I work in flight data analytics, we are trying to find a robust way to detect liftoff
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I work in flight data analytics, we are trying to find a robust way to detect liftoff
I work for a flight data analytics company, we are trying to find a robust way to detect the exact point of liftoff of an aircraft using data available from a flight recorderCurrently, we use a mix of gear, pitch, longitudinal / normal acceleration, and altitude indications.
Suggestions, brainstorming, questions... All is welcome!
Suggestions, brainstorming, questions... All is welcome!
Not an FDR input, but would be monitored by an anti-lock system: at the exact point of liftoff the tires will instantaneously begin to slow in rotation at a linear rate. You will have a separate lift-off for each independent axle. If there is a bounce the speed will suddenly increase to flight speed. Even if the data rate for the rotation monitoring isn't high, one can interpolate both the on-ground speed and the airborne speed and see where they intersect.
WOW may indicate before the last contact with the ground has occurred and there won't be a way to determine exactly when except that it happened between two recorded times. WOW, OTOH, is almost certainly recorded in any aircraft that depends on WOW for automation.
WOW may indicate before the last contact with the ground has occurred and there won't be a way to determine exactly when except that it happened between two recorded times. WOW, OTOH, is almost certainly recorded in any aircraft that depends on WOW for automation.
Main gear tyre pressures - once all have gone to a minimum, the aircraft must have no weight on any tyre and therefore be airborne ?
But these data are not universally measured on all aircraft, and I don't know if they are recorded on the flight recorder ?
But these data are not universally measured on all aircraft, and I don't know if they are recorded on the flight recorder ?
Aren't the WOW sensors linked to thrust reverser and ground spoiler activation too? Surely there's a discrete input to the EEC (FADEC) and flight control system logic.
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Tyre pressures are not recorded by any FDR that i have come across besides the 787 and 350 but they record things such as wheel RPM which is more useful in the context of my post
In that case; what about Rad Alt; corrected for pitch attitude?
The measured Rad Alt will reduce to a minimum as the aircraft is pitched up, (Rad Alt antennas usually fitted underneath the rear fuselage), then after a pause, the Rad Alt will increase as the aircraft lifts up.
I am assuming that Rad Alt will be accurate enough when the antennas are within a meter or so from the ground, but only a positive or negative trend will need to be registered.
And there will need to be constant reference to the aircraft pitch angle, used to correct the measured radio altitude height; since pitch angle will change the measured reading.
The measured Rad Alt will reduce to a minimum as the aircraft is pitched up, (Rad Alt antennas usually fitted underneath the rear fuselage), then after a pause, the Rad Alt will increase as the aircraft lifts up.
I am assuming that Rad Alt will be accurate enough when the antennas are within a meter or so from the ground, but only a positive or negative trend will need to be registered.
And there will need to be constant reference to the aircraft pitch angle, used to correct the measured radio altitude height; since pitch angle will change the measured reading.
