RichPa,
Were they jammed above idle?
From the BEA Final Report (I eliminated the sections pertaining to brake details):
Between 15:58:10 and 15:59:03 the thrust is increased gradually from idle to a steady value of 1.25 EPR. This engine thrust setting corresponds to a position of the thrust levers between MCT (Max Continuous Thrust) and MTO (Max Take Off Thrust).
At 16:02:06 the person in the right seat starts talking but is interrupted at 16:02:08 by the person in the left seat who announces :
“Euh ... cabin is ... aircraft is moving forward”
The first significant LONGITUDINAL ACCELERATION parameter values showing a forward acceleration of the aircraft are observed around 16:02:07. The recorded ground speed starts to increase at 16:02:09 (3)
Note (3): Ground Speed values are recorded in increments of 1 kt.
Between 16:02:08 and 16:02:13 the ground speed increases from 0 to 4 kt.
At 16:02:11 the person on the left seat again says :
“Aircraft is moving forward”
An action on the brake pedals is recorded from around 16:02:11
The parking brake is deactivated around 16:02:13
The person on the right seat announces :
“Parking brake off”
From the moment the park brake is released:
• the brake pedals are briefly released on two occasions
• the recorded ground speed increases rapidly from 4 to 31 kt in seven seconds
The angle of the nose gear reaches 77 degrees right at 16:02:19 and remains at that value until the end of the recording. From 16:02:18 we can hear on the CVR severe vibration noises followed by impact noises.
The thrust levers did not move until 16:02:20 when they are retarded to the IDLE detent. The EPR values of the 4 engines start to decrease immediately afterward.
The longitudinal acceleration becomes significantly positive, indicating an aircraft deceleration, around 16:02:20.5
FDR recording ends between 16:02:21 and 16:02:22
I would assume the engines that couldn't be shutdown were at idle or close to idle.