About six months ago, someone–either a customer or an aircraft manufacturer–queried Rockwell Collins about a runway with a displaced threshold in a Pro Line FMS database. The airport databases in FMSs used in the Pro Line 4 and 21 avionics suites provide total runway length but not available landing distance (runway length less displaced threshold or usable length).

When the FMS is used to calculate landing performance, there is no provision for the pilot to alter the length of the runway by subtracting the displaced threshold. Rockwell Collins has since set about adding usable runway length to its FMS databases and plans to incorporate this feature in software updates accompanying a WAAS upgrade available late next year.

Rockwell Collins isn’t the only avionics manufacturer that designed FMSs without available landing distance. Some Honeywell FMSs include usable runway length, while others do not, according to a spokeswoman. Garmin’s G1000 system displays total runway length but not information about displaced thresholds. Universal Avionics’ FMSs have incorporated displaced thresholds and shown pilots usable runway length for many years, according to Dan Reida, director of worldwide marketing.

The question of whether FMS/nav system databases include information about displaced thresholds came to AIN’s attention after we ran an article in the July issue about the Southwest Airlines runway overrun accident at Chicago Midway Airport on Dec. 8, 2005 (“FAA changes landing distance rules for commercial operators,” page 1). The article focused on the FAA’s proposed policy to require Part 91K (fractional), 135, 121 and 125 operators to apply a 15-percent safety margin to calculated landing distance, to ensure that there is always enough room to stop given existing conditions, aircraft performance and equipment.

In the article, we based calculations of the landing performance of the 737 on the total length of Midway’s Runway 31C. Two alert readers pointed out that 31C has a 696-foot displaced threshold, and one added that the database in his Challenger 604’s Rockwell Collins FMS-6000 does not account for the displaced threshold. As a result, we contacted avionics manufacturers to find out more about the information that is included in their airport databases.

Project Under Way
Rockwell Collins told AIN it had already been working on updating its FMS databases, prompted by the customer or OEM query mentioned above. “After looking into this,” said Galen Kyes, FMS product manager, “we found out we’re not using the displaced threshold; we never implemented it.”

Jeppesen, which provides the database to many avionics manufacturers, has included displaced threshold information for many years, according to a spokesman. “Our database is coded per the industry-standard Arinc 424 coding standards,”
he said. “When we get source data that gives us this information, we’ll code the displaced threshold coordinates, so avionics manufacturers could then figure out available landing distance. How the manufacturers use that information is up to them.”

Upgrading an FMS to include the displaced threshold information isn’t a big deal, said Rockwell Collins’ Kyes. “To add this one change is a fairly minor cost, just a couple of changes and release the software.” Rockwell Collins, however, is adding the available landing distance information at the same time as a major upgrade that includes WAAS/SBAS (wide-area augmentation system/satellite-based augmentation system).

The upgrade’s availability will depend on whether the aircraft OEM decides to certify the WAAS upgrade, he said. If a business case can’t be made to entice operators to pay for a major upgrade that includes WAAS and the displaced-threshold information, operators will have to continue calculating usable runway length manually. “It is good to get [usable runway length] in the FMS,” Kyes said, “but with tens of thousands of aircraft out there, people are going to have to deal with it for a long time to come operationally.”

Both Garmin and Honeywell declined to provide information about whether they plan to add usable runway length data to their FMS or nav system databases.
“This type of information is not currently available on the G1000, but that doesn’t mean that it won’t be in the future,” wrote a Garmin spokeswoman in an e-mail.
“We continually look at new features and services for our FMS products,” wrote Honeywell’s spokeswoman. “At this time there are no specific product plans we can discuss related to the question.”