Product Focus: Mission Data Recorders

By David Jensen | March 1, 2002
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Defining a mission data recorder (MDR) isn’t easy. How, for example, does an MDR differ from other recording devices on an aircraft?

When asked to define an MDR, Bruce McEwen, Smiths Aerospace’s director of business development and strategic planning, says, only half jokingly, "You respond to the RFP [request for proposals], and that is what it becomes." Others in the industry chuckle at McEwen’s definition but nod in agreement.

"Quite basically, a mission data recorder acquires data and stores it in an appropriate medium, " McEwen explains. The data can come from navigational and flight sensors, engine and airframe condition sensors, video cameras, voice recorders and flight instruments. It can include engine exceedances, fuel loads, weapons delivery, systems failures, overstressed components, and cockpit and cabin video–"anything the customer wants to record," says Jay Balakirsky, Smiths Aerospace Electronic Systems’ director of business development. And the data often is stored in solid state mass storage, either with battery-backed volatile memory (static random access memory, or SRAM) or nonvolatile memory–for example, FLASH memory. Other means of storage include PCMCIA cards, tape and hard disks.

But MDRs can do much more than record and store data. For example, they can play a significant role in the mission planning process. Indeed, MDRs for combat aircraft were developed, in large part, to eliminate the manual input of data in preparation for a mission. Pilots can initialize their avionics and mission systems by inputting into a laptop such data as waypoints, altimeter readings, terrain data, weapons information and target locations, and then relaying the information via a data transfer cartridge to the onboard MDR. With mass storage capability, the MDR also can accommodate the data bases for digital moving map software.

The recorded data in MDRs can be disseminated in various ways, as well. For example, broadband technology allows the radio transfer of mission data from MDRs in the U.S. Army’s AH-64 Apache helicopter and the Navy’s F-14 Tomcat to locations throughout the battle arena, according to Ron Burnett, national sales manager at TEAC America Inc. Commonly, however, the data is used for post-mission review. With today’s digital recorders, this usually involves having an encoder convert the data into a video format to create a simulated image for review on the PC screen.

The most advanced and comprehensive MDRs are installed in combat aircraft. One of the first solid state MDRs was developed for the F-16 by Fairchild Defense (now part of Smiths Aerospace).

Perhaps the most advanced MDR today is the one Smiths Aerospace developed for the U.S. Air Force’s new advanced tactical fighter, the F-22 Raptor. What makes it state of the art is its data transfer, mass memory and video recording capabilities. It can record up to four channels of video taken from, say, the panel displays and head-up display. Video and audio data can be recorded simultaneously via digital fiber optic and analog inputs. Its video data cartridge provides up to 30 gigabytes of memory capacity, a vast improvement over the 16-kilobyte capacity in early solid state MDRs.

And the memory capacity for MDRs keeps expanding. The Joint Strike Fighter mission data recorder will have 1 terabyte (1 trillion bytes, or 1,000 megabytes) of capacity, according to Burnett.

Early MDRs had only a single Mil-Std 1553B interface; however, today’s systems for combat aircraft will have multiple 1553 interfaces, multiple audio and video input interfaces, audio/video output, Ethernet, Fibre Channel and others, all in one box.

MDRs must be capable of offering still more capability, according to McEwen. "They must be upgradeable and modular, to add new functions and parameters." To accommodate upgrades, MDRs also must be developed so that "programs in the processors don’t interfere with each other," he adds.

The data recorded on a mission can serve various purposes. Post-mission analysis is common with combat aircraft. Using today’s data compression and animation technologies, the information from a solid state data cartridge can be presented on a personal computer for debriefing. The animated image can show instrumentation, weapons firing, even the view outside the aircraft, all synchronized, with recorded audio and video. Data from MDRs on more than one aircraft can be coordinated to present a more comprehensive picture of a combat mission. This type of flight review is particularly beneficial for pilot training.

While the pilot reviews the mission, maintenance personnel can use the recorded data from the MDR to review the aircraft’s condition, to see if there were engine exceedances, airframe wear or need for repair. "Aging aircraft make mission recorders more critical than ever," says McEwen.

The Canadian air force uses MDRs to equalize the wear on its aircraft. Called "level loading," this use of data allows the service to assure one aircraft is not used more extensively than others in the fleet.

Similarly, commerical carriers use digital flight data recorders to detect potential problems before they cause an accident or the need for costly maintenance. These quick access recorders–such as those made by Avionica, Teledyne Controls and other manufacturers–may be little more than match box size, yet they can store up to 400 hours of flight data. Some airlines apply these recorders to a flight operational quality assurance (FOQA) program. The focus of a FOQA program often is engine trend monitoring; however, the acquisition units also can present flight operations data–accelerations, airspeed, altitude, etc.–in animation on a PC screen. "With animation software, such as SimAuthor’s FlightViz, we can convert the data into simulated imagery [of the flight]," says Scott Moore, Avionica’s vice president of business development. "We can also marry the data with Jepp charts to enhance the imagery."

MDRs are used during aircraft test and evaluation, too. "Our line of data recorders is mainly used for test applications and instrumentation calculations for avionics bus data or telemetry data," says Chris Thacker, product manager of Merlin Engineering Works Inc., a subsidiary of TEAC. "The interfaces on our units are generic, so they can be used on many platforms."

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