Airbus A380 Issue
 

From an email I received. The email went on to say that they also saw some signficant deflections in the main gear struts under these loads. The photo below shows what happens when you turn an A380 on the tarmac:

AirBus elected NOT to make their main landing gear system (four separate gear with four wheels apiece) steerable. Why? You save a considerable amount of weight -- not to mention some serious extra cost -- by not doing so. There is a trade-off, however ...

http://forums.pelicanparts.com/uploa...1123074586.jpg

Another pic:

http://forums.pelicanparts.com/uploa...1123074867.jpg

Send it down to Tyson @ TRE for some adjustments...

Is that the pavement that's chewed up, or is it leaving that much rubber behind?

That's chewed up pavement. I'm sure airport operators will love to see that.

Mike

I'm not an aerospace engineer - and I don't play one on TV - but it seems like frickin' common sense to make something that big steerable.

There's a picture out there of some big cargo plane landing, and it's gear are pointing one way and the plane is pointing another.

Maybe SingPilot and others can shed some light.

Well for sure all aircraft tires take a royal beating in these situations, but it seems the massive size of the A380 is really exacerbating the problem.

Like you said, I'd like to hear feedback from the guys who know more about this.

Mike

Oh my God!! Those tires are Michelins! The sidewalls are going to fail!! I am suprised Micheline has not sent a letter advising not to use the tires yet.

It's OK - they're going to put a chicane at the end of the runway to slow down the planes...

I just assumed the French aircraft design team wanted to sell French tires. Almost (can't speak for the French designed types) every Pilot's Operating Handbook advises against locked wheel turns, for this very reason.

Those are pretty amazing pictures. Another (long list) reason to stay out of an Airbus.

per PBS.org:
Clearly, the AirBUS is newer . .. which means it must be better technologically.http://www.pelicanparts.com/support/smileys/loki7.gif


. . .doesn't everyone know that? ;)

I bet the problem is with the tug driver. Some one obviously tried to pivot the plane too sharply while ground positioning it.

A cousin is a mechanic on both Boeing and Airbus airliners. The term around the maintenance base is "Scarebus".

This is a distinct possibility. The email mentioned that it was unknown whether the A380 was under it's own power or not at the time...

Mike

I think you meant bigger is better?:confused:

What does this say about the rest of the plane (engineered from the ground up)?:eek:

I could give a rats butt about Airbus vs Boeing, but many aircraft can be damaged due to improper ground handling. Many aircraft have to have pins pulled on linkages, etc and published procedures followed before being towed by tugs. The skid marks obviously show that the plane was being improperly pivoted about that gear leg, it does not neccesarily have anything to do with the design of the aircraft.

Tim, do those ground pullers have the pull to do this? (honest question)

The tugs have the ability to move the aircraft even with locked brakes, or to pivot it with the gear scrubbing just like in the pictures. I suspect that is the case with these pics. You'll note these pics are from Airbus (copyright notice in lower right corner), so they are probably using them to illustrate what NOT to do, and to document the damage.

When the nose gear is pivoted 90 degrees and pushed or pulled at that angle, the inside main gear has to pivot, while the outer gear can roll around the larger radius. This is like when you are trying to turn sharp with a tractor. You stomp on the inside wheel brake and pivot around meanwhile, the inside wheel has to skid as it is not rolling.

What Tom said above is true about some aircraft, but by no means is this the majority.

I doubt this kind of ground handling is required at most airports (severe pivoting turns).

What makes this plane different, is that there are 4 main gear trucks. Even if one truck pivots, the other is scrubbing. Looking closely at these pics (you can see which direction is forward and aft), this pivot happened with the plane moving backwards, meaning it was being pushed with a tug. Yes, this kind of manuvering is not required at any major airport, and in fact the handbooks give the minimum turning radius and maximum angle allowed on the nosegear.

This is what happenes when the book is not followed.

So why not make all or some of the gear trucks steerable?

Some of the airports (eg/SFO, SeaTac) have pretty tight confines. In fact, if my sense of proportion is not out, getting this plane to an interior gate at Atlanta is going to require fairly tight turns.

Pete;

Most of the heavies have specified taxi route and gates at every airport to take this into account. Every pilot's IOE (Initial Operating Experience) and Airport Familiarization exercise takes these situations into account. Some taxiways are not available because of wingspan or weight.

The scariest thing these days is a divert of some kind. To an airport that you are not familiar with.

There was a lot of discussion along these lines when the BA 747 continued to England after an engine failure on climbout from Los Angeles. If they had made it without incident, no one outside the industry would have even learned of it. Trouble was, they had to declare a fuel emergency and land in Ireland after not taking all the 3 engine performance charts into account.

The new A380 is rewriting some of these rules, as well as coming up with the list of airports that will be served. They had to do a bunch of wing redesign to compensate for the wingspan max limit imposed by physical limitations at the airports they wanted to serve. That is a fairly small list of intended airports for this behemoth.

Kinda like building 10 foot wide cars for use on 8 foot wide highways.
Oops!

Tight TURN=not so bad. PIVOT=not so good.

Being that the same thing happened on the 747 back when it was being developed, I have a hard time trying to figure out why Airbus thought they could get away without steerable trucks.

I think it goes back to the idea that the inventors of manned flight (the French) could not possibly have anything to learn from someone else's experience.

The Concorde crash reminded us all of that. Some things never change.

I guess if the worst thing about an Air bus is that some moron tug driver might skuff the tires and leave skid marks on the tarmac when he gets confused and tries to turn it around in a tight place, it will be in good shape.

My guess is that this will not end up being the worst thing to ever come out of operating an Air bus!

B-52
http://www.hq.nasa.gov/office/pao/History/SP-468/ch12-3.htm

Yep, the BUFF had a castering gear.

So did the. . . Cessna 195! (optional)

Years of taildragger experience teaches you to land in the exact same direction the airplane is flying. With the castering gear you fly the airplane onto the runway WITH the crosswind crab held in.

Goes against every intuition but it works.

1. Concorde run over a metal strip that separated from american airliner, which destroyed one of tires, which brought down the plane. Concorde has very high TO speed and has much smaller TO envelope.

2. Pics posted above are from gear overstress-tests. Of course, people who don't like Airbus will forget that and use it as a proof of faulty design.

Sing,

If you are refering to the BA flight that took off from LAX destined for LHR that had a engine out from shortly after t/o it landed at Manchester, not in Ireland and the issue, from the thread attahced (its bit long) was more to do with a potential fuel transfer problem that became an issue once the crossing had been completed. The crew appears to have taken into account the 'new configuration' and adapted to it. The issue which caused an ealry landing amy or may not have been directly related.

Bear in mind its only from open sources such as this that this conclusion has been reached.

http://www.pprune.org/forums/showthread.php?threadid=173143

As for the A380 landing gear much has been said on this thread http://www.pprune.org/forums/showthread.php?threadid=182113 covers the reasons for these images.

It appears to have been a test of the worse possible ( in hte testers imagination) event that could occur on the ramp.
It was a deliberate mishandling of the aircraft at max load etc etc etc.....

Again the impression given is that the design is somehow at fault.

The A380 is designed to operate within the same parameters as the B747-400.....as these standards were set along time ago and ahve proven very robust.
So turning radii and wheel loadings are within the range acceptable for current airfield specifications.

The real issue however is that the many jetway layouts are already at maximum extension with a 747. The A380 takes it over the top creating a number of problems for existing field operators. However the standards for terminals have been resivsed to accommodate the A380 (and at the time longer winged B777 versions). This means new international terminals shoul be able to accommodate the A380 if they respect these standards.

MFAFF,

That was an interesting thread. It does indicate that the 380 has four main gear, two in the fuselage and two under the wings, the gear in the wings being slighty forward of the gear in the body. As such, the aircraft cannot be turned without some of the wheels scrubbing. The 747 compensates for this by steering the body gear to minimize scrub.

It goes on further to state that the maximum steering angle with a towbar will be limited to 60 degrees in operations, but has been tested as high as 72 degrees. I can't locate the spec for a 747, but I do know that the smaller jets have a much higher steering angle.

It does appear, however, that that damage was done with the aircraft well above MGTOW.

Why do you think they didn't include a steering feature? Weight? Complexity?

"Landing Check! Mix Air Trim Pump Lights Brakes Ready to Come Aboard!" Sure could use a castering gear HERE!

http://forums.pelicanparts.com/uploa...1096979531.jpg

Well, I'm glad we finally got to the end of this. Sorry to stir the pot somewhat, but I obviously was the recipient of an email (from a fellow Boeing employee) that mis-represented these pictures.

They were neat pictures, though. Maybe to make up for it I will post some pictures of when they tested the 777 wings to failure. :>)

Mike

There is a video of that test out there somewhere. Very impressive...and the wing failed at something like 5% over the predicted failure load.

Yeah, it was amazing. I think the wingtips withstood something like 24 feet (?) of vertical displacement before failure.

Mike

IROC,

Stirring is no bad thing, provide you know how and when to ackonwledge the facts arriving on the scene.....

The reality of the steerable gear is complex.

The B-52 has it because it is 'bicycle' type u/c and is flown onto the runway, not flared as other aircraft...thus you cannot fly crabbed on approach and kick her straight before th emains touch....all 4 trucks are supposed to hit at the same time so no pivot action....the trucks are 'crabbed' to allow axial (relative wind' approached to e maintained all the way to t/d...

The 747 has them solely to allow confirmed area ops....remember the 747 was a factor of 1.7 larger in wingspan etc et cat the time to say nothing of pax numbers. Airports were not even close to being able to cope. The steerable u/c was a way of enabling 747s to use many more airports...the gear was also a useful left over of the C-X programme (later C-5Galaxy) which imposed very strict truning radii etc in 'tactical' situations. Another example of Boeing's resourcefulness.

The A380 is not being born at the same time. WEight and seat mile economics are the primary driver....so any weight (she's already a fat bird) that can be saved is a good thing....IS the scrubbing going to significantly affect tyre life compared to a heavy landing? I don't know but I imagine the trade off has been considered...

Or some would say "stubbornness". The way I heard the story told, the government specificied a high wing design for the C-X program and Boeing just knew they were smarter and offered what is now the 747 for the competition...and lost.

Of course, maybe that's the way I heard the story because I am old McDonnell Douglas... :>)

Mike

Geeze, I thought we finally got rid of all you guys... :)

Never!!!!!!! :>)

When I pointed out that the pics had the Airbus copyright logo in the corners, I suspected that there had to be more to that story. Why else would Airbus release the pics?

When I heard the HF radio calls from the BA flight (I was over the North Atlantic that night), the destination was changed to Shannon. There was a long (especially for HF) discussion with the Shanwick radio operators relaying from BA ops, requests for actual fuel remaining, and WHERE the fuel was. Your post makes that make sense. When they went to VHF, we could no longer hear (we were westbound), and I assumed they went to Ireland. The HF atmospherics that night were bad for talking eastbound, our AFIS SATCOM was even affected, and we had to relay our position reports thru Gander from 20 west (early). The BA flight was similarly affected. Thanks for the reference.

And I am also an old Douglas guy.

P.S. Thanks MFAFF, I had never seen the PPrune site.