LH problem
Hi,
It could have been an engine surge. If the Cpt said 'idle" it means that the engine was not shut down as for fire or failure.
As regards to FRA emergency services, I was there 2 months ago when a LH flt landed with minor hydro problem. The pilot did not declare "emergency" when he was querried by ATC, but the Em Serv went out - Better safe than sorry.
In my airline a surge should have been reported and a MOR - "Mandatory Occurence Report" filed.
Eng Surge can happen for many reasons and if dealt with properly, is not a big deal - it is not in the same league as fire or severe damage.
Good Luck and I just checked my DLAKY (DLH) shares - another 50 cents up...