CRJ Start up

[tangjuice81 2]

I have a slight problem. When I go to start the engines there is no air transferred from the APU to the engines. The inlets are closed and no air is going to the engines. Here is an example. 

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Need help. Thank you. 

[gabrieldonate 2]

3 hours ago, tangjuice81 said:

I have a slight problem. When I go to start the engines there is no air transferred from the APU to the engines. The inlets are closed and no air is going to the engines. Here is an example. 

Please login to display this image.

 

Need help. Thank you. 

 

I had the same issue and it has been reported in this thread.

 

A temporary fix that works for me is:

-Set the plane to its "Ready to Taxi" state

-Let it complete the configuration and the engines start. (It's best if you get the "Aircraft Configuration Complete" banner message.)

-Then go back to "Cold & Dark" state. 

 

The engines should start up after doing that. Let me know if it works out!

 

[Hans Hartmann [OLD] 1419]

That's a visual issue, nothing that really has consequences. In fact, the valves are only displayed as open when the engines are running. That's to late and will be fixed. Anyway, this does not influence the startup itself.

[Guest Jo va Bra]

Same problem. Start Switch does'nt light op

I go to the Cold&dark status but i got the message: Configuring aircraft. Please wait.... so i'm waiting for 10 minutes nothing happend.

:-((

[JRBarrett 675]

I have a slight problem. When I go to start the engines there is no air transferred from the APU to the engines. The inlets are closed and no air is going to the engines. Here is an example. 

 

Need help. Thank you. 

 

The valves you see in the ECS graphic don't do what you think they do. They are outlet valves, not inlets. They only open after the engine is running to let bleed air flow TO the main duct FROM the engine. The ducts that send APU bleed air to the engine starters are not shown in the airplane's system pages.

 

[tangjuice81 2]

8 hours ago, gabrieldonate said:

 

I had the same issue and it has been reported in this thread.

 

A temporary fix that works for me is:

-Set the plane to its "Ready to Taxi" state

-Let it complete the configuration and the engines start. (It's best if you get the "Aircraft Configuration Complete" banner message.)

-Then go back to "Cold & Dark" state. 

 

The engines should start up after doing that. Let me know if it works out!

 

Thanks I'll try that. 

31 minutes ago, JRBarrett said:

 

The valves you see in the ECS graphic don't do what you think they do. They are outlet valves, not inlets. They only open after the engine is running to let bleed air flow TO the main duct FROM the engine. The ducts that send APU bleed air to the engine starters are not shown in the airplane's system pages.

 

Thank you for the clarification. 

[Hans Hartmann [OLD] 1419]

44 minutes ago, JRBarrett said:

They are outlet valves, not inlets. They only open after the engine is running

OK, so I didn't make a mistake there. Thanks.

[JRBarrett 675]

44 minutes ago, JRBarrett said: They are outlet valves, not inlets. They only open after the engine is running

OK, so I didn't make a mistake there. Thanks.

 

You definitely wouldn't want those valve to open before the engine is started or you would have hot APU bleed air being directly injected into the 10th stage section of the (non moving) engine compressor. That would not be good!

 

The actual bleed air system has a one-way check valve in the duct to prevent back-pressurizing the engine in case the main outlet valve fails in the open position, but that is not shown in the simplified system display.

[Hans Hartmann [OLD] 1419]

Do you have a rough idea when they open? At a certain N2 may be?

[JRBarrett 675]

30 minutes ago, Hans Hartmann said:

Do you have a rough idea when they open? At a certain N2 may be?

 

Unfortunately I can't answer that for the 700/900, as it is normally under the control of the bleed air computer, and I don't have access to detailed maintenance publications for those models. On the CRJ 200 I maintain, the pilots have to manually configure the bleed sources. Typically, they would not open either engine bleed valve until both engines are fully started and stabilized. The inlet valves to the packs are shut down before engine start to maximize APU bleed air pressure. The packs are re-enabled once start is complete.

 

First they close the isolation valve, which shuts off the APU supply to the right bleed air duct. The right pack will momentarily shut down when it loses its bleed supply, since the isolation valve is between the APU and the right side bleed air duct. Once the isolation valve is commanded closed, they then open the right engine bleed valve, and the right pack comes back online. Then, they close the APU bleed valve, which causes the left pack to momentarily shut down. Finally, they open the left engine bleed valve which brings the left pack back online. Finally, they re-open the isolation valve.

 

This sequence prevents any section of the main bleed air duct from being pressurized by the APU and engines at the same time.

 

In the 200, after landing, the opposite sequence is followed to bring the APU bleed back online. 1. Isolation valve is closed. 2. Left engine bleed valve is closed. 3. APU bleed valve is opened, 4. Right engine bleed valve is closed. 5. Isolation valve is re-opened. 

 

I would think the bleed air computer in the 700/900 probably follows a similar logic. Typically on most jet engines, you do not want to extract any bleed air from the engine compressor until the engine is fully started and stabilized, otherwise it can lead to hung starts or hot start - and you do not want to pressurize the main bleed ducts from the engines and APU at the same time.

 

In the 200, they normally leave the APU running until reaching 10,000 feet in the climb, with the APU bleed air supplying both packs. This allows the engines to produce maximum thrust for takeoff and initial climb.     

[Hans Hartmann [OLD] 1419]

I will ask one of the CRJ pilots to take a look on his next flight.

[JRBarrett 675]

I looked at the valves on the ECS synoptic during engine start, and it appears that they are all sequencing in the correct order to bring the engine bleeds on line while isolating the APU. The engine bleed valves might be opening a little too quickly, but other than that, it all looks right to me.

 

Jim Barrett

 

[Hans Hartmann [OLD] 1419]

OK. Thanks Jim.

[tangjuice81 2]

8 hours ago, JRBarrett said:

 

Unfortunately I can't answer that for the 700/900, as it is normally under the control of the bleed air computer, and I don't have access to detailed maintenance publications for those models. On the CRJ 200 I maintain, the pilots have to manually configure the bleed sources. Typically, they would not open either engine bleed valve until both engines are fully started and stabilized. The inlet valves to the packs are shut down before engine start to maximize APU bleed air pressure. The packs are re-enabled once start is complete.

 

First they close the isolation valve, which shuts off the APU supply to the right bleed air duct. The right pack will momentarily shut down when it loses its bleed supply, since the isolation valve is between the APU and the right side bleed air duct. Once the isolation valve is commanded closed, they then open the right engine bleed valve, and the right pack comes back online. Then, they close the APU bleed valve, which causes the left pack to momentarily shut down. Finally, they open the left engine bleed valve which brings the left pack back online. Finally, they re-open the isolation valve.

 

This sequence prevents any section of the main bleed air duct from being pressurized by the APU and engines at the same time.

 

In the 200, after landing, the opposite sequence is followed to bring the APU bleed back online. 1. Isolation valve is closed. 2. Left engine bleed valve is closed. 3. APU bleed valve is opened, 4. Right engine bleed valve is closed. 5. Isolation valve is re-opened. 

 

I would think the bleed air computer in the 700/900 probably follows a similar logic. Typically on most jet engines, you do not want to extract any bleed air from the engine compressor until the engine is fully started and stabilized, otherwise it can lead to hung starts or hot start - and you do not want to pressurize the main bleed ducts from the engines and APU at the same time.

 

In the 200, they normally leave the APU running until reaching 10,000 feet in the climb, with the APU bleed air supplying both packs. This allows the engines to produce maximum thrust for takeoff and initial climb.     

Great explanations. I always thought that the APU was shut off prior to take off but every aircraft is different. 

[JRBarrett 675]

45 minutes ago, tangjuice81 said:

Great explanations. I always thought that the APU was shut off prior to take off but every aircraft is different. 

 

I'm not sure what standard procedures are for the 700/900, (and it may vary by operator) - but for the 200 it is typical to leave the APU on to supply the packs during takeoff and initial climb. The engines on the 200 are the smallest of the CF34 series, and can use all the help they can get!

 

Jim Barrett

[jpcambre 3]

I'm having this problem in the Cold & Dark state.

 

I have found the cause is the bleed valves default to CLOSED and will not toggle to auto no matter what I try.

[Hans Hartmann [OLD] 1419]

9 hours ago, jpcambre said:

I'm having this problem in the Cold & Dark state.

 

I have found the cause is the bleed valves default to CLOSED and will not toggle to auto no matter what I try.

You mean the knob on the overhead panel doesn't move?

[jpcambre 3]

Yes it moves for a half a second and then goes back to closed. I've had this glitch sporatically. It seems to be related to starting with cold and dark, but not every time. What I've had to do is select the plane again from vehicle selection and set it back to cold and dark and that usually fixes it. Its annoying though because I don't always notice it and will have to set the plane back up in the fms, etc.

[Hans Hartmann [OLD] 1419]

I don't understand the reason for this as well. It's just a normal knob. Animation code and settings are identical to about a dozen other knobs. It's the same mythical problem as with the yoke. There's simply no explanation why that is happening.