birdstrike

Air India suffers the first fatal crash involving a 787

David Learmount Uncategorized , , , , , , , , , , , ,

Boeing’s long-range widebody 787 has been in service since 2013, and had some worrying technical problems in early service. Those, however, were corrected and it had been crash-free until now.

There has been very little information for investigators to work with since the Air India 787-8 crashed just after take-off from Ahmedabad today.

There are reports of an urgent Mayday call from the crew during the brief airborne period. The 787 appears to have reached a maximum height of about 600ft before descending, wings-level, in a nose-high attitude, to impact with buildings about 1.5nm from the runway’s end. An explosion followed, resulting from the large amount of fuel on board contacting hot engine parts when the crash breached the fuel tanks. The aircraft had been fuelled for the scheduled ten-hour flight to London Gatwick.

Powered by twin GE Aerospace GEnx engines, the 787-8 took off from Ahmedabad at 13:40 local time in good weather, carrying 242 passengers and crew. Initial reports from the site indicate that all on board died except for a single passenger who was thrown clear, and has survived. There are expected to be many casualties on the ground, but the numbers are not known at present.

Looking at a video of the last few seconds of the flight, the landing gear still remains down, the flaps look as if they are still at a take-off setting – but the video quality is so poor that cannot be stated with certainty – and the aircraft is in a steady descent which only ended in impact with buildings and the ground.

At this point after take-off, the gear would normally have been retracted and the aircraft would have been climbing rapidly. The steady descent actually witnessed in the video suggests the crew could not command sufficient power from the engines to keep the aircraft level, let alone to climb.

If that is true, what had happened to deprive the pilots of power from the engines? Had they suffered a multiple birdstrike that damaged both engines? No-one so far has reported a flock of birds in the departure path.

And failure of a single engine should not cause a crew to lose control of a modern airliner, even in the critical early climb phase. The video shows an aircraft that looks under control, but unable to climb.

Simultaneous engine failures for unconnected reasons simply do not happen, according to the entire history of aviation accidents. So if there was a failure of both, what could have caused it?

Frankly, we don’t know for certain in this case if engine power was the problem, but if you go looking for a potential cause of multiple engine failure, fuel contamination could do it. Again, however, history is against that potential cause in observed reality.

Could the pilots not demand the nose-up attitude they actually wanted because of some technical limitation? Well, that happened in the notorious 737 Max cases, but there is virtually no commonality in the way the 737 Series controls work and the manner in which the 787 Series operates.

So we have to wait for the investigators to report. These days, if the Indian investigators follow today’s recommended protocol, after about a month they will provide factual data of which they are certain, even if the final verdict is not yet clear. The aircraft’s “black boxes” – the cockpit voice recorder and flight data recorder – will provide data on what the aircraft actually did, and may throw some light on why it did it.

Meanwhile, be patient. This kind of accident is incredibly rare these days, and finding the truth behind it could not be more important.

Jeju Air – the missing four minutes

David Learmount Uncategorized , , , , , , , , , , , , , , , ,

Birdstrikes on airliners are not rare, but they don’t usually cause crashes, let alone fatal ones.

The most famous birdstrike accident before the Jeju Air crash at Muan, Korea a little more than a month ago was the “Miracle on the Hudson”, in which a US Airways Airbus A320 climbing away from take-off at New York LaGuardia airport in January 2009 hit a flock of large geese that disabled both engines. What followed captured the public’s imagination to the extent that Hollywood made a movie about it.

When the geese collided with his aircraft, Captain “Sully” Sullenberger made the decision not to attempt a turn-back to land on the runway, but to glide down for a ditching in the Hudson River. All 155 passengers and crew survived the ditching in the river’s freezing water.

Moving forward 15 years, the Korean aviation and railway and accident investigation board (ARAIB) interim report on the 29 December 2024 Jeju Air crash at Muan International Airport has now confirmed that the chain of events leading to the accident also started with a birdstrike on both engines. The Boeing 737-800, on final approach to runway 01 at Muan, ran into a flock of small ducks which caused the engines and the aircraft extensive damage. Details of the extent and nature of the damage have not been established, but it is clear that some of the aircraft’s electrical systems stopped working.

Much more would normally be known at this stage, but the flight data recorder (FDR) and cockpit voice recorder (CVR) stopped operating at the time of the birdstrike (08:58:50 local time), depriving the investigators of extensive data about the last four minutes of the flight that would otherwise have been captured. Simultaneously the aircraft’s ADS-B transmissions that enable the its three-dimensional trajectory to be tracked in real time also stopped, so it will be more difficult to establish the precise course the crew flew in order to line up for the emergency landing they chose to make.

It was at 08:54:43 that Jeju Flight 7C2216, inbound from Bangkok, Thailand, had first contacted Muan Control Tower and received clearance to land on runway 01. If they had not already done so, at that point they would have selected the undercarriage down and set the flaps for landing.

The first hint of the problems the flight was about to face came four minutes later when the Tower warned the Jeju pilots of bird activity ahead (08:57:50). At that point they were about 3nm from their anticipated landing. The electrical failure that stopped the two recorders occurred a minute later at 08:58:50, at which time the aircraft was still 1.1nm away from the threshold of runway 01, according to the ARAIB report.

The crew saw the flock of ducks ahead and below them just before the birdstrike, it seems, so they decided to abandon the approach and carry out a go-around, increasing engine power and starting to climb away. Six seconds later, at 08:58:56 local time, they declared a Mayday emergency, citing a birdstrike, and announcing their go-around, which had now become far more difficult to carry out because of reduced power from the damaged engines.

The report emphasizes that recordings during the last 4min 7sec of the flight are missing. That is the time that elapsed between the electrical failure that stopped the recorders and the moment of the 737’s violent collision with the earth and concrete mound beyond the end of the landing runway in which the ILS localizer antenna array was embedded (09:02:57).

Image from ARAIB interim report

As they initiated their go-around, the pilots felt – and heard – the birdstrike and witnessed a loss of engine thrust just after they had advanced the throttles to climb away. As a part of the go-around drill the crew retracted the undercarriage and selected the flap fully up. There is no recording to confirm this, but they must have done so, as events in the next few minutes make clear.

The attempt to save the flight

The crew knew they had to get the aircraft on the ground fast in case the damaged engines failed completely, but by this time they were losing sight of the runway 01 threshold below the nose as they initiated their go-around, so landing ahead on 01 was no longer an option. Circling back to set up a new approach to the same runway was risky because they might not have sufficient power to maintain height for that long. The ARAIB report says that the last pressure altitude recorded was effectively 500ft (498ft to be precise), and indicated airspeed was 161kt.

At such a point the pilots would want to gain any height and speed they could with the remaining engine power so as to increase their gliding range in the event of total engine failure, and to stay withing gliding range of the runway. So their decision was to fly ahead, then turn through 180deg to land on the same runway but in the opposite direction – that is designated runway 19. Because, during the go-around, they were positioned to the left of runway 01 and parallel to it, they were committing to a right turn to reverse their heading and line up for the approach to 19.

The workload and stress on the pilots at that moment were massive. They did not know how much engine power they would have, or how long they would still have it, so the temptation to turn early to line up on the runway was high. Video of the aircraft’s arrival on runway 19 at Muan shows the aircraft touching down gently with its wings perfectly level, but nearly 2/3rds of the way along the tarmac, travelling very fast with no flaps set, the undercarriage still retracted, and no spoilers deployed.

With the data available at present there is no way of knowing whether the crew failed to get the flap and gear down because of hydraulic problems, or whether the high workload and lack of time made them forget to deploy them. Apart from the failure of electric power to the flight recorders, the investigators don’t know what other problems the pilots faced.

It’s even difficult to work out why an external collision with relatively small birds (Baikal Teals, average weight given as 400g) would cause an electrical supply to fail, unless the undercarriage was still down at the point of birdstrike, leaving electrical wiring and hydraulic tubing in the gear bay vulnerable to impact damage.

Almost all the 181 people on board the Jeju 737 were killed, the only survivors being two cabin crew strapped into their seats in the tail of the aircraft. Everyone on board would still have been alive until the high speed impact with the solid foundations for the ILS localiser antenna array about 200m into the runway overrun, which caused the aircraft to break up and catch fire.

Question for the Korean authorities: what was that obstruction just beyond the Muan runway end?

David Learmount Uncategorized , , , , , , , , , , , , , , , , ,

It will not be long before accident investigators reveal the reasons why the Jeju Air Boeing 737-800 crew felt they had to commit to a flapless, gearless landing on runway 19 at Muan, South Korea. But the reason so many people died was not the landing as such, but the fact that the aircraft (HL8088) collided with a very hard obstruction just beyond the runway end.

That collision broke up the hull and caused a conflagration. What was the obstruction, and why was it positioned on the runway extended centreline only about 200m beyond the runway threshold?

It looks as if it was a concrete anchorage for the Instrument Landing System (ILS) antenna array. ILS antennae are often just beyond runway ends, but they are normally designed to be frangible so any aircraft that collides with them suffers only minor damage. This was hard. Very, very hard.

The sequence of events that led to this accident began with the aircraft approaching runway 01, cleared to land, but the crew elected to go around just after ATC had warned them of a potential birdstrike. It looks as if a birdstrike did, indeed, take place, and the crew declared a Mayday emergency shortly after that.

The crew then elected to land on the same runway but in the opposite direction – on runway 19. This was not much of an issue because the wind was very slight and the visibility was excellent.

But when they returned for the fatal landing on 19 they touched down with no flaps and no landing gear. Why? Perhaps because the birdstrike caused the right engine to fail, and all or some of the hydraulics with it. And the gear and flaps are hydraulically powered.

We don’t know yet, but we will know soon.

Meanwhile the touchdown was as good as a flapless/gearless touchdown could be: wings level, nose not too high to avoid breaking the tail. But being flapless, the airspeed was very high – probably around 200kt.

Look at the video of the landing run. The aircraft slid the full length of the runway with the fuselage, wings and engines substantially intact, and with no fire. It slid over the end still going fast – maybe 70kt or so, but still with no further substantial damage to the structure and no fire.

Then the aircraft hit the obstruction about 150m beyond the hard runway overrun, but until impact it remained substantially undamaged and fire-free. At impact, the hull buckled and broke up, the wing fuel tanks were ruptured and instantly exploded into flames. The wreckage came to rest just beyond the obstruction, near the wire perimeter fence.

If the obstruction had not been there, the aircraft would have slid through the antenna array, across the level ground beyond it, and through the wire perimeter fence. It would have come to rest with most – possibly all – those on board still alive.

We will soon find out the whole truth about why the landing took place as it did. But because the accident killed all on board except two of the cabin crew, those answers will be almost academic. The question to answer is: what was that obstruction, and why it was there?