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Trimeresurus
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In your airline, do you start the APU upon landing?

Sun Oct 04, 2020 12:51 pm

Or do you wait for the ground crew to connect the ground power and/or the air cart(how often are air carts used anyway, for air conditioning)? If you do, and wait for the ground power, how long does it take for you to shut off the engine(s) after docking is completed?

Also the the port for external air is seemingly very close to the engines, is it safe to connect the air hose to it's place when the engines are running(sure you can shutoff the engine directly behind it, but in a narrow body ground crew would still have to get pretty close to the other one)? And isn't the fuel savings by not running the APU offset by extra engine time at the gate?
 
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Starlionblue
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Re: In your airline, do you start the APU upon landing?

Sun Oct 04, 2020 1:13 pm

On the A330/A350 at my airline, we start the APU while taxiing in. We aim for single engine taxi to save fuel, and we do not shut down an engine until the APU is on.

When we park, we shut down the engine(s). Once they are off, we switch the seatbelt sign off. This signals the cabin crew to disarm the doors. Once the doors are disarmed, we switch off the beacon, indicating it is safe to approach the aircraft.

The whole process is a matter of 20-30 seconds after setting the park brake.

In your example, the ground crew would not connect external air unless the engines are off, as indicated by the beacon being off. They'd also check with the flight crew that the APU bleed is off before connecting external air. Connecting external air with the APU and/or engine bleed on is bad.

Taxiing on one engine with the APU running saves fuel even if you only do it for one minute.
 
ACMIdriver
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Re: In your airline, do you start the APU upon landing?

Sun Oct 04, 2020 2:02 pm

On the B744, we also start APU on the taxi in as part of the After Landing Procedure. Sometimes we will shut down Number 3 if a long taxi is expected, but it's not common at the airports we fly into.

As for the fuel savings, during my Line Training I remember once forgetting to start the APU on the taxi in. Arriving at the gate, about to switch to the APU GENs but seeing no AVAIL light I realised what I had done. Needless to say it seemed like one of the longest and most awkward 30 seconds in my life sitting at the gate with the engines whirring away waiting for the APU to spool up, with the passengers kept seated wondering what was going on... To add to my embarrassment in the mean time the ground engineer had just plugged his headset in and chimed in on the intercom: "Is everything alright, do you need ground power sir, APU inop?"

So yes, I'm sure not starting it definitely burns more fuel, at least in that case.
 
CosmicCruiser
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Re: In your airline, do you start the APU upon landing?

Sun Oct 04, 2020 2:21 pm

Depending on the location we would be told if ground power was available or not. If it was we didn't start the APU.
 
Tristarsteve
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Re: In your airline, do you start the APU upon landing?

Sun Oct 04, 2020 3:45 pm

Here at ARN the rule is that the ground crew do not cross the red line to approach the aircraft until the engines and beacon are off. So you need to start the APU after landing, or you will have no power at the gate. If the APU is inop, then the pilot tells the handling agent and ground power is connected as an exception. As soon as the ground power is on line, the APU is switched off to comply with airport regulations.
When SAS used to operate MD80s, then ground power was connected with the engines running, and the APU was not started on arrival. But when the B737-500 and 600 arrived in service, the no approach rule was instigated. The ground power socket is close to the prohibited area for the engine intake on these aircraft, and the rule was made universal.
 
bradyj23
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Re: In your airline, do you start the APU upon landing?

Sun Oct 04, 2020 3:54 pm

At my former airline on the CRJ we would often shut down the left engine and wait until the ground crew plugged in ground power before shutting down the right engine. We were told that saved more money than running the APU. Current airline, on the 737, we always start the APU on the way in.
 
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DocLightning
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Re: In your airline, do you start the APU upon landing?

Sun Oct 04, 2020 3:57 pm

Starlionblue wrote:
Taxiing on one engine with the APU running saves fuel even if you only do it for one minute.


Do you alternate which engine you shut down for taxi?
 
FGITD
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Re: In your airline, do you start the APU upon landing?

Sun Oct 04, 2020 5:04 pm

Where I've worked connecting air with engines still running was always prohibited. Too much risk, too little benefit. It's something that could always wait an extra minute or two for engine shutdown.

Connecting ground power with an engine running wasn't uncommon. I work widebodies most frequently, and it more or less always went the same. Shut down starboard side during taxi or on arrival, move in and hook up.

Only thing I never liked is usually ground power comes from a unit on the jetbridge, which is of course on the left side. Boeing in their infinite wisdom tend to put GPU receptacles on the right side. So we'd have to move the jetbridge in close, plug in, and then carefully reposition the bridge to 2L. Not a big deal with a good team, but very easy for the jetbridge operator to forget they're plugged in.

But compared to air starts, GPU is a walk in the park
 
Max Q
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Re: In your airline, do you start the APU upon landing?

Sun Oct 04, 2020 5:19 pm

We Always start the APU after landing, false economy to plan on external power being connected quickly after parking and you burn far more fuel running an engine waiting for this than the cost of cranking the APU


Occasionally I’ve flown with FO’s that hold off starting the APU after landing, planning to crank it as we get closer to the gate and save a few pounds of fuel. Bad idea as they often forgot, I did too and then we’re having to leave an engine running for electrical power after we’re parked and have to wait for the APU to start


Best procedure and our policy is to always start it, once parked and shut down with external power connected then evaluate whether to keep it running for heating or cooling if no external air is connected. I always prioritize passenger comfort so it will stay running if there’s a need for it


One other thing, on an autoland we will start the APU in flight before the approach (757/67) to provide electrical redundancy in the event of an engine driven generator failure
 
dakota558
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Re: In your airline, do you start the APU upon landing?

Sun Oct 04, 2020 6:22 pm

Tristarsteve wrote:
Here at ARN the rule is that the ground crew do not cross the red line to approach the aircraft until the engines and beacon are off. So you need to start the APU after landing, or you will have no power at the gate. If the APU is inop, then the pilot tells the handling agent and ground power is connected as an exception. As soon as the ground power is on line, the APU is switched off to comply with airport regulations.
When SAS used to operate MD80s, then ground power was connected with the engines running, and the APU was not started on arrival. But when the B737-500 and 600 arrived in service, the no approach rule was instigated. The ground power socket is close to the prohibited area for the engine intake on these aircraft, and the rule was made universal.


In Norway, the APU is normally not started on taxi in. The GPU will be connected a few seconds after the aircraft has parked. Even on the -500 and -600 there is plenty if distance from the ground power hatch to the red "danger" line on the fuselage. This seems to be the case at other airports in Europe I've been to, while the opposite appears to be true in the states for some reason.
The aircraft I fly does not have an APU, so the GPU must be connected before we can shut down the engines.
 
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Starlionblue
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Re: In your airline, do you start the APU upon landing?

Mon Oct 05, 2020 12:30 am

DocLightning wrote:
Starlionblue wrote:
Taxiing on one engine with the APU running saves fuel even if you only do it for one minute.


Do you alternate which engine you shut down for taxi?


We do not alternate.

On the A330 we always shut off engine 2 (right hand) because engine 1 powers the blue hydraulic system, which in turn powers alternate braking. Even if you lose normal braking and don't have alternate braking, you'd still have the accumulator, but better safe then sorry. (Normal braking is powered by the green hydraulic system, which is powered by both engines.)

On the A350 the hydraulics are symmetrical so you can shut down either engine. Often it will still be engine 2 out of habit, but if you plan to make tight turns in a certain direction while taxiing in, you can turn off the engine in that direction. E.g. if you have a sharp left turn into the bay you'd turn off number one engine to avoid turning against power while taxiing slowly. If you happen to slow down too much in a tight turn you need a lot of power to get going again, and even more if the "wrong" engine is shut down. Most bays are also slightly uphill for drainage, which adds to the fun times.

Max Q wrote:

Occasionally I’ve flown with FO’s that hold off starting the APU after landing, planning to crank it as we get closer to the gate and save a few pounds of fuel. Bad idea as they often forgot, I did too and then we’re having to leave an engine running for electrical power after we’re parked and have to wait for the APU to start



On the A330/A350 "APU - START" is on the after landing checklist. A good mental reminder. Even if you delay APU start a bit, the checklist will be hanging over you, so to speak, since you can't complete it without the APU.
 
Sancho99504
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Re: In your airline, do you start the APU upon landing?

Mon Oct 05, 2020 2:17 am

When I worked on the ramp, pilots generally taxied in on #2 so that we could hook up ground power and air once they hit the block. Mostly though, APU was running and whoever was working in the rear bin would hang the preconditioned air hose on the net so they didn't die back there.
 
shamrock137
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Re: In your airline, do you start the APU upon landing?

Mon Oct 05, 2020 2:43 pm

Trimeresurus wrote:
Also the the port for external air is seemingly very close to the engines, is it safe to connect the air hose to it's place when the engines are running(sure you can shutoff the engine directly behind it, but in a narrow body ground crew would still have to get pretty close to the other one)? And isn't the fuel savings by not running the APU offset by extra engine time at the gate?


In my experience working on the ramp, with narrow bodies the crew would shut down #2 engine during taxi, or after setting the parking brake, and we would connect ground power while the jetbridge was being attached. Then the crew would shut down the #1 engine once the aircraft was on ground power. The APU would not be started. We would then complete the arrival walk around, and connect the ground air. With wide bodies, the APU would normally be on for taxi in, the crew would shut down the engines and we would connect the ground power, usually not the ground air as it wasn't really powerful enough to make a difference, especially in the summer.

Personal experience though, some airlines seem to be almost militant about not starting the APU until the last moment. UA and TK come to mind. Sitting onboard a TK 330, having boarded in one of the last groups, and waiting 15 min for the completion of boarding and closeout while relying on the ground air is rough. Even in the mild SFO weather, the ground air never seems to be able to keep a 739 from feeling hot and stuffy.
 
DiamondFlyer
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Re: In your airline, do you start the APU upon landing?

Mon Oct 05, 2020 3:29 pm

Where I work, depending on the airframe, it's either started shortly after landing, or at 10,000 ft on approach.
 
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Starlionblue
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Re: In your airline, do you start the APU upon landing?

Mon Oct 05, 2020 11:11 pm

shamrock137 wrote:
Trimeresurus wrote:
Also the the port for external air is seemingly very close to the engines, is it safe to connect the air hose to it's place when the engines are running(sure you can shutoff the engine directly behind it, but in a narrow body ground crew would still have to get pretty close to the other one)? And isn't the fuel savings by not running the APU offset by extra engine time at the gate?


In my experience working on the ramp, with narrow bodies the crew would shut down #2 engine during taxi, or after setting the parking brake, and we would connect ground power while the jetbridge was being attached. Then the crew would shut down the #1 engine once the aircraft was on ground power. The APU would not be started. We would then complete the arrival walk around, and connect the ground air. With wide bodies, the APU would normally be on for taxi in, the crew would shut down the engines and we would connect the ground power, usually not the ground air as it wasn't really powerful enough to make a difference, especially in the summer.

Personal experience though, some airlines seem to be almost militant about not starting the APU until the last moment. UA and TK come to mind. Sitting onboard a TK 330, having boarded in one of the last groups, and waiting 15 min for the completion of boarding and closeout while relying on the ground air is rough. Even in the mild SFO weather, the ground air never seems to be able to keep a 739 from feeling hot and stuffy.


Ground air in most places seems adequate to keep the cabin at a decent temperature when it is warm out, but only as long as there are no passengers on board.
 
EssentialPowr
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Re: In your airline, do you start the APU upon landing?

Mon Oct 05, 2020 11:40 pm

In the summer time the 737-800, 900 and 900ERs need 2 packs operating to stay comfortable with a full pax load. Taxiing in single engine with the APU running both packs and the Number 2 engine shut down works well. With no electrical load on the APU the right pack can be run in “Hi” and the left pack in “Auto”.
 
Alias1024
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Re: In your airline, do you start the APU upon landing?

Tue Oct 06, 2020 8:28 pm

Company policy is to start the APU, but not always immediately after landing. We are encouraged to time the APU start so that it is available for electrical and air conditioning just before parking. We will taxi the A320 single engine (#1 engine) with the APU off both taxi out and taxi in. The yellow hydraulic electric pump is turned on so the PTU doesn’t run constantly trying to pressurize that system.

Previous regional encouraged us to leave the APU off for taxi in and just wait for power. Reason was that some APU maintenance functions are cycle based and they said it was $30 every time we started the APU. They wanted to save one cycle per aircraft turn. One engine at idle would burn less than 300 pounds of fuel per hour so it took several minutes of idle power at the gate before it was more expensive than the extra APU start.
 
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Horstroad
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Re: In your airline, do you start the APU upon landing?

Tue Oct 06, 2020 11:28 pm

At my airline they (I'm not a pilot) don't start the APU at our home station. Or whenever there is a GPU available at an outstation. Someone calculated that it consumes more fuel to start the APU than to keep an engine running for the 30 seconds to a minute until external power is available.
We don't transport pax, so air conditioning is not required most of the times. When it is, the APU is used before departure... but after arrival the cargo is unloaded within short times anyways, so it wouldn't make much of a difference.
On the MD11 they leave the #2 engine running, so there's no hazard at all for the ground crew. On the 777 usually the L/H engine is kept running until the GPU is connected.
The APU is only started when the ground handling crew is not present when the aircraft arrives. This can happen from time to time, especially during the current events of cost savings. When it is obvious that external power wont be available within the next 2-3 minutes, the APU will be started.
The APU is also used on outstations where a GPU is not available, or where the use of the APU is cheaper than the fee for a GPU, or when air conditioning is needed for temperature sensitive cargo.
 
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DocLightning
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Re: In your airline, do you start the APU upon landing?

Wed Oct 07, 2020 2:52 am

Starlionblue wrote:
DocLightning wrote:
We do not alternate.


So does that not lead to uneven wear on the engines?
 
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Starlionblue
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Re: In your airline, do you start the APU upon landing?

Wed Oct 07, 2020 7:06 am

DocLightning wrote:
Starlionblue wrote:
DocLightning wrote:
We do not alternate.


So does that not lead to uneven wear on the engines?


I'm sure it does, ever so slightly. However:
- One engine taxi is only a few minutes per flight.
- Taxi is at idle power or barely more. Not exactly a high wear regime.
- Engines are complex and don't wear identically even on the same airframe.
- Apart from when the plane leaves the factory, engines aren't "symmetrical" on any given airframe. One engine might be brand new or have just come back from overhaul, while the other might have done thousands of hours on the wing.
 
flybaurlax
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Re: In your airline, do you start the APU upon landing?

Wed Oct 07, 2020 8:16 pm

DocLightning wrote:
Starlionblue wrote:
DocLightning wrote:
We do not alternate.


So does that not lead to uneven wear on the engines?


In terms of engine longevity, it doesn't really make a difference. The wear and tear normally comes from the full thermal cycle, with the harshest part in the takeoff and climb.
 
mwthekoopinator
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Re: In your airline, do you start the APU upon landing?

Thu Oct 08, 2020 6:32 am

With my regional, the company would rather the pilots come in on engines, and have us hook up power as soon as the aircraft chocks in, with chocks and GPU being the first two things we (ground crew) take care of when the aircraft parks. Per policy, PCA is to be connected by A+7 as needed. Usually on the Q400, we get power hooked up as soon as the props feather and the APU is only used for climate control when we aren't using a PCA unit. With the E175, they almost always have the APU on at taxi-in and have engines off by the time we hook up our power, but will shut down to GPU power as part of the terminating checklists.
 
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DocLightning
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Re: In your airline, do you start the APU upon landing?

Sat Oct 10, 2020 9:59 pm

flybaurlax wrote:

Starlionblue wrote:


Thank you both for being such informative and helpful members of this community.
 
Redbellyguppy
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Re: In your airline, do you start the APU upon landing?

Mon Oct 12, 2020 2:22 pm

I typically start the apu as part of my after landing flow... flaps up, start apu, start switches off, unnecessary lights off, window heat off, auto brakes off, call operations... by the time it has been started and warmed up for a minute, we are often reasonably close to the gate. Packs on apu bleed for passenger comfort, electrics bussed up so we can kill engines any time.

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