Commercial, Embedded Avionics, Military

Snake Pit Superior

By by Frank Colucci | April 1, 2012
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An AH-1Z Cobra with the Aviation Combat Element of the 11th Marine Expeditionary Unit hovers above the USS Makin Island in the first shipboard deployment of the attack helicopter.   Photo courtesy U.S. Marine Corps

Aboard the amphibious assault ship Makin Island, the Bell AH-1Z completes the U.S. Marine Corps H-1 helicopter upgrade and gives the 11th Marine Expeditionary Unit a truly integrated light attack helicopter element. The four AH-1Z attack and three UH-1Y utility helicopters in their first combined sea deployment share avionics, dynamics, engines and structures to reduce supply, maintenance and training burdens. Just as important, the Northrop Grumman Integrated Avionics System (IAS) in both aircraft reduces crew workload and increases situational awareness with common hardware and software. The improvements are game-changers, especially in the tandem-seat attack helicopter that long kept pilots in the back with reduced visibility and co-pilot/gunners up front with reduced functionality. According to H-1 program manager Marine Col. Harry J. Hewson at the Naval Air Systems Command, “We’re finding in the AH-1Z there’s a role reversal. The front-seat pilot is doing all the flying. The rear-seat pilot is working the weapons.”

Identical front and rear cockpits in the Zulu Cobra are built around color Multi-Function Displays (MFD) with flight symbology, moving map, communications, weapons management and subsystems pages. Sidesticks with Hands-On-Collective-and-Stick (HOCAS) controls call up display pages and reduce pilot hand and eye movements for weapons selection, flare and chaff dispensing, radio frequency selection, and other functions. Hand-held mission grips enable either pilot to control the multi-sensor Target Sight System (TSS). Optimized Top Owl helmets show pilots targeting, navigation, and flight symbology, and slave the TSS to the user’s line-of-sight. One Marine pilot in the Zulu systems working group compared the legacy AH-1W SuperCobra to the new AH-1Z: “It’s like going from a VW Beetle to a new Lexus.” Current plans remanufacture 131 AH-1Ws into Zulu Cobras and build 58 new AH-1Zs through 2019.

Marine Cobras have evolved from the 9,500-lb AH-1G first delivered in February 1969 to the 18,500-lb AH-1Z declared operational in February 2011. The fourth-generation AH-1W introduced in 1986 today watches over Marines in Afghanistan with an Elbit-Kollsman Night Targeting System (NTS) and Hellfire and TOW missiles. Piecemeal developments nevertheless gave the Whiskey Cobra a high-workload cockpit.

“There were some fairly significant shortcomings in the AH-1W,” acknowledged Hewson. “The AH-1W was very much a federated cockpit. It had a lot of systems scabbed-on that did not interact with other systems on the aircraft. It was up to the pilot to turn things on and move things around.”

By one count, an AH-1W front-seater needed 52 switch actions to arm, select, program and launch a Hellfire missile. Different front and back cockpits complicated crew coordination. The Whiskey Cobra back-seater could fire weapons but could not program Hellfire laser frequencies or use the original day-only weapons sight. While the back-seater had no long-range visionics, the front-seater no Head-Up Display (HUD) to aim rockets. Either pilot in the Whiskey Cobra could use an antiquated mechanical helmet tracker to aim the Cobra gun, but one crew member had to be talked-on to targets spotted by the other.

Even with the Mil-Std-1553B databus on the AH-1W, the rudimentary fire control system could not use data generated elsewhere on the helicopter. “Information exchange between the navigation system and the fire control was limited,” observed Hewson.

Aircraft survivability suite likewise bridged stand-alone subsystems. With an APR-39 radar warning receiver display only in the aft cockpit, the front-seater who heard a warning had to ask the pilot for threat location.

“One of the big shortcomings of the AH-1W is that the front and rear cockpits are very, very different,” said Hewson. “One of the overarching concerns was to make them common.” He added, “It’s a training benefit to the pilot you only have to learn one cockpit.”

The AH-1Z first flew in 2000 but was not declared combat-ready until 2010. The Marines are expected to receive 189 AH-1Zs, with production running to 2019.
Photo courtesy Northrop Grumman

Marine squadrons also operate their close air support, anti-armor Cobras and utility/scout/Medevac Hueys side-by-side, but the AH-1W and aged UH-1N are totally different helicopters that complicate logistics in expeditionary squadrons. An H-1 Upgrade Engineering and Manufacturing Development (EMD) contract signed in November 1996 simultaneously addressed avionics and propulsion/drivetrain/dynamics disparities with the AH-1W(4BW) and UH-1N(4BN) now the AH-1Z and UH-1Y. Prime contractor Bell Helicopter chose Litton Guidance & Controls now Northrop Grumman Electronic Systems Navigation Division in Woodland Hills, Calif. to integrate the avionics of both aircraft.

Software Intensive

H-1 remanufacturing plans at the Bell plant in Amarillo, Texas, gave way to a mix of rebuilt and new Zulus and Yankees with 84 percent commonality in maintenance-significant components and 100 percent commonality in IAS software. Northrop Grumman Vice President for Situational Awareness Ike Song noted the same Operational Flight Program runs in both the AH-1Z and UH-1Y. “It wakes up and knows exactly what platform it is in.” Fleet savings in common H-1 software are significant. “When you have an upgrade in the Zulu, you have an upgrade in the Yankee and vice-versa,” observed Song. “A lot of people said that couldn’t be done because the Y and Z have different mission requirements.”

AH-1Z requirements emerged from working groups that interfaced government with industry. Input from Marines defined and refined the Zulu Cobra cockpit. The mission grip at each crew station, for example, controls sensors and weapons.

“This thing actually was loosely copied off a kid’s video game controller,” noted Hewson. However, early grips pulled-out on rails to rest in the user’s lap. “The reception was pretty cold on that.” The production cockpit has grips with coiled cords for Zulu pilots to stow the controller beside their seats and pop them out when needed. The cockpit Working Group continues to meet with representatives from the Marine Corps, NAVAIR, Bell, Northrop Grumman and the China Lake Weapons Software Support Activity.

H-1 avionics hot benches at China Lake, Woodland Hills and Amarillo validate IAS changes on real hardware. Despite the emphasis on Yankee-Zulu commonality, the slim Cobra airframe imposed special constraints on IAS hardware. “If you look at the Zulu and the Whisky, it is so space-constrained, if you want to add any functionally in black boxes, you’ve got to take something out,” Song said.

Northrop Grumman pursued a software-intensive solution for the H-1 Upgrade. Song explained, “We did a significant change from our previous federated architecture which added more black boxes. We went opposite of that where we have an open, integrated architecture instead of adding boxes, you add capability in software.” The AH-1W digital map from Harris in Melbourne, Fla., fills a 22-pound box. The Harris map on the AH-1Z is purely software. “Because the Zulu is so space-constrained, we also pushed back on our vendors and solution-providers to make sure we had a software-based solution.”

The attack helicopter architecture is shared by the Marine UH-1Y and the fixed-wing Navy E-2D. Most map functions, the display driver and the driver of the human-machine interface are carried over from one platform to the other. “All those modules are very similar,” Song explained. “Rather than re-use pieces of old software, we implemented standard software modules adaptable to multiple applications... It’s more of a partitioned software, so you don’t have ‘spaghetti code.”

Song added, “A lot of our competitors squeeze their commercial software into military applications. We only do defense work. The government owns all of our software.” The arrangement allows the owner to choose different vendors for upgrades. The Naval Aviation Center for Rotorcraft Advancement (NACRA) has half of an AH-1Z cockpit suite installed on its UH-1N test helicopters for rapid prototyping. “If they like what they see, we can get that into software on our Zulu and Yankee.”

Hardware and Helmets

The second-generation Northrop Grumman mission computer that hosts the modular software entered production in 2005, and introduced conduction cooling without fans to reduce weight and improve reliability. The FlightPro computer also mixed commercial and proprietary processors to maximize performance and manage life-cycle cost. Song noted that while commercial chips have a half-life of eight to 10 months, putting some processing in proprietary Field Programmable Gate Arrays stretches the half-life of the entire computer. “You don’t redesign every two to three years but every 10 to 15 years.”

Zulu/Yankee avionics, including aircraft survivability equipment, are fully integrated on ARINC 429 and Mil-Std-1553 databuses, plus an Ethernet bus for optical data. The Marines want 50 percent growth margin in processing power and databus throughput.

“I think there’s a heck of lot more than 50 percent. If you look at the bus, it’s greater than 80 percent,” Song said. “Today’s processor is so powerful, even when we put all this heavy-duty software on our mission computer, our bit-rate on the bus and processor is minimal”

The modular IAS accommodates different sensors and weapons on the AH-1Z and UH-1Y. NAVAIR and Bell chose Lockheed Martin Missiles and Fire Control in Orlando, Fla., to supply the AN/AAQ-30 Target Sight System (TSS) with mid-wave infrared, color TV, laser designator/rangefinder, laser spot tracker, and inertial measurement unit for the Hellfire-armed AH-1Z. The UH-1Y IAS is integrated with the AN/AAQ-22E BRITE Star II multi-sensor gimbal from FLIR Systems, of Wilsonville, Ore.

Both auto-tracking sensors show imagery on 8-inch by 6-inch Multifunction Displays from L-3 Communications Ruggedized Command and Control Solutions in San Diego. A 4.2-inch square Dual Function display shows standard pages or emergency flight symbology. “We’re using dumb displays,” explained Song. “All of the video processing is done at the mission computer. The flat, dumb display reduces the cost as well as the weight.” Bezel switches call up targeting, pilotage, navigation or systems pages with one or two button pushes. Song recalled, “One of the fundamental things we wanted to do was reduce the number of actual button-pushes.”

The Optimized Top Owl helmet gives Marine aviators a head-up display with day or night monocles. It is used in conjunction with standard Night Vision Goggles.
Photo courtesy U.S. Marine Corps.

The eyes-out Zulu cockpit also gives each crew member a day/night helmet display for targeting and pilotage data. The magnetically tracked helmets provide precise aiming cues and cues to show one pilot where the other is looking to enhance crew coordination. Bell selected the Thales Top Owl helmet flying on the Eurocopter Tiger as a low-risk Head-Up-Display. The binocular helmet had Image Intensifier (I2) cameras by the wearer’s ears and sent imagery to the aircraft computer to return a processed, annotated picture to a CRT visor.

“That was a great idea with a lot of opportunity because you’re processing the image and doing a lot of things to it. The problem was latency,” Hewson said. With the computer unable to keep up with rapid head movements, display imagery smeared. “It became a very high-risk issue. We decided that whole architecture had to be pitched.”

The second solution ported imagery from the sides of helmet straight to the visor without computer manipulation. Software overlaid HUD data on the visor day or night. “That was feasible in general flight conditions,” explained Hewson, “but in low-level terrain flight, taking off and landing in dark landing zones, and operating around the ship at night and in dark environments, you get hyperstereopsis the image is different from the design eye-point and creates weird illusions close to the ground.”

I2 imagery projected on a transparent visor was also prone to line-losses. “It was not the best image, particularly in low-light conditions. You really rely on the quality of the image projected there on dark nights.” Shortcomings in the refined helmet were uncovered by Marines during Operational Testing “Apparently other users don’t do the dark boat stuff and dark landing stuff that the Marines do,” noted Hewson.

Zulu testers reviewed helmet alternatives. “One-hundred percent, we concluded there is nothing in the world that is better for night vision than the current state-of-the-art Night Vision Goggles.”

The monocular Optimized Top Owl now in the fleet uses the magnetically tracked helmet and HUD processors, but trades the visor for a clip-on day monocle with HUD information. AN/AVS-9 goggles are used with a night monocle. Hewson added, “There’s some growth potential we’re talking about porting FLIR to the helmet.”

Other potential improvements focus on digital connectivity and streaming video to and from the Zulu. “That is in development right now,” said Hewson. “The most important thing for the Marines is down to the Forward Air Controlled on the ground with a ROVER video link. That really shortens the kill chain for the Cobra in any close air support engagements.”

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