-I was reading about Air France fligh 447 and how the airspeed 'pitot' sensors may have been defective or malfunctioning, causing the aircraft to stall. I have traveled often on transatlantic flights and I have often seen GPS screens showing tail speed, altitude, etc, even in the main cabin for the passengers to see. Could pilots use GPS to measure airspeed as a back-up system, in case the airspeed sensors on board may fail?The GPS system on most aircraft in use today is not displayed to the pilots. There installed to aid the navigation system and not to supply pilots with flight parameters. The FMS system and optionally a GLS system uses the inputs from GPS.
As mentioned earlier, you would not receive the IAS from any GPS system. When it comes to maintaining your heading it鈥檚 not that simple if you鈥檙e flying in the middle of the night and your instruments gone bonkers. BUT, as long as the pilots have standby horizon they shod trust this and be able to level the aircraft. I have not read everything written about the AF447 accident and I鈥檓 not going to until the finished, official report is done.
Actually, no. At least not in most newer Boeing or Airbus aircraft.
The cockpit windows have a thin laminate of gold threads that is used to heat and or defog the window. This interferes with the GPS signal. I know I tried this when the first usuable GPSs became available and it didn't work in the cockpit, although it would work if the remote antenna was attached to a cabin window. Not practical for flying obviously.
In any case the issue of the availability of GPS data isn't relevant in this case since the aircraft's own GPS data was still valid, available and displayed right there on the PFD/ND. That information doesn't help much until you are below around 10,000ft. when it is a more accurate reflection of indicated airspeed.
The real problem is the training the pilots didn't get enough of.
Absolutely they could. But based just on what we know of flight 447, that would have made no difference. The autopilot still would have disconnected due to the disagreement and whatever prevented them from recovering from the stall (which we don't know yet) still would have done so.
There have been accidents, however, that this could have averted. For example, there was one case (AeroPeru flight 603) where airspeed and altitude readings were unreliable and an aircraft gradually descended into the ocean as the flight crew believed they were holding altitude. GPS altitude would have saved them. It was an aircraft accident (Koreal Air Lines flight 007) that prompted President Reagan to make GPS available for commercial use in the first place.
In order to need GPS speed to maintain attitude though, you'd have to lose both airspeed and attitude indicators. That's a pretty improbable condition since these are provided by completely different systems and the attitude indicator is independent of anything but a power source.
As mentioned by Skyking - GPS tells you ground speed -
An airplane stall speed is function of IAS (airspeed) -
Two different animals -
If your two airspeed sensors are "dead" - it is simple -
(1) keep nose up attitude at 2 to 3潞 above horizon, wings level -
(s) Maintain cruise power you had before airspeed malfunction -
Why is it necessary to complicate everything...? -
I bet a good private pilot can do the above...
If the pitot sensors did, in fact fail, they didn't cause the aircraft to stall. The pilots failed to notice the malfunction and allowed the aircraft to get into a condition from which they could not recover. It's pilot error. Not all aircraft are equipped with IFR certified GPS.
GPS only measures ground speed, not airspeed. It is therefore useless as a replacement for a failing airspeed sensor system, because airspeed can be dramatically different from ground speed.
No. GPS measures ground speed and the pilots would need to see Indicated Air Speed. The two can be very different, especially at high altitude.
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