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Will The 787 Landing Gear Need Redesign?  
User currently offlineSpeedmarque From United Kingdom, joined Jul 2005, 684 posts, RR: 1
Posted (8 years 3 months 3 weeks 5 days 4 hours ago) and read 6401 times:

Hello,

Pics I have seen so far have shown the 787 to have an 8 wheel main gear set-up (4 on each bogey like a 767). My question is will this be enough to cope with the 787-10 length and weight considering a 773 and A346 has 12 main wheels?

Any ideas or has this already been taken care of at Boeing and I have just missed it!

Cheers, enjoy your Sunday!

17 replies: All unread, jump to last
 
User currently offlineZvezda From Lithuania, joined Aug 2004, 10511 posts, RR: 64
Reply 1, posted (8 years 3 months 3 weeks 5 days 3 hours ago) and read 6349 times:

The main gear on the B787 are good for MTOW up to about 540,000 to 560,000 lbs. Higher MTOWs will require the addition of a center two-wheel bogey slightly aft of the existing main gear. This is the same solution that Airbus applied to the A340-300 to increase the MTOW for the A340-500 and A340-600.

User currently offlineRheinbote From Germany, joined May 2006, 1968 posts, RR: 52
Reply 2, posted (8 years 3 months 3 weeks 5 days 3 hours ago) and read 6291 times:

Quoting Zvezda (Reply 1):
Higher MTOWs will require the addition of a center two-wheel bogey

The adoption of 777-style six-wheel bogies appears more likely. In any case, quite a hassle as the current landing gear bay design probably can't pack a six-wheel bogie, so the rear bulkhead needs to be moved aft and the aft E/E bay with it.


User currently offlineZvezda From Lithuania, joined Aug 2004, 10511 posts, RR: 64
Reply 3, posted (8 years 3 months 3 weeks 5 days 2 hours ago) and read 6225 times:

Quoting Rheinbote (Reply 2):

The adoption of 777-style six-wheel bogies appears more likely.

Why do you think so?

Quoting Rheinbote (Reply 2):
the current landing gear bay design probably can't pack a six-wheel bogie

That is my understanding. It would be astonishing if it could.

Quoting Rheinbote (Reply 2):
so the rear bulkhead needs to be moved aft

Why do you think so? My understanding is that there is space just forward of the pressure bulkhead that would accomodate a two-wheel center bogey.

Adding two tyres would give the undercarriage all the capacity the wings have -- about 640,000 lbs. Being aft of the existing main gear, it would also help with rotation in the case of the longer variants.


User currently offlineDalecary From , joined Dec 1969, posts, RR:
Reply 4, posted (8 years 3 months 3 weeks 5 days 2 hours ago) and read 6201 times:

If the 787-10 stays at the same MTOW as the -9 no landing gear change will be required. However, if Boeing decide to go with a heavier, slightly bigger -10X, changes to the main landing gear will be required.

User currently offlineRheinbote From Germany, joined May 2006, 1968 posts, RR: 52
Reply 5, posted (8 years 3 months 3 weeks 5 days 2 hours ago) and read 6145 times:

Quoting Zvezda (Reply 3):
Why do you think so? My understanding is that there is space just forward of the pressure bulkhead that would accomodate a two-wheel center bogey.

The current wheel bay and keel beam design doesn't suggest that to me.


User currently offlineSpeckSpot From United States of America, joined Jul 2005, 46 posts, RR: 0
Reply 6, posted (8 years 3 months 3 weeks 4 days 4 hours ago) and read 4513 times:

So with an extra two wheel bogey in the middle, just slightly aft, does that mean that when it is rotating, for a split second it is going to be on only one bogey (th e middle one) which is the last to lift off? I mean, it is possible that the other two main bogeys will still have their rear set on the ground, but how much weight could they be bearing then? Intuitively it seems like the weight (whatever is left of it not being borne by the wings) will all be on that center bogey if it is aft of the other two, and it seems odd. Comments anyone?

User currently offlineZvezda From Lithuania, joined Aug 2004, 10511 posts, RR: 64
Reply 7, posted (8 years 3 months 3 weeks 4 days 4 hours ago) and read 4461 times:

Quoting SpeckSpot (Reply 6):
So with an extra two wheel bogey in the middle, just slightly aft, does that mean that when it is rotating, for a split second it is going to be on only one bogey (th e middle one) which is the last to lift off?

Yes.

Quoting SpeckSpot (Reply 6):
I mean, it is possible that the other two main bogeys will still have their rear set on the ground, but how much weight could they be bearing then? Intuitively it seems like the weight (whatever is left of it not being borne by the wings) will all be on that center bogey if it is aft of the other two, and it seems odd. Comments anyone?

At any time the center bogey is the only one in contact with the ground, most of the aircraft's weight will be borne by the wings which will be generating a lot of lift.


User currently offlineAstuteman From United Kingdom, joined Jan 2005, 10031 posts, RR: 96
Reply 8, posted (8 years 3 months 3 weeks 4 days 4 hours ago) and read 4372 times:
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Quoting Zvezda (Reply 3):
Quoting Rheinbote (Reply 2):

The adoption of 777-style six-wheel bogies appears more likely.

Why do you think so?

I put this forward without any specific knowledge of the point in case, Zvezda, but, taking technical feasibility as a given, I would imagine that 2 x 6 wheel bogies would be both lighter and simpler (therefore cheaper) than 3 x 4 wheel bogies.
But as I say, that's just me guessing  Smile.
Regards


User currently offlineLumberton From United States of America, joined Jul 2005, 4708 posts, RR: 20
Reply 9, posted (8 years 3 months 3 weeks 4 days 2 hours ago) and read 4204 times:

Here's some info on the subject from an article in Aviation Week:

Quote:
The larger wing will likely be the baseline for the 787-10, the stretch of the -9 now under consideration. The -10 is response to Emirates's interest in a 300-plus-seat aircraft with 787 technology. Boeing expects a formal launch decision in the next 12 months. But the -10's configuration, which is still far from being set, didn't drive the wing change, he insists. He notes that the -10 will keep the same MTOW as the -9 because of limits imposed by its four-wheel main landing gears.

Boeing Revises 787-9 Plan



"When all is said and done, more will be said than done".
User currently offlineBoeing Nut From , joined Dec 1969, posts, RR:
Reply 10, posted (8 years 3 months 3 weeks 4 days 1 hour ago) and read 4160 times:

Quoting Astuteman (Reply 8):
Quoting Zvezda (Reply 3):
Quoting Rheinbote (Reply 2):

The adoption of 777-style six-wheel bogies appears more likely.

Why do you think so?

I put this forward without any specific knowledge of the point in case, Zvezda, but, taking technical feasibility as a given, I would imagine that 2 x 6 wheel bogies would be both lighter and simpler (therefore cheaper) than 3 x 4 wheel bogies.
But as I say, that's just me guessing

In this case, I believe that a center bogey will be incorporated. Reason - for a six wheeled bogey to be used would take a massive redesign of the fuselage/wingbox/gear stowage area. That would take big R&D bucks to do so. That is, if there is room to do this in the first place. If there's no room then the six wheelers are the only way to go.

But that's just me guessing as well!  wave 

Regards


User currently offlineOryx From Germany, joined Nov 2005, 126 posts, RR: 0
Reply 11, posted (8 years 3 months 3 weeks 4 days ago) and read 4071 times:

Quoting Zvezda (Reply 7):
At any time the center bogey is the only one in contact with the ground, most of the aircraft's weight will be borne by the wings which will be generating a lot of lift.

As far as I understand this, the rotation is initated by the deflection of the elevator. Its downward force ads to the weight of the plane. As the most rearward bogey is the rotation point, theoretically all forces act on the last bogey. The wings do only produce lift after the planes has already rotated somewhat.


User currently offlineZvezda From Lithuania, joined Aug 2004, 10511 posts, RR: 64
Reply 12, posted (8 years 3 months 3 weeks 3 days 23 hours ago) and read 3994 times:

Quoting Astuteman (Reply 8):
I would imagine that 2 x 6 wheel bogies would be both lighter and simpler (therefore cheaper) than 3 x 4 wheel bogies.

There is no proposal for 3 x 4 wheel bogeys. Boeing are looking at adding a 2 wheel (not 4 wheel) center bogey. This is exactly the same solution that Airbus chose for the A340.

Quoting Oryx (Reply 11):
As far as I understand this, the rotation is initated by the deflection of the elevator. Its downward force ads to the weight of the plane. As the most rearward bogey is the rotation point, theoretically all forces act on the last bogey. The wings do only produce lift after the planes has already rotated somewhat.

The gear are sprung. The center bogey would be only slightly aft of current main gear. During most of rotation, all ten wheels would be on the ground. Only during the final moments of rotation, when the wings have already taken most of the load, would only the center 2 wheels still be in contact with the ground.


User currently offlineOryx From Germany, joined Nov 2005, 126 posts, RR: 0
Reply 13, posted (8 years 3 months 3 weeks 3 days 22 hours ago) and read 3994 times:

Quoting Zvezda (Reply 12):
The gear are sprung.

Yep, didn't think of it.


User currently offlineDfwRevolution From United States of America, joined Jan 2010, 977 posts, RR: 51
Reply 14, posted (8 years 3 months 3 weeks 3 days 22 hours ago) and read 3994 times:

Quoting Zvezda (Reply 12):
Boeing are looking at adding a 2 wheel (not 4 wheel) center bogey. This is exactly the same solution that Airbus chose for the A340.

As well as the DC-10 and MD-11, no?

Quoting Dalecary (Reply 4):
However, if Boeing decide to go with a heavier, slightly bigger -10X, changes to the main landing gear will be required.

Now I know this is a simple matter of semantics, but when you say "bigger," I assume you mean heavier?

I was under the impression that given Boeing nomenclature the -10X and -10 were the same capacity, but the -10X had a higher MTOW and payload/range.


User currently offlineSpeckSpot From United States of America, joined Jul 2005, 46 posts, RR: 0
Reply 15, posted (8 years 3 months 3 weeks 3 days 21 hours ago) and read 3994 times:

Thanks for the answers, Zvezda and Oryx. Nice to know these things  Smile.

That means touchdown will also be on the single bogey for a split second. I believe it, but it just feels bizarre. There's something about touching down on
two bogeys that just feels right  Smile.

Speckspot.


User currently offlineSpeedmarque From United Kingdom, joined Jul 2005, 684 posts, RR: 1
Reply 16, posted (8 years 3 months 3 weeks 3 days 21 hours ago) and read 3994 times:

Thanks for your insights.

Speedy


User currently offlineOryx From Germany, joined Nov 2005, 126 posts, RR: 0
Reply 17, posted (8 years 3 months 3 weeks 3 days 3 hours ago) and read 3907 times:

Quoting SpeckSpot (Reply 15):
That means touchdown will also be on the single bogey for a split second. I believe it, but it just feels bizarre.

Yes, but it will imediately contract like the shock absorbers in a car. So actually only the load of the internal springs are on the gears.


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