BritJap From Japan, joined Aug 2006, 250 posts, RR: 2 Posted (5 years 7 months 3 weeks 2 days 2 hours ago) and read 8159 times:
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.
FWI747 From France, joined Jul 2007, 70 posts, RR: 0 Reply 2, posted (5 years 7 months 3 weeks 1 day 23 hours ago) and read 8116 times:
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.
SEPilot From United States of America, joined Dec 2006, 6306 posts, RR: 39 Reply 5, posted (5 years 7 months 3 weeks 1 day 18 hours ago) and read 8009 times:
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 From France, joined Jul 2007, 70 posts, RR: 0 Reply 6, posted (5 years 7 months 3 weeks 1 day 17 hours ago) and read 7995 times:
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.
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 ?
SEPilot From United States of America, joined Dec 2006, 6306 posts, RR: 39 Reply 7, posted (5 years 7 months 3 weeks 1 day 16 hours ago) and read 7968 times:
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 From France, joined Jul 2007, 70 posts, RR: 0 Reply 8, posted (5 years 7 months 3 weeks 1 day 16 hours ago) and read 7961 times:
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
KELPkid From United States of America, joined Nov 2005, 5962 posts, RR: 4 Reply 9, posted (5 years 7 months 3 weeks 1 day 16 hours ago) and read 7954 times:
Some aircraft use electric gear actuation already:
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 From United States of America, joined Dec 2006, 6306 posts, RR: 39 Reply 10, posted (5 years 7 months 3 weeks 1 day 14 hours ago) and read 7911 times:
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 From United States of America, joined Nov 2005, 5962 posts, RR: 4 Reply 11, posted (5 years 7 months 3 weeks 1 day 14 hours ago) and read 7892 times:
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..."
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
SEPilot From United States of America, joined Dec 2006, 6306 posts, RR: 39 Reply 12, posted (5 years 7 months 3 weeks 1 day 13 hours ago) and read 7885 times:
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..."
Sounds like fun; think they'll implement it?
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
Brenintw From Taiwan, joined Jul 2006, 1470 posts, RR: 1 Reply 13, posted (5 years 7 months 3 weeks 1 day 9 hours ago) and read 7825 times:
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!
I'm tired of the A vs. B sniping. Neither make planes that shed wings randomly!
RebelDJ From United Kingdom, joined May 2007, 105 posts, RR: 0 Reply 15, posted (5 years 7 months 2 weeks 22 hours ago) and read 7437 times:
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 From France, joined Jul 2007, 70 posts, RR: 0 Reply 16, posted (5 years 7 months 2 weeks 17 hours ago) and read 7383 times:
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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