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By Andrew Tilghman - Staff writer
Posted : Saturday Jan 24, 2009 7:09:46 EST
Navy Times

How well does the “G-suit” protect an aviator from the effects of high-speed turns in high-performance jets?

Naval aviation officials hope to tackle that question in a wide-ranging study of the most effective ways to help pilots push the limits of speed in tactical aircraft. At the heart of the study is an examination as to whether muscle-flexing and physical ability are more effective ways to battle the forces of gravity than a pressurized suit.

The study, commissioned in early January by the commander of Naval Air Forces, will feature a new round of research into G-forces and the best ways to counteract high-speed pressures that can abruptly drain blood from a pilot’s brain, causing lightheadedness, temporary vision loss or a blackout.

The latest research compiled by Naval Air Training Command from any number of organizations that conduct aeromedical studies suggests that the G-suit — a pressurized garment that inflates to prevent blood from rushing toward the lower body — is not the most critical element of G-force protection.

“For the past year and a half, we’ve been taking a hard look at the aeromedical research on G-tolerance and the performance of aviators,” said Rear Adm. Mark Guadagnini, chief of naval air training. “What it all indicates is that the biggest factors in G-tolerance and the ability of a pilot to perform are fitness levels, having been through centrifuge training and a good ‘anti-G-straining maneuver.’

“And notice that having a G-suit on was not one of those factors.”

Guadagnini has been scrutinizing the latest research following the fatal April 2007 crash of Blue Angels pilot Lt. Cmdr. Kevin Davis in Beaufort, S.C.

Investigators last year found Davis probably suffered a “grayout” while making a sharper-than-normal turn and then failing to take steps to prevent blood from rushing from his brain during the maneuver.

Blue Angels pilots do not wear the pressurized flight suits worn by fleet fighter pilots. That’s partly because the flight suit’s sudden inflation risks bumping the control stick while the pilots fly in close formation; any imprecise movement in such formations could be catastrophic.

Investigators into Davis’ death recommended that the Blue Angels consider developing a G-suit that could inflate without risk of bumping the control stick.

But the Blue Angels declined.

They detailed their reasons for doing so in September when applying for their annual waiver from fleet-wide rules requiring G-suits be worn by all F/A-18 Hornet and Super Hornet pilots.

Better ways to battle Gs
Guadagnini provided extensive research to Naval Air Forces as a part of that waiver application, suggesting that the best ways to prevent fatal accidents such as Davis’ included:

• Improving the anti-G straining maneuver, or “Hick maneuver,” in which a pilot breathes a certain way and tenses his lower muscles during intense G-forces to prevent blood from flowing downward.

• Enhancing fitness training to focus on the legs, abdominals and the torso.

• Improving simulator and centrifuge training to help pilots practice the timing and techniques of the anti-G strain maneuver. Specifically, technology in new training modules can coordinate G-force simulation with a pilot’s flight exercise.

After reviewing the waiver request and the attached research, Naval Air Forces commander Vice Adm. Thomas Kilcline said the analysis may be useful not only for the Blue Angels, but for the rest of the fleet. He formally ordered a review in early January.

“The tasking from the air boss is, ‘Let’s see what we can find that is out there, to take a look at the combination of equipment, training and fitness to see what is the best way to protect pilots from G-induced performance effects,’ ” Guadagnini said.

The G-suit provides pilots with an additional 1.5 Gs of protection. But the real threat — and the one that likely killed Davis in 2007 — is sharp spikes in G-force. Those can come on too quickly for the flight suit’s inflation mechanism to have a significant effect, Guadagnini said.

“The issue is the instantaneous Gs, the high-G onset. … The G-suit does not protect you against those, nor does any equipment that the Air Force uses,” Guadagnini said.

The review also will involve extensive research by Naval Air Systems Command and likely will last more than a year, Guadagnini said.

It may be the military’s largest review of G-force protection efforts in nearly 10 years. In 2000, the Air Force examined an alternative G-suit that used water rather than air to place pressure on the pilot’s legs and forced oxygen into the pilots lungs. That suit was not adopted for widespread use.

by Staff Writers
Washington (AFP) Jan 15, 2009
Space War

In a breakthrough that could signal a new era for human technology, US and Chinese researchers announced Thursday they are a step closer to creating an invisibility shield.

In a development made possible by advances in complex mathematical algorithms, engineers at Duke University, North Carolina were able to create what they call “metamaterials.”

These materials can “guide electromagnetic waves around an object, only to have them emerge on the other side as if they had passed through an empty volume of space,” according to the team, whose work was published in the January 16 edition of the journal Science.

The cloaking phenomenon is similar to mirages seen at a distance on a hot day, according to senior researcher David R. Smith.

“You see what looks like water hovering over the road, but it is in reality a reflection from the sky,” Smith said.

“In that example, the mirage you see is cloaking the road below. In effect, we are creating an engineered mirage with this latest cloak design.”

The team, who were backed by the US Air Force Office of Scientific Research and the National Science Foundation of China among others, worked off their 2006 prototype that proved the project’s feasibility.

But Smith said their latest cloak is far superior to the original design, Smith said.

“The new device can cloak a much wider spectrum of waves — nearly limitless — and will scale far more easily to infrared and visible light,” he said.

“The approach we used should help us expand and improve our abilities to cloak different types of waves.”

The breakthrough has the potential of advancing numerous technologies that already exist, and ideas that have yet to be devised.

“By eliminating the effects of obstructions, cloaking devices could improve wireless communications, or acoustic cloaks could serve as protective shields, preventing the penetration of vibrations, sound or seismic waves,” said the team.

The cloak, measuring 20 inches (50.8 centimeters) by four inches (10 centimeters) and less than an inch (2.5 centimeter) high, is constructed with 10,000 fiberglass pieces arranged in parallel rows, 6,000 of which are unique.

The unique algorithms that can affect electromagnetic waves determined the shape and placement of each piece, the team indicated.

In a tight spot, you need zoom to maneuver.

By Jim Mathews
Air & Space Magazine, July 01, 2008

Remember the scene in the movie Top Gun when Navy pilot Pete “Maverick” Mitchell gets the upper hand on his instructors by slowing down, pulling up the nose of his F-14 Tomcat, and watching his opponent fly right by? The idea was to get a quick, unexpected position behind the bad guy, putting Maverick (played by Tom Cruise) and his trusty sidekick Goose into place to win the Engagement.

Real fighter pilots will tell you that what Maverick does is a showoff move that bleeds off so much energy that you’re vulnerable to getting shot down yourself. What a pilot really needs is a way to quickly get in the right position to fire at the enemy. Today’s most maneuverable fighters use thrust vectoring, which can make a jet turn faster and more tightly.

Powered by Pratt & Whitney F119 turbofans, each with 35,000 pounds of thrust, the F-22A—the Air Force’s newest fighter—sports a nozzle that can direct exhaust thrust up or down as much as 24 degrees.

The advantage to pilots is superior low-speed and high angle-of-attack maneuverability, compared to conventional-thrust aircraft, says Second Lieutenant Aaron Hoke, a propulsion engineer on the U.S. Air Force team that manages the Lockheed Martin F-22A Raptor program at Wright-Patterson Air Force Base in Ohio.

Continue reading ‘How Things Work: Thrust Vectoring’ »

By Joe Pappalardo

Air & Space Magazine, August 01, 2007

These days, fighter pilots’ helmets are nearly as complex as their airplanes. And with good reason: If the helmets can’t tell where the pilot is looking, many of the airplane’s systems, including weapon targeting, are useless.

The folks at Vision Systems International of San Jose, California, who have designed advanced U.S. military helmets for the F-15, F-16, and F/A-18, make their living at the nexus between man and machine. VSI’s flagship program is the Joint Helmet Mounted Cueing System. It uses a magnetic field in the cockpit to sense the orientation of the helmet, then feeds information on the current line-of-sight to the aircraft’s flight computer. VSI’s helmet has an accuracy of about four milliradians, an angular measure commonly used in the world of shooting and targeting. One milliradian equates to one one-thousandth the distance to the target. So if the target is 1,000 feet away, you’d be accurate to within a foot.

Determining where a pilot is looking by tracking eye movement is a much taller order. “You would not believe some of the human factor issues you have to overcome to have a successful eye tracker,” says Louis Taddeo, VSI marketing director. “Although we have research projects into eye tracking, it is a very difficult task both from a technical [standpoint] and the physiology.”

So for now, VSI uses helmet position to achieve that four-milliradian accuracy. Pilots need only turn their heads to aim their weapons, even during high-G maneuvers, freeing their hands for other tasks.

The head-up displays (HUDs) currently used in fighter aircraft are sophisticated, but they have a single, fixed point of view. Future helmets will include virtual displays projected across the visor, where the pilot can see information and targeting prompts. The F-35 Lightning II helmets due to enter service in 2012 will offer what Taddeo calls “extreme off-axis targeting.” Instead of having to turn the airplane toward the target to frame it in a fixed-view HUD, the pilot will be able to see targets that are off-axis, or not in the direction of flight. Like its predecessors, the Lighting II helmet will use magnetic head tracking, but VSI says the accuracy will be greater, courtesy of software upgrades that combine head position with eye location and data from the HUD.

Lockheed Martin test pilot Jon Beesley took the new helmet for a test drive last April in the first pre-production F-35. It was the first time a pilot in a tactical fighter had flown without a HUD in at least three decades. Expect more flights if the reviews are good.

Got a nagging question we can help you answer? Send an email to Joe Pappalardo at needtoknow@airspacemag.com

Some keep flying for decades, while others end up on the scrap heap.

By Rebecca Maksel

airspacemag.com, March 01, 2008

Source:  Air & Space Magazine

A reader asks: “Two articles in the Feb./Mar. 2007 issue of Air & Space raised a question. One was about the last flying examples of a number of classic planes (”And Then There Was One”). The other was about newer jetliners, too old to fly, being chopped up to make skateboards and soft drink cans (”We Recycle“). It struck me as odd that the old planes are still airworthy, while the jetliners are fit only for the scrap heap. Why can some planes seemingly keep flying forever, while other, newer ones are already used up?”

An aircraft’s lifespan is measured not in years but in pressurization cycles. Each time an aircraft is pressurized during flight, its fuselage and wings are stressed. Both are made of large, plate-like parts connected with fasteners and rivets, and over time, cracks develop around the fastener holes due to metal fatigue.

“Aircraft lifespan is established by the manufacturer,” explains the Federal Aviation Administration’s John Petrakis, “and is usually based on takeoff and landing cycles. The fuselage is most susceptible to fatigue, but the wings are too, especially on short hauls where an aircraft goes through pressurization cycles every day.” Aircraft used on longer flights experience fewer pressurization cycles, and can last more than 20 years. “There are 747s out there that are 25 or 30 years old,” says Petrakis.

How do airlines determine if metal fatigue has developed in their passenger-liners? Bob Eastin, an FAA specialist on aircraft fatigue, says, “[Airlines] are really relying on the manufacturer’s maintenance programs. The manufacturers design the aircraft to be trouble-free for a certain period of time. There are maintenance actions to preclude any catastrophic failures, but that’s not to say that the aircraft might not [experience metal fatigue] before those times…. When you get to a certain point [in the aircraft’s lifespan], you need to inspect or replace certain parts.”

Nondestructive evaluation (NDE) inspections are used both during production (to ensure that components start out free of defects) and during an aircraft’s service life to detect cracks as small as 0.04 inch. Inspectors might, for example, take a close look at fastener holes located at the wing and spar junction.

We contacted NDE experts Deborah Hopkins of Lawrence Berkeley National Laboratory and Guillaume Neau, of Bercli, LLC, who together answered in an e-mail: “The challenge in developing an easier and less expensive inspection strategy is to design a technique that can be used from the skin side (of the wing), that does not require removal of the fastener, and that provides the same or better resolution than the conventional method of removing the fastener.” Not having to remove the fastener is a big money-saver.

One commonly used method of NDE is ultrasonic phased-array testing, which analyzes the echoes from ultrasonic waves to reveal imperfections inside a material. By using several ultrasonic beams instead of just one, then varying the time delays between the beams, inspectors can look inside a material at different locations and depths, thereby determining the size and shape of any defects.

At present, million-dollar robotic inspection systems equipped with phased arrays are being used to inspect wings and composite fuselages for large commercial aircraft and jetfighters before they fly. “Most aircraft manufacturers and service providers—Dassault Aviation, Airbus, and Boeing, for instance—ensure the quality of their production with large-scale non-destructive testing systems,” Neau wrote in an e-mail. And while a million dollars may sound like a lot, “when put in perspective, the number is not so large,” he says. “If manufacturers discover a problem after assembly, the cost of dismantling and redoing the part or the scrappage waste is much higher than the inspection cost.”

Got a nagging question we can help you answer? Send an email to Rebecca Maksel at rmaksel@si.edu