The emergency gear selector will certainly cause problems if it is selected to emergency (forward or partly so) position. This valve is normally open to allow hydraulic fluid to return to the reservoir from the return end of the right nose and both inboard main actuators. These are the actuators that are pressurised by the emergency hand pump to provide positive pressure for the down cycle of the gear in the event of a normal extension system failure. If this valve is not in its normal position it will cause slow retraction and most likely prevent the gear from retracting fully.
However this should only happen with a normal retraction cycle.
My experience with this valve was that it had little effect on the extension cycle.
Does any one know for sure if the flaps were available? If so this would suggest that the hydraulic system was not the root cause of the failure of the gear to extend.
That is not to say that there was not an electrical control problem with the gear system.
However if that was the case then the emergency extension should have been capable of getting the gear down.
It seems to me that this crew must have been faced with two separate problems with the gear.
The other possibility is that they were unable to extend one of the main legs and then they correctly followed the flight manual procedure and landed gear up. Does any one know if this was the case?
With all due respect to Cat1234 the Metro gear system is almost bullet proof although I agree that his senario is possible.
The investigation and report will be really interesting and may point to some possible defects that are really just appearing. Maybe the age/hours of the Metro's really are beginning to catch up with them.