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12 CHAPTER TWO FACTORS AFFECTING COLLISION RISKS A runway incursion is more likely to occur at controlled air- The following are some of the contributing factors that have ports when the exact location of an aircraft or vehicle on the been identified: airport surface is unknown or contrary to an ATCT instruc- tion. ATCT controllers are constantly reminded of their need Failure to follow established standardized procedures, to monitor the location and progression of the aircraft and Failure to understand the implications of one's actions vehicles operating on the airport surface, in accordance with or inactions, instructions issued, to provide assurance of separation. At Lack of training and practice to internalize procedures, uncontrolled airports, a safety hazard or runway incursion is Loss of SA, more likely to occur when proper procedures are not followed Failure to ask for help when confused, by pilots or by ground operators. Failure to use the airport diagram, and Unfamiliarity with the airport. One study that sought to identify the factors associated with incursions or surface incidents focused on ATCT controllers. When the questionnaire asked airport operators what factors It identified the most common factor for errors (27%) was the they had experienced or thought would increase the risk of controller "forgetting" something. Forgetting about an air- collision, the response was wide ranging and inclusive. The craft (e.g., holding in position or on approach) contributed most common factors identified by survey respondents were to 15% of the errors; 5% were related to the controller for- poor communication, poor visibility, and fatigue. The factors getting that a runway was closed; and 3% of the errors were identified represent the varying nature of airport operations at the controller forgetting about a vehicle on the runway. The different categories of airports. The following chapters pro- remaining 4% involved the controller forgetting something vide a synopsis of the type of factors identified in the survey else, such as a local procedure (26). responses, and they are grouped accordingly. A case example from the FAA follows: COMMUNICATION In daylight IMC, with Runway Visual Range reported at 3,000 ft, Airport operator responses to the questionnaire cited multiple a B737 captain--just after touch down--observed the amber rotating beacon on a vehicle about 1,000 ft. ahead on the runway. times that poor communication was a primary factor affect- The captain made an immediate "go-around" and missed the ing the risk of collision. Poor communication included failed eight vehicles by an estimated 10 feet. What happened? While or miscommunication with the ATCT and other crew mem- the aircraft was about 15 miles SW of the airport and being vec- bers, lack of communication of the snow plan or of ATC tored for a runway 36 Cat II approach, the local controller had given the ground controller permission for snow removal equip- traffic advisories, and confusion about radio communications. ment to proceed north on runway 36 and to exit runway 36 at Contributing to poor communication are radio-related factors the intersection of Runway 27L. The aircraft reported at the that could have a basis in human factors, communication tech- outer marker and was cleared to land with no further conversa- tion between controllers about the status of the snow removal niques and processes, or equipment operation. They include equipment. (27, p. 32) monitoring or using an incorrect radio frequency or the wrong radio, inoperative radio equipment, dead batteries, frequency Forgetfulness is not the sole domain of ATCT controllers, congestion, failure to switch frequencies, or noise. The dis- as airport maintenance and operations personnel can be just semination, or lack thereof, of safety-related information as forgetful, perhaps not of equipment on the airfield, but through the NOTAM system was also cited as a contributor where they are located and of procedures or requirements to poor communication. Dissemination of safety-related infor- that must be followed. Vehicle operators have a responsibility mation, proper communication protocol, and operator distrac- to maneuver their vehicles on taxiways and runways in accor- tion is discussed in more detail in chapter three of this report. dance with ATCT instructions. As a cause of errors, loss of SA is discussed further in chapter six. ENVIRONMENT The FAA Office of Runway Safety has identified through- Classified under environmental conditions are factors encoun- out its literature common factors for why incursions occur. tered during winter operations such as changing weather and