Thanks for the heads-up to the gear retraction video.

Is it me or is it quite fast. Plus as someone mentionned before, the main bogies seem to retract straight up into the bay.

Any reason why they would do it this way, other than it looks really neat?

The body gear retracts backwards. The 6 wheel bogie remains level with respect to the aircraft so that teh gear can stow. This gives the impression of a vertical retraction.

A 380 Again
 

Hiya All


Sorry if this as been asked and aswered already, but can anyone tell me the runway length needed for this beast to land and tak-off please.


Thanks


Mike

I wouldn't expect anybody to know at this stage !

Would guess that this needs to be determined by by test flights.

Mike - impossible to answer your question, even given test flights.

A 'minimum' length for PLANNED operations will no doubt be published but actual distances depend on too many other factors.

At what weight, with what engines at what thrust with what derate, under what atmospheric conditions (temperature, runway altitude etc.)? Mere details but significantly altering any and all performance...

A380 film on discovery
 

Discovery Channel in Sweden announced that there will be a documentary on the A380 on Sunday evening the 8th May. Looked in Discovery web site but could not see it. But keep your eyes open.

OK Maybe I should have made my question a little more specific.


Which airports will the A380 be able to land at. eg would Glasgow be long enough at 2658m.
If not how much space will it need?


Mike

The thingy has only flown once or a maybe few times and probably not at MTOW yet.

So I dare stating that at this stage, nobody in the known universe has any idea what the official safe distances are.

I think they'll have to do a lot of test takeoffs and landings in all kinds of weather and temperatures to determine the distances.

AFAIK, Heathrow and Gatwick are the only two UK Airports that are presently making specific preparations to handle the A380.

I would imagine that an A380, at typical landing weight, could probably land quite safely at Glasgow, but wing tip clearance and Apron space would be one of a number of limiting factors, in subsequently taxiing and parking the aircraft.

I wouldn't be surprised to see STN added to the list for FedEx. My back of fag packet calcs show that it would get in to GLA, but it wouldn't get out at MTOW (nor would a 747-400 - which requires a good 1500 ft more at MTOW than the A380 does).

In short, if a 747 can do it, an A380 can do it - and about 10% better.

spekesoftly

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quote:
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Which airports will the A380 be able to land at. eg would Glasgow be long enough at 2658m.
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AFAIK, Heathrow and Gatwick are the only two UK Airports that are presently making specific preparations to handle the A380.


I think you will find Manchester is also.

Add Doncaster to the list

There's an Airport Planning Doc at airbus.com (see under the 380 family on the main site rather than the reveal site) which gives graphs for temps/alts/weights and runway lengths required for Trent and GP engines, freight and pax versions.

As has been pointed out, many aircraft can beat the "standard" runway restriction if the performance penalty is worth it (say a ferry after an emergency landing at a short field, using min fuel and no pax/cargo)

A380 flight schedule
 

Airbus A380 takes off on second test flight
05.04.2005, 10:35 AM

TOULOUSE, France (AFX) - The superjumbo Airbus A380, the world's largest commercial airliner, took off over southwestern France today for its second test flight.

The European aircraft maker, based in the French city of Toulouse, said the second flight -- which came a week after the A380's maiden voyage -- would last about four hours.

A third flight is planned for later this week, probably on Saturday, followed by three flights next week, a company source told Agence France-Presse.

The plane may fly at an altitude slightly higher than the 10,000 feet achieved in the first flight, and could climb up to 13,000 feet, the source said.

Doncaster will make a nice alternate. Methinks pax ops there are a wee bit optimistic, don't you?

A380 Take-off field lenght (m sea level ISA) 2050m (2900m for the freighter). On top of that, she climbs straight to FL350
Just for fun the B777300 Take-off field lenght (m sea level ISA) 3700m. and she only clims to FL330 on MTOW.

One thing about the A380 confuses me...

Do a simple sum based on pounds of thrust and maximum take-off weight, and compare the A380 to other aircraft.

The 757 comes out at a healthy 0.34, the 747 comes out at around 0.28, while the lethargic A340-300 comes out at 0.22.

The A380 is just better than the A340-300 at 0.25.

So will the A380 be a lardy beast? Or will the massive wing area overcome the relative lack of power?

...and here are some figures for the insomniacs out there...(information from manufacturer sites)...

Aircraft Thrust MTOW Thrust / Weight
Airbus A340-300 136000 608300 0.2236
Airbus A380-800 308000 1232000 0.2500
Airbus A340-500 224000 818400 0.2737
Boeing 777-200ER 180000 654632 0.2750
Boeing 747-400ER 253200 908105 0.2788
Airbus A330-200 144000 514580 0.2798
Airbus A330-300 144000 514580 0.2798
Boeing 767-400ER 127000 449064 0.2828
Boeing 777-200 154000 543862 0.2832
Boeing 777-200LR 220200 764394.4 0.2881
Airbus A340-600 240000 809600 0.2964
Boeing 777-300ER 230600 773374.8 0.2982
Boeing 777-300 196000 654632 0.2994
Boeing 767-300ER 126600 411136 0.3079
Boeing 737-700 48400 154314.6 0.3136
Boeing 737-800 54600 173822 0.3141
Boeing 737-900 54600 173822 0.3141
Boeing 737-600 45400 143198 0.3170
Airbus A318 47600 149600 0.3182
Airbus A320 54000 169400 0.3188
Boeing 757-300 87000 271920 0.3199
Airbus A321 66000 205700 0.3209
Airbus A319 54000 166100 0.3251
Boeing 757-200ER 87000 254496 0.3419

Interesting experiment NWSRG, but in reality it's only of limited, if any, relevance. Aircraft designers generally design aircraft to be as powerful as they need to be, as this has an impact on the economics of the aircraft.

Here are some notional examples why that might be the case. They are illustrative rather than scientific.


More power is good, right?

Well, not necessarily. Let's say we took an airframe and we put on a tiny turbojet engine, just enough to get the aircraft airborne and into the cruise. The engine weighs, for example, 1 Smidgen. The aircraft flies, cruises, descends and lands. Life is good.

Let's take the same fuselage, and attach four big turbofans to it. Let's say each turbofan, being a big beast, weighs 10 Shedloads each (40 in total). That means the aicraft is now significantly heavier and more powerful than before.

The problem is that because the aircraft is heavier, it needs to generate more lift to support its weight in flight. Lift has a bitter/sweet relationship, like many things in life. If you eat cream cakes, you will get fat. If you smoke, you will get cancer. If you need to create more lift, you will also create more drag.

Assuming the only difference is the engines, more lift would be obtained by flying faster. This means using those powerful engines to their potential. But more lift means more drag, which reduces efficiency. More power also means a higher fuel consumption, which means you need to carry more fuel. More fuel means more weight. Which needs more lift. And creates more drag. Etc etc.

In reality, design engineers have to carefully balance the various characteristics of an aircraft to ensure that everything is in equilibrium. There comes a point where a bigger, more powerful engine would end up actually being counter-productive -- it would weigh too much more, drink too much more fuel, and therefore cost more.

In our example, if an engine that weighs 1 Smidgen provides enough power to do the job, why put on anything bigger?


Extra power is a waste...

In commercial aviation, if you have more power than you need to get airborne, you don't generally use it.

In a light aircraft, once you get lined up, you open the taps and hurtle down the runway at the speed of paint. Life is good.

Jet aircraft don't generally do this. If you have a runway that is 5000 metres long and taking off at full power would get you airborne in 1000 metres, you would generally elect to apply less-than-full power during the take-off. This uses more runway, and also generally uses more fuel. So why do it? Well, engines can be expensive to fix so they tend to be operated with as much sympathy as possible. A reduced-power take-off, using only the power that is really necessary to do the job, saves wear-and-tear on the turbines and prolongs engine life.

Therefore on a 757 'pocket-rocket' you may find that the crew fly reduced-power T/O's a fair bit.


Jet operating efficiency

Finally, jet engines operate at their most efficient when they are generating about 90% power. If you have a very light airframe with very powerful engines, you might find that (at cruise altitude) you only need 50% power before you hit your limiting top speed (known as Mmo).

This means that the engines are running off-optimum. This costs money. Ergo, more spare power available is not necessarily more good.

This is also the reason why some military aircraft, e.g. the Nimrod in the UK, actually shut down an engine when they are on-station. Doing so means the other three can be revved up to a more economical cruising power.


The bottom line?

Well, the bottom line is that manufacturers generally equip aircraft with engines that are powerful enough to do the job, and not much more. Remember: they are designing commercial aircraft, not hod-rods. These things are designed to make money, not burn it.

There is, evidently, some variation between aircraft and manufacturers. If you do a search on other forums, you'll find that Boeing have in the past been slightly more likely to put 'a bit extra for Mum' into the engine selection they offer on each type, giving them slightly more spare power. Airbus, on the other hand, jokingly get slagged off for being slower in the cruise and by seemingly climbing only by virtue of the curvature of the earth. Yet they are often identified as being more more economical in the cruise than some older Boeings.

The A380 designers will have looked at their aircraft. They will have looked at how economical the airframe is, looked at the airfields it's likely to use (along with their altitudes and temperatures), looked at the speeds and altitudes they'd like it to cruise at, and worked out how much power they will need from the engines. While it may seem underpowered according to your stats, it will (in theory) deliver the economies they are looking for.

Power-to-weight ratio is an interesting stat but it needs to be considered in context, most airlines wouldn't be worried about it and would be more concerned with 'operating cost per km' and similar figures.

HTH
Charley :)

p.s. have you noticed, as an aside, how your list seems to be in order of 'long-haul' to 'short-haul'? Think about it... ;)

Charley...

A very eloquent post...

However, I'm still wondering how Airbus achieve similar field lengths etc. to the 747, with a poorer power / weight ratio? Both being 4 engined, the comparison should be fairly straightforward.

Are we saying that the 747 has proportionately more surplus thrust than the A380 for any given situation? Or does the larger wing of the A380 trade drag for lift better than the 747 (presumably the answer is yes, it being a much newer aerofoil).

I'm guessing that a more modern wing design, with less drag for a given amount of lift, requires less powerful engines to achieve similar results??

Saying that, the pure numbers still suggest that the A380 will have 'relaxed' performance.;)