Operations by older-variant Boeing 737s have been temporarily banned at Bolivia's capital El Alto airport near La Paz.
The ban takes effect immediately, on 10 October, and takes into account recommendations following the occurrence of "events", says the Bolivian civil aviation regulator DGAC. DGAC executive director Celier Arispe Rosas says the prohibition will remain in place while technical evaluation is conducted in several areas relating to operations and airworthiness. "This measure is being carried out with the sole purpose of ensuring safety of our passengers, pilots, aircraft, and all those involved in air operations at El Alto airport," he states. The DGAC adds that it will lift the suspension once risks are mitigated and an "acceptable level" of safety is achieved. It has not specified the events which led to the ban but a number of incidents and accidents at La Paz involving older 737s – those variants prior to the -600 – have occurred within the last year. These include the landing-gear collapse of an arriving Peruvian 737-500, a 1990-built aircraft, in November last year. The DGAC is probing a serious 3 August incident in which a 737-300 of Bolivian carrier BoA – a 1997 airframe – experienced "strong vibration" after the fracture of a main landing-gear shimmy damper. It has also listed a similar shimmy-damper damage incident which affected another 1997-built BoA 737-300 during landing on 7 March. Arispe Rosas stresses that the suspension only affects El Alto airport, and none of the other Bolivian airports capable of handling the 737 variants. The DGAC has not clarified whether the particular conditions at El Alto – one of the highest-elevation airports in the world, situated at an altitude of more than 4,000m – are behind this specific restriction. But South African carrier Comair, which experienced a shimmy-related 737-400 gear collapse at Johannesburg in October 2015, pointed out that the hot-and-high conditions at the airport, can require high-speed approaches in order to maintain the glideslope. Johannesburg airport has an elevation of about 1,700m. About a month later a 737-300 landing at Mexico City suffered a gear collapse. The airport is located at an altitude of more than 2,200m. Iranian operator Taban Airlines experienced a 737-400 shimmy-damper failure and landing-gear collapse during touchdown at Ardabil, after a high-speed approach, in March 2017. Ardabil is also considered to be a hot-and-high airport with an elevation of 1,300m. Boeing has previously advised that soft landings at higher speeds, particularly during approaches to high-elevation airports, can expose the landing-gear to greater risk of shimmy. Bolivia's Cochabamba international airport is also sited at high elevation, over 2,500m.

Pilots of a BMI Regional Embraer ERJ-145 were caught out by false ILS signals before the jet was involved in a serious airprox incident with a light aircraft during approach to Norrkoping airport last year. The ERJ-145, inbound from Munich, had been south-east of the airport, heading north. Its crew had requested to self-position for an ILS approach to runway 27. This involved navigating towards a point on the extended approach path, then turning left to line up and follow the ILS. But before reaching the centerline, 7nm to the north, the aircraft intercepted a false localiser signal offset from the centerline by 42° to the south. As a result the aircraft – flying at 2,100ft with its ILS approach mode armed – started turning to the left to follow the false localiser path, heading north-west, rather than west, towards the airport. At the time of the turn the light aircraft, an ATEC Zephyr 2000, had been flying west in uncontrolled airspace at 1,400ft. Swedish investigation authority SHK believes the controller did not consider the ERJ's premature turn to be unusual, because the crew had asked to self-position, while the pilots were probably distracted by the appearance of conflicting traffic on their collision-avoidance system. "The crew was not aware of the risk that a false localiser signal could be captured by the aircraft's ILS," it adds. SHK conducted a test flight in the region and determined that there was not only a false localiser signal in the region of the incident but a glideslope signal as well, which the test flight followed from 2,100ft to 1,600ft. The inquiry says that this false glideslope was also "probably followed" by the ERJ, which commenced a descent from its cleared altitude of 2,100ft. Shortly after turning onto the false localiser path, the ERJ crew made a break-off turn towards the south. But the descent profile and the break-off meant the ERJ started converging on the Zephyr's flightpath. The ERJ crew, who had visual contact with the Zephyr, executed a go-around. SHK says the ERJ had descended to 1,600ft – despite the crew's repeatedly insisting to air traffic control that they had maintained their assigned altitude – and it came within 0.85nm and 200ft of the Zephyr.

Source: FlightGlobal

Airbus A380 operators are set to be instructed to check for cracks in the trailing edge, and trailing-edge devices, of the double-deck type. The European Union Aviation Safety Agency says the directive is intended to prevent in-flight loss of parts from the trailing edge, following findings of cracks in devices on both sides. Airbus has addressed the situation with service bulletins covering inspection instructions for various locations and modifications to achieve design service targets The EASA directive lists some 30 structures for inspection, with individual service bulletins identifying the specific A380 airframes to which they apply. These structures include ribs, actuator brackets and actuator clevis assemblies at a number of spoiler locations. EASA's proposed directive mentions that several of the structures are "made from 7449". Airbus has previously experienced a wing component cracking issue which involved an aluminium alloy known as type 7449, an issue which resulted in an extensive retrofit programme and use of a more robust alloy. EASA says the new detailed inspections of the trailing edge and trailing-edge devices need to be carried out within 147 months of the A380 date of manufacture, and then at six-year intervals.

Source: FlightGlobal