Flight from San Francisco to Hong Kong has to abort landing and divert to Taipei because of turbulence during Typhoon Nida
At the time, the Observatory had issued a No 8 typhoon warning
A flight into Hong Kong Airport had to abort its landing on Tuesday and divert to Taipei because of turbulence as Typhoon Nida battered the city.
Singapore Airlines flight SQ1 from San Francisco failed to get wheels down onto the tarmac at 10am. The turbulence was blamed on windshear, a problem familiar to pilots flying in and out of Hong Kong.
As heard on LiveATC.net, a website that monitors air traffic control broadcasts worldwide, one of the pilots on SQ1 told controllers the plane was affected by windshear and needed another landing attempt. The pilot soon decided to abort a second landing, and diverted to Taipei.
The Hong Kong Observatory’s aerodrome forecast for 10am showed gusts between 40 and 50 knots.
Hong Kong is renowned for windshear, which occurs as the gaps in the peaks on Lantau Island disturb the airflow during strong winds. This affects take-offs and landings by causing a temporarily loss of handling.
No other flights attempted to land at the time
Commercial airline pilot Jeremy Tam Man-ho said 40 to 50 knot gusts were well within limitations of what a large-bodied aircraft – a Boeing 777-300ER in this case – could sustain during landings.
He said two tries before a diversion was acceptable given that the plane had enough fuel and there was no imminent danger. “Given how bad Hong Kong’s weather was at the time, they would have probably brought enough fuel for such an emergency,” he said. “Pilots do not usually take more than two attempts and anything more would be questionable.”
Pilots were also able to judge windshear based on changes in vertical speed and pitch, or, if the aircraft’s own windshear warning system is triggered. Under such mechanical turbulence, “go-arounds” were standard procedure, he said.
Given that most neighbouring airports are usually also affected by the same typhoon, diversions due bad weather usually go to Taipei or Manila.
A Singapore Airlines spokesman confirmed to the Post that the flight was diverted due to strong winds from Typhoon Nida. The flight arrived in the Taipei at 11.20am and departed for Hong Kong again at 2pm. Passengers travelling to Singapore on the flight were transferred to another flight.
“Passengers were served refreshments upon their arrival in Taipei. Arrangements will be made to re-book affected passengers on alternative flights upon their arrival in Hong Kong,” the spokesman said.
Hong Kong’s Civil Aviation Department said the incident happened between 9am and 10am on Tuesday. Surface wind at the airport was 200 degrees at 25 to 30 knots with gusts at 40 to 50 knots. Significant windshear and severe turbulence was forecast on the flights approach path but the pilot had insisted on making the landing.
“Despite repeated informing of the crosswind condition at HKIA and constant update on the wind and windshear information by ATC, the pilot [had opted] to make an approach,” a spokeswoman said.
“The decision to carry out any flight manoeuvre for instance departure or approach rests with the pilots as they are ultimately responsible for the safety of the aircraft.” She said missed approaches in bad weather were common at the airport.
The Airport Authority said about 500 flights to and from Hong Kong between 6am and midnight were expected to be rescheduled on Tuesday.
Hong Kong’s biggest airline Cathay Pacific and its sister company Dragonair announced they would resume flights from 2pm. The move followed the cancellation of dozens of flights between the two airlines from 10pm on Monday night until Tuesday afternoon.
Hong Kong Airlines and HK Express also suspended flights until Tuesday afternoon.
Additional reporting by Ernest Kao
Condensed transcript of Singapore Airlines SQ1
SQ1: SQ1 [inaudible]...we have windshear on runway track.
ATC: Singapore 1 continue on present heading, climb to 6,000 feet. What is your intention afterwards?
SQ1: Windshear recovery.
ATC: Continue present heading 6,000 feet.
SQ1: 6,000 feet continue runway heading no. 1.
SQ1: Singapore 1, unable 6,000 feet, request 7,000.
ATC: Singapore 1, climb to 7,000, and when you are ready, you can turn left on tango delta, on heading 170.
SQ1: Climbing 7,000, Singapore 1.
ATC: Singapore 1, do you require higher or is that enough for you?
SQ1: Singapore 1, we do require higher and our intent is to divert to Taipei.
ATC: Singapore, roger, Taipei. Just standby, you can turn left to heading 090.