DC-9 Collision in MSP...62000 hours on A/C

[ATRedneck]

Just saw the preliminary report on the NTSB website.

The thing that jumped out at me was the number of hours on the part:

The right side hydraulic system was pressurized with hydraulic fluid and a leak from the rudder shutoff valve housing was noted. The rudder shutoff valve, part number 3772374-5503 G, serial number RON 1185, had a recorded total time in service of 62,436 hours.

Is that about average for NWA's 9s, or was that part "new" relative to the airplane?

 

[bafanguy]

ATR,


Just looked at the prelim report you mentioned. Hard to say about the issue of the high-time part. Perhaps that just explains the initial hyd failure. I still want to hear how they managed to move forward after stopping and awaiting the tow-in. The report said the left hyd resv was full.

 

[LarryinTN]

Assuming that the airplane was built in 1970, that's just under 150 hours per month.

The left hydraulic system is quite capable of operating the steering and brakes. Unfortunetly, they shut down the left engine to do a single-engine taxi in so the left system would have also lost pressure. That would result in no steering, no brakes and no reverse on their only operating engine.

 

[Peanut gallery]

FAA Rumors

From an investigator:

While I have never flown the DC-9, so I have no idea how the system works. This is what I heard and maybe someone who has flown the plane can make sense out of this.
The one Electric Hyd pump was DMI'ed. The NWA procedure called for shutting down the associated engine during taxi. After clearing the runway the crewshut down the incorrect engine and lost hyd to the braking system. The accumulator gave them a few applications and then failed as they approached the Bus. The crew then selected reverse thrust which apparently failed to deploy and the crew somehow still managed to get the engine to spool up pushing them harder into the Bus.
Just what is out there.

 

[bafanguy]

Unfortunetly, they shut down the left engine to do a single-engine taxi in so the left system would have also lost pressure.

LJ-ABX,

Would you happen to know if shutting down the left engine for S/E taxi-in is the SOP at NWA ? If this is the case, and that's what they did, it might explain how habit patterns jump up to bite you now and then. We only shut down the rt engine for S/E taxi, but I suppose there's more than one way to do these things.

 

[FurloughedAgain]

ACARS can bite you too. Oftentimes if the ground crew saw the right engine shut-down they would pop the cargo doors (on the right side) before the parking brake was even set. All of the sudden, "POOF" you're off the clock!!

When it then takes another 10 minutes for the jetway driver to show up, you can see why some crews would shut down the left engine and leave the right running... which would keep the ground crew AWAY from the airplane until the crew is READY to come off the clock.

Why sit in an airplane with an engine or APU running (and all of the associated responsibility) if you're not getting paid for it?

 

[Ghetto Buck]

Assuming that the airplane was built in 1970, that's just under 150 hours per month.

The left hydraulic system is quite capable of operating the steering and brakes. Unfortunetly, they shut down the left engine to do a single-engine taxi in so the left system would have also lost pressure. That would result in no steering, no brakes and no reverse on their only operating engine.

NOT TRUE!!!
Form Good system's Knowledge We learn that .........with the alternate pump ON and the Right hyd system pressurised YOU STILL HAVE BRAKES STEERING FLAPS &SLATS and NOSEWHEEL STEERING on the side of the dead Engine, al-be-it at a reduced rate.
have a nice day
Gnd School

 

[bafanguy]

.........with the alternate pump ON and the Right hyd system pressurised YOU STILL HAVE BRAKES STEERING FLAPS &SLATS and NOSEWHEEL STEERING on the side of the dead Engine, al-be-it at a reduced rate.

Gnd School

I believe that in this case, according to the prelim NTSB report, the right hyd system had failed in flight. The right hyd resv was found empty...the left was found full following the incident.

 

[Huck]

ASA had a crew that tested the "six application" accumulator on the EMB-120. It quit when they got to 5. Then they hit something.

 

[fokkers&beer]

62,000 hours on the airframe, and some of the parts. They're almost brand new! Freighters would be salivating for that airframe.

 

[SiuDude]

62,000 hours on the airframe, and some of the parts. They're almost brand new! Freighters would be salivating for that airframe.

I agree, that is pretty "new." 62,000 hours is probably somewhere around 78,000 cycles. The DC-9s are certified for 104,000 cycles and Northwest is gonna make sure they get at least 100,000 cycles out of their 9's.

 

[LarryinTN]

NOT TRUE!!!
Form Good system's Knowledge We learn that .........with the alternate pump ON and the Right hyd system pressurised YOU STILL HAVE BRAKES STEERING FLAPS &SLATS and NOSEWHEEL STEERING on the side of the dead Engine, al-be-it at a reduced rate.
have a nice day
Gnd School

The alt gear pump is worthless (with regard to steering, brakes and reversers) when the right system leaks away all of it's fluid.