Ask The Pilot

[petercr]

Going by the timeline of episodes (last week's one featured the 2012 Melbourne Cup being delivered via Emirates), I'd say it was filmed about this time last year so I thought it would be safe to assume that it'd be finished by now...

Having seen other shows about building developments in Dubai, they must have got the 'rest of the team' working on the terminal then. Was interesting to see what they had to do esp with tonight's episode also featuring how they changed gate numbers over from numeric to alpha-numeric in one 8-hour period.

 

[RobYg]

I'm not sure if this has been answered, JB747, but what is the fuel consumption of an A380 on climb, cruise and flight idle? Once again, thank you for your informative and expert answers.

 

[jb747]

When does the runway work start at DXB or is it under way.

Has that had an impact on schedules or just general delays?

I've been a bit out of the loop lately, but the time frame I heard was around March/April. Apparently they want about half of all of the traffic to just go away, which given it's Emirates home is probably a bit of an issue for them. All freight and many commercial flights being pushed to another airfield about 50nm away. I've not heard what the effect on QF will be. I know they wanted to keep both flights through there whilst the work is in progress, but it's not impossible that they might go via another route for the period.

 

[jb747]

Was interesting to see what they had to do esp with tonight's episode also featuring how they changed gate numbers over from numeric to alpha-numeric in one 8-hour period.

+

The gate numbers on the outside (i.e. that the pilots use) and the inside (the passengers) are different.....

 

[anat0l]

I've not heard what the effect on QF will be. I know they wanted to keep both flights through there whilst the work is in progress, but it's not impossible that they might go via another route for the period.

I think it'll send people around the bend if they go back to via SIN even for a while......

 

[docjames]

I think it'll send people around the bend if they go back to via SIN even for a while......

Would via AUH be an option to still allow connections? Allows ground connection to DXB (~ 1hr via bus).

 

[petercr]

+

The gate numbers on the outside (i.e. that the pilots use) and the inside (the passengers) are different.....

Recipe for confusion there... Hey Fred, there's a 738 parked in my spot... nah it's okay Dave, just call the tower and get them to get it towed and impounded...

 

[jb747]

I'm not sure if this has been answered, JB747, but what is the fuel consumption of an A380 on climb, cruise and flight idle? Once again, thank you for your informative and expert answers.

Like so many things in aviation, there is no one answer to your question. The fuel flow figures will vary dramatically with temperature, altitude and weight.

In the case of cruise, starting at max weight, the flow will be in the order of 4,000 kgs per engine, per hour. That will reduce to about 2,800 kgs/hr by top of descent.

Climbing, the fuel flow will progressively reduce. It will start at about 8,000 kg/hr (per engine), and end at very slightly above the cruise figure (say about 4,200 kgs/hr).

Idle...about 400 kgs/hr up high, down to about 800 kgs/hr.

 

[mjt57]

JB, just a quick one. When not actually flying or in the airport preparing for a trip, do you have a workplace that you can go to for work stuff, or do you work from home? ie. work emails, etc.?

 

[MichaelD]

JB,

I am trying to get my head around the effects of wind on take-off and landing in terms of which directions are optimal.

For a North-South runway:

If there is a very strong northerly wind (i.e. a wind blowing from the North to the South);
- would take-off be towards the north or towards the south?
- would landing be approached from the north or from the south?
and why?

Thank you very much for your reply.

 

[jb747]

JB, just a quick one. When not actually flying or in the airport preparing for a trip, do you have a workplace that you can go to for work stuff, or do you work from home? ie. work emails, etc.?

Basically we work from home. Other that the simulator, it can be very many months between visits to the 'office', and even then they tend to be more social than anything else.

 

[jb747]

JB,

I am trying to get my head around the effects of wind on take-off and landing in terms of which directions are optimal.

For a North-South runway:

If there is a very strong northerly wind (i.e. a wind blowing from the North to the South);
- would take-off be towards the north or towards the south?
- would landing be approached from the north or from the south?
and why?

A couple of 'speeds' to learn about first.

Basically, airspeed is the speed of the aircraft through the air mass. It's what you would feel if you stuck your hand out the window. Airspeed is what makes an aircraft fly.

Ground speed is the speed of the aircraft over the ground. It is the result of airspeed plus or minus the wind component.

If my take off speed is going to be 150 knot AIRSPEED, as I line up on a runway with a 30 knot northerly wind blowing I would line up pointing to the north. Sitting on the runway, at ZERO knots of groundspeed, I would already have 30 knots of airspeed because of the wind. I would need to accelerate the aircraft by 120 knots to achieve my lift off speed.

But, if I'd lined up pointed downwind, then sitting on the runway, I'd have -30 knots of airspeed, and would need to accelerate the aircraft by 180 knots to achieve that target lift off speed. I would need to add much more energy, and it would require a lot more time and runway to take off downwind.

Landing is the same thing. Landing into a headwind, the wind speed is subtracted from the airspeed to give you a groundspeed. Once you touch down, the groundspeed is what the brakes have to get rid off.

If your approach speed was 135 knots, and you had that same 30 knot wind...the brakes would need to get rid of over 200% more energy if you landed with the downwind component.

So, within quite narrow limits, you always take off and land pointed INTO the wind.

 

[Dmac6345]

Hi JB,
Speaking of the wind, does the A380 move around more with the wind, than say a 738 or 763. I know they are so much bigger, but having much more surface I would have though they move around more, even without the passengers noticing. Having flown in most of the different QF aircraft, they all feel different, but you can certainly feel the bumps more in smaller stuff Cheers

 

[jb747]

Hi JB,
Speaking of the wind, does the A380 move around more with the wind, than say a 738 or 763. I know they are so much bigger, but having much more surface I would have though they move around more, even without the passengers noticing. Having flown in most of the different QF aircraft, they all feel different, but you can certainly feel the bumps more in smaller stuff Cheers

A big factor in how an aircraft responds to wind gusts is its wing loading. Basically this is a measure of how much weight each square foot of wing is being asked to carry. Airbus generally have substantially lower loadings than the equivalent Boeing (747/767). The upshot is that the Airbus tend to move around more in response to the wind. This effect is somewhat masked by the FBW. Overall, the 767 is the best aircraft that I've flown for handling gusty conditions.

 

[Dmac6345]

I totally agree with the 767. I think one of the worst is the A330. For some reason it just feels like it is constantly moving and not very forgiving. Travelling b/w MEL-SIN regularly, I somtimes get off feeling very average. Never used to happen on the A380.

 

[Moody]

A big factor in how an aircraft responds to wind gusts is its wing loading. Basically this is a measure of how much weight each square foot of wing is being asked to carry. Airbus generally have substantially lower loadings than the equivalent Boeing (747/767). The upshot is that the Airbus tend to move around more in response to the wind. This effect is somewhat masked by the FBW. Overall, the 767 is the best aircraft that I've flown for handling gusty conditions.

Speaking of wind ... I was on a Melbourne to Sydney flight on Thursday and we were initially told that we would be using the E/W runway due to high winds. But as we started our approach the captain said that conditions had eased on we would be using the third runway as normal.

It was not a normal landing!

A fair bit of buffeting and throttle work was to be expected and we passed over the threshold a little higher and faster than usual (IMHO) but nothing concerning to me at the time. The final 10-15 seconds getting the aircraft on the deck was the sphincter clenching bit. In particular the left wing dipped sharply downwards to the point where I thought the tip would touchdown before the landing gear. The plane then righted itself and we got the left and then right wheels on the deck, and then there were some pretty extreme rudder inputs as if we were driving through a chicane.

I have had some pretty interesting landings and the usual reaction of the pax afterwards is to have a chuckle with each other to prove we were never really worried. On this occasion there were a few glances but nobody said a word.

So the question I have is ..... is there a point at which aborting a cross-wind landing is as dangerous as persevering?

 

[mjt57]

Basically we work from home. Other that the simulator, it can be very many months between visits to the 'office', and even then they tend to be more social than anything else.

Is "the office" in Sydney or Melbourne for you? If SYD it's a fair hike just to go in for a social visit isn't it?

When you were doing your conversion to the 380 was this in a classroom or from home for the theory side of things?

 

[D747]

Hi jb, does Airbus fly by wire compensate for thrust inputs in relation to pitch? Also, does it compensate for pitch in a turn?

 

[jb747]

Is "the office" in Sydney or Melbourne for you? If SYD it's a fair hike just to go in for a social visit isn't it?

When you were doing your conversion to the 380 was this in a classroom or from home for the theory side of things?

Because I'm based in Sydney (though I now live in country Victoria), the 'office' is in Sydney. I'm certainly not going all that way just to say hello, but it's easy enough to stick one's head through the fleet manager's door when up there for a simulator or some classroom days.

The conversion onto the 380 consisted of roughly a month of classroom, the same again in the sim, and then two to three months of line training. One week of the initial classroom could be done at home as you worked through the software, but the rest was traditional classroom...albeit with only a couple of students.

 

[jb747]

Hi jb, does Airbus fly by wire compensate for thrust inputs in relation to pitch? Also, does it compensate for pitch in a turn?

The behaviour of the flight controls varies with the law, and there can be minor variations with stage of flight. In normal law, to turn the aircraft (up to 30º angle of bank), you just roll to the bank angle you want. The FBW will then hold the attitude. If autothrust is engaged, it will ensure (up to the power limits) that the speed is maintained. At very small bank angles, (<2º, it rolls back to wings level)....this can be very annoying behaviour when on finals.

The very strong engine pitch couple of (say) the 767 meant that any time you moved the thrust levers, there had to be an immediate adjustment in pitch as well. The Airbus FBW damps that out entirely. You have to keep the engines in mind, as the cues to autothrust behaviour are removed by the system. (Actually this seems to be an Airbus trait...they seem to hate cues, and do their best to remove them.) The best example of this is a manually flown go around. In a 767 or 747, you'd push the power to TO/GA, and the aircraft would pitch up very strongly. There was virtually no back stick required, and you actually had to push and trim to stop the pitch up at the desired attitude. In the AB, there is no pitch couple whatsoever, so you push to TO/GA, and the aircraft continues DOWN until you remember to pull up to the required pitch target. Obviously something you learn pretty quickly, but it's different to every non FBW aircraft that I've ever flown.