Bombardier CL-650 | N10KJ

DTSB: The DTSB determines the Probable Cause of this accident to be an aerodynamic stall during liftoff, caused by contaminated wing or tail surfaces, for reasons that remain undetermined at this time.
The reported weather at the time of takeoff clearance was 1 ¼ statute miles (RVR greater than 6,000), light snow, and temperature -16°C, or 3°F. Using the annually issued FAA Winter 2024-2025 Holdover times guidelines document, table 54, indicates a classification of Moderate snowfall, even though the tower reported snowfall as light, and snow was not accumulating on the ground.
The KBGR FBO has reported that the Type IV anti-ice fluid in use at their facility is 100% UCAR FlightGuard AD-49 as shown in Table 38 from the same FAA publication. This particular Type IV fluid creates a holdover time between :02 and :09 minutes at -16°C, 3°F. This same specific fluid allows a generous :40 to 1:15 of time at -14°C (7°F), a difference in only 2 degrees Celsius warmer ambient outside air temperature.
The accident aircraft began the takeoff sequence approximately 16 minutes and four seconds after the final type IV application began, and 8 minutes and 11 seconds after starting the taxi process to the runway. Hold over times are calculated using the time that the final application began as the start time, but are also known to be very conservative in nature.
Given the reported and crew observed very light snowfall, and the published procedure, the de-ice (Type I – cleaning) and anti-ice (Type IV -gel coating protection layer) should have been more than sufficient to ensure a clean aircraft for takeoff in frozen dry very light snow conditions, at temperatures near 3°F. The conditions were typical of Maine winter conditions at that time, and certainly could not be considered unusual or dangerous in any way. It appears that the accident crew followed all FAA guidelines and procedures. A Part 121 aircraft just ahead of the accident aircraft returned to the gate after fully expecting to takeoff in the same conditions, but yet returned to the gate and reported that “Our de-ice fluid just failed” – indicating a possible mechanical failure in the de-ice and anti-ice system as a function of the FBO provided service.
The other FAA publication entitled “FAA Ground Deicing Program, General Information” contains this important note regarding the use of Type I fluid as an aircraft cleaner:
“(6) The applied temperature requirements for Type I fluids are located in the Type I fluid application table in the FAA HOT Guidelines (Guidelines for the Application of SAE Type I Fluid- Type I Anti-icing Guidelines). Type I HOTs are based upon a minimum fluid temperature, measured at the dispensing system nozzle, of 60 °C (140 °F). Dispensing Type I fluid for anti-icing purposes, at a temperature less than the minimum allowable temperature invalidates the published Holdover times.” Type I fluids are purchased in bulk and mixed with normal water on site in a process called dilution. Dilution rates are typically 1:1, or 50% water.
The FAA Deicing guidelines and General information document were created primarily for FAA Part 121 usage, and the opening page of the FAA Guidelines document offers this information: “This is a guidance document. Its content is not legally binding in its own right and will not be relied upon by the Department as a separate basis for affirmative enforcement action or other administrative penalty. Conformity with the guidance document is voluntary only. Nonconformity will not affect rights and obligations under existing statutes and regulations.” Page 25 of the FAA Ground Deice Program document clearly indicates the critical aspect of the effectiveness as relates to the FBO and individual FBO employee applying the applications. “ (6) The effectiveness of Types II, III, and IV fluids is highly dependent on the training and skill of the individual applying the fluids. When these fluids are used, ground personnel should ensure that they are evenly applied so that all critical surfaces, especially the leading edge of the wings, are covered with fluid. In addition, an insufficient amount of anti-icing fluid, especially in the second step of a two-step procedure, may cause reduced HOT because of the uneven application of the second-step fluid.”
The weather conditions were not so severe that other air carrier crews aborted their assigned missions prior to going to deicing, and it is likely that any similarly situated crew would have chosen to begin the deice process, and plan for takeoff as well. The airline flight crew that had previously reported a mechanical fluid failure indicated that they were going to go through the deice process a second time, and anticipated a normal departure.
It is evident that the accident aircraft flight crew was seasoned, qualified, current, and followed all regulations and procedures. The accident crew specifically did “not” exceed any Anti-ice limitation, as there was no delay incurred, and there was no FAA Anti-ice limitation in place. The total time taken by the accident aircraft flight crew to re start engines and reach the runway and be ready for takeoff after leaving the de ice area was very efficient. As indicated by the FAA in their own publications, published hold over times (HOT’s) are guidelines for expected results only, and no legal limitation exists. The accident aircraft was operating on a normal planned schedule, and was unrelated to poor ADM, or any pressure to takeoff in dangerous conditions, as no dangerous conditions existed at that time.
During takeoff, the aircraft rotated normally at the correct speed, whereupon it immediately entered an inflight aerodynamic stall, and un-commanded roll to the right. The stall and roll sequence observed by ground witnesses is common to this aircraft type when taking off with contaminated surfaces, and has been well documented in the past on this type aircraft. The aircraft attained approximately 10 – 20 feet of total height above the runway surface and traversed to the right side of the runway, whereupon it descended with right wing low, and the right-wing tip impacted the ground. The crash sequence began from this first point of contact. The aircraft did not roll inverted on takeoff, rather it came to rest inverted after its right wing struck the ground and the breakup cartwheel sequence began, but only because of the wing tip strike. Fire consumed much of the cockpit and cabin almost immediately; there was no possible escape from the wreckage. The Probable Cause of this accident is clearly contaminated surfaces during takeoff, but the cause of the contamination remains undetermined. However, the cause is likely now limited to the failure of: 1) The FBO provided deice process to remove contaminants, or 2) the failure of the Type I fluid to be dispensed at the minimum temperature of 140°F minimum, or 3) The failure of the FBO to assure the proper 1:1 glycol/water ratio mix in the Type I tank, which assures that the delivered mix does not refreeze on contact, or 4) A failure of the of the FBO employee applicator to ensure that the Type IV fluid was completely and uniformly applied in order to consider the aircraft clean and covered, or 5) A highly unusual weather phenomena that occurred instantly at the runway such as ice pellets, that could not be observed by tower personnel, or perceived by the flight crew. Given the extremely low ambient temperature conditions near 0°F, all snow and falling precipitation would have been frozen, dry, and unable to adhere to any aircraft surface. Ice Pellets are physically impossible to have occurred occur at this temperature. The accident aircraft likely was in essence unintentionally “iced” in error during the Type I cleaning process by the FBO due to either faulty FBO equipment, or an untrained FBO employee, which resulted in an inappropriate Type I dilution being sprayed on the accident aircraft, essentially water. The aircraft was then covered with green Type IV 100% UCAR FlightGuard AD-49 anti-ice gel, so that the underlying clear thin ice was not visible during the cabin check of the wings by the accident crew prior to the accident takeoff sequence. A tactile wing inspection is not common or practical while holding short of the runway. As a policy, there are no crews that would disembark their aircraft while holding short and at the active runway in order to perform a tactile wing inspection just before takeoff, and no tactile wing inspections were conducted by any aircraft holding short that night.
Therefore, the DTSB finds the Probable Cause of this accident to be:
1) A combination of improper Type I fluid, (number 3 above) with
2) the applied thick gel like type IV anti-ice material still adhering to upper surfaces during takeoff and acting as a contaminant as well, in conjunction with
3) the overall lack of “any” Challenger 650 AFM guidance regarding increased Vr speeds and much slower rotation up into the V bars for takeoffs in icing conditions, with aircraft anti-ice systems on, or after deicing type IV fluid has been applied.
Due to the actual cockpit observation of very light snow conditions and tower reported RVR as greater than 6,000 feet, the accident pilots fully expected to be completely safe up to at least 30 minutes past the time that the final application of Type IV fluid began, and voiced that conclusion as recorded by the CVR. There is virtually no holdover time in place if contaminants are not falling from the atmosphere onto the aircraft. A tactile wing inspection is only required when deciding whether to de-ice or not. In this case, the crew had already decided to de-ice and a tactile wing inspection at the runway prior to takeoff was not required. The accident pilot did rotate up into the command bars within a degree of the 12 degree ANU default takeoff position, at a rate approximately commensurate of the recommended 3 degrees per seconds as he had successfully done on all previous uneventful takeoffs in this same aircraft.

NTSB: NONE

DTSB: The DTSB recommends that all operators and applicators of deicing and antiicing services review and ensure that proper Glycol dilutions, nozzle temperatures, and procedures are strictly followed for all De ice operations. The DTSB also recommends that all operators use a more robust Type IV fluid such as CHEMCO CHEMR NORDIK IV, listed as Table 31 in the FAA Guideline, yielding much longer Hold Over Times.

NTSB: NONE