Low speed ingestion.
Had to use emergency reverse at low speed at the old Gotenborg on a DC 9 -51 to stop us sliding off the cliff at the end.
Engines surged repeatedly - characterised by a very loud bang as the airflow re established itself and ignited the fuel in the back end.
Reduced the thrust until the banging stopped (emergency reverse - white knuckle reverse).
Fortunately we hit some ice with some braking action otherwise I wouldn't be writing this.
Borescope check reviewed no damage.
Reverse is much more effective at high speed and ineffective at low speed - so if in doubt I always pulled a little too much when initially setting it.
Once watched a skipper reverse off a stand in lhr - not a good idea because of FOD and the risk of standing the aircraft on it's tail.
Couldn't be done on a VC 10 because of the castoring nosewheel.