Premature touchdown

2007-11-22

in Daily updates

The story of what happened to Japan Air flight #2 on November 22nd, 1968 is a strange one. The pilot brought the plane down in a normal landing procedure, though he managed to land the plane several miles ahead of the runway, in San Francisco Bay.

It was my belief, previously, that everybody died on commercial airliners that landed in the sea. I had heard that the drag from the engines going through the water decelerates everyone so violently that they never get to find out how good (or poor) the flotation of their seat cushion really is. Not only did these passengers not die, but the plane was in good enough shape to repair and use again.

Two factors make me think this was less bad then an emergency water landing. For one, the water wasn’t deeper than the plane. Apparently, “the rising water stopped just short of the bottom sills of the cabin doors.” That might mean there was less sudden change in velocity. For another, the plane was making a normal powered landing. The pilot apparently thought he was about to touch down on tarmac. Pilots landing a plane in water with no engine power, or limited engine power, (the only reason you would land the plane there) might have a lot less control of their velocity and the craft’s orientation at the time of impact.

To his credit, the pilot made no excuses for the crash – accepting the blame personally. In honour of Captain Kohei Asoh, this tactic is now called the Asoh Defence.

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{ 12 comments… read them below or add one }

Milan November 22, 2007 at 6:10 pm

In December 2002, The Economist quoted an expert as claiming that “No large airliner has ever made an emergency landing on water” in an article that goes on to charge, “So the life jackets … have little purpose other than to make passengers feel better.” This claim was repeated in The Economist in September 2006 in an article which claimed that “in the history of aviation the number of wide-bodied aircraft that have made successful landings on water is zero.” This is correct, but incomplete (the one wide-bodied landing was a case of a 767 leaving a runway).

From the Wikipedia entry Water landing

Milan November 22, 2007 at 6:14 pm

This previous blog entry quotes one of those Economist articles:

Flight safety

Milan November 22, 2007 at 6:25 pm

NATIONAL TRANSPORTATION SAFETY BOARD
AIRCRAFT ACCIDENT REPORT (PDF)
JAPAN AIRLINES CO., LTD.
DC-8-62, JA 8032
SAN FRANCISCO BAY
SAN FRANCISCO, CALIFORNIA
NOVEMBER 22, 1968

Milan November 22, 2007 at 7:15 pm

Page 19 of the report gives the speed at the time of impact as 125 knots.

Litty November 23, 2007 at 10:16 am

I had heard that the drag from the engines going through the water decelerates everyone so violently that they never get to find out how good (or poor) the flotation of their seat cushion really is.

Not comforting. Do not mention this to the person in the seat beside you during your next flight.

A Wadhamite November 23, 2007 at 6:04 pm

Asoh committed suicide in the end. And he was demoted.

Matt T November 28, 2007 at 11:41 pm

I would take issue with the ‘no aircraft has ever made an emergency landing on water’ factoid. While I can’t think of any where the airplane floated serenely on the water’s surface as is depicted on the emergency cards, there are at least two water landings that spring to mind, and both at least partially survivable:

First, an Ethopian 767 that was hijacked and ran out of fuel. The video is of the actual crash. Some died, but many lived. Aspects that contributed to survivability: Crashing in warm water, crashing just offshore, crashing at a tourist resort with many people to help rescue survivors. Aspects that added to the death toll: Pilots fighting with the hijackers while attempting to land the plane. Notice it does not hit the water level.

Crash video

Second, a Garuda Indonesia 737 experienced a double engine failure due to water ingestion (flying through a severe thunderstorm). Pilots unable to restart engines elected to ditch in the Benjawang Solo River. All but one, a flight attendant, survived. Aspects that contributed to survivability: shallow water.

737 sitting in the river

There are also other instances which, although not exactly ditchings, wound up with an airliner in water.

China airlines 747 at Kai Tak

Scandanavian DC-10

National 727

World Airways DC-10

There are others, too, such as the Air Florida 737 that crashed into a bridge over the Potomac river in washington, and then crashed into the river itself. 5 survived this crash despite the icy water. 6 initially survived. but the last man drown waiting to be rescued.

I’d venture to say that, although a water landing is likely to end in your demise, should you be on that plane, it is far from a certainty.

Milan December 2, 2007 at 10:18 pm

Matt,

Thanks a lot. Rarely do I get comments with so much informative content.

Milan January 16, 2009 at 8:47 am
Tristan January 16, 2009 at 9:48 am

Milan, I think you are probably right to infer that the difference has to do with whether the landing is powered or not. The speed at which a wide bodied airplane executes a powered landing is very slow, in the order of 100mph?

Although, I don’t know why it would not be possible to land this slowly without power (i.e. why it would not simply be more difficult but not impossible.) I will have to check the space shuttle’s landing speed.

Tristan January 16, 2009 at 10:02 am

On an airliner buff website, I found a few people saying things like this about 747’s take off and landing speed:

“181 takeoff speed and flaps 30 landing is 165-121”

Whereas, the landing speed of the shuttle is apparently 219mph. But, that isn’t necessarily down to power alone, it also would have to do with the lower lift to drag ratio required of a plane which must re-enter the atmosphere.

The fact remains that if the plane is traveling slowly enough, the force of the water on the engines will not cause it to buck and roll. I just don’t know what counts as ‘slow enough’ – in my books, 130mph is still pretty fast.

Milan January 16, 2009 at 11:34 am

In order to perform a successful water-landing, here is what I expect you want:

  • Enough forward velocity to generate lift (preventing a rapid vertical deceleration) and maintain useful control surfaces
  • As smooth a profile as possible for moving through the water (preventing a rapid horizontal deceleration).

You can see smooth-bellied ‘flying boat‘ aircraft can do this well. For a normal plane, having the landing gear stowed would probably help.

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