NTSB Factual Report

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 level, about eight quarts. He and the FO discussed the situation and decided that there was normal hydraulic quantity but low hydraulic pressure on the right hydraulic system, and normal hydraulic pressure and quantity on the left hydraulic system. They went through the procedures again.

They had lots of time to discuss the runway, when to start the descent, and how they would extend the landing gear. They were not sure if the landing gear would come down normally or if they would have to use the alternate landing gear extension method. The CAPT stated that they had plenty of fuel and decided to lower the landing gear early.

Approximately 1835 the CAPT briefed the lead flight attendant (Position A FA) on the situation and intention to declare a "yellow emergency". (Yellow emergency is a NWA specific terminology).

He stated that after they decided on a course of action, he then briefed the flight attendants (FAs). The first FA to come to the cockpit was the "add" [additional] FA, so he decided to brief her and later briefed Position A FA. He told her about the entire situation and that there were two possible scenarios regarding the landing gear: one, if the gear came down normally and two, if they had to use the alternate method of landing gear extension. If they had to use the alternate method of lowering the landing gear, he wanted the FAs to prepare for a "yellow" emergency. He told them that if this were the case, they would be stopping on the runway and not to be alarmed if rescue and fire trucks were seen near the airplane. If it was not going be a normal landing, he told the FAs he would give them about ten minutes notice before landing.

Approximately 1850, the CAPT contacted dispatch to request that they "call out the trucks" for their arrival. Approximately 30 seconds later the FO began briefing the approach to runway 22.

The FO stated that he tuned in the Automatic Terminal Information Service and heard weather of 5,000 feet broken with 10 miles visibility. He briefed for a visual approach to runway 22 with a localizer backup. There was no instrument landing system (ILS) on runway 22.

Approximately 1900, the FO noted 'we just lost our quantity.' Approximately one minute later the CAPT radioed to MSP center "ah we got a hydraulic problem, we're gonna go ahead and declare an emergency. ah everything should be okay but just gonna have to land a little faster and we're gonna have the trucks standing and everything."

The CAPT stated that MSP Approach Control started giving the flight radar vectors and he had to remind them that they were an aircraft in an emergency situation. Approximately 1905, they were on approach and the CAPT and FO both indicated that the landing gear had extended successfully. They did not use the Emergency Gear Extension Handle. When MAINT said there may be a reservoir problem, he thought there was a higher chance that it was an indication problem and then when the landing gear came down, it reinforced this idea. He thought to himself that he must not have had a problem with that hydraulic system.

At 1908, the Minneapolis Saint-Paul Metropolitan Airport Commission (MAC) Fire Department received an initial notification call from ATC for an alert 2 (according to the MSP Emergency Plan, an Alert 2 notification prompts ARFF to "stand-by at predetermined locations at a runway for incoming aircraft with a problem").

The FO stated that he flew a long slow downwind from Farmington to a downwind leg to runway 22. He turned onto the localizer course at an altitude about 3,000 feet. The flight was then cleared for the approach to runway 22. He observed a cloud ahead, which prevented him from seeing the runway. He stated that he told the CAPT that he could not descend at that point without seeing the runway; therefore, he requested that the CAPT tune in the crossing radial to identify a fix along the localizer course. The FO stated that he saw the runway visually by the final approach fix.

Approximately 1919, the FO called "flaps 40 landing check."

1920:44, TWR, Northwest fourteen ninety five Minneapolis tower runway two two cleared to land winds calm you're number two for the airport traffic three mile final runway three zero left.

1920:54, RDO-1, cleared to land ah two two Northwest fourteen ninety five you're aware we cle - declared emergency and we won't be able to go around.

1920:60, TWR, roger. And Northwest fifteen ah thirty six traffic emergency landing runway two two I'll need you I know you can't commit it's a wet runway but ah just don't delay ah around two two either roll through it or stop short of it.

1921:08, CAPT, down and green flaps forty. forty blue. spoilers armed. checklist complete.

The CAPT stated that there was a visual approach slope indicator (VASI) on runway 22. As they approached the runway they drifted a little high on the VASI but then corrected and accomplished an uneventful landing in the proper touch down zone. The FO stated that upon landing, he applied brakes a little earlier than normal to make sure they were working. Reverse thrust was also working.

1923:01, CAM, [sound similar to tires contacting runway and auto-ground spoilers activating].

1923:02, FO, still **. ah ya.

1923:04, CAPT, (go back).

1923:09, CAPT, reverse normal.

1923:29. FO, you got the plane.

1923:30, TWR, …ah you want the equipment out there?

1923:30, CAPT, I got it.

1923:31, RDO-1, ah fourteen ninety five we're okay ah, everything's good to go.

1923:34, TWR, roger stow the equipment?

1923:37, RDO-1, yes sir.

1923:37, TWR, roger.

1923:41, FO, you got the plane. yea…

1924:04, RDO-2, ground Northwest fourteen ninety five's ah clear of two two and ah no longer need any assistance for the ah emergency response.

1925:35, CAPT, flaps came up and everything *.

1925:37, FO, …complete. yea they did.

The CAPT stated that after landing, the hydraulic low-pressure annunciator light stayed on while rolling down the runway. He thought that the light was broken. He was thinking that everything was normal. After landing, the CAPT felt relieved. As they were slowing down on the runway, he told TWR that the emergency vehicles were no longer needed. After clearing the runway, the CAPT called for the flaps to be retracted and then called for the After Landing checklist. The FO completed the After Landing checklist while the CAPT retracted the spoilers and turned off the landing lights and antiskid.

The flight exited the runway on taxiway C2 and were then cleared to taxi on taxiway C, make a left turn on taxiway C3, back-taxi on runway 22, and hold short of runway 30L. The CAPT had to taxi the airplane from the taxiway back onto the runway because of construction activity. Runway 22 was then used as a taxiway. The CAPT stated that he had forgotten and was surprised that there was construction along the runway. While taxiing, the CAPT stated that he looked at the brake accumulator gauges for pressure just before crossing runway 30L and they were both normal.

At 1928:05, South Ground Control cleared NWA 1495 to "cross runway three zero left turn right on alpha taxi to the gate traffic on Charlie is waiting for you." NWA 1495 acknowledged the clearance.

The FO stated that he accomplished the after landing "flow," did the After Landing checklist, and called Ramp Control to confirm gate G7.

At 1928:36, CAM recorded [sound of mechanical click followed by high frequency noise reducing in frequency, sound of clunk, and high frequency noise stabilizing - sound similar to engine shutdown]. According to the Flight Data Recorder Specialist's Factual Report, at 1928:42, the left engine pressure ratio (EPR) decreased to 1.01 and remained at the value until the end of the recording, which was 1936:42.

The CAPT stated that it was his typical routine to not shut down an engine until clear of all runways. He stated that he did not recall shutting down the left engine, but he stated that if he had shut down the left-hand engine, he would have done so after crossing runway 30L. After crossing runway 30L, he made a right turn onto taxiway A. They were taxiing by the "tunnel" when they started to have problems. They made a slight gradual turn into the gate area. He had just started to turn i

NTSB Probable Cause

the Captain's decision to shutdown the left engine during taxi with no hydraulic pressure on the right side hydraulic system to effectively operate the brakes, steering, or thrust reversers. A factor was the fatigue fracture of the rudder shutoff valve which resulted in the loss of right side hydraulic pressure.