Windmilling engine and the backup generator???

[AeroTech]

Hi,

Certain aircrafts (like B 777) are fitted with backup generators (BUG). If for certain raisons the engine is shutdown or flame-out, the IDG is no longer on-line. Does the BUG come on-line in such case and provide electric power?

-If we have all engines flame-out, can the BUGs provide electric standby power, or only the RAT will provide the standby power.

Thank you.
Best regards.

[Bolty McBolt]

Aero tech

What is your fixation with in-flight shut downs. All of your threads start with “with an engine shut down or all engines flamed out”
Engine manufactures go to great lengths to make sure this does not happen and if airlines maintenance become lax and in-flight shut down occurs the external governing bodies FAA JAA CASA etc remove etops or shorten operating etops limitations from 240 minutes to 120 or 180mins to 135 mins etc as applicable.
I mention this to emphasise how important it is to any airline operating large twin engine jet aircraft NOT to have in in-flight shutdown.

Your Backup Generator is a wild frequency generator used in case of main generator failure (IDG) to provide a separate power to flight control/ auto pilot computers etc.. “Essential power”
Check your mail for the rest..
I hOPE THIS HELPS

[Swedish Steve]

The B777 Back up generator is driven by the engine and will not operate at windmilling speed.

[AeroTech]

Hi,

Thank you guys for your post.
-Bolty, currently what is the maximum diverstion time for certain B 777 (the approved time by FAA)?

Originally posted by Steve
The B777 Back up generator is driven by the engine and will not operate at windmilling speed

Originally posted by Steve

The B777 Back up generator is driven by the engine and will not operate at windmilling speed
Steve, did you experience it in aircraft or in sim?

Thank you.
Best regards.

[Swedish Steve]

The BU generator is a 20kva frequency wild (i.e. it turns at engine speed no CSD). It is quite big, not like a Dedicated generator. It is tested every engine start and then sits there waiting for an engine or IDG failure when it powers the Transfer Bus. The BU gen convertor sits in the MEC and converts the power to Constant Frequency. Only one BU generator can be on line at a time. It comes on line just before the engine reaches idle, just like any other generator.

[AeroTech]

hi,

originally posted by Swedish Steve
The BU generator is a 20kva frequency wild (i.e. it turns at engine speed no CSD). It is quite big, not like a Dedicated generator. It is tested every engine start and then sits there waiting for an engine or IDG failure when it powers the Transfer Bus. The BU gen convertor sits in the MEC and converts the power to Constant Frequency. Only one BU generator can be on line at a time. It comes on line just before the engine reaches idle, just like any other generator.

What do you mean by the MEC? Is it the main engine control???
Thank you
Best regards.

[Swedish Steve]

No. It is the Main Equipment Centre, the little cave under the first class galley where the engineers climb into to fix things. On the B777 you have to visit it often because Boeing have moved all the circuit breakers down there away from the pilots.

[gas path]

On the B777 you have to visit it often because Boeing have moved all the circuit breakers down there away from the pilots.
All the important ones anyway:} :}

[Blacksheep]

...and if airlines maintenance become lax and in-flight shut down occurs the external governing bodies FAA JAA CASA etc remove etops or... I'm sure they would, but "lax maintenance" is an airworthiness matter, whereas ETOPS is concerned with reliability. A quite different matter altogether.

In rather simplistic terms, ETOPS is based upon the reliability monitoring program. If the reliability program reveals that the IFSD rate has exceeded a set value, the ETOPS rating is automatically downgraded and the engineering department will report this to the FAA/EASA/CAA/DCA/DGCA or whatever body applies. (In fact a representative of the regulatory body often sits as a member of the reliability committee.) The regulator will then monitor the corrective action (service bulletins etc.) taken and grant restoration of the ETOPS rating only when it is satisfied that the required reliability level is restored. It is worth noting that not only engine reliability is taken into account; system reliability is also monitored.

If an airline violated the ETOPS program by failing to report a reliability shortfall, I'm sure the sanctions would involve more than mere removal of an ETOPS rating. As would be the case in the event of "lax maintenance"

I had sharp and rude words about this on another forum far to the east of here recently!

[Bolty McBolt]

Hi Black sheep

Thankyou for taking me to task :O
But i think you missed my point. I was trying to illistrate how important it is for airlines and manufactures of aircraft/engines NOT to have inflight shutdowns. Mr Aerotech seems to have a fixation with what happens after an inflight shutdown.
To be honest I was dumbing it down for the "postees" benifit as you can see had to ask what an MEC was and I have seen aerotech's threads before.

I am surprised that as an engineer you would not link maintenace which is a process, to flight reliability.
Is it the statistics that keep the engines running
Perhaps I have misunderstood?

Bolty