An image forming apparatus includes an image forming unit adapted to form an image on a sheet, a first sensor adapted to detect skew or a folded corner of a sheet being conveyed, a second sensor adapted to detect multiple feeding ofsheets being conveyed, and a display adapted to display results of detection of the first sensor and the second sensor. The apparatus further includes a test fluid container in fluid communication with the fluid inlet, and a collection container in fluid communication with the fluid outlet. The hanger portion is configured for selectively engaging a cable. An elevation conveyor 5 is held in a cable 20a installed in an elevation space 9 through a coupling member 20b of a cableveyor 20, and can freely elevate and stop at a port 21 installed on each floor while being interlocked with motion of the cableveyor 20 caused by reciprocating circulation of the cableveyor 20 in a vertical direction by an elevation conveyor controller 4. The algorithms also account for the image processing and cockpit display functions, in accordance with the ultimate discernment by the pilot’s eye when viewing an appropriate display device. At least one of the first and second end disks has support knobs arranged in a circular arrangement about the longitudinal axis and extending in axial direction outwardly.