Instrument Landing System

Washington DC airspace will stay risky

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

Activity in Washington DC’s urban airspace is now being constrained – just a little – by the Federal Aviation Administration following its discovery that the risk of collisions at or near airports across the whole USA is higher than the Agency had appreciated.

This fact emerged during the inquiry by the National Transportation Safety Board (NTSB) and FAA into the 29 January fatal mid-air collision between an army helicopter and regional jet airliner over the Potomac River near Washington Reagan airport.

This decision to reduce traffic, however, is likely to be challenged, and probably quite soon.

The appetite for instantly accessible air transport among DC denizens is insatiable because – they would tell you – of the febrile environment in which many of them conduct their political, lobbying, military or security business in the District. There is always high demand for flights to and from DC’s compact downtown airport close to the heart of the city, and it operates near capacity all the time. Reagan airport is right next to the west bank of the Potomac River, and the other side of the river directly opposite the airfield there is a confluence of urban helicopter routes (see chart below, helicopter routes marked in blue). In addition to that complexity, less than a mile to Reagan’s north west is the Pentagon, with its own heliport.

On the night of the collision the PSA Airlines Bombardier CRJ was approaching Reagan from the south, tracking northward above the Potomac River, intent upon intercepting the instrument landing system (ILS) for runway 01 to land. Meanwhile the army Black Hawk was to the north of Reagan, tracking south along helicopter Route 1 to join Route 4.

Reagan tower asked the CRJ crew if they could accept a late runway change to land on 33, and because the crew could see the lights of both runways they accepted the change, broke off from the runway 01 ILS while still at about 1,700ft, and made a slight right turn to head north to intercept runway 33 ILS. Approaching ILS intercept, the CRJ turned onto final approach at about 500ft. As the CRJ descended through 300ft toward the runway the two aircraft collided.

The circumstances of the collision are not surprising given that these operations were carried out under night visual flight rules (VFR), and the visibility at the time was such that visual identification and separation was practical, if not actually wise. Asked by Reagan tower if they had the CRJ in sight, the Black Hawk crew said they did, although the fact of the collision makes it clear that they had misidentified the regional jet. The lights of the city and airport crowd around on all sides, making misidentification easy.

It has since transpired that the army helicopter was not operating its ADS-B-Out to enable identification by ATC, which it was supposed to do. Right now there is a behind-closed-doors argument going on between the army and the FAA about the military use of ADS-B-Out. The army doesn’t like its aircraft to be trackable, and the FAA insists they must be identifiable in environments like DC airspace. There was, however, no special security classification that demanded stealth for this particular helicopter flight, which was carrying out crew training.

Chair of the NTSB Jennifer Homendy remarked upon the failure of the FAA to respond to the fact that the exact point at which the two aircraft collided had long been identified as a “high risk location”. This failure, she said, was “more than an oversight.” When it was published in early March, the NTSB’s preliminary report on the accident revealed that, between October 2021 and December 2024, there had been more than 15,000 “close proximity events” between helicopters and commercial aircraft near Reagan.

It may be a useful exercise to gather statistics like that to back an argument, but anyone who operates the skies near Reagan knows how busy it has always been, and knows that such a level of traffic density involves considerable risk, especially at night or in poor visibility. The operational requirements for a helicopter heading south on Route 4 are that, when passing Reagan, it is supposed to be at 200ft or lower, so that any aircraft on approach to runway 33 should pass over the helicopter at a height between 300ft and 400ft. The margins for error are tiny, both for vertical separation between the two aircraft, and for obstacle clearance between the low-flying helicopter and ground obstructions, especially risky at night.

The FAA has now decided to close Route 4 whenever runway 33 is in operation. But what if, like the day of the accident, the tower decides at short notice to change a landing from runway 01 to 33? Can sufficient notice be given to helicopter crews using Route 4? The agency plans to allow some limited helicopter traffic on Route 4, but only for “urgent missions, such as lifesaving medical, priority law enforcement or presidential transport”. Unfortunately such flights over this city are common, and there is a question as to who should authorize them. Meanwhile ATC will be expected to prohibit fixed-wing aircraft from simultaneously using Reagan airport’s secondary runways – 15/33 and 04/22. That combination of responsibilities is quite an ask for controllers as busy as those at Reagan.

The FAA’s administrator Chris Rocheleau, at a Congressional Hearing on 27 March, obviously bidding for the Understatement of the Year Oscar, said: “Clearly, something was missed.” The NTSB’s Homendy pointed out that the DC airspace incident data is there to be easily gathered, in the form of voluntary safety reports of near-accidents of all kinds, but admits there is a lot of it. Rocheleau says the Agency is now looking into using artificial intelligence to sort through “tens of millions” of such reports to identify – and flag up – specific risks and trends.

Urban aviation activity like that in Washington DC’s airspace would not be permitted in similar European airspace. Instrument flight rules (IFR) would apply, even if visual separation was used as a backup in VMC. That is not to say Europe is right and America is wrong. Each State has a right to decide what level of risk it finds acceptable, and to determine ways of ensuring that its agreed standards are met, in the knowledge that the authorities will take the rap if they get it wrong.

That is the question Washington DC must answer: how much risk do its denizens want to take, and should they be allowed to take risks at that level? In the 29 January collision all the people on both aircraft died, but the machinery fell harmlessly into the river. In a future collision, that might not be so.

In DC, my money is on a win for the risk-takers who are not prepared to slow down.

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.