BALANCE.
17th Jul 2012, 20:49
After reading the the final report on AF447, where unreliable airspeeds (among a myriad of other problems) contributed to the accident, I was wondering whether the Ram Air Turbine could be used to determine airspeed (roughly or accurately) as an emergency backup?
RAT uses airflow to power critical systems on an ACFT. The kW generated would increase roughly with the square of the airspeed (or would it be linearly?). If the electrical power generated is known (which the flight computers I assume WOULD have a value for), and also possibly the altitude, wouldn't it then be a (relatively) simple step to calculate curves for airspeed with respect to power? I am going by some simple equations from wind air turbine power generation, which would apply to a RAT.
A flight crew could use a simple (perhaps memory item) relationship between power from the RAT and airspeed to estimate airspeed when other instruments are proving unreliable/confusing. Could the crew of AF447 have used this idea (perhaps if it were in the FCOM/AFM for non-normal conditions, and/or the QRH) to make a decision?
RAT uses airflow to power critical systems on an ACFT. The kW generated would increase roughly with the square of the airspeed (or would it be linearly?). If the electrical power generated is known (which the flight computers I assume WOULD have a value for), and also possibly the altitude, wouldn't it then be a (relatively) simple step to calculate curves for airspeed with respect to power? I am going by some simple equations from wind air turbine power generation, which would apply to a RAT.
A flight crew could use a simple (perhaps memory item) relationship between power from the RAT and airspeed to estimate airspeed when other instruments are proving unreliable/confusing. Could the crew of AF447 have used this idea (perhaps if it were in the FCOM/AFM for non-normal conditions, and/or the QRH) to make a decision?