From Fokkers chasing Sopwith Camels over the muddy trenches of Flanders, to Phantom versus MiG dogfights over Hanoi, fighter aircraft combat has boiled down to getting your opponent in your gunsight while staying out of his.

Weapons changed from machine guns to cannon to air-to-air guided missiles, but the principle remained the same: Get the enemy in front of you and keep him there until he is reduced to his component parts.

But what if a pilot glimpsed an enemy aircraft that was to his left or right, or above or below his forward line-of-sight? His eyes could roam the sky, but his weapons mostly fired forward; so lining up a shot meant maneuvering to get the enemy in front of him (hence how dogfighting got its name).

What's been true for nearly a century of aerial warfare is true no longer, thanks to two pieces of revolutionary technology.

First is the helmet-mounted sight, a targeting system that projects crosshairs directly onto the helmet visor, allowing pilots to lock weapons regardless of the direction he is looking in. Then there are the weapons that respond to this novel cueing system - off-boresight missiles that can engage targets at extreme angles away from an aircraft's axis of advance.

Now a pilot engaged in high-G maneuvers doesn't have to maneuver his aircraft to get an equally gyrating opponent in front of him - and his situational awareness is enhanced by an ability to release weapons without looking down at an instrument panel.

Such a devastating combination of helmet and missile - smacking of Superman's laser vision capability - might have given U.S. pilots a lethal advantage during the Cold War, had they had it. But the Russians actually were first to use - albeit in crude, 1980s form - the helmet-mounted sight. Not long afterward, however, the Israelis, predictably, were able to vastly improve on the Russian model for their own uses.

American Pilots Disadvantaged

It's been U.S. aircraft that have lacked this capability for nearly two decades as they faced MiG-29s with helmet-mounted sights and R-73 Archer short-range, air-to-air missiles - which NATO has dubbed the AA-11 - a lethal heat-seeker reportedly able to lock on to targets 45 to 60 degrees off-boresight.

With Israel exporting their DASH [Display and Sight Helmet System] helmet-mounted sights and Python off-boresight missiles, American pilots have been at a disadvantage in any close-range dogfight where an enemy could engage them asynchronously but U.S. pilots could not. Better training and better equipment have more than compensated for this, but no fighter pilot wants to give an opponent any edge. The last thing he wants is a fair fight.

Not a moment too soon comes the Joint Helmet Mounted Cueing System (JHMCS), which its makers claim will give U.S. pilots the best helmet in the world.

"It really resolves a deficiency relative to foreign capabilities, either the MiG-29 or even capabilities the Israelis have developed and exported around the world," said Terry Kasten, JHMCS program manager at Wright-Patterson Air Force Base in Dayton, OH. "A potential adversary is going to be at a distinct advantage to a U.S. pilot without a helmet-mounted cueing system and an AIM-9X missile in an air-to-air engagement."

The JHMCS is designed to be the eyes of the AIM-9X, a high off-boresight version of the Sidewinder heat-seekers that trace their pedigree back to the 1950s.

The helmet also works with other air-to-air missiles as well as a variety of bombs and precision-guided munitions (PGMs). And the JHMCS has already finished operational testing for the F-15 and F/A-18E/F, and is in the midst of developmental tests for the F-16 that should be complete by the middle of 2003, according to Steve Winkler, the Boeing JHMCS project manager in St. Louis.

There is also a development contract to fit the JHMCS into the F/A-18C/D, with developmental testing soon to begin and operational testing slated for 2003.

Kasten said pilots welcome the JHMCS, and not just because it gives them an edge in a dogfight. "The feedback we're getting is that the pilots absolutely love it. They love it for the air-to-air capability, the air-to-ground capability and the enhanced situational awareness. They fly it on every mission, even when they're flying cross-country. They don't have to go heads-down and look at their gauges."

Israeli Technology a Key

The JHMCS draws heavily on the Israeli DASH helmet from Elbit Systems. It is being developed with Boeing as the prime integrator, along with Vision Systems International, a San Jose, California-based joint venture of Elbit and Kaiser Electronics (part of Rockwell Collins). Lockheed Martin is handling integration for the F-16.

Each JHMCS costs about $250,000, including support equipment and spares, with development costs for the project totaling about $65 million, according to Kasten.

The decision to enter full-scale production or not will come in September.

Kasten estimates that full production will mean approximately 1,800 helmet systems for the Department of Defense (DoD). But foreign military sales may prove to be equally lucrative, with interest in the JHMCS already expressed by Denmark, Switzerland, and other European states, as well as Australia which wants to upgrade the effectiveness of its F/A-18s. "If I were going to take a guess, I would say foreign sales would double the 2,000-unit domestic production requirement," Winkler said.

The JHMCS joint program office already has three initial production contracts:

• A contract in mid-2000 for 36 helmet systems plus spares for F/A-18E/F Block 24 aircraft.
• A 2001 contract for 137 helmets plus spares for  Block 25 F/A-18E/Fs as well as a limited number F-15s and domestic and Greek Air Force F-16s.
• In March of this year, an order for domestic F-15s, F-16s and F/A-18s that should ultimately total 200 systems.

The F-16 order comes before its operational tests are completed, but Winkler says that because JHMCS has worked well with other aircraft, this shouldn't be a problem for the Air Force. "From the F-16 perspective, they're very confident, because the subsystem itself is common across the F-15, F-16 and F/A-18."

One Size Fits All 

In fact, a one-size-fits-all approach is one of the prime attractions of the JHCMS. The same components are used for each aircraft, except for the length of the cable needed to plug the helmet into the aircraft's wiring.

"You can take them out of one aircraft and put them in another aircraft. Take it out of an F-15 and put it in an F-16, and it works fine," Winkler said.

Each JHMCS unit is comprised of a helmet shell, a helmet display unit on top of the helmet that projects cueing information on the visor, and an electronics unit that calculates the line of sight in whichever direction the pilot is looking. From the back of the helmet is an interface cable that plugs into the aircraft's wiring at hip level.

The electronics unit, the brains of the unit, uses a magnetic tracking system to calculate line of sight. Inside the cockpit is a transmitter that emits a magnetic field throughout the cockpit (each cockpit must first be magnetically mapped to calibrate the field). In the helmet is a receiver with three coils to measure changes in the X-, Y- and Z-axes of the pilot's head.

As the pilot scans the airspace, his head moves into a different part of the magnetic field, which is measured by the electronics unit. The electronics unit also generates the display information for projection onto the pilot's visor.

Although the United States wasn't the swiftest in the race for a helmet-mounted sight, JHMCS managers say their product is the best. Kasten rates the Israeli helmet as more capable than its Russian equivalent, and, in turn, JHCMS as more capable than DASH.

"We have double the accuracy of any other helmet system out there, including the next best, which would be the Israeli DASH," Kasten added.

For example, the JHMCS will have interchangeable day and night modules unlike the DASH 4, the latest version of the Israeli helmet, according to Louis Taddeo, director of business development for Visions Systems International.

Another feature unique to JHMCS is "uplook cursors," said Boeing's Winkler. These are targeting crosses that are displayed at "eyeball gimble limits," when the pilot's eyes are traversing as high and to the left or right as his eyes muscles will allow. By flipping a switch, a U.S. pilot in a super-close, canopy-to-canopy deathmatch gains an extra 30 degrees of cueing range when he can't crane his neck any further.

HOBS Capability 90 Degrees

Most importantly, the JHMCS is designed to use the AIM-9X's high off-boresight seeker (HOBS) capability, which allows the heat-seeking missile to acquire targets far to the sides of the aircraft.

Winkler describes the Russian R-73/AA-11 Archer as a medium-boresight missile that can lock on to targets at angles of, say, 60 degrees on either side of the aircraft's axis of advance. He refused to disclose the AIM-9X's acquisition angle, but he did say that a HOBS missile might acquire targets out to 90 degrees off centerline.

Indeed, the limitation of JHMCS appears to be the weapons it is slaved to rather than the helmet itself. The helmet can look in any direction, including over the shoulder. Whether a missile could acquire an over-the-shoulder target is another matter.

"The weapon or sensor is the limiting factor," Winkler said. The JHMCS has been tested successfully with earlier versions of the Sidewinder such as the AIM-9L, as well as the AMRAAM radar-guided missile. In addition, the helmet has a camera that records the targeting display on videocassette for post-mission debriefing, a feature also found on the DASH 4.

Beyond sheer lethality, the JHMCS has another feature sure to please pilots with a keen sense of self-preservation. The helmet is the only one of its kind that has been ejection-tested, Kasten said.

That's no minor matter considering the Helmet Display Unit is a mass sitting on top of the helmet, which means extra mass on a pilot's head when he blasts out of his cockpit at high speed. A heavier helmet means more chance of neck injuries, and JHMCS managers said ejection testing was one of the hardest parts of the project.

"We are the only ejection-qualified helmet system in the world," said Kasten. "Other helmet systems have gone through tower-testing and wind-blasting, but we've gone through a complete sled test program, so we view our system as the safest out there." 

Air-to-air combat is what the JHMCS was designed for, but it's in the air-to-ground role that it may really shine.

The helmet has been successfully used with air-to-ground weapons from an F/A-18, including Mark 82 and 84 iron bombs, Joint Direct Attack Munitions (JDAMs), Mavericks and laser-guided bombs. Winkler is certain that other aircraft will also use it for ground strikes. "We anticipate that once the F-16 community start flying in earnest and getting assets out in the field, they're going to come to the same revelation that the air-to-ground utility is equally, if not more, important than air-to-air."

Cueing System PGM Launches Coming?

To be precise, the JHMCS has not yet been used to directly launch precision-guided munitions. "The accuracy requirements levied on us were not such that we needed to be so precise," Winkler said. But the helmet-mounted sight can be used to slew narrow-focus sensors, such as FLIR (Forward-Looking Infrared) systems.

Once he uses the helmet to get a general fix on the target, the pilot can use his head-down displays to precisely align his sensors and then lock and launch precision-guided munitions.

The principle is the same as the air-to-air mode," said Winkler. "You're telling the aircraft the line-of-sight that you're looking at. It knows the exact angles that you're looking at, whether they're up or down." 

The extra seconds this saved harried pilots are priceless; acquiring targets through the narrow "soda-straw" view of a FLIR isn't fun when the targets are flashing past at 500 miles per hour.

"Before, if you were going to pop up over a hill, you'd be using your targeting pod and your FLIR to zero in, and that might take nominally 30 seconds for an operator to find what he's looking for with that soda straw searching approach," said Winkler. "Whereas if you fly up over that same hill, you look down and cue it with your helmet system, and five seconds later you've sweetened it up. So you've gone from 30 seconds to five."

There is no doubt that helmet-mounted sights will get better. Already under development for the JHMCS is a night module that projects the display on a dark visor instead of a clear one, thus making the display easier to read. On the other hand, the night module lacks the capability of night vision goggles; pilots can wear ANVS 49 night vision goggles and the helmet, but they sacrifice the helmet's display functions. To remedy this, the Air Force is working on Panoramic Night Vision Goggles designed to work with the JHMCS.

Kasten predicts that future versions of the JHMCS will have integrated day/night capabilities and an accuracy quotient double that of the current model. "It will be such that you can essentially throw away the Head-Up Display and look at a target on the ground, like we can do with JCMHS, but immediately release a PGM. We can do this with JCHMS today, but it's not going to be a very accurate cue. You could have accuracy [margins of error] of hundreds of feet."

HUDs to Disappear

Doing away with the Head-Up Display (HUD) opens a world of possibilities for aircraft designers. No HUD means a smaller, lighter cockpit, which in turn means that future aircraft could be designed around a helmet-mounted sight.

So it's no surprise that the Joint Strike Fighter (JSF) will have no HUD but will have its own special helmet. Details of the next-generation helmet are sketchy and classified at this point, with design just underway, but a few prototypes have been created, according to Taddeo. Vision Systems International is working on both the new helmet as well as the JHMCS.

Taddeo said the next-generation helmet will have a wide field of view, binocular display with digital image sources and integrated night vision situational awareness. It will also be able to display all the data that a HUD does.

With the next generation helmet at least five years away, should foreign customers wait for it and skip the JHMCS?

No, said Taddeo. Older aircraft can use the next generation helmet, but not without significant upgrade of their avionics. More important, the design of the helmet will be defined by the requirements of the JSF, so if the aircraft is delayed, so will the helmet.

"JHMCS is a proven, available system that offers graceful expansion as new technology comes on line," Taddeo added.

For now, what counts is that U.S. pilots will soon be looking at their opponents in a whole new way. And they'll be able to return home to tell the tale.