38
$\begingroup$

A comment by @AsheeshR says:

The Hudson River Landing was due to a combination of piloting skill and an autopilot system that was engaged right till impact and kept the plane in a controlled descent within a safe flight envelope.

It was an Airbus aircraft, so the autopilot has priority over pilot input, but how exactly did the autopilot play a role in getting them down safely?

What exact procedures did Sully and the crew follow when landing? Was there anything in addition to standard ditching procedures, that might have contributed to them landing in one piece?

Improve this question
$\endgroup$
16
  • 7
    $\begingroup$ @RedGrittyBrick You're right, but it wasn't pressed on this particular flight. $\endgroup$
    – Danny Beckett
    Commented Mar 25, 2014 at 15:35
  • 10
    $\begingroup$ @flyingfisch See youtu.be/Zzjbubs59Ks?t=23m45s - it was at the end of the checklist, which they didn't have time to complete. $\endgroup$
    – Danny Beckett
    Commented Mar 25, 2014 at 15:36
  • 6
    $\begingroup$ @flyingfisch The ditch switch is meant to close openings in the fuselage through which water would make ingress, and slow flooding of the fuselage; however, it wouldn't have done much good in this situation, because the forces of impact ripped holes in the hull anyway. $\endgroup$
    – tgies
    Commented Mar 25, 2014 at 17:33
  • 3
    $\begingroup$ I have no idea if this was deliberate, skill, luck or accident and I can find no reference; If you watch the video, it seems to me that he touched down with low speed but not so low that the pitch angle would be such that the tail would dig in and slap the fuselage down or shear it off. Looks like the tail dragged just enough to bleed off the speed and settle the fuselage down. I saw an interview with an experienced SLF who said that the forces when the fuselage leveled were not that much higher than during a firm arrival such as might be experience in a 737 in bumpy conditions. $\endgroup$
    – Simon
    Commented Mar 25, 2014 at 20:12
  • 3
    $\begingroup$ @NickT In a Boeing, ultimate control is left to the pilot, and the aircraft will not override the pilots' inputs. In Airbus aircraft, the opposite is true. Ultimate control rests with the autopilot, which the pilots cannot override. $\endgroup$
    – Danny Beckett
    Commented Mar 27, 2014 at 12:29

3 Answers 3

Reset to default
36
$\begingroup$

The NTSB report is a great resource when looking for information about an incident like this.

There is an Engine Dual Failure Checklist discussed starting in section 1.17.1.2 of the report. This includes steps to attempt restarting the engines, and further steps depending on whether or not the engines can be started, and finally steps to help prepare for a forced landing. Pilots train on engine failures regularly, so they are already familiar with the procedures. The report discusses how their actions compared to what the checklists say. Since the incident occurred at such a low altitude right after takeoff, they didn't have time to complete all of the steps. They did what they had time for, and had to make quick decisions about what their options were.

The report also discusses in section 1.17.3.2 the ditching training the pilots received. There was guidance in the manual, but no specific scenarios included in their simulator training.

The autopilot is great for use in normal situations. However, as soon as anything is going wrong, the pilot should take control of the plane. You do not want to take time to figure out "what's it doing now" in a difficult situation. So in this situation, the autopilot probably disconnected when the engines went out, or was manually disconnected by the pilots.

Section 1.6.3 talks about the flight envelope protections. I believe these protections are what you are referring to when you say that the autopilot has more control. They are designed to protect the plane from stalling or otherwise exiting controlled flight. Because the pilot was able to start the APU to provide electrical power, the plane remained in the "normal law" mode where these protections were available. This limits the control the pilot has in order to protect the plane, in the sense that the plane will override pilot inputs to avoid dangerous situations.

Section 2.7.2 discusses the impact of these protections in this case.

The airplane’s airspeed in the last 150 feet of the descent was low enough to activate the alpha-protection mode of the airplane’s fly-by-wire envelope protection features...

Because of these features, the airplane could not reach the maximum AOA attainable in pitch normal law for the airplane weight and configuration; however, the airplane did provide maximum performance for the weight and configuration at that time...

The flight envelope protections allowed the captain to pull full aft on the sidestick without the risk of stalling the airplane.

An interesting point in the report is that Airbus certified the plane to be able to land on the water intact under certain conditions. Here is how the actual conditions compared to the certified conditions.

Section 1.6.7

enter image description here

The report mentions that it would be extremely difficult to meet all of these requirements in an airplane with no power. The values that are higher, notably the mass and descent rate, are factors in the damage the airplane received.

Improve this answer
$\endgroup$
2
  • 5
    $\begingroup$ As @Lnafziger mentioned, the amount of "nannying" that an Airbus does compared to a Boeing is debated among pilots. Airbus, for example, won't let you jerk the controls to the point of possibly losing control or bending metal. Boeing will let you, so that if you come out of a cloud and see you're going to collide with another plane in 3 seconds, you can pop a few rivets but avoid a mid-air. Boeing also gives a lot more tactile feedback on the controls and involves the pilot more heavily, which can have its advantages (the downside is more routine workload). $\endgroup$
    – Phil Perry
    Commented Mar 25, 2014 at 22:25
  • 10
    $\begingroup$ Examples of how the Airbus system works well are in this ditching case (pilot wants best nose up performance, doesn't need to judge manually) and the incident here, where the plane prevented an inadvertent nose down from damaging the plane. $\endgroup$
    – fooot
    Commented Mar 25, 2014 at 22:32
4
$\begingroup$

The autopilot and autothrottle were both disengaged and, thanks to the quick thinking of the Pilot Flying to activate the Auxiliary Power Unit (APU), the aircraft stayed in Normal Law. This assisted when ditching due to the transition at 50ft to Flare Mode that causes a pitch down attitude allowing the pilot to pull back with a constant pressure on his side stick to cause the plane to flare for landing.

Improve this answer
$\endgroup$
3
  • 3
    $\begingroup$ We're looking for long answers that provide some explanation and context. Don't just give a one-line answer; explain why your answer is right, ideally with citations. Answers that don't include explanations may be removed. $\endgroup$
    – Federico
    Commented Apr 12, 2015 at 11:40
  • $\begingroup$ You should improve your answer by adding reeferences and explaninig what your answer add to the rest of the other answers $\endgroup$
    – Manu H
    Commented Sep 27, 2016 at 12:06
  • 1
    $\begingroup$ "technically" the best answer so far, and the only one to correctly point out that A/P was off. Guys, you cannot fly manually with A/P on. People all over this page have mistaken FBW protections and laws with the Autopilot $\endgroup$
    – Radu094
    Commented Sep 29, 2016 at 11:40
1
$\begingroup$

There is not much training for situations like that because they are very rare and the simulators cannot teach accurately what to expect when a plane touches down on water.

The captain in this situation got almost everything right for a water landing, as he kept the nose up and wings level, he let the tail hit the water first slowing the plane down enough so it survived the impact.

I'm not sure autopilot played much role in this if any, because there was no runway length and reverse thrust to concider.

Improve this answer
$\endgroup$
6
  • 2
    $\begingroup$ I disagree that there's "not much training for situations like this" - ditching is definitely a commonly practised procedure. $\endgroup$
    – Danny Beckett
    Commented Mar 25, 2014 at 14:39
  • 10
    $\begingroup$ From the Air Crash Investigation episode on this accident @ about 11:25 -- "Investigators Soon Learned that none of the Major Airlines Teach Pilots how to Land On Water. Training for Ditching in water is very difficult, we don't have the models to accurately simulate what a plane will do when it touches down on water, Given the rarity of this type of event it will be difficult to justify training for training pilots for this type of event" $\endgroup$
    – Tasos
    Commented Mar 25, 2014 at 14:41
  • $\begingroup$ Thanks for that! It sounds like I stand corrected. Does anyone else know about this? $\endgroup$
    – Danny Beckett
    Commented Mar 25, 2014 at 15:16
  • $\begingroup$ Your thinking about "Ditching" and you are correct, there are procedures for that, and for "Water Ditching" their is some standard procedures pilots learn to follow. There must some Knowledge as to what to do in situations like that and from historical experience. But Learning how to do that its very difficult. $\endgroup$
    – Tasos
    Commented Mar 25, 2014 at 15:25
  • 10
    $\begingroup$ FWIW, in my 10 years of taking 747 simulator check rides, ditching was regularly practiced. There was a checklist for ditching. It included recommended touchdown configuration, speed, pitch attitude, and admonitions for landing parallel to the swells if possible. There was a lot of work for the flight engineer (3 man cockpit), a lot of setup including making sure the outflow valves were closed and the like. As I remember, the recommended pitch attitude for the 747 was 5 degrees nose up. I can't remember the recommended flap setting. $\endgroup$
    – Terry
    Commented Mar 28, 2014 at 8:28

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .