YYZatcboy
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Salt Water Corrosion

Fri Mar 11, 2011 7:56 pm

My question stems from todays horrific disaster in Japan. I'm sure we've all seen the images of the airport that got flooded by the tsunami. As of yet I can't see any aircraft at the airport with the exception of the three GA aircraft in other pictures.


At what point would salt water from the wave cause enough damage or suspected damage to the airframe for an aircraft to be a write off. If a 737 say was on that gate and was not otherwise damaged from the wave, would the salt water on it's components be a concern?

Thoughts?
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tdscanuck
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RE: Salt Water Corrosion

Sat Mar 12, 2011 5:46 am

Quoting YYZatcboy (Thread starter):
At what point would salt water from the wave cause enough damage or suspected damage to the airframe for an aircraft to be a write off.

Assuming that no structural damage occurred because of current/debris, you'd have to get water actually inside the fuselage (i.e. an open door/vent/etc.) to start to do that kind of damage. The engines might be ruined, but those can be replaced. Most of the bilge is pretty water-tolerant (it's a bilge, afterall) in the shortterm. If you got salt water in there and let it sit for days or weeks you'd be in trouble...if they get to it quickly and clean it out, there shouldn't be lasting structural damage. If the water gets deep enough you'll have a lot of pissed off avionics but, again, those can be replaced with relatively little effort.

Quoting YYZatcboy (Thread starter):
If a 737 say was on that gate and was not otherwise damaged from the wave, would the salt water on it's components be a concern?

Outside, generally not. Those components are all exposed to pretty considerable amounts of water anyway so, assuming you didn't let it sit, you should be OK. I'd pull the engines, replace the brakes and wheels, and do full lubrication and inspection of everything, but it should survive. If water got inside, much more inspection and I'd expect to have a lot of electrical problems (corroded pins) for the foreseeable future.

Tom.
 
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kanban
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RE: Salt Water Corrosion

Sat Mar 12, 2011 6:51 am

a couple years ago we dumped a restored 307 in the bay (salt water) .. it took 15 months to put back to flying shape to be delivered to the Aero Space Museum and never to fly again...      
 
unattendedbag
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RE: Salt Water Corrosion

Sat Mar 12, 2011 11:25 am

Quoting kanban (Reply 2):
a couple years ago we dumped a restored 307 in the bay (salt water)

why?
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YYZatcboy
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RE: Salt Water Corrosion

Sat Mar 12, 2011 12:58 pm

I'm figuring a 737 sitting at a gate would probably be being serviced, AKA baggage holds open, APU possibly running, AC vents open, possibly A and E bay exposed. I don't think the pitot tubes and other sensors are quite low enough on the 737 to be hit by the 10 foot wave, but those could concieveably be splashed.

Thanks for the reply Tom. I'm a dispatcher not a mechanic or hydraulic engineer, so this is very interesting to me.

Cheers
Joe
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tdscanuck
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RE: Salt Water Corrosion

Sat Mar 12, 2011 2:44 pm

Quoting unattendedbag (Reply 3):
Quoting kanban (Reply 2):
a couple years ago we dumped a restored 307 in the bay (salt water)

why?

They ran out of gas.
http://www.seattlepi.com/local/64484_main29.shtml

Tom.
 
jetstar
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RE: Salt Water Corrosion

Sat Mar 12, 2011 10:22 pm

In 1968, A Japan Airlines DC-8 landed in San Francisco Bay, 2 and1/2 miles short of the runway, the airplane sat in the bay for 55 hours before being lifted onto a barge and taken to a United Airlines hanger where it was cleaned and repaired and returned to service.

The airplane remained with JAL for another 14 years and was then eventually operated by Airborne Express from 1987 until it was removed from service and scrapped in 2001.

So this airplane spent another 33 years in service after a 55 hour salt water bath.

JetStar
 
Viscount724
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RE: Salt Water Corrosion

Sun Mar 13, 2011 12:09 am

Quoting jetstar (Reply 6):
In 1968, A Japan Airlines DC-8 landed in San Francisco Bay, 2 and1/2 miles short of the runway, the airplane sat in the bay for 55 hours before being lifted onto a barge and taken to a United Airlines hangar where it was cleaned and repaired and returned to service.

Not even any injuries to the 107 passengers and crew. A few photos:

http://www.dc-8jet.com/Images/jal-dc862-in-sf-bay1.jpg



Aircraft involved 4 months before (only 2 months old then) and 14 years after the accident.


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Starlionblue
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RE: Salt Water Corrosion

Sun Mar 13, 2011 12:23 am

Side question on that DC-8. Just like the Hudson river Airbus, it is sitting bum down in the water. Is this coincidence or does the design of the aircraft contribute to the aft part being lower?
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Viscount724
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RE: Salt Water Corrosion

Sun Mar 13, 2011 12:29 am

Quoting Starlionblue (Reply 8):
Side question on that DC-8. Just like the Hudson river Airbus, it is sitting bum down in the water. Is this coincidence or does the design of the aircraft contribute to the aft part being lower?

One major difference with the JL water landing was that the water was only about 7 or 8 feet deep so the aircraft came to rest sitting on its landing gear (at least the main gear). That's what prevented it from sinking.
 
roseflyer
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RE: Salt Water Corrosion

Sun Mar 13, 2011 12:42 am

Almost all components outside the pressure vessel are tested for salt spray and corrosion. That means components in the wheel wells, wings, engines, struts, etc. They can take it some salt water damage. However if it gets inside the fuselage it will do some damage as those components are not designed to take the salt water.
If you have never designed an airplane part before, let the real designers do the work!
 
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kanban
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RE: Salt Water Corrosion

Sun Mar 13, 2011 5:35 am

Quoting Starlionblue (Reply 8):
Side question on that DC-8. Just like the Hudson river Airbus, it is sitting bum down in the water.



I think that has to do with the wings acting as floatation devices and the horiz stabs to some degree but since they're higher than the wings, the arse end settles a bit deeper. (and I could be totally wrong)
 
tdscanuck
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RE: Salt Water Corrosion

Sun Mar 13, 2011 9:36 pm

Quoting Starlionblue (Reply 8):
Side question on that DC-8. Just like the Hudson river Airbus, it is sitting bum down in the water. Is this coincidence or does the design of the aircraft contribute to the aft part being lower?

The wings really want to float and their center of buoyancy is ahead of the center of gravity, so the airplane pitches up until enough of the tail gets into the water to balance it out.

Tom.
 
sfotom
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RE: Salt Water Corrosion

Sun Mar 13, 2011 11:13 pm

Quoting Starlionblue (Reply 8):
Side question on that DC-8. Just like the Hudson river Airbus, it is sitting bum down in the water. Is this coincidence or does the design of the aircraft contribute to the aft part being lower?

I used to know some of the people that worked on the recovery of this aircraft. They told me that the nose gear was stuck in the mud and the aircraft would "weather vane" on it as the tide came in and out.

Tom

[Edited 2011-03-13 16:48:11]

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