Ask The Pilot

[UP4014]

Inside, sorry not a great shot, a grab shot as we say in rail.

 

[Brissy1]

Start up the APU to get the missing engine generator back

I'm not a pilot, not even ppl, but just curious- do the APU functions work off one main engine only?

 

[jb747]

I'm not a pilot, not even ppl, but just curious- do the APU functions work off one main engine only?

APU means "auxiliary power unit". It has nothing to do with the engines, but is actually a separate turbine engine mounted in the tail of the aircraft. The exhaust is quite obvious right at the tip of the tail on most airliners, with the intake generally being next to the fin. They normally run on the ground to provide electricity and air-conditioning whilst the engines are shut down.

If you use the APU to provide bleed air for a/c during take off, it makes slightly more power (and so weight) available for a given runway length (because the engines aren't losing a couple of percentage points of their power to run the bleed). We used that last night departing LAX, to avoid having to taxi to the other side of the airport to use a different runway.

The APU will normally run a couple of generators on the ground. In flight our APU will only run one, but we can use that to fill in for a missing main generator if we need to.

On the twin engined aircraft the APU can normally be both run and started throughout the flight regime. On the 747 it cannot be started in flight, and the 380 can only do so below 20,000'.

 

[Brissy1]

APU means "auxiliary power unit". It has nothing to do with the engines, but is actually a separate turbine engine mounted in the tail of the aircraft. The exhaust is quite obvious right at the tip of the tail on most airliners, with the intake generally being next to the fin. They normally run on the ground to provide electricity and air-conditioning whilst the engines are shut down.

If you use the APU to provide bleed air for a/c during take off, it makes slightly more power (and so weight) available for a given runway length (because the engines aren't losing a couple of percentage points of their power to run the bleed). We used that last night departing LAX, to avoid having to taxi to the other side of the airport to use a different runway.

The APU will normally run a couple of generators on the ground. In flight our APU will only run one, but we can use that to fill in for a missing main generator if we need to.

On the twin engined aircraft the APU can normally be both run and started throughout the flight regime. On the 747 it cannot be started in flight, and the 380 can only do so below 20,000'.

Wow thanks for all that. I never imagined that an APU would, in any practical sense, increase otherwise available thrust (I"ve thought it would in theory, but virtually undetectable). Maybe that's what I sometimes hear with the a/c cutting in/out during taxi - a switch over to/from the APU. But of course I'm really mainly concerned about not running out of ice.

 

[AviatorInsight]

Maybe that's what I sometimes hear with the a/c cutting in/out during taxi - a switch over to/from the APU.

Out on the ramp you can definitely hear the start up and shut down of the APU. On the 737 you'll know when the transfer is made from APU to engine generators and vice versa when there's a quick power interruption when the transfer occurs. Usually about the same time as the safety demo on pushback, and taxiing into the gate on arrival.

 

[Melburnian1]

I posted in the Air NZ delays and cancellations thread about how NZ has had to withdraw an unspecified number of its 11 B789s due to turbine blade cracking problems with the Trent 1000 Rolls Royce engines that necessitated two turnbacks this week to AKL, one for NZ30 and one for NZ99.

Tomorrow (Friday 8 December) NZ61/NZ161/NZ162/NZ175 are anticipated to suffer delays of 90 to 455 minutes. The first is a SYD-bound flight; the other three are to or from PER.

One report:

ANZ Boeing 787-9 Dreamliner near Auckland on Dec 5th 2017, engine shut down in flight

QF has GE engines on its B789s so it must be unaffected.

I gather DY, NZ and TR are among airlines with Trent Rolls Royce engines for their B789s: there are two variants, the TEN being very new.

What other airlines have B789s with RR engines?

Will the NZ problems lead to recalls for urgent lengthy maintenance for B789s operated by other airlines?

From memory NH also had a problem at some stage.

 

[Gold Member]

A couple of days ago I was rolling into MEL aboard a Sri Lankan Airlines A330. After lining up with the gate the captain turned off both engines and rolled the aircraft in using its momentum while gently braking approaching the final stop marker.

I’ve never experienced this before. All flights have left engines at idle or have powered up a little as we approach the stop marker for each aircraft type and apply brakes far more aggressively at that point.

I can’t imagine shutting down the engines 50 meters before reaching the gate is a wise move based on what I assume is the Captain’s gut instinct of momentum and distance to travel. What if you you don’t make it to the gate and need to restart them. Possible but certainly not common practice or even SOP? Maybe even a little embarrassing.

 

[jb747]

A couple of days ago I was rolling into MEL aboard a Sri Lankan Airlines A330. After lining up with the gate the captain turned off both engines and rolled the aircraft in using its momentum while gently braking approaching the final stop marker.

Did he really? If so it would be one of the most stupid things I've ever heard of, and CASA would be most interested.

How do you know the engines were shut down? Did the aircraft stop prior to the gate?

Lack of engines would affect hydraulics, and take away the reverse thrust option. And the first item in the Airbus 'Loss of Braking' checklist is 'reverse - max'.

Melbourne has a requirement that more than idle thrust cannot be used after lined up with the gate, and that if the aircraft stops, that it must subsequently be towed to the gate. Break away power cannot be used.

 

[jb747]

I posted in the Air NZ delays and cancellations thread about how NZ has had to withdraw an unspecified number of its 11 B789s due to turbine blade cracking problems with the Trent 1000 Rolls Royce engines that necessitated two turnbacks this week to AKL, one for NZ30 and one for NZ99.

Tomorrow (Friday 8 December) NZ61/NZ161/NZ162/NZ175 are anticipated to suffer delays of 90 to 455 minutes. The first is a SYD-bound flight; the other three are to or from PER.

One report:

ANZ Boeing 787-9 Dreamliner near Auckland on Dec 5th 2017, engine shut down in flight

QF has GE engines on its B789s so it must be unaffected.

I gather DY, NZ and TR are among airlines with Trent Rolls Royce engines for their B789s: there are two variants, the TEN being very new.

What other airlines have B789s with RR engines?

Will the NZ problems lead to recalls for urgent lengthy maintenance for B789s operated by other airlines?

From memory NH also had a problem at some stage.

Seriously...if I could answer any of those questions I could make a fortune on the stock market.

 

[Gold Member]

Did he really? If so it would be one of the most stupid things I've ever heard of, and CASA would be most interested.

How do you know the engines were shut down? Did the aircraft stop prior to the gate?.

99% certain engines were off. There was a deftly silence in the cabin - having taken over 1000 flights in my life you can tell when engines are idling or completely shut down. Did not hear or notice APU switchover although that may have been done earlier shortly after touchdown when taxiing. When the aircraft had come to a complete stop there was no usual engine wind down sounds.

The aircraft stopped perfectly on the marks (I assume) as the airbridges were all aligned correctly. The Captain just rolled it in using the aircraft momentum and feathered the brakes as we got closer to the marks.

I’m not hear to dob anyone in, but the ground staff must have noticed it as well, even with all their protective earphones. Surely they would have reported it?

 

[Quickstatus]

Aviators - can you please summarise what the 4 hydraulic systems on the 747 operate.

#1 hydraulic system failed on a recent BA747-400 LHR-YVR due to hydraulic leak at #1 engine pylon. Aircraft arrived successfully. So trailing edge flaps and landing gear, nose steering and presumably brakes were operational. (info via AVherald)
British Airways (BA) #85 ✈ 29-Nov-2017 ✈ LHR / EGLL - CYVR ✈ FlightAware

 

[jb747]

Aviators - can you please summarise what the 4 hydraulic systems on the 747 operate.

#1 hydraulic system failed on a recent BA747-400 LHR-YVR due to hydraulic leak at #1 engine pylon. Aircraft arrived successfully. So trailing edge flaps and landing gear, nose steering and presumably brakes were operational. (info via AVherald)
British Airways (BA) #85 ✈ 29-Nov-2017 ✈ LHR / EGLL - CYVR ✈ FlightAware

The systems are split up, so that there is redundancy with any single failure, and even with some multiple failures. For the slats and flaps there's two types of control too. Flaps have hydraulic and electric, and slats have electric and pneumatic.

From the flight manual....

1. Systems 1 and 4 power the trailing edge flaps, landing gear, normal brakes (SYS 4), alternate brakes (SYS 1), and steering. Systems 1 and 4 also provide redundant power to the primary flight controls.
   
   Systems 2 and 3 power the primary flight controls, stabiliser trim, and elevator feel. System 2 also powers the alternate brakes and lower yaw damper. System 3 powers the upper yaw damper.
   
   Systems 1, 2, and 3 power the related centre, right, and left autopilot servos. Systems 2, 3, and 4 power the spoilers.
   
   
   

 

[jb747]

99% certain engines were off. There was a deftly silence in the cabin - having taken over 1000 flights in my life you can tell when engines are idling or completely shut down. Did not hear or notice APU switchover although that may have been done earlier shortly after touchdown when taxiing. When the aircraft had come to a complete stop there was no usual engine wind down sounds.

The aircraft stopped perfectly on the marks (I assume) as the airbridges were all aligned correctly. The Captain just rolled it in using the aircraft momentum and feathered the brakes as we got closer to the marks.

I’m not hear to dob anyone in, but the ground staff must have noticed it as well, even with all their protective earphones. Surely they would have reported it?

Whilst I'm sure it may have seemed that way to you, I'll bet it falls within that 1%.

 

[Gold Member]

Whilst I'm sure it may have seemed that way to you, I'll bet it falls within that 1%.

lol, thanks for your vote of confidence JB

 

[ChrisGibbs]

Was on QF162 WLG-SYD (VH-VZP Oz registered 737-8xx) this morning 9/12. The cabin crew were a mix of QF mainline and QF Jetconnect while the tech crew were QF Jetconnect. The aircraft that service the SYD-WLG-SYD sector are typically QF Jetconnect (ZK registered). Sometimes they are replaced by QF mainline aircraft including Tech and Cabin crew when a QF Jetconnect aircraft goes U/S. As departure time approached the CSM made a PA saying we are just about ready to go however given the aircraft we were flying on was an Australian registered aircraft the pilots had to familiarise themselves with the coughpit and our departure would be delayed by a couple of minutes. A couple of questions:

- Would the coughpit layout of a QF mainline 737-8xx differ that much from a QF Jetconnect 737-8xx? If so would it require additional time for familiarisation
- Can / do QF mix and match tech crew across the mainline and Jetconnect sectors?

Having travelled for more than a few years now across various airlines I thought this was one of the more interesting PA's to be made by a CSM to explain a slight delay in departure.

 

[ChrisGibbs]

Was on QF162 WLG-SYD (VH-VZP Oz registered 737-8xx) this morning 9/12. The cabin crew were a mix of QF mainline and QF Jetconnect while the tech crew were QF Jetconnect. The aircraft that service the SYD-WLG-SYD sector are typically QF Jetconnect (ZK registered). Sometimes they are replaced by QF mainline aircraft including Tech and Cabin crew when a QF Jetconnect aircraft goes U/S. As departure time approached the CSM made a PA saying we are just about ready to go however given the aircraft we were flying on was an Australian registered aircraft the pilots had to familiarise themselves with the coughpit and our departure would be delayed by a couple of minutes. A couple of questions:

- Would the coughpit layout of a QF mainline 737-8xx differ that much from a QF Jetconnect 737-8xx? If so would it require additional time for familiarisation
- Can / do QF mix and match tech crew across the mainline and Jetconnect sectors.

Just saw this posted this afternoon

Qantas pilots fume over move to fly Australian planes with Kiwi crew

Interesting quote "Jetconnect pilots will have to undergo a short conversion course before they can fly the Australian-registered 737s".

 

[jb747]

- Would the coughpit layout of a QF mainline 737-8xx differ that much from a QF Jetconnect 737-8xx? If so would it require additional time for familiarisation

I wouldn't have expected any difference at all. They were not ordered by Jetconnect.

- Can / do QF mix and match tech crew across the mainline and Jetconnect sectors?

No.

 

[ChrisGibbs]

Anyway, it's probably the second last time it will affect me.

Some years back I remember there were a bunch of ex QFi guys that retired from flying internationally at the mandatory age and jumped across onto the 737's and flew in the LHS domestically for a few more years. In the US I also read there were some international Captains who, for various reasons, needed to continue flying and elected to become FO's. Is this still an option?

Many years back I ran into a recently retired QF747 Captain (L. Williams) on the old QF5 Singapore - Frankfurt sector and he said when he retired he simply walked away and never looked back. With your combined RAN and QF background it must be a tough thing to simply walk away after 45+ yrs (at a guess) of aviation experience. How does an industry like aviation maintain the skills and IP you've developed over the years and allow it to be utilised for the future?

 

[ayebee]

greatly appreciate this thread ...

I noted the Air France A380, that had the uncontained engine failure and diverted to Goose Bay Canada in September, flew back to Paris after a replacement engine was fitted. The AF CEO was reported as saying the cause of the GP7200 engine failure, which was the first of its kind, had not been determined.
I recall after the QF32 RR failure aircraft were grounded for some time.
I imagine other GP7200 engines have been closely inspected, but is it a concern they continue flying when no one knows why this one failed?

 

[jb747]

Some years back I remember there were a bunch of ex QFi guys that retired from flying internationally at the mandatory age and jumped across onto the 737's and flew in the LHS domestically for a few more years. In the US I also read there were some international Captains who, for various reasons, needed to continue flying and elected to become FO's. Is this still an option?

It was an option for a while, but the Americans/ICAO changed the rules again.... A couple of people who hit 65 moved from the left to the right seat, but now you can't fly internationally, in any position, after your 65th birthday. But, you can continue to fly domestically within Oz, and some people elect to do that. As a generalisation, the number is inversely proportional to the number of times you've been married.

Many years back I ran into a recently retired QF747 Captain (L. Williams) on the old QF5 Singapore - Frankfurt sector and he said when he retired he simply walked away and never looked back. With your combined RAN and QF background it must be a tough thing to simply walk away after 45+ yrs (at a guess) of aviation experience. How does an industry like aviation maintain the skills and IP you've developed over the years and allow it to be utilised for the future?

Ah, Lyn...delightful bloke to fly with. Walking away is my intention too. This sort of blog will be as close as I get, as I have no intention of having any further involvement with CASA.

Right behind me are a bunch of Captains and FOs who have a vast wealth of their own experience. They don't need me. I'll just comment from the sidelines when they get it wrong. And like a good wine, as the years go by, I'll get better. Or not.