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PPVRA
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Aircraft And Earthquakes

Sun Feb 28, 2010 11:37 pm

The recent events in Chile made me wonder if there are any procedures/checks to made to aircraft after such a strong earthquake hits an airport? I have never been through a strong earthquake, and the one or two weak ones never woke me up, so I really have no idea if this type of thing can be sufficient to cause damages to aircraft on the ground (aside from huge crevasse opening up and swallowing the plane). On the other hand, these planes are pretty strong, and I'm sure their suspensions take a lot of the shock. Aside from any mechanical issues, I had particularly in mind the wing flexing down while it is fully "relaxed" which is not something natural.

So, just a stationary turbulence with little to no effect, or more to it?

Thanks,
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fr8mech
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RE: Aircraft And Earthquakes

Mon Mar 01, 2010 2:06 am

I didn't find an earthquake inspection in our various AMM's. But, I would guess, depending on severity of the quake, caution may have maintenance perform a high side-load inspection. I would assume the aircraft may experience side loads in excess of the normal limits.
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Okie
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RE: Aircraft And Earthquakes

Mon Mar 01, 2010 3:11 am

I think Airbus generates its own inspection report from g forces from hard landings. One would assume if the plane was powered up that it would generate and inspection report if needed. I just do not know if all the proper systems would be on while sitting on the tarmac or at the gate to have the plane generate a report.


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Starlionblue
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RE: Aircraft And Earthquakes

Mon Mar 01, 2010 4:09 am

I get the feeling that any forces experienced in earthquakes would be less than what happens during turbulence and landing. I could be wrong.
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UAL747
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RE: Aircraft And Earthquakes

Mon Mar 01, 2010 4:22 am

in the 1989 SFO earthquake, I had a friend flying from SFO to DEN (I think on a DC-10). She said they felt the aircraft shake, as they were pushing back. She speculated that "The pilot must have pushed back the plane while the jetway was still connected," which I doubt would even feel like that, not to mention ground crew would see the jetway.

At any rate, I have heavy doubts any check would be needed. Think of all the hard landings every aircraft makes multiple times a day and how much weight and stress is put on the aircraft. The aircraft is also built to handle these stresses as well as heavy heavy vibrations and fluctuations in the surface shape of the aircraft.

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LAXintl
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RE: Aircraft And Earthquakes

Mon Mar 01, 2010 4:36 am

I have never heard of an earthquake check.
Frankly even the worst quake is not going to be much worse then the shaking, rolling and swaying an aircraft experiences when taxiing, especially at an airport with crappy taxiways like JFK.
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lotsamiles
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RE: Aircraft And Earthquakes

Mon Mar 01, 2010 4:33 pm

Per the California Geological Survey:

"During an earthquake, the forces vary a lot and keep changing, back and forth and side to side. These forces, if they’re strong enough, can damage structures unless the structures have been specially designed. The largest earthquake forces that have been measured are about 1 to 2 g; most earthquakes have much lower forces, but those forces can still damage many structures."

I suspect with an 8.8 earthquake the g forces were above 1g at the epicenter. However, with the distance to SCL the forces there would be in the 0.1 to 0.3g range as may be typical for a magnitude 6 earthquake (taken from some quick Google search results from academia).

I can't find them now but from my memory I think the vertical load limit on most airliners is 1.0g and the lateral load limit is 0.5g.

If so, then a strong earthquake underneath a sitting airliner may exceed some load limits and I would think that should necessitate inspections.
 
tdscanuck
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RE: Aircraft And Earthquakes

Mon Mar 01, 2010 5:34 pm

Quoting lotsamiles (Reply 6):
I can't find them now but from my memory I think the vertical load limit on most airliners is 1.0g and the lateral load limit is 0.5g.

3g up, 6g down, 9g forward, and 1.5g lateral.

Based on that, and the numbers you posted, an earthquake no threat to the airplane.

Tom.
 
lotsamiles
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RE: Aircraft And Earthquakes

Mon Mar 01, 2010 5:57 pm

Quoting tdscanuck (Reply 7):
3g up, 6g down, 9g forward, and 1.5g lateral.

Based on that, and the numbers you posted, an earthquake no threat to the airplane.

Tom, thanks for the references. I should know better than to trust my quickly aging memory. However, thinking more about this the ground handling or landing loads are probably a better guide. FAR part 25 section 495 gives a 0.5g lateral load requirement for aircraft turning on the ground. Section 485 gives 0.8g outward or 0.6g inward in combination with 50% of the max vertical ground reaction for landing gear.

Perhaps the flying aircraft can take more than any anticipated earthquake loads, but what about an aircraft standing on the gear?
 
tdscanuck
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RE: Aircraft And Earthquakes

Mon Mar 01, 2010 7:13 pm

Quoting lotsamiles (Reply 8):
FAR part 25 section 495 gives a 0.5g lateral load requirement for aircraft turning on the ground. Section 485 gives 0.8g outward or 0.6g inward in combination with 50% of the max vertical ground reaction for landing gear.

Perhaps the flying aircraft can take more than any anticipated earthquake loads, but what about an aircraft standing on the gear?

Whoops...you're absolutely right. The figure I gave are flight loads, which is a whole different ballgame because of how the loads are applied.

Tom.
 
bassbonebobo
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RE: Aircraft And Earthquakes

Mon Mar 01, 2010 9:43 pm

Although an inspection of the landing gear couldn't hurt I doubt the loads experienced as a result of the shaking would do any damage to the aircraft. I would be much more concerned about the aircraft being damaged by falling debris from surrounding structures (hangars, terminals, jetways, lighting structures, etc.).
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DocLightning
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RE: Aircraft And Earthquakes

Mon Mar 01, 2010 10:29 pm

Quoting bassbonebobo (Reply 10):
Although an inspection of the landing gear couldn't hurt I doubt the loads experienced as a result of the shaking would do any damage to the aircraft. I would be much more concerned about the aircraft being damaged by falling debris from surrounding structures (hangars, terminals, jetways, lighting structures, etc.).

The other thing is that cracks can open up in the pavement that might put stresses on/puncture the tires. It's probably worth a quick inspection if there's any damage to the tarmac, I'd imagine.
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lowrider
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RE: Aircraft And Earthquakes

Mon Mar 01, 2010 11:10 pm

The only thing I haven't seen mentioned is the potential damage to gyros and IRUs. Depending on thier status at the time of the quake, I would think there is the possibility for some damage.
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prebennorholm
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RE: Aircraft And Earthquakes

Tue Mar 02, 2010 3:00 am

Depending on the circumstances you may want to check for collision damage made by stairs, catering truck, baggage belts etc. which were at work on the plane.

Otherwise, the max vertical speed landing tests and max sideslip tests, which are done for certification, are much worse torture than anything an eartquake can do.

Except if the tarmac is totally destroyed. An 8.8 Richter earthquake, like outside Chile the other day, right at the airport, would create 10 - 20 feet high "waves" on the tarmac, and the runway). It will last a few days (weeks, months, even years) before the next plane takes off from that airport again. A plane taking off or landing, while the runway is being destroyed, that will of course create a disaster.
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L-188
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RE: Aircraft And Earthquakes

Tue Mar 02, 2010 7:19 am

I rode out a 6.6 quake at Adak Island about 97.

The plane rocked pretty good.

I think the most you have to worry about is if you cause skin damage because a piece of GSE is parked up against the side of the aircraft.
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Aaron747
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RE: Aircraft And Earthquakes

Tue Mar 02, 2010 8:47 am

Quoting LAXintl (Reply 5):
Frankly even the worst quake is not going to be much worse then the shaking, rolling and swaying an aircraft experiences when taxiing, especially at an airport with crappy taxiways like JFK.

LOL.

This about the best answer to this question one can get.
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Viscount724
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RE: Aircraft And Earthquakes

Wed Mar 03, 2010 10:04 pm

Quoting prebennorholm (Reply 13):
Except if the tarmac is totally destroyed. An 8.8 Richter earthquake, like outside Chile the other day, right at the airport, would create 10 - 20 feet high "waves" on the tarmac, and the runway). It will last a few days (weeks, months, even years) before the next plane takes off from that airport again.

Photo of damage to the 5100 ft. runway at Northway, Alaska, about 250 nm northeast of ANC near the Canadian border, following a magnitude 7.9 earthquake in the interior of Alaska on November 3, 2002.



Another related item with more photos.
http://www.aopa.org/whatsnew/newsitems/2002/02-4-082x.html

Control tower at ANC (7 storeys, reinforced concrete) that collapsed in the magnitude 9.2 Alaska quake on March 27, 1964, the most powerful every recorded in North America and 3rd strongest in the world at the time. The one person in the tower was killed. If memory correct, the runways survived intact.

http://libraryphoto.cr.usgs.gov/htmllib/batch07/batch07j/batch07z/aeq00027.jpg
 
lotsamiles
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RE: Aircraft And Earthquakes

Thu Mar 04, 2010 7:16 pm

engines in shop after Chile 8.8 quake


I guess engine pedistals are not up the the task.
 
PPVRA
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RE: Aircraft And Earthquakes

Thu Mar 04, 2010 8:22 pm

Quoting lotsamiles (Reply 17):
I guess engine pedistals are not up the the task.

Could you please attempt to post that again? I can't see it. Sounds like a cool picture  
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lotsamiles
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RE: Aircraft And Earthquakes

Thu Mar 04, 2010 8:49 pm

engine in shop after strong earthquake
 
PPVRA
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RE: Aircraft And Earthquakes

Thu Mar 04, 2010 11:17 pm

Quoting lotsamiles (Reply 19):

Thanks a lot!

Looks like an expensive mistake that could have been avoided. And good thing it happened when no one was around working on them. Can these engines be re-used?
"If goods do not cross borders, soldiers will" - Frederic Bastiat
 
lotsamiles
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RE: Aircraft And Earthquakes

Fri Mar 05, 2010 12:44 am

Quoting PPVRA (Reply 20):
Can these engines be re-used?

I think with a special workscope recommended by the OEM they could be used again. All bearings would need to be replaced, as well a careful inspection of the cases for cracks and loss of dimensions is needed. Further inspections are required for evidence of contact on rotating parts, etc. I believe the OEM's have ready made workscopes for dropped engines.

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