andz
Posts: 7626
Joined: Mon Feb 16, 2004 7:49 pm

744 Thrust Reverser Positioning Sensors

Mon Jul 10, 2006 5:15 am

I recently flew SAA JNB-LHR on a 744. We taxied out and stopped, then the Captain came on and said there was a technical fault with No 2 thrust reverser sensors and we might need to return to the gate. Laudair sprang to mind and I commented to the F/A sitting opposite me that I was happy to return to the gate for a reverser problem!

Anyway back the gate we went, the Captain was on the P/A explaining that they couldn't determine the position of the reverser which could compromise our take off performance and the aircraft in the air. He explained everything in layman's terms which I thought was pretty good, saying the quickest fix was to lock it out which would take about half an hour.... 20 minutes later we were on our way on a smooth and uneventful flight.

Anyone got any similar stories? Is this a common occurrence? The aircraft was ZS-SAK which has Rolls-Royce RB-211s.


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kaddyuk
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RE: 744 Thrust Reverser Positioning Sensors

Mon Jul 10, 2006 7:39 am

Quoting Andz (Thread starter):
Is this a common occurrence?

Thrust reversers when we have problems with them and we're in a rush are normally locked out. Its not a fix as such, but the aircraft can be dispatched with one thrust reverser Inoperative.

There are many different interlocks that prevent the T/R from being deployed in flight, many of them introduced because of the Lauda Air crash.

Its a fairly simple procedure to lock a T/R out and can be done inside 20 Minutes (I've never really timed myself though).
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n8076u
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RE: 744 Thrust Reverser Positioning Sensors

Mon Jul 10, 2006 11:25 am

Quoting Kaddyuk (Reply 1):
Thrust reversers when we have problems with them and we're in a rush are normally locked out.

I agree, this seems to always happen when you don't have time to actually fix it, and the aircraft is already loaded.  Wink

The P&W powered 747-400s we had at UA weren't particularly troublesome at least compared to the 747 classics we had.

After the Lauda Air crash, the newer 747-400s UA had came with "sync locks" which physically prevented the reverser actuators from turning, should one somehow activate in flight. The 767-300's had these as well. Older 747-400s were retrofitted with this feature at overhaul. Sync lock operation was checked at every "B" check (1000 hrs. between B checks if I remember right). The gaps on the reverser actuator proximity switches were also checked at "B" checks.

Chris
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liedetectors
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RE: 744 Thrust Reverser Positioning Sensors

Sun Jul 16, 2006 3:30 am

Quoting Kaddyuk (Reply 1):
the aircraft can be dispatched with one thrust reverser Inoperative.

Theoretically, you can lock out all the T/Rs and dispatch b/c the T/R is not an essential item.
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n8076u
Posts: 419
Joined: Mon Jun 19, 2006 10:52 am

RE: 744 Thrust Reverser Positioning Sensors

Sun Jul 16, 2006 3:57 am

Quoting Liedetectors (Reply 3):
Theoretically, you can lock out all the T/Rs and dispatch b/c the T/R is not an essential item.

Theoretically, yes. But the reality is that according to the MEL on the 747-400 only one reverser can be inoperative. If you have two inoperative, you're not going anywhere.

Chris
Don't blame me, I don't work here...
 
kaddyuk
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RE: 744 Thrust Reverser Positioning Sensors

Sun Jul 16, 2006 6:30 am

Quoting Liedetectors (Reply 3):
Theoretically, you can lock out all the T/Rs and dispatch b/c the T/R is not an essential item.

Negative, you can lock out both t/r on one engine... however you can't lock out more than one t/r not on the same engine...
Whoever said "laughter is the best medicine" never had Gonorrhea
 
n8076u
Posts: 419
Joined: Mon Jun 19, 2006 10:52 am

RE: 744 Thrust Reverser Positioning Sensors

Sun Jul 16, 2006 8:46 am

Quoting Kaddyuk (Reply 5):
Negative, you can lock out both t/r on one engine... however you can't lock out more than one t/r not on the same engine...

Yes, both reverser halves on one engine must always be locked out together.

Now, it "may" be possible to get a one-time ferry permit and fly a 747 with two reversers inop, so theoretically it is "possible" but never, ever on a revenue flight.

Chris
Don't blame me, I don't work here...
 
kaddyuk
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RE: 744 Thrust Reverser Positioning Sensors

Mon Jul 17, 2006 3:50 am

Quoting N8076U (Reply 6):
Now, it "may" be possible to get a one-time ferry permit and fly a 747 with two reversers inop, so theoretically it is "possible" but never, ever on a revenue flight.

You'd need a Permit to Fly from the CAA and a NTO (No Technical Objection) from the Manufacturer I guess as you'd be operating outside the MMEL.
Whoever said "laughter is the best medicine" never had Gonorrhea

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