Operations by older-variant Boeing 737s have been temporarily banned at Bolivia's capital El Alto airport near La Paz.

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.