Page:CAB Accident Report, American Airlines Flight 383.pdf/16

– 15 – shown on the No. 1 altimeter from that shown on No. 3; then substractsubtract [sic] the altitude shown on the No. 2 altimeter from that shown on No. 3. In each instance the difference shall equal the published elevation (ASL) of the airport of intended landing. Each pilot will call out the difference derived from his altimeter check for verification by the other pilot.

"(d) Care shall be exercised throughout the approach to monitor the barometric changes and to correct the altimeters accordingly, particularly when significant barometric changes are taking place.

"(e) During the final approach the pilot not making the landing, using the instruments of his own flight panel, will call out the altitude and airspeed checks that are currently specified in the respective aircraft Equipment Operating Manuals. The pilot making the landing will check the announced airspeed and altitude readings with those being displayed on his instruments.  This cross check shall also include checking that the No. 3 altimeter is indicating the appropriate value.  Any discrepancies of readings between instruments shall immediately be called to the attention of the pilot making the approach.

"(f) QFE settings may be obtained, upon request, from FAA operated control towers when Company facilities are not available.

"(g) All aircraft altimeters have both the adjusted filed pressure markers and the barometric scales. If an Instrument should fail or be suspected of error during flight, the other instruments may be used with QFE or QNH settings if desired."

The investigation revealed that the crew of N1996 was provided with a local station pressure altitude (QFE) of "815 above." This setting will result in a barometric scale position of 29.05 inches of mercury. The local station (QNH) setting provided to the crew was 30.00 inches of mercury. As was previously discussed, the captain's altimeter was found at a barometric setting of 29.06 inches with the index marker on 800 feet and the copilot's altimeter was found at a barometric setting of 29.03 inches with the index marker positioned at 815 feet.

The AA standard operating procedures for monitoring altimeters and rates of descent are outlined in the AA B-727 Operating Manual as follows:

"Monitoring Instruments

Localizer and Glide Slope Indications:

The pilot not making the landing and the Flight Engineer shall monitor GDI and HDI indications and shall call out any discrepancy, between the two panels, in glide slope or localizer indications.

Airspeed, Altitude, and Rate of Sink:

During all (VFR and IFR) approaches, the pilot not making the landing shall call out:

– Airspeed – any time it is below reference or above reference plus 10 knots after extending full flaps.