Max Q
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Landing Gear Length On The 787-10 Inadequate?

Sat Nov 17, 2012 12:35 am

The 787-8 sits pretty low to the ground, one of the reasons it looks deceptively small.


The landing gear is not overly tall looking to me leading me to wonder if Boeing plans on extending it for the -9 series and especially the planned -10.


I would think that tail clearance on rotation would be a real problem on the -10 in particular.


Thoughts, opinions ?
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Stitch
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RE: Landing Gear Length On The 787-10 Inadequate?

Sat Nov 17, 2012 1:37 am

Quoting Max Q (Thread starter):
The landing gear is not overly tall looking to me leading me to wonder if Boeing plans on extending it for the -9 series and especially the planned -10.

The 787-10 will use the same undercarriage as the 787-9 to the best of my knowledge. I imagine it will have re-calibrated anti-tailstrike software to account for the extra aft length.
 
tdscanuck
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RE: Landing Gear Length On The 787-10 Inadequate?

Sat Nov 17, 2012 2:06 am

Quoting Max Q (Thread starter):
I would think that tail clearance on rotation would be a real problem on the -10 in particular.

The extra fuselage length isn't going to help, but the 787 tailstrike law is *very* good. It can reliably plant the tail a foot from the runway so you can safely and repeatedly get the full rotation angle.

Tom.
 
fr8mech
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RE: Landing Gear Length On The 787-10 Inadequate?

Sat Nov 17, 2012 2:07 am

I'll suggest that any aircraft that has a tail-skid has landing gear that is too short. But, that's a trade-off in design.

Quoting Stitch (Reply 1):
anti-tailstrike software

Aren't new aircraft grand? If you trust the system (and I don't see a reason why you shouldn't) you don't need the tai-skid anymore, do you?
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tdscanuck
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RE: Landing Gear Length On The 787-10 Inadequate?

Sat Nov 17, 2012 3:17 am

Quoting fr8mech (Reply 3):
If you trust the system (and I don't see a reason why you shouldn't) you don't need the tai-skid anymore, do you?

On the 787 they actually refer to the system as an "electronic tailskid"...there is no physical skid.

Tom.
 
fr8mech
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RE: Landing Gear Length On The 787-10 Inadequate?

Sat Nov 17, 2012 3:26 am

Quoting tdscanuck (Reply 4):
On the 787 they actually refer to the system as an "electronic tailskid"...there is no physical skid.

I found the MMEL on MBF and found that the aircraft has a "Tail Strike Detection System". I thought that was the role the pilot filled with a Mark-10 Mechanic Eyeball as a back-up.
When seconds count...the police are minutes away.
 
imiakhtar
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RE: Landing Gear Length On The 787-10 Inadequate?

Sat Nov 17, 2012 4:52 am

Quoting fr8mech (Reply 5):
I thought that was the role the pilot filled with a Mark-10 Mechanic Eyeball as a back-up.

More often than not, pilots are the last people to know when a tail strike occurs. They're usually first informed by cabin crew or ATC.
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Max Q
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RE: Landing Gear Length On The 787-10 Inadequate?

Sat Nov 17, 2012 6:30 am

That's fine, but software and flight control laws can only get you so far. If you start to have take off performance penalties because you have to run up the v speeds to provide adequate tail clearance on rotation (like the B764) you are sacrificing performance and marketability.


I suspect the 787-10 will need a longer gear (like the 764 has)
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sunrisevalley
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RE: Landing Gear Length On The 787-10 Inadequate?

Sun Nov 18, 2012 10:09 pm

Quoting Max Q (Reply 7):
I suspect the 787-10 will need a longer gear (like the 764 has)

How about storage? Boeing has already had to play around with the upper surface of the bay to accomodate the 10" thicker gear of the 789.
 
roseflyer
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RE: Landing Gear Length On The 787-10 Inadequate?

Sun Nov 18, 2012 11:00 pm

The 787-10 may have semilevered gear so that the airplane rotated off the rear axle ( like the 77w). That gives an extra degree of rotation.
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AA737-823
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RE: Landing Gear Length On The 787-10 Inadequate?

Mon Nov 19, 2012 12:46 am

Quoting fr8mech (Reply 5):
I found the MMEL on MBF and found that the aircraft has a "Tail Strike Detection System". I thought that was the role the pilot filled with a Mark-10 Mechanic Eyeball as a back-up.

Did you click past the dialog box on MBF that says, "Information contained herein is Boeing proprietary, and by clicking 'continue', you agree to NOT SHARE IT WITH ANYBODY?" Cuz I think "anybody" would include a.net...
 
Max Q
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RE: Landing Gear Length On The 787-10 Inadequate?

Mon Nov 19, 2012 3:51 am

Quoting sunrisevalley (Reply 8):

How about storage? Boeing has already had to play around with the upper surface of the bay to accomodate the 10" thicker gear of the 789.

What do you mean 10'' thicker ?


Don't understand your statement.

Quoting Roseflyer (Reply 9):


The 787-10 may have semilevered gear so that the airplane rotated off the rear axle ( like the 77w). That gives an extra degree of rotation.

That would make a lot of sense, although they wouldn't get as big an advantage as the 7W with its very long six wheel bogie it would still help.


Its still not unprecedented for Boeing to put a taller gear on a stretch model though. They made the necessary modifications to extend the main landing gear by 18'' on the B767-400.


A side effect of that taller gear IMHO was that it made the 764 by far the best looking of all the 767 models !
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sunrisevalley
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RE: Landing Gear Length On The 787-10 Inadequate?

Mon Nov 19, 2012 12:48 pm

Quoting Max Q (Reply 11):
Don't understand your statement.

A poor choice of words, wider would be better. The outside of bogey to outside of bogey on the 789 is 10" more on the 788 The wheel spacing is wider around the centre line of the strut probably because of the bigger tire size.

Go to the Boeing ACAP sheets , find the 787 Brochure and look at P18.
 
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Stitch
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RE: Landing Gear Length On The 787-10 Inadequate?

Mon Nov 19, 2012 3:35 pm

Quoting sunrisevalley (Reply 8):
How about storage? Boeing has already had to play around with the upper surface of the bay to accomodate the 10" thicker gear of the 789.

They might be able to mount the strut farther out on the wing.

Honestly, though, I have the feeling Boeing always considered a longer 787 than the -9 and took that into account when designing the undercarriage. Also, the 787-10X's latest dimensions are a 5m stretch as opposed to the original 6m stretch so that might be a concession to rotation issues (stretch it 3m front and 2m aft).

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