Micro PLCs from IDEC control 70,000-lb doors at a giant airplane maintenance hangar in San Francisco.A Boeing 747-400 is 232 ft. long, has a wing span of 212 ft. and a tail height of 64 ft.. It weighs close to 875,000 lbs. at takeoff. The Superbay Maintenance Hangar at the San Francisco International Airport can accommodate up to four of these massive airplanes at one time. The hangar has eight doors—four on each opposite sides—allowing access to this huge space measuring 500 x 540 ft, about the size of two football fields.
Each hangar door (Figure 1) consists of two inner and two outer doors, each measuring 130 ft wide and 90 ft high to allow the planes to be towed in and pushed out using tow vehicles. Each door is made of two halves, each 65-ft wide, and weighs 74,000 lb. The door sections are mounted on dedicated rails (much like a train track), and the rails are offset so that adjacent doors can open and close without interfering with their neighboring door. Read More