Aerospace and Electronic Systems Magazine April 2017 - 13
Imai et al.
tifies a normal condition. For underweight
conditions, we set a constraint that will
identify 10% discrepancy in weight. Since
the 10% weight difference leads to a 4.69
knots difference in airspeed from Equation
(8) (computed by averaging over w = 13,000
∼ 22,000 kg at 23,000 feet), 4.69 is used as
the boundary for the underweight conditions. In summary, the error signatures vector is shown in Table 4.
Error Signatures Vector for the Tuninter 1153 Flight
−2 < k < 2
4.69 < k
Weight Check PILOTS Program
A PILOTS program called WeightCheck
implementing the error signatures vector of
Table 4 is presented in Figure 12. WeightCheck detects an underweight condition
by comparing the monitored and estimated
airspeed computed from the weight and altitude. Once WeightCheck detects the underweight condition by the error signature S1, it
estimates the corrected weight, which can be
obtained by solving Equation (9) for w.
Flight data: The airspeed, monitored
fuel weight, and altitude of the aircraft are
collected from Attachment H of the accident report . Since the total weight of
the aircraft is needed for the model used in
WeightCheck, the fuel weight comparison
to the zero fuel weight of the aircraft is computed and added to the model. As a result,
before the departure, the monitored "fictitious" weight of the aircraft is 19,420 kg,
whereas the actual weight is 17,270 kg.
Experimental settings: We run
the WeightCheck PILOTS program in
Figure 12 for 1,500 seconds, from 2,000 to
3,500 seconds after departure including the
first (2,170-2,370 seconds) and the second
cruise phases (2,960-3,450 seconds), to see
how the error signatures vector works for
these two cruise phases. Note that we evaluate only the second cruise phase since the error signatures vector is adjusted by the first
Results: With ω = 1 and τ = 0.8, Figure 13
presents the results. As shown in Figure 13b,
the PILOTS program correctly detects the
underweight condition for the first cruise
phase whereas it detects the underweight
condition well before the second cruise phase
starts. The fault is detected early because the
error goes beyond 4.69 (the boundary for the
underweight condition) around 2,770 secAPRIL 2017
PILOTS program to detect and correct for weight data faults.
Aircraft weights and detected modes for the TU1153 flight.
IEEE A&E SYSTEMS MAGAZINE