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A380 Thrust Reversal  
User currently offlineRichiemo From United States of America, joined Jul 2008, 206 posts, RR: 0
Posted (5 years 6 months 1 day 22 hours ago) and read 6326 times:

Curious as to why only the inboard engines on the 380 have thrust reversers. Are the engines sostrong that only two are needed or does anyone know of any other reason why this would be.

45 replies: All unread, showing first 25:
 
User currently offlineManu From Canada, joined Dec 2004, 406 posts, RR: 7
Reply 1, posted (5 years 6 months 1 day 21 hours ago) and read 6314 times:

Simple... the outer engines overhang on turf or other material (off the runway). Reversing there would stir things up and cause debris to be ingested into the engines. So they don't do it.

User currently offlineManu From Canada, joined Dec 2004, 406 posts, RR: 7
Reply 2, posted (5 years 6 months 1 day 21 hours ago) and read 6292 times:

You can see what I am talking about in this 747SP landing for retirement on a 15m wide runway. Normally it is 60m.

http://www.youtube.com/watch?v=ap_nyRzEOMI


User currently offlineQF744FAN From Australia, joined Jan 2007, 120 posts, RR: 0
Reply 3, posted (5 years 6 months 1 day 21 hours ago) and read 6276 times:



Quoting Manu (Reply 1):
Simple... the outer engines overhang on turf or other material (off the runway). Reversing there would stir things up and cause debris to be ingested into the engines. So they don't do it.

Spot on!

Add to this the amazing design of its wing. The "gulling" effect is on full display when this beauty is on final approach, enabling it to come in no faster than a much smaller aircraft


User currently offlineWingedMigrator From United States of America, joined Oct 2005, 2138 posts, RR: 56
Reply 4, posted (5 years 6 months 1 day 20 hours ago) and read 6118 times:



Quoting QF744FAN (Reply 3):
The "gulling" effect is on full display when this beauty is on final approach, enabling it to come in no faster than a much smaller aircraft

The gulling has nothing to do with approach speed, and everything to do with ground clearance for the engines. The low approach speed is enabled by the very large wing, which carries less weight per unit area than most other airliners.


User currently offlineQF744FAN From Australia, joined Jan 2007, 120 posts, RR: 0
Reply 5, posted (5 years 6 months 1 day 20 hours ago) and read 6096 times:



Quoting WingedMigrator (Reply 4):
The gulling has nothing to do with approach speed, and everything to do with ground clearance for the engines. The low approach speed is enabled by the very large wing, which carries less weight per unit area than most other airliners.

That's me not being very clear... my apologies.

Such a large wing surface area, and such a long wing/wide wing span. If they weren't gulled they'd be scraping the ground on full tanks.

Large surface area allows for slower speeds with safety due to greater increases in lift production


User currently offlineAA737-823 From United States of America, joined Mar 2000, 5639 posts, RR: 11
Reply 6, posted (5 years 6 months 1 day 15 hours ago) and read 5959 times:



Quoting Manu (Reply 1):
Simple... the outer engines overhang on turf or other material (off the runway). Reversing there would stir things up and cause debris to be ingested into the engines. So they don't do it.

That is not the reason AT ALL.

In fact, in five replies, only ONE of them even ADDRESSED thrust reversers!

Quoting Richiemo (Thread starter):
Are the engines sostrong that only two are needed or does anyone know of any other reason why this would be.

By that logic, you'd only need 2 to takeoff, as well.

The answer is WEIGHT. Airbus had originally designed the aircraft with four reversers (as anyone in their right mind would expect on the heaviest, hardest-to-stop airliners ever mass produced), but late in the game, when the aircraft was coming up SEVERELY overweight, they decided to yank out the reversers on #1 and #4. Further, it was determined that it would really be a great idea to pull off the brakes on the aft axles of the body gear. Those six wheel trucks? Yep, four brakes only.

It all makes perfect sense to me- an airplane drastically larger than a 747, yet with the same number of wheel brakes, and only half the reversers.

Off of my soapbox, if you'll do a search on this forum, you will either find or not find a VERY LONG, HEATED discussion we had here. Not surprisingly, the opinions were based more on which side of the Atlantic ocean the poster was typing from. The Euro's thought it was a great idea, as reversers can't be used for landing runway length certification anyway, and the Americans thought it was stupid, because there are instances (particularly in Anchorage, Alaska, where the ground is icy 7 months a year, and UPS and FedEx were both planning on sending A380F's.... by the way, did I mention that it's illegal to dispatch an aircraft on known icy taxiway/runway conditions with an INOP thrust reverser? Yeah, how interesting) anyway, there ARE INSTANCES where you want all the reverse you can get.

I hope that answers your question.

It has nothing to do with FOD ingestion- by that standard, the 346 and 744 wouldn't have them, either, as there are more than a few runways where 744 outboard engines are exposed to turf.


User currently offlineWingedMigrator From United States of America, joined Oct 2005, 2138 posts, RR: 56
Reply 7, posted (5 years 6 months 1 day 12 hours ago) and read 5918 times:



Quoting AA737-823 (Reply 6):
That is not the reason AT ALL.

FOD is very much a reason for not having thrust reversers on the outboard engines. No other airliner has 50 meters between outboard engines and routinely operates on 45 m runways... certainly not the 744, nor the A346.

Refer to Norris's book on the A380 for more details of the story; there is rarely a single reason to do something in engineering. FOD and weight were both important considerations.

Quoting AA737-823 (Reply 6):
Further, it was determined that it would really be a great idea to pull off the brakes on the aft axles of the body gear.

Those brake units were never "pulled off" the A380-800 design, since there is sufficient capacity without them. They were present in the heavier A380-800F baseline. Future A380 models, with MTOW well north of 600 tonnes, may add those brake units. This is only one of many "scars" specifically intended for growth of the airframe.


User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 8, posted (5 years 6 months 1 day 10 hours ago) and read 5877 times:



Quoting Richiemo (Thread starter):
Curious as to why only the inboard engines on the 380 have thrust reversers. Are the engines sostrong that only two are needed or does anyone know of any other reason why this would be.

That was what they could get EASA & FAA to agree on...they originally wanted none, because they don't actually need them to meet the regulations.

Quoting QF744FAN (Reply 3):
The "gulling" effect is on full display when this beauty is on final approach, enabling it to come in no faster than a much smaller aircraft

True, it has a good approach speed, but that doesn't help the fact that you have a huge amount of mass to stop.

Quoting AA737-823 (Reply 6):
Quoting Richiemo (Thread starter):
Are the engines sostrong that only two are needed or does anyone know of any other reason why this would be.

By that logic, you'd only need 2 to takeoff, as well.

Not at all...the performance requirements for reverse and takeoff are extremely different. On an A380, you only need 3 to takeoff anyway, but there's no regulation governing engine-out reverse capability.

Quoting AA737-823 (Reply 6):
The answer is WEIGHT. Airbus had originally designed the aircraft with four reversers (as anyone in their right mind would expect on the heaviest, hardest-to-stop airliners ever mass produced)

Actually, I heard that they wanted none from the start (weight, cost, & complexity). Unfortunately, I can't find any data to prove which version is true.

Quoting AA737-823 (Reply 6):
It all makes perfect sense to me- an airplane drastically larger than a 747, yet with the same number of wheel brakes, and only half the reversers.

Number of brakes doesn't mean squat...energy capacity of the brakes is what matters. If Airbus could design a brake with ten times the energy capacity of the 747 brakes, they could probably do just fine with four.

Likewise, number of reversers doesn't mean anything by itself. You need to look at the total reverse acceleration (total reverse thrust / mass).

Tom.


User currently offlineHAWK21M From India, joined Jan 2001, 31573 posts, RR: 57
Reply 9, posted (5 years 6 months 1 day 3 hours ago) and read 5801 times:

Wasn't exceeding planned Weight limits,the real issue for A380 opting out of the Outboard T/Rs?
regds
MEL.



Think of the brighter side!
User currently offlineFinkenwerder From Germany, joined Apr 2005, 147 posts, RR: 0
Reply 10, posted (5 years 6 months 1 day 3 hours ago) and read 5799 times:

All above partially correct....the wing is not designed to sustain 4 engines in TR torsion would be excessive on the outer pylons.

User currently offlineAA737-823 From United States of America, joined Mar 2000, 5639 posts, RR: 11
Reply 11, posted (5 years 6 months 1 day 2 hours ago) and read 5798 times:



Quoting Finkenwerder (Reply 10):
All above partially correct....the wing is not designed to sustain 4 engines in TR torsion would be excessive on the outer pylons.

Well that's the easiest explanation to believe so far, considering that the ONLY A380 wing ever tested to failure actually broke BEFORE THE LEGAL LIMIT.

Quoting Tdscanuck (Reply 8):
Likewise, number of reversers doesn't mean anything by itself. You need to look at the total reverse acceleration (total reverse thrust / mass).

True, but I think we can agree that FOUR reversers will provide more acceleration than TWO, all else being equal, which in this case, it is.

Quoting Tdscanuck (Reply 8):
because they don't actually need them to meet the regulations.

No airliner does, yet with the noted exception of the BAe-146, all of them managed to get them... and they're heavy on all the other ones, too.

Quoting Tdscanuck (Reply 8):
Actually, I heard that they wanted none from the start (weight, cost, & complexity). Unfortunately, I can't find any data to prove which version is true.

That certainly may be the case, I don't know. But I am under the strong impression that there were four reversers until VERY late in the game, well after the first aircraft had been assembled.

Quoting Tdscanuck (Reply 8):
If Airbus could design a brake with ten times the energy capacity of the 747 brakes, they could probably do just fine with four.

Yes, you're right. But the 747-400 has very good brakes- good enough that you can dispatch with an ENTIRE gear's worth of brakes (4 wheels, I mean) INOP. With the heavier A380 weights, do you (or anybody here) know if they've got that capability.


User currently offlineFinkenwerder From Germany, joined Apr 2005, 147 posts, RR: 0
Reply 12, posted (5 years 6 months 1 day 2 hours ago) and read 5796 times:

Bear in mind for performance purposes reverser availability gains no credit for stopping distance. It's all about the brakes...

User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 13, posted (5 years 6 months 1 day 2 hours ago) and read 5795 times:



Quoting AA737-823 (Reply 6):
by the way, did I mention that it's illegal to dispatch an aircraft on known icy taxiway/runway conditions with an INOP thrust reverser?

Not according to our MEL!


User currently offlineStarlionblue From Greenland, joined Feb 2004, 16908 posts, RR: 67
Reply 14, posted (5 years 6 months 1 day ago) and read 5740 times:



Quoting AA737-823 (Reply 6):
The answer is WEIGHT. Airbus had originally designed the aircraft with four reversers (as anyone in their right mind would expect on the heaviest, hardest-to-stop airliners ever mass produced), but late in the game, when the aircraft was coming up SEVERELY overweight, they decided to yank out the reversers on #1 and #4.

It's the other way around. It was originally designed with no reversers. Comparing brakes and reversers, the brakes are hugely more effective. It's all about the brakes. Reversers are a nice to have in the vast majority of cases.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently onlineTristarSteve From Sweden, joined Nov 2005, 3930 posts, RR: 34
Reply 15, posted (5 years 6 months 20 hours ago) and read 5699 times:



Quoting PhilSquares (Reply 13):
Quoting AA737-823 (Reply 6):
by the way, did I mention that it's illegal to dispatch an aircraft on known icy taxiway/runway conditions with an INOP thrust reverser?

Not according to our MEL!

We have the following
B767 and B757 One reverser may be inop, Operation on Slippery runways not allowed.
A320 Both reversers may be inop. It is inadvisable to operate on slippery runways as the required distance may be more than available.
B777 One may be inop. no restrictions
B744 Two may be inop, must be symmetrical, and most of the brakes must be working.


User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 16, posted (5 years 6 months 8 hours ago) and read 5560 times:



Quoting AA737-823 (Reply 11):
Well that's the easiest explanation to believe so far, considering that the ONLY A380 wing ever tested to failure actually broke BEFORE THE LEGAL LIMIT.

That's true, but it doesn't mean they violated regulations. I know you didn't say that, but you seem to be implying there was something improper...the FAR's (and whatever EASA is calling their regulations now) just require that the OEM show that the wing withstand ultimate load without breaking...they don't say how you have to show that. A test to almost the limit, plus analysis of design changes, may be sufficient. In the case of the A380, it was.

Quoting AA737-823 (Reply 11):
Quoting Tdscanuck (Reply 8):
Likewise, number of reversers doesn't mean anything by itself. You need to look at the total reverse acceleration (total reverse thrust / mass).

True, but I think we can agree that FOUR reversers will provide more acceleration than TWO, all else being equal, which in this case, it is.

Well, yes, but eight engines will provide more thrust (and reverse) than four, all else being equal...that doesn't mean they should have eight engines.

Quoting AA737-823 (Reply 11):
Quoting Tdscanuck (Reply 8):
because they don't actually need them to meet the regulations.

No airliner does, yet with the noted exception of the BAe-146, all of them managed to get them... and they're heavy on all the other ones, too.

It's not necessarily about regulations, it's also about performance. Despite the rampant myth on airliners.net, current certifications *do* allow you to take reverser credit on wet runways, which is important for some performance situations.

Quoting Finkenwerder (Reply 12):
Bear in mind for performance purposes reverser availability gains no credit for stopping distance.

Only on dry runways...on wet, you can take credit. This was a fairly recent change (last ~12 years or so)...all the prior stuff never had certified limits for wet runways.

Tom.


User currently offlineFinkenwerder From Germany, joined Apr 2005, 147 posts, RR: 0
Reply 17, posted (5 years 6 months 7 hours ago) and read 5543 times:



Quoting Tdscanuck (Reply 16):
Only on dry runways...on wet, you can take credit. This was a fairly recent change (last ~12 years or so)...all the prior stuff never had certified limits for wet runways.

Tom.

Your quite right, the obvious exception....  banghead 


User currently offlineHAWK21M From India, joined Jan 2001, 31573 posts, RR: 57
Reply 18, posted (5 years 6 months 1 hour ago) and read 5470 times:



Quoting PhilSquares (Reply 13):
Not according to our MEL!

Which types are you reffereingtoo.
Out here its no-go under wet/rainy conditions with Inop T/R for
A300/310/320/330/340/B737/747/757/767/777.
regds
MEL



Think of the brighter side!
User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2532 posts, RR: 24
Reply 19, posted (5 years 5 months 4 weeks 21 hours ago) and read 5254 times:



Quoting AA737-823 (Reply 6):
Off of my soapbox, if you'll do a search on this forum, you will either find or not find a VERY LONG, HEATED discussion we had here. Not surprisingly, the opinions were based more on which side of the Atlantic ocean the poster was typing from. The Euro's thought it was a great idea, as reversers can't be used for landing runway length certification anyway, and the Americans thought it was stupid, because there are instances (particularly in Anchorage, Alaska, where the ground is icy 7 months a year, and UPS and FedEx were both planning on sending A380F's.... by the way, did I mention that it's illegal to dispatch an aircraft on known icy taxiway/runway conditions with an INOP thrust reverser? Yeah, how interesting) anyway, there ARE INSTANCES where you want all the reverse you can get.

Please don't generalise so. I'm a "Euro" and I thought reversers were probably a good idea on the A380. I'm certain there are "Yanks" who think the A380 is marvellous. Reducing the A v B debate to nationalism is crazy.

My argument was they should either have four reversers or none. Not two with and two without. If one of the inboard engines is out, the other inboard reverse thrust would create a lot of asymmetry, so effectively you have no reverse.

The usual answer to the icy runway/no reversers argument is "divert". However with a mammoth like the A380 your choices are more limited. Not to mention 500 pax to transport to their proper destination.  Wink

Quoting Tdscanuck (Reply 8):
True, it has a good approach speed, but that doesn't help the fact that you have a huge amount of mass to stop.

It's also about energy, which increases with the square of speed. So a few knots off approach speed makes a big difference to stopping distance.

Quoting AA737-823 (Reply 11):
No airliner does, yet with the noted exception of the BAe-146, all of them managed to get them... and they're heavy on all the other ones, too.

Not just the 146. The Fokker F.28 had no reversers either. Actually the 146 has a low ground idle setting which is surprisingly effective in increasing deceleration, not to mention liftdumpers AND a speedbrake (like the F.28).

The FOD argument is a red herring in my view. The A380 outboard engines aren't much further outboard than those of a 747. As long as reverse is cancelled before speed gets too low, foreign objects won't get into the engines.



The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 20, posted (5 years 5 months 4 weeks 20 hours ago) and read 5235 times:



Quoting Jetlagged (Reply 19):
If one of the inboard engines is out, the other inboard reverse thrust would create a lot of asymmetry, so effectively you have no reverse

To be honest, there is very little asymmetry from a reverser inop. Generally, the EEC/FADEC will limit reverse thrust to 70% N1 or so. I have worked for airlines where SOP is to use all reverse in an engine out landing. Don't worry about asymmetry as normal steering through the rudders will take care of that.


User currently offlinePGNCS From United States of America, joined Apr 2007, 2757 posts, RR: 45
Reply 21, posted (5 years 5 months 4 weeks 18 hours ago) and read 5202 times:



Quoting AA737-823 (Reply 6):
Airbus had originally designed the aircraft with four reversers (as anyone in their right mind would expect on the heaviest, hardest-to-stop airliners ever mass produced),

Hardest to stop? It has slow approach speeds and excellent brakes. We all know you hate Airbus, but give it a rest.

Quoting Tdscanuck (Reply 8):
True, it has a good approach speed, but that doesn't help the fact that you have a huge amount of mass to stop.

But having appropriate brakes for the mass of the aircraft does. In any case a landing at normal weights is no real challenge to the brakes; the RTO requirements are much more taxing.

Quoting AA737-823 (Reply 11):
considering that the ONLY A380 wing ever tested to failure actually broke BEFORE THE LEGAL LIMIT.

So you're a certification expert now, too? The wing failed so close to the design limit that the issue was addressed by analysis and changes that the authorities allowed without requiring the very expensive retest of the wing.

Quoting Tdscanuck (Reply 16):
Quoting AA737-823 (Reply 11):
Well that's the easiest explanation to believe so far, considering that the ONLY A380 wing ever tested to failure actually broke BEFORE THE LEGAL LIMIT.

That's true, but it doesn't mean they violated regulations. I know you didn't say that, but you seem to be implying there was something improper...the FAR's (and whatever EASA is calling their regulations now) just require that the OEM show that the wing withstand ultimate load without breaking...they don't say how you have to show that. A test to almost the limit, plus analysis of design changes, may be sufficient. In the case of the A380, it was.

Well put, Tdscanuck. Thank you.

Quoting Jetlagged (Reply 19):
Please don't generalise so. I'm a "Euro" and I thought reversers were probably a good idea on the A380. I'm certain there are "Yanks" who think the A380 is marvellous.

I am an American and think the A-380 is a brilliant piece of engineering. I wish my operator would buy some. Jetlagged, while I have had disagreements with you before, I always find you to be rational and well-informed. Just because some here rail against Airbus, doesn't mean that all of us are closed-minded and self-righteous. Having flown both Airbus and Boeing, I find the Airbus to be a superior product overall, so count me as a "Yank" who thinks the A-380 (and other FBW Airbus models) are marvelous.

Quoting Jetlagged (Reply 19):
My argument was they should either have four reversers or none. Not two with and two without. If one of the inboard engines is out, the other inboard reverse thrust would create a lot of asymmetry, so effectively you have no reverse.

I respectfully don't buy this given my prior experience. The carrier I flew the 744 for used all reversers on an engine out landing and directional control was never difficult in any way. I don't know the internal deliberations that occurred at Airbus on this design, but I DO think the engineers there are more than competent and I trust them to have made the most appropriate design trade. Certainly Airbus has knowledge on this subject far exceeding our collective insight, and the design caused no difficulties in certification.

Quoting PhilSquares (Reply 20):


Quoting Jetlagged (Reply 19):
If one of the inboard engines is out, the other inboard reverse thrust would create a lot of asymmetry, so effectively you have no reverse

To be honest, there is very little asymmetry from a reverser inop. Generally, the EEC/FADEC will limit reverse thrust to 70% N1 or so. I have worked for airlines where SOP is to use all reverse in an engine out landing. Don't worry about asymmetry as normal steering through the rudders will take care of that.

Agreed.


User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2532 posts, RR: 24
Reply 22, posted (5 years 5 months 4 weeks 16 hours ago) and read 5165 times:



Quoting PhilSquares (Reply 20):
To be honest, there is very little asymmetry from a reverser inop. Generally, the EEC/FADEC will limit reverse thrust to 70% N1 or so. I have worked for airlines where SOP is to use all reverse in an engine out landing. Don't worry about asymmetry as normal steering through the rudders will take care of that.

Fair enough, I well understand that reverse asymmetry is a fraction of the asymmetry you might have on takeoff, especially if it is inboard. However I was thinking particularly of low friction contaminated runways, where reverse thrust asymmetry might become more important since wheel braking and lateral tyre friction are minimal. Rudder effectiveness reduces rapidly with forward speed, and reverse thrust reduces it even further.

Still these are rare circumstances and the design should not be compromised by one special case.

Quoting PGNCS (Reply 21):
Jetlagged, while I have had disagreements with you before

Really? Nothing serious I hope.  Smile

Quoting PGNCS (Reply 21):
Certainly Airbus has knowledge on this subject far exceeding our collective insight, and the design caused no difficulties in certification.

100% agree.



The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 23, posted (5 years 5 months 4 weeks 15 hours ago) and read 5150 times:



Quoting Jetlagged (Reply 22):
Fair enough, I well understand that reverse asymmetry is a fraction of the asymmetry you might have on takeoff, especially if it is inboard. However I was thinking particularly of low friction contaminated runways, where reverse thrust asymmetry might become more important since wheel braking and lateral tyre friction are minimal. Rudder effectiveness reduces rapidly with forward speed, and reverse thrust reduces it even further.

It's called judgement. I would argue you wouldn't want to go into a airport as you describe unless there is no other alternative. With autobrakes, even landing on a contaminated runway, isn't that big of a deal. Remember, stopping distances don't take into account reverse thrust, so even though you can use asymmetrical reverse there is no mandate you have to.

I don't understand your comments about reverse thrust decreasing rudder effectiveness. On every aircraft I have flown, that has had reverse thrust, there is no decrease of rudder effectiveness with the use of reverse. It does decrease as airspeed decreases. On a contaminated runway, judicious use of reverse on the asymmetrical engine minimises any problem with directional control.

That's what we get paid for!!!!.


User currently offlineAA737-823 From United States of America, joined Mar 2000, 5639 posts, RR: 11
Reply 24, posted (5 years 5 months 4 weeks 15 hours ago) and read 5137 times:



Quoting Jetlagged (Reply 19):
Please don't generalise so. I'm a "Euro" and I thought reversers were probably a good idea on the A380. I'm certain there are "Yanks" who think the A380 is marvellous. Reducing the A v B debate to nationalism is crazy.

Haha, fair enough. I think that reducing it to nationalism is crazy as well, and yet that's what nearly always happens. I am not a fan of the A380, but it's not because I'm an American. Boeing doesn't really build anything to compete with the aircraft, so I have nothing to gain by senseless nationalism.
By the way- you're not a Euro, you're from the UK. Big difference!

Quoting PhilSquares (Reply 13):
Not according to our MEL!

The MEL for the airline I USED to be associated with stated that ANY inop reverser was a no-go item if the taxiways and runways were icy, which in Anchorage, Alaska is the case much of the year. That COULD be tied to an... incident... that carrier had here many years ago, but for what it's worth, they were no-go for us 6 months out of the year.

Quoting PGNCS (Reply 21):
Hardest to stop? It has slow approach speeds and excellent brakes. We all know you hate Airbus, but give it a rest.

Really? Odd, as I choose to fly in their aircraft across Ye Olde Atlantique on 66% of my flights.
Further, I have absolutely RAILED on Randy Tinseths' blog over at Boeing, regarding the noise issue in the 787 cabin.
Before you make inflammatory statements, you should make sure the person you're accusing is actually as childish as you think.
I'm not quite there..... unless you push me REEEEEEAL hard.

Quoting PGNCS (Reply 21):
So you're a certification expert now, too?

Haha, any idiot with a baguette and a glass of wine can say "oh crap" when a wing breaks before it's supposed to. And I don't even have a baguette or a glass of wine.
Doesn't take an expert, buddy.... doesn't take an expert.


25 WingedMigrator : I'm one. They are, by 23%. The A380 outboard engines are 51.4 m apart (center-to-center); the 747's are 41.7 m apart. When you operate on a 45 m (150
26 Jetlagged : The effect is most noticeable with tail mounted engines for obvious reasons as the engines are close to the fin so airflow over the rudder is directl
27 Tdscanuck : The yaw control requirements for an engine out at takeoff will vastly overshadow any adverse yaw you'd get from reverse asymmetry. Since the aircraft
28 Jetlagged : You are assuming there is no concrete beyond the marked runway edges. The paved width could well be twice the runway width. It will certainly be a lo
29 Astuteman : Which the A380-800 passed with ease, BTW.... Maybe so, but the chances of FOD ingestion have to be a lot greater when the outboard engines are on the
30 Jetlagged : The distance from the outer side of one outboard engine pylon to the other is approx 55m on an A380. On pavement 90m wide, there is therefore 17.5m o
31 Francoflier : The 744 has 'good brakes' alright, but you are being a bit generic and vague with your arguments (you'd make a good political campaign adviser ), and
32 Astuteman : Can't argue with that - if the pavement is 90m wide... Rgds
33 Starlionblue : 20 years later than 744, 15 years later than 340. It's amazing how technology progresses.
34 Viscount724 : The F-28 and BAe146 were used without problems in northern Canada for years where snow-covered runways are common 8 months of the year.
35 Jetlagged : OK, there won't be many runways with 90m pavement, but those that an A380 will use will likely be a lot wider than 45m. 60m would be more than enough
36 Finkenwerder : Incidently the A380 MMEL permits dispatch with 1 or more reversers inop. As long as they are locked out, with appropriate ECAM indications.
37 Northwest727 : If I am not mistaken, another reason the outboards on the A380 don't have reversers is to reduce weight and costs.
38 Viscount724 : The standard VC-10 had reversers on the outboard engines only. The prototype had reversers on all 4 engines but not the production aircraft. Weight w
39 Starlionblue : As mentioned in Reply 6...
40 PlaneWasted : Wonder if this is true? The hardest to stop part.. With the higher landing speed of the 747 it might actually have more kinetic energy to brake away.
41 NicoEDDF : I doubt the 380 will always get priority for 25R/7L in FRA as opposed to 27L/7R. The former has 60m, the latter 45m. So I think it will be more than
42 Jetlagged : The published width of 45m refers to the marked runway. A quick look at Google Earth shows there is a few meters of tarmac outside this. The prepared
43 Post contains links and images WingedMigrator : I dunno. For reference, here's a take-off on a 45 m runway: View Large View MediumPhoto © Stewart Andrew Maybe that picture tells you everything
44 Astuteman : I think the issue here is not the frequency of landing on 45m wide runways, but the fact that it undoubtedly will at some time, and has been designed
45 Tdscanuck : Reversers don't inhale FOD until the speed is relatively low (below 80 knots or so) and you normally kill reversers by then anyway. Plus the A380 out
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