Baltimore, MD, USA
TF-FII
Boeing 757-200
During the takeoff roll as the captain was about to call "eighty" knots, the first officer called "hundred." The captain noted that the standby airspeed indicator agreed with the first officer's and decided to continue the takeoff and address the anomaly of his airspeed indicator after takeoff. The pilots indicated that EICAS messages appeared and disappeared several times after takeoff and during the climb, including the messages MACH/SPD TRIM and RUDDER RATIO. Checklists for MACH/SPD TRIM and RUDDER RATIO messages did not mention an unreliable airspeed as a possible condition. The modifications associated with Boeing Alert Service Bulletin 757-34A0222 (and mandated by FAA Airworthiness Directive 2004-10-15 after the incident), which had not been incorporated on the incident airplane, would have provided a more direct indication of the airspeed anomaly. According to information in the Icelandair Operations Manual, these EICAS messages (in conjunction with disagreements between the captain and first officer airspeed indicators) may indicate an unreliable airspeed. Overspeed indications and simultaneous overspeed and stall warnings (both of which occurred during the airplane's climb from FL330 to FL370) are also cited as further indications of a possible unreliable airspeed. The crew did take actions in an attempt to isolate the anomalies (such as switching from the center autopilot to the right autopilot at one point during the flight). However, this did not affect the flight management computer's use of data from the left (captain's) air data system, and the erroneous high airspeeds subsequently contributed to airplane-nose-up autopilot commands during and after the airplane's climb to FL370. During the climb the captain's indicated airspeed began to increase, and the overspeed warning occurred. The first officer indicated that at this time his airspeed indication and the standby airspeed indication both decreased to about 220 knots and his pitch attitude felt high. Despite agreement between the first officer and standby airspeed indications and the pilots' belief that the captain's airspeed indicator was inaccurate, control was transferred from the first officer to the captain. Pitch attitude continued to climb and airspeed continued to decay after the captain assumed control. The airplane's pitch attitude became excessively high until the airplane's stick shaker activated and the airplane stalled. Although stall recovery was eventually effected and the airplane was leveled at FL300, the lack of appropriate thrust and control column inputs following the stall delayed the recovery. Evidence from the investigation indicates that anomalies of the captain's airspeed indicator were caused by a partial and intermittent blockage of the captain's pitot tube. The reason for the blockage was not determined.
HISTORY OF FLIGHT On October 19, 2002, about 2000 eastern daylight time (EDT) [or 0000 coordinated universal time (UTC)], a Boeing 757-200, TF-FII, operating as Icelandair flight 662, experienced a stall while climbing from flight level (FL) 330 (i.e., 33,000 feet) to FL 370. The flight lost about 7,000 feet during the recovery and then diverted to Baltimore-Washington International Airport (BWI), Baltimore, Maryland. There were no injuries to the 191 passengers or 7 crewmembers and no damage to the airplane. The airplane was being operated under the provisions of 14 Code of Federal Regulations Part 129 as a scheduled international passenger flight from Orlando International Airport (MCO), Orlando, Florida, to Keflavik International Airport, Keflavik, Iceland (KEF). The incident flight departed MCO about 1900 EDT; the first officer was the pilot flying (PF). According to Icelandair's Standard Operating Procedures (SOPs) and Boeing's 757/767 Flight Crew Training Manual, the captain (as the non-flying pilot) was responsible for calling out 80 knots during the takeoff roll. The captain indicated that about the time he was going to call out 80 knots, the first officer called out 100 knots. The captain indicated that he was going to abort the takeoff until he noticed that the first officer and the standby airspeed indicators were indicating the same airspeed (at this point, about 110 knots). He decided to allow the FO to continue with the takeoff, with the option of returning to MCO. The first officer indicated that during the takeoff, all of the parameters on his side were normal; therefore, he continued the takeoff. The pilots indicated that shortly after takeoff, the lateral and vertical flight director (FD) bars on the captain's display and lateral FD bar on the first officer's display disappeared. The first officer switched his flight director source from "right" to "center", but the problem remained and the first officer returned the switch to "right". In addition, after passing through about 1,000 feet, the advisory messages MACH/SPD TRIM and RUDDER RATIO appeared on the Engine Indication and Crew Alerting System (EICAS) display. The status message ELEV ASYM also displayed. (EICAS information includes systems alerts, maintenance information, and status messages.) The captain told the first officer to continue the climb and to deal with the messages later. After trimming the airplane and retracting the flaps, the first officer asked the captain for the After-Takeoff checklist and the Quick Reference Handbook (QRH) to address the EICAS messages. Subsequently, the EICAS messages disappeared, the FD bars returned, and the airspeed indications showed consistent readings. After climbing through about 10,000 feet, the same advisory and status messages again appeared on the EICAS, and the captain airspeed indication showed 10 knots lower than the first officer and the standby airspeed indications. A few minutes later, the EICAS messages disappeared, and the captain's airspeed indication again agreed with the first officer and the standby airspeed indications. The first officer indicated that the messages disappeared without any action by the flight crew. When the flight reached FL 330, the same messages and airspeed sequences once again occurred, and then everything returned to normal about two minutes later. The pilots indicated that they suspected that failure in the left Air Data Computer might have caused the captain's airspeed anomalies. However, they indicated that because no failure flags appeared on the captain's airspeed indicator, they decided not to switch captain's air data source to alternate. After a little over an hour into the flight, air traffic control (ATC) authorized a climb to FL 370. The climb from FL 330 was made at normal climb power, with the autothrottle and the autopilot engaged. During the climb the captain's indicated airspeed began increasing, and the overspeed warning occurred as the airplane neared FL 350. The first officer indicated that he did not remember what his airspeed indication was at that time. The pilots indicated that because of the previous airspeed anomalies, they felt that the overspeed warning was erroneous and they decided to pull circuit breakers to silence the aural overspeed warning. The captain stated that his airspeed indication reached a maximum of between 320 and 350 knots during the climb. The first officer indicated that during the climb his airspeed indication and the standby airspeed indication both decreased from about 250 to 220 knots. The first officer told the captain that he did not think that his airspeed indication was reliable and asked him to take control of the airplane. He stated that the captain promptly took control of the airplane. The first officer indicated that he did not remember the pitch attitude at this time but thought that it was less than 10 degrees. When asked why control was transferred from the first officer to the captain, despite their acknowledgement of anomalies with the captain's airspeed indicator and agreement between the first officer and standby airspeed indicators, the first officer indicated that he noticed that the airplane's pitch was unusually high and the airspeed had decreased substantially. Because he became unconvinced whether his instruments were correct, he asked the captain to assume control of the airplane. The captain indicated that he had a better view of the standby instruments, in case the first officer's airspeed indicator had become unreliable. Soon after the captain assumed control, the flight experienced activation of the stick shaker and then heavy stall buffet. The captain indicated that he then disconnected the autopilot and autothrottle. The captain indicated that he initiated the stall recovery by reducing the power to idle and lowering the nose about 5 degrees below the horizon. He indicated that he looked at the first officer and standby airspeed indications and that they were the same. The captain stated that "there was a lot of vibration" during the stall encounter, and both pilots acknowledged that they had never experienced anything like it before. The first officer indicated that the stall buffet felt a little bit different than what he had experienced during simulator training but that it felt the same in strength. Subsequent FDR analysis revealed that the stick-shaker continued for about 45 seconds. During the loss of altitude, the first officer radioed the urgency message PAN PAN, advising that they were unable to maintain altitude and were descending out of their cleared flight level. The flight crew received immediate clearance to descend FL 300 and then subsequently to FL 290. The captain then decided to divert to BWI. The pilots stated that they monitored their instruments during the descent to BWI. The captain indicated that his airspeed indication was 40 to 70 knots lower than the first officer and standby airspeed indications at times during the descent. After descending to FL 250, the pilots verified that the first officer and standby airspeed indications were the same (about 250 knots), and the first officer took control of the airplane and reengaged the autopilot. The captain indicated that at this time, his airspeed indication was 180 knots. The pilots further checked the captain's airspeed indication against ground speed values provided by ATC to determine the erroneous nature of the airspeed indication. The flight landed at BWI about 2100 EDT. PERSONNEL INFORMATION Captain The captain has been employed by Icelandair since 1986. His total flight time prior to the incident was around 8,500 hours, including about 1,020 hours as B-757 pilot-in-command (PIC). He previously served as captain with Icelandair on the Fokker 50 and as first officer on the B-757. The captain completed training (as a captain) for his B-757 type rating in May 2001. During his training, he demonstrated approaches to stall in the clean configuration (with terrain not a factor) and in the landing configuration (with terrain a factor) and also conducted a recovery from a full stall. The captain demonstrated these maneuvers in his most recent company proficiency check in April 2002. The captain held a first-class medical certificate, dated May 7, 2002, with no waivers. The first officer stated that he had flown with the captain on three previous occasions. He characterized the captain as having very good situational awareness. He stated that the captain was calm, practiced crew resource management (CRM), and was a good commander. On October 16, 2002, the captain flew a round trip from KEF to London and was off-duty on the following day. On October 18th, the captain flew from KEF to MCO and arrived about 2100. He stated that he had a good night's sleep in Orlando and that he awoke about 0700 on October 19th. He added that he later took a 2-hour nap and departed the hotel at 1730. The flight departed MCO for KEF about 1900. During interviews with Safety Board personnel following the incident, the captain indicated that the stall recovery procedure he used was the procedure taught to him during simulator training. He stated that he was taught that if there was enough altitude, the pilot should reduce power and lower the nose. He was taught that at lower altitudes, the pilot should use full thrust with 5 degrees nose-up pitch. He stated that he received stall training during his proficiency check in April 2002. He stated that there were no procedures in company manuals for pulling the circuit breaker on the cockpit voice recorder (CVR) following an incident. He added that he was not trained on postincident landing procedures. The captain further indicated that he did not initially increase thrust during the stall recovery because high thrust can increase nose-up tendencies and make it more difficult to decrease the airplane's angle of attack. First Officer The first officer has been employed by Icelandair since 1997. His total flight time prior to the incident was about 4,100 hours. His flight time on the B-757 was about 1,800 hours and was all as first officer. During company proficiency checks in April 2000 and May 2002, the first officer demonstrated approaches to stall in the clean configuration (with terrain not a factor) and in the landing configuration (with terrain a factor). The first officer's attended recurrent ground school training in October 2002. He had three days off prior to the trip to MCO. The first officer held a first-class medical certificate, dated May 7, 2002, with no waivers. The captain stated that he thought he had flown with the first officer on two previous occasions, the last time being on August 31, 2002. He characterized the first officer as very professional and as someone who always tried to do his best. The first officer stated that he always followed the checklists. He stated that he was taught stall recovery for incidents in which terrain is not a factor during simulator training. He stated that for an overspeed warning, pilots are taught to disengage the autopilot, autothrottle, and flight director; check all possible sources of airspeed; and then attempt to maintain normal attitude, pitch, speed, and thrust settings. The first officer stated that he performed approaches to stall in the clean and landing configurations, with and without terrain as a factor, during his May 2002 training. The first officer stated that the recovery procedures for an approach to stall called for applying maximum thrust, maintaining configuration, then pitching up to the eyebrow on the primary attitude display and allowing speed and altitude to increase. AIRCRAFT INFORMATION General The incident airplane, serial number 24760, was manufactured on March 5, 1990 and delivered to Icelandair on May 3, 1990. It was powered by two Rolls Royce RB211-535E4 turbofan engines. Daily and ETOPS checks were carried out by maintenance at MCO. No open discrepancies and no entries related to erroneous airspeed indications were noted in the maintenance log before the incident flight. A check of the maintenance records revealed no sign of erroneous airspeed indications prior to the incident. Icelandair indicated that pitot covers were most likely not used while the incident airplane was parked at MCO and that this might have allowed insects to enter the captain's pitot tube. Air Data System The B-757 air data system consists of a pitot-static system (the pitot static system consists of one left [captain] and one right [first officer] pitot tube, one right auxiliary and one left auxiliary pitot tube, and six static ports); one temperature probe; two angle-of-attack probes; two air data computers (ADC); and electric flight instruments. The system provides pitot and/or static pressure information to various flight instruments and airplane systems. The two ADCs use sensed air data to provide input signals to certain flight instruments, including the mach/airspeed and standby airspeed indicators and the altimeter and standby altimeter indicators. The left ADC provides information to the captain's instruments, and the right ADC provides information to the first officer's instruments, although the opposite ADCs are available as alternate air data sources. If the ADC detects a fault or stops transmitting valid air data signals, warning flags appear on the air data instruments. The left and right ADC data buses can be switched by the air data source select switches in the cockpit. Crew statements and FDR data indicate that the switches remained in their normal positions throughout the flight. With the switches in the normal positions, the data recorded on the FDR are from the same ADC supplying the captain's instruments. Each mach/airspeed indicator displays airspeed, mach, and Vmo (maximum operating airspeed) from the selected ADC. The standby airspeed indicator is installed along the left side of the center control panel. The instrument is connected directly to the right auxiliary pitot and the alternate static ports. ADC Inputs to Flight Control and Flight Management Computers Each of the B-757's three flight control computers (FCCs) receives air data from both the left and right ADCs. The source of air data utilized by the FCCs is dependent upon the autopilot or flight director engagement configuration. The FCCs will utilize air data from the right ADC if the right FCC is engaged first or if only the first officer's flight director is switched on. Otherwise, the FCCs will utilize data from the left ADC. During the altitude hold, flight level change, and vertical speed autopilot pitch modes, the FCCs generate pitch commands using ADC information. For VNAV modes, the FCCs receive VNAV steering commands directly from the Flight Management Computer (FMC). The FMC receives air data from both ADCs and selects the left ADC as the primary source. During a VNAV climb, the FMC generates pitch steering commands to control the airspeed to the FMC target speed. With the autothrottle engaged, the FMC requests the autothrottle to control thrust to the target thrust setting (climb thrust). VNAV will command an increase of the pitch attitude to manage excess airspeed until the FMC target airspeed is reached or a 15 degree pitch attitude limit is reached. During VNAV PATH mode the FMC generates pitch steering commands to control the airplane to the FMC target altitude, while the autothrottle manages the thrust to control airspeed to the FMC target speed. When the flight directors are engaged, the pitch commands for the engaged mode are presented to the pilot via the flight director bars. The flight director bars provide commands to lead the pilot to the desired path. After the flight had leveled at FL330, the crew switched from the center autopilot system to the right autopilot system; this was maintained until the autopilot was disconnected during the stall encounter at FL370. The crew indicated that they made the switch to the right autopilot system because they had thought it would use data from the right ADC and FMC instead of possible erroneous data from the left ADC and FMC. B-757 Engi
The captain's improper procedures regarding stall avoidance and recovery. Contributing to the incident were the partial blockage of the pitot static system, and the flight crew's improper decisions regarding their use of inaccurate airspeed indications. Contributing to the flight crew's confusion during the flight were the indistinct alerts generated by the airplane's crew alerting system.
Source: NTSB Aviation Accident Database
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