Honeywell says it expects to have a fix in place by the end of the third quarter that will remove temporary restrictions placed on Primus Apex-equipped Pilatus PC-12 NG aircraft earlier this month.
The European Aviation Safety Agency on 3 April issued an emergency airworthiness directive against the integrated avionics suite, alerting operators to the possibility that both primary flight displays could indicate an erroneous roll attitude offset of up to 10° in the same direction when the Apex-equipped aircraft are taxied on to the runway in an accelerated turn, with take-off immediately following.
Honeywell says the problem is linked to a "software issue" in Apex's air data, attitude and heading reference system that "affects attitude indication on the primary flight displays of the PC-12 NG."
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As an interim fix, the emergency AD requires PC-12 NG operators to hold in place for 60s before lining up on the runway for take-off, followed by a low-acceleration turn on to the runway and waiting 15s once aligned with the runway centreline before departure.
Further, the AD requires pilots to follow their electronic standby instrument system (ESIS), located to the left of the pilot's primary flight display, if there is a discrepancy between the bank angle on the display and the ESIS. EASA notes that the flight director and autopilot navigation and heading modes are unaffected by the issue.
Pilatus began delivering the Apex suite in the PC-12 as part of the NG upgrade in May 2008.
Source: Flight International
