Hello:

I was reading Captain's Dave latest blog post (sorry can't seem to be able to paste the link; search Flight Level 390 to find it) in which he describes pushing a little red button to activate boosting on his V2500-equipped A321.

I was not aware that such a feature existed and I can not find any online resource describing it. Could someone tell me more about it?

Thank you!

http://www.smartcockpit.com/data/pdfs/flightops/aerodynamics/Flex_and_Derate_Takeoff_and_Climb.pdf

Pages 21-25

Thanks a lot!

This text/image is from A330 but for a general understanding:


THRUST BUMP CONTROL (OPTIONAL)

The optional thrust bump function can be used to obtain an additional
thrust capability during take-off. It permits to increase the maximum
thrust rating from engine CF6-80E1A4 to engine CF6-80E1A3, i.e
from 70.000 lbf to 72.000 lbf.
It is controlled from the guarded pushbuttons fitted on the thrust levers.
The thrust bump is engaged when:
- the A/C is on ground,
- the engines are running (N2>50%),
- TRA is in forward thrust region,
- one of the two bump P/Bs has been pressed.
The thrust bump is disengaged on ground when:
- reducing thrust levers to, or below, MCT,
- pressing one of the two bump P/Bs, if the thrust levers are not at
above MCT,
- the engine is shutdown.
The thrust bump is activated if FLEX T/O or DERATED T/O have
not been selected. The thrust bump is automatically deactivated by
the ECU after take-off, when the thrust lever is at, or below, CLB.
The Thrust bump engagement is identified by a "B" displayed in green
on RH side of N1 indication.
In case of EIVMU failure during take-off, after bump activation by ECU, the bump condition is maintained.


http://i474.photobucket.com/albums/rr101/Zab999/ThrustBump.jpg

Thanks a lot. Out of curiosity, do you know of many operators which have ordered it?

Qatar is a main operator of the GE80E1A4B (bump capable) engines.
(acc. owners & operators guide 2008)

You will trade EGT margin for extra thrust when required.

I think operators nowadays will order A3 (same thrust as A4B with bump engaged) and derate/flex when full thrust is not required.

Each time you "BUMP" it has to be reported in the tech log. Bump also reduces the time on the engine. I found it to be a nuisance. It's quite stupid and should be removed/discontinued in my opinion.
T