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CRJ Hydraulic Pump Deferral  
User currently offlineDocLightning From United States of America, joined Nov 2005, 19725 posts, RR: 58
Posted (2 years 6 months 1 week 2 days 17 hours ago) and read 3230 times:

Was on N886AS today from PHX to OAK. We taxied out and then taxied back because a hydraulic pump wasn't working. Captain said "we have another perfectly good one, so we can just defer it. It won't take a minute."

So obviously, there was more than one other hydraulic pump aboard, yes? We didn't fly with one working hydraulic pump, correct?

What was he talking about, then?

22 replies: All unread, jump to last
 
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 1, posted (2 years 6 months 1 week 2 days 10 hours ago) and read 3147 times:

Quoting DocLightning (Thread starter):
So obviously, there was more than one other hydraulic pump aboard, yes?

Yes. There were 5 others. A CRJ has three hydraulic systems (1, 2, and 3) with two pumps on each. 1 and 2 each have one engine driven pump and one electrical pump. 3 has two electrical pumps.

Quoting DocLightning (Thread starter):
We didn't fly with one working hydraulic pump, correct?

Correct.

Quoting DocLightning (Thread starter):
What was he talking about, then?

On the system that they deferred the pump, you had one working pump left. Had that pump failed you would have lost that hydraulic system (but had two other perfectly good ones).

Tom.


User currently onlineGoldenshield From United States of America, joined Jan 2001, 6037 posts, RR: 14
Reply 2, posted (2 years 6 months 1 week 2 days 5 hours ago) and read 3050 times:

Quoting tdscanuck (Reply 1):
On the system that they deferred the pump, you had one working pump left. Had that pump failed you would have lost that hydraulic system (but had two other perfectly good ones).

Exactly.

Redundancy in transport aircraft is pretty crtical. and thus, having different hydraulic systems power different parts of the airplane ensure this redundancy. There's only a couple incidents that I can think of where the plane was not able to manuever due to loss of all hydraulics.

Also, in the case of this CRJ, there's one pump that CANNOT be deferred; that being 3B. This is the emergency pump and it powered by the ADG should the plane lose power.



Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.
User currently offlineDocLightning From United States of America, joined Nov 2005, 19725 posts, RR: 58
Reply 3, posted (2 years 6 months 1 week 2 days 3 hours ago) and read 3024 times:

Quoting Goldenshield (Reply 2):
Redundancy in transport aircraft is pretty crtical.

Right. Hence my question. I knew that no pilot in his right mind would take off with one working pump. So I wondered how many there were.

At the time, I guessed there were at least two hydraulic systems, probably three. I guessed there were two pumps per system. Apparently, I'm right.  


User currently offlinewoodreau From United States of America, joined Sep 2001, 1042 posts, RR: 6
Reply 4, posted (2 years 6 months 1 week 1 day 19 hours ago) and read 2934 times:

Quoting Goldenshield (Reply 2):
Also, in the case of this CRJ, there's one pump that CANNOT be deferred; that being 3B. This is the emergency pump and it powered by the ADG should the plane lose power.

I was wondering if your company has a different MEL, as ours 1B, 2B, and 3B may not be deferred (-700/900 model MEL) or (not knowing which CRJ 866AS is and based on your "in the case of this CRJ" qualifier) is this a difference between a -200 model and a -700/900/1000 model. Thx.



Bonus animus sit, ab experientia. Quod salvatum fuerit de malis usu venit judicium.
User currently offlineFlyASAGuy2005 From United States of America, joined Sep 2007, 7004 posts, RR: 11
Reply 5, posted (2 years 6 months 1 week 19 hours ago) and read 2760 times:

Quoting woodreau (Reply 4):

886AS is a CR2..



What gets measured gets done.
User currently offlineDocLightning From United States of America, joined Nov 2005, 19725 posts, RR: 58
Reply 6, posted (2 years 6 months 1 week 17 hours ago) and read 2752 times:

Quoting FlyASAGuy2005 (Reply 5):
886AS is a CR2..

Out of curiosity, did you look it up or do you know it by heart?


User currently onlineGoldenshield From United States of America, joined Jan 2001, 6037 posts, RR: 14
Reply 7, posted (2 years 6 months 1 week 13 hours ago) and read 2713 times:

Quoting woodreau (Reply 4):
I was wondering if your company has a different MEL, as ours 1B, 2B, and 3B may not be deferred (-700/900 model MEL) or (not knowing which CRJ 866AS is and based on your "in the case of this CRJ" qualifier)
is this a difference between a -200 model and a -700/900/1000 model. Thx.

Well, the MMEL aside, everyone's going to have slight differences. Yes, in the -200, you can have 1B and 2B deferred, as long as the all 3 hydraulic systems have a way to pressurize. With the 7/900, you are correct that none of the Bs can be deferred. Also, Neither 1A or 2A can be deferred at the same time.

Quoting DocLightning (Reply 6):
Quoting FlyASAGuy2005 (Reply 5):
886AS is a CR2..

Out of curiosity, did you look it up or do you know it by heart?

Airlines (at least here in the US) have number ranges for different aircraft types and/or versions (with a few exceptions) to help differentiate them to those who work with them.



Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 8, posted (2 years 6 months 1 week 4 hours ago) and read 2654 times:

Quoting DocLightning (Reply 6):
Quoting FlyASAGuy2005 (Reply 5):
886AS is a CR2..

Out of curiosity, did you look it up or do you know it by heart?

I can't speak for FlyASAGuy2005, but I looked it up on airfleets.net and it also says CRJ-200.

Tom .


User currently offlineFlyASAGuy2005 From United States of America, joined Sep 2007, 7004 posts, RR: 11
Reply 9, posted (2 years 6 months 6 days 23 hours ago) and read 2599 times:

Quoting DocLightning (Reply 6):
Out of curiosity, did you look it up or do you know it by heart?

Knew it by heart.

Former EV bird. All ASA CR2s (prior to aquiring the ACA a/c (600BRs)) are numbered 800AS or 900EV. All CR7s (prior to the Comair and QX transferes) are numbered 700EV (one given an IND reg).



What gets measured gets done.
User currently offlineVC-10 From United Kingdom, joined Oct 1999, 3701 posts, RR: 34
Reply 10, posted (2 years 6 months 6 days 23 hours ago) and read 2596 times:
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Assuming it wasn't a nil dispatch why did they return to the gate? In out MEL is says 'The MEL applies to all defects that occur up to the point of dispatch, and comes into effect again when the a/c next comes to rest at the end of its flight' - EASA regs

User currently onlineGoldenshield From United States of America, joined Jan 2001, 6037 posts, RR: 14
Reply 11, posted (2 years 6 months 6 days 22 hours ago) and read 2590 times:

Quoting VC-10 (Reply 10):

Assuming it wasn't a nil dispatch why did they return to the gate? In out MEL is says 'The MEL applies to all defects that occur up to the point of dispatch, and comes into effect again when the a/c next comes to rest at the end of its flight' - EASA regs

Restrictive MELs need to be complied with before takeoff regardless of whether they are at the gate or taxiing, per the FAA.



Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.
User currently offlineapodino From United States of America, joined Apr 2005, 4280 posts, RR: 6
Reply 12, posted (2 years 6 months 6 days 8 hours ago) and read 2518 times:

On the CRJ-200 the 1B, 2B, and the 3A pumps can be deferred. Those are all Electrical driven pumps. Though it is very rare, the two engine driven pumps can be deferred as well.

The 2B pump is the biggest pain in the neck to defer though. Hydraulic system 2 controls the Landing Gear and the Anti Skid system on the airplane, so when 2B is deferred, the restriction also assumes that you are without an Anti Skid system as well. What that means is at sea level, you need at least a 9,000 foot long runway (For landing, not takeoff) to avoid a serious weight restriction (And more than likely to even be able to launch, which is one reason why the plane is never sent to LGA or DCA with that MEL in place).

The 3A pump also has a slight performance hit on takeoff, but it never causes the problems that a deferred 2B pump causes.


User currently offlinewoodreau From United States of America, joined Sep 2001, 1042 posts, RR: 6
Reply 13, posted (2 years 6 months 6 days 6 hours ago) and read 2492 times:

Quoting Goldenshield (Reply 7):
Yes, in the -200, you can have 1B and 2B deferred, as long as the all 3 hydraulic systems have a way to pressurize. With the 7/900, you are correct that none of the Bs can be deferred.

Thanx for the info. Surprised that the -200 can defer the B pumps, I wonder what changed.

Quoting VC-10 (Reply 10):
Assuming it wasn't a nil dispatch why did they return to the gate? In out MEL is says 'The MEL applies to all defects that occur up to the point of dispatch, and comes into effect again when the a/c next comes to rest at the end of its flight' - EASA regs

Sometimes you can defer without returning to the gate if you can crew placard. If mx has to placard the deferral and the crew is not permitted to defer the inoperative item, then you have to go back to the gate.



Bonus animus sit, ab experientia. Quod salvatum fuerit de malis usu venit judicium.
User currently offlineDashTrash From United States of America, joined Aug 2006, 1528 posts, RR: 2
Reply 14, posted (2 years 6 months 6 days 5 hours ago) and read 2482 times:

Quoting Goldenshield (Reply 7):
With the 7/900, you are correct that none of the Bs can be deferred. Also, Neither 1A or 2A can be deferred at the same time.

Slats on the B system. or both?


User currently onlineGoldenshield From United States of America, joined Jan 2001, 6037 posts, RR: 14
Reply 15, posted (2 years 6 months 6 days 4 hours ago) and read 2475 times:

Quoting woodreau (Reply 13):
Surprised that the -200 can defer the B pumps, I wonder what changed.

Everything changed on the -700 (including the -900/1000)---for the better. Better bleed air configuration and automation, better anti-ice, hydraulic reversers, etc. I could go on.

Quoting DashTrash (Reply 14):
Slats on the B system. or both?

Erm, no. Electrically driven via two motors and a torque tube.



Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.
User currently offlinewingscrubber From UK - England, joined Sep 2001, 850 posts, RR: 0
Reply 16, posted (2 years 6 months 6 days 4 hours ago) and read 2475 times:

http://www.smartcockpit.com/pdf/plan...r/CRJ-100-200-SERIES/systems/0015/

Smartcockpit has some good material describing the CRJ hydraulic system.



Resident TechOps Troll
User currently offlineDocLightning From United States of America, joined Nov 2005, 19725 posts, RR: 58
Reply 17, posted (2 years 6 months 6 days 2 hours ago) and read 2458 times:

Quoting woodreau (Reply 13):
Sometimes you can defer without returning to the gate if you can crew placard. If mx has to placard the deferral and the crew is not permitted to defer the inoperative item, then you have to go back to the gate.

We were back at the gate for maybe ten minutes tops. All in all, we were less than 25 minutes late on arrival into OAK.

Quoting apodino (Reply 12):
The 2B pump is the biggest pain in the neck to defer though. Hydraulic system 2 controls the Landing Gear and the Anti Skid system on the airplane, so when 2B is deferred, the restriction also assumes that you are without an Anti Skid system as well. What that means is at sea level, you need at least a 9,000 foot long runway (For landing, not takeoff) to avoid a serious weight restriction

Wasn't 2B then, because the weather at OAK was absolutely rotten.


User currently offlineapodino From United States of America, joined Apr 2005, 4280 posts, RR: 6
Reply 18, posted (2 years 6 months 5 days 19 hours ago) and read 2420 times:

Quoting DocLightning (Reply 17):
n

Wasn't 2B then, because the weather at OAK was absolutely rotten.

It still could have been the 2B. IIRC runway 11-29 at Oak is nearly 11,000 feet long, which is plenty long enough to handle a 2B pump. The fact that the visibility was down is irrelevant to the length of runway needed for a safe landing.


User currently onlineGoldenshield From United States of America, joined Jan 2001, 6037 posts, RR: 14
Reply 19, posted (2 years 6 months 5 days 15 hours ago) and read 2407 times:

Quoting DocLightning (Reply 17):
Wasn't 2B then, because the weather at OAK was absolutely rotten.

I know what it was, but I've already said enough...

Quoting apodino
It still could have been the 2B.

It's already been fixed. That is all.

[Edited 2012-03-20 02:26:24]


Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.
User currently offlineDashTrash From United States of America, joined Aug 2006, 1528 posts, RR: 2
Reply 20, posted (2 years 6 months 5 days 11 hours ago) and read 2380 times:

Quoting Goldenshield (Reply 15):
Erm, no. Electrically driven via two motors and a torque tube.

Far out. I thought they were hydraulic.


User currently offlineAlias1024 From United States of America, joined Oct 2004, 2760 posts, RR: 2
Reply 21, posted (2 years 6 months 5 days 5 hours ago) and read 2339 times:

Quoting apodino (Reply 12):
The 2B pump is the biggest pain in the neck to defer though. Hydraulic system 2 controls the Landing Gear and the Anti Skid system on the airplane, so when 2B is deferred, the restriction also assumes that you are without an Anti Skid system as well. What that means is at sea level, you need at least a 9,000 foot long runway (For landing, not takeoff) to avoid a serious weight restriction (And more than likely to even be able to launch, which is one reason why the plane is never sent to LGA or DCA with that MEL in place).

Ugliest weight penalty I've ever seen was with 3A deferred and an inop APU in freezing fog. Unpressurized takeoff so we could use the bleeds for wing and cowl anti-ice, and the 3A deferral requires single engine performance to be calculated with the landing gear remaining down. Even with 11,000 feet of runway we were limited to 26 passengers.  Wow!



It is a mistake to think you can solve any major problems with just potatoes.
User currently offlineDashTrash From United States of America, joined Aug 2006, 1528 posts, RR: 2
Reply 22, posted (2 years 6 months 4 days 23 hours ago) and read 2307 times:

Quoting Alias1024 (Reply 21):
Ugliest weight penalty I've ever seen was with 3A deferred and an inop APU in freezing fog. Unpressurized takeoff so we could use the bleeds for wing and cowl anti-ice, and the 3A deferral requires single engine performance to be calculated with the landing gear remaining down. Even with 11,000 feet of runway we were limited to 26 passengers.

That would make one hell of a hit on second segment climb!


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