Flight instrument issue involving a Piper PA-27, VH-DTL, near Flinders Island Airport, Tasmania, on 18 April 2014

On 18 April 2014, a Piper PA-27 aircraft, registered VH-DTL, departed Moorabbin, Victoria for Flinders Island, Tasmania, under the instrument flight rules (IFR), with five passengers and the pilot on board.

During climb, the aircraft entered cloud. When the aircraft momentarily exited cloud, the pilot observed the primary artificial horizon (AH) indicated level flight, while the aircraft was in a descending turn. The primary AH then settled and accurately reflected the aircraft state.

The aircraft was in cloud throughout the cruise and severe turbulence intermittently caused both AH’s to provide unstable indications. The pilot set up the GPS to track for the runway 05 RNAV (GNSS) approach to Flinders Island, via waypoint ‘FLIWC’.  

After passing the waypoint, the GPS did not sequence to the next waypoint. He then continued to fly the approach using AvPlan. When at about 1,000 ft AGL, the aircraft encountered heavy rain, the pilot was unable sight the runway and commenced a left turn to circle back to approach the runway.

When at about 500 ft AGL, the aircraft encountered severe turbulence, which resulted in a high angle of bank and the stall warning horn activating. With both AH’s not providing accurate information, the aircraft entered cloud.

The pilot contacted ATC and reported that the aircraft was in cloud with unreliable AH’s, GPS and ADF. The controller advised the pilot to turn onto a heading of 150° and climb to 8,000 ft AMSL to fly clear of the cloud. After about 20 minutes, the pilot observed the coastline, and elected to divert to Saint Helens aerodrome, Tasmania.

This incident highlights how unreliable or unserviceable instruments can increase pilot workload, particularly when in instrument meteorological conditions (IMC).

Aviation Short Investigations Bulletin - Issue 32