American Airlines Flight 1572 Crash Analysis

Topics: Instrument approach, Air safety, Air traffic control Pages: 9 (2974 words) Published: March 18, 2011
The Accident

On November 12, 1995, an American Airlines McDonnell Douglas MD-83 type passenger aircraft, which was operating as Flight 1572, departed from Chicago O’Hare International (ORD); however, the aircraft got substantially damaged due to impact to the top of oak trees on Peak Mountain Ridge in East Granby, Connecticut. The aircraft also hit the Instrument Landing System (ILS) localizer antenna, which was on its way to Runway 15 of Bradley International Airport (BDL). The aircraft, lastly, crashed while on approach to Runway 15 of BDL at 00:55 Eastern Time. Fortunately, there were no fatalities and all 73 passengers and crew of 5 survived the impact.

Accident Factors

Among many contributing factors to the crash of Flight 1572, the most significant accident factors were environmental hazards. Due to severe weather conditions in the North Eastern U.S., there were many weather related contributing accident factors to the Flight 1572 crash. Firstly, according to the initial report that the flight crew received via the Automatic Communication and Recording System (ACARS), conditions like severe turbulence, icing at lower altitudes, high winds, reduced visibility, rain, and low-level wind shear were expected on the approach to BDL. The reason behind these extreme weather conditions was the rapid change in pressure around the Bradley area. Even though the flight crew received several Significant Meteorological Information (SIGMET), due to extreme conditions, the information they got was outdated in short notice.

In addition, it was found that the altimeter settings were not correct at the time of impact. The reason behind the false altimeter settings was that the flight crew did not set the altimeters according to rapidly changing pressure. American Airlines DC-83s were equipped with different altimeters that were set to different pressure references. One of the altimeters was set according to the elevation from the sea level, which was set to QNH. The other one was set according to the elevation from the airfield, which was set to QFE. However, at the time of impact, altimeter pressure settings were not matching with the ones that Boston air traffic control center and the Automatic Terminal Information Service (ATIS) have calculated. Due to the outdated dispatcher information and the SIGMET, the flight crew could not adjust the DC-83’s altimeters to the correct settings. Because of the rapid pressure drop and fight crew’s outdated pressure information, the aircraft was descending at an altitude that it should not have been descending under, the Minimum Descend Altitude (MDA).

The incorrect setting of the altimeter caused the aircrew to read the altitude false. Since the altimeters were set to the outdated pressure levels, the altitude shown in the cockpit was higher than it actually was. When the aircraft started to descend on their approach to BDL, due to the incorrect altimeter settings, it started to cruise at an altitude that was lower than the MDA. The MDA reported for the approach was 1080 feet from the sea level. Since the BDL airfield is 172 feet above sea level, the MDA according to the airfield was 908 feet. Even though the first officer was aware of the situation of rapid altitude descend and sense the MDA was approaching fast, he was busy with observing the external environment and looking for the airfield conditions. Since the limited visibility, high winds, and other extreme weather conditions, the first officer was helping the captain in monitoring outside and locating the airfield. Therefore, the first officer was not able give his full attention to rapidly descending altitude, and even descending to an altitude that is lower than the MDA.

In occasions like approaching to an airfield while extreme weather conditions are in effect and rough terrain is in sight, such as the steep ridgeline near East Granby, CT, it is advised that a Visual Descent Point (VDP) to be...
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