Ok fellas so the following is what we got here copying and pasting our posts together since I'm sitting here sick in bed. Maybe I'm sick for spending so much time with it hahahah.
I sent the following to be verified by a Bombardier Engineer to see wht he says. meanwhile anyone have any more comments, ideas or knowledge. Thanks for your help with this fellas.
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1. All valves associated with the 10th stage bleeds are spring-loaded CLOSED and require air pressure as well as electricity (electro-pneumatic) for them to move OPEN with their associated PBA pushed in. The 14th Stage ISOLATION valve operates the same way. Spring loaded closed when PBA flush/out and electro-pneumatically open when PBA pushed in as long as it has both electricity AND air.
2. On the entire Bleed Air panel, the L & R 14th stage valves are the only ones that are spring loaded OPEN when no electrical power and/or air pressure is supplied to them, and they need air pressure to move them to the CLOSED position when their PBA's are pushed OUT/OFF position. If they were to lose electrical power with their respective PBA's in the out/off position the would move to the open/on positon making 14th stg bleed pressure available to the Anti Ice system if needed if a wire to the valves were to break. With their respective PBA in the in/on position the valves are sprung to the open position with the electric part of the valve not being energized. We normally leave the PBA's for the 14th stage valves in the IN / ON position so as not to keep the valves energized to the closed position for no reason and so bleed pressure is always available to the Wing and Cowl AI systems. A reason to close them (PBA OUT) would be if there were a 14th stage duct rupture.
3. Because all valves need air pressure to move them, they do not always move when the appropriate switch is pressed unless there is electrical power to direct/energize them and air pressure to move them. It is easiest to remember that when the switches are selected, IN is OPEN and OUT is closed. The valves will move when the air pressure reaches them.
4. (Side note) The APU LCV valve never allows itself to be supplying APU air pressure lower than is being applied from a 10th stg engine bleed source. If during operation it senses 10th stg bleed pressure on the 10th stg duct higher than it is supplying it will automatically close regardless of the LCV PBA being in the IN/ON/OPEN position.
5. The left and right 10th stage engine bleed valves AND the 10th stage ISOLATION valve open automatically regardless of their PBA position (in or out) when the start button/PBA is pushed.
6. In a normal APU assisted start we have the 10th stg ISOL valve PBA in the pushed IN / ON / OPEN position even though it will open regardless of the bleed source (APU LCV valve or 10th stg engine bleed source) when pushing in the START PBA and is then closed PBA OUT position when transferring bleeds on TO above 1500 AGL to isolate the L & R 10th stage systems.
7. A cross-bleed start for the CRJ requires advancing the thrust lever of the engine that was previously started by a ground air-start cart (if APU INOP) until you get 60 psi from the operating engine. The only way you can read the psi is by going to the ECS Eicas page to see the 10th stg pressure by opening the 10th stage engine bleed on the operative engine to supply the 10th stage duct with pressure although the book calls for both engine 10th stage bleed valves to be open. Unless you do so by pushing in the operative engine 10th stage engine bleed PBA, there's no pressure indication on the EICAS ECS page. Once you've verified the pressure, on the eicas page you can then start the other engine (knowing you have sufficient pressure of 60 psi to be utilized for the air turbine starter).
8. The book also states for a cross bleed start that the operating engine's RPM needs to be at least 85% N2 or higher, so that would be another way to indirectly check for appropriate pressure without actually checking the ECS synoptic page and not requiring pushing in the operative engine 10th stage engine bleed PBA since it will automatically open when the START PBA is pushed in. But this is only for system knowledge since it is not according to the procedures laid out in the book.
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Question: In our line operation book (QRH) it has us make sure that the 14 stage PBA's are pushed in (valve open position).
I was told that the reason we make sure they are open are to help ensure against a hung start if we were to loose electrical power........... I also heard on the CRJ that the 10th stage is used for this and since the 10th stage is pressurized for the engine start it can't be used to unload the compressor.
This info in the paragraph above doesn't rest well with my present systems knowledge.
Most jet engines I have been involved with namely Pratt & Whitney JT3D-3b & -7 and JT8-7 through 200 series of which I was a turbine and compressor component buildup and assembly mechanic, test cell operator, and inspector as well as line A&P and I.A. and then Flight Engineer and then Copilot on have a Pressure Ratio Bleed Valve or Relief Valve which is open ahead of the diffuser section that is open during engine start to help unload the compressor keeping the compressor spinning freely to help avoid hung starts.
Can you tell me anything or can you refer me to anyone who can explain why the 14th stage PBA's are verified in the ON / OPEN position during Crossbleed beyond the fact that it calls for it in the QRH / line operations handbook.
Thankyou respectfully,
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