REVIEW OF FAA’S FINAL MONITOR AID 

TOOL AT DENVER’S TERMINAL RADAR 

APPROACH CONTROL CENTER 

Federal Aviation Administration 

Report Number AV-2008-022 

Date Issued: January 25, 2008 
U.S. Department of 

Memorandum

Transportation 

Office of the Secretary 

of Transportation 

Office of Inspector General 

Subject: ACTION: Review of FAA’s Final Monitor Aid 

Tool at Denver’s Terminal Radar Approach 

Control Center 

Federal Aviation Administration 

Report Number AV-2008-022 

Date: January 25, 2008 

From: Lou Dixon 

Assistant Inspector General for 

 Aviation and Special Program Audits 

Reply to 

Attn. of: JA-10 

To: Acting Federal Aviation Administrator 

This report presents the results of our review of the safety and suitability of the 

Federal Aviation Administration’s (FAA) Final Monitor Aid (FMA) tool deployed 

at Denver’s Terminal Radar Approach Control Center (TRACON). We initiated 

our review in response to a hotline complaint. Our objective was to determine if 

the FMA at the Denver TRACON is safe, effective, and suitable for managing air 

traffic. The exhibit to this report details our review scope and methodology. 

FMA allows Denver’s air traffic controllers to visualize and precisely manage 

aircraft on triple, simultaneous, final approaches to the airport’s parallel runways 

during low-visibility conditions. Without FMA, triple, parallel approaches at 

Denver are prohibited when visibility is limited, and the maximum aircraft 

acceptance rate into the airport is reduced by 33 percent—from 96 aircraft 

landings per hour to just 64 per hour. 

The FMA tool at the Denver TRACON runs on a Standard Terminal Automation 

Replacement System (STARS) computer and display. To receive flight and radar 

data, the STARS FMA system requires STARS hardware to be connected in a 

hybrid configuration to Denver’s existing terminal automation system, the 

Common Automated Radar Terminal System (CARTS). 
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BACKGROUND 

During 2006 and early 2007, the STARS FMA system was tested at the Denver 

TRACON. Based on those tests, Denver officials concluded that the system was 

safe. The system was subsequently commissioned on February 28, 2007, 

concluding a lengthy installation and testing process. 

In 1996, STARS was the centerpiece of the Agency’s nationwide terminal 

automation modernization effort. However, FAA did not complete the nationwide 

STARS deployment primarily because of affordability concerns. Recognizing 

these concerns, we recommended in 2004 that FAA focus on replacing aging 

controller displays at Denver and three other large TRACONs and upgrading 

existing CARTS systems instead of deploying STARS.1

 As we noted in 

congressional testimony, replacing the aging displays is the most urgent issue 

facing terminal modernization.2

Subsequently, FAA decided to retain CARTS and is scheduled to replace aging 

displays in Denver in 2008. Once the new displays are installed on CARTS in 

2008, CARTS could be upgraded with FMA software. Once that upgrade is 

complete, there will be no benefit to keeping the STARS FMA workstations—

from both an operational and a maintenance perspective. 

RESULTS IN BRIEF 

We found no evidence that Denver’s new STARS FMA system, as currently 

configured and operating, is unsafe. It appears to be effectively performing the 

role for which it was designed. However, Denver’s STARS FMA solution 

requires two complete terminal automation systems, STARS and CARTS, to do 

the job of one. 

During testing in 2006, Denver’s STARS FMA system experienced problems 

related to its hybrid configuration that raised legitimate safety questions. While 

those safety issues were resolved, FAA’s use of two complete automation systems 

to provide Denver with FMA capability raises questions about the suitability and 

cost-effectiveness of the STARS FMA configuration compared with a singlesystem approach. For instance, annual TRACON maintenance costs for STARS 

FMA in 2006 were about $100,000, or over 12 times more than the approximately 

$8,100 spent maintaining Denver’s legacy FMA system. 

 

1

 OIG Report Number AV-2005-016, “Terminal Modernization: FAA Needs To Address Its Small, Medium, and 

Large Sites Based on Cost, Time, and Capability,” November 23, 2004. OIG reports and testimonies are available 

on our website: www.oig.dot.gov. 2

 OIG Testimony Number CC-2007-047, “Actions Needed To Reduce Risk With the Next Generation Air 

Transportation System,” May 9, 2007. 
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In 2008, FAA will install new controller displays and upgrade the CARTS 

automation system at Denver. These new displays will be able to present FMA 

radar and flight data to controllers, without using STARS. Therefore, when 

installing the new displays in Denver, FAA needs to determine whether it is more 

cost-effective to maintain both STARS and CARTS or integrate FMA software 

into one automation system. FAA should then implement the most suitable and 

cost-effective means of providing FMA capability at Denver and other locations. 

FINDINGS 

Denver’s STARS FMA Is Safe but Requires Two Complete Automation 

Systems To Provide FMA Capability 

CARTS and STARS are two completely different automation systems, developed 

by two different vendors. Because CARTS and STARS are separate systems, 

FAA had to develop a unique software interface to allow the two systems to 

exchange critical radar and flight data. However, this interface is so complex and 

sensitive that a disruption on the CARTS side can cause the loss of all critical 

flight data on the STARS FMA side. 

For example, on October 4, 2006, all critical flight data were lost from Denver’s 

STARS FMA displays during testing. This incident raised legitimate safety 

questions about the STARS FMA system, which was removed from testing for 

analysis. FAA subsequently developed a software interface patch, and the system 

re-entered testing on November 1, 2006. According to Denver TRACON 

officials, no additional malfunctions have occurred since testing resumed. 

After the STARS FMA system re-entered testing, we visited the Denver TRACON 

and watched the system operate. We interviewed local air traffic controllers, 

managers, and maintenance and technical personnel and found no evidence to 

indicate that the STARS FMA system is unsafe. The personnel we interviewed all 

generally supported the view that FMA on STARS appears to operate safely and 

perform the task for which it was designed. 

FAA Needs To Consider a More Integrated Approach To Deliver the 

FMA Capability at Denver 

The Denver TRACON relies on two systems to provide FMA services. However, 

this creates a complex configuration, which may not be the most suitable or 

cost-effective way to obtain FMA capabilities. This configuration requires air 

traffic controllers to be trained on both CARTS and STARS and FAA 

maintenance technicians to support both systems. 
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Maintaining a complete STARS automation system for the sole purpose of 

providing FMA also adds additional costs to the Denver TRACON’s operations. 

In 2006, annual maintenance costs for STARS at Denver were about $100,000 

versus only about $8,100 to support the legacy FMA system—an increase of more 

than 12 times. Further, although STARS at Denver is a complete radar automation 

system with associated STARS-only displays, Denver limits STARS to one role: 

enabling FMA. The Denver TRACON does not utilize any other STARS features. 

FAA personnel estimate that the FMA capability uses less than 5 percent of 

STARS capabilities. 

Instead of operating and maintaining two systems to provide FMA at Denver, 

FAA could simplify its approach by integrating FMA software directly into the 

CARTS automation system after replacing the aging CARTS displays in 2008. 

An integrated FMA approach for CARTS is feasible; it was prototyped and 

demonstrated to FAA officials in 2002. An integrated approach would also reduce 

costs for training controllers and maintenance support. Lastly, adopting an 

integrated FMA approach would eliminate the cost of separate STARS hardware 

and STARS-only displays, the connecting software interface from CARTS to 

STARS, and the cost to operate and support two systems. 

We discussed a CARTS integrated FMA approach with FAA’s Terminal 

Automation Program Office. The program manager was familiar with the 

integrated approach. He acknowledged that after the plan to fully deploy STARS 

changed, the unique situation at the Denver TRACON created a less efficient 

maintenance condition. The program manager also agreed that integrating the 

FMA capability into a single system would be technically feasible once the aging 

displays in Denver are replaced in 2008. 

Since those discussions, the program office began a cost-benefit analysis to 

determine if it would be cost-effective to integrate FMA into a single automation 

system after the aging displays are replaced in 2008. The cost-benefit analysis is 

not yet complete. The estimated cost to integrate FMA into multiple air traffic 

control facilities using CARTS, including Denver, is $2 million. However, FAA 

anticipates that this cost will be offset by the benefit of having to maintain only 

one terminal automation system that also provides FMA capability. 
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RECOMMENDATIONS 

We recommend that FAA determine whether it is more cost-effective to maintain 

both STARS and CARTS in Denver or integrate FMA software into one system 

once Denver’s aging displays are replaced in 2008. After taking this action, FAA 

needs to implement the most cost-effective means of providing FMA capability at 

Denver and other air traffic control facilities where FMA capability is justified. 

AGENCY COMMENTS AND OFFICE OF INSPECTOR GENERAL 

RESPONSE 

We discussed the results of our work with FAA managers at the Denver TRACON 

and the Terminal Automation Program Office at the Agency’s Headquarters in 

Washington, D.C. We also provided them with a discussion draft in December 

2007 and incorporated their comments where appropriate. FAA Headquarters and 

field office managers concurred with our findings, conclusions, and 

recommendations. They pointed out that actions are underway (an ongoing costbenefit analysis) to address our concerns. We believe that management attention 

will be needed to ensure follow-through by the Agency to identify and select the 

most cost-effective approach for providing FMA at Denver and other facilities. 

ACTIONS REQUIRED 

In accordance with DOT Order 8000.1C, we request that FAA formally respond to 

our recommendation within 30 calendar days. We are requesting that FAA 

provide us with target completion dates for completing the cost-benefit analysis 

and implementing the most cost-effective approach for providing FMA. FAA may 

propose alternative actions that it believes would resolve the issues presented in 

this report. 

We appreciate the courtesies and cooperation of FAA representatives during this 

review. If you have any questions or concerns about this report, please contact 

Matthew E. Hampton, Deputy Assistant Inspector General for Aviation and 

Special Program Audits, at 202-366-1987. 

# 

cc: Anthony Williams, ABU-100 

 Martin Gertel, M-1 
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EXHIBIT. SCOPE AND METHODOLOGY 

To accomplish our objective, we interviewed FAA managers from the Denver 

TRACON at the Northwest Mountain Regional Office in Renton, Washington. 

We reviewed FAA documents and records related to the Denver FMA system and 

its automation platform, STARS, as well as FMA operation, performance, and 

maintenance history. 

We visited the Denver facility and observed STARS FMA operations. We 

interviewed air traffic control and operational support personnel familiar with 

STARS and Denver’s existing automation system, CARTS. We also discussed the 

STARS FMA and CARTS systems with an FAA Headquarters official from the 

terminal automation program office responsible for managing the acquisition and 

installation of air traffic control equipment. We discussed Denver’s future 

replacement displays with a representative of FAA’s display contractor. We 

conducted this review between December 2006 and November 2007 in accordance 

with generally accepted Government Auditing Standards prescribed by the 

Comptroller General of the United States. 

Exhibit. Scope and Methodology