Mountains

Findings as to Causes and Contributing Factors:
1. For reasons not determined, the pilot did not adhere to the procedures depicted for the LOC DME-B approach to runway 16 at Penticton. As a result, the aircraft did not remain within the confines of protected airspace, was below the minimum safe altitude for the procedure turn, and struck the tower.
Findings as to Risk:
1. The approach was flown in weather conditions that virtually precluded the pilot from completing a landing.
Other Findings:
1. The pilot's flight medical certificate had expired one month prior to the accident, and no information could be found that he had submitted to an FAA medical during that time.

The pilot-in-command's failure to maintain sufficient altitude while maneuvering to land, which resulted in a collision with terrain. Factors in the accident were the dark night, mountainous terrain, snow showers, clouds, and the pilot's decision to cancel his IFR clearance.

The flight crew's decision to continue VFR flight into instrument meteorological conditions. Factors associated with the accident are high winds, turbulence, and low ceilings.

On vacating FL140, the aircraft's climb rate was so erratic at 140 KIAS that it seems likely that by then, the aircraft had already gathered sufficient ice to seriously affect its performance. If all the
turbocharger inlets had become partially blocked, then manually selecting both engines to alternate air induction should have introduced warmer air into the turbochargers and restored power. The description of engine operation in the Superstar manual states:
'If manifold pressure continues to decrease after opening the manual alternate air, it is an indication that turbocharger inlets are still restricted and the engine may become normally aspirated through the automatic alternate air door located below the induction air filter'.
Normal aspiration reduces the manifold pressure to ambient or less and at FL140 the ambient pressure is about 17.6 inches which is less than half the climb rated manifold pressure. That might explain the inability to climb above FL 160 but it would also have deprived the pilot of pressurisation. There was no change in his voice consistent with donning an oxygen mask so he may not have lost pressurisation completely. Nevertheless, since he lost control at around FL160 and 110 KIAS, and because the aircraft initially turned to the right, a combination of airframe icing and asymmetric power loss seem the most likely explanation for the sustained loss of control. The split in the EDP diaphragm which almost certainly occurred during this flight may have contributed to an asymmetric power problem. Alternatively, the pilot might have become mildly hypoxic and decided to begin an emergency descent. If so, he did not declare an emergency at the time he started to descend, although he did utter the word "SCOTTISH" after control was lost, so he was conscious even if his mental abilities had been impaired by hypoxia. On balance, the tone of his voice and his initial failure to respond to ATC messages suggested that the descent was begun through loss of control rather than a deliberate act followed by loss of control. At the time of the accident the aircraft had been flying below the freezing level (8,000 feet) for about five minutes and much of the airframe and induction system ice may have melted. The would-be rescuers would have taken at least five minutes to reach the crash site and so the fact that none of them reported seeing or treading on any ice was not surprising. Witness and propeller evidence indicated that power had been restored on at least one engine but there seemed to be insufficient power to climb out of Glen Lyon. The aircraft was out of control when it crashed at low speed from a sharp turning manoeuvre. Before this manoeuvre the pilot may have had partial control, albeit with a power problem which prevented him from climbing, and he finally lost control totally when he attempted to turn around within the confines of the Glen. He had no choice but to attempt the turn since, had he not turned, he would have flown into the side of the hill above the crash site.

It was determined that the loss of control was the consequence of a double engine failure in flight due to a fuel exhaustion. At the time of the accident, all tanks were empty and the crew failed to calculate properly the fuel consumption, and the fuel quantity for the last leg from Pereira to Bogotá was insufficient. The aircraft was completing a series of flight since Octobre 26.

Total blockage of the instrument static system due to ice.

Controlled flight into terrain after the crew continued the approach in poor weather conditions below the minimum prescribed altitude and while deviated from the approach path. The following contributing factors were identified:
- Navigational error on part of the crew during the final stage of the approach,
- ATC based at Batumi Airport failed to determine the exact position of the aircraft and failed to warn the crew accordingly,
- The crew 's decision to continue the approach in such conditions rather than to divert to a suitable alternate airport,
- Erroneous data transmitted by ground navigational aids in the Batumi area.

Controlled flight into terrain after the crew descended too low under VFR mode in IMC conditions. The following contributing factors were identified:
- The crew canceled the IFR flight plan for an approach under VFR mode despite weather conditions were marginal and the visibility was insufficient,
- The crew failed to follow the approach checklist,
- The crew failed to complete an approach briefing,
- The crew did not proceed to any callouts on approach,
- The second pilot was procedurally not involved in cockpit work processes and decision-making,
- On approach, the crew referred to the Flight Management System (FMS type III series) which was initially dedicated to flight inspection purposes only,
- Measurement was performed by the flight engineer.

The decision of the pilot to continue the approach under VFR mode in IMC conditions. The limited visibility caused by low clouds was considered as a contributing factor. At the time of the accident, the hilly terrain was shrouded in clouds. For unknown reasons, the approach speed was relatively low (110 knots).