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OBK!
12th Sep 2007, 15:56
Wondering if anyone can help with a little tech issue i've seen twice now on the A320 with V2500 engines. After starting both engines and waiting for FADEC startup sequence to finish (grey box around N2), I've selected the guarded push button to activate bump thrust but it's only come up on one engine.

Obviously had to shut down both engines on remote stand and start again with fingers crossed. Quite frustrating but I have no idea why it does this?

A4
12th Sep 2007, 16:25
Hi,

Been a while since I operated V2500's but I do remember this problem. I once selected BUMP after starting the first engine and then when I selected it on the second (after start) it "flip-flopped" between the two! (indicated by a "B" next to the EPR gauge for each engine on the Upper ECAM). Only solution was to shut down "un-bumped" engine and restart.

I think you answered your own question - let the start sequence FULLY finish before selecting BUMP.

For those that have no idea what we're on about - BUMP is a facility on V2500 engines that puts an extra ring of injectors into the combustion chamber. Used to increase thrust at limiting fields...... but it cooks the hot section of the engine so is very detrimental to engine life.

If you watch the EPR gauges after TOGA is set you can see the EPR take another step up about 10 seconds after it has initially stabilised - presumably this is the "after burners" :) kicking in.

A4

spannerhead
12th Sep 2007, 18:57
I've worked A320 V2500's for a while and can't think where the heck a gaurded "bump" switch is. Please enlighten me before I hand my approval back to the quality dep't!

A4
12th Sep 2007, 20:54
Under a little flap on the back of each thrust lever. Missile launch buttons as I used to tell kids back in the days of flight deck visits............ :(

A4

OBK!
12th Sep 2007, 20:55
spannerhead

They're on the back of the thrust levers. One on each lever, but only need to push one to select bump on both engines when they are running.

A4

I'm probably going to leave it until taxi now to select bump but I'm desperate to find out what causes the single bump selection. Before this happened the first time I frequently selected bump without FADEC even finishing the startup sequence and it was fine. Must be another airbus gremlin!

A4
12th Sep 2007, 21:00
OBK - we must have been typing simultaneously........

Possibly controlled by FADEC Mod state? Don't know - I fly CFM's now - far more straight forward :)

If I needed BUMP I used to leave the switch guards down as a reminder before start and then select before the after start checklist.

A4

OBK!
12th Sep 2007, 23:32
A4

I used to do exactly the same, only recently had this problem!

Would much prefer CFM. It takes 2 minutes per start on these bl**dy v25ss. For it to go and have a glitch like this makes you want to use the crash axe.

Fargoo
13th Sep 2007, 02:06
spannerhead - it's a customer option, they don't all have it.

Phoebus
12th Mar 2008, 20:25
Bump was only applicable to V2500-A1... ...as an option. (The A1 being pretty asthmatic with anything other than sea-level ISA conditions.)

However, the latest V2500-A5 software standard refers to it again, not sure what step change would be achieved. Remember that the -A5 engine is the same physical device producing 22,000lbs on an A319 or 33,000lbs on an A321, only a small 'plug' in the FADEC is changed to tell the FADEC what it is.

Dream Land
14th Mar 2008, 11:03
(The A1 being pretty asthmatic with anything other than sea-level ISA conditions.)How true, and taking off with one armed and the other one not would have been a non-event. :cool: