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SaschaYHZ
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Electrical Power during One Engine Operation

Wed Aug 30, 2017 10:35 pm

Sorry if this has been discussed before...tried searching the forum and couldn't really find an answer. Does running one engine on the ground provide enough power for an aircraft? As in, if you're approaching a hard stand, would turning off the starboard engine, perhaps so crew can safely approach the aircraft and save APU usage, while leaving the port engine running until the GPU is connected and power turned on there.
 
rendezvous
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Re: Electrical Power during One Engine Operation

Wed Aug 30, 2017 11:03 pm

Yes, one engine provides adequate power, just as it does following an engine failure in the air.
Shutting down one engine to allow ground personnel to approach the aircraft generally isn't practical. When the engine is running, the red beacon will be operating - people should not approach the aircraft. If you turn it off so they can approach, then there is still an operating engine with no beacon to warn anyone. One of the practical solutions to this is to the have the APU in the first place. Some airports these days use ground power as a preference over APU use - less noise and less carbon emissions.
 
shamrock137
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Re: Electrical Power during One Engine Operation

Thu Aug 31, 2017 12:59 am

Yes it does, however an engine uses significantly more fuel then an APU. Many airlines use a single engine to taxi then start the second engine before takeoff, or the opposite, shut one engine down after landing. I know on some smaller aircraft, one engine turns are performed where the aircraft does not have an APU, Dash 8, Metroliner, B1900. Even if a station has a GPU available sometimes they don't have ground air to heat or cool the cabin requiring the engine to be kept running so the cabin doesn't get too hot or cold.
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Max Q
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Re: Electrical Power during One Engine Operation

Thu Aug 31, 2017 4:06 am

Port and Starboard are nautical terms, not used in practice and rarely used at all in aviation.
The best contribution to safety is a competent Pilot.


GGg
 
wa5
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Re: Electrical Power during One Engine Operation

Thu Aug 31, 2017 7:11 am

do pilots simply use "left" and "Right"?
 
Flow2706
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Re: Electrical Power during One Engine Operation

Thu Aug 31, 2017 8:02 am

On the A320 each engine driven and APU Generator is rated at 90kva, which is more than enough to supply the whole electrical system on its own (the RAT still generates 5KVA and the static inverter 1KVA). The only thing that are shed are galley loads. During normal operations with both engine generators running the generator loads are around 17-35% according to the ECAM ELEC page.
Still, if an engine or generator fails in flight it is good practice to start the APU (even though it is mentioned nowhere on ECAM/in the checklists, as it is not a requirement) in order to restore redundancy and supply the galley.
Leaving on engine running on stand is virtually never done on the A320, except for engine tests (if authorized). The APU uses a lot less fuel than the main engines. Obviously you can shut down the APU after external power is connected, even though many crews prefer to leave it running at least until the door is open (it gets rather uncomfortable after a short period of time without air conditioning with a full passenger load and closed doors) or even until the last passenger is disembarked at night time (external power unit sometimes have the bad habit of failing causing the cabin to go into total darkness except for emergency lights which is not what you want if you still have passengers on board). The temperatures in the cabin remain acceptable during normal conditions (in European weather) even with no air conditioning, but during a hot day in summer it may still be a good idea to ask for external air conditioning (or leave the APU running).
wa5, we usually use Nr. 1 or Nr. 2 but left and right are also sometimes used (even though it can cause confusion, as in "your left" or "my left" - but it should be referred to the direction of flight anyway). In some systems different wordings are used, f.e. in the Airbus Hydraulic system (which are called green/yellow/blue instead of 1/2/3).
 
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Starlionblue
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Re: Electrical Power during One Engine Operation

Thu Aug 31, 2017 9:08 am

wa5 wrote:
do pilots simply use "left" and "Right"?


Yep. Never heard port and starboard at my airline.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
SaschaYHZ
Topic Author
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Re: Electrical Power during One Engine Operation

Thu Aug 31, 2017 1:11 pm

Thanks for all the replies! (And I do have some boating behind me, hence my usage of those terms...thanks for correcting!)
 
Woodreau
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Re: Electrical Power during One Engine Operation

Thu Aug 31, 2017 2:18 pm

wa5 wrote:
do pilots simply use "left" and "Right"?


Number 1 and Number 2 engine.

With Number 1 being the left engine.


If it were nautical numbering, the Number 1 engine is the right engine and the Number 2 engine is the left engine. (Odd numbers to starboard, even numbers to port)
i.e. for an aircraft carrier, looking forward from the rear of the carrier, the four propellers and associated main engines are #4, #2, #1, #3. from left to right.
Last edited by Woodreau on Thu Aug 31, 2017 2:21 pm, edited 1 time in total.
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Redbellyguppy
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Re: Electrical Power during One Engine Operation

Thu Aug 31, 2017 2:20 pm

rendezvous wrote:
Shutting down one engine to allow ground personnel to approach the aircraft generally isn't practical.


It's so practical we do it on just about every flight at the top of the parking line taxiing inbound if it wasn't already done on taxi in as soon as cool down time is complete.
 
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767333ER
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Re: Electrical Power during One Engine Operation

Thu Aug 31, 2017 2:42 pm

This is basically what bus ties are for. The engine driven generators are set up such that one is sufficiently capable of supplying power to the while plane, but maybe with some load shedding of non essential equipment.
Woodreau wrote:
wa5 wrote:
do pilots simply use "left" and "Right"?


Number 1 and Number 2 engine.

With Number 1 being the left engine.


If it were nautical numbering, the Number 1 engine is the right engine and the Number 2 engine is the left engine. (Odd numbers to starboard, even numbers to port)
i.e. for an aircraft carrier, looking forward from the rear of the carrier, the four propellers and associated main engines are #4, #2, #1, #3. from left to right.

Unless you're flying the CRJ and then it is left engine and right engine.
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Tristarsteve
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Re: Electrical Power during One Engine Operation

Thu Aug 31, 2017 2:47 pm

Here at ARN Menzies rules that no-one may approach an arriving aircraft with the beacon on. There are exceptions for u/s APU, but every occurence must be coordinated on the radio in advance.
British Airways has exactly the same rule.
 
744lover
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Re: Electrical Power during One Engine Operation

Thu Aug 31, 2017 4:08 pm

Operating the MD-11, I've been in a situation where the APU was MEL'd and the station did not have any ground air-start available (informed to us beforehand via ACARS). The solution was to keep engine 2 running while the aircraft was serviced since its sits high above the ground and the jetblast is nowhere near the working area.

BR,
744lover
 
rendezvous
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Re: Electrical Power during One Engine Operation

Thu Aug 31, 2017 10:26 pm

Redbellyguppy wrote:
rendezvous wrote:
Shutting down one engine to allow ground personnel to approach the aircraft generally isn't practical.


It's so practical we do it on just about every flight at the top of the parking line taxiing inbound if it wasn't already done on taxi in as soon as cool down time is complete.


To clarify, I was meaning it was impractical to have one engine still running on the gate while there are ground personnel around the aircraft. For our operations we have to leave the red beacon on until the engines are shut down - with the exception of plugging in ground power, nobody is allowed to approach the aircraft until the beacon is off. If we were to leave one engine running on the gate, the beacon would have to stay on, and nobody would be able to load/unload the plane.

Are your ground personnel allowed to approach the aircraft and open doors etc when there is an engine still running?
 
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Starlionblue
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Re: Electrical Power during One Engine Operation

Thu Aug 31, 2017 11:35 pm

rendezvous wrote:
Redbellyguppy wrote:
rendezvous wrote:
Shutting down one engine to allow ground personnel to approach the aircraft generally isn't practical.


It's so practical we do it on just about every flight at the top of the parking line taxiing inbound if it wasn't already done on taxi in as soon as cool down time is complete.


To clarify, I was meaning it was impractical to have one engine still running on the gate while there are ground personnel around the aircraft. For our operations we have to leave the red beacon on until the engines are shut down - with the exception of plugging in ground power, nobody is allowed to approach the aircraft until the beacon is off. If we were to leave one engine running on the gate, the beacon would have to stay on, and nobody would be able to load/unload the plane.

Are your ground personnel allowed to approach the aircraft and open doors etc when there is an engine still running?


Nope. And we definitely can't leave an engine running while loading and unloading is going on.

The other exception to beacon on and personnel in proximity would be engine start on external pneumatic pressure.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
SaschaYHZ
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Re: Electrical Power during One Engine Operation

Fri Sep 01, 2017 12:52 am

I meant to clarify that "approach the aircraft" was to simply plug in the GPU to provide power to not need to turn on the APU. So they'd leave the left engine to running until GPU was plugged in, and power turned on...tben everyone else approaches.
 
Redbellyguppy
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Re: Electrical Power during One Engine Operation

Fri Sep 01, 2017 4:57 am

After landing unless I have tight maneuvering to get to the gate, i shut down the right engine as soon as I can to save fuel. Approaching the gate we shut it down so that when we are in the safety zone it is spooled down enough so that the ground power can be plugged in on the right side of the aircraft and the pits can be opened sooner.

If an apu is deferred though, you have no choice. An engine must be started at the gate. And when you get to your destination, the engine must be running until the gpu is plugged in.

Normal operations I transfer electrics and air to the apu approaching the gate and shut down the right engine at the top of the line so the ground crew can get to work without any delay.
 
Flow2706
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Re: Electrical Power during One Engine Operation

Fri Sep 01, 2017 6:55 am

If the APU is U/S external power is indeed plugged in before shutting down the second engine, but this situation is the exception not the norm (increased risk to ground crew).
For the single engine taxi, it has to be carefully considered. Some Taxiways have strong upslopes (f.e. the "bridge" after landing in Frankfurt on 25R) which make single engine taxi impossible as you won't have enough thrust available on one engine. Also some engines need a certain period of cool down (f.e. 3 minutes after high thrust operations on CFM56) which make single engine taxi unfeasible if the taxi time is short.
 
StereoTechque
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Re: Electrical Power during One Engine Operation

Fri Sep 01, 2017 3:46 pm

Starlionblue wrote:

Nope. And we definitely can't leave an engine running while loading and unloading is going on.

The process is loosely called Hot Refueling.
However if carried out, utmost precautions should be taken by the involved personnel ie fire department notified and area manned by same, area barricaded, all commercial activities carried out from the non running engine side, atc notified and pilot standing by and in touch with the ground Atc among others..
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Starlionblue
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Re: Electrical Power during One Engine Operation

Sat Sep 02, 2017 12:29 am

StereoTechque wrote:
Starlionblue wrote:

Nope. And we definitely can't leave an engine running while loading and unloading is going on.

The process is loosely called Hot Refueling.
However if carried out, utmost precautions should be taken by the involved personnel ie fire department notified and area manned by same, area barricaded, all commercial activities carried out from the non running engine side, atc notified and pilot standing by and in touch with the ground Atc among others..


I should have been more clear. It can be done. We just don't do it at our airline.

There's also the issue with the cargo doors only being on one side...
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
GalaxyFlyer
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Re: Electrical Power during One Engine Operation

Sat Sep 02, 2017 1:03 am

Port and Stsrboard in naval aviation.

GF
 
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exFWAOONW
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Re: Electrical Power during One Engine Operation

Wed Sep 06, 2017 3:25 pm

Another benefit of the DC9 is it is relatively safer to do a single-engine turn when in a pinch than your typical wing-mounted engine A/C. ie APU MEL'd and GPU not available. It happens more often in out (spoke) stations where the aircraft won't spend a lot of time and company maintenance forces aren't available. Had to do it many times over my career.
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