What was the Vmca of the 2-engine 747 config the El Al 1862 crew faced, and could they have landed the plane at a corresponding Vref?
The accident report says


  2.4.2 Performance
  
  An energy analysis was performed based upon altitude and airspeed
  data from the DFDR. It should be realised that this method does not
  allow extrapolation of performance capabilities in other conditions
  then those encountered during this flight. Based on this analysis the following conclusions can be made:
  
  
  Marginal level flight capability was available at 270 knots and go
  around power with a limited manoeuvring capability;
  At MCT thrust and 270 knots IAS there was no level flight capability;
  Performance degraded below about 260 knots at increased angles
  of attack. Deceleration to 256 knots resulted in a considerable sink
  rate.
  


(my emphasis)

My interpretation is that it is not appropriate to define a Vref for a 747 in that configuration.



Glossary

Vmca = Minimum Control (air) Velocity. Min speed that directional control can be maintained. Vmca2 for two engines (critical and inboard on same side) of a 4-engine aircraft.

Vref = Speed required as the landing runway threshold is crossed at a height of 50 feet in landing configuration.

MCT = Maximum Continuous Thrust. Thrust levels higher than this can only be maintained for a short time (e.g. minutes).