britjap
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A380 & 787 Landing Gear Question

Thu Nov 01, 2007 8:36 am

Not so much a question about the landing gear itself, rather the actuation systems used for gear extention/retraction.

I know that Airbus really tried to develop and push the MEA concept forward for the A380. Due to its very large size the benefits are particularly significant. But what I want to know is has this led to EHA or EMA actuators being used for the landing gear? Same question goes for the 787 as well.

If the answer is no, then are there any aircraft using these actuators for the landing gear?

If the answer to that one is no as well then what do you think will be the first aircraft to utilise this technology?

Feel free to mention if you know of other areas where these actuators are used on an aircraft, but I am specifically asking about landing gear actuation.

Regards
 
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jetmech
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RE: A380 & 787 Landing Gear Question

Thu Nov 01, 2007 9:47 am

Quoting BritJap (Thread starter):

I think the electro / hydraulic actuators are used as a backup on flight controls only.

Regards, JetMech
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
FWI747
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RE: A380 & 787 Landing Gear Question

Thu Nov 01, 2007 11:13 am

AFAIK, EHA on the A380 have been chosen for the back-up braking system (named Full Brake by Wire) and as a for the steering control system of the nose landing gear.
For what I've understood EHA are providing back-up or an momentary increase of power for the primary flight control system (elevator, ruder, ailerons) when needed.

Regards, David
 
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HAWK21M
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RE: A380 & 787 Landing Gear Question

Thu Nov 01, 2007 12:55 pm

Quoting FWI747 (Reply 2):
named Full Brake by Wire

Any data on this.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
FWI747
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RE: A380 & 787 Landing Gear Question

Thu Nov 01, 2007 1:20 pm

 
SEPilot
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RE: A380 & 787 Landing Gear Question

Thu Nov 01, 2007 4:48 pm

When I was involved in the design of the world's first totally computerized grinding machine it the late 1970's one of our design goals was the elimination of hydraulics. This was accomplished initially, but as the machine evolved in the 80's it was discovered that when heavy loads have to be moved smoothly, there really is no substitute for hydraulics. Electro-mechanical operators end up being more expensive, more complex, heavier, bulkier, and less reliable than hydraulics, even with all the drawbacks that hydraulics bring. Granted, electro-mechanical actuators have improved greatly since then, but I suspect that they still aren't competitive with hydraulics for things like landing gear actuators. When you see excavators and backhoes start using electro-mechanical instead of hydraulic actuators then I believe that aircraft landing gear actuators will follow.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
FWI747
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RE: A380 & 787 Landing Gear Question

Thu Nov 01, 2007 5:23 pm

Quoting SEPilot (Reply 5):
Electro-mechanical operators end up being more expensive, more complex, heavier, bulkier, and less reliable than hydraulics, even with all the drawbacks that hydraulics bring. Granted, electro-mechanical actuators have improved greatly since then, but I suspect that they still aren't competitive with hydraulics for things like landing gear actuators. When you see excavators and backhoes start using electro-mechanical instead of hydraulic actuators then I believe that aircraft landing gear actuators will follow.

 checkmark 

However, I recall that NASA tested an F16XL equipped with that type of actuator some years ago. Can anyone out there confirm it ?
And on a side note what type of operator does the F35 use ? EHA ?

David
 
SEPilot
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RE: A380 & 787 Landing Gear Question

Thu Nov 01, 2007 6:10 pm

Quoting FWI747 (Reply 6):
However, I recall that NASA tested an F16XL equipped with that type of actuator some years ago.

NASA often does things long before they become viable for commercial applications; sometimes they actually work and lead to widespread use. Other times they make expensive toys. It would not surprise me if eventually electro-mechanical actuators do replace hydraulics in aircraft landing gear; it also would not surprise me if they never do.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
FWI747
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RE: A380 & 787 Landing Gear Question

Thu Nov 01, 2007 6:22 pm

Quoting SEPilot (Reply 7):
NASA often does things long before they become viable for commercial applications; sometimes they actually work and lead to widespread use. Other times they make expensive toys

 yes 
 
KELPkid
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RE: A380 & 787 Landing Gear Question

Thu Nov 01, 2007 6:39 pm

Some aircraft use electric gear actuation already:

View Large View Medium
Click here for bigger photo!

Photo © Bruce Leibowitz



Heck, some even use manual gear actuation (the infamous "Johnson Bar" gear):

View Large View Medium
Click here for bigger photo!

Photo © Terry Shepherd


EDIT: It should also be added that many GA types use an interesting hybrid system for the landing gear, with an electric motor driving the hydraulic pump. I guess that's for the GA types where the hydraulic system is doing nothing more than raising and/or lowering the landing gear...

[Edited 2007-11-01 11:41:01]
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
 
SEPilot
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RE: A380 & 787 Landing Gear Question

Thu Nov 01, 2007 8:03 pm

Quoting KELPkid (Reply 9):


EDIT: It should also be added that many GA types use an interesting hybrid system for the landing gear, with an electric motor driving the hydraulic pump. I guess that's for the GA types where the hydraulic system is doing nothing more than raising and/or lowering the landing gear...

This is the electro-hydraulic system talked about. Yes, many GA aircraft use different methods, but the fact that it is possible to do manually (i.e. the Johnson bar) indicates that the force required is really quite low. How big do you think the Johnson bar would have to be on an A380?
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
KELPkid
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RE: A380 & 787 Landing Gear Question

Thu Nov 01, 2007 8:52 pm

Quoting SEPilot (Reply 10):
How big do you think the Johnson bar would have to be on an A380?

I would imagine that it would extend from the lower passenger deck to the upper, and require at least 10 people to activate...

"And we here at Singapore Airlines would like to remind those seated in the first section on the upper deck to reivew the safety card, as you may be called upon to help in the event of a landing gear malfunction..." Big grin
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
 
SEPilot
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RE: A380 & 787 Landing Gear Question

Thu Nov 01, 2007 9:11 pm

Quoting KELPkid (Reply 11):

"And we here at Singapore Airlines would like to remind those seated in the first section on the upper deck to reivew the safety card, as you may be called upon to help in the event of a landing gear malfunction..."

 bigthumbsup 
Sounds like fun; think they'll implement it?
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
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BreninTW
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RE: A380 & 787 Landing Gear Question

Fri Nov 02, 2007 1:24 am

Quoting KELPkid (Reply 11):
would like to remind those seated in the first section on the upper deck to reivew the safety card, as you may be called upon to help in the event of a landing gear malfunction

It would be more a case of "would like to remind those passengers seated at the back that they might be called to walk to First Class to assist ..."

Heaven help the F/A who asks a F/C pax to do anything other than sleep!
 
FWI747
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RE: A380 & 787 Landing Gear Question

Fri Nov 02, 2007 9:06 am

Quoting Brenintw (Reply 13):
Heaven help the F/A who asks a F/C pax to do anything other than sleep!

So true !  rotfl 
 
RebelDJ
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RE: A380 & 787 Landing Gear Question

Fri Nov 09, 2007 12:31 pm

Quoting FWI747 (Reply 2):
AFAIK, EHA on the A380 have been chosen for the back-up braking system (named Full Brake by Wire) and as a for the steering control system of the nose landing gear.

Not quite right. The braking system on the A380 has two parts - the "power" and the "control". The brakes are powered by the two hydraulic circuits on the a/c and they are controlled (activated) by wires linking them to the centralised computers on the a/c.

The steering system is a conventional Airbus hydraulic push me - pull you opposed hydraulic actuators, again controlled by the centralised computer system.

Neither braking nor steering use EHA. They do use a Local ElectroHydraulic Generating System (LEHGS) which is described on the Messier Bugatti link you posted - but this is a standby reservoir/pump system - not an EHA.

The only systems on the A380 using EHA/EBHA are the flight controls (which is why the a/c can meet it's safety objectives with just the two hydraulic systems).

The 787 on the other hand is the first a/c to use electric brakes - i.e. no hydraulics.
 
FWI747
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RE: A380 & 787 Landing Gear Question

Fri Nov 09, 2007 5:21 pm

Quoting RebelDJ (Reply 15):
The only systems on the A380 using EHA/EBHA are the flight controls (which is why the a/c can meet it's safety objectives with just the two hydraulic systems).

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Thanks for this clarification  Smile

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