In an emergency similar to AF447; in the case of loss of airspeed indication at high altitude due to failure of all pitot tubes, what is the QRH guidance to maintain control of the B777?
Does the Non-Normal tab of the center/lower screen in the Boeing 777 cockpit provide guidance on the needed steps for pilots to take in this scenario?
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In the event of loss of airspeed indication at high altitude as a result of failure of pitot tubes similar to Air France Flight 447, pilots are trained to immediately return the airplane to the target attitude and thrust settings.
They have to consult the Performance In-flight section of the QRH (Quick Reference Handbook) in order to get the correct attitude, thrust settings for the actual airplane’s weight and altitude.
For example, on a Boeing 777, if the plane was at 40,000 feet, flying level at Mach 0.84 (84 % of speed of sound) and weighting 200 tons, it has to maintain a target body attitude of 2.3 degrees up and a power setting on its Rolls Royce engine of 1.252 EPR (Engine Power Ratio)
I believe the recent changes in the Boeing procedures that provide guidance regarding the monitoring of airspeed indications on the center/lower screen come with ‘ IAS DISAGREE and ALT DISAGREE’ messages to make recognition of any anomalies easier.
Today, on the Airbus planes, as a result of AF447 crash, they have come out with a more user- friendly tool (instrument), to save the day. It is known as the BUSS or Back Up Speed Scale.
The pilots need not have to memorise or refer to the figures above to fly the plane when it loses its airspeed. They just fly the indicator onto the green scale. See the image below.
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