Flight Validation Toolset Helps Get New Flight Paths Off the Ground Quickly and Safely

August 2010
Topics: Air Traffic Management, Air Navigation, Avionics
With the help of a MITRE-developed Flight Validation Toolset, airlines, airports, and FAA-authorized companies now have a low-cost method for measuring obstacle heights around runways.
air trafic control screen

Flight paths in and out of busy airports are dictated by precise sets of guidelines. These flight paths, also called "procedures," ensure that aircraft avoid obstacles and other aircraft. Thousands of such flight procedures are currently in use worldwide. Now, advanced navigation capabilities and other technologies allow new procedures to be developed that will reduce flight times, save fuel, and reduce noise—making air travel more efficient and environmentally friendly.

The introduction of enhanced flight procedures is a significant element of the Next Generation Air Transportation System, or NextGen. (NextGen is the Federal Aviation Administration's plan to modernize the National Airspace System.) To encourage development of the procedures, the FAA recently began allowing airlines and FAA-authorized companies to create and validate their own approach and departure instrument flight procedures.

Once an organization develops a new flight procedure, however, the FAA must (literally) clear it for take-off. The FAA currently uses a survey method to demonstrate that the new procedure safely avoids any obstacles such as cell towers, buildings, and trees. Unfortunately, getting through the traditional measuring process can be time-consuming and costly because it requires certified surveyors using expensive equipment.

MITRE is helping by providing the Flight Validation Toolset, which measures the height and position of obstacles that might get in the way of a flight procedure. Procedure designers using the Flight Validation Toolset can measure the size and location of obstacles from the ground or the air. (Ground assessments, when feasible, are generally more accurate.)

"As you develop new procedures, you move through different parts of the airspace, so you get exposed to a different set of obstacles," says Tom Becher, a program manager in the Center for Advanced Aviation System Development (CAASD), the federally funded research and development center MITRE operates for the FAA. By using the toolset, Becher notes, airlines, airports, FAA-authorized companies, and the FAA can save time and avoid the cost of expensive surveys while still yielding accurate and efficient flight procedures.

A Direct Effect on NextGen

MITRE developed the Flight Validation Toolset at the FAA's request. The new ground-obstacle measurement method uses commercial-off-the-shelf equipment; with some training, certified parties such as airlines can perform tests themselves.

Moreover, the toolset's lower cost will help airlines participate directly in the development of NextGen, which is part of the FAA's dual strategies of enabling third-party collaboration and streamlining procedure implementations. This will also allow airlines and procedure-design companies to take quicker advantage of benefits created by new procedures.

"Our team developed the Validation Toolset so that airlines and instrument flight procedure designers can inexpensively and accurately measure obstacle heights with equipment that's easily obtainable," says Tim Lovell, a MITRE senior systems engineer. In addition to Lovell, other team members include Jeremy Irish, Steve Chase, Adric Eckstein, and project team manager Mike Mills. They all work in CAASD's department for RNP/RNAV (Required Navigation Performance/Area Navigation) Standards and Procedures.

Inexpensive Measuring System

The MITRE-developed toolset includes a laptop computer, Global Navigation Satellite Systems (GNSS) receivers the size of hockey pucks, handheld GNSS survey units, and a laser rangefinder—all connected by serial or USB cables, or via wireless Bluetooth technology. Optional equipment can include a digital camera for obstacle identification and a portable webcam for real-time communication. The MITRE team demonstrated the tool's feasibility using a variety of commercial-off-the-shelf products that allows the airlines flexibility in how to meet the requirements.

"The laptop computer is connected to GNSS hockey puck receivers placed at specific locations we call anchor points, which you establish yourself," Lovell says. "They can be located anywhere around an obstacle, such as a transmission tower. Ideally, you would have 360 degrees of access around the tower so that you can establish four or more anchor points on which to place a receiver. Then you would use the laser rangefinder to measure the horizontal distance from the anchor points to the obstacle. The rangefinder also computes the height of the obstacle with its built-in inclinometer and trigonometry routine."

These measurements are fed into another MITRE-developed tool called TARGETS, for Terminal Area Route Generation and Traffic Simulation. (See "TARGETS Software Eases Design of Flight Procedures.") The software does a trilateration calculation to determine where the obstacle is located with respect to the anchor points. Similar to how GNSS measures position, trilateration measures the obstacle position using the distance measurements of a series of anchor points around the obstacle.

The toolset has an accuracy of 20 feet horizontally and 10 feet vertically. Alternatively, special instruments can make obstacle measurements from an aircraft, but these measurements will be less precise due to the movement of the aircraft. Therefore, when feasible, ground measurements are preferred, with in-flight measurements used to check the validity of the ground-based measurements. If there is a big discrepancy, test participants repeat the obstacle-validation process.

Continuing Work

A number of airlines are currently beta-testing the Validation Toolset so the FAA and the airline industry can more fully assess the toolset; results of this testing should be available late this summer. Based on the success of the initial toolset, the FAA has tasked MITRE to evaluate the effect of adding to the toolset a three-dimensional measuring process that uses LIDAR (Light Detection And Ranging) and stereo photogrammetric imagery.

Commercial-off-the-shelf equipment used with the CAASD's height measuring system. The equipment must be connected to a laptop by wire or by Bluetooth.
Commercial-off-the-shelf equipment used with MITRE's height measuring system. The equipment must be connected to a laptop by wire or by Bluetooth.

"Later, we'll use the Validation Toolset to address the second part of the FAA's flight validation process—the flight portion," says Lovell. "In this case, the GNSS receivers will be mounted on the aircraft cockpit glare shields and the windows. The flight track of the aircraft will be independently recorded by the Validation Toolset and can be compared in real time to the internal avionics system as it flies the instrument procedure, thus validating that it is on course and on speed.

In this bird's eye view, a rangefinder from a GNSS (GPS) anchor point measures an obstacle. Geo-referenced digital images from a GPS-enabled camera can be recorded with the obstacle survey. This provides the ability to photograph obstacles and have the images correctly positioned at the camera coordinates, or at the obstacle's location, to aid in future obstacle analysis.
In this bird's eye view, a rangefinder from a GNSS (GPS) anchor point measures an obstacle. Geo-referenced digital images from a GPS-enabled camera can be recorded with the obstacle survey. This provides the ability to photograph obstacles and have the images correctly positioned at the camera coordinates, or at the obstacle's location, to aid in future obstacle analysis.

"Eventually, we hope to see the Validation Toolset adopted by the FAA as the standard methodology and process for flight validation of performance-based navigation instrument flight procedures."

A laser rangefinder can be used from any vantage point independent of its GNSS-derived position to determine obstacle height. The software combines laser rangefinder measurements from several anchor points to compute a location for the surveyed obstacle.
A laser rangefinder can be used from any vantage point independent of its GNSS-derived position to determine obstacle height. The software combines laser rangefinder measurements from several anchor points to compute a location for the surveyed obstacle.

—by David A. Van Cleave

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