bri2k1
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B777 Main Gear Steering Inop - WX?

Tue Dec 13, 2005 1:30 pm

On a recent flight from hell, er I mean ORD, to DEN, on a UA 772, I heard a strange comment on channel 9. We pushed back, deiced, and taxiied out, but due to substantial delays, we had to return to the gate for deicing. A gate was not available, and the holding areas were full, so we just stopped on a small connector taxiway. The pilots never shut the engines down, but we were there for almost 3 hours. When we finally got to move again, the captian told the ground controller "We just lost the main gear steering, so we can't make that next turn. We'll have to go down farther." I was wondering, could the loss of the main gear steering have been due to snow/ice accumulation? If not, then what? Maintenance never checked out the plane, so I wouldn't think it was a MEL item, and we eventually (9 hours later) took off on the same plane. How does this system work, and what are its usual failure and recovery modes? Thanks!
Position and hold
 
777wt
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RE: B777 Main Gear Steering Inop - WX?

Tue Dec 13, 2005 2:43 pm

I wouldn't think it would've been from the snow/ice accumulation. The main gear steering allows the rear 2 wheels on each mains to turn for tight turns and to ease up the stress on the main gear.
Failure mode would prob just lock the gear in line with the other wheels. I wouldn't know, a 777 tech could explain better.

Sounded like UA burned up alot of fuel in this case.
 
cdfmxtech
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RE: B777 Main Gear Steering Inop - WX?

Tue Dec 13, 2005 5:11 pm

Main gear Steering uses inputs from the Nose Gear steering system to provide steering for the aft main gear wheels. The 777 monitors itself and if it determines different levels of faults that may exist in the system. The level of message will determine whether the crew can go or not. For instance, if the wheels were not locked and centered, then an advisory message will let them know about it. If they were to advance the throttles to take off position, then a higher level WARNING message would alert them.
If an actuator failed in the closed position, it would be a status message, and returning to the gate might not be necessary.

The Main gear Steering system is placardable, but maintenance must ensure the system is locked. The lockout is done on the gear.

There is a way to access a display in the flightdeck which will show the position of the MGS steering system. Not sure if it's on the regular pilot synoptinc pages ot on maintenance pages. Don't work the airplane often enoguh to remmeber that.
 
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HAWK21M
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RE: B777 Main Gear Steering Inop - WX?

Wed Dec 14, 2005 5:04 am

Quoting Bri2k1 (Thread starter):
Maintenance never checked out the plane, so I wouldn't think it was a MEL item, and we eventually (9 hours later) took off on the same plane.

Wouldn't an MEL entry necessatite a Paperwork Entry.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
Tristarsteve
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RE: B777 Main Gear Steering Inop - WX?

Wed Dec 14, 2005 6:48 am

Quoting HAWK21M (Reply 4):
Wouldn't an MEL entry necessatite a Paperwork Entry

In my airline, once the aircraft starts to move under its own power then the MEL does not apply. If the crew get a message they can decide to look in the MEL to see what it says, then decide to take off if no maint action is required.
 
bri2k1
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RE: B777 Main Gear Steering Inop - WX?

Wed Dec 14, 2005 7:40 am

Quoting Tristarsteve (Reply 5):
once the aircraft starts to move under its own power

That's interesting. I don't know what would have applied here. We did return to the gate for refueling, but I could clearly see the aircraft door from where I sat, and no crew member left the plane, nor did a maintenance person board the plane. We eventually pushed back, de-iced again, and took off. I heard no other mention of the MLG steering on the radio (although I could only hear communications with ramp metering and ground, and not the company frequencies.)
Position and hold
 
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HAWK21M
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RE: B777 Main Gear Steering Inop - WX?

Wed Dec 14, 2005 3:10 pm

Quoting Tristarsteve (Reply 5):
In my airline, once the aircraft starts to move under its own power then the MEL does not apply. If the crew get a message they can decide to look in the MEL to see what it says, then decide to take off if no maint action is required

Interesting.Is this SOP in tune with FAA/JAA/CAA of your Countrys regulatory board.
Out here its Different.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
Matt72033
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RE: B777 Main Gear Steering Inop - WX?

Wed Dec 14, 2005 4:05 pm

Quoting Bri2k1 (Reply 6):
nor did a maintenance person board the plane.

surely if fuel was uplifted then an entry into the tech log must be made, also here we have to deliver the fuel card to the captain so he can make his calculations and decide he's happy with what he has!
 
Sabenaboy
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RE: B777 Main Gear Steering Inop - WX?

Wed Dec 14, 2005 4:56 pm

Quoting HAWK21M (Reply 7):
Quoting Tristarsteve (Reply 5):
In my airline, once the aircraft starts to move under its own power then the MEL does not apply. If the crew get a message they can decide to look in the MEL to see what it says, then decide to take off if no maint action is required

Interesting.Is this SOP in tune with FAA/JAA/CAA of your Countrys regulatory board.
Out here its Different.
regds
MEL

Hi, this rule is also applicable in my airline. Once we started taxi, we are not obliged anymore to take out the MEL if a failure occurs. Of course, the crew can always decide to do so, if in doubt about a certain failure. Even if the MEL would say that the failure is a no go-item, the crew can still legally decide to continue the flight. For instance, if the Flight date (DFDR) AND the voice recorder (CVR) fail after the taxi has started, the captain may decide to continue the flight. If the failure had occurred during the pushback, a repair would have been necessary before takeoff.

And yes,Hawk, this SOP is in tune with the rules in my country and JAR.

Regards,
Sabenaboy
 
charliecossie
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RE: B777 Main Gear Steering Inop - WX?

Wed Dec 14, 2005 5:48 pm

Quoting Matt72033 (Reply 8):
surely if fuel was uplifted then an entry into the tech log must be made,

United don't have a "tech log". Neither do they have an MEL on the aircraft.

Quoting HAWK21M (Reply 7):
Out here its Different.

No surprise there then.

Quoting Bri2k1 (Thread starter):
Maintenance never checked out the plane, so I wouldn't think it was a MEL item,

Very common that a 777 fixes itself. IOW, status messages come and go regularly. Main gear steering is common, is MELable but requires a maintenance procedure. However, it regularly goes away (the message, that is) all on it's own. No message, nuthin' to fix.
 
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HAWK21M
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RE: B777 Main Gear Steering Inop - WX?

Wed Dec 14, 2005 10:30 pm

Quoting Charliecossie (Reply 10):
United don't have a "tech log". Neither do they have an MEL on the aircraft.

Pls elaborate Charlie.
Isn't MEL a part of the On board Docs.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
charliecossie
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RE: B777 Main Gear Steering Inop - WX?

Wed Dec 14, 2005 11:09 pm

There is no "tech log" on the aircraft. It's totally computerised.
The only paperwork normally in the cockpit is the Maintenance Release Document which details defects recorded on the previous sector and the action taken, open MEL items and a few other things. The MRD is usually transmitted to the aircraft via ACARS. There is a (never used) paper backup system in case the computer system dies but it's never needed in reality.
Defects are transmitted (via ACARS) by the crew or the CMC (certain status messages). If the defect is a status message that self-erases, the defect disappears from the online tech log automatically.
As there's no tech log, fuel figures cannot be entered into it.
United use a computer printed fuel sheet. Loading fuel is not an engineering function. It's carried out by ramp staff who bring the completed fuel sheet to the cockpit.
There is no MEL on a United 747 or 777. Any EICAS/status messages/defects seen by the crew are transmitted back to the online tech log. If a status message occurs during, for example, taxi to the runway, the crew either call local engineering on VHF or Systems Aircraft Maintenance Control (aka SAM-C) via satcom or ACARS. If SAM says it's a go-er, they go and SAM makes the online tech log entry and defers it. The aircraft receives (again via ACARS) a copy of the MEL placard.
Seems complicated. Is complicated. Works well.
 
Matt72033
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RE: B777 Main Gear Steering Inop - WX?

Wed Dec 14, 2005 11:23 pm

sounds good! paperworks such a huge part of the job here....anything that can cut it down a bit has to be good.

so if there's no paper tech log, does the licenced engineer have to sign anything to release the aircraft? does the captain sign anything to accept the aircraft? or is this all done on the MRD?
 
charliecossie
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RE: B777 Main Gear Steering Inop - WX?

Wed Dec 14, 2005 11:28 pm

Quoting Matt72033 (Reply 13):
does the licenced engineer have to sign anything to release the aircraft?

Electronic "signature" on the MRD. If you aren't qualified, you can't release it.

Quoting Matt72033 (Reply 13):
does the captain sign anything to accept the aircraft?

No, not required.
 
Matt72033
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RE: B777 Main Gear Steering Inop - WX?

Wed Dec 14, 2005 11:58 pm

looks like its the way forward...hopefully it'll be implemented here soon!
 
CX Flyboy
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RE: B777 Main Gear Steering Inop - WX?

Thu Dec 15, 2005 12:44 am

Quoting Charliecossie (Reply 10):
Very common that a 777 fixes itself. IOW, status messages come and go regularly. Main gear steering is common, is MELable but requires a maintenance procedure. However, it regularly goes away (the message, that is) all on it's own. No message, nuthin' to fix

In my years on the 777 I cannot say that I have ever seen a Main Gear Steering message, although you are correct in that sometimes we do get messages which appear and then vanish sometime later, although I would not say that it is regular. Maybe once every 30 flights or so with our fleet. More common is the status message which the engineers reset and then the system passes a check and it is declared serviceable.
 
bri2k1
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RE: B777 Main Gear Steering Inop - WX?

Thu Dec 15, 2005 1:14 am

Quoting CX flyboy (Reply 16):
a Main Gear Steering message

I wasn't privy to the actual message, of course. I simply overheard the captain tell ground control "we just lost our main gear steering" and, as a result, we couldn't make the very next 90-degree turn, we had to taxi down a ways.

It's interesting that the message would come and go. I assume while it was completely safe, the designers didn't intend for the plane to sit, fully loaded, both engines turning, for 9 hours, in an ice storm, every single flight. That's why I wondered if the steering issue could have been related to the weather. So, I guess I'll never know if it was fixed or not, but I do know we eventually left on the same plane, and I never saw anyone fixing anything mechanical. Thanks for all the responses!
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cdfmxtech
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RE: B777 Main Gear Steering Inop - WX?

Sat Dec 17, 2005 6:14 am

Quoting Bri2k1 (Reply 17):
I wasn't privy to the actual message, of course. I simply overheard the captain tell ground control "we just lost our main gear steering" and, as a result, we couldn't make the very next 90-degree turn, we had to taxi down a ways.

yes, the only way the crew would have knowwn about the loss of MGS is a message. There are no Annunciators for this condition on the 777, just the message.
 
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Starlionblue
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RE: B777 Main Gear Steering Inop - WX?

Fri Dec 30, 2005 8:28 am

Quoting CX flyboy (Reply 16):
although you are correct in that sometimes we do get messages which appear and then vanish sometime later

Very comforting Big grin
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
larspl
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RE: B777 Main Gear Steering Inop - WX?

Sun Jan 01, 2006 8:58 pm

Quoting Bri2k1 (Reply 6):
We did return to the gate for refueling, but I could clearly see the aircraft door from where I sat, and no crew member left the plane, nor did a maintenance person board the plane. We eventually pushed back, de-iced again, and took off. I heard no other mention of the MLG steering on the radio (although I could only hear communications with ramp metering and ground, and not the company frequencies.)

on many a/c types there are more ways to enter and exit the aircraft than the 'normal' doors. i.e.: the A330 has a hatch in de cockpit floor into the bay and another hatch into the 'outside'.



i'm not implying that this happened on your flight, i'm not even sure if it is possible on the 777. Just a reminder that there is so much you don't see in the cabin happening in aviation



I would guess that forward or e/e access is located in the cockpit, and that under the left seat is some sort of hatch.
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charliecossie
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RE: B777 Main Gear Steering Inop - WX?

Sun Jan 01, 2006 10:14 pm

Quoting Larspl (Reply 23):
I would guess that forward or e/e access is located in the cockpit, and that under the left seat is some sort of hatch.

Don't guess, you'd be wrong.
 
larspl
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RE: B777 Main Gear Steering Inop - WX?

Mon Jan 02, 2006 2:40 am

Quoting Charliecossie (Reply 24):
Don't guess, you'd be wrong.

alright  Smile

can you tell me where to they do refer?
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charliecossie
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RE: B777 Main Gear Steering Inop - WX?

Mon Jan 02, 2006 4:37 am

On the triple, the "lower 41" hatch (e&e bay hatch) is just inside door 1 left.
On United, the latch handle (for the hatch) is secured, from above, with a very large screw.
 
Matt72033
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RE: B777 Main Gear Steering Inop - WX?

Mon Jan 02, 2006 4:49 am

Quoting Charliecossie (Reply 28):
On the triple, the "lower 41" hatch (e&e bay hatch) is just inside door 1 left.
On United, the latch handle (for the hatch) is secured, from above, with a very large screw.

anyway out through the nose gear bay?
Edit: or into the cargo hold?

[Edited 2006-01-01 20:53:37]
 
larspl
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RE: B777 Main Gear Steering Inop - WX?

Mon Jan 02, 2006 4:54 am

Charliecossie, thanks!

and do you know where and what the 'forward access' is?
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HAWK21M
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RE: B777 Main Gear Steering Inop - WX?

Mon Jan 02, 2006 3:17 pm

Quoting Charliecossie (Reply 22):
On United, the latch handle (for the hatch) is secured, from above, with a very large screw

Any Pic/Sketch.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
charliecossie
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RE: B777 Main Gear Steering Inop - WX?

Mon Jan 02, 2006 7:35 pm

Quoting Larspl (Reply 24):
and do you know where and what the 'forward access' is?

There's a small electronics bay fwd of the nose gear bay.
Not much up there.

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