for reception. Another point being that the constellation of 24 GPS satellites has perhaps about one more year of useful life left before they start to fail. That is going to be a major problem for the military if it doesn't get fixed and soon. Meanwhile we have the "O" man busily slashing budgets left and right so it's going to get interesting very soon.

Regards,
GtG

It sounds to me like either the Air France pilots or the journalists quoting them were confused. The pilots are not engineers, but the journalists are more likely to be the problem.
1. It is beyond belief that the plane would use air-speed sensors for navigation.
2. The Airbus fly-by-wire system does use 3 air-speed sensors, but they are used for redundancy/reliability (though the error message indicates that the triple-redundancy gambit failed).

(I would say that Airbus has a huge problem and will need to totally re-engineer their FCS)

You are correct about the recent switch to laser gyros. They do drift with temperature-gradient but probably less than the old spinning-gyros. It is my understanding that these aircraft use coupled inertial systems and GPS for Nav, the former for short-term and the latter for update correction.