US Airways Splashdown on the Hudson

The Hudson River touchdown of US Airways flight 1549 has been called a miracle by some folks. How these folks would describe the ingestion of a flock of birds in terms of miraculous phenomena has not been disclosed. Whatever it was, the aircrew certainly performed admirably.

If you look at a map of the flight path and note the timing, one minute after the birdstrike the A320 had descended from 4000′ to 2000′. At this phase of flight 1549, the airplane is heavy with fuel, baggage, and people. They are configured for climbout and are navigating in congested airspace at low altitude.  At least one of the pilots has his head on a swivel watching for traffic while the other is monitoring flight control systems.

After the birdstrike, there would be some seconds of confusion where the pilot and first officer would have to analyze the warning annunciators as well as what story the flight instruments are telling them. Loss of power on climbout means a prompt loss of airspeed. Here the pilot and first officer would coordinate their cockpit duties. One pilot will concentrate on flying the airplane while the other would, for instance, focus on an engine restart, declaring an emergency with the tower or TRACON, notify the cabin crew for emergency procedures, etc.

While the pilots are determining what kinds of flight controls they have to work with and what other failures may be unfolding, they have to establish a standard airspeed that will minimize their decent rate. This gives them more time in the air and correspondingly, more landing options.

An airplane does a coordinated turn by banking the wing and tilting the lift vector in the direction of the turn. As you tilt the wing, the force vector acting against gravity becomes smaller and without coordinated input from other controls and a bit of power, the airplane will begin to sink.

The point is that when you bank an aircraft during a deadstick glide, you will increase the sink rate. Looking at the map, the pilot could not afford to lose anymore altitude by attempting to make a gliding turn to Teterboro to get lined up with the runways. They had no choice but to continue straight forward along the direction of the river and hope they could land in the water without dipping a wing and cartwheeling the airplane.

I’d say the aircrew made a series of good decisions.

7 thoughts on “US Airways Splashdown on the Hudson

  1. John Fetzer

    With no thrust, simple ballistics says gravity would limit the time greatly and that the descent would be pretty fast, even in a gliding mode. The crew took a very limited set of circumstances and chose one of the few series that worked.

    Reply
  2. gaussling Post author

    I’ve heard that the A320 has a glide ratio of 20:1. I’m not sure I believe this, especially near max gross takeoff weight. But the airplane can be trimmed to give a predictable glide. The hard part is dealing with ground obstacles, i.e., bridges, ferries, etc.

    Reply
  3. morris

    The NTSB report, (if public?), should be fascinating. It will be refreshing to read about no loss of life and what went right. The shuttle report you linked previously was detailed and tactful, but this one might be the most positive investigation report I’ve ever read.

    Reply
  4. Han Solo

    Excellent narration.

    For the reading impaired you can see the coast guard footage.
    Must fast forward to about 2 minutes into the video.

    Reply
  5. Jordan

    When I was in grad school, I used to fly home for visits on an A320 all the time.

    Gaussling — what would the ground speed of the plane have been just before impact? Is the A320 designed to float like that — nose-up?

    Reply
  6. gaussling Post author

    The actual landing speed depends quite a bit on the weight of the aircraft. According to the charts I’ve seen, at 170,000 lbs, the landing speed Vref is 147 knots indicated airspeed (KIAS) with full flaps. At 100,000 lbs, the full flaps landing speed is 112 KIAS. Ideally, the pilot would try to flare the aircraft in ground effect and float as long as possible, bleeding of airspeed before touchdown. Who knows if that was an option?

    Click to access A320PERFORMANCE.PDF

    It’s hard to say why the jet floated the way it did. Maybe the aft spaces flooded faster than in the front.

    Reply

Leave a comment