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777GE90
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How Can The A380 Climb So High Initially?

Fri Apr 22, 2016 9:26 pm

I noticed newer gen aircraft like the A380 / 787 seem to always have really high initial climb altitudes, for example I usually see EK A380's climb straight to FL400 from DXB to LHR, when you compare that with a 77W with powerful GE90's on the same route, it seems to climb to much lower initial altitudes and then step climb up as it burns more fuel and gets lighter.

This confuses me as I would expect a 777 with massive GE90's to be able to outperform a super heavy A380 in the air, especially since the 777 is very capable at climbing rapidly, so what gives, how come the newer gen aircraft like the A380 are able to climb so much higher initially? Is it a software limitation on older aircraft?
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RE: How Can The A380 Climb So High Initially?

Fri Apr 22, 2016 9:31 pm

Two words : Wing loading
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RE: How Can The A380 Climb So High Initially?

Fri Apr 22, 2016 9:33 pm

it comes down to those monster sets of wings on the 380.
IIRC , they were designed with the -900 stretch model in mind.

I've watched several 380's launch from DFW to Sydney and Dubai
and while they may climb like homesick angels once airborne,, they need ALOT
of runway to get airborne at max loads.
 
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Stitch
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RE: How Can The A380 Climb So High Initially?

Fri Apr 22, 2016 9:34 pm

Quoting 777GE90 (Thread starter):
When you compare that with a 77W with powerful GE90's on the same route, it seems to climb to much lower initial altitudes and then step climb up as it burns more fuel and gets lighter.

The 777-300ER has relatively high wing loading so it cannot climb to the highest flight levels until it's burned off fuel and lightened it's weight.
 
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RE: How Can The A380 Climb So High Initially?

Fri Apr 22, 2016 10:08 pm

Quoting 777GE90 (Thread starter):

I asked the same thing a few days ago in Tech/Ops.

Quote:
The 77W makes do with the wing of its lighter siblings, with only small extensions added at the tips. It is a wing-limited airplane, where the smaller versions are power-limited.

Whereas it is not unusual to see lighter -200 and even -300 loiter around FL400, the heavier -300ER usually never really goes much past FL 360-380, and only when light.

At or near MTOW, you can even find them at an initial cruise altitude of 280 or 290...

The good thing is that whatever altitude it has to climb to, it gets there in no time thanks to those massively powerful engines.
 
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RE: How Can The A380 Climb So High Initially?

Fri Apr 22, 2016 10:20 pm

This is why the 778-779 will not need as much power as the 77W-it will have a significantly larger wing. It still will not approach the performance of the A380, though, whose wing is oversize by most standards. As Sooner787 pointed out, the wings were designed for the A389, and hence are larger than needed for the A388.
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RE: How Can The A380 Climb So High Initially?

Fri Apr 22, 2016 11:29 pm

I'll never forget flying into Barcelona last year, we parked on the tarmac and deplaned via stairs into a bus. Just as I was walking down the stairs, an Emirates A380 was rotating in front of me. There was a strong headwind, and being so big it always looks like it's moving slower than it really is, but the way it leapt into the air so eagerly was really awesome.
 
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RE: How Can The A380 Climb So High Initially?

Sat Apr 23, 2016 2:41 am

I often get EK A380s climbing over my house for a ~4 hour flight to MEL and they're usually in a turn at about 2000 feet.

I'm always stunned at how much of the noise is from the airframe rather than engine noise.
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RE: How Can The A380 Climb So High Initially?

Sat Apr 23, 2016 4:36 am

When leaving SYD heading long to LAX, DFW or DXB, I've noticed a good steady climb, but initially only up to perhaps FL300 or FL320 with QF.

The plane generally only gets up to FL400/FL410 in the final section of the flight.

On shorter hops, we've gotten up to FL360 quite quickly, and up to FL410 soon after.
 
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RE: How Can The A380 Climb So High Initially?

Sat Apr 23, 2016 4:42 am

Not a lot of cargo loads mostly just people and bags, on a 5-6 hour sector also helps.
 
astuteman
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RE: How Can The A380 Climb So High Initially?

Sat Apr 23, 2016 5:50 am

Quoting Sooner787 (Reply 2):
I've watched several 380's launch from DFW to Sydney and Dubai
and while they may climb like homesick angels once airborne,, they need ALOT
of runway to get airborne at max loads.

That suggests the use of flexpower take-offs, as the last thing an A380 needs is A LOT of runway
Even an MTOW an A380 will use less runway than a fully loaded 777 or 747

Per their respective manufacturers ACAP documents

ISA 0ft + 15 deg C gives ..

A380 - 3 000m at 570t
777-300ER - 3 300m at 347t
747-8 - 3 300m at 445t

Rgds
 
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RE: How Can The A380 Climb So High Initially?

Sat Apr 23, 2016 6:51 am

Quoting Sooner787 (Reply 2):
it comes down to those monster sets of wings on the 380.
IIRC , they were designed with the -900 stretch model in mind.

  


Those big, bulky wings make the fuselage seem like an afterthought. Among the things that make the Whalejet among the most stubby, ungainly and inelegant aircraft ever IMHO...


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waly777
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RE: How Can The A380 Climb So High Initially?

Sat Apr 23, 2016 8:49 am

Quoting astuteman (Reply 10):

Unlikely any aircraft uses flex takeoff when close to or at MTOW which is likely the case for a DFW to SYD flight.

3000M is still a lot of runway, plus those lengths do not indicate the actual length required to rotate, it includes RTO stopping distance. I'd like to think most widebodies need a good bit of runway at MTOW except the 332 and 788 with higher thrust engines.

At the OP, it's definitely to do with wingloading and relatively lower takeoff weights on such sectors. You would usually see the 345, 77L, 788, 330, 359 and 388 at high initial cruise altitude when doing medium haul routes.
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RE: How Can The A380 Climb So High Initially?

Sat Apr 23, 2016 10:05 am

Quoting waly777 (Reply 12):
Unlikely any aircraft uses flex takeoff when close to or at MTOW which is likely the case for a DFW to SYD flight.

I don't know much about civil aviation, so this might be a daft question, but if you've got the runway for it, why not?

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RE: How Can The A380 Climb So High Initially?

Sat Apr 23, 2016 1:59 pm

Quoting astuteman (Reply 10):
the last thing an A380 needs is A LOT of runway

I saw a demo at Farnborough 2008, lightly loaded, not only a steep climb rate but appeared very slow moving at the same time. Truly impressive.
 
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RE: How Can The A380 Climb So High Initially?

Sat Apr 23, 2016 2:06 pm

Quoting Faro (Reply 11):
Those big, bulky wings make the fuselage seem like an afterthought. Among the things that make the Whalejet among the most stubby, ungainly and inelegant aircraft ever IMHO...

Don´t forget that Gallic nose... awful.
 
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RE: How Can The A380 Climb So High Initially?

Sat Apr 23, 2016 2:18 pm

Quoting waly777 (Reply 12):
Unlikely any aircraft uses flex takeoff when close to or at MTOW which is likely the case for a DFW to SYD flight.

Why? Every airplane I've flown that allowed for flex/reduced thrust takeoffs had no prohibition on MTOW takeoffs. The reduction in power is going to be a bit less, but as long as you've got the runway and climb gradient for it, you certainly can.

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RE: How Can The A380 Climb So High Initially?

Sat Apr 23, 2016 2:19 pm

When Air France flew a few training sorties out of LHR, we lined up on 27L at the intersection by T4 and rolled straight away.

We were passing 3000' by T5 and we had 516 full seats. Only about 200 litres of fuel though.
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RE: How Can The A380 Climb So High Initially?

Sat Apr 23, 2016 2:36 pm

Quoting DiamondFlyer (Reply 16):

I should clarify as I was thinking of widebodies when I wrote that.

I said it was unlikely, not impossible. However, you are more likely to see aircraft, widebodies in particular not using derated/flex takeoff at MTOW.
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RE: How Can The A380 Climb So High Initially?

Sat Apr 23, 2016 2:45 pm

Quoting uta999 (Reply 17):
Only about 200 litres of fuel though.

Are you sure about that?
 
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RE: How Can The A380 Climb So High Initially?

Sat Apr 23, 2016 3:17 pm

Quoting waly777 (Reply 12):
Unlikely any aircraft uses flex takeoff when close to or at MTOW which is likely the case for a DFW to SYD flight.

That's incorrect.

Even the A345/6 which is a runway hog compared to the A380 uses flex extensively. These numbers are from a very heavy A340 Hifly flight plan F3 takeoff, Sea level, 3570m runway:

TOW 371t, v1 150, vr 167, v2 180, green dot 271 flex41C

I'm note sure what the max flex available on the type is but it's probably in the region of 70C.

From the widebodies we operate, all bar the 777 make extensive use of flex/atm on LH flights, some of which approach 14 hour sectors.
 
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RE: How Can The A380 Climb So High Initially?

Sat Apr 23, 2016 3:38 pm

Quoting waly777 (Reply 12):
3000M is still a lot of runway, plus those lengths do not indicate the actual length required to rotate, it includes RTO stopping distance.

I have no intention of debating this with you.
Whatever Sooner787 thinks he's seeing, any image of the A380 on DFW-SYD being a runway hog would be dwarfed if he watched a 748 or 77W doing the same mission from the same runway.
The primary runways at DFW are over 4 000m long
The emphasis on the A380's use of "A LOT of runway" is not appropriate either way.
Unless it's using flex of course  

Rgds
 
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RE: How Can The A380 Climb So High Initially?

Sat Apr 23, 2016 3:42 pm



Quoting ap305 (Reply 1):
Two words : Wing loading
Quoting Sooner787 (Reply 2):
monster sets of wings

My friend related the interesting story of flying holding patterns for LHR. He always finds it fascinating to see all the 777's skidding around the tight circuits at high speed whilst he sits there hanging about serenely in the Whalejet.

Regards, JetMech

[Edited 2016-04-23 08:47:56]
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RE: How Can The A380 Climb So High Initially?

Sat Apr 23, 2016 6:57 pm

Quoting waly777 (Reply 12):

Unlikely any aircraft uses flex takeoff when close to or at MTOW which is likely the case for a DFW to SYD flight.

I don't see why not. Using max power is very hard on the engines; it shortens their life and makes a catastrophic failure on takeoff more likely. Saving the engines at the cost of using more runway when it is available makes a lot of sense, especially with 4 engines where a single failure (unless it is uncontained) is basically a non-event. I think the balance of safety AND economy would dictate using no more power than necessary for a safe takeoff with the available runway.
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RE: How Can The A380 Climb So High Initially?

Sat Apr 23, 2016 8:17 pm

Quoting 777GE90 (Thread starter):
when you compare that with a 77W with powerful GE90's on the same route, it seems to climb to much lower initial altitudes and then step climb up as it burns more fuel and gets lighter.

Engine power has nothing to do with cruise, that has to do with climb rate. What matters, as others have noted, is wing loading. The lower the wing loading, the longer the mission the plane is optimized for.

But optimal wing loading changes with technology. New aluminums or CFRP decrease the weight for increasing the wing loading. That has resulted in wings of higher aspect ration (wider but thinner which is less drag) and lower wing loading.

Each wing has a lift to drag ratio or L/D too. Engine power is what overcomes that. Newer wings have higher L/D ratios. But for your question, it is the lower wing loading that allows higher cruise.

For a given flight speed (Mach #), a certain wing loading or below is required to cruise at any altitude. Basically, the weight of the plane must drop with the reduced density of air. But planes that start light, for the size of their wing, are already below the required wing loading.

Wing loading is expressed in either pounds per square foot (lbm/ft^2) or kg/m^2 typically.

Wing loading can go up with increased flight speed (Mach#), but I'm going to compare the planes just on wing loading.
At 30,000 ft, let's assume the wing loading is 100.
At 35,000 ft, we would need 83% of the wing loading. Or... the plane has burned 17% of its weight in fuel to climb 5,000 ft higher, or the plane was just built with a larger wing.
At 40,000 ft, the wing loading must be 66% (or less) of of the wing loading enabling cruise at 30,000 ft.

"Power" enables cruise speed, but due to shockwave effects, most widebody airlines cruise at about the same Mach # (airspeed). So it is wingloading that determines cruise altitude.

Business jets do fly faster. A G650 at Mach 0.92 has 17% more lift than the same plane at Mach 0.85.

Quoting ap305 (Reply 1):

Two words : Wing loading

This is why the 777X is getting a new wing. New materials will make the plane not only lighter, but increased wingspan which improves both aspect ratio (reduces relative drag) and lowers wing loading. So the next generation 777 will climb to a very high initial height.

But some is also drag (L/D). The new wing should have less drag which might slightly optimize the cruise altitude higher if a higher cruise speed increases.


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RE: How Can The A380 Climb So High Initially?

Sat Apr 23, 2016 8:20 pm

Sorry for being ignorant but what is 'flex 41C' refering to, even using a 'flex' TO??
Many thanks.
 
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RE: How Can The A380 Climb So High Initially?

Sat Apr 23, 2016 9:38 pm

Quoting dustydesuk (Reply 25):
what is 'flex 41C' refering to

The thrust the engine would achieve with TOGA on 41C OAT day. The hotter the ambient air temperature the less thrust the engine can produce (hot air > lower air density > less air for the engine to "suck in"). In fact the real OAT is lower, but TO is done with reduced power (acc. FLX temp) which prolongs engine life.
 
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RE: How Can The A380 Climb So High Initially?

Sat Apr 23, 2016 9:55 pm

Quoting dustydesuk (Reply 25):
Sorry for being ignorant but what is 'flex 41C' refering to, even using a 'flex' TO??
http://en.wikipedia.org/wiki/Flex_temp says:

Quote:
The runway length required for an aircraft to take off is calculated for each flight. Depending on the aircraft weight, the air temperature and the wind speed, this length may be shorter than the available runway length. The crew can then calculate a lower-power engine setting where take-off will use a larger portion of the runway. Lower power settings reduce noise, engine wear, and maintenance costs.

This technique is based on air temperature, rather than percentage of engine power, because it is easy for the crew to look up or calculate the highest air temperature at which any particular take-off can be performed. That temperature is the highest flex temp that can be used.
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RE: How Can The A380 Climb So High Initially?

Sat Apr 23, 2016 10:40 pm

Quoting SEPilot (Reply 23):
Using max power is very hard on the engines; it shortens their life and makes a catastrophic failure on takeoff more likely. Saving the engines at the cost of using more runway when it is available makes a lot of sense,

Especially as most engines are either leased and/or on power by the power. Settings over X% have a disproportionate impact on surcharges, and also affect future PBH base fees.
 
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RE: How Can The A380 Climb So High Initially?

Sat Apr 23, 2016 10:52 pm

Re: FLEX. Thanks for the replies - makes sense now. Being an armchair enthusiast, I get confused over terminology and abreviations. Learning fast  
 
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RE: How Can The A380 Climb So High Initially?

Sun Apr 24, 2016 5:43 am

Quoting SEPilot (Reply 23):
I don't see why not. Using max power is very hard on the engines; it shortens their life and makes a catastrophic failure on takeoff more likely. Saving the engines at the cost of using more runway when it is available makes a lot of sense, especially with 4 engines where a single failure (unless it is uncontained) is basically a non-event

I don't either TBH.
At 4 050m long, the DFW runways would allow a current A380 (i.e. not even with uprated engines) to take off at 620 tonnes TOW on a warm day (ISA + 15), and 630 tonnes on a colder one.

QF's planes are 560 tonnes MTOW.

I certainly wouldn't challenge what Sooner787 saw. That would be daft. I wasn't there.

But if the A380's are using A LOT or runway at DFW, they're using FLEX. Period  

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RE: How Can The A380 Climb So High Initially?

Sun Apr 24, 2016 12:12 pm

Quoting astuteman (Reply 30):
But if the A380's are using A LOT or runway at DFW, they're using FLEX. Period  
Quoting lightsaber (Reply 24):
What matters, as others have noted, is wing loading. The lower the wing loading, the longer the mission the plane is optimized for.

Two statements I can only fully agree with.  
 
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RE: How Can The A380 Climb So High Initially?

Mon Apr 25, 2016 2:44 am

Quoting waly777 (Reply 12):
Quoting astuteman (Reply 10):

Unlikely any aircraft uses flex takeoff when close to or at MTOW which is likely the case for a DFW to SYD flight.

At MTOW on the 330 we'll not infrequently use TOGA even on a long runway. Typically when it's more then 25C. The FLEX margin would simply not be enough.
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RE: How Can The A380 Climb So High Initially?

Mon Apr 25, 2016 2:52 am

Quoting Starlionblue (Reply 32):
At MTOW on the 330 we'll not infrequently use TOGA even on a long runway. Typically when it's more then 25C. The FLEX margin would simply not be enough.

So there are times you don't depress the TOGA switch to activate the takeoff mode for the FD?

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RE: How Can The A380 Climb So High Initially?

Mon Apr 25, 2016 3:45 am

Quoting DiamondFlyer (Reply 33):

Quoting Starlionblue (Reply 32):
At MTOW on the 330 we'll not infrequently use TOGA even on a long runway. Typically when it's more then 25C. The FLEX margin would simply not be enough.

So there are times you don't depress the TOGA switch to activate the takeoff mode for the FD?

Airbus thrust levers don't have a TOGA switch. The thrust lever detents control modes.

There are four detents: Idle, CL (Climb), FLX/MCT and TOGA. For a FLEX take-off, the levers are moved from Idle, past CL to FLX/MCT. For a TOGA take-off they are moved all the way forward to TOGA. (For thrust symmetry purposes we pause about halfway to CL until the engines spool up to around 1.1 EPR, but there's no detent there.)

The thrust lever reaching the detent activates the modes. FLX detent will give you FLEX and SRS, while TOGA gives TOGA and SRS**. If you are in FLX and want to go TOGA, simply move the thrust levers all the way forward.

** You will also get the RWY mode if there is an ILS.
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RE: How Can The A380 Climb So High Initially?

Mon Apr 25, 2016 3:54 am

Quoting 777GE90 (Thread starter):
I noticed newer gen aircraft like the A380 / 787 seem to always have really high initial climb altitudes, for example I usually see EK A380's climb straight to FL400 from DXB to LHR, when you compare that with a 77W with powerful GE90's on the same route, it seems to climb to much lower initial altitudes and then step climb up as it burns more fuel and gets lighter.

Generally speaking airlines do not fly around at maximum possible flight level that the airframe can archive, they fly at an optimum altitude based upon their cost index. The cost index is a compromise between time and cost. If an airline has a high cost index, i.e. the direct costs are deemed the driving cost, aircraft will cruise at lower flight levels for a better true airspeed which comes at the cost of additional fuel.

On the A330 for example at heavy weights on an ISA day the airframe would just be able to make FL390 from a performance standpoint at 230t (a few tonnes below MTOW) however the optimum altitude for that weight would be FL330 as FL330 will provide the better specific range for the cost index selected. Around every 1500 nm thereafter the next optimum level will increase by around 2000 ft.

If you fly around at the maximum level, not only are you going to right on the edge for buffet boundary in you have to encounter weather or turn, you will also be burning 5-10% more fuel, and flying slower.

Quoting Starlionblue (Reply 32):
At MTOW on the 330 we'll not infrequently use TOGA even on a long runway. Typically when it's more then 25C. The FLEX margin would simply not be enough.

I am not sure what you are talking about. Do a Web RTOW for LRA, VHHH25L at 235t, QNH 1013, nil wind and temp of 40 deg C. You still will have have FLEX 44, and supplementary performance capability of 245t (10t above MTOW) with TOGA.
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RE: How Can The A380 Climb So High Initially?

Mon Apr 25, 2016 4:49 am

Quoting zeke (Reply 35):
Quoting Starlionblue (Reply 32):
At MTOW on the 330 we'll not infrequently use TOGA even on a long runway. Typically when it's more then 25C. The FLEX margin would simply not be enough.

I am not sure what you are talking about. Do a Web RTOW for LRA, VHHH25L at 235t, QNH 1013, nil wind and temp of 40 deg C. You still will have have FLEX 44, and supplementary performance capability of 245t (10t above MTOW) with TOGA.

Fair enough but I've seen the ACARS RTOW spit out TOGA when we are heavy. Then again maybe my memory is failing me and it was on a shorter runway. 
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RE: How Can The A380 Climb So High Initially?

Mon Apr 25, 2016 5:01 am

Quoting Starlionblue (Reply 36):
Fair enough but I've seen the ACARS RTOW spit out TOGA when we are heavy. Then again maybe my memory is failing me and it was on a shorter runway.

Let me guess 07RJ2 5T ?, there is a reason 07R has an EOSID and 25L does not.
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RE: How Can The A380 Climb So High Initially?

Mon Apr 25, 2016 7:31 am

Quoting lightsaber (Reply 24):
This is why the 777X is getting a new wing. New materials will make the plane not only lighter, but increased wingspan which improves both aspect ratio (reduces relative drag) and lowers wing loading.

Isn't the 779X said to be gaining quite a bit of OEW versus the -300ER ?
( Can't be all concentrated in a couple meters fuselage extention  
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RE: How Can The A380 Climb So High Initially?

Mon Apr 25, 2016 8:00 am

Quoting zeke (Reply 37):

That's the one! The iPad app gives me TOGA at 30C and QNH 1013 with dry runway at VHHH 07R taking off at MTOW.

So it's the obstacle clearance that does it, yeah?
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RE: How Can The A380 Climb So High Initially?

Mon Apr 25, 2016 8:51 am

Quoting Starlionblue (Reply 39):
So it's the obstacle clearance that does it, yeah?

Yes, do 25L and you will have a different answer  

(unless your try 25L J2, it might say its a little short)
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RE: How Can The A380 Climb So High Initially?

Mon Apr 25, 2016 3:31 pm

Quoting lightsaber (Reply 24):
What matters, as others have noted, is wing loading. The lower the wing loading, the longer the mission the plane is optimized for.

I find this interesting, as the vast majority of the world's longest flights are flown by 77Ls, 77Ws and A388s. The three aircraft would all have very different wing loadings, according to the discussions here, but all seem very well optimized for LH and ULH flying. I'm not arguing, at all. Just trying to learn. This information is very fascinating to me. I have always heard about the MD-11 having very high wing loading, and when watching videos of their take offs just this weekend, I noted how small the little wings look compared to newer WBs. I am just trying to wrap my head around the idea that the A388 is much more optimized for longer missions, whereas the 77W/L aren't as much so, but all three fly very similar missions. I assume airlines wouldn't love the 77W as much as they do, and often fly them on 12-15 hour sectors if the aircraft wasn't optimized for it.

Could you guys please elaborate further for a layman? Thanks so much for all of the interesting insights!
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zeke
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RE: How Can The A380 Climb So High Initially?

Mon Apr 25, 2016 3:44 pm

Quoting AA777223 (Reply 41):
Could you guys please elaborate further for a layman? Thanks so much for all of the interesting insights!

You have been conned by a few people who use buzz words to make them sound intelligent. An aircraft is not much different to many other forms of transport, what gets you from A to B the most efficiently wins the prize. You want to drive from New York to Miami, you will need to gas up more times in a car, and spend more on fuel per person than you would taking a greyhound. Bigger modes of transport are more efficient over larger distances, train trumps bus, ship trumps train etc.

What we look for in aircraft is called the specific air range, what gets you the furthest with the least amount of fuel, and it is not wing loading.
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AirlineCritic
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RE: How Can The A380 Climb So High Initially?

Mon Apr 25, 2016 6:55 pm

Quoting 777GE90 (Thread starter):
This confuses me as I would expect a 777 with massive GE90's to be able to outperform a super heavy A380 in the air, especially since the 777 is very capable at climbing rapidly, so what gives, how come the newer gen aircraft like the A380 are able to climb so much higher initially?

Because the A380 is not an underpowered dog.

And for avoidance of doubt, I *am* being sarcastic. There's been a lot of a.net fascination with "power" the way it is demonstrated by the 757s and 777s, and not demonstrated by the "dogs" such as A340s. In reality, not being too over-powered is an advantage... cuts down on fuel costs, gives better range, etc.

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