I witnessed this incident as a passenger whilst taxiing near the runway as the 747 took off yesterday morning. Because of the angles of view I did not see if there was a problem until rotation, when it passed us. At rotation and during the part of the initial climb that I could see, orange flames trailed the No 1 engine in regular double pulses, each double pulse with an interval of about 1.5 seconds. The flames appeared detached from the engine by about 10 metres and the flames themselves seemed about 15 metres long. It reminded me of the recent footage of the ?Britannia? 757 following a birdstrike.
very descriptive and enlightening.
You are describing a classic engine stall/surge response to an internal problem. The engine is not quite sick enough to run down so it tries to recover to the same power setting that it demonstrated that it could not handle.
If left alone it would probably overtemp.
One could point at the possible causes, but the idea is to just fix it for now and think about insurrance claims later.