Ask The Pilot

[WheelieBagWanderer]

Coming back from HKG on CX a few weeks back we were held at the gate in HKG for about 40 minutes after scheduled departure time.

During the delay the captain announced that "we've been advised by Sydney Air Traffic Control to hold here for a little while, as due to favourable winds we would arrive in Sydney a lot of time prior to the end of the overnight curfew."

I had 2 thoughts on this:
1. Would SYD ATC *really* have advised the flight when they're sitting on the ground in HKG? If so, how? Via the datalink in the flightdeck?
2. If SYD advises an aircraft in HKG (or any destination for that matter) to "hold", doesn't that have an effect of missing the departure slot at the airport of origin?

Finally, on the topic of wearing shoes during take-off and landing, I noticed on a couple of flights with SQ that during the pre-take off cabin check that the SQ crew have asked passengers who have removed their shoes to please put them on again until "after take off", so I assume it must be company policy at that airline.
Others don't seem to mind - EK springs to mind.

Thanks again for great answers to all our (in my case most probably, inane) questions! Appreciated.

 

[jb747]

What is the standard scale of the cost index (eg 0 - 100), is there a cost index which is typically used? Do the cost index numbers mean the same between different types (eg would the cost index of say 50 mean the same thing on a B747 an A380 and a B767).

They seem to be numbers that are just plucked out of the sky. 747 we used 100, but the speed that gave you varied over the years as the cost of fuel changed. I don't recall how high it went. 380 we use either 60 or 130.

I'm not a big fan of using them (higher numbers) when you want to go faster. A fixed mach number works as well, and perhaps better.

 

[markis10]

FWIW aircraft have had the ability to contact any ATC unit for a long time, in the 80s I asked a Northwest captain to let Bankstown tower know I would not be on shift next day because I had got on the wrong plane. He simply touched base with Northwest Ops via HF who then sent Bankstown a message via a system known as the AFTN, essentially a telex network, these days ACARS does the job.

 

[jb747]

Coming back from HKG on CX a few weeks back we were held at the gate in HKG for about 40 minutes after scheduled departure time.

During the delay the captain announced that "we've been advised by Sydney Air Traffic Control to hold here for a little while, as due to favourable winds we would arrive in Sydney a lot of time prior to the end of the overnight curfew."

I had 2 thoughts on this:
1. Would SYD ATC *really* have advised the flight when they're sitting on the ground in HKG? If so, how? Via the datalink in the flightdeck?
2. If SYD advises an aircraft in HKG (or any destination for that matter) to "hold", doesn't that have an effect of missing the departure slot at the airport of origin?

Unlikely that Sydney said anything. The curfew time is known to the crew and Cathay ops, and I expect the decision to delay was from them.

Many places don't have departure slots. If you miss your slot, then that's how it is. You go when you can...

Finally, on the topic of wearing shoes during take-off and landing, I noticed on a couple of flights with SQ that during the pre-take off cabin check that the SQ crew have asked passengers who have removed their shoes to please put them on again until "after take off", so I assume it must be company policy at that airline.
Others don't seem to mind - EK springs to mind.

Well, I guess SQ have had some experience of exactly the sort of issue that we were talking about. It's a good idea.

 

[jb747]

FWIW aircraft have had the ability to contact any ATC unit for a long time, in the 80s I asked a Northwest captain to let Bankstown tower know I would not be on shift next day because I had got on the wrong plane. He simply touched base with Northwest Ops via HF who then sent Bankstown a message via a system known as the AFTN, essentially a telex network, these days ACARS does the job.

Satphone works too. I can directly call many of the ATC agencies that we deal with. Sometimes it can be better to have a discussion on the phone rather than the radio. And a phone patch can always be had via the IOC in Sydney.

 

[WheelieBagWanderer]

Well, I guess SQ have had some experience of exactly the sort of issue that we were talking about. It's a good idea.

Maybe the "experience" is from their incident at Taipei some years back?
Then again it could have been company policy for a long time. As you say, seems sensible.

I just remember one thing I was interested in asking you, JB....
Has there been any talk around the QF traps about this documentary which I see Channel 9 have started advertising tonight as "Coming Soon".
QF32 ??

http://channelnine.ninemsn.com.au/article.aspx?id=8761507

It will be interesting to see how they portray this, but the cynical side of me thinks it will be easy to guess.

Thanks to you and Markis10 for your quick replies on the ATC question.

(Edited - Sorry.. link didn't copy!)

 

[jb747]

Has there been any talk around the QF traps about this documentary which I see Channel 9 have started advertising tonight as "Coming Soon".
QF32

It will be interesting to see how they portray this, but the cynical side of me thinks it will be easy to guess.

Thanks to you and Markis10 for your quick replies on the ATC question.

Your cynical side is probably correct.

 

[legroom]

... Well, I guess SQ have had some experience of exactly the sort of issue that we were talking about. It's a good idea.

May be judged off topic but here it goes.

SQ would not give out slippers until after take-off, but they did give me the PJ then.

When I queried, the FA said something like "it is for your safety".

That was in F.

 

[JohnPhelan]

May be judged off topic but here it goes.

SQ would not give out slippers until after take-off, but they did give me the PJ then.

When I queried, the FA said something like "it is for your safety".

That was in F.

Agree absolutely. All airlines should ensure that pax keep their shoes on during take off and landing (difficult to totally enforce, I know). If you have to evacuate the aircraft in an emergency - especially one involving fire or fuel - you want to be wearing shoes! (Yes, yes, no high-heeled women's shoes on the evacuation slides, I know).

Which brings up the "Singapore girls" in their sandals - totally inappropriate from a safety perspective, I've always thought ......

 

[casanovawa]

They probably keep the runners in a locker/closet somewhere, don't want to seem over prepared to the passeners in the cabin...

 

[jb747]

Zipping through DXB the other week I noticed that a number of the EK planes on stand had their speed brakes and/or ailerons (upper wing control surfaces - not sure which ones) sticking up. Is this normal? I was of the impression that all airlines (?) returned these control surfaces to their home position during the taxi to the gate.

Further to this one... I had a chat with an engineer in Dubai the other day. Apparently on the early A380s, there is a bug in the software that causes the spoilers to rise slightly if both hydraulics systems are depressurised. Apparently only on the ground, and not to a great extent.

 

[moa999]

Does Airbus (corrected) not upgrade the software on aircraft?? Or just some stuff.

I would have thought it was dangerous to have lots of different versions floating around

 

[Robbi]

Does Boeing not upgrade the software on aircraft??

A380 is Airbus...and apparently not

 

[defurax]

Packs can be turned off entirely (not a top idea when it's over 40º) or run from the APU until after take off. The combination of the two might get you another 15 tonnes depending upon the actual conditions.

Hi JB,

Thanks for your detailed answer the other day. So in the end it was quite an interesting experience, QF93 was scheduled to leave at 11:20 AM but we were delayed 2 hours. The Captain gave us a very detailed explanation of what had caused the delay. So the aircraft was towed to the gate and while baking under the sun at an ambient temperature of 45 celsius the APU apparently failed (which I think is a relatively common occurrence on very hot days). Just before boarding was about to begin, the cabin temperature had reached the mid-40s and the Captain decided to send the cabin crew in the terminal, close the door and start one of the engine (packs?) for 40 min to try and cool the cabin. We were then allowed to board and we could feel the temperature quickly rising once inside the plane...the Captain had to start an engine at the gate again to keep us cool and we finally made it to the runway and once we reached 20,000 feet the cabin temperature was perfect

My question is: 1- Are APUs limited in their design so that there will always be problems at 45 celsius ( I am not an engineer...)
2- Do Emirates have a lot of problems in DXB with overheating planes parked at the gate?

 

[harvyk]

Does Airbus (corrected) not upgrade the software on aircraft?? Or just some stuff.

I would have thought it was dangerous to have lots of different versions floating around

Whilst not a pilot, I am a software engineer who has also written software to control hardware devices (firmware)... It's in no way dangerous having different equipment running on different versions. The basic protocols between the various devices would have been devised in the very beginning of the design process (assuming that they are not using standard protocols) and are unlikely to have changed much since. As such when a piece of firmware is updated to a newer version, chances are it is only processing internal to that device which would be changed.

Where a dependency exists between two different devices, they would have defined testing procedures to ensure that an update in one device does not cause a problem downstream, and if it does then either the update will be fixed to mitigate the issue, or the downstream device will have it's own software update developed.

So to follow on from JB's point about a bug in the A380 software, chances are it was a bug within a couple of methods (think program functions) which was causing that problem. They could have either put in a workaround (eg no hyd = automatic resting state, regardless of other inputs) or found the line of code which was causing the issue itself (sometimes very difficult to do and can cause unintended side effects).

 

[jb747]

Does Airbus (corrected) not upgrade the software on aircraft?? Or just some stuff.

I would have thought it was dangerous to have lots of different versions floating around

The software is updated, but not all the aircraft are exactly the same hardware, so not all can accept exactly the same software package. Basically, I doubt if two aircraft are ever exactly the same...it's not quite like making a Toyota.

 

[jb747]

1- Are APUs limited in their design so that there will always be problems at 45 celsius ( I am not an engineer...)

I think it's a trade off. We very rarely need the sort of bleed that is demanded on those 45º days, so I expect the APUs are designed to handle the loads of 95% of the days (and of course many airports have decent ground air facilities).

Do Emirates have a lot of problems in DXB with overheating planes parked at the gate?

There is very good conditioned air from the terminal in Dubai, so the APUs can be shut down. But, there is still a problem with the APU bleed ducts overheating on the hottest days there. That's a problem for Airbus to resolve, but it means we have to be careful about how long we run the APU bleed for. That means conditioned terminal air for a long as possible, and if using the APU for take off, only turn its bleed on just before you need it.

Temperature management as you describe is something that doesn't come up often, but which I've had to do occasionally in every type.

 

[harvyk]

The software is updated, but not all the aircraft are exactly the same hardware, so not all can accept exactly the same software package. Basically, I doubt if two aircraft are ever exactly the same...it's not quite like making a Toyota.

Come to think of it I was under the impression that most airlines purchased their own avionics equipment or at least had a bit of a choice.
If that's the case then the basic protocols which I referred to earlier would be even more important since the data along the cable connecting everything would need to follow a standard agreed to by all manufacturers.

 

[markis10]

All this talk of software makes me wonder how you reboot an A380, and where do they hide the any key?

 

[petercr]

Maybe they use an old AT-style key switch... (Scene: in the A388 coughpit... Hey JB, I just accidentally turned the key past ON to RESET... how long is this thing going to take to reboot)