N357NW

The pilot induced oscillations and the delay in aborting the takeoff. Factors associated with the accident were the first officer used an improper trim setting and the captain did not identify and correct the setting during the taxi checklist, and the wet runway conditions.

The Airbus A320 contacted the runway and the terrain during takeoff on runway 3C (8,500 feet by 200 feet, wet) at the Detroit Metropolitan Wayne County Airport. An emergency evacuation was made during which time the emergency evacuation slide on the 2 left (2L) door failed to deploy. The captain reported that during the initial takeoff run, he held half forward pressure until reaching 80 knots. He reported that up to this point, everything was normal. He stated he released forward stick pressure by about 100 knots and the nose of the airplane began lifting off the ground with neutral stick, which was not normal. He reported he applied about half forward stick and the nose came back down. He reported that at 120 knots the nose again began to rise with one half to one quarter stick input. He then pushed the stick forward to the forward stop and the nose came up at a rapid rate. The captain reported that his attention was focused outside the airplane and he did not hear the first officer call V1. He reported that he felt the airplane was going to stall so he pulled the power off and aborted the takeoff. The captain stated that he was trained not to perform high-speed aborted takeoffs, but he felt the airplane would have been uncontrollable if the takeoff continued. The captain stated the thrust reversers were deployed and he initially thought there was enough runway remaining to stop. He assumed the autobrakes activated, but he pressed on the brakes anyway. He reported the airplane was not decelerating and it departed the end of the runway at a high speed. The captain reported that deceleration was rapid once the airplane departed the paved surface and the engines flamed out during the ground roll. Post accident inspection of the airplane revealed the horizontal stabilizer trim was set to negative 1.7 (units of trim), when it should have been set at positive 1.7. The first officer stated he set the trim while on the taxiway. The captain did not notice the improper trim setting during the cross check which was part of the taxi checklist. Further investigation revealed the operator procedures were to set the trim using units instead of percentage of mean aerodynamic chord as recommended by the manufacturer. In addition, it was discovered that the manner in which the units of trim were displayed on the trim control wheel, on the electronic centralized aircraft monitoring system (ECAM), and in the aircraft communications addressing and reporting system (ACARS) were not consistent. As a result the Safety Board issued Safety Recommendations A-02-06 and A-02-07. Post accident examination of the 2L slide/raft that did not deploy revealed an improper chamfer on the telescopic girt bar which attaches the slide/raft to the airplane structure. This allowed the slide/raft to detach from the airplane when the 2L door was opened. As a result the Safety Board issued Safety Recommendations A-01-27 and A-01-28. Being a fly-by wire airplane, the Airbus A320 has twosources of control lag in the pitch control. One is the latency between the pilot's input and the elevator movement through the elevator aileron control (ELAC) computer and the other is the rate limit of the elevator. Examination of the digital flight data recorded data for this accident revealed the pilot changed the pitch input faster than the elevator system would respond and saturation occurred in the rate at which the elevator surface could respond to the inputs. This resulted in pilot inducted oscillations (PIO) during the takeoff roll.

HISTORY OF FLIGHT On March 17, 2001, at 0705 eastern standard time, an Airbus Industrie A320-200, N357NW, operated by Northwest Airlines (NWA) as Flight 985, contacted the runway and the terrain during takeoff on runway 3C at the Detroit Metropolitan Wayne County Airport, Detroit, Michigan. The airplane received substantial damage. Three passengers reported minor injuries. The captain, co-pilot, 4 flight attendants, and 144 passengers were not injured. The 14 CFR Part 121 flight was operating in instrument meteorological conditions and an IFR flight plan was filed. The flight was originating at the time of the accident and the intended destination was Miami, Florida. The captain stated that when he reported on the morning of the accident, he completed his paperwork then went to the airplane where he performed the captain's "flow", checked maintenance records, briefed the flight attendants, and loaded the flight plan into the multifunction control display unit (MCDU). He stated they received the load data five to six minutes before they pushed back and it was entered into the flight management guidance computer (FMGC). The V-speeds were also set while at the gate. He stated that it was snowing so he had the first officer arrange to have the airplane deiced. The captain stated the first officer set the stabilizer trim prior to reaching the deice pad. The captain reported they taxied to the deice pad and he left the engines and auxiliary power unit (APU) running while the airplane was being deiced. Type 1 deice fluid was used, which resulted in a 15 minute hold over time, giving him 10 minutes to become airborne by time the deicing was completed. The captain reported they moved the airplane out of the deice pad before they turned the systems back on. They then completed the engines-running deicing procedure checklist and requested a taxi clearance. The captain reported the deice pad used was only 5 or 6 airplane lengths away from the end of runway 03C. He said he performed the taxi checklist as the airplane was taxied to the end of the runway, accomplishing all the checklist items. He reported that as part of the checklist, he noted the trim setting on the electronic centralized aircraft monitoring (ECAM) display and the maximum gross load (MGL). He reported that he checked this information against the setting on the trim wheel, making sure it was in the green band. New automatic terminal information service (ATIS) information was received and he noted that the weather was deteriorating. He stated they accomplished the before takeoff checklist, and he briefed the first officer regarding what they would do in case of an engine failure on takeoff. The airplane was then cleared into position to hold, followed 30 seconds later by the takeoff clearance. The captain reported that takeoff/go-around (TOGA) thrust was set, and he held half forward pressure on the control yoke until reaching 80 knots. He reported that up to this point, everything was normal.He stated he released forward stick pressure by about 100 knots, and the nose of the airplane began lifting off the ground with neutral stick, which was not normal. He reported he applied about half forward stick and the nose came back down. He reported that at 120 knots the nose again began to rise with one half to one quarter stick input. He then pushed the stick forward to the forward stop and the nose came up at a rapid rate. The captain reported that his attention was focused outside the airplane and he did not hear the first officer call V1. He reported that he felt the airplane was going to stall so he pulled the power off and aborted the takeoff. The captain stated that he was trained not to perform high-speed aborted takeoffs, but he felt the airplane would have been uncontrollable if the takeoff continued. The captain stated the thrust reversers were deployed and he initially thought there was enough runway remaining to stop. He assumed the autobrakes activated, but he pressed on the brakes anyway. He reported the airplane was not decelerating and it departed the end of the runway at a high speed. The captain reported that deceleration was rapid once the airplane departed the paved surface and the engines flamed out during the ground roll. The captain reported that he believed the tail struck the runway during the aborted takeoff, followed by the main gear and then the nose gear. He stated the impact was hard enough that he thought the airplane was structurally damaged and there was a threat of fire so he initiated an emergency evacuation of the airplane. The flightcrew performed the emergency evacuation checklist, notified the tower, and went to the back of the airplane. He reported he waited until the airplane was empty, then he exited the airplane through the 1R door and the first officer exited using the 1L door. The first officer stated he checked in for the flight and proceeded to the gate where he met the captain and flight attendants. He received his paperwork and waited for the arriving flight to be off loaded. He then proceeded to the airplane where he checked the flight attendant log and reviewed the minimum equipment list with the captain. He then left the airplane to perform the external preflight. The first officer stated that after returning to the cockpit, he arranged to have the airplane deiced, then he continued the preflight. He reported he received the aircraft communication addressing and reporting system (ACARS) load data prior to pushback at which time he entered the request for runway 3C, and requested a pack-off variable speed takeoff. He stated he discussed this with the captain and the captain concurred. The first officer stated he entered the V speed, the zero fuel weight, and the block-out fuel weight information into the computer. He then began his "flow", accomplished the before-start checklist, and called for a pushback clearance. After pushback he called for the taxi clearance. The first officer statedthat while established on the taxiway, he set the stabilizer trim to negative 1.7 and performed the flight control check. He then received their taxi clearance to the runway 3C deice pad. The first officer stated the airplane felt normal while taxiing. The deicing checklist was then accomplished and the deicing was performed. During the deicing he reviewed the hold over chart and used "light snow" for determining the holdover time. They then accomplished the before taxi checklist and received their taxi clearance to runway 3C. The first officer stated the taxi checklist was completed, new ATIS information was received, and the before takeoff checklist was completed before the flight was cleared into position and hold. The flight was then cleared for takeoff. The first officer stated the takeoff started off normally and he made the "80 knots thrust normal" call. He stated that at 100 knots, he felt the nose coming up and he noticed the captain was correcting for it. At about 120 knots, he felt the airplane was coming up, at which time he looked at the captain and then at the airspeed indicator. He noticed the pitch rate was unusual and the captain called "abort". He stated the airplane landed hard and proceeded off the end of the runway. The first officer stated the captain called air traffic control (ATC). They then accomplished the emergency evacuation checklist. The captain then instructed the flight attendants to evacuate the airplane. The first officer stated he and the captain then left the cockpit and exited the airplane. He stated the emergency vehicles were already at the airplane when he exited. PERSONNEL INFORMATION The captain held an airline transport pilot certificate with an airplane multi-engine land rating and a commercial pilot certificate with an airplane single engine land rating. He also held an experimental aircraft builder certificate. The captain held airline transport pilot type ratings in A320, CE-500, and N-265 airplanes. The captain held a first-class medical certificate that was issued on December 7, 2000. This certificate contained the restriction, "Must have available glasses for near vision." The captain reported that he had a lot of experience with general aviation having made his first solo on his 16th birthday. He flew DC-9s as a first officer for Republic Airlines. Northwest Airlines hired him in 1985. He began flying the Airbus A320 in 1990 as a first officer and was upgraded to captain on the A320 about 2 years prior to this accident. The captain reported he had a total of about 16,000 hours of flight time of which 7,000 hours were in A320s. Of that 7,000 hours, about 1,000 hours were as captain. The first officer held an airline transport pilot certificate with an airplane multi-engine land rating and a commercial pilot certificate with an airplane single engine land rating. He held type ratings in DHC-8 and SA-227 airplanes. He held a flight instructor certificate with airplane single engine land andairplane instrument ratings, and both advanced and instrument ground instructor ratings. In addition, the first officer held a flight engineer certificate with a turbojet rating. The first officer held a first-class medical certificate that was issued on June 2, 2000. He also had a waiver on his medical certificate with the restriction "not valid for night flying or by color signal control." The first officer began flying in general aviation. He was employed by Mesaba Airlines where he flew SA-227's for 2 years as a first officer and 1 year as a captain. He then flew DHC-8's before being hired by Northwest Airlines in 1998. He reported that he had been a first officer on A320s since the end of April 2000. The first officer reported having a total of about 13,000 hours of flight time of which approximately 450 hours were in A320s. The captain and first officer had not flown together in the past. The accident occurred on the first leg of a three-day trip for this flight crew. AIRCRAFT INFORMATION N357NW, an Airbus A320-212, serial number 830, accumulated a total airframe time of 9345.54 hours at the time of the accident. The airplane was powered by two CFM56-5-A3 engines. The engines had a total time of 4,123 hours at the time of the accident. The dispatch released the takeoff gross weight for the flight was 151,961 pounds with a maximum takeoff gross weight of 156,500 pounds. The mean aerodynamic chord (MAC) was calculated to be 37.6 percent. The forward MAC limit for the airplane 17.0 percent and the aft MAC limit is 43.0 percent. The airplane was within its weight and balance limitations. The dispatch released cargo weight was 4,808 pounds. The cargo (baggage) was weighed after the accident and the actual cargo weight was determined to be 6,250 pounds. N357NW was maintained in accordance with a Federal Aviation Administration (FAA) approved continuous airworthiness program. The last inspection of the airplane was on March 7, 2001. The airplane accumulated a total of 85 hours since that inspection. The Safety Board studied the aircraft performance in this accident. The Report on Aircraft Performance Group Investigation is in the public docket of this report. The performance study revealed: The Airbus A320 is a "fly-by-wire" airplane. The pilot commands are sent to computers that then send a command to the flight controls as dictated by control laws to reach a desired target. Pitch control is normally accomplished through the elevator aileron control (ELAC) computer. Different control laws are used for different phases of flight. For takeoff, the A320 is designed to initially use ground control law (a direct law that commands a given elevator deflection for a given side stick input) and then it transitions to flight law. A review of the data indicates the NWA985 remained in ground control law throughout the event. Given that the A320 is a "fly-by-wire" airplane, there is latency between the pilot's input and the actual movement of the elevatorthrough the ELAC computer and the rate limit of the elevator. There is also latency between the actual movement of the flight controls and the time in which the movement is time stamped on the FDR. These latencies were taken into account during the review of the accident data. METEOROLOGICAL INFORMATION Automatic Terminal Information Service (ATIS) Information Echo was current at the time of the accident. The weather information contained in Information Echo included weather from the aviation routine weather report (METAR) taken at 0654. The weather at that time was recorded as: Wind: 340 degrees at 6 knots Visibility: 1 ½ statute miles Runway 3L rvr 5,500 feet variable to 6,000 feet Light snow and mist Vertical Visibility 1,000 feet Temperature: -2 degrees Celsius Dew Point: -3 degrees Celsius Altimeter: 30.04 inches of mercury (Hg) The local controller reported that after issuing the ATIS information to NW985, he noticed the visibility was decreasing. He stated that he used the visibility chart and determined that the current visibility was ¾ (three quarters) of a mile. Another METAR was issued at 0710. The weather at that time was reported as: Wind: 350 degrees at 8 knots Visibility: 3/4 statute miles Runway 3L rvr 4,500 feet variable to 5,000 feet Light snow and mist Vertical Visibility 700 feet Temperature: -2 degrees Celsius Dew Point: -3 degrees Celsius Altimeter: 30.04 inches of Hg The first officer reported that it was snowing lightly as they were taxing to the runway. He stated that he could not estimate the visibility. COMMUNICATIONS At 0645:23, NW985 contacted Detroit, Metro, Ground Control Northwest requesting a taxi clearance, stating that they would need to be de-iced. NW985 was told to contact the Detroit, Metro, Ground Control Northeast Controller (GNE) during taxi. At 0647:37, NW985 contacted the GNE controller and was told to hold short for three center at foxtrot for the deice pad. NW985 was then cleared to the deice pad and was told to call when they were finished. At 0702:53, NW985 contacted the GNE controller stating they were ready to taxi. NW985 was cleared to taxi to runway 3C and was informed that information Echo was current. After stating that they did not have information Echo, the controller read it to them. At 0705:28, N985 was cleared into position and hold on runway 3C. At 0707:14, N985 was cleared for takeoff and to fly a heading of 050 after takeoff. At 0708:34, N985 transmitted "evacuate, evacuate." At 0708:55, NW985 informed the tower, "tower nine eighty five we're down." At 0708:59, the local controller acknowledged the transmission. At 0709:14, the local controller transmitted "northwest nine eighty five uh metro tower can you say your position due to the visibility." At 0709:18, NW985 informs the tower "nine eighty five we're down off the end of the runway send a truck we're off three center we're crashed." In his Personnel Statement, the local controller stated that after clearing NW985 for takeoff, hehad a discussion w