Truckee, CA, USA
N605TR
BOMBARDIER INC CL-600-2B16
The captain and first officer (FO) departed on a non-revenue flight operating under instrument flight rules with four passengers bound for Truckee, California. Most of the flight was uneventful. During the descent, air traffic control (ATC) told the flight crew to expect the area navigation (RNAV [GPS]) approach for runway 20. The captain (pilot flying [PF]) stated and the FO (pilot monitoring [PM]) calculated and confirmed that runway 20 was too short for the landing distance required by the airplane at its expected landing weight. Instead of making a request to ATC for the straight-in approach to runway 11 (the longer runway), the captain told the FO they could take the runway 20 approach and circle to land on runway 11, and the FO relayed this information to ATC. ATC approved, and the flight crew accepted the circle to land approach. Although the descent checklist required that the flight crew brief the new circle to land approach, and the flight crew’s acceptance of the new approach invalidated the previous straight-in approach brief, they failed to brief the new approach. ATC instructed the flight crew to hold, but the captain was slow in complying with this instruction, so the FO started the turn to enter the holding pattern and then informed ATC once they were established in the hold. About 20 seconds later, ATC cleared them for the approach. Before the FO confirmed the clearance, he asked the captain if he was ready for the approach, and the captain stated that he was. The FO subsequently commented that they had too much airspeed at the beginning of the approach and then suggested a 360° turn to the captain, but the captain never acknowledged the excessive airspeed and refused the 360° turn. After the FO visually identified the airport, he told the captain to make a 90° right turn to put the airplane on an approximate heading of 290°, which was parallel to runway 11 and consistent with the manufacturer’s operating manual procedures for the downwind leg of the circling approach. However, the FO instructed the captain to roll out of the turn prematurely, and the captain stopped the turn on a heading of about 233° magnetic, which placed the airplane at an angle 57° left of the downwind course parallel with runway 11. As a result of the early roll-out, the flight crew established a course that required an unnecessarily tight turning radius. When they started the turn to final, the airplane was still about 1.3 nautical miles (nm) from the maximum circling radius that was established for the airplane’s approach category. The FO also deployed flaps 45° after confirming with the captain (the manufacturer’s operating manual procedures for the downwind leg called for a flaps setting of 30°, but the manufacturer stated that a flight crew is not prohibited from a flaps 45° configuration if the approach remains within the limitations of the airplane’s flight manual). The airplane’s airspeed was 44 kts above the landing reference speed (Vref) of 118 kts that the flight crew had calculated earlier in the flight; the FO told the captain, “I’m gonna get your speed under control for you.” The FO likely reduced the throttles after he made this statement, as the engine fan speeds (N1) began to decrease from about 88% to about 28%, and the airplane began to slow from 162 kts. After the FO repeatedly attempted to point out the airport to the captain, the captain identified the runway; the captain's difficulty in finding the runway might have been the result of reduced visibility in the area due to smoke. The FO continuously reassured and instructed the captain throughout the circle to land portion of the approach. On the base leg to the runway and about 25 seconds before impact with the ground, the FO started to repeatedly ask for control of the airplane, but neither flight crewmember verbalized a positive transfer of control as required by the operator’s general operating manual (GOM); we could not determine who had control of the airplane following these requests. As the airplane crossed the runway extended centerline while maneuvering toward the runway, the FO noted that the airplane was too high. One of the pilots (recorded flight data did not indicate which) fully deployed the flight spoilers, likely to increase the airplane's sink rate. (The flight spoilers are deployed using a single control lever accessible to both pilots.) The airspeed at the time was 135 kts, 17 kts above the Vref based on the erroneous basic operating weight (BOW) programmed into the airplane’s flight management system (FMS). About 7 seconds later, the left bank became steeper, and the stall protection system (SPS) stick shaker and stick pusher engaged. The captain asked the FO, “What are you doing,” and the FO again asked the captain multiple times to “let [him] have the airplane.” The stick shaker and stick pusher then briefly disengaged before engaging again. The airplane then entered a rapid left roll, consistent with a left-wing stall, and impacted terrain. A postcrash fire consumed most of the wreckage. Analysis of data retrieved from the flight data recorder (FDR) indicated that the engines were functioning normally at the time of impact and there were no indications of a flight control or system malfunction. Most of the wreckage was consumed by postcrash fire, and the flight control linkages were destroyed either by high energy impact forces or the postcrash fire, which precluded a complete examination of the wreckage. Examination of the primary flight control surfaces did not reveal any preimpact mechanical anomalies. Engine data from the accident flight did not show any interruptions in power or suggest any mechanical anomalies with the power production capabilities of either engine. Flight Crew Performance The captain and FO were appropriately qualified to perform their respective duties as pilot in command (PIC) and second in command of the accident flight, which was the first pairing of this crew for the operator. A review of operator documentation revealed that the flight complied with the requirements of Title 14 Code of Federal Regulations (CFR) Part 91, General Operating and Flight Rules, and was not conducted under the operator’s 14 CFR Part 135 certificate. Although toxicology testing detected ethanol in the FO’s tissue, given the different concentrations of ethanol, the presence of n propanol, and the state in which the body was found, it is likely that the identified ethanol was from sources other than ingestion. The flight crew elected to conduct a circling approach to runway 11 and never asked ATC for the straight in RNAV (GPS) approach to the desired runway. The crew also failed to brief the new circling approach after previously briefing the anticipated straight in approach. The flight crew’s failure to brief the circling approach prevented them from sharing a mental model for how the approach should have been conducted and points to poor crew resource management (CRM) because they failed to prepare for adverse situations and contingencies, such as a missed approach. Because of their lack of preparation, they made critical errors on the approach that reduced the safety margin, which included: o flying the circling approach at a higher airspeed than the upper limit specified for the airplane’s category C approach category; o failing to establish the airplane on the downwind leg of the circle to land approach; and o failing to visually identify the runway early in the approach, likely due to obscuration by smoke. The airplane’s higher airspeed reduced the flight crew’s time to configure the airplane, assess their position relative to the runway, and make corrections to their trajectory, which further reduced the safety margin. During the approach, the FO made several announcements to the captain that the airplane was fast. The captain rejected the FO’s suggestion to take a 360° turn early in the approach, which would have provided additional time and distance for speed control. The circling approach maneuver began at 160 kts, which was 20 kts higher than the upper limit of the circle to land approach speed established for this airplane’s approach category (category C) and did not drop below the category C maximum speed until the flight crew was preparing to start their base leg turn. The captain’s failure to establish the airplane on the downwind leg and the airplane’s proximity to the airport during the approach also reduced the safety margin by limiting the space available to align the airplane with the runway centerline. The captain did not establish the airplane on a downwind leg parallel to the destination runway, as depicted in the manufacturer’s operating manual, but instead flew a downwind leg that converged on the runway centerline. This tightened the pattern and resulted in an overshoot of the runway centerline only 0.8 nm from the runway threshold during the base-to-final turn, limiting the flight crew’s ability to properly align the airplane with the runway centerline for final approach. The FO received updated weather information from an automated weather observation system (AWOS) early in the approach, which included an advisory of reduced visibility due to heavy smoke in the area, but he did not relay this visibility advisory to the captain, further reducing the safety margin. The smoke likely made it more difficult for the captain to visually identify the airport. The FO reassured the captain throughout the approach about needing to be patient and having plenty of time (despite the time constraints resulting from the fast and tight circling maneuver). These reassurances demonstrated that the FO was aware of the adverse effects of self-induced pressure to perform; however, he exhibited self-induced pressure to salvage a deteriorating approach. In addition, despite the captain not properly setting up the approach, he failed to ask for more time in the holding pattern and rejected the FO’s suggestion to use a 360° turn to slow the airplane. Without any external pressure to land immediately, the captain’s actions indicated a self-induced pressure to perform without being corrected. Following the turn to the base leg, the airplane was not in a position from which it could align with the runway without overshooting the centerline, nor could the pilots execute a normal descent to the runway. Further, the airspeed was not on target or approaching the flight crew’s target Vref of 118 kts. The stabilized approach criteria in the operator’s GOM required that the airplane be in a position to execute a normal descent to the runway and that the airspeed be on target or approaching target no later than 500 ft above field elevation in visual meteorological conditions (VMC). The accident approach did not meet those criteria and was therefore unstabilized. Once the approach became unstabilized, the crew should have abandoned the approach and gone around but did not. The operator’s GOM empowered both pilots to perform a go around, and the circumstances of the approach did not preclude a go around; there was no time- or fuel related pressure to land. Even so, the flight crew never announced a go around, and the FO did not make callouts for going around as required in his role as PM (as the PM, it would have been the FO’s duty to call for a go around once the operator’s stabilized approach criteria were violated). The flight crew’s choice to continue the unstabilized approach rather than go around was consistent with self induced pressure to perform and degraded decision making. About 8 seconds after the FO asked for control of the airplane the first time, he said, “We’re gonna go through it and come back okay?”, likely referring to the runway centerline, and indicating an intent to salvage the unstable approach. As the airplane crossed the centerline, the captain said, “It’s here” (also likely referring to the centerline), and the FO responded, “Yes yes it’s here we are very high,” indicating that he was aware that the airplane was not in a position to make a normal descent to the runway. At the same time, the spoilers were deployed. Given the FO’s stated intent to overshoot the runway centerline and then return to it and his recognition that they were high, it is likely that the FO deployed the spoilers in an attempt to descend quickly toward a nominal glidepath to the runway. Once the airplane crossed the extended runway centerline, it approached a stall and the stick shaker engaged; the FO again requested control of the airplane multiple times, likely motivated by a desire to continue the approach. However, the cockpit voice recorder (CVR) did not record a positive transfer of control or any indication that the captain had relinquished control to the FO. The FO had acted as an instructor to the captain throughout the flight; seeing himself in this role might have driven his desire to take the controls in the final moments of the flight. Given the FO’s clear motivation to continue the approach and his multiple requests for control of the airplane, it is likely that he improperly attempted to take control of the aircraft without permission from the captain and increased the bank angle of the left turn, which contributed to the left wing’s stall. In his leadership position as PIC, the captain should have taken decisive action to exercise his authority to ensure airplane control when the FO likely improperly attempted to take control; however, he failed to do so. In addition, both the FO’s decision to attempt to salvage the unstabilized approach and the captain’s failure to intervene demonstrated degraded performance and vigilance. Further, during the final 10 seconds of the flight, the CVR captured reactive statements from both crewmembers, including the FO’s multiple requests for control of the airplane, that suggest they were not working together. The captain's lack of assertiveness in exercising his authority, each flight crewmember’s failure to recognize their own psychological stresses, and the flight crew's disregard for safety while attempting to salvage the approach all point to improper CRM in the final moments of the accident flight. Failures in CRM generally describe a lack of clear communication and a failure to recognize degraded performance and vigilance in the cockpit. In this case, poor CRM contributed to the flight crew’s degraded performance and competition for control of the airplane, ultimately resulting in a stall. Airplane Performance Examination of paperwork for previous maintenance done on the airplane established that the weight and balance information was incorrect in the airplane’s FMS. About 10 months before the accident, a maintenance facility serviced the airplane’s FMS units to comply with a scheduled battery replacement. Although the maintenance facility reinstalled the required databases, which included the approach speeds and performance databases, it did not input a weight specific to the accident airplane. As a result, the airplane had likely been operating with an incorrect empty weight since the maintenance; the operator reported flying the airplane for four flights since the operator took possession of it in May 2021. The default empty weight in the FMS was about 3,000 lbs lighter than the estimated actual airplane empty weight for the accident flight. Because of the inaccurate empty weight, the FMS had computed for the flight crew an erroneous Vref of 118 kts, which was 6 kts slower than the correct reference landing speed of 124 kts. Although this oversight showed a lack of attention to detail by the operator, an airplane performance study determined that the weight and balance discrepancy did not contribute to the stall because the airplane was flying several kts above the correct reference speed in its final moments. The performance study and accident data revealed that the full deployment of the flight spoilers about 12 seconds before the accident had a significant effect on the stall margin of the airplane in the final moments before impact. Performance analysis showed that the airplane would have been at a bank angle of about 36° when the stick shaker engaged at a calibrated airspeed of 130
HISTORY OF FLIGHTOn July 26, 2021, about 1318 Pacific daylight time, a Bombardier Inc. Challenger 605, N605TR, was destroyed when it was involved in an accident near Truckee Tahoe Airport (TRK), Truckee, California. The captain, FO, and four passengers were fatally injured. The airplane was operated as a Part 91 personal flight. According to automatic dependent surveillance broadcast (ADS-B) data, the nonrevenue flight operating under instrument flight rules departed Coeur d'Alene Airport - Pappy Boyington Field (COE), Coeur d’Alene, Idaho, about 1145 for TRK. (All times in this report are referenced to the airplane’s FDR clock unless otherwise indicated. The ADS-B clock was 1.625 seconds behind the FDR clock and has been shifted by 1.625 seconds in this report.) CVR data indicated that about 1155, ATC cleared the flight to 37,000 ft mean sea level (msl) where it remained for the rest of the cruise phase of the flight. About 1220, the captain started the approach briefing for the RNAV (GPS) approach for runway 11 at TRK with the FO. At 1248, ATC began issuing descent instructions for the airplane’s approach into TRK. At 1249:31, the FO received the updated weather observations for 1251 from the AWOS at TRK, which included an advisory of “visibility may be different than what is shown on AWOS due to heavy smoke in the area.” However, when the FO subsequently relayed the weather to the captain, he did not include the smoke advisory. At 1251:22, the FO informed the captain, “New numbers are sent… eighteen, twenty-nine, forty-five” (referring to a Vref speed of 118 kts, approach climb speed of 129 kts, final segment speed of 145 kts). During this time, the CVR recorded the captain asking the FO for the descent checklist twice before the FO initiated the checklist. The flight crew stated they had completed the approach briefing for the RNAV (GPS) approach for runway 11 about 1252. At 1255, the FO asked ATC if they could proceed direct to the waypoint ALANT for the RNAV (GPS) approach for runway 11 at TRK and the controller cleared them as requested. About 1258, as the airplane descended below 26,000 ft msl, ATC informed the flight crew that they could expect the RNAV (GPS) runway 20 approach at TRK. The captain informed the FO that runway 20 was too short and that they “cannot accept that,” and added that the runway 20 approach would require them “to circle to land” for runway 11. The FO then computed the required landing distance and concluded that runway 20 was “4,655” ft long (4,654 ft according to the TRK airport chart) and they required a minimum landing distance of 4,600 ft. The captain noted that the margin was “too tight,” and the FO agreed. At 1259:57, the captain told the FO they could make the approach into runway 20 and circle to land. Fifteen seconds later, the FO informed ATC that they could take the runway 20 approach but would need to circle to runway 11 because they needed the longer runway. The controller approved their request and told them to plan on the circling approach, then told them to expect some delays. The flight crew did not brief the new approach, which was required by the descent checklist because the flight crew had changed their approach after briefing the original approach. At 1302:54, the FO asked the controller if they should enter the published hold at AWEGA waypoint, but the controller instructed the flight crew to expect a hold at waypoint ALVVA, an initial approach fix (IAF) west of AWEGA. The FO then asked for and was given a clearance and instructions to hold at ALVAA. When the airplane was about 11 nm southeast of waypoint ALVVA, the FO told the captain he would start the turn for him toward the waypoint and did so. The FO then helped the captain program the hold into the FMS. At 1311:43, ATC cleared the flight for the RNAV (GPS) runway 20 approach. After the FO asked and the captain confirmed that he was ready for the approach, the FO provided an abbreviated readback of the clearance. At 1312:13, the FO asked the captain, “Are you gonna be able to get down?” According to the ADS-B data, the airplane was at an altitude of 15,725 ft msl at the time and the first altitude of the approach was 12,000 ft msl at AWEGA, about 3.5 nm away. At 1312:39, the FO then stated to the captain, “We’ve got a ways to go,” and added, “You got plenty of time.” About this time, FDR data showed the airplane’s indicated airspeed was at 241 kts. At 1313:24 the FO said, “We gotta get this thing slowed down,” then asked if the captain wanted “a right three sixty [degree turn],” but the captain declined. The airplane was about 3 nm south of AWEGA, heading toward OSTIE waypoint at an airspeed of about 252 kts (OSTIE is about 2 nm north of LUMMO, the final approach fix [FAF]) (see the locations of flight crew comments and waypoints in figure 1 below). Figure 1. Airplane flightpath and crew discussion on runway 20 approach At 1313:41 the captain instructed the FO, “Now just below two fifty give me flaps twenty please”; however, the FO responded, “Below two-fifty? how about below two-thirty?” (consistent with the published flap speeds of 231 kts in the manufacturer’s operating manual that were also placarded in the airplane), and the captain agreed. The FO then stated again that they should start slowing down the airplane. A few seconds later, the controller terminated radar services and asked the flight crew to contact Truckee tower. At 1314:15, when the airspeed was about 228 kts, the captain again asked the FO to deploy flaps 20°, which the FO stated had been selected (and FDR data showed the flaps setting was selected 4 seconds later). About the same time, the FO contacted Truckee tower and informed them that they were passing the FAF inbound (which ADS-B data confirmed) and would circle to runway 11. The tower acknowledged the communication and asked them to report when the airport was in sight. The captain asked the FO to deploy the landing gear, then the FO responded, “… You came off… what are you… ah nevermind,” and then said, “How ‘bout gear down flaps thirty before landing checklist.” The captain then asked the FO again to deploy the landing gear. At 1315:20, the flaps were at 30° and the landing gear was down when the captain asked for “flaps, thirty please” and the FO responded, “No, we’re at flaps thirty, gear down.” The captain then immediately restated, “Flaps thirty.” About 15 seconds later, the captain asked the FO to confirm the airport’s location on the left. The FO confirmed the airport's location then added, “We’re gonna have to make a right hand turn to get to it,” and the captain acknowledged him. At 1315:55, the FO stated the airport was 5 miles away. At 1316:20, the FO deployed full flaps (45°) after confirming with the captain. A second later (near YAKYU waypoint), the FO said, “There’s the airport,” told the captain to make a 90° right turn, and contacted Truckee tower, which cleared the airplane to land. The FO attempted to point out the airport to the captain, and the captain asked “where?” twice. At 1316:43, the FO told the captain to roll out (level the wings, stopping the turn) and turn the autopilot off. The airplane was at the beginning of the downwind leg turn (about 213° magnetic) when the FO told the captain to roll out, and the airplane rolled out on a heading of about 233°. Figure 2 depicts the turns taken by the airplane in the approach and the maximum circling radius of 3 nm allowed for category C aircraft at TRK in the airport’s approach charts (the airplane was at least 1.3 nm from that maximum circling radius). Figure 2. The airplane’s downwind leg and allowed circling radius. At 1316:53, the FO told the captain, “I’m gonna get your speed under control for you.” FDR data indicated the airplane’s airspeed was about 162 kts at this time. FDR data showed that the airplane began to slow after the FO made this statement. At 1316:56, the captain stated, “Oh I see the runway,” when the airplane had already started the circling approach to runway 11. Two seconds later, the FO told the captain that he could start descending, and the captain replied, “’Kay, full flaps.” The FO replied, “You do have full flaps,” and then stated, “Patience patience patience you got all the time in the world”; 13 seconds later, he stated, “You are looking very good my friend.” At 1317:24, the airspeed was about 123 kts and the airplane was on a west heading about 1.5 nm from the approach end of runway 11 when the FO told the captain to “bring that turn around,” then the airplane began a left turn toward the runway. At 1317:46, as the airplane was turning through a heading of 188°, the FO made the first of several requests for control of the airplane, asking the captain, “Let me see the airplane for a second.” Eight seconds later, the FO told the captain, “We’re gonna go through it [the runway centerline] and come back [to the centerline] okay?” and the captain acknowledged the FO. About 1317:59, when the airplane flew through the runway 11 extended centerline about 0.8 nm from the runway threshold, FDR data showed that the flight spoilers were fully deployed (40°). At the time, the airspeed was 135 kts, and the N1 had reduced from about 60% rpm to about 28% rpm. At 1318:01, the FO said, “We are very high” (the airplane was about 6,390 ft msl, or about 489 ft above the runway 11 threshold elevation of 5,901 ft msl). At 1317:59, the airplane began a left turn that reached a bank angle of 36° about 4 seconds later. According to the CVR data, the stick shaker engaged at 1318:04, then the captain asked, “What are you doing,” which was followed by a stall warning sound. The airplane was on a south heading about 0.75 nm from the runway threshold as it continued to turn back toward the extended runway centerline (see figure 3). The stick pusher engaged about 1318:05. (For more information about the stick shaker and stick pusher, see the section below about the SPS.) The captain again asked the FO, “What are you doing?” and the FO then asked the captain three times over 2 seconds to “let me have the airplane.” The stick pusher disengaged at 1318:07 followed immediately by the stick shaker disengaging. At 1318:09, the stick shaker engaged again followed immediately by the stick pusher engaging, and the airplane was about 6,075 ft msl on a southeasterly heading when it entered a rapid left roll. The airplane was in a 111° left wing low bank angle at 1318:11 and 1 second later it was in a 146° right wing low bank angle and an approximate 30° nose low attitude, just before the airplane impacted terrain and a postcrash fire ensued. Figure 3. Accident airplane’s flightpath during final approach after crossing the runway centerline. Surveillance video from a business located along the airport perimeter captured the airplane in its final moments. At 1318:09 (according to the time captured by the recording device), the airplane was in a descending left turn on a southeasterly heading at a low altitude. About 1318:12, it entered a rapid left roll and disappeared below the tree line, and smoke appeared in the same location 5 seconds later. PERSONNEL INFORMATIONCaptain The captain, who had signed an employment contract with the operator but was not yet an employee at the time of the accident, was operating the flight under contract to the operator until he could be onboarded. A review of training records from the captain’s training provider showed that the captain, who was the PF and PIC during the accident, completed his most recent proficiency training as PIC in a Challenger 605 simulator 10 days before the accident flight. This most recent ground training included CRM training, and the captain’s overall rating for ground training was proficient. Records showed that the captain passed his checkride, which included a non precision approach, stall prevention, and a go around/rejected landing; however, the instructor comments for the practice simulator sessions noted that he rushed checklists, needed to slow down and read the checklist requirements, and needed to setup approach procedures without PM prompts. The captain also enrolled online for the accident flight operator’s basic indoctrination training, which included instruction on the flight operator’s GOM, 12 days before the accident flight. Federal regulations do not require any leadership and command training for Part 91 or Part 135 operations, and the captain had not taken any leadership training. However, according to both 14 CFR 91.3(a) and the flight operator’s GOM, the captain as PIC would have been “directly responsible for, and is the final authority as to, the operation of” the accident airplane. First Officer The FO, who was the PM and second-in-command during the accident flight, was not the accident operator’s employee at the time of the accident and had been hired as a contract pilot for the accident flight. The flight was the first pairing of this crew with the operator. A review of training records from the FO’s training provider showed that the FO completed a simulator session in a Challenger 604 in May 2021 and completed Challenger 604 recurrent training as PIC in June 2021. The recurrent training program included 15 hours of ground training and 8 hours of simulator training, which were split evenly as the PF and PM with five non precision approaches and one circle to land approach. The simulator training sessions included CRM, in which the FO was rated proficient. The FO’s training was not specific to the operator’s policies and procedures and the FO did not receive training on the operator’s GOM. According to Federal Aviation Administration (FAA) Order 8900.1, Volume 5, Chapter 2, Section 19, the accident airplane, a Challenger 605, was under the same type rating designation as the Challenger 604. AIRCRAFT INFORMATIONFlight Management System The airplane was equipped with a triple FMS, including three control display units in the cockpit, and three flight management computer (FMC) units in the underfloor avionics equipment bay. The flight crew used the control display units to input, modify, and execute flight plans; calculate airplane performance; and determine the airplane’s approach speeds (including Vref), maximum landing weight, and landing field length. The year before the accident, a maintenance facility serviced the airplane’s FMC units to comply with a scheduled battery replacement. Servicing the FMC units involved removing the FMCs from the aircraft, sending them to a third-party repair facility, and subsequently reinstalling them in the aircraft. Bombardier’s (the airplane manufacturer’s) maintenance manual instructed owners to “make sure that the default values and BOW value are appropriate for the aircraft” after reinstalling the FMC. According to the maintenance facility, it reinstalled the FMCs and the required databases, which included the approach speeds and performance databases, but did not input the BOW specific to the accident airplane. During subsequent testing, the manufacturer of the FMS confirmed that the BOW defaults to 24,000 lbs after battery replacement and reinstallation of the databases. The FMC manufacturer also confirmed that the installation of the databases did not prompt the user to enter a BOW. Flight Spoilers The airplane was equipped with flight spoilers that provided lift dumping and speed control while airborne. A flight spoiler control lever on the center pedestal allows the pilot to select variable amounts of flight spoiler deployment up to a maximum of 40°. An amber caution message is posted on the engine indicating and crew alerting system if the flight spoilers are deployed in flight and another condition is met, such as an altitude between 10 and 300 ft above ground level (agl); the left or right N1 is greater than 79%; or, if radio altitude is not available, any time the landing gear is extended. Stall Protection System According to a technical memorandum prepared by Bombardier, the natural stall characteristics of its Challenger 600 series airplan
The first officer’s (FO’s) improper decision to attempt to salvage an unstabilized approach by executing a steep left turn to realign the airplane with the runway centerline, and the captain’s failure to intervene after recognizing the FO’s erroneous action, while both ignored stall protection system warnings, which resulted in a left-wing stall and an impact with terrain. Contributing to the accident was the FO's improper deployment of the flight spoilers, which decreased the airplane's stall margin; the captain’s improper setup of the circling approach; and the flight crew’s self-induced pressure to perform and poor crew resource management, which degraded their decision-making.
Source: NTSB Aviation Accident Database
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