SINGAPORE - A Singapore Airlines (SIA) aircraft departing Nepal for Singapore in May 2022 was damaged when the bottom of its tail hit the runway during take-off, an investigation found.

The tail strike was caused by the pilot over-tilting the aircraft, and possibly a tailwind, the Transport Ministry’s Transport Safety Investigation Bureau (TSIB) concluded in its May 2 final report on the incident.

The scheduled flight on a Boeing 737-800 took off from Kathmandu at 5.13pm Singapore time on May 6, 2022, during which a cabin attendant at the rear of the plane heard a thud and a scraping sound just before the plane lifted off.

The pilot monitoring the flight also reported that he “felt a light thud” during take-off but noted that there were no anomalies in the engine readings. But he informed the pilot flying shortly after take-off of his suspicions that the tail might have hit the runway.

As the departure out of Kathmandu required the aircraft to fly over high terrain, the pilot continued to fly the plane to above the minimum safe altitude of 14,400 ft before descending and diverting it to land in Kolkata, India. 

The monitoring pilot also deployed the passenger oxygen masks as a precautionary measure.

No one on board the flight, which was carrying eight crew members and 165 passengers, was injured.

Inspections in Kolkata confirmed the skid shoe of the aircraft’s tail skid assembly had touched the runway, but that there was no damage to its rear fuselage. The tail skid is an attachment at the base of the tail that absorbs contact.

In its report, TSIB said the flight crew “could have considered” checking for a tail strike after reaching 10,500 ft – when the plane would have established its flight path and configuration – while still climbing to its minimum safe altitude.

It noted that the flight crew training manual stipulates the checklist of actions when a tail strike is confirmed or suspected “should be carried out without delay”.

However, it acknowledged that a tail strike out of the Kathmandu airport, which is at an elevation of 4,400 ft, would represent “a very challenging situation due to the uniqueness of the operation environment”.

One of the actions for a suspected tail strike would be to depressurise the aircraft to avoid any potential damage to the plane structure, and at the height the plane was flying, this might trigger oxygen masks to be automatically deployed. This could cause “inconvenience” to passengers, the report said, but noted that it would be acceptable given the unknown risk of damage.

Investigations also showed the aircraft lacked a tail strike warning indication system, which could have helped the flight crew better decide on whether to check and confirm a tail strike.

TSIB recommended the aircraft manufacturer, Boeing, consider making a tail strike warning indication a standard feature on the flight deck.

The report also noted that the monitoring pilot had deployed the passenger oxygen masks without informing the pilot flying.

“Oxygen masks deployment, an irreversible action, is a significant event in flight operation,” the report said.

“Keeping each other in the cockpit informed of the flight operational situation is a common safety strategy practised by flight crew and is important for ensuring that flight crew members have the same operational picture,” said TSIB, adding that this will allow them to better manage situations.

TSIB also recommended SIA re-emphasise proper aircraft control techniques during take-off to prevent tail strikes and provide targeted advice and training for airports at high elevations surrounded by high terrain, such as the one in Kathmandu.

In the report, TSIB said that SIA has incorporated the lessons learnt from the incident by holding discussions during recurrent and initial crew training.

When contacted, an SIA spokesman said: “We have taken note of the recommendations in the final report, and would like to share that our approved initial and recurrent training programmes ensure that crew are trained to handle situations that may occur during the course of their operational duties.

“The safety of our customers and crew is our utmost priority.”