1. Field of the Invention
This invention pertains generally to the field of aircraft display units that provide information to the pilot or flight crew of an aircraft.
2. Description of the Related Art
Hardware and software design standards for the aviation industry have been published by the Radio Technical Commission for Aeronautics (“RTCA”). The RTCA has published DO-254 entitled “Design Assurance Guidance for Airborne Electronic Hardware” and DO-178B entitled “Software Considerations in Airborne Systems and Equipment Certification.” Each publication distinguishes between simple and complex electronic hardware, recognizes five classes of failure conditions, and provides guidance for each hardware and/or software design assurance level (“DAL”) associated with a given failure condition.
Level A is considered the highest DAL and corresponds to a “catastrophic” failure condition of which failure of the hardware and/or software may cause a loss of the aircraft. Level B corresponds to a “hazardous” failure condition of which failure may cause a large negative impact on safety or performance, reduces the ability of the crew to operate the aircraft due to physical distress or a higher workload, or causes serious or fatal injuries among the passengers. Level C corresponds to a “major” failure condition of which failure may be significant but have a lesser impact than a hazardous failure or significantly increases crew workload. Level D corresponds to a “minor” failure condition of which failure may be noticeable but have a lesser impact than a major failure. Level E corresponds to a “no effect” failure condition of which failure has no impact on safety, aircraft operation, or crew workload.
To meet the higher DALs, many standards have been developed. With respect to presenting the pilot with flight-related information and aircraft-system information and/or allowing the pilot to control systems installed somewhere on the aircraft by interacting with a cockpit display unit, data exchange protocols have been published by Aeronautical Radio, Incorporated (“ARINC”) in ARINC Specification 661 entitled “Cockpit Display System Interfaces to User Systems” (“ARINC 661”), an aviation industry standard known to those skilled in the art.
Although ARINC 661 could be employed for all aircraft systems, ARINC 661 may be considered too demanding for a manufacturer of an aircraft system because of the strict protocols stated therein. For example, information about real time parameter(s) of an aircraft system may be presented to the pilot and/or facilitate pilot control of the system; in order to do so, however, the strict protocols of the ARINC 661 have to be followed.
There may be occasions when an aircraft system does not need to meet higher DALs. For example, a cabin control system could be employed in an aircraft, but failure of such system may have no impact on safety, aircraft operation, and/or crew workload; instead, failure may mean a loss of passenger comfort. In this instance, although it may be beneficial to provide information about and/or control of the cabin control system to the pilot in the cockpit, it may not be beneficial and/or cost-effective for the manufacturer of the cabin control system to employ the strict protocols of ARINC 661 when such system does not have to meet higher DALs.