cdfmxtech
Topic Author
Posts: 1319
Joined: Wed Jul 05, 2000 11:37 am

B757 Speedbrakes EXT

Fri Feb 01, 2013 12:34 am

Read this in an article about the Britannia 757 incident years ago:

In 1999, Boeing modified the speedbrake alert system for all B757s built after June 1999, to include a warning light whenever the speedbrake lever is beyond the ARMED detent and the engine thrust lever is forward of the flight idle position for more than 15 seconds. Boeing considered a retroactive change to the fleet, but this was not implemented.

Is anyone aware of any 757s actually flying around with this mod?
 
EGGD
Posts: 11880
Joined: Sat Feb 24, 2001 12:01 am

RE: B757 Speedbrakes EXT

Fri Feb 01, 2013 6:28 pm

From our QRH:

Message: SPEEDBRAKES EXT

Condition: The speedbrakes are extended and one or more of these occur:
  • The radio altitude is between 15 and 800ft
  • The flap lever is in a landing setting
(Boeing 757-300s)
  • a thrust lever is not closed


Not the most descriptive entry, but a look in the Boeing Tech CD that the company kindly provided for reference leads to a slightly more conclusive reference:

Quote:
The EICAS caution message SPEEDBRAKES EXT displays and the SPEEDBRAKES light illuminates if speedbrakes are extended when:
•the flaps are in a landing position (25/30) or
•Captain's Radio Altitude is 800 feet or below or
•757-300 either Thrust Lever forward of flight idle for more than 15 seconds

Note: The warning is inhibited below 15 ft Radio Altitude


It would appear that there are two 757-300's flying in the UK with that particular modification. The airline also has two 757-200's built after June 1999 (and one built in June 1999), there is no reference anywhere as to whether they have it but considering we apparently only recently found some of the aircraft in the fleet had Hydraulic Generators I wouldn't be surprised if they did.
 
cdfmxtech
Topic Author
Posts: 1319
Joined: Wed Jul 05, 2000 11:37 am

RE: B757 Speedbrakes EXT

Fri Feb 01, 2013 9:26 pm

Hi EGGD,

Thanks for the reply.

Beginning to think it's a option.
From our AMM

The speedbrake warning is generated by the landing
configuration warning module in either of the following
conditions:
1) RA >15 feet and speedbrake lever is above the trip point
(spoilers extended) and flaps are in the landing position.
2) 15 feet
 
EGGD
Posts: 11880
Joined: Sat Feb 24, 2001 12:01 am

RE: B757 Speedbrakes EXT

Fri Feb 01, 2013 11:50 pm

Quite possibly. I know that our 757-300s were very high specification, so no surprise that they have the additional warning for the thrust lever positioning. All our 757's have the SPEEDBRAKE EXT warning light and I assume that it has always been standard on the aircraft for the other conditions (flaps landing position/RA less than 800ft)?
 
cdfmxtech
Topic Author
Posts: 1319
Joined: Wed Jul 05, 2000 11:37 am

RE: B757 Speedbrakes EXT

Sat Feb 02, 2013 1:48 am

OK - new development. I checked out my airlines AFM - and the same note is in there regarding our 757-300s. BUT - I have combed thru the systems schematics and there is no thrust lever input to the circuit that provides the SPEEDBRAKES EXT light. They usually don't lie to the pilots (they have no problem lying to the techs though lol)...but in this case - I'm thinking this might be an incorrect statement in the AFM. But going to keep digging.

Re: your question, as far as I know that logic (Flaps, RA >15

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