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Written by Sabc   
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General Description
Development
System Features
Operational Issues
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The F-15E uses the Joint Helmet-Mounted Cueing System (JHMCS) which is a multi-role system that enhances pilot situational awareness and provides head-out control of aircraft targeting systems and sensors - and as such it is a force multiplier for the Strike Eagle.

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General Description

In an air-to-air role, the JHMCS, combined with the AIM-9X missile, form the High-Off-BoreSight ( HOBS) system. HOBS is an airborne weapon-interception system that enables pilots to accurately direct or "cue" onboard weapons against enemy aircraft merely by pointing their heads at the targets to guide the weapons, while performing high-G aircraft maneuvers that may be required to complete the attack.

In an air-to-ground role, the JHMCS is used in conjunction with targeting sensors (radar, FLIR, etc.) and "smart weapons" to accurately and precisely attack surface targets. It allows F-15E aircrew to provide unparalleled support to ground troops in the CAS environment.

jhmcs_pilot

In all roles, the JHMCS provides the pilot with aircraft performance, targeting, weaponry and threat warning information, regardless of where the pilot is looking, significantly enhancing pilot situation awareness throughout the mission. In a dual-seat aircraft, each crewmember can wear a JHMCS helmet, perform operations independent of each other, and have continuous awareness of where the other crewmember is looking.

Development

JHMCS was developed by Vision Systems International ( VSI) based on the Israeli DASH III and the Kaiser Agile Eye HMD systems. VSI is a joint venture company formed by Rockwell Collins, Elbit and Kaiser Electronics. VSI has been awarded the original development contract in 1996. The US Department of Defense ( DoD) has awarded an $86m contract for first full-rate production lot of JHMCS to Boeing in June 2004. The JHMCS is deployed operationally now on over 2,500 F-15, F-16, and F/A-18 aircraft worldwide, including several international air forces that employ these aircraft. System integration to the F-15E Strike Eagle was done by Boeing. Note that although JHMCS integration to different aircraft types require different solutions, 95% of the system remains common to all platforms.

In May 2012 Boeing has awarded a contract to VSI to supply JHMCS for the US Navy and Air Force aircraft. Under the $32m contract, VSI will deliver JHMCS, including spares, technical support and ground support equipment to Boeing in support of the foreign military sales ( FMS) to Finland, Australia, Belgium, Canada and Switzerland. The JHMCS will be used onboard the Boeing-built F-15 and F/A-18, as well as on General Dynamics-built F-16 aircraft. Deliveries under this contract are scheduled to begin in 2012 and will continue throughout 2013.

System Features

Unlike one of its predecessor, the DASH system, which is integrated into the helmet itself, JHMCS is a clip-on attachment unit, which can be latched into position with one hand during flight (see photo below). It fits to modified HGU-55/P, HGU-56/P or HGU-68/P helmets and it features a newer, faster digital processing package than that used in the DASH. The overall design is more advanced than DASH, based on the collective knowledge accumulated by Elbit and Kaiser through the years.

jhmcs_display_assembly

The JHMCS has a magnetic helmet-mounted tracker (like DASH), which determines where the pilot's head is pointed, combined with a miniature display system that projects information onto the pilot's visor. A magnetic transmitter unit is fixed to the pilot’s seat and a magnetic field probe is mounted on the helmet to determine where the helmet is actually pointing. A Helmet Vehicle Interface ( HVI) interacts with the aircraft system bus to provide signal generation for the helmet display. The head tracker and visor display together act as a targeting device that can aim sensors and weapons.

To obtain a variety of information and sensor-based data pilots can refer to the visual display on the inside of the helmet while remaining in a "heads-up" or "outside" position during combat; this eliminates the break in visual contact that occurs when they look away to check the display readouts in the cockpit. This significantly improves pilot situational awareness during all mission elements. The visor display presents monochrome calligraphic symbology (stroke display) with information like airspeed, altitude, G-load, AoA, target range, targeting cues, threat warnings, etc. JHMCS provides support for raster scanned imagery to display FLIR or IRST pictures for night operations and provides collimated symbology and imagery to the pilot. JHMCS symbology covers a 20 degree field of view for the right eye, with an 18 mm exit pupil (see photo below).

To aim and fire a missile, pilots simply move their heads to align a targeting cross (placed in the middle of the projected imagery) with the target and press a switch on the flight controls to direct and fire a weapon.

jhmcs_display_symbology

To attack a ground target, the pilot can acquire the target with a sensor and note it's location on the helmet display. Alternatively, the pilot can use the helmet display to cue sensors and weapons to a visually detected ground target. Note that precision ordnance cannot be released based on JHMCS targeting alone, the system is not accurate enough for this. However it can be used to direct the aircraft's much more precise targeting systems (targeting pod) towards the target the pilot is looking at. This way the tedious "soda-straw" search limited to a display image generated by the narrow field of view targeting system can be shortened significatly. With JHMCS, target acquisition can follow a much quicker "look, sharpen, shoot" process.

The system can be used without requiring the aircraft to be maneuvered, significantly reducing the time needed to prosecute an attack, which also minimizes the time spent in the threat environment.

Since targets may be located at high-off-boresight line-of-sight locations in relation to the shooter, the system delivers a short-range intercept envelope that is significantly larger than any other air-to-air weapon in use. When combined with the AIM-9X missile, JHMCS allows effective target designation up to 80 degrees either side of the aircraft's nose.

The JHMCS display assembly requires two cable connections: a high voltage power cable for operation and a data cable for information exchange with the host aircraft. Unlike in DASH the high voltage power supply is not embedded in the helmet, it feeds up via an umbilical, through a quick disconnect inline high coltage rated connector.

When used in conjunction with a datalink, the system permits handoff of visually detected targets from one aircraft to another, with the second aircraft receiving visual cueing to the target.

jhmcs_side_view

JHMCS provides low-weight, optimized center of gravity and in-flight replaceable modules to enhance operational performance – including the ability to be reconfigured in-flight to meet night vision requirements. For this latter purpose, an attachment is provided to allow the NVG package to be clipped on during flight. Integration with NVG was a key requirement during the development program.

The system features a small built-in camera which records the targeting display during mission. This feature allows detailed and accurate post-mission briefing.

As part of a complete flight testing, the JHMCS system underwent ejection tests as well. It needed special design and solution to ensure that the extra weight of the helmet display assembly doesn't cause neck or spine injuries to the pilot during ejection.

Operational Issues

Since it is used on different aircraft, the shape of the dashboard of the given aircraft type and model can be programmed into the system. The system knows where the pilot is looking and it immediately clears the visor from projected information when the pilot is looking "down" or inside the cockpit to read conventional instruments (or the HUD in the F-15E for example). Likewise, since pupil positions relative to the visor vary from pilot to pilot, the system should be programmed for the individual pilot before the mission, otherwise correct aiming would not be possible. For this purpose, pilot specific anatomic data (pupil distance for example) are measured and stored to be downloaded into the system if needed.

JHMCS is integrated into the HOTAS system of the F-15E, resulting in very smooth operations and control - at the cost of aircrew having to re-learn modified HOTAS functions again. The first unit using the JHMCS in real combat environment will most probably be the 336th "Rocketeers" (as of 3rd Sept, 2010) who just began their combat tour in Afghanistan at the end of August 2010.

When wearing helmets, pilots can turn their head approximately 60 degrees from side to side of the aircraft's bore line. Since new generation missiles (i.e. AIM-9X) feature off-boresight capabilities of more than 60 degrees, the pilot's limited range of head movement would limit the use of these weapons. To eliminate this limitation, the JHMCS system utilizes an "up-look" aiming reference (see figure below). That is two up-look reticles provide higher off-boresight cueing capability by allowing pilots to cue the missile with their peripheral vision. Thus, they can utilize the full capability of missile technology and successfully employ weapons beyond 60 degrees off boresight.

jhmcs_up_look_reticle

JHMCS senses the direction the helmet is pointing at. The helmet can be shifted slightly on the pilot's head due to high-G maneovering if the helmet is fitted poorly. This results in targeting errors, which can seriously hinder the effectiveness of the cueing system. A misalignment as little as 2 degrees practically makes aiming impossible. For this reason, JHMCS's center of gravity has been optimized for high-G maneuvering.

Studies proved that pilots simply cannot hold their head steady (thus cannot aim properly) during high-G maneuvers or during aircraft buffeting. Aircraft buffeting occurs when the aircraft performs on the edges of its flight envelope during high AoA or when the aircraft is flying in turbulent air at low altitudes - this latter especially applies to F-15E in the CAS environment. For this reason, JHMCS features interface supression to smooth out inadvertent pilot head movements during high-G maneuvering and in areas of aircraft buffeting.

Flying with JHMCS increases the potential for spatial disorientation as well as task saturation. Most fighter pilots are used to flying with HUD information, which is always in the same place relative to the airplane, but flying with “HUD-like” displays on the visor can initially be disorienting because information is now located wherever they happen to be looking at the time. The problem is compounded at night due to the general lack of either a horizon or visual cues. Furthermore, having to keep up with aircraft parameters such as altitude, heading, and airspeed displayed directly in front of the right eye while attempting to employ and monitor weapons during dogfighting can quickly become overwhelming to pilots. To help lessen the danger of helmet displays contributing to this sort of task saturation, designers have enabled a HOTAS function so that pilots can blank the display if it becomes distracting in the tactical environment.

Sources

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Last Updated on Friday, 11 May 2012
 


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JHMCS
Sep 05 2010 06:46:20
weasel1962, thanks for the inspiration!
#209

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