ElectroHydroStatic Actuators

[popcorn]

How big an effort is it to maintain the hydraulics system on legacy jets and what benefit from the Mx perspective does the F-35s EHSA tech provide? Do .he traditional systems operate at the same hydraulic pressure as the new kit or does the latter any performance,benefit in terms of moving control surfaces?

[spazsinbad]

ELECTROHYDROSTATIC ACTUATION SYSTEMS

http://www.parker.com/literature/Contro ... ochure.pdf (3.1Mb)

“Power-by-wire control that delivers less system weight, enhanced avionics integration, and reduced life-cycle costs.

Electrohydrostatic actuation (EHA) and electrical backup hydraulic actuation (EBHA) are power-by-wire systems that eliminate the need for central hydraulics. EHAs and EBHAs are self-contained hydraulic systems controlled by high-power electronics, which allows the use of traditional, proven hydraulic actuation configurations for fault tolerance.

The product of two decades of research, development, and flight-tested reliability, Parker EHAs offer significant advantages:

• Reduced system weight. This is due to the elimination of hydraulic distribution systems.

• Reduced power consumption. Power is used as required, yielding a more efficient system.

• Improved maintainability. Hydraulic disconnections between actuation equipment and the vehicle system are eliminated.”

[spazsinbad]

Perhaps related interest PDF (5.5Mb):

The Evolution of Electric Military Aircraft 29 July 2011 Dr. Mark T. Maybury Chief Scientist USAF

http://www.avweb.com/pdf/electric-aircr ... rcraft.pdf

[spazsinbad]

JSF/F-35 Pollution Prevention Activities ESTCP/SERDP DoD Metal Finishing Workshop 22-23 May 2006

http://www.asetsdefense.org/documents/W ... s-F-35.pdf (4.6Mb)

"• Lifetime Sealed Unit
• No Maintenance Required
Avoids Hydraulic Leaks and Clean Up"

[spazsinbad]

Shaping the F-35 Maintenance Approach - The View from Pax River 07/18/2011

http://www.sldinfo.com/shaping-the-f-35 ... -approach/

"...The Block 60 was the most advanced F-16 ever built. Avionics-wise, the airplane was called an F-16 because the airframe, basically, didn’t change.

They beefed it up in areas, but the biggest changes were the avionics packages, and being an avionics technician by trade I saw those every day. I see a lot of that similarity and beyond now in the F-35 because it’s even more advanced. Block 60 doesn’t compare in our world today to the F-35.

SLD: So what’s the difference between a Block 60-enabled F-16, which is the most advanced F-16, built today and an F-35 from this particular avionics point of view?

Paramore: The maintenance concept, when fully matured it is going to be something that we’ve never had the pleasure of before. F-22s, I know a little bit about, I have friends of mine that have been on the program and actually are maintainers in the field for the F-22. Those guys tell me about how easy their aircraft is actually from a maintenance perspective.

This is going to make it even easier from a maintenance perspective because of the way our maintenance concepts are set up on the F-35.

SLD: But at the end of the day, from your point of view, even before there is a fully matured maintenance regime, and the first batch of aircraft are delivered, how will the maintenance approach very, very different from a 16?

Paramore: On a F-16, for example, all your actuators are still hard-lined into the hydraulic system. The actuators on the F-35 are fully self-contained: four cannon plugs, some bolts, and it pops right out after you take your panels off.

On the F-16, you’d be four cannon plugs, eight bolts, two hydraulic lines, refuel or resetting the hydraulic systems, re-servicing those, bleeding and leaking them, and then doing the ops checks, not to mention if you had some kind of rigging you had to do for the actual actuator if it wasn’t just a straight swap, you’d had to go in and do all your rigging for that actuator. The F-35 system self-adjusts the flight controls, so once you go in and replace an actuator, you run auto-rig, and the system auto-rigs the actuator.

SLD: So, you get two immediate benefits. One is you’re talking a much shorter amount of time necessary to get the plane airborne, which gives you the second advantage which is you get a better sortie generation rate out of the same aircraft, better use out of the aircraft...."

LOTS more at the JUMP of course....

[spazsinbad]

More stuff than I care to read at 0200. But anyhoo...

Power-By-Wire May 1, 2001 James W. Ramsey

http://www.aviationtoday.com/av/militar ... 12671.html

"Will the Joint Strike Fighter be controlled in flight by an electro-hydrostatic system? A Lockheed Martin-lead team hopes it will. The Boeing team has another idea....

...Reducing Weight and Cost
The new flight control subsystems package includes a power-on-demand electrical system and electric actuation (rather than the traditional, large, heavy and difficult-to-maintain hydraulic actuation) of flight control surfaces. Lockheed Martin maintains that government studies show the new approach could deliver up to a 5% reduction in procurement costs, 3% in lower life-cycle costs, and a 6% decrease in gross takeoff weight.

"We found that the emergency and secondary power system is much simpler and cleaner if you go with the electric approach," says Eicke. "It enables a much smaller and simpler airplane."

He adds that it can reduce aircraft weight by as much as 700 pounds (315 kg), but not because the system itself is lighter. "We’re taking weight out of the hydraulic system, weight out of the secondary power system, and out of the thermal management system, because we’re not generating as much heat.

"But we’re offsetting it with a relatively more complex actuation system," Eicke adds. "If you don’t do the trade studies at the air vehicle level, you don’t see the benefits.

"We also are simplifying maintenance on the aircraft. If you have to replace an actuator, you don’t have to bleed the fluid systems and break the hydraulic connections, which can cause environmental concerns."..."

[neptune]

Weapon Bay door actuators; pneumatic or E-H? I think I've seen these cycled and they can move very fast??

[spazsinbad]

Goodrich is a Major Producer of Actuation Systems with one of the Most Diverse Capabilities in this Field. September, 2011

http://www.goodrich.com/gr-ext-templati ... ystems.pdf (33Kb)

"...Goodrich actuation is vital to the Lockheed Martin Lightning II Joint Strike Fighter (JSF) - the company provides the complete drive system for the JSF weapons bay door. The speed and precision of this system is critical to aircraft safety because the protective stealth properties of the F-35 are degraded when it deploys its weapons, making it more vulnerable to attack. The aircraft has two internal weapons bays, each with two doors that are opened by rotary geared actuators driven by a hydraulic motor. The system includes an electronic control unit, hydraulic motors, a power drive gearbox, multiple rotary geared actuators and door uplocks, and consists of about 70 separate parts of which 20 are actuators. Goodrich also provides actuators for the flight and propulsion system on the F-35B Short Take-Off Vertical Landing (STOVL) version. These flight critical systems move control surfaces as the aircraft transitions from horizontal to vertical flight and vice versa...."

[popcorn]

Thanks Spaz, informative stuff. This slide summed up the benefits quite nicely.

[marksengineer]

Irrespective of of whether the actuator has an integral pump or is supplied fluid the size of it is a function of pressure and load. Given the same load as you decrease your pressure you increase the piston diameter. Can't see where you would be able to decrease pressure all that much unless you like to see large bulges on the control surfaces. The plumbing losses aren't all that much.
Instead of two pumps on a circuit you now have at least one pump at every actuator. I can't tell from the photo but it may be that there are two pumps at every actuator. Does someone know? It will be interesting to see if the smaller pumps are as reliable as the larger ones. What it does do for you is limit failure to one actuator and not the entire aircraft.
In the industrial world integral electro-hydrastatic units have had mixed results. Typically they cost more.
All electrical actuators are prefered industrially for control response but they haven't of yet developed ones with the speed and power of hydraulic systems.

[archeman]

I am happy to see them starting to get banished, hydraulic systems give me the creeps.
Don't get me wrong, I respect the power they can deliver.
I always hated the feel of that stuff on my hands on a windy cold night, there was no good way to easily get it off until you could get yourself off the flightline. The fittings are unforgiving and the constant mess under the equipment in the aircraft is a sure fire hazard in combat as well as a pain to live with. Your supposed to clean up every single spill but that just doesn't happen (and they are always spilling). I remember countless nights where we would change out a pump that had failed for mysterious reasons and reconstruct the system only to find over and over again that air bubbles were still hiding somewhere in the system no matter how many times we would follow the bleed procedure. The gear would waver back and forth at detent like a college kid on spring break.

Thank you for your service hydraulic systems, you'll find your gold watch and retirement papers on the way out the door.
Good Day Sir

[spazsinbad]

Not being an engineer I have no idea what this chap is on aboot [CANUCK spellin'] however some of youse might get the gist...

Design and Characterization of a Dual Electro-Hydrostatic Actuator By Kevin Ronald McCullough January 2011
A Thesis Submitted to the School of Graduate Studies in Partial Fulfillment of the Requirements for the Degree of Master of Applied Science in the Department of Mechanical Engineering, McMaster University, Hamilton Canada

http://cmht.mcmaster.ca/docs/McCullough ... 202011.pdf (5.3Mb)

Abstract
“Actuation of flight surfaces in aircraft have evolved over the last century from systems using simple mechanical linkages actuated by the pilot to complex electronic systems that maneuver large loads and have some form of redundancy. The latest form of flight surface actuation uses Power-By-Wire (PBW) systems, which are modulated, lean and fault tolerant actuators embedded in the flight surface that require only the attachment of power and control wires. This research will focus on a specific form of PBW system called an Electro-Hydrostatic Actuator (EHA), which is seen on modern aircraft such as the Lockheed F-35 Lightning and the Airbus A380.

An EHA is a closed-loop form of hydraulic system which controls an actuator’s movement by routing fluid to it via a fixed-displacement pump attached to a servomotor. The two primary components of the EHA’s hydraulic circuit are a bi-directional external gear pump and an actuator, but the system incorporates an accumulator, a bi-directional relief valve, a by-pass valve and a series of check valves for full functionality. The minimal components and the closed-loop architecture lend itself to be lightweight, modular and independent of other hydraulic systems on an aircraft.

This research will focus on developing a design based on a dual EHA system used for the rudder of the F-35. The design objective is to reduce the comparative weight. The dual EHA allows for continued actuation of the airfoil in the event that one of the EHA’s malfunction. The design produced in this research incorporates a new inner-circuit which allowed the system to be 12% lighter than the F-35 rudder EHA. A prototype developed from this design was produced but was augmented with additional components that allow for simulation of fault conditions in the future. With a prototype produced several experiments were performed to determine the level of internal leakage and damping inside the system. Experiments showed that internal leakage increases linearly with the increase of back pressure on the pump and that the bulk of the leakage occurs at the pump itself. Experiments also showed that the damping in the system is non-linear and that it is best described by a LuGre friction model.

Black-box system identification techniques were applied to the EHA to determine piece-wise linear models. These trials showed that the non-linear friction as well as the seals in the actuator forced the system to have two major piece-wise linear regions. These experiments also showed that when the mean velocity of the actuator increases so does the system bandwidth.

Enclosed in this dissertation are details of the design of the dual EHA and the experimental results performed on it.”

[spazsinbad]

Some in the MOOG stuff here: http://www.moog.com/products/actuators- ... drostatic/

"Electrohydrostatic Actuators, often referred to as “power by wire,” are fully self contained actuation systems that combine design elements from electric and electrohydraulic actuation. They receive power from an electric source and transform an input command signal (usually electrical) into motion. They typically include a servomotor, hydraulic pump, accumulator and servoactuator."

http://www.moog.com/images/Products/Act ... iagram.jpg

[spazsinbad]

There is at least one thread on this F-35 forum about the Live Fire Testing with info from this and other magazines. Those links will follow. In the meantime...

Aircraft Survivability - Live Fire Test and Evaluation Magazine
Published by the Joint Aircraft Survivability Program Office SPRING 2010

http://www.bahdayton.com/surviac/asnews ... ring10.pdf (3.2Mb)

F-35 Live Fire Test: Full-Up Systems Level Testing by Charles Frankenberger 2010

"...The primary objective of 2AA:0001 LFT series is to evaluate the systems that support aircraft flight controls. This includes the electrical power system, the power and thermal management system, the vehicle systems network, and the flight control system itself. The testing will be conducted in a way that replicates the aircraft functions during a mission, from engine start, to wheels up, to ingress and egress, and return to base. Facility integration with the aircraft system to conduct each of these functions has proven to be quite the engineering challenge.

About the Aircraft
The 2AA:0001 aircraft is structurally non-representative of the final SDD aircraft design. It is, however, very representative from a systems perspective. Some of the features of the JSF air vehicle include a glass cockpit, an advanced fly-by-wire closed loop flight control system, 270 volts direct current (VDC) electrohydrostatic actuators (EHA) to drive control surfaces, an integrated power and thermal management system, and a 40,000-pound thrust-class F135 engine. EHAs provide the mechanical power to position the flight control surfaces. There is one EHA driving each flight control surface. For critical surfaces (Horizontal Tail and Flaperons), dual-tandem EHAs provide redundant actuation within a single line replaceable component....

...The VSIF, having the most hardware in the loop, is the most difficult to operate, and so was used only when necessary. Consequently, most of the test cases were conducted in the VIF; the VSIF was necessary in nine of the cases where real hardware was required, such as electrohydraulic actuators (EHA), electronic units (EU), and converter/
regulators (C/R.)

Figure 1 shows a functional diagram of the VSIF facility. The facility is equipped with dynamic electro-hydraulic actuator (EHA) load fixtures, drive stand, EPS, and cockpit rooms. Each room’s level of integration is controlled by the VSIF control room. The control room is separated into three areas for each integrated product team (IPT)—FCS, EPS, and HUA. The “core” of the control room layout is a cluster in the center of the room consisting of the Vehicle Management Computer (VMC) Engineering Test Station (VETS) and the Remote Input/Output (RIO) Engineering Test Station (RETS). In the center of this cluster is the VETS/RETS switch rack that allows the VSIF to switch from three standalone facilities to a single integrated facility...."
_______________

Some other threads on this forum links to this testing:

http://www.f-16.net/index.php?name=PNph ... c&p=221179
&
http://www.f-16.net/index.php?name=PNph ... c&p=204074

[spazsinbad]

'archeman' the A-4 Skyhawk family (with many other US / UK aircraft for sure) was notorious for oil and hydraulic leaks. In the hangar a drip tray was underneath at all times. In flight the oil/hydraulic leak streaks were most obvious and difficult to clean up on ground with the original dull paint schemes. Later high gloss paint schemes allowed the usual method of fixing the aircraft (hit offending part with a rubber hammer and wipe with a clean rag) more efficient.