UK investigators believe an increasing tailwind resulted in an Emerald Airlines ATR 72-600’s losing airspeed as it crossed a Liverpool runway threshold in heavy rain, causing the turboprop to make a hard landing.

Analysis found the ATR touched down on runway 09 with an impact of 2.8g and the crew executed a go-around. It subsequently landed safely with no injuries among the 71 occupants.

Although the crew had discussed the captain’s taking over the landing if weather conditions were gusty, Liverpool approach control had indicated a southeast wind at 7kt, so the first officer – who had 172h on ATRs – remained as the flying pilot.

The ATR was stabilised on the approach but the crew observed that, as the aircraft was cleared to land, the surface wind had switched to the southwest – giving a tailwind component.

According to the UK Air Accidents Investigation Branch, the captain advised the first officer to monitor power should the wind change.

On short final, it says, the rain became heavy and visibility rapidly deteriorated as the aircraft overflew the runway threshold.

“The [first officer] recalled the flightdeck ‘going dark, like someone had pulled the curtains’,” it adds.

Emerald ATR 72-c-Emerald Airlines

Source: Emerald Airlines

Investigators found the ATR, similar to this one, encountered heavy rain just before touchdown

Although the aircraft’s airspeed was 109kt when the flare was initiated at 30ft, the inquiry believes the tailwind component had increased as the aircraft crossed the threshold, causing the airspeed to decline.

The rate of descent, as a result, did not reduce during the flare. But the poor visibility, says the inquiry, “made it difficult” for the crew to notice.

Flight-data recorder information shows the airspeed had fallen to 95kt and the descent rate was around 670ft/min when the aircraft contacted the runway. The ATR started climbing away about 5s after the hard landing.

The inquiry points out that the flight-management system uses a smoothing algorithm which avoids large instantaneous wind changes being displayed to the pilots, and that this means winds shown to the crew might lag the real-time conditions.

Inspection of the aircraft (EI-HDK) after the incident, on 14 August last year, did not reveal any structural damage, but the main landing-gear was nevertheless replaced. The aircraft returned to service two weeks later on 30 August.