ANALYSIS: Bangor Challenger crash highlights importance of bizav winter operations

During a severe winter storm on Jan. 25, a Bombardier Challenger 650 crashed while taking off from Bangor International Airport (BGR) in Maine. The crash killed the pilot, co-pilot and four passengers. The NTSB's preliminary report indicates that the crew tried to take off after exceeding the anti-ice treatment's maximum holdover time.Its analysis of the cockpit voice recorder (CVR) revealed a troubling discussion among the flight crew about holdover times as they were taxied to runway 33. The pilot commented that it was "standard" to have 14-18 minutes and that if the wait was more than 30 minutes, they would return to the ramp to deice again. Without any objections, the copilot concurred. This discussion highlighted a critical error and sealed the fate of the passengers and crew. A standard holdover time simply does not exist. Technically and legally, the crew should have never attempted to take off.PREVIOUS STORIES:NTSB releases preliminary report on Challenger 650 crash in Maine AOPA Air Safety Institute suggests icing as factor in Challenger 650 crashBy definition, a holdover time is the estimated time anti-icing fluid will prevent the formation of frozen contamination on the protected surfaces of an aircraft. Holdover time always begins with the holdover start time, the time at which the final application of fluid has begun. The length of a holdover time varies. In very light snow, a holdover time using a common Type IV anti-ice fluid may last up to three hours. In the case of the accident flight, the holdover time was only nine minutes due to moderate snowfall intensity and extremely low outside air temperatures. Once the holdover expires, and if precipitation is still present, the aircraft must be retreated with deice/anti-ice fluid, or the pilots must complete a pretakeoff contamination check (PTOCC). A PTOCC is rare. If weather conditions warrant this type of inspection, other alternatives - such as delaying a takeoff - should be considered. Holdover time calculations Determining the actual holdover time is a complex procedure and requires multiple steps. Airline and charter operators are required by federal regulations (14 CFR 121.629 and 14 CFR 135.227) to have an approved ground deice / anti-icing program that helps guide pilots through these steps. Business aviation operators, such as the crew of the accident flight, under Part 91 (14 CFR 91.527) are not required to have an FAA-approved program; this is both concerning and problematic. As an example of its complexity, pilots must first analyze the current weather and determine the intensity of the snowfall based on the prevailing visibility using the FAA-approved Snowfall Intensity Table (FAA Holdover Guidelines for Winter 2025-2026, table 54). This table accounts for visibility, day or nighttime conditions, and outside air temperature to determine the snowfall intensity classified as either very light, light, moderate or heavy. On the night of the accident flight, the weather at the time of the deice/anti-ice process was surface visibility of ¾ miles, light snow and an outside air temperature of -16 degrees Celsius. NTSB analysis utilizing the FAA Snow Fall Intensity Table, under these weather conditions would classify the snowfall intensity as moderate based on ¾ miles visibility and nighttime conditions. Next, pilots must reference the appropriate holdover time table for the specific type and brand of the fluid to be used. This table factors in the outside air temperature, fluid concentration, type and intensity of the precipitation, as determined in the first step. In some cases, such as heavy snow, there may not be a valid holdover time. The NTSB further analyzed the applicable hold-over time table (FAA Holdover Guidelines for Winter 2025-2026, table 38) for the accident flight. Using the "corrected" (as determined in the first step) moderate snowfall intensity and the extremely low outside air temperature of -16 degrees Celsius, the NTSB determined the maximum holdover time under these conditions was only nine minutes from the start of the anti-ice application. The NTSB preliminary report did not discuss the significance of anti-ice applications in extremely low temperatures. Type IV anti-ice fluids are chemically based on Propylene Glycol or Ethylene Glycol and are considered non-Newtonian fluids (meaning they require a shear force to be removed from the aircraft). These anti-ice fluids lose effectiveness at extremely low temperatures (below -14 degrees Celsius). Below these temperatures, the fluid-absorbing characteristics are diminished, and the fluid can solidify to the point that it will not shear off from the wing. Timeline for accident flight NTSB investigators created a timeline for the accident flight in its preliminary report. Several sources were used to build it, including ADS-B information, CCTV images and the flight data recorder (FDR). The aircraft arrived in Bangor at 18:09 EST on a flight from William P. Hobby Airport (KHOU) in Houston, Texas. This was the first of a two-leg transatlantic flight. At 18:15 EST, the aircraft arrived on the FBO ramp and was refueled for the planned flight to France. It's important to note, at around this time, weather conditions in Bangor were bad. Two separate airliners, as reported on LiveATC.com, were discussing failed pretakeoff checks on the ATC ground control frequency before attempting to depart from Bangor. One airliner mentioned that its anti-ice fluid had failed near the departure end of the runway and that they planned to return to the deice pad to be retreated with deice/anti-ice fluid. ATC at the time, reported contaminated runway surfaces with condition codes of 3/3/3 (the scale is 1 to 5 with 5 being the best) and medium braking action reports. The accident aircraft spent approximately one hour on the FBO ramp before taxiing to the deice pad. After refueling, the pilots of the accident aircraft coordinated with deice personnel to accomplish a two-step deice/anti-ice treatment. The two-step treatment includes removing snow and other contaminants with a heated Type I de-icing fluid, followed by the application of Type IV anti-ice fluid to provide extended protection from frozen or freezing precipitation prior to takeoff. A one-step de-ice treatment, using Type I de-ice fluid only, can be used to clean the aircraft, but offers very little anti-ice protection during active periods of precipitation. Type I deice fluids offer very little anti-ice protection other than heat transfer from the fluid to the wing surface. According to the NTSB, from 19:19 to 19:27 EST, the aircraft was deiced with 41 gallons of Type I deice fluid. Within 40 seconds, the application of Type IV fluid began. Records indicate that, over the next three minutes, 28 gallons of deice fluid were dispensed from the deice truck. Nine minutes and counting… Remember, the NTSB determined that the maximum holdover time under these conditions was nine minutes from the start of the anti-ice application. In this case, the holdover start time was 19:27:43 - this meant that the aircraft had to be airborne no later than 19:36:43. Following the anti-ice application, according to the NTSB report, the aircraft sat for 4 minutes 51 seconds before taxiing from the deice pad at 19:35:46. More than eight minutes had elapsed since the beginning of the holdover start time. At 19:40:16, the aircraft reached the departure end of runway 33. Approximately 3 minutes 41 seconds later, the aircraft began its takeoff roll. At this point, the maximum holdover time had expired by more than 7 minutes. According to FDR data, engine power began to increase toward the selected thrust of 85% at 19:43:05. Within 20 seconds, the co-pilot made most of the appropriate callouts and the pilot began to rotate the aircraft for takeoff as the left and right main landing gear weight on wheel indications changed from ground to air. Seconds later, the pitch attitude increased to 13 degrees aircraft nose up (19 degrees AoA). Within a second, both stick shakers independently activated and the aircraft stalled. The last FDR recording indicated a pitch attitude of 6 degrees aircraft nose up and a bank angle of 77 degrees, right wing down. "Multiple airport CCTV cameras captured the airplane during the takeoff and captured the aircraft impacting the ground, followed by several explosions as the impact sequence progressed," the report stated. From tragedy we learn The final NTSB report on this accident is expected to be released in the next 12 months. Once published, this final report will determine the probable cause of the accident. For the business aviation community, this accident must be treated as a watershed moment. This accident was preventable and highlights a lack of knowledge and understanding of aircraft winter operations - such as deicing and anti-icing procedures - in business aviation. Although not required by regulation, CFR Part 91 operators can follow the model of AC 120-58 and, at a minimum, download the current FAA Holdover Tables and Guidance, updated every August.