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Airbus: A380 has a weight problem

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Airbus: A380 has a weight problem

Old 14th Jul 2004, 22:28
  #101 (permalink)  
 
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Sorry Stagger, I did not understand what you meant by PIC.
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Old 15th Jul 2004, 10:59
  #102 (permalink)  
 
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Whats the problem with the A380 evac height? Escaping from a building is much more difficult in a panic situation and skyscrapers are still being built.
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Old 15th Jul 2004, 11:45
  #103 (permalink)  
 
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747Focal- if you read Stagger's post more carefully, there is a clue what PIC means. As for Stagger's question about PIC reaction in emergencies, pilots are well aware that in any emergency evacuation, injuries will always occur. The decision to order a full emergency evacuation is not taken lightly as a result. The deciding factor is when the risks associated with a decision to stay onboard start exceeding the risks of an evacuation- this from a pair of pilots who cannot see the outside of the aeroplane or what is happening inside the aeroplane. Not an easy decision. You can have a fatality from a 747 or a 380 with the heights in question.
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Old 15th Jul 2004, 11:45
  #104 (permalink)  
 
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GearDown&Locked - people usually escape from buildings by using the stairs. Slower than a slide but then again everyone doesn't need to be out in 90 seconds because buildings burn a bit slower than aircraft what with them usually being made of concrete and not loaded with fuel.


Notso Fantastic - glad someone understood the question! Since as you say the decision to evacuate must be made when "the risks associated with a decision to stay onboard start exceeding the risks of an evacuation" surely this balance will be different for the A380 than for other types (and is probably already different for a 747 than for other smaller types).

I have some concerns though that perceptions of the dangers associated with evacuation on the A380 may lead to decisions being made that are not entirely rational.

Here’s an analysis of the problem based on entirely hypothetical numbers…

Two hypothetical premises…

- With a stretched version of the A380 carrying 800 passengers perhaps you might expect one serious injury or fatality with every evacuation.

- With an evacuation delayed until fire or smoke has actually become detectable in the cabin perhaps you might expect 30% of the passengers to be seriously injured or killed (surely a passenger or cabin crew initiated evacuation will occur once flames are seen).

Now imagine yourself as PIC with some indication of a problem that could perhaps lead to a fire. Perhaps there is only a 1 in 100 chance that the problem will lead to a fire.

Option 1 – order an immediate evacuation as a precaution with the expectation that one person will be seriously injured or killed.

Option 2 – wait and monitor the situation knowing that there is only 1 in 100 chance of a fire developing.

The results of these courses of action…

Option 1 – one person seriously injured or killed.

Option 2 – 99 times out of 100 nobody is seriously injured or killed. But a 1 in 100 chance of 30% (i.e. 240) of passengers being seriously injured or killed. Consequently, the average of result of Option 2 is 240/100 = 2.4 serious injuries or fatalities.

So using these figures it’s always rational to accept the dangers associated with a precautionary evacuation.

Now before everyone starts rubbishing the specific numbers I’ve chosen – their just to illustrate a point. The point being that the specific numbers are important when it comes to determining what’s a rational strategy.

Last edited by stagger; 15th Jul 2004 at 12:10.
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Old 15th Jul 2004, 12:16
  #105 (permalink)  
 
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If the height is a problem... Would it be possible to retract the gear of the aircraft prior to the evac takes place? (assuming that this catastrophic scenario would consider the plane already lost from recovery). I know its a dumb idea so go easy on the beating

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Old 15th Jul 2004, 13:41
  #106 (permalink)  
 
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Stagger, I think you will find we already face those problems. On almost every widebody evacuation, someone is seriously injured (personal opinion). I think we will increasingly be facing fatalities from ultra large jets (2 candidates at the moment). It will be a difficult decision and I think will increasingly have to be made relying on external advice. Of course catastrophic events will make for an easier decision.
GD&L- retracting the gear prior to evacuating won't work:
*despite the best of intentions of engineers, gears are not designed to be retracted on the ground. I don't think hydraulics will be able to power the main gear out of 'down'.
*settling the aircraft when everybody is standing queueing to get out will have everybody over
*potential for damage/explosion (hot engines/fuel leaks from damaged tanks) too great- would likely cause further severe problems
*it would write off the aeroplane for possibly needless reasons.
*so it makes a 35' drop for the upper deck say 25-30' (personal guesses). Worth it? Aeroplane may tip tail down exacerbating the problem as the front inboard engines will take the load (before giving up).
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Old 15th Jul 2004, 14:00
  #107 (permalink)  
 
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You're right Notso, the idea just popped like that.
But thinking about it a bit more, would it be feasable to retract the gear to an "Emergency" mechanical stop position, i.e. not fully retracted but just enough to keep the engines from hitting the ground (and power wouldn't be an issue here because it could use a hyd dump valve)? or the height from the base of the engine casings to the ground won't be that much of a help on this case?

Another different question is: even with the distance reduced, how much time would be saved? 10 secs out of 90?
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Old 15th Jul 2004, 14:35
  #108 (permalink)  
 
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GearDown&Locked,

It is a nice idea in theory, but gear weight is something the designers have been working to get down for many years. Something like that would undoubtably add much more weight and then you have to justify carrying it around to the been counters. The Japanese actually tried to get Boeing to build them a fixed gear 747 version so the weight would go way down and those half hour flights with 550 people on board would be more profitable.
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Old 15th Jul 2004, 15:09
  #109 (permalink)  
 
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Don't make it any easier for us to land with the wheels up!
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Old 19th Jul 2004, 13:29
  #110 (permalink)  
 
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What’s amusing about this is that Gerard Blanc, VP of operations for Airbus, calls Noel Forgeard a liar about half way down the article.

http://seattlepi.nwsource.com/busine...problem17.html

If you go here you can fly your own A380, but you have to add to paperclips so that it simulates the over weight.

http://www.airbus.com/events/farnbor...owncolours.pdf

Last edited by 747FOCAL; 19th Jul 2004 at 13:54.
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Old 20th Jul 2004, 10:30
  #111 (permalink)  
 
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GD&L, jets with undermounted engines are designed so the lowest engines (inboards) are only a few feet off the ground. The reason undercarriage legs are as long as they are is to allow for rotation on takeoff/landing and to stop the lowest bits getting scraped- the engines. So to leave the engines undamaged by lowering the aeroplane, you have only got a metre or so at the most- not worth the technical expense of going to the trouble of a system like that.
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Old 20th Jul 2004, 10:59
  #112 (permalink)  
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From Airbus press conference today (20/7/03) at Farnborough.

The A380 programme
“We are on schedule for a first flight early next year. The business case is fully on track. We are on target to meet our guarantees to customers and to put an end to dubious figures floating around, I confirm that the maximum weight empty of the A380 is less than two per cent above our internal target, less than one per cent of the maximum take off weight”. Later he clarified that this was only 0.1 to 0.2 different from our computerised predictions.

Seemingly things are not so bad after all!
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Old 20th Jul 2004, 11:45
  #113 (permalink)  
 
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According to Airbus website - planned MTOW = 560 tonnes, planned typical empty weight = 276.8 tonnes

1% of MTOW = 5.6 tonnes
2% of empty weight = 5.5 tonnes

Are these figures very different from the "dubious figures floating around"? What were these?
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Old 20th Jul 2004, 12:18
  #114 (permalink)  
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First post says 5% of empty!
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Old 23rd Jul 2004, 10:14
  #115 (permalink)  
 
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Is overweight not a common problem on the first build?
The JSF is claimed to be way over weight also, problem more acute as it is only a 'little' fighter.
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Old 23rd Jul 2004, 10:43
  #116 (permalink)  
 
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Is overweight not a common problem on the first build?

uhhhhh, why yes, more common than previously supposed!

Boeing Talks Of 7E7 Benefits, Admits Weight Issues
Aviation Daily07/23/2004


In admitting that the Boeing 7E7 is currently slightly heavier than planned, program chief Mike Bair couldn't help but take a lighthearted jab at rival Airbus and weight problems that it may be encountering with the A380.


While he did not specify by how much the current weight exceeds targets, Bair pointed out, "We're where we have been typically on past programs," and said he was confident weight could be reduced to meet targets in the development process. "I have a lot of sympathy for our friends in Toulouse," he added, hinting at Airbus's problems to fight the Airbus A380s overweight issues. "It can run away from you very quickly. Big airplanes are really hard. We've been there."


Bair also stressed that interest in the 7E7 was "astounding" and that the bulk of the interest was in the 7E7-8 version. He disclosed, however, that a big part of the All Nippon Airways orders was for the 7E7-3. While he saw a broad customer base internationally, interest is "light in the U.S.," and executives are now "scratching their heads" over securing delivery positions for U.S. carriers. The stretched 7E7-9 is "penciled in" for initial deliveries in 2009. -JF
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Old 24th Jul 2004, 09:59
  #117 (permalink)  

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While I am sure that estimates of weights of components designed but not yet made are getting better all the time we should not forget the effects of human nature.

Design team individuals responsible for one small part of the whole have been known to over estimate the weight of their bit so that when it is actually incorporated it will not be their widget that has spoiled the party. Aero guys have been known to pad their drag estimates and reduce their lift estimates for similar reasons. I for one will only believe the weight of an aircraft once it has been built and weighed.

The Hawk was one design that performed better than estimated and I believe this was (at least in part) because of this. It was also the first Kingston fixed price contract with penalty clauses for failing to meet spec which probably increased the motivation mentioned above.

Of course there are some who use the opposite technique. They say it will weigh less than they know it will, will cost less than they know it will and rely on the customer not feeling the difference is big enough to cause cancellation.....but perhaps that sort of thing is more related to company culture than engineering?
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Old 16th Aug 2004, 10:20
  #118 (permalink)  
 
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Well, after eight pages and a lot of reading this post has finally come back to where it started - namely whether or not the A380 will be overweight.

I have just read a quote from Mike Blair in the Flight International edition for 3-9 August. There are two interesting quotes in fact. The first stated that "We are a little overweight, although less so than we were on the 777 at this point." I do not recall anybody leaping into print to knock that product , or the 7E7 for that matter, on the basis of its weight.

The second quote was a little revealing when he said of the 7E7, "All delivery positions through 2009 are committed, as is 80% of 2010. We're looking a little light on customers in the USA. At some point the US carriers are going to wake up to the 7E7 and we're going to have to tell them that we don't have any aircraft available." This is NOT meant as a dig against Boeing or the 7E7, merely a comment on the apparent lack of support for an American product from American airlines.
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Old 16th Aug 2004, 14:13
  #119 (permalink)  
 
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Name one American Airline besides Southwest that has any money to spend on new aircraft?
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