The UK Air Accidents Investigation Branch (AAIB) also questions the CAA's programme for overseeing the nation's airlines, noting that the agency had highlighted weaknesses at Liverpool-based Emerald but failed to ensure that improvements were made.
Both incidents involved the crews of British Aerospace 748-2A twin turboprops, one a freighter and one carrying 51 passengers, that descended below minimum descent height and avoided terrain largely by luck.
The crews were both conducting VOR/distance measuring equipment (DME) approaches to runway 08 at Ronaldsway Airport on the Isle of Man in the northwest UK on 6 June 1998.
Although the report does not mention it, ATI understands that, by a remarkable coincidence, an AAIB official was actually in the Ronaldsway control tower at the time of the incidents.
The report says both aircraft descended "very significantly below" the specified descent profile, as a result of the handling pilots' losing situational awareness and a lack of prompt and effective intervention by the non-handling pilots.
Extensive low cloud had restricted the crews' visibility. The report says it was "entirely fortuitous" that, owing to nature of the cloud, the crew managed to see the approaching terrain.
It says: "In both cases initiation of a climb to avoid possible collision with the high ground occurred once the surface and coastline had been sighted by the pilots involved."
In both incidents, crews were conducting an approach which is unusual in that the beacon is located 4.5nm (8.3km) ahead of the runway threshold. The DME indication in the cockpit therefore counts down as the aircraft approaches the beacon, and then counts up as it passes the beacon and heads towards the runway.
The approach crosses a rocky outcrop called the Calf of Man - which rises to 420ft - as well as 580ft mast. Because of these obstacles, the approach procedure requires an aircraft to descend towards the VOR/DME, cross it at a minimum height of 1,400ft, then continue the descent but remain above 800ft until 2.5nm (4.6km) from the threshold. Only at this point can the aircraft safely descend towards the runway.
During the freighter's descent to the VOR/DME at about 05:15, its crew - which had not made the instrument approach to Ronaldsway before - incorrectly set the flaps to 27.5° for landing, rather than 22.5° for approach.
Handling difficulties from the subsequent drag distracted the pilot, leaving the aircraft's rapid descent unchecked until it had dropped far below the 1,400ft minimum, to around 630ft, just half a mile from the Calf of Man rock face. The first officer also failed to notice the loss of altitude because he was occupied with landing checks and radio calls.
According to the approach controller, the aircraft disappeared momentarily from primary and secondary radar during the low-altitude excursion.
Once the pilot realised the danger, he executed a go-around, and the aircraft landed safely. Despite a request that the crew contact the radar controller by telephone, the crew departed with another aircraft without making such a call.
A second Emerald 748 crew attempted the same procedure, just over two hours later. The aircraft was flying too fast, and the pilot was already trying to correct a heading overshoot when he initiated a rapid descent towards the beacon. The pilot said later that he'd believed the aircraft to be much closer to the runway than in reality, partly because of the unusual beacon location and partly because he had misread the cockpit DME display.
This led to what the AAIB report describes as a "rushed approach", the high aircraft speed leaving little time for the crew to configure the aircraft, "creating the conditions where errors are likely to occur".
As a result, the crew failed to realise that the aircraft was sinking far below the descent profile. By the time recovery was initiated, the aircraft was flying at just 500ft.
In both incidents, the AAIB raised concerns over communication between the crew members. The freighter crew comprised a 41 year-old captain with 8,667 total hours - including 6,739 on type - and a first officer aged 27 with 1,060hr, including 100hr on type. It was the first time they had flown together.
The freighter's first officer could not recollect being briefed for the approach, despite the pilot's claim that such a briefing took place. The first officer, according to the report, said he was "reluctant" to question the commander because he had only been with Emerald a short time.
On board the passenger aircraft involved in the second incident was a 64 year-old captain with 16,000 total hours, including 800hr on type, and a 41 year-old first officer with 1,527hr, of which 563 were on type.
During this incident the report says: "The first officer noted that the aircraft had descended below the required profile and recalled highlighting this to the commander, but the commander did not respond.
"The first officer indicated that he then looked across the flight-deck to see if the commander was incapacitated, but concluded that he was just concentrating on flying the aircraft. The commander did not recall any voice prompt having been made."
In their report, the investigators express several concerns: crews' not being issued with "any volumes of the operations manual"; no aircraft technical manual with detailed systems descriptions being available to crews; poor format of the operations manual; poor crew resource management which had already resulted in altitude deviations; and the "diverse nature and ergonomic quality of the instrumentation and radio equipment fitted to each of the aircraft in the fleet".
They are particularly critical over the airline's apparent favoured practice on non-precision approaches. Re-drawn diagrams showing final-approach technique, they say, "gave an indication that the preference was to conduct a rapid descent to Minimum Descent Height and then to level off".
The report adds: "This is contrary to best published advice, widely circulated in the industry, relating to the conduct of this type of approach, and has been cited as a causal factor into some controlled-flight into terrain accidents in the past."
The AAIB says that the CAA's AOC Holder Oversight Programme had already identified deficiencies in the crew resource management aspects of Emerald's operations. But it concludes: "The programme was ineffective in producing sufficient, timely improvement. If it had been successful, these incidents could have been prevented."
Among its nine safety recommendations, the AAIB says the CAA should review the effectiveness of the programme, to determine whether methods are needed to ensure safety deficiencies are corrected promptly. The CAA says such a review is underway, to be completed by the end of April.
Neither aircraft's altimeters and airspeed indicators had adjustable cursors which could have been set to indicate minimum safe heights and speed to the crew. But the CAA has rejected a recommendation to require such cursors on primary instruments, stating that they "would not have affected the outcome" of the Emerald incidents.
The AAIB says that Emerald Airways should modernise its fleet to provide greater standardisation and more ergonomic cockpit design.
It further suggests improvements to the Racal Aeronautical Services approach charts, to give crews better insight into the terrain and obstacles, and recommends that an instrument landing system be installed at Ronaldsway Airport.
The AAIB continues to work on its investigation into the loss of another Emerald BAe 748 carrying passengers at London Stansted Airport in which the captain successfully abandoned take-off after becoming airborne and identifying an engine fire. UK pilots are curious to see what view the AAIB takes of the pilot's action in abandoning take-off after V1 decision speed given that there is some question as to whether it would have survived a circuit to land with the intense fire that had broken out.
Source: Flight International
