24victor
An alternate system will need to be developed which delivers accurate airspeed without using M. Pitot's somewhat ancient approach.
Yes can be done. From basic aerodynamic theory it follows that velocity squared is inversely proportional to angle of attack. So when flying in a steady state (eg S+L) there is a one to one relationship between speed and angle of attack. So you could have software convert angle of attack into a calculated airspeed (might not be super accurate, but better than nothing) or better still, have the angle of attack displayed directly to the pilots.
If you lost all pitots, you would transition to using thrust to fly an optimum angle of attack (and hence indirectly an airspeed). Flying angles of attack instead of airspeed is routine stuff for modern fighters. For example on the F/A-18 when on final approach, the pilot does not fly a speed, but flies a constant angle of attack as displayed in the HUD.
The use of angle of attack in the event of a total loss of airspeed indications is discussed in this Boeing article:
Aero 12 - Angle of Attack
The relevent text is:
AOA backup indication following pitot or static system failures. The AOA instrument described in this article is useful as a backup for unreliable airspeed indication caused by pitot or static source blockage because the calculation of indicated AOA is not greatly affected by pitot or static pressure inputs for its calibration, and the displayed value has not been normalized.
Pitot or static system failure requires the flight crew to take several fundamental steps to resolve the problem (see "Erroneous Flight Instrument Information," Aero no. 8, Oct. 1999):
* Recognize an unusual or suspect indication.
* Keep control of the airplane with basic pitch and power skills.
* Take inventory of reliable information.
* Find or maintain favorable flying conditions.
* Get assistance from others.
* Use checklists.
Recognition of a problem will be accomplished by instrument scanning and cross-check practices or crew alerts, depending on the design of the system in the airplane. In this respect, AOA instruments can be useful as an additional cross-check.
Present procedures for unreliable airspeed call for flying the airplane by reference to pitch attitudes, and refer the pilots to reference tables showing pitch attitudes for various configurations, weights, and altitudes that will result in safe angles of attack and speeds. AOA could be useful if the relevant data is included in the pitch and power tables that already exist in the nonnormal checklist procedures. AOA would be most useful in flying the airplane in multiple failure conditions where all pitot or static sources are affected, making all airspeed indicators unreliable.
Care should be taken when flying the airplane by reference to AOA in lieu of airspeed. Control should be made by reference to pitch attitude, using AOA as a cross-check to ensure that the pitch attitude results in the desired speed or AOA. Attempting to follow AOA or speed indications too closely without stabilizing the airplane in pitch can lead to an oscillatory flight path.