Friday, February 6, 2015

TransAsia Flight 235 Inexplicably with No Engines

TransAsia Airways Flight 235 was a scheduled Taiwanese domestic flight from Taipei Songhan Airport to the Kinmen Islands.

The aircraft, registration B-228516, was a twin-engine turboprop made for regional airliners, the ATR 72. It can seat up to 74 passengers and is operated by a two-pilot crew. B-22816 had two Pratt & Whitney Canada PW127M engines and was less than a year old. There were five crew and 53 passengers on board. The flight crew consisted of three extremely experienced pilots. The Captain (Pilot Flying) had 4,914 flight hours and the First Officer had 6,922 flight hours. A flight instructor who was in the jumpseat had over 16,000 flight hours.

The aircraft took off from Taipei and climbed through 1,000 feet. Two minutes after take-off, the flight crew declared an emergency.

Control Tower [inaudible] … wind 100 degrees, 9.9 knots. Clear to take off.
TransAsia GE235 Clear to take off, runway 10, TransAsia 235
TransAsia GE235 Mayday! Mayday! Engine flameout
Control tower TransAsia 235, please try again. Contact Taipei Approach on 119.7
Control tower TransAsia 235. Control tower. … TransAsia 235, Control tower.

Contact was lost at 10:53 GMT, just two minutes after departure.

Flight 235 passed over the Huangong Viaduct, where multiple cars with dashcams inadvertently recorded the disaster.

TransAsia Airways Flight 235 – Wikipedia

The aircraft, flying level, first cleared an apartment building. Then it rolled sharply, at nearly a 90-degree bank angle, left wing down. As the aircraft flew low over the elevated viaduct, its left wingtip struck the front of a taxi travelling west on the viaduct, and the outboard section of the wing was torn off when it struck the concrete guardrail at the edge of the viaduct. Two people in the taxi were injured.

The following shows the aircraft in its last moments before it crashed into the Keelung River and the wreckage after (caution, may be disturbing).

As of today (6 Feb 2015), 15 people have been rescued. 35 occupants of the aircraft were killed in the crash and eight are missing. Two were injured on the ground when the aircraft hit a taxi on the road but suffered only minor injuries.

The Taiwanese Aviation Council has released some preliminary data from their investigation, specifically the engine plots from the flight-data recorder. All times are given in GMT.

The blue dotted line is the right-hand engine, engine #2, which is the one that had the original fault. The green line is the left-hand engine, engine #1.

10:51:XX TransAsia Flight 235 received take-off clearance
10:52:33 TransAsia Flight 235 handed off to departure
10:52:38 The aircraft had been airborne for 37 seconds and was at 1,200 feet above mean sea level when a master warning showed that the right-hand engine (engine #2) had failed.
10:52:43 The left-hand engine (engine #1) was throttled back
10:53:06 The right-hand engine (engine #2) auto-feathered.

The director of the Aviation Safety Council said in a press event that there was no flame-out. The right-hand engine shifted into idle mode but the oil pressure never changed. It’s unclear what triggered this.

10:53:12 Stall warning activated
10:53:18 Stall warning ceased

According to the Aviation Herald, at 10:53:19 the crew discussed that engine #1 had already feathered, the fuel supply had already been cut to the engine and they decided to attempt a restart of engine #1. However, I’ve not seen a copy of the cockpit voice recorder data or a news report that it is released, so I’m not sure where this information has come from.

However, there’s no doubt that at this point, the left-hand engine, that is the other engine, was shut down manually. Now the aircraft has no power.

10:53:21 Stall warning activated
10:53:34 Mayday call while multiple attempts were made to restart the engine
10:54:34 A second master warning activated

Half a second later, all devices on the aircraft stopped recording.

Time line showing flight #GE235 events based on ADS-B data from Flightradar24 and data from flight recorders. http://ift.tt/1ADmsU5

— Flightradar24 (@flightradar24) February 6, 2015

Right now, the actions of the pilots make no sense. They clearly believed that an engine had flamed out but even taking this into account, there’s no reason to shut down the other one. The ATR 72 can fly on just one engine so losing the right-hand engine would not have necessarily been an issue.

Right now, it looks suspiciously like this tragedy could have been averted if the pilots had done nothing at all. But this is surprising considering how experienced all of the pilots were and I’m still hoping there will be some other explanation.

The Taiwanese Aviation Safety Council is leading the investigation, with the French BEA representing the country of manufacture and the Transportation Safety Board of Canada representing the country of engine manufacture. They expect to release a preliminary report in 30 days.

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