National Transportation Safety Board
Washington, DC 20594
February 12, 2009
FOURTH UPDATE ON INVESTIGATION INTO DITCHING OF US AIRWAYS JETLINER INTO HUDSON RIVER
The following is an update on the National Transportation Safety Board's investigation of US Airways flight 1549, which ditched into the Hudson River on January 15, 2009. The bird remains found in both engines of US Airways flight 1549 have been identified by the Smithsonian Institution's Feather Identification Laboratory as Canada Goose (Branta canadensis).
The lab made the identification for the NTSB through DNA analysis as well as through morphological comparisons in which feather fragments were compared with Canada Goose specimens in the museum's collections; the microscopic feather samples were compared with reference microslide collections.
A total of 25 samples of bird remains have been examined as of today. Additional analysis will be conducted on samples received from the NTSB to attempt to determine if the Canada Geese were resident or migratory. While no determination has been made about how many birds the aircraft struck or how many were ingested into the engines, an adult Canada Goose typically ranges in size from 5.8 to 10.7 pounds, however larger individual resident birds can exceed published records.
The accident aircraft was powered by two CFM56-5B/P turbofan engines. The bird ingestion standard in effect when this engine type was certified in 1996 included the requirement that the engine must withstand the ingestion of a four-pound bird without catching fire, without releasing hazardous fragments through the engine case, without generating loads high enough to potentially compromise aircraft structural components, or without losing the capability of being shut down. The certification standard does not require that the engine be able to continue to generate thrust after ingesting a bird four pounds or larger.
NTSB investigators worked closely with wildlife biologists from the United States Department of Agriculture, both at the scene of the accident in New York City and during the engine teardowns at the manufacturer's facility in Cincinnati, to extract all of the organic material that was identified today.
NTSB Media Contact: Peter Knudson
There were 18 turbofan aircraft hull losses from 40,286 reported bird strikes in the US between 1990-2006, says R.A. Dolbeer basing on USA National Wildlife Strike Database: (http://www.davvl.de/Volu%20englisch/2007/Dolbeer.pdf
That’s 1 hull per 2238 bird strike, and vast majority small twin engine jets. There were at least 120 million US commercial airline departures, 1990-2006. Please, check and correct my facts as necesary.
94% of these strikes, says Dolbeer, occurred on takeoff roll or "wheels-off" <100ft above aerodrome elevation. 6% occurred on departure (>100ft) or short final or en route.
There were approx. 10 million commercial airline departures in the US in 2006 (just under that in 2008), on back to about 6 million in 1990. Or 1 hull loss per 6.7 million average departures from bird strike.
Cactus 1549 is purported to have collided head-on with a flock of waterfowl over the Bronx in clear skies. The only jet airliners on international record to collide head-on with a flock of waterfowl in ‘formation’ (not spooked into scattered flight during takeoff roll, wheels up or short final) took the flock by surprise at high speed out of a cloud bank.
In 1995, on approach into JFK, a Polar Air Cargo 747 broke out of the clouds at 7500’ straight into a flock of snow geese that had no time to evade. The collision caused significant airframe damage and knocked out ‘one’ engine. The crew reported a flurry of “sandbag”-like thuds. (www.birdstrike.org
Turbofans, even though regulations say 4lb, are built to withstand one-off 8lb bird ingestion. It takes two or more 8lb birds to knock out an engine.
Departure (wheels up and initial climbout) is where most turbofan bird ingestions occur due to TO-power N1 in bird central congregation habitat. The odds of a turbofan-powered jet striking a bird in all stages of flight are 3000:1, and after beating these odds 33:1 will result in “substantial engine damage” and 44:1 that this damage will occur above 100ft AAE (Dolbeer). Tall odds.
Odd that have yet to factor in clear sky conditions, flight crew experience, skill and vigilence, medium full-time staffed radar, PIREP, passengers statements, and the remarkable little aviators themselves, the waterfowl.
With Cactus 1549 the only twin engine commercial airliner departure to be downed by a purported flock out of all US departures between Feb. 2008 and Jan.2009 is a 1 in 10 million occurence.
The odds of hitting acutely vigilant waterfowl on full-time high alert for predators over the Bronx in clear skies are even taller.
Did I mention that the airline industry loses money on the whole, needs massive public subsidy to be sustained, engages in vicious price wars and exposure of potentially lethal component defects tantamount to catastrophic?
The odds of a predator high alert flock failing to collectively detect and evade a huge strange looking threatening bird bearing down on them from 4nm in clear sky are next to none. As is no other airframe damage by 10lb birds at 180kts make. Same for two birds per engine just happening to be side by side or line astern perfectly lined up in the path of each 1549 turbofan intake. The combined odds of a first officer hitting an entire flock in clear skies from 4nm and the captain letting it happen, unthinkable. The odds of TRACON radar plus prior departing crews not detecting these very birds in clear skies, just incredible.
The odds of 149 passengers reporting solitary ‘loud BANG!’ against one saying ‘thud’, self-explanatory. The odds of every passenger this very aircraft three before all reporting a loud bang then lights out, also self-explanatory. The odds of any passenger seeing any blurry object fly past their window in 1st class taking to co-passenger to their immediate right, forget it. The odds of identifying this blur, even if did detect, impossible. Only confirmation by labs like the Smithsonian can correctly identify, and I seem to recollect that it takes a whole lot longer than this unbelieveably fast test result to identity. The odds of smelling bird in the cabin, contrary to some passengers, impossible.
Ingested bird is shredded and ejected in a blink. Whatever sidewall blood spatter remains is air-dried at the engine’s forward velocity, in this case, about 180kt. Bleed air is drawn 'before' the fuel stage. Bird remains travel so fast through the super hot high compressor air that don’t have time to combust. The only ‘engine-related’ contaminants in the cabin occur from faulty valve leak of lubricating oil, etc, requiring a steady supply over minutes, maybe hours mixed and diluted with ambient air from the ram air inlets to the parts per million point of humanly undetectable. And why passengers get headaches, dry eyes without ever knowing why. A bird goes through too fast.
Even if I'm totally incorrect and 1549 really did it birds. This crew bullseyed a visible and avoidable airborne danger, therefore massive crew negligence at bare minimum. Along with TRACON negligence not to identify an airborne threat in clear skies; no prior crew off 04 bird PIREP in clear skies; acutely vigilant birds to make no effort of avoidance with 4nm to do so; no compressor surge and stall by the same engines three days before over Newark, and a spotless CFM 56-5B operational history with no operator complaints.
Just out of curiosity. How did the Brantus canadensis feather evidence stick around after an approx. 150kt inrush of Hudson River water, powerful enough to rip the #2 off, flushed through them on touchdown and yet left no dried blood spatter?