On October 25, 1999, a tragic accident of the Learjet Model 35, N47BA occurred at around 1213 (CDT). The plane crashed near Aberdeen, South Dakota. The plane departure was Orlando, Florida and it was heading to Dallas, Texas. Radio contact was lost north of Gainesville, Florida after the airport regulation cleared the plane to flight level 390. Amid the flight, the plane was captured by a few US Air Force and Air National Guard flying machines as it moves northwest bound (Aviation Accident Brief, 2000). The witness pilots of the military airplanes stated during an interview that the forward windshield of the Learjet seemed to be frosted or covered with condensation. Therefore their vision into the cabin was limited. Also, they did not discover any unusual conditions on the plane. After investigations, the probable cause found by the National Transportation Safety Board was incapacitation of the flight crew because of inability to get a sustainable supply of oxygen following a loss of cabin pressurization, for reasons not known (Aviation Accident Brief, 2000).
Pressurization failure in airplanes can be caused by different reasons. Following this case study as the witness pilots observed there was no structural failure of the plane such as failure of a window or an in-flight explosion which might have caused pressurization failure (Auten et al., 2010). More probable factors that might have caused the failure may be the failure of the pressurization system. When the system malfunctions in some parts such as the outflow valve it may cause the pressure in the plain to drop and deplete the oxygen causing incapacitation. Furthermore, other factors such as deliberate act may cause the pressurization system to fail. Such act which a captain may consider as a way of clearing cabin smoke, however, the act may go unexpected and the pressure fails to return to normal hence reduction of oxygen level inside the plane (Auten et al., 2010). Also, inadvertent system control inputs may cause the pressurized system of the plane to fail. Such occurs during an incorrect activation of a critical pressurization control. As such accident occurring it may cause the system to fail and hence the oxygen levels in the plane drops and end up causing crew incapacitation.
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As usual, every aircraft is pressurized to create an environment which is psychologically suitable for humans. The pressure difference between the inside and outside of the plane depends on the modification of the plane as when the plane goes above the atmosphere the higher the pressure difference needs to be maintained (Auten et al., 2010). Due to this mechanism, a balance between structural design and psychological need is obtained. As the air pressure reduces with increase in altitude the atmospheric air remains constant. However partial pressure of oxygen diminishes and the decrease of gaseous pressure likewise lessens the stream of oxygen crosswise over lung tissues of an individual and into the circulation system. This significant decrease in the ordinary grouping of oxygen in the circulatory system is called Hypoxia. Flight physiology is directly linked up with the pressurization failures. When any of the factors cause the pressurization system to fail it directly affects the people on board by causing Hypoxia and all the crew becomes unconscious and eventually respiratory and heart failure.
References
Auten, J. D., Kuhne, M. A., Walker, H. M., & Porter, H. O. (2010). Neurologic decompression sickness following cabin pressure fluctuations at high altitude. Aviation, space, and environmental medicine, 81(4), 427-430.
Aviation Accident Brief AAB-00-01. (2000). Retrieved from https://www.ntsb.gov/investigations/accidentreports/pages/aab0001.aspx
Loss of Cabin Pressurisation - SKYbrary Aviation Safety. (2018). Retrieved from https://www.skybrary.aero/index.php/Loss_of_Cabin_Pressurisation
