O

N

A

-

C

R

E

W

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F

R

I

E

N

D

S

H

I

P

JACK GOLD ON
THE HUDSON DITCHING

There's been much discussion about US 
Airways Flight 1549 and the extraordinary 
circumstances that befell the Airbus 
A320-200 (N106US) and her compliment of 
150 passengers and 5 crew. At least 
preliminarily, it appears a double bird 
strike disabled each of theCFM56-5B4/P 
engine forcingCaptain C.B. Sullenberger 
III and his First Officer to ditch the 
jetliner in the Hudson River.




As the aircraft was making its 'final 
approach' to the Hudson, the crew was 
preparing the aircraft and its passengers 
for the water landing, including, some 
speculate, by activating the ditching 
system on the A320. The button, cleverly 
labeled 'ditching', is located on the 
'Cabin Press' section of the overhead 
panel shown above.

So what does that infrequently used 
button actually do?

When pressed, it commands the aircraft 
operating system to close the outflow valve, 
emergency ram air inlet, avionics inlet, 
extract valve and flow control valve. In 
addition, it will immediately shutdown the 
cabin fans. The button itself has a guard 
over it to prevent accidental activation. 
The system is available on all A320 family, 
A340/A330 and A380 aircraft.

According to the A320 quick reference guide, 
the ditching procedure calls for Flaps 3 and 
a minimum approach speed of 150 kts. The system 
should be activated at 2000 feet AGL and Airbus 
recommends 11 degrees of pitch at the time of 
touchdown.

The ultimate purpose of the system is to seal 
the aircraft to prevent water from undermining 
the buoyancy of the aircraft to keep it afloat 
in the event that the airframe remains intact 
after impacting the water. Federal Aviation 
RegulationPart 25, Section 801describes the 
safety requirements in the event of a ditching:
(d) It must be shown that, under reasonably 
probable water conditions, the flotation time 
and trim of the airplane will allow the occupants 
to leave the airplane and enter the liferafts 
equired by25.1415. If compliance with this 
provision is shown by buoyancy and trim 
computations, appropriate allowances must be made 
for probable structural damage and leakage. If the 
airplane has fuel tanks (with fuel jettisoning 
provisions) that can reasonably be expected to 
withstand a ditching without leakage, the 
jettisonable volume of fuel may be considered 
as buoyancy volume.

It's not hard to imagine that this live test 
of the 'Ditching' system was a resounding success.
 
Jack Gold
E-mail jascog@aol.com