"Following this incident, fuel system functionality tests performed by Bond Air Services and two other EC135 operators in Europe have revealed possible similar supply-tank fuel gauging errors on some aircraft.
The vertical black dashed line indicates a tide gauge error of zero.
The tide gauge error, i.e., the difference between the reference pressure tide gauge record and the GNSS-derived sea level, for GPS L1 versus wind speed.
The shapes of the four Van de Casteele diagrams, centered around zero tide gauge error, indicate that there are no systematic errors for the GNSS-derived sea level.
The Van de Casteele diagrams consist of simultaneous sea level height measurements on the y-axis and tide gauge error on the x-axis (tide gauge sea level minus the GNSS-derived sea level).
The tide gauge error, i.e., the difference between the reference pressure tide gauge record and the GNSS-derived sea level, was then compared to the wind speed for identical epochs (wind speed measurements are available every 10 min).
From Figure 7, it is again apparent that the phase delay sea level better resembles the tide gauge sea level, i.e., the tide gauge error is smaller, than the SNR sea level.
Sea level height is presented along the y-axis of the diagram, and the tide gauge error, i.e., the difference in sea level height between the two sea level records, is presented along the x-axis of the diagram.
It does not appear that there are significantly less SNR-derived results at higher wind speeds than at lower wind speeds, and there is no visible correlation between the tide gauge error and increasing wind speed.
