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several Significant Meteorological Information (SIGMET), due to extreme conditions, the information they got was outdated in short notice.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 Due to the outdated dispatcher information and the SIGMET, the flight crew could not adjust the DC-83’s altimeters to the correct settings. Because of the rapid pressure drop and fight crew’s outdated pressure information, the aircraft was descending at an altitude that it should not have been descending under, the Minimum Descend Altitude (MDA).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 used to control the descend. A VDP is basically a reference point provided to aircrew, or calculated by them, to be utilized on the approach to enable descend through a normal flight path instead of doing instant, steep sinks.
In addition, a VDP keeps the aircraft at an altitude that will not descend lower than the MDA. The VDP is useful for and frequently utilized during approaching to an unintended runway, such as the one at BDL, the VOR Runway 15. However, airmen of the flight 1572 were not utilizing any VDPs during the flight, did not calculate one either. Furthermore, the tower issues at the BDL airport might have contributed to the crash too. The last ATIS report the crew received was at 10:51 PM, which was almost two hours before the accident occurred.
That last ATIS record became obsolete in short notice due to rapidly changing weather conditions at BDL. Even though extreme conditions were in effect at BDL, the aircrew was not informed with recent information. Therefore, even though the last ATIS record that was sent to pilots informed them about extreme weather conditions at BDL, additional ATIS records should have been released. The reason behind not emitting new ATIS records after the one sent at 10:51 PM was the timing and personnel congestion issues at the BDL tower.
According to the controller that sent the last ATIS report to the crew, he was waiting for additional recent weather information to appear on the Systems Atlanta Information Display System (SAIDS); however, until the time he left the tower, which was around midnight, SAIDS did not show any new weather information. In addition, due to severe winds at BDL, a plate glass window of the radar room under the tower was loosened, letting rain inside.
Therefore, the controller at that moment closed the tower temporarily in order to supervise in fixing the loosened window. Meanwhile, according to the NTSB, a low altitude warning would not have been noticed even if there was one. According to the records, the warning came in late enough to miss the chance to warn the pilots about a very-low altitude approach. Besides, due to fact that SAIDS did not show any recent changes in weather information, current air traffic controller did not advise the on-coming air traffic controller about the situation.
In situations like this, the controller usually calls the airport police to go to the NWS Aviation Weather Center office and inform the personnel at the office to call the tower regarding an update on the weather information On the other hand, the Federal Aviation Administration (FAA) requires controllers to issue an ATIS report every hour even if there is not a change in the weather conditions. However, the controller stated that he was waiting for an update on SAIDS to emit the report to the crew; thereby, he did not think that issuing a new ATIS report was necessary at that moment.
In essence, the probable cause of the accident was the failure of flying the aircraft under the MDA. However, stating that the pilots’ error of maintaining the required altitude result the accident would be a harsh critique. There were contributing factors that triggered this pilot error. Extreme weather conditions obviously triggered several other factors at BDL that lead the tower controllers to pay attention to other issues that leading the aircraft to a landing; thereby, the pilots fail to maintain the correct flight path and flying the aircraft above the MDA.
Recommendations After the investigation of the crash of American Airlines Flight 1572, National Transportation Safety Board (NTSB) made several recommendations in order to establish a safer air transportation system. The FAA issued several orders according to some of these recommendations. Due to extreme weather conditions and steep ridgeline obstacle on the approach path, NTSB recommended publishing a VDP for approaches to the VOR runway 15 runway of BDL.
Publishing a VDP for this particular runway would help airmen to utilize a reference point in space to maintain a healthy approach angle even in the rough times like rapid pressure changes, high turbulence, or an obstacle on the way. Thereby, instead of observing the external environment and not concentrating to the instruments on the panel, the first officer would have been focused on descending below the MDA and would have been warn the captain to ascend to the correct altitude. It is common that the altimeter settings might be affected by sudden terrain changes and extreme weather conditions such as rapid pressure decreasing.
Since altimeters are extremely important for a pilot to gain control over the flight path, the Peak Mountain Ridge should be recorded as an obstacle that might very well affect the VOR runway 15 approaches. In addition, it is highly recommended to the FAA that in case of extreme weather conditions and since the Peak Mountain Ridge is a major obstacle that threatens any approach made to the VOR runway 15, appropriate guidelines should be implemented to Terminal Instrument Approach Procedures (TERPS).
One of the major effects that the BDL tower has done in the American Airlines Flight 1572 crash was not issuing ATIS as frequent as it should have. The most recent ATIS report issued before the crash was more than two hours old. Thereby, it is recommended that the tower should be issuing ATIS reports more frequent, especially during extreme conditions such as rapid pressure falling. Even though the weather information shown on the SAIDS equipment does not change, it is recommended to the controller to issue a current weather report to the crew, as frequent as possible.
It is also recommended that if a tower is going to be closed for any reason for a certain period of time, a relevant ATIS should be emitted to pilots. In addition, if an approach comes upon an air traffic controller shift change, the oncoming controller should be notified about the most recent information. The leaving controller should notify the relieving controller in case of a missing report, such as the NWS Aviation Weather Center report that was required to issue a new ATIS for pilots.
Thereby, the relieving controller might know if a long period of time has passed since the previous report has been issued, and act accordingly if an instrument approach is expected. Lastly, it is recommended for pilots to request more frequent updates on the airport conditions, such as controller shift changes or weather conditions. Thereby, even if the tower personnel forget to issue a recent report, pilots would let them know that they would require newer information regarding their approaches. Aviation Safety Issue
It is a fact that while the American Airlines’ MD-83 has lost both its engines after the tree and antenna impacts, and extreme weather conditions were extremely affecting the approach, it is a miracle that the American Airlines Flight 1572 crash had no fatalities. It can easily be said that the pilots have done their job really well during the last phase of the flight. The crew resource management and the effort of handling an emergency should be appreciated. Most of the passengers agree on the fact that the pilot of American Flight 1572 was a hero and he was doing what he was trained to do (Dunn, 1995).
However, the communication quality between the air crew and the BDL tower directs investigators towards a bigger safety issue. As one of the reasons behind the Flight 1572 crash, the outdated ATIS information and miscalculation of the altitude caused pilots to fly the aircraft at an altitude below the MDA. Due to rapidly falling pressure in the North Eastern region, the altimeter setting in the MD-83 should have been updated more frequently to keep the correct altitude on the approach.
Both the pilots and the tower personnel should be held responsible of this miscalculation. However, there was not a regulation towards this complication. Neither the pilots had to ask the tower personnel to update the ATIS reports more frequently, nor were the tower personnel obliged to do more frequent checks on the ATIS. In essence, even though the communication quality between those parties caused the aircraft to descend to an altitude that should not have been descended to, blaming either the tower personnel or the pilots would not be a solution to the real problem.
In order to enhance safety in such situations like rapid pressure decrease, wind shear, reduced visibility, high turbulence, or obstacle on the approach route, there would be additional regulatory requirements to be done. For instance, more frequent updates on the ATIS reports, additional SAIDS checks, or required VDP might be some examples. American Airlines, after the Flight 1572 crash, added new requirements from the airmen to cruise at an altitude 100 feet higher than the MDA on their instrument approaches to all airports (Brelis, 1995).
Furthermore, American Airlines directed its pilots to avoid landing, or landing to another suitable airfield in such situations like the visibility is reduced lower than one-half a mile. On the other hand, the tower issues were not so bright either. Due to a loosened window because of high winds, the only controller of the tower was supervising the radar room personnel in fixing that particular window. The radar room was shut down temporarily since the rain water was getting in the room, threatening the instruments (Pazniokas, 1995).
In situations like severe weather conditions, rapid pressure falling, and a coming shift change at the tower, the controller should not have been distracted from the duty of leading the aircrew to a safe instrument landing. In essence, even though it is not the aircrew’s priority to let the tower personnel about the conditions and the concerns, it would have been helpful for them to request more frequent updates on the SIGMET, ATIS and other instrument approach related information from the controller.
Likewise, even though it is not the controller’s duty to warn the NWS Aviation Weather Center to issue a more recent update on SIGMET, it would have been wise for him to stay alert while various weather-related hazards might affect the safety of the approach. Lastly, it can be considered as a miracle that the American Airlines Flight 1572 had no fatalities after losing both engines and having various structural damages on the fuselage. The pilots should be congratulated for the preparedness and quality crew resource management in an emergency situation.
However, American Airlines did the right thing by issuing multiple requirements from its pilots by demanding safer conditions like half-mile visibility limit, often pressure checks with the tower, and 100 feet higher altitude for non-precision landings (Brelis, 1995). Therefore, it can be said that even though it is not mandatory to fulfill such requirements, American Airlines is doing the right thing to eliminate this safety issue. Deficiencies The final report issued by the NTSB investigation of American Airlines Flight 1572 was adequate enough to explain the probable cause and findings about the contributing factors to the accident.
Fortunately, there were no fatalities and all of the flight crew and passengers were able to participate in the investigation procedures. Thereby, NTSB was well informed about almost every aspect of how the accident occurred. In addition, NTSB clearly stated that due to extreme weather conditions like rapid pressure decrease, low level wind shear, high turbulence, rain, and low visibility may have contributed the accident. NTSB also mentioned that these hazards contributed to the other factors like pilot error of wrong altimeter setting and various control tower issues.
Furthermore, NTSB investigation report added that the FAA should have considered the Peak Mountain Ridge as an obstacle for the BDL Runway 15 approach. Therefore, NTSB recommended the FAA to consider the Peak Mountain Ridge and the steep terrain when developing and modifying the approach to runway 15. As a result of this investigation and a similar crash in Cali, California, including a steep terrain difficulties as well, couple of months before, NTSB’s call for this issue has taken into consideration by the FAA.
However, even though the NTSB concludes the investigation report by stating that pilot error in the probable cause, it might have gone in depth with other contributing factors like the controller’s lack of attention to details or the FAA’s false approach requirements for the BDL runway 15. Blaming the pilots and stating that the error of not maintaining the altitude by descending to an altitude lower than the MDA was not satisfying enough.
In essence, the NTSB final report mentions almost every hazard that contributed to the American Airline Flight 1572 crash in depth. In addition, since there were no fatalities or serious damage or loss of fuselage, NTSB was able to go in depth to find out the factors associated with the crash. Thereby, NTSB made sufficient and appropriate recommendations to the responsible parties like the FAA, American Airlines, and Bradley International Airport. However, the report concludes the investigation by stating that the pilot error was the major cause of the accident. Stating that the pilot error was the only significant cause to this accident might not be satisfying to every party, especially American Airlines.
References
Brelis, M. (1995, December 5). Airline ups flight rules after crash at Bradley (City Edition). Boston Globe, 25. Boston, Mass: Boston Globe. (Document ID: 21418021). Dunn, R. D. , Jr. (1995, December 18). Pilot, crew of flight 1572 did their best (Statewide Edition). Hartford Courant, A. 14. Hartford, Conn: Hartford Courant. (Document ID: 22945376). National Transportation Safety Board. 996. Aircraft Accident Report: Collision with Trees on Final Approach. American Airlines Flight 1572, McDonnell Douglas MD-83, N5611, East Granby, Connecticut, November 12, 1995. DCA96MA008. Washington, D. C. : NTSB. Pazniokas, M. (1995, November 19). Altimeter setting a focus of inquiry into flight 1572 (Statewide Edition). Hartford Courant, A. 9. Hartford, Conn: Hartford Courant. (Document ID: 22935910). Walters, J. M. , Sumwalt, R. L. (2000). Aircraft accident analysis: final reports. New York: McGraw-Hill.
