Sunday, December 1, 2002
Product Focus: Aircraft Recorders in Transition
In anticipation of new regulations, standards bodies are preparing for aircraft recorders that store not only voice and data but also digital data link messages. As aircraft/air traffic control voice communications evolve to the data link environment, recording these messages to and from the airplane will be necessary for safety purposes. Technical experts also are working on a standard approach to recording cockpit images.
The European Organization for Civil Aviation Equipment (EUROCAE) is developing an equipment standard that will address data link and cockpit image recording, as well as audio and flight data recording parameters. A document, ED-112, covering these areas, is expected by March 2003, providing a baseline for future regulation.
The Airlines Electronic Engineering Committee (AEEC), meanwhile, is addressing data link recording issues in a draft supplement 3 to its cockpit voice recorder (CVR) standard, ARINC 757, expected in February 2003. AEEC plans to address image recording issues in ARINC Characteristic 767, expected in about two years.
The U.S. National Transportation Safety Board (NTSB) has recommended that aircraft have data link recording capability. A recent update to the International Civil Aviation Organization’s (ICAO’s) Annex 6 has called for newly certificated aircraft using data link communications–and required to carry a CVR–to record "all" data link communications to and from an aircraft after Jan. 1, 2005.
According to a Joint Aviation Authorities (JAA) interpretation of the ICAO standard, however, aircraft probably won’t need to record aeronautical administrative communications, automatic dependent surveillance (ADS) communications between aircraft, and data transmissions in response to secondary surveillance radar interrogations.
But data link recording requirements are still "somewhat vague," says Duncan Schofield, Honeywell’s manager of flight recorder engineering. "To size the memory, we need to have some predictability on how much we have to record." Exactly what information goes over the selected ARINC 429 data link pipe and how it is sent have not been finally determined.
Smiths Aerospace, however, contends that, given the limited bandwidth of the data link channel, the company’s own combi recorder should have enough extra memory capacity to accommodate data link recording capacity requirements.
There is interest in combination cockpit voice and data recorders (CVDRs) that would be able to record flight data, cockpit voice and data link messages in a single unit. NTSB has recommended the use of two "combi" recorders per aircraft, one as close to the cockpit as possible and the other as far aft as possible. EUROCAE’s ED-112 document echoes this sentiment and ARINC’s draft Project Paper 767 takes a similar line.
It is considered unlikely that the Federal Aviation Administration (FAA) will require the airlines to install combi recorders, but the agency may require dual-redundant CVR and FDR capability–so carriers may have to install two CVRs and two FDRs or two combis. The perceived benefits in logistics (a single part number) and improved airplane dispatchability have raised interest in the combination approach.
FedEx Sets Pace
FedEx Express is the first major carrier to take the combi approach, replacing older tape-based CVRs with the newer technology. The air cargo company had installed combination voice flight data recorders (CVFDRs), produced by Smiths Aerospace, on its MD-11 airplanes and on 75 percent of its Airbus fleet, as of October 2002, giving it dual data recording capability. FedEx plans to begin installing combis on Boeing 727s by year-end. It has specified that its future Airbus 380s will come with redundant combination recorders–one in the nose and one in the tail, says Robert Swanson, a FedEx project engineer.
Because of these equipment changes, FedEx had petitioned the FAA Flight Standards Service for minimum equipment list (MEL) relief. The company requested that airlines with dual-redundant flight data recording capability–in excess of FAA requirements–could extend the time for repair or replacement of one data recorder, if it should become inoperable. According to the proposal, repairs could be deferred from the current three flight days to as many as 10 flight days. FedEx expected that the proposal would be adopted at the next meeting of FAA’s AFS 260 group, scheduled for November 2002, if no objections emerged.
ARINC’s draft supplement to the 757 standard completes the definition of the data link recording interface, says Dan Martinec, secretary of AEEC’s DFDR (digital flight data recorder) Subcommittee. Supplement 3 also will align fault and status indications for combi data recording with its existing ARINC 747 DFDR standard, making it possible–with the use of an adaptor–to install combi recorders in the FDR slot. (Combis already can be installed in CVR slots.)
The alignment of data recording interfaces requires the reassignment of some existing pins, Martinec says. Software changes and some rewiring also will be required, but industry hopes FAA will consider these adjustments as minor, allowing a speedy approval process. The changes that would be introduced by 757-3 are optional at this point. Currently, data link messages are recorded on the ground, not in the air.
Honeywell, L-3 Communications and Smiths Aerospace make combination voice/data recorders compliant with the current ARINC 757-2 specification. Honeywell has a combi digital voice data recorder (DVDR) in a certification program with Embraer for the new ERJ 170. Each aircraft will carry two Honeywell combis, according to Schofield. The company expects technical standard order (TSO) approval in January 2003. This "757-2-plus" recorder would require only minor changes to meet the latest revision of the ARINC spec, Schofield says. L-3 Communications also has a combi cockpit voice and data recorder with the ARINC 757 connector.
Smiths provides a Model 3257A1 CVFDR and Model 3874C control unit, which have been certified and installed on Boeing MD-11, B727, Airbus 300, A310, and Bell 412 and 430 aircraft, says Bill Peterson, Smiths’ lead systems engineer, civil recorders. The company also is targeting the Dassault Falcon 900B and the Canadian military’s C-130 aircraft. Smiths’ anticipated 757-3-compliant product will implement digital data link recording and comply fully with forthcoming equipment standard, ED-112.
Some technical issues still remain with data link recording. A new requirement in ED-112 calls for a time stamp of less than 250 milliseconds, or less than 0.25 second, for synchronizing all aircraft recording. ARINC’s 619 data link spec–"ACARS Protocols for Avionic End Systems"–provides for a 1-second time reference. A supplement to ARINC 619 is expected to add the new specification this year. Data link recording also will have implications for the design of communicatons management units (CMUs), which receive, process and forward data link messages.
FedEx’s MD-11s are forecast to have data link recording capability in the future by upgrading the current ARINC 757-2-compliant combis to the ARINC 757-3 configuration. FedEx hopes to begin installing CMUs some time in 2003 and to implement the data link recording function some time in 2004.
EUROCAE also is addressing cockpit image recording in ED-112, a document that envisions simultaneously recording data, voice, data link messages and cockpit images in a single unit. In response to the EUROCAE effort, AEEC’s DFDR Subcommittee is developing Project Paper 767, "Enhanced Airborne Flight Recording System," which also focuses on interfaces for image recording. When ARINC 767 is published, however, "we expect that all facets of form, fit and function will be defined exactly as would be necessary to install on the airplane," Martinec says.
Although cockpit image recording is not currently required, it could be mandated as a means of determining instrument state, pilot hand movements, data link message displays, head-up display status, and possibly cargo and cabin area images presented to the flight crew, for accident investigation.
AEEC’s DFDR Subcommittee has provided feedback to EUROCAE during the ED-112 development process. The DFDR group, for example, recommended limiting image color depth and the frame recording rate, inputs which were accepted.
The recording of data-intensive image files will require larger memory banks but also greater bandwidth to the recorder. Use of 10BaseT, 100BaseT, or even 1000BaseT Ethernet links, integrated services digital network (ISDN) and optical fiber has been discussed.
The high-speed link could connect an "information acquisition unit"–gathering voice, data, data link and image information–and the recorder. Another option, however, would be to provide a direct link between the "acquisition function" of an integrated avionics suite and the recorder, Martinec says. The latter option would have implications for data acquisition systems. Ethernet would provide more than enough bandwidth, but presents issues of its own. For example, "there is a finite limit to how far copper wire can operate reliably with 100BaseT Ethernet," Martinec says. "It’s probably near the limit, if the recorder is installed in a very large airplane."
Even after these issues are worked out, the use of image recording would require a new airplane architecture, Schofield says. "Until somebody decides to build an airplane with those extensive changes, we probably won’t pursue it." It would be difficult to retrofit image recording on existing aircraft, to find places for the cameras, adds an avionics engineer. "You need to design it into the airplane in advance."
Aerospace Monitoring & Systems Ltd. www.ams.co.za
Avionica Inc www.avionica.com
Kaman Aerospace Corp., Memory Systems Division www.raymond-engrg.com
L-3 Communications www.l3com.com
Meggitt Avionics www.meggitt-avionics.co.uk
Muirhead Avionics www.muirheadaerospace.com
Penny And Giles www.pgcontrols.com
Photo-Sonics Inc www.photosonics.com
SFIM Inc www.sfiminc.com
Smiths Aerospace www.smiths-aerospace.com
SPACEAGE Control Inc www.spaceagecontrol.com
Spirent Systems www.spirent-systems.com
TEAC America Inc www.teac.com
TEAM Inc www.team-avionics.com
Teledyne Controls www.teledyne-controls.com
Thales Avionics www.thalesgroup.com
Universal Avionics Systems Corp. www.universalavionics.com