L engine bleed trip off with 1 engine as bleed source.

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L engine bleed trip off with 1 engine as bleed source.

Postby lj_dekker » 13 Jul 2007, 18:25

Howdy,

We had an a/c with a L engine bleed trip off with 1 engine as bleed source after selecting wing anti ice right after take off.

Is this normal?
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Postby sjap » 14 Jul 2007, 14:07

No its not normal.
The bleed tripoff, was it resettable? are the duct-pressures within limits ?
Else you need to do a bleed health check and see if one of the components is malfunctioning.
regards
sjap
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Postby lj_dekker » 14 Jul 2007, 16:09

It was resettebale. the a/c made a no bleed take off. After selecting engine bleeds on, engine no. 2 duct press was 5 psi and left was 40 psi. At FL330 the crew tried wing anti ice when right duct press was 5 psi and l was 40 psi. When wing anti ice was selected, left engine had a bleed trip, so at that point he had a huge problem, but it was almost immediately resettable and at TOC r engine was also 40 psi again (when throttles retarded). from that on they did not had any probles again. We chenged the HSV of engine 2 and the a/c did not had the problem again.
For engine 1, i heard that the max altitude to select wing anti ice is FL350 and when it is selected close to the max altitude it could generate a bleed trip. You ever heard of this problem. A/c was an NG btw.

regards.
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Postby troubleshooter » 16 Jul 2007, 18:45

I would say that l/h bleed tripped off due to the high required airflow in the system after wing anti ice selection resulting in a high precooler outlet temperature (> 254°C is the trip point). Was the isolation valve open at that time???
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Postby hakani » 31 Aug 2007, 09:22

We had same problem our 734 type a/c, which returned from C check and engine #1 also changed. Technicians at the hangar in Romania who replaced the engine, they wrongly fix the 450F thermostat line between precooler cont. valve 390F thermostat line... It is reaaly interesting because the line has same size (11/16 I remember) There is no murphy:)
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Postby beerbrewer737 » 04 Oct 2007, 20:53

I will not say it's impossible to do but the 450 thermostat and the (390) pre-cooler sensor ARE different. Look at the bottom of either sensor and you'll see a "tit" which is mounted in a different location.

Sorry to be responding to a old topic...
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Postby lbh » 05 Oct 2007, 13:23

Hey

Im not a mechanic but a pilot... lj_dekker I dont quite get your story... When did they select WAI? Right after TO or at FL330?
Well first... I think to recall no max split limit between L and R duct? But more than 10 is not normal.
If any find a limit please tell.
Selecting WAI on at FL330 where the OAT is -51 does not make sence! Especially if you might have a pneumatic problem. TAI is taken off no later than -40 OAT. WAI is only on shortly when ice has build up, unless in holding during special conditions.
Selecting WAI on at FL330 is close to the recommendation from Boeing. And if one duct is as alarming low as 5 PSI well?? Its not recommended from Boeing to use WAI above fl350 according to FCOM VOL 1 SP 16.11 "Caution: Use of wing anti ice above approximately FL350 may cause bleed trip off and possible loss of cabin pressure." There are some articles on MyBoeingFleet.com regarding this. It goes for both CL and NG!

Lasse
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Postby lj_dekker » 21 Oct 2007, 13:50

Hi Lasse,

They selected wai near fl330 so that was indeed the cause and not such a bright idea. The limits for duct pressure for the left and right duct 42 psi +- 8 psi. The fault isolation manual states that when l + r pointers are not the same it is to be called a split. But i think that with the 'split' they mean that one of the pointers is out of its limits of 42 +-8 psi. Right?
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Postby lbh » 24 Oct 2007, 00:23

Hey Lj_dekker

I dont have the FIM unless its the same as AMM part II? So Im therefore not sure of the exact defintion and remember Im a pilot not mechanic. But I would call it a spit if L or R is not the same. But it can still be within limits of +-8...
But the 42 psi +- 8 is a gound setting with max 80% N1 and no bleed requrements but that still doesnt explain the big diff of 40 psi and 5 psi in air...? Did the A/C pass that ground limit when you did the test? How with engines in idle? Could sound to me its something with the low pressure valve??

/Lasse
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Postby lbh » 24 Oct 2007, 00:29

Hey Lj_dekker

I dont have the FIM unless its the same as AMM part II? So Im therefore not sure of the exact defintion and remember Im a pilot not mechanic. But I would call it a spit if L or R is not the same. But it can still be within limits of +-8...
But the 42 psi +- 8 is a gound setting with max 80% N1 and no bleed requrements but that still doesnt explain the big diff of 40 psi and 5 psi in air...? Did the A/C pass that ground limit when you did the test? How with engines in idle? Could sound to me its something with the low pressure valve?? How did the story end?

/Lasse
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