the crew might have boosted the Auxiliary Power Unit to compensate.
I'm not an expert, but I don't believe that the APU was running upon reaching the stand because once the engines were finally shut down, there was a good 20 - 30 seconds of quiet before I heard the APU start up.
Also, when engine noise increased there was no movement at all - brakes were clearly firmly on.
What was very strange was that, although I don't think this is possible, the apparent engine thrust increase was linked to the cabin lights going out...
If the GPU was dodgy and was failing like Marlow and Paxboy say, would the main engines be required to compensate by increasing thrust? (I wouldn't have thought so, because at idle, the aircraft is running off power from the engines anyway, right? Unless there was a short?)
Also flight was FRA to LYS LH4178 9th Oct 2008, A/C was a 733. Sorry - I am getting confused with all the travelling I'm doing at the moment!
Cheers
Rich