Aero 22 Index Horizontal Navigation

Index Vertical Navigation New ETOPS RegulationsMaintenance of High-Strength Alloy Steel ComponentsRich Higgins PDF file






Top of page















Top of page

The Category IIIB Autoland, Global Navigation Satellite System Landing System, Integrated Approach Navigation, and Navigation Performance Scales options work together or separately to improve safety and performance while decreasing operating costs.

Operators will be able to enhance the approach capability of their 737-600/-700/-800/-900 airplanes this year with a suite of new flight deck navigation options: Category IIIB Autoland, the Global Navigation Satellite System (GNSS) Landing System, Integrated Approach Navigation, and Navigation Performance Scales.

Together with the excellent existing approach capabilities
of the 737, these options offer a flexible navigation solution for airlines that want to increase their competitive advantage by improving airplane safety and performance, decreasing operating costs, and reducing flight crew training requirements through advanced technology.

The new navigation options work together or separately to enable pilots to fly safe, stable, and precise three-dimensional paths that smoothly intercept a variety of final approach legs.

The options improve landing capability in adverse weather conditions, in areas of difficult terrain, and on existing difficult approach paths. It addition, they will allow crews to take advantage of emerging air traffic control technologies designed to improve airport operations.

To help operators understand these navigation options and their features, this article describes

  1. Category IIIB Autoland.
  2. GNSS Landing System.
  3. Integrated Approach Navigation.
  4. Navigation Performance Scales.

The article also discusses how the options and procedures are compatible with current and emerging approach navigation technologies such as the Instrument Landing System, mixed-mode, and constant-angle nonprecision approaches.


The new 737-700/-800/-900 Category IIIB Autoland option (fig. 1) provides the same all-weather, precision approach autopilot guidance currently available on other Boeing airplane models.

This option, which is in flight test, will be offered with the 737-700/-800/-900 over-under engine format. The over-under format provides the display space necessary for Category IIIB Autoland system messages. (The 737-600 is not currently being certified for Category IIIB operation.).


The 737-600/-700/-800/-900 GNSS Landing System (GLS) option uses Global Positioning System navigation satellites and a Ground-Based Augmentation System (GBAS) to provide signals similar to Instrument Landing System (ILS) signals (fig. 2). Ultimately, the GLS could replace the ILS as the primary means for guiding airplanes to the runway in low visibility. The GLS also might be expanded to support curved approaches. (See “Global Navigation Satellite System Landing System,” Aero no. 21, Jan. 2003.)

The initial 737-600/-700/-800/-900 GLS option supports a Category I instrument approach capability and the ability to complete the approach with an automatic landing. This system is being expanded to support full Category IIIB Autoland operations.

Retrofit for the 737-600/-700/-800/-900 GLS requires new multimode receiver (MMR) hardware and software, a navigation control panel with GLS capability, hardware and software upgrades for the enhanced ground proximity warning system (EGPWS), flight management computer (FMC) U10.5 software, and common display system (CDS) Block Point 2002 software. A future curved GLS approach capability might require autopilot and CDS software changes.

The U.S. Federal Aviation Administration (FAA) plans to deploy GLS ground stations in Memphis, Chicago O’Hare, Juneau Alaska, Seattle, Phoenix, and Houston to support operational evaluation testing. The program calls for the purchase and deployment of as many as 40 ground stations per year after the initial phase. The FAA projects a total of 160 GBAS ground stations are needed in the United States. Europe also plans to develop and install GBAS ground stations.


Integrated Approach Navigation (IAN) is an approach option designed for airlines that want to use ILS-like pilot procedures, display features, and autopilot control laws for nonprecision (Category I) approaches. This option does not require additional ground facility support.

Top of page

The FMC transmits IAN deviations to the autopilot and display system. The pilot procedures for IAN are derived from current ILS pilot procedures and are consistent for all approach types: Select the approach on the FMC control display unit, tune the appropriate station, and arm the autopilot approach mode. The IAN function supports the ILS for glideslope inoperative, localizer only, and backcourse approach types.

The IAN function will alert the crew to approach selection or tuning inconsistencies. For example, if an ILS station is tuned and an area navigation (RNAV) approach also is selected on the FMC, the flight crew will be alerted and the ILS approach mode will take precedence automatically, with the appropriate display format.



Top of page

While the IAN display (fig. 3) is similar to an ILS display, there are sufficient visual differences to ensure that the crew does not confuse a nonprecision IAN approach for a precision ILS or GLS approach (fig. 4). As on all nonprecision approaches, the altimeter is the primary method of ensuring that altitude constraints are honored.

Retrofit of this option involves software updates for the FMC, CDS, flight control computer, and digital flight data acquisition unit (DFDAU) and hardware and software updates for the EGPWS.


Navigation Performance Scales (NPS) is a new display feature that integrates the current lateral navigation (LNAV) and vertical navigation (VNAV) with actual navigation performance (ANP) and required navigation performance (RNP). The primary display format of the NPS (fig. 5) can be interpreted easily, thereby allowing the crew to monitor flight path performance relative to flight phase requirements and airplane system navigation performance.

NPS can be especially valuable for approaches with tight airspace restrictions because of terrain, traffic, or restricted areas. LNAV and VNAV with NPS supports Category I approaches down to 0.10-nmi RNP. NPS also is designed to smoothly transition to an ILS, GLS, or IAN approach. (For a detailed description of NPS, see “Lateral and Vertical Navigation Deviation Displays,” Aero no. 16, Oct. 2001.) Retrofit of this option involves software updates for the FMC, CDS, and DFDAU.





Top of page


This year, operators will be able to enhance the approach capability of their 737-600/-700/-800/-900 airplanes through a suite of new flight deck navigation options: Category IIIB Autoland, GLS, IAN, and NPS. These options enable pilots to fly paths that smoothly intercept various final approach legs. This integrated, flexible approach navigation solution improves safety and performance and decreases operating costs. The options are designed to meet the current and future approach requirements of Boeing customers worldwide.




| Top of page | Boeing Home | Boeing Commercial | Contact Aero |
  Aero Copyright © The Boeing Company. All rights reserved.
Field Service Search Archives About Aero Home Boeing Home