An ISIS is designed to combine the functions of separate equivalent mechanical instruments that had previously been included as backup in such cockpits, including
altimeter,
airspeed indicator, and
attitude indicator. Various aspects of ISIS are defined by its function of being a backup to conventional instrumentation. In accordance with this principle, it has been designed to operate with a high level of availability and reliability, as well as being as independent as possible from the aircraft's primary instrumentation and sensors alike. It is commonplace for an ISIS to work in conjunction with provisions for auxiliary power (typically a
battery unit), as well as harnessing embedded sensors for its readings wherever possible. When all onboard instrumentation is performing normally, the readings indicated by an ISIS are identical to those of the
primary flight display. Advantages presented by ISIS over traditional systems include increased safety, greater ease of operation, and reduced operating costs. A number of aircraft have been produced with relatively sophisticated integrated standby systems which may include additional functions. For example, the
Rockwell Collins Pro Line 21 flight deck, which is fitted to aircraft such as the
Cessna Citation XLS+ business jet, features a standby navigation display and engine gauges.
Thales Group produces its own ISIS, which is installed on the
Airbus A320 narrow-body and
Airbus A330 wide-body airliners, among other aircraft; it allowed for one single instrument to replace four standby instruments that had been traditionally used. Thales also produced an Integrated Electronic Standby Instrument (IESI) dedicated for use on
helicopters; in excess of 6,000 such units have reportedly been sold as of July 2020. Another such system is manufactured by
L3Harris Technologies, intended for both helicopters and
general aviation purposes. Additional companies specialising in avionics, such as
GE Aviation,
Smiths Group, and
Meggitt, have also marketed ranges of standby instrumentation using both standalone and ISIS-compliance principles. Several companies have produced
patentable innovations related to ISIS, including large aerospace players such as
Airbus Group. In addition to such technology being adopted upon new-build aircraft, several operators have opted to retrofit their existing aircraft fleets with current generation ISIS, such as
UPS's
Airbus A300 freighters. Along these lines, Rockwell Collins developed a retrofit package for the
Boeing 757 and
Boeing 767 that incorporates ISIS. During the 2010s, the cost of performing such cockpit display retrofits reportedly dropped substantially. ==See also==