Keypads seem to be mat-ter-of-fact arrays of push-button switches laid out in unassuming squares or rectangles. But these devices can reflect a complex design evolution. Take the case of the AT2901 control panel developed by UPS Aviation Technologies (UPSAT).
Automatic dependent surveillance-broadcast (ADS-B) technology was the driver behind UPSAT’s AT2901. But the keypad can be used to control the presentation of weather radar, terrain and navigation data overlaid on the company’s AT2000, 6.1-inch (15.5-cm) -diagonal, multifunction display (MFD). The keypad also will be able to control a hybrid system UPSAT is completing to address the proposed rule that cargo aircraft have traffic alert collision avoidance systems (TCAS) installed by Oct. 31 2003. (The hybrid system will correlate TCAS and ADS-B data, appealing to air transport, as well as cargo carriers.) ADS-B promises benefits such as instrument-based approach spacing and station-keeping, as well as enhanced situational awareness for surface operations.
In May 2002 UPSAT was completing supplemental type certification (STC) approval for TCAS on a Boeing 757, using the new display and keyboard. (The STC also includes an ACSS TCAS computer and UPSAT’s AT700 Mode S transponder.) An STC of the hybrid system–adding the ADS-B computer–on a B757 is expected in August. UPS plans to install the correlated system on some B757s and B767s, although the exact number and date are undetermined.
In the 757 installation, the keypad is mounted on the center panel and the MFD is in the center cockpit, forward of the throttle controls. The AT2901 is about 6 inches (15.2 cm) wide and 1.5 inches (3.8 cm) from top to bottom, comprising three rows of 10 keys each.
Keypad History
UPS Airlines sponsored UPSAT to work on ADS-B in early 1998, recalls Steve Horvath, UPSAT’s software engineering manager for air transport products. The first version of the keyboard was approved for use on B727s and DC-9s, in preparation for the first operational evaluation of ADS-B technology in 1999.
With input from Cargo Airline Association (CAA) pilots and UPS flight operations, UPSAT developed the original keypad, which was used by UPS (B727), FedEx Express (B727), and Airborne Express (DC-9) in OpEval 1. Afterwards UPSAT solicited more input, forming a "key group." Some crewmembers "wanted to reorganize the keys and change the labeling," to group certain related functions vertically, Horvath says.
Version two adopted this principle. To select ADS-B traffic targets, for example, the pilot pushes the target (TGT) key–located on the right side of the panel. Target-up (T`) and target-down (TØ) keys, above and below the TGT key, activate the next aircraft icon farther ahead of or closer to the user’s aircraft. Similarly, the velocity vector (VEC) key turns that feature on and off, allowing the pilot to see where ADS-B targets will be at various time intervals. V` and VØ are used to adjust the time value. Pressing the display (DSP) key toggles between a 360-degree compass rose and a 120-degree arc view. Range-up (R`) and range-down (RØ) keys change the range of the map area on which the display is set.
The second iteration also added more tactile feedback, so that aircrews can feel a "firm snap," or "click," when they press a button. Designers also decided to recess the keys slightly below the frame, preventing users from accidentally pressing two keys at the same time.
B757 Changes
The B757 installation involved a few other changes. UPSAT added a captain/first officer (C/F) key that controls whether the pilot’s or first officer’s navigation data will be shown on the MFD. Designers also added a traffic (TFC) key to activate the TCAS or hybrid display. (Pressing the TFC key toggles between "off" and "on," although a traffic alert automatically reactivates the display.) To make room for these changes, UPSAT combined the look-up (LK`), level (LVL) and look-down (LKØ) keys (from version two) into one key, (LKÊ), which sets an altitude filter for targets.
Externally controllable dimming has been added for the B757 STC, as well. The B757 has one central dimming control knob, which is used to adjust lighting on the MFD control panel, as well as the radio and transponder controls.
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