MWH Controller expressed concern regarding new operational policy which requires that TRACON functions be operated from the Tower cab. Reporter cites RADAR range issues and personnel crowding as safety factors.

Narrative

Moses lake; WA (MWH) was a split Tower upstairs/radar downstairs until about 4 months ago. Since then we have been ordered to work the radar from a Tower Display D Brite; with all Controllers crowded together in the Tower Cab. This configuration was previously only used during low traffic levels and with minimum staffing. Working heavy and complex levels of traffic while combining the radar functions within the Tower Cab reduced the margins of safety substantially. Most Controllers at my facility agree tht this is a very dangerous situation. Specifically; the Radar Controller must keep his radar range at about 60 miles in order to control aircraft within his assigned airspace. This one Tower Display Radar must also be shared with the Tower Controller. However; the 60 mile range reduces the actual size of the Tower's displayed airspace to less than 2 inches in diameter. Try separating 20 airplanes from each other on a display the size of a silver dollar. This is too small to be of much use with aircraft data blocks overlapping and hiding other aircraft positions and altitudes. The Local Controller must often resort to temporarily reducing the range on the shared display. The obvious problem with this fix is that the Radar Controller's airspace and aircraft are not displayed at all. The Radar Controller and the Local Controller must decide between them who needs to be able to see their aircraft more. Lastly; sometimes ATC Controllers just have to make it work because of staffing or equipment issues. However; in this case; we have 2 perfectly working radar scopes in the TRACON but have been mandated an unworkable policy that reduced my effectiveness to safely control air traffic; and prohibits access to radar scopes essential to my job responsibilities. The margins of safety have been reduced by this action. This arbitrary policy is a broken link in the chain of safety at Grant County International Airport.