Description

On 13 July 2009, a Gulfstream IV being operated by Indian operator Asia Aviation on a private flight from Kerry to Luton with one passenger on board in day Instrument Meteorological Conditions (IMC) suffered a left main windshield failure shortly after take off and elected to make a return to land. Having received an ATC clearance to do so, it then failed to follow it and began a steep descent approximately 6 nm to the south of the airport towards high ground. When ATC became aware of this, an urgent instruction to climb was given and eventually the return was completed.

Investigation

An Investigation was carried out by the Irish AAIU. The track followed by the aircraft was re-created from the available data and the illustration below taken from the official report was created. Following the request for a return as a result of the windshield failure it was noted that the clearance given to route to the overhead and then establish outbound on the ILS for an ILS DME approach to RWY 26 was acknowledged but not followed.

It was established that, as the aircraft initially began to track as cleared, the aircraft navigation equipment had picked up a false ILS LLZ signal which produced an indication of LLZ capture, albeit with concurrent oscillations of both the LLZ and ILS GS command bars. It was noted that at the location where the false LLZ signal was received, the aircraft had been outside the LLZ specific coverage sector for the ILS at Kerry. It was established that the inexperienced First Officer had been unable to properly programme the FMS and had set it up for an approach to RWY 26 at the originally intended destination rather than Kerry, to which the return was being made.

A steep descent had then been commenced in landing configuration on a track roughly parallel to the Kerry ILS LLZ but approximately six miles to the south of it. The Investigation determined that “this track took the aircraft directly towards high ground rising to in excess of 3,000 feet and it descended in cloud to a lowest height of 702 ft above the ground”. This inappropriate descent was attributed to “non-compliance with laid-down procedures and instructions, as well as non-adherence to CRM principles” and it was considered that a potential controlled flight into terrain was averted by the intervention of a controller in the ACC who was not working the aircraft and the simultaneous warning provided by the aircraft Terrain Avoidance and Warning System (TAWS).

It was noted that, even after the recovery from the near CFIT, the aircraft track had continued to evidence further navigational difficulties and that for much of the flight, the aircraft had been operated below the applicable Minimum Sector Altitude while not under radar control.

It was also noted that:

• The failure of the flight crew to comply with instructions and provide accurate information seriously compromised the Kerry TWR Controller’s situational awareness.

• Notwithstanding the fact that the Kerry TWR Controller did not have access to radar data, he did not challenge the non-compliance of the crew with his instructions because he considered that such an intervention would have added to crew confusion and increased the pressures under which they were operating.

• There was inadequate oversight of the operation of the aircraft by the Operator.”

• The crew had not tripped the Cockpit Voice Recorder (CVR) circuit breaker after the flight, although this was a requirement of the State of the Operator following an accident or incident.

The facts relating to the airworthiness aspects of the flight were determined as follows:

• The failure of the left hand main windshield after take-off was caused by electrical arcing. This arcing generated an excessive amount of heat that caused damage to the inner laminated surface of the outboard glass ply. The damage penetrated the surface compression and entered the centre tension layer of the chemically strengthened glass, causing spontaneous fracture. The effect on forward visibility for the aircraft commander was not significant enough to present any actual difficulty for the visual transition to land.

• The No. 1 engine was found to have sustained serious foreign object damage to the fan blades, the LP compressor and the HP compressor. However, the first indication of an engine anomaly was a stall event shortly before the engine was shut down on the ramp following completion of the flight. The foreign object involved was a hard-bodied object, probably of round shape, approximately 25 mm in diameter and made of mild steel. Contrary to flight crew comments about signs of engine malfunction when airborne shortly after the windshield failure, there was no connection between the latter and the engine damage. It was noted that even though they were aware of foreign object damage to the fan blades the crew subsequently performed a series of inappropriate engine starts, accelerations and decelerations. It was considered probable that the engine damage was exacerbated by these operations, culminating in a serious stall event on the final high power run.

The Investigation concluded that the Probable Cause of the event was that:

“The crew suffered a serious loss of navigational and situational awareness while attempting to return to EIKY following a windshield fracture encountered shortly after take-off.”

Five Contributory Factors were identified:

• The crew made a number of rushed and inappropriate decisions during the flight, thus displaying poor crew resource management.

• The First Officer’s lack of recent flying hours is likely to have contributed to his loss of navigational and situational awareness.

• A “false localiser” signal was received due to Approach mode being armed while the aircraft was outside the specific localiser coverage sector.

• The Captain commenced a descent without having a valid ILS signal and without cross-checking other available navigation aids.

• The situational awareness of the controller in Kerry Tower was compromised by erroneous position reports from the crew and non-compliance with his instructions, as well as a lack of direct radar information.

One Safety Recommendation was made:

• That the licensee of Kerry Airport, in conjunction with the Irish Aviation Authority, should review the provision of radar information to support the air traffic control service provided by Kerry ATS unit. (IRLD2010016)

The Final Report of the Investigation was published on 30 August 2010 and may be seen in full at SKYbrary bookshelf: AAIU Synoptic Report No: 2010-012

Further Reading

• Controlled Flight Into Terrain (CFIT)
• Cross-checking Process
• Terrain Awareness
• Response to a "PULL UP" Warning
• Pilot judgment and expertise (OGHFA BN)
• Crew Resource Management (OGHFA BN)
• Situational Awareness