Backup System Helped Pilot Control Jet

The Wall Street Journal, Jan. 20, 2009

As the captain of US Airways Flight 1549 prepared to ditch his disabled jet in New York's Hudson River, he had some help from some last-resort equipment that apparently kept the plane's electrical and hydraulic systems working even as both engines nearly shut down.

After striking what is believed to be a flock of large birds, which disabled both of the plane's engines, Capt. Chesley B. Sullenberger III maneuvered the plane to glide some 3,000 feet without power and splash down as slowly as possible in the river Thursday. All 155 people on board the flight from New York's La Guardia airport en route to Charlotte, N.C., were able to escape safely, a feat air-safety experts consider one of the most difficult in aviation.

The generators that routinely provide electricity weren't available because they are driven by the aircraft's engines -- which weren't putting out sufficient power after apparently having ingested several geese. But the plane's auxiliary power unit -- made by Honeywell International Inc. -- was operating during the descent and gave the pilot full use of the jet's flight-control system, according to a spokesman for the National Transportation Safety Board and other people familiar with the details.

Crash investigations determined that a so-called ram air turbine -- which can be used to regain hydraulic pressure when both engines stop working -- also was deployed before the touchdown, board spokesman Peter Knudson said Monday. It isn't clear whether the crew deployed the turbine, or whether it deployed automatically because of the emergency. The device consists of a small propeller that drops out of the bottom of the craft, and then drives a hydraulic pump and also supplies backup electricity at certain speeds to help operate the plane's flight controls.

A spokesman for the U.S. Airline Pilots Association, the independent union that represents US Airways Group Inc. pilots, declined to comment on the details of the accident.

According to one person familiar with the investigation, Capt. Sullenberger was able to keep the nose of the plane up while flying at a reduced speed partly because his aircraft's so-called fly-by-wire system used computers to prevent the jetliner from stalling, or becoming uncontrollable and falling out of the air. Preliminary data indicate that these computer-controlled safeguards remained fully operational until touchdown, this person said.

Gary Hummel, training committee chairman for the U.S. Airline Pilots Association, said Monday that the pilots do train for dual-engine failures in simulators, but at much higher altitudes.

Mr. Hummel, who has flown the A320 in the past but now flies Boeing 767s for US Airways, says the carrier's pilots "do not practice ditching" in simulators. "Those procedures are covered in ground-school instructions," he said. "Ditching is so rare, such an unusual occurrence" that pilots don't routinely practice it except in ground school, the "chalk and talk" method of instruction as opposed to simulators.

A spokesman said US Airways has its pilots practice dual-engine failure in the simulator. However, that training "includes successful ignition" of one engine. The company also said "ditching is not something easily replicated in a simulator."

One possible fallout from the US Airways incident, according to safety experts, is that airlines now have specific data to feed into simulators to help pilots understand the flight-control movements and glide characteristics that saved Flight 1549. "Airlines that fly Airbus planes are all likely to be looking at eventually incorporating such data into their training," said John Goglia, a former NTSB member.

But in addition to basic flying skills, the ditching also underscores another factor pilots should consider in surviving such emergencies: the need to quickly choose a course of action, even if it goes against normal procedures. Barely 30 seconds after his aircraft hit the birds and lost nearly all thrust from both engines, the captain disregarded the advice of air-traffic controllers and decided that ditching in the Hudson was the best option.

"The timeliness of that decision gave the crew time to set up properly" for touchdown more than two minutes later, according to Richard Healing, a former safety board member. "Good judgment allowed them to use their skills to make that perfect landing."

Investigators continue analyzing the A320's maintenance records to determine if there were any previous repairs or incidents that may be relevant to the current probe. But at this point, experts from the safety board and industry increasingly are convinced that until colliding with the birds, last Thursday's flight was routine and didn't experience any unusual events, according to one person who has discussed the matter with investigators.