Hi everyone,

 

I have a question about the standard operation procedure when commercial airplanes docking at the gate in real world.

 

I know that when 400Hz power and PCA are available, pilots are usually required to use them rather than APU. But I have seen two different procedures:

a. Start APU while Taxiing ---> Taxi to the gate  --->  Switch to APU electricity  ---> Turn off engines --> Connect bridge power and PCA --> Switch to bridge power and PCA --> Shutdown APU

b. Taxi to the Gate ---> Shut down one engine (usually the left one) --> Connect bridge power and PCA --> Switch to bridge power and PCA  --> Shut down main engine.

 

I don't know which procedure is right or more proper. Is there any regulation (by ICAO, FAA, CAA, etc) on this procedure ?

Thanks!

There is no regulation on it.  It comes down to preference.

 

I'm not sure where you live but during the summer most planes cannot cool the cabin on a single engine.  Hence why you hear the APU start. 

 

Out of habit they continue to use the APU in the non summer months.

 

It is perfectly fine to taxi in on one engine without the APU.

 

Most companies would like you to shut down the engine and then use the APU only if its necessary for cabin cooling.

Majority of airlines keep the APU running if the plane is doing a quick turn. Yes, you're burning Jet A but in the grand scheme of things it's not as much as keeping an engine running. 

 

For longer turns, they'll go with scenario A you outlined. Come to think of it the only time I ever see scenario B happen is for a regional prop. Just feather the engines (if its a free turbine) and connect the power then shut down. 

 

Hope this helps!

There is no regulation on it.  It comes down to preference.

 

I'm not sure where you live but during the summer most planes cannot cool the cabin on a single engine.  Hence why you hear the APU start. 

 

Out of habit they continue to use the APU in the non summer months.

 

It is perfectly fine to taxi in on one engine without the APU.

 

Most companies would like you to shut down the engine and then use the APU only if its necessary for cabin cooling.

 

Hi, FormSF3, Thank you for your reply!

 

Since there is no regulation, I guess that it depends on airliners or pilots.

 

I live in China. Recently the Civil Aviation Authority of China (CAAC) is trying to reduce APU usage to cut down fuel consumption and green gas emission. I've just read some information and I am a bit curious about that.

 

Again, thank you so much!

 

 

 

 

Majority of airlines keep the APU running if the plane is doing a quick turn. Yes, you're burning Jet A but in the grand scheme of things it's not as much as keeping an engine running. 

 

For longer turns, they'll go with scenario A you outlined. Come to think of it the only time I ever see scenario B happen is for a regional prop. Just feather the engines (if its a free turbine) and connect the power then shut down. 

 

Hope this helps!

 

Hi Avi8tor1, thank you for your reply.

 

As you say, scenario B seems not to be a common one, or at least not a common scenario for jet planes.

 

But one thing is clear - procedure A is using by many airliners.

 

Thank you for your information!