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Hearings Reveal Definition of Ditching Needs Upgrading

Sun, Jul 26, 2009 — David Evans

Articles, Featured

There’s no question that US Airways Captain Chesley Sullenberger and his first officer performed a superb feat of airmanship in ditching their stricken Airbus A320 on the Hudson River and saving the lives of all 150 passengers and 5 crew aboard. (See Aviation Safety Journal, ‘Ditching After Bird Strike Probed by Safety Board’) What is also clear from the recent National Transportation Board (NTSB) fact finding hearing on the 15 January 2009 event is that there are serious issues of aircraft and engine certification, and a real anomaly concerning Federal Aviation Administration (FAA) efforts to mitigate the hazard of bird strikes.

This was evidenced, in part, by the absence of any questions from one of the parties to the investigation present for the three-day hearing. That was US Airways, whose senior representative could simply have had a tape recorder playing into the microphone, telling NTSB Member and Presiding Officer Robert Sumwalt, “US Airways has no questions, Mr. Chairman”

Of course not. US Airways has no issues as the event proved that their crew selection and training, their evacuation procedures and their overall handling of the event were above reproach. There was nothing for the airline to gain by bringing up tough issues, especially with a gazillion court cases pending from the passengers.

The same could not be said for aircraft manufacturer Airbus, or the FAA, both of whom were designated parties to the investigation and had plenty of questions – questions that shed light in a way probably not intended. The contradictions strained credulity.

The only thing that could be called criticism of US Airways was when First Officer Jeffrey Skiles remarked about the artificiality of training, but that remark could apply to any airline:

“One of the training spots was dual engine failure, but it was performed at altitude with plenty of time to do procedures. This training really did not have an effect on the accident, which happened extremely fast. The newspaper said it was only3 minutes from the time the birds hit until they [flight 1549] touched down. They did not have much time and were already quite slow. They were not in the relight envelope. The current training philosophy was to take your time to try to assess the situation. It did not apply in the actual accident.”

Sullenberger said when they flew into the flock at about 3,000 feet after takeoff from New York’s LaGuardia airport he heard many birds striking the airplane. It sounded, he said, like it was “raining birds.” Fortunately, the Canada geese did not hit the windscreen.

Sullenberger, an experienced glider pilot, was at the helm of an A320 glider, all thrust from the engines having been lost as a result of the bird ingestions (2 geese into the left engine, 1 goose into the right engine).

The option of gliding back to LaGuardia was quickly ruled out, as the airplane was too low and too slow to make the runway. The Hudson River appeared as the only option.

Rear exits were unusable. Passengers were lined up on the left wing all the way out to the tip. Note that the rafts are still attached to the doors; no one could figure out how to cut the attachments so the rafts could float free.

Rear exits were unusable. Passengers were lined up on the left wing all the way out to the tip. Note that the rafts are still attached to the doors; no one could figure out how to cut the attachments so the rafts could float free.

“The impact was violent,” said passenger Billy Campbell, who was seated in the next to last row (seat 25A). “The airplane submerged, it was almost like looking out a porthole … The water rose very rapidly, and I thought the airplane was going to sink.”

Even though the landing was on water, Captain Marc Parisis of Airbus Flight Operations and Support Services maintained it was not a ditching. “Ditching is a planned event. This was an emergency landing with no time to prepare the aircraft.”

Airbus officials maintained that a “ditching” involves not only time to prepare the aircraft and passengers, but also that thrust is available from the engine. A ditching, to Airbus, is a planned, powered, controlled event.

“There’s no definition of ditching without engine power,” said Parisis.

The regulatory definition of ditching assumes that the aircraft sink rate, in the moments before impacting the water, will not exceed a rate of descent of 3.5 feet per second. Moreover, the regulations address water leakage, to wit, that water must not reach the door sills on the main deck until passenger evacuation is complete.

In the case of flight 1549, Sullenberger’s sink rate just moments before water touchdown as on the order of 13 feet per second – or about 3.7 times greater than the certification standard. The impact crushed the rear fuselage skin and permitted water to be scooped into the tail cone. That water pushed through the rear pressure bulkhead. The weight of water dragged down the rear of the aircraft, rendering the rear exits unusable.

Damage on impact allowed water into the fuselage, which rammed through the rear pressure bulkhead. By not calling it a ditching, aircraft certification issues are not raised -- for example, the durability of the read pressure bulkhead when landing on water.

Damage on impact allowed water into the fuselage, which rammed through the rear pressure bulkhead. By not calling it a ditching, aircraft certification issues are not raised -- for example, the durability of the read pressure bulkhead when landing on water.

For ditching certification, the evacuation must be completed by the time any exit first goes under water.

When landed under certification standards, there is no water damage.

One has to question the certification envelope. Here was a landing on glass-smooth water, on a clear day, wings perfectly level, where an experienced glider pilot in effect “greased” the landing. Yet there was damage to the watertight integrity of the fuselage, and slide rafts that should have been available weren’t (the ones attached to the submerged rear doors, which is why passengers crowded onto the wings).

Now consider a ditching on the open ocean, with swells, at night, with less experienced pilots at the controls. Remember, the airplane is designed to be flown by the “average” pilots, not one with the test pilot-like skills of Sullenberger.

Ditching standards clearly need to be more realistic. Of course, upgrading those standards may impose added performance and weight to the aircraft, hence the Airbus position, and the FAA’s, that this was an unplanned, emergency landing on water, not a ditching.

“It was a forced crash landing,” said the FAA’s Bob Breneman. “He’d have put the airplane down on a golf course or a highway if the Hudson River wasn’t available.”

But there are significant difference, obviously between a landing on terra firma and one in the water. Not the least, landing in water puts the airplane into a few million gallons of fire suppressant (the water).

NTSB staff member Jason Fedok put up on the viewscreen, for all to see, an Airbus publication, “Getting to Grips With Cabin Safety,” in which ditching was described as follows:

“The definition of ditching is ‘A deliberate emergency landing on water, where the aircraft touches down under control.’ However, in commercial aviation this is a rare occurrence.”

“Given the Airbus definition, wouldn’t this [flight 1549] be a ditching?” he asked.

“This wouldn’t be a ditching because the cabin crew didn’t have time to prepare the cabin,” said Airbus’ Hans-Juergen Lohmann.

The FAA’s Jess Gardlin chimed in, “This accident doesn’t suggest we look at all the evacuation/ditching regulations.”

It seems to this observer that the Airbus definition of ditching is actually the right one to use, and that the definition used for regulatory purposes – which assumes the engines are functioning – is outdated if not entirely artificial.

With respect to certifying the engines’ ability to absorb bird strikes and keep functioning, the FAA’s Robert Ganley said, “If certified today, the engine would be tested to one 6 lb bird standard.” It is estimated the left engine on the accident airplane ingested two birds weighing 16 lbs apiece.

Top: damage to inlet guide vanes. Bottom: fractured compressor blades.

Top: damage to inlet guide vanes. Bottom: fractured compressor blades.

“These were flocking birds, yet you test against only one going into the engine,” noted the NTSB’s John DeLisi.

“We have to look at a high level of safety, but also to standards that can be met,” replied the FAA’s Marc Bouthillier. He added that birds weighing more than 8 lbs “did not show up” in the FAA’s recorded history of engine bird ingestions. “This incident is unprecedented in our data,” he explained.

The FAA’s Robert Ganley, manager of the agency’s engine standards staff, took a more positive approach. “This event is telling us we need to update the database of bird ingestion,” he declared. “Then, once the database is updated, we’ll look at certification rules.”

Regarding the presence of birds near airports, news reports currently tout the FAA’s efforts to test and deploy bird-detecting radar. However, the flock encountered by flight 1549 was outside of the normal airport surveillance area. The geese that brought down the airliner were much higher and further out, flying some 4 miles distand at an altitude of about 3,000 feet on a migratory route.

Airport efforts to mitigate the presence of birds would not cover these migrating flocks, which typically involve 50-100 birds.

It is also evident from the NTSB presentations of the encounter that radar plots of these migrations are available. But they are not included in weather reports or other information provided to pilots. One would think that avian hazards could easily be added to routine whether reports.

A radar plot, showing the intersection of flight 1549 with the path of the migrating Canada geese. If such plots can be produced after the fact, then obviously radar data on bird flights is available beforehand and could be included in crew weather reports.

A radar plot, showing the intersection of flight 1549 with the path of the migrating Canada geese. If such plots can be produced after the fact, then obviously radar data on bird flights is available beforehand and could be included in crew weather reports.

One thing is clear from the hearings: the definition of ditching is highly artificial.

As Member Sumwalt asked, “What would be the advantage of looking at this event as a ditching?”

The FAA’s Breneman replied, “We’d have to scrap everything about ditching and revisit everything.”

Precisely.


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