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fjsharry

Two engine can't maintain FMS cruise speed

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When my engine two get high temp and i follow QRH to shutdown engine and descent to FL300(in fmc crz pref max altitude),and notice can not maintain fms speed(magenta) in FL300,it's normal procedure?

And what function for overboot bar?


Jia-Hsing Fu

 

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When my engine two get high temp and i follow QRH to shutdown engine and descent to FL300(in fmc crz pref max altitude),and notice can not maintain fms speed(magenta) in FL300,it's normal procedure?

 

Have you confirmed the "ENG OUT" page on the FMC? That page will give you the optimum speed and altitude to fly at.

 

And what function for overboot bar?

 

If you push the thrust levers through the overboost bar, the engines will provide the maximum amount of thrust available. Useful if you are about to hit something hard or need to get out of the situation quickly.


Kenny Lee
"Keep climbing"
pmdg_trijet.jpg

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@Kenny Q1 Yes,i was set "eng out",and have show " /32XXX" in max altitude. But when descent,it's can not keep speed with AT at that altitude.

Q2 And i notice can not re-engage A/T after use overboot bar,it's normal?


Jia-Hsing Fu

 

ACH0978.jpg

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But when descent,it's can not keep speed with AT at that altitude.

 

The way I understand it is that when the engine out has been confirmed, the current speed will remain the target speed. Set the desired altitude on the FCP. When the speed cannot be maintained, the speed target will become the driftdown speed. The aircraft will begin to descend when this speed is reached and the altitude is set in the FCP.

 

This descent is controlled by pitch to maintain speed and thrust levers at MCT. The D/D speed is shown on all PERF pages at line 1L as well as the ENG OUT speeds at their usual location.

 

If the descent rate slows to less than -100 fpm for more than 60 seconds, the descent rate will change from the D/D to a vertical speed of -100 fpm.You can change this on the FCP and then reengage PROF.

 

To change from the descent mode to cruise mode, you need to enter cruise information on the INIT page. The speed target will be the ENG OUT ECON cruise speed. The thrust limit will remain in MCT.

 

And i notice can not re-engage A/T after use overboot bar,

 

I'm not sure about this, but reset the overboost bar and the AT may re-engage.


Kenny Lee
"Keep climbing"
pmdg_trijet.jpg

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Q2 And i notice can not re-engage A/T after use overboot bar,it's normal?

 

When the overboost bar is pushed the engines go to alternative mode. You have to turn them back to normal (on the overhead, you will see there altn lights). Then you will be able to engage the Auto thrust again. The overboost bar has to be on normal too.

 

Regards,

Manfred


Manfred G.

 

Ships are cooler that you think.

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@Kenny My procedure is setting confirm engine out in fmc,and turn low altitude on FCP then pull to descent,push FMS SPD AND PROF after reached altitude,but IAS will little drop down...Maybe i will test this later

 

@Manfred Yes,FADEC will turn to alter after push overboot,but i was reset overboot and click ALT to normal(light out),but still can not re-engage A/T.

 

Here is after confirm engine out,and seem fmc target spd is low for only two engine workload.

engineout.jpg


Jia-Hsing Fu

 

ACH0978.jpg

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Found it in the FMS manual at FMS.110.16. There is a lot of information but to simplify. The target speed remains the same, you have to choose correct speed. However the aircraft will start descending if you reach driftdown speed (but only if the MCP altitude is dialed down).

 

Still searching for the ATS engagement...

 

Regards,

Manfred


Manfred G.

 

Ships are cooler that you think.

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Mmm..agree,flow boeing and McDonnell Douglas both system,i thought mcDonnell manual not like boeing have complete procedure,most situation was mention less information.


Jia-Hsing Fu

 

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