Ask The Pilot

[jb747]

While waiting to depart I was tracking the QF682 service from ADL-MEL. From the looks of things it was over a 3hr sector for them with what looked to be a couple of missed approaches onto RWY16. When planning an ADL-MEL sector would you typically take on that much fuel for that much holding?

As there were thunderstorms on the forecast, for 5 minutes after his planned arrival time, his minimum fuel would have had to include at least an hour's holding. Knowing the Captain concerned, I expect he'd have a bit more than that.

 

[jb747]

I see old de Crespigny has released a new book.
You going to grace our book shelves soon JB747 ?

It went bang.

We descended.

We landed.

Done.

 

[tuppaware]

Almost poetic !

 

[Kerrodt]

It went bang.

We descended.

We landed.

Done.

Can I get an autographed copy please JB?

 

[opusman]

It went bang.

We descended.

We landed.

Done.

6 more syllables and it's a haiku!

 

[ChrisGibbs]

As there were thunderstorms on the forecast, for 5 minutes after his planned arrival time, his minimum fuel would have had to include at least an hour's holding. Knowing the Captain concerned, I expect he'd have a bit more than that.

You are still able to see who is crewing particular flights?

While we were taxiing to queue for takeoff the Captain said the airport was closed due to thunderstorms. I understand all ground personnel clear the aprons and aircraft cannot be pushed back or taxied to the gate. Who makes the decision to close the airfield? Is there a rule that says lightning strikes were seen within X nm of the field and then we have to wait Y minutes from the last strike to re-open the airfield. Does the closing of the airfield prevent landings and takeoffs or just ground operations? I presume that even if the airfield is open the Captain has the final choice on whether to depart or not? If you get to the holding point and decide you're not going to depart due to weather do you then have to taxi off the runway and rejoin the queue at the end?

 

[jb747]

You are still able to see who is crewing particular flights?

No, not generally. This was a Facebook job....

While we were taxiing to queue for takeoff the Captain said the airport was closed due to thunderstorms. I understand all ground personnel clear the aprons and aircraft cannot be pushed back or taxied to the gate. Who makes the decision to close the airfield? Is there a rule that says lightning strikes were seen within X nm of the field and then we have to wait Y minutes from the last strike to re-open the airfield.

I don't know who, specifically, makes those decisions. They're company rules. The one I was familiar with was 5 nm.

Does the closing of the airfield prevent landings and takeoffs or just ground operations?

If they cease ground handling operations, that has no effect upon aircraft that are already off the gate and able to fend for themselves. They're just trying not to electrocute the guys loading your luggage, etc. Closure of the airfield to all ops by ATC (which I don't recall ever seeing), would be a different matter.

I presume that even if the airfield is open the Captain has the final choice on whether to depart or not? If you get to the holding point and decide you're not going to depart due to weather do you then have to taxi off the runway and rejoin the queue at the end?

I've seen that scenario a number of times over the years. Basically, I've taxied on to the runway, and then up the runway a bit , and then exited again far enough down the runway to be clear of the holding traffic. Once (in HK) I went back to the gate...I was not going flying that night. On another occasion, in Singapore, I held on a parallel taxiway, where I was joined by a number of other players, as we watched people who had made a different decision launch into the weather. Whilst those who flew all got away with it on those occasions, I was quite happy with my decision.

 

[cosi]

Once (in HK) I went back to the gate...I was not going flying that night

Sitting on board a CX flight in Aug 17, when 2 consecutive typhoons hit Hong Kong, CX Captain announced they would only take-off if they felt it was safe. They had no respect for the cowboys taking off. We sat near they take off runway for 3 hours waiting for the wind shear to pass.

 

[jb747]

Sitting on board a CX flight in Aug 17, when 2 consecutive typhoons hit Hong Kong, CX Captain announced they would only take-off if they felt it was safe. They had no respect for the cowboys taking off. We sat near they take off runway for 3 hours waiting for the wind shear to pass.

Are they cowboys, or airlines in which management have managed to assume control of all aspects of the flying? I expect they're the same airlines in which fuel loads are decided remotely.

 

[ChrisGibbs]

Was on the Monday 13 May QF1 SYD-SIN service. All passengers were on and the baggage compartments closed with the LL2 Door being the last one remaining open. Our scheduled departure time came and went with the Captain coming on PA and saying they were ready to go up the front and just had to wait for the automated fuel management system to finish transferring fuel to the horizontal stabilisers at the rear for the plane to ensure weight and balance was maintained. Once this was done we we would then get the final load sheet transmitted to the aircraft and we would be on our way. A question is this fuel transfer automated to the extent it kicks in without any manual intervention. Does the aircraft have to be stationary for weight and balance to be calculated?

Thanks in advance.

 

[jb747]

Was on the Monday 13 May QF1 SYD-SIN service. All passengers were on and the baggage compartments closed with the LL2 Door being the last one remaining open and the scheduled departure time had come and gone. The Captain came on PA and said the automated fuel management system had started to transfer fuel to the horizontal stabilisers at the rear for the plane to ensure weight and balance was maintained. Once this was done we got the final load sheet and were on our way. A question is this fuel transfer automated to the extent it kicks in without any manual intervention. Does the aircraft have to be stationary for weight and balance to be calculated?

Around the time that you start doing the coughpit preflight, you'll be sent a couple of numbers. One is the zero fuel weight, and the other, the zero fuel CoG. They are entered into an FMC, and will be used by the fuel system to calculate just where it will put the fuel. It then does that automatically.

In the last few minutes prior to push back, you'll get the final loadsheet. That will update those numbers, and will also give take off CoG and load control's calculation of the fuel distribution. We update those numbers in the FMC, and then enter TO setting, as well as check that the fuel figure what is actually in the trim tank. The FMC will have also calculated a TO setting, and that has to be within 1% of the figure on the final load sheet. If it isn't then you select the "auto fuel transfer" system. It's automatic in that once you turn it on, it will then move fuel until the two TO settings match. You can stop it once within 1%, but you'd almost always let it stop by itself, which it will do when the two match exactly.

All of this is done in the before start procedures, so you can't complete them, or the before start or after start checklists, until you've completed the loading entries.

Procedurally, it has to be done before push back. That closes a lot of the potential holes in the cheese. But, the system would work when you are taxiing, and you could enter the numbers into the FMC. Not a great idea though.

 

[Quickstatus]

Moving fuel to adjust various parameters relies on an empty space to move the fuel to. What if there isn’t any space to move the fuel?

 

[jb747]

Moving fuel to adjust various parameters relies on an empty space to move the fuel to. What if there isn’t any space to move the fuel?

It's called a trim tank. It's not something that you fill up. There are also tanks in the wings that are mostly empty on the ground, but which have fuel pumped to them airborne.

But, if the tail tank were full (or perhaps unusable), and you still needed to make a trim correction, then you'd either have to move/offlload the freight, luggage, or passengers.

 

[ChrisGibbs]

On the A380 I assume there are a bunch of tanks that are for trim / weight / balance purposes only and not useable for drawing fuel from to drive the engines and/or APU. What are the surge / vent tanks used for? Many years ago at the old BKK airport I was watching a 747-300 being refuelled. After a while I saw what looked to be fuel coming out of the wing tip at a rapid rate of knots. I'm guessing there are some jet aircraft that will distribute the fuel automatically as the aircraft is re-fuelled from the one point whereas other aircraft require the refuellers / pilots to determine how much fuel they should put it various tanks.

 

[jb747]

On the A380 I assume there are a bunch of tanks that are for trim / weight / balance purposes only and not useable for drawing fuel from to drive the engines and/or APU. What are the surge / vent tanks used for? Many years ago at the old BKK airport I was watching a 747-300 being refuelled. After a while I saw what looked to be fuel coming out of the wing tip at a rapid rate of knots. I'm guessing there are some jet aircraft that will distribute the fuel automatically as the aircraft is re-fuelled from the one point whereas other aircraft require the refuellers / pilots to determine how much fuel they should put it various tanks.

There are only four tanks that directly feed the engines in a 380 (or 747). These are called the mains. You can crossfeed fuel to the engines, but that's pressurised fuel from another of (the 4) main tanks. There are 6 more wing tanks...the main, the mid, and the outers (imaginatively named). And then there's the trim tank in the tail. Fuel management was normally automatic, but it could go awry, particularly in the case of some early diversions.

The fuel in the tail is moved, in about 2,000 kg allotments, to keep the CofG at the most efficient point, for as long as possible. Basically that means that weight is pushing the tail down, not aerodynamic forces. As the fuel in the wings is burnt, the system eventually transfers fuel forward, sharing it across the tanks that are in use.

Surge tanks aren't part of the pilots concern...as the fuel within is not measured. Basically, in many cases the fuel is cool when loaded, having been underground for some time. It arrives in the tanks, and starts to expand. It has to go somewhere, so you either vent it (bad) or capture it and allow it back into the main fuel system when there is space.

What you saw should not happen though...so I expect you were simply being overfilled...also bad.

 

[odysseus]

On the A380 I assume there are a bunch of tanks that are for trim / weight / balance purposes only and not useable for drawing fuel from to drive the engines and/or APU. What are the surge / vent tanks used for? Many years ago at the old BKK airport I was watching a 747-300 being refuelled. After a while I saw what looked to be fuel coming out of the wing tip at a rapid rate of knots. I'm guessing there are some jet aircraft that will distribute the fuel automatically as the aircraft is re-fuelled from the one point whereas other aircraft require the refuellers / pilots to determine how much fuel they should put it various tanks.

On that note, only around 2 years back at Sydney, I saw the same thing of fuel coming out the wing on a domestic craft while waiting to board at another gate. I don't recall seeing the refuelling vehicle, though it was certainly alarming to see at the time, whatever the cause.

 

[AviatorInsight]

Also known as a NACA (the predecessor to NASA) duct. They're a similar shape to the air conditioning packs and allow air to flow in creating a positive pressure in flight.

 

[Quickstatus]

AC and DC busbars on an aircraft

AC is initially generated by spinning genies in engines, APU, RAT, Emergency Gen on A330 (I think spun by hydraulics) but is this rectified to DC at the generator or at some common location?

 

[jb747]

AC and DC busbars on an aircraft

AC is initially generated by spinning genies in engines, APU, RAT, Emergency Gen on A330 (I think spun by hydraulics) but is this rectified to DC at the generator or at some common location?

I don’t think the generators directly produce DC, but there are various transformer/rectifiers throughout the system. I’ll have a look at a manual when I get home in a day or two.

The A330 emergency generator produces power from a small propellor dropped into the airstream. Not sure where it is...on the A380, it’s under the port wing.

Some aircraft can also produce power from what are called HMGs....generators within the hydraulic system.

 

[Moody]

Harking back to an off-hand comment about the attitude of some US air traffic controllers, do any SIMs include a degradation or complete loss of ATC comms into a busy airport?