Page:NTSB Aircraft Accident Report, United Airlines Flight 389.pdf/24

 A VHF navigational receiver was recovered set at 113.0 mcs., the frequency of the Northbrook VORTAC north of O'Hare Airport.

The first officer's altimeter was recovered with a barometric setting between 29.91 and 29.92. There are two three-pointer type altimeters installed in the cockpit, one on each pilot's instrument panel. These altimeters have three concentrically mounted pointers, coded in length and shape. The long pointer indicates 100's of feet, the short, stubby, roughly diamond-shaped pointer indicates 1,000's of feet, and the shortest pointer, with a short cross bar, indicates 10,000's of feet. The 100's pointer makes one complete revolution per 1,000 feet of altitude change, the 1,000's pointer makes one complete revolution per 10,000 feet of altitude change, and the 10,000's pointer makes one complete revolution per 100,000 feet of altitude change. The 10,000 feet pointer is painted on a rotating plate which has a slot cut around part of its circumference and a wedge-shaped cutout on the face of the plate approximately 90 degrees to the left of the pointer. The two cutouts are arranged so that at zero elevation the wedge exposes a black and white hash marked area and the circumferential cutout exposes a black background on the instrument face As the altimeter is taken to higher altitudes the plate rotates clockwise gradually exposing a white arc to the left of the 10,000 feet pointer and gradually covering up the hash mark area. At an altitude of approximately 16,000 feet the hash mark area is completely covered and the white arc is exposed to a point approximately halfway between the Nos. 1 and 2 on the face of the altimeter. As the altimeter is taken further up in altitude more of the white arc is exposed. As the aircraft descends the situation is reversed and the white arc is gradually covered up and at approximately 16,000 feet the hash marked area is again brought into view. For examples of altimeter presentations see Attachment #2.