The Safety Board determined that the left aileron surface position data recorded by
the accident airplane’s FDR were invalid even though the accident airplane had been
modified on August 7, 2001, with the position sensors and associated hardware required
by STC No. ST01310NY. Executive Airlines stated that the first and last FDR parameter
readout since the installation of the sensors occurred on January 3, 2003, about 1 year and
5 months after the installation and 1 year and 4 months before the accident. Executive
Airlines stated that it had replaced 47 aileron surface position sensors in the last 3.5 years.
However, the company indicated that, because the sensors are not tracked, the times from
installation to failure could not be determined.