The safety margins of a long-range business jet can be eliminated in a few seconds by a thin, almost invisible sheet of ice. That fact about engineering has become the focal point to the questions of a private-jet crash on a takeoff landing in Bangor international Airport in the north part of Maine.
According to the federal authorities, the aircraft crashed soon after takeoff and landed inverted before burning. Local airport management advised that the field was not open until further notice despite the difficult winter weather conditions that complicated access into the site and ground movement around the field.
The initial news about who was aboard and the number of people aboard have not been consistent in first issues, which is typical of the prime time of major accidents in the first 24 or 48 hours. Before verifying an ultimate accounting, investigators usually balance passenger manifests, flight plans, and operator records and physical evidence. To engineering readers, the operating envelope is more robust: a fast jet taking off with the runway surface contaminated or changing rapidly, with aerodynamic tolerances based on tight assumptions concerning a “clean wing.”
According to the data published in an incident summary, the aircraft was a Bombardier Challenger 650 with tail number N10KJ manufactured in 2020 and flew into Bangor after a flight out of Houston. The same notes that the crew had ordered Type I and Type IV de-ice and anti-ice fluids prior to departure taxiing. It also writes of a take-off landing attempt on the runway 33 and a loss of directional control as well as roll over, which was followed by a post crash fire.
Such information is important as the wing-design of the Challenger family is efficient at cruise but with a small contamination tolerance at low speed. In swept aerodynamically clean wings, without leading-edge slats, or other forms of high-lift forgiveness, the maximum lift-to-ratio can decrease abruptly in response to the disruption of air-flow at the leading edge by ice or frost or slush. Any slight roughness will increase the stall speed and decrease controllability at the worst time: rotation and initial climb when there is limited altitude and time.
Practically, the safety of winter takeoff is constructed in a chain of controls that interlock, i.e., the choice of fluid, its quality of application, holdover time, intensity of precipitation, delay during taxi-uing, and the final check of the pilot on the clean wing. The performance numbers based on which the V-speeds and thrust assumptions are set can be invalidated by any weak link. The investigators also measure runway conditions and braking behavior, since a veer or excursion may be catalyzed by an uneven friction, cross winds or contaminated road surface, or asymmetrical thrust and braking reaction in a high-speed roll.
According to Bangor airport director, the first responders were present in less than a minute, highlighting the rapidity with which airport rescue and firefighting teams can get to the runway area in case of of an incident when the field is active. Nevertheless, the questions of extinction and site stabilization do not provide answers to the engineering questions that come up.
The National Transportation safety board and the federal Aviation Administration will look into the pilot, the aircraft and the operation environment including the maintenance history, in-house systems, weather reports and any de-icing history. The aim is to see which assumption will fail first the airframe, surface, procedure or environment at the most unsympathetic stage of the flight.
