CHI05MA111

The A-319 was being pushed back from the gate when it collided with a company DC-9 that was taxiing to the gate area. Prior to arriving at the destination airport, the DC-9 experienced a loss of hydraulic fluid from a fractured rudder shutoff valve located in the DC-9's right side hydraulic system. The left side hydraulic system had normal hydraulic pressure and quantity throughout the flight. The flightcrew elected to continue to the scheduled destination and declared an emergency while on approach to the destination airport. After landing, the emergency was negated by the flight crew and the airplane taxied to the gate. Flight data recorder information indicates the left engine, which provides power for the left hydraulic system, was shut down during taxi. The captain stated he did not remember shutting the left engine down, and that if he had, it would have been after clearing all runways. The first officer stated that he was unaware that the left engine was shut down. Upon arrival at the gate with the left engine shut down and no hydraulic pressure from the left system and a failure of the right hydraulic system, the airplane experienced a loss of steering and a loss of brakes. The flightcrew requested company maintenance to chock the airplane since they were unable to use brakes to stop the airplane. The crew said they were going to keep the "...engines running in case we have to use reversers..." The airplane began to roll forward and the captain applied reverse thrust but the reversers did not deploy. The airplane impacted the A-319 with a speed of approximately 15.65 miles per hour to 16.34 miles per hour. Evacuation of the DC-9 was completed approximately 5:22 minutes after the collision and evacuation of the A-319 occurred approximately 13:08 minutes after the collision. Examination of the left hydraulic system revealed no anomalies and examination of the right hydraulic system revealed a fractured rudder shutoff valve that displayed features consistent with fatigue. Following the accident, the airplane manufacturer issued a service letter pertaining to the replacement of the rudder shutoff valve based upon reliability information that was reported to them. The number of reports was greater than that of the Federal Aviation Administration's Service Difficulty Reports database, and less than the operators records.

The DC-9 was taxiing to the gate area when it collided with a company A-319 that was being pushed back from the gate. Prior to arriving at the destination airport, the DC-9 experienced a loss of hydraulic fluid from a fractured rudder shutoff valve located in the DC-9's right side hydraulic system. The left side hydraulic system had normal hydraulic pressure and quantity throughout the flight. The flightcrew elected to continue to the scheduled destination and declared an emergency while on approach to the destination airport. After landing, the emergency was negated by the flight crew and the airplane taxied to the gate. Flight data recorder information indicates the left engine, which provides power for the left hydraulic system, was shut down during taxi. The captain stated he did not remember shutting the left engine down, and that if he had, it would have been after clearing all runways. The first officer stated that he was unaware that the left engine was shut down. Upon arrival at the gate with the left engine shut down and no hydraulic pressure from the left system and a failure of the right hydraulic system, the airplane experienced a loss of steering and a loss of brakes. The flightcrew requested company maintenance to chock the airplane since they were unable to use brakes to stop the airplane. The crew said they were going to keep the "...engines running in case we have to use reversers..." The airplane began to roll forward and the captain applied reverse thrust but the reversers did not deploy. The airplane impacted the A-319 with a speed of approximately 15.65 miles per hour to 16.34 miles per hour. Evacuation of the DC-9 was completed approximately 5:22 minutes after the collision and evacuation of the A-319 occurred approximately 13:08 minutes after the collision. Examination of the left hydraulic system revealed no anomalies and examination of the right hydraulic system revealed a fractured rudder shutoff valve that displayed features consistent with fatigue. Following the accident, the airplane manufacturer issued a service letter pertaining to the replacement of the rudder shutoff valve based upon reliability information that was reported to them. The number of reports was greater than that of the Federal Aviation Administration's Service Difficulty Reports database, and less than the operators records.

History of flight

On May 10, 2005, at 1936 central daylight time, a McDonnell Douglas DC-9-51, N763NC, collided with an Airbus A-319-114, N368NB, during taxi into the gate resulting in substantial damage to both airplanes near gate G10, at Minneapolis/St. Paul International Airport (MSP), Minneapolis, Minnesota. Both airplanes were operated by Northwest Airlines Inc. (NWA) under Title 14 Code of Federal Regulations (CFR) Part 121 as scheduled-domestic passenger flights 1495 (N763NC) and 1849 (N368NB). Visual meteorological conditions prevailed at the time the accident. Both airplanes were evacuated after the collision. The DC-9 captain (CAPT) received serious injuries and the first officer (FO), two flight attendants (FAs) and two passengers received minor injuries. Three A-319 FAs and one passenger received minor injuries. Three NWA ground personnel received minor injuries. N763NC departed Port Columbus International Airport (CMH), Columbus, Ohio, at 1826 eastern daylight time with a scheduled destination to MSP.

The following are excerpts from the Operations Group Chairman and DC-9 Cockpit Voice Recorder (CVR) Group Factual Reports. The CVR transcription contains recordings of the CAPT, FO, cockpit area microphone (CAM), radio transmissions from the CAPT (RDO-1) and FO (RDO-2), NWA maintenance control (MAINT), and MSP Air Traffic Control Tower (ATCT).

The DC-9 CAPT stated that the accident occurred on the second leg of a two-day trip. The first leg from MSP to CMH was uneventful.

The FO was the flying pilot on the return flight from CMH to MSP. The FO stated that the departure from CMH was normal except that they had to use five degrees of flaps for takeoff because of the airplane's heavier weight. After takeoff, at some point below 4,000 feet altitude, when the slats were retracted, the MASTER CAUTION light illuminated. He observed the RUDDER CONTROL MANUAL annunciator light and then saw that the right hydraulic system pressure was about 1,000 pounds per square inch (PSI).

Approximately 1736, the FO stated, "we've lost pressure on the right side" and ten seconds later commented "...we lost the quantity, too." Approximately three minutes later the FO called for the 'climb check'.

The CAPT stated that he noticed the right hydraulic system quantity decreasing rapidly. The CAPT reached over to turn off the hydraulic pumps but later noticed that he had only selected the right engine hydraulic pump switch to the LOW position instead of OFF. He then corrected the switch position to OFF and finished the COM Hydraulic Pressure Low and/or Fluid Loss procedure.

Approximately 1745, the FO asked "what's its say, or your thoughts about continuing?" and the CAPT responded "well we're gonna talk to everybody before we make any decisions. I don't see an urgent need to be turning around right this second," and the FO responded "I don't either." During the next ten minutes the CAPT and FO discussed the need for manual gear extension and the loss of the outboard spoiler system. During this discussion, it was noted that the right side hydraulic quantity had risen to indicate four quarts.

The CAPT stated that there was no emergency, and the FO continued flying the airplane. Above 10,000 feet, the CAPT transferred both the flying and ATC communication duties to the FO while the CAPT referred to the NWA DC-9 Cockpit Operating Manual (COM) to complete the procedures. He stated that he referred to the procedure in the COM for right hydraulic system quantity loss and went through the procedure several times. During this time, the right engine hydraulic pump switch was repositioned from LOW to OFF. He then read ahead through the emergency gear extension procedure.

The CAPT stated they had a situation that would involve a manual rudder, which means that they had to have an adequate amount of runway and would have to fly a little faster speed on the approach. He and the FO discussed the procedure, and they tried to reset some circuit breakers to regain hydraulic pressure from the auxiliary hydraulic pump. The CAPT wanted to get the FO more involved; therefore, he asked him to read through the procedures.

Approximately 1756, the CAPT began communications with maintenance control (MAINT) to discuss the hydraulic problem. The right hydraulic system fluid quantity was indicating five quarts and while they were talking, it had increased to six quarts. He asked the MAINT mechanic what he thought the problem was, and the MAINT mechanic said that he had never seen anything like that, but it sounded like there was a problem with the hydraulic fluid reservoir. The CAPT interpreted that to mean that the mechanic thought there was a problem with the fluid quantity transmitter on the reservoir. The CAPT ended this communication approximately three minutes later, stating "roger that we will continue back to Minneapolis then" and confirmed that dispatch had copied the entire exchange. He decided to continue on to MSP in order to burn off some fuel to reduce the weight of the airplane. He also discussed the situation with the FO before deciding to continue to MSP. He decided not to immediately declare an emergency with ATC because he thought the situation was stabilized.

The CAPT stated that he once again went through the procedures in the COM. The right hydraulic system pressure was indicating zero, but the hydraulic low pressure light (R HYD PRESS LOW) on the annunciator panel was not illuminated. He said that he performed an annunciator panel light test and found the light bulbs for the right hydraulic system pressure low light were inoperative. He had checked the annunciator lights on preflight and they had all been working normally. When he attempted to change the bulbs, the entire housing came apart. He stated that he basically slammed the door closed and the light came on, but it was so broken up that he was not certain if the light came on because the housing was broken or if the light came on because it was actually indicating low pressure.

The CAPT stated that the checklist was straightforward but when he ran the COM checklist, there was confusion when trying to decide what problem they really had and whether they were using the correct checklist. It was really confusing when the right system hydraulic quantity came back up, and there was no hydraulic pressure low annunciator light. He said he told the FO that they had to look at what they had and go by the proper checklist.

Approximately 1815, the CAPT stated, "alright now I can read the procedure. Start to finish. Hydraulic pressure low [unintelligible]."

The CAPT stated, "We finally decided to address what was indicated, which was low hydraulic pressure on the right side and normal quantity of hydraulic fluid on the right side." On the left side, both pressure and quantity were normal. Both he and the FO went through the procedure for right hydraulic system quantity normal but pressure low. Following the procedure, the brake selector was selected to the left side, and the rudder control was placed in manual. Later there were Airborne Communications and Response System (ACARS) communications with Dispatch. Dispatch suggested using runway 22 for landing at MSP in case they had to stop on the runway and have the landing gear "pinned" and the landing gear doors raised. The CAPT told them that he wanted a truck standing by to "pin" the landing gear when they arrived. He did not declare an emergency immediately because they were not sure if they were going to have to use the emergency landing gear extension. The FO stated that he thought they should go ahead and declare an emergency because of the manual rudder. The CAPT stated that that was a valid point, and he then declared an emergency with ATC.

The CAPT stated that when they were about half way into the flight, the hydraulic quantity indication continued to rise to a normal le

History of flight

On May 10, 2005, at 1936 central daylight time, a McDonnell Douglas DC-9-51, N763NC, collided with an Airbus A-319-114, N368NB, during taxi into the gate resulting in substantial damage to both airplanes near gate G10, at Minneapolis/St. Paul International Airport (MSP), Minneapolis, Minnesota. Both airplanes were operated by Northwest Airlines Inc. (NWA) under Title 14 Code of Federal Regulations (CFR) Part 121 as scheduled-domestic passenger flights 1495 (N763NC) and 1849 (N368NB). Visual meteorological conditions prevailed at the time the accident. Both airplanes were evacuated after the collision. The DC-9 captain (CAPT) received serious injuries and the first officer (FO), two flight attendants (FAs) and two passengers received minor injuries. Three A-319 FAs and one passenger received minor injuries. Three NWA ground personnel received minor injuries. N763NC departed Port Columbus International Airport (CMH), Columbus, Ohio, at 1826 eastern daylight time with a scheduled destination to MSP.

The following are excerpts from the Operations Group Chairman and DC-9 Cockpit Voice Recorder (CVR) Group Factual Reports. The CVR transcription contains recordings of the CAPT, FO, cockpit area microphone (CAM), radio transmissions from the CAPT (RDO-1) and FO (RDO-2), NWA maintenance control (MAINT), and MSP Air Traffic Control Tower (ATCT).

The DC-9 CAPT stated that the accident occurred on the second leg of a two-day trip. The first leg from MSP to CMH was uneventful.

The FO was the flying pilot on the return flight from CMH to MSP. The FO stated that the departure from CMH was normal except that they had to use five degrees of flaps for takeoff because of the airplane's heavier weight. After takeoff, at some point below 4,000 feet altitude, when the slats were retracted, the MASTER CAUTION light illuminated. He observed the RUDDER CONTROL MANUAL annunciator light and then saw that the right hydraulic system pressure was about 1,000 pounds per square inch (PSI).

Approximately 1736, the FO stated, "we've lost pressure on the right side" and ten seconds later commented "...we lost the quantity, too." Approximately three minutes later the FO called for the 'climb check'.

The CAPT stated that he noticed the right hydraulic system quantity decreasing rapidly. The CAPT reached over to turn off the hydraulic pumps but later noticed that he had only selected the right engine hydraulic pump switch to the LOW position instead of OFF. He then corrected the switch position to OFF and finished the COM Hydraulic Pressure Low and/or Fluid Loss procedure.

Approximately 1745, the FO asked "what's its say, or your thoughts about continuing?" and the CAPT responded "well we're gonna talk to everybody before we make any decisions. I don't see an urgent need to be turning around right this second," and the FO responded "I don't either." During the next ten minutes the CAPT and FO discussed the need for manual gear extension and the loss of the outboard spoiler system. During this discussion, it was noted that the right side hydraulic quantity had risen to indicate four quarts.

The CAPT stated that there was no emergency, and the FO continued flying the airplane. Above 10,000 feet, the CAPT transferred both the flying and ATC communication duties to the FO while the CAPT referred to the NWA DC-9 Cockpit Operating Manual (COM) to complete the procedures. He stated that he referred to the procedure in the COM for right hydraulic system quantity loss and went through the procedure several times. During this time, the right engine hydraulic pump switch was repositioned from LOW to OFF. He then read ahead through the emergency gear extension procedure.

The CAPT stated they had a situation that would involve a manual rudder, which means that they had to have an adequate amount of runway and would have to fly a little faster speed on the approach. He and the FO discussed the procedure, and they tried to reset some circuit breakers to regain hydraulic pressure from the auxiliary hydraulic pump. The CAPT wanted to get the FO more involved; therefore, he asked him to read through the procedures.

Approximately 1756, the CAPT began communications with maintenance control (MAINT) to discuss the hydraulic problem. The right hydraulic system fluid quantity was indicating five quarts and while they were talking, it had increased to six quarts. He asked the MAINT mechanic what he thought the problem was, and the MAINT mechanic said that he had never seen anything like that, but it sounded like there was a problem with the hydraulic fluid reservoir. The CAPT interpreted that to mean that the mechanic thought there was a problem with the fluid quantity transmitter on the reservoir. The CAPT ended this communication approximately three minutes later, stating "roger that we will continue back to Minneapolis then" and confirmed that dispatch had copied the entire exchange. He decided to continue on to MSP in order to burn off some fuel to reduce the weight of the airplane. He also discussed the situation with the FO before deciding to continue to MSP. He decided not to immediately declare an emergency with ATC because he thought the situation was stabilized.

The CAPT stated that he once again went through the procedures in the COM. The right hydraulic system pressure was indicating zero, but the hydraulic low pressure light (R HYD PRESS LOW) on the annunciator panel was not illuminated. He said that he performed an annunciator panel light test and found the light bulbs for the right hydraulic system pressure low light were inoperative. He had checked the annunciator lights on preflight and they had all been working normally. When he attempted to change the bulbs, the entire housing came apart. He stated that he basically slammed the door closed and the light came on, but it was so broken up that he was not certain if the light came on because the housing was broken or if the light came on because it was actually indicating low pressure.

The CAPT stated that the checklist was straightforward but when he ran the COM checklist, there was confusion when trying to decide what problem they really had and whether they were using the correct checklist. It was really confusing when the right system hydraulic quantity came back up, and there was no hydraulic pressure low annunciator light. He said he told the FO that they had to look at what they had and go by the proper checklist.

Approximately 1815, the CAPT stated, "alright now I can read the procedure. Start to finish. Hydraulic pressure low [unintelligible]."

The CAPT stated, "We finally decided to address what was indicated, which was low hydraulic pressure on the right side and normal quantity of hydraulic fluid on the right side." On the left side, both pressure and quantity were normal. Both he and the FO went through the procedure for right hydraulic system quantity normal but pressure low. Following the procedure, the brake selector was selected to the left side, and the rudder control was placed in manual. Later there were Airborne Communications and Response System (ACARS) communications with Dispatch. Dispatch suggested using runway 22 for landing at MSP in case they had to stop on the runway and have the landing gear "pinned" and the landing gear doors raised. The CAPT told them that he wanted a truck standing by to "pin" the landing gear when they arrived. He did not declare an emergency immediately because they were not sure if they were going to have to use the emergency landing gear extension. The FO stated that he thought they should go ahead and declare an emergency because of the manual rudder. The CAPT stated that that was a valid point, and he then declared an emergency with ATC.

The CAPT stated that when they were about half way into the flight, the hydraulic quantity indication continued to rise to a normal le