The 737 Virtual Flight Deck


The next-generation 737 airplane (737-600/-700/-800/-900) offers more advanced, even more reliable airframe systems and digital avionics for increased altitude, speed, and range capability. Key to the next-generation 737 is the computer-generated graphic representation of flight instruments on the common display system (CDS). Simply by loading flight-deck software, operators can use the CDS to replicate either the electronic flight instrument system with map (EFIS/MAP) display of classic 737 models (737-300/-400/-500) or the primary flight display/ navigational display (PFD/ND) used in the 777 and 747-400 models. As a result, operators can continue to fly their earlier 737s while introducing next-generation 737 airplanes into their fleets with minimal training. Operators who fly the latest 737 exclusively will find the more advanced PFD/ND display formats are aligned with those on the advanced 747-400 and 777. All operators who select the PFD/ND format will benefit from easier implementation of equipment for the future air navigation system (FANS).

Called the "virtual flight deck" by its project pilot, the flight deck on the next-generation 737 uses a computer-generated graphics presentation to reproduce either one of two different instrument panels: the panel in the 737-300/-400/-500 series of airplanes or the panel in the 777 and 747-400 airplanes. These two looks, presented on the next-generation 737 common display system (CDS), are more commonly known as the electronic flight instruments system with map (EFIS/MAP) and the primary flight display/navigational display (PFD/ND), respectively.

The CDS in the EFIS/MAP format is certified by the U.S. Federal Aviation Administration (FAA) as essentially the same as the EFIS/MAP flight deck in the 737-300. It has achieved the same type certification as the 737-300, freeing next-generation 737 flight crews from the requirement for simulator training time to learn the differences. Operators of 747-400 or 777 airplanes, as well as other 737s, can generate a flight deck that virtually represents those models in PFD/ND formats, lessening the amount of time flight crews need to spend in transition training. Flight crews using the CDS and its associated EFIS control panel have the same workload as they would on the 737-300. In addition, the new systems do not increase demands for crew attention during periods of peak activity.

The CDS evolved as an outcome of the challenge to develop an all-new 737. The task included incorporating new, improved digital technologies and the necessary attendant equipment while meeting the requirement to save airplane weight, reduce part numbers, and cut costs. This all had to be accomplished without losing the same type rating for flight crews who would use the new flight deck. The flight-deck redesign initially appeared to require several visible changes to incorporate new digital systems, including at least 22 new parts and a complicated flight-deck instrument panel made up of electromechanical and digital displays.

However, a brand-new flight deck was not an option. Operators had clearly stated that they wanted no change to the type rating, no requirement for additional flight crew simulator training, and no new "bells and whistles" without clear economic or safety value.

The resulting "virtual flight deck" reflected several improvements and new features:

  1. Primary flight instruments.

  2. Digital engine control and avionics.

  3. Engine display format options.

  4. Improved ergonomics.

  5. Advanced common display system components.

  6. Backup systems.

  7. Manual display switching.

  8. Enhanced color and number displays.

Primary Flight Instruments
In order to duplicate the functionality of the 737-300 flight deck, any change to its integral presentations had to be minimal in the following displays on the next-generation 737 flight deck:

EFIS/MAP.
The 737-300 EFIS/MAP system (figure 1) uses CRT displays for the primary electronic attitude direction indicator (EADI) and for the electronic horizontal situation indicator (EHSI). Some operators use electromechanical attitude direction instruments (ADI) rather than the CRT EADI. The EADI presentation includes autothrottle mode annunciation, autopilot mode annunciation, and vertical speed tape option. Superimposed over the navigation data on the EHSI are weather radar and traffic collision avoidance system (TCAS) targets.

ANALOG/ELECTROMECHANICAL INSTRUMENTS
These instruments on the 737-300 are arranged in the basic "T" scan familiar to most flight crews. They consist of a "round dial" electromechanical airspeed indicator, altitude indicator, and vertical speed indicator.

The flight crew of the 737-300 manipulates sliding white plastic "bugs" to indicate critical takeoff and landing speeds. For navigation, the crew moves the "rabbit ears" located on the radio distance magnetic indicators (RDMI), which allow the crew to select the automatic direction finder (ADF) or very-high-frequency omni range (VOR).

The EFIS/MAP format of the CDS graphically generates the same "round dial" analog presentation and presents it in the classic "T" scan pattern.

The white plastic airspeed bugs that pilots previously slid manually around the ring of the Mach airspeed indicator (MASI) are now graphically displayed and automatically positioned by the flight management computer (FMC) (figure 2). For dispatch with FMC inoperative, the bugs can be set manually through the speed reference knob located above the engine displays.

Digital Engine Control and Avionics.
Avionics on 737-100/-200/-300/-400/-500 airplanes use the analog-based ARINC 500 series. The propulsion control system in the 737-100/-200 is analog based and hydromechanical; on 737-300/-400/-500 models, it is electronic supervisory (hydromechanical control with electronic trim).

However, the next-generation 737 design called for full-authority digital-electronic engine control (FADEC) and digital ARINC 700 series avionics. These improvements made most of the analog-based electromechanical instruments and the flight crew interfaces on the 737-300 obsolete.

The next-generation 737 offers systems to increase cruise speed to Mach .80 from Mach .74, increase cruise altitude from flight level (FL) 370 to FL 410, increase its range, and improve on its already excellent dispatch reliability.

Engine Display Format Options.
Engine instruments on the 737-300, with some options, are analog/ electromechanical style. Data are displayed in rolling digits and multiple green-colored LED segments that serve as analog pointers.

The two flight instrument displayformats available through the CDS offer operators two choices in loading the engine display formats: "over-under" or "side-by-side" (figure 3).

The "over-under" format is nearly the same engine presentation as the 777, using both the upper and lower display panels simultaneously.

In the "side-by-side" format, engine instruments and warning lights are computer-generated in the same geographical locations as on 737-300/-400/-500s.

Improved Ergonomics.
Flight-deck components are arranged so that flight crews seated at the appropriate eye-reference point can operate controls and instruments without unnecessary motion. Each crew member has convenient access to an individual glare-shielded EFIS control panel (figure 4) for manual control of

The flight crew can individually adjust the brightness of each display unit using control panels at each pilot station. In addition, automatic brightness controls adjust the brightness of all six display units as well as adjusting each individual display unit in response to sunlight.

Advanced Common Display System Components.
The CDS comprises six flat panel LCD display units and two display electronic units (DEU).

FLAT PANEL DISPLAY UNITS
The six identical, state-of-the-art ARINC D-size display units are 8 by 8 in (20.32 by 20.32 cm). Each has a 6.68- by 6.68-in (16.97- by 16.97-cm) usable display area. The four display units located outboard and inboard on the captain's forward panel and first officer's forward panel show all primary flight and navigation data. The upper- and lower-center display units on the center panel show engine and system data.

DEU
Two DEUs drive the display units. The DEUs collect, process, and display analog discretes, analog variables, and digital bus data. Each DEU can provide completely independent sources of flight information for each of the captain's and first officer's displays. Normally, the left DEU drives the captain's display units and the upper-center display unit; the right DEU drives the first officer's display units and the lower-center display units. In the event of a single DEU failure, the system automatically switches all displays to the operating DEU. In case of an undetected failure, the crew always has the option to manually switch to the appropriate DEU.

Backup Systems.
The CDS provides for automatic switching to handle failures of the DEU or display units. For instance, the CDS has internal monitoring of display unit failures and automatically maintains a PFD in view for all single failures. In the EFIS/MAP mode it switches to PFD mode, with all primary instruments in "round dial" form compacted into one display (figure 5).

The PFD/ND format merely moves its vertical speed tape version as-is to the functioning display unit. The failed outboard unit remains blank to prevent confusion. In the event of operational failure of the upper unit of the two central displays, the engine format automatically moves to the lower display unit. If the engine data are moved to the lower-center display unit, either manually or automatically, the upper-center display unit becomes blank. In all cases, the flight crew always has the option to manually place formats and select its source by using the display source selection.

Manual Display Switching.
A display source select switch and an EFIS control select switch are located in the overhead panel for failures of the individual DEU or EFIS control panels for the captain and first officer. When the EFIS control panel select switch is in the NORMAL position, each crew member controls his or her own display. However, if one of the EFIS control panels fails, the crew member can select BOTH ON LEFT or BOTH ON RIGHT. This allows one crew member to control both sides of the displays, with identical EFIS control functions shown at both crew member positions. When required, the crew member can manually force the PFD to either the inboard or outboard display unit by using the display select panel located just above the outboard display unit. This panel also allows the crew member to manually move engine and other display formats to new locations, depending on the presentation format.

Enhanced Color and Number Displays
The new CDS also provides enhancements to basic 737 features through the use of color and alphanumeric characters, borrowing from the colors and shading developed for the 777. Examples include amber warnings on the fuel indicator (for FUEL CONFIGURATION, FUEL IMBALANCE, and LOW FUEL) and green or amber indication on the engine display (for TAI [thermal anti-ice], ENGINE FAIL, and REV [reverser position]) (figure 6).

The next-generation 737 flight instrument systems meet Federal Aviation Regulation (FAR) Part 25 airworthiness standards for transport category airplanes and Joint Aviation Authorities requirements. In addition, FAA advisory circulars, though not strictly required, are applicable. These circulars cover transport category airplane electronic display systems, system design analysis, minimum flight crew, and crew qualifications and pilot type rating for transport category aircraft operated under FAR Part 121.

Summary
The CDS for the next-generation 737 flight deck provides flexibility for all 737 operators. Those already flying 737 airplanes can continue to operate earlier 737s as well as next-generation 737 models using the EFIS/MAP format with minimal training. New 737 customers may choose the more advanced PFD/ND, which is similar to the display format on the 747-400 and 777 and provides capability to implement FANS if desired (see related article in AERO No. 2, April 1998).


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Mike Hewett
737 Chief Pilot

737 Program
Boeing Commercial
Airplane Group

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