R. Fred Polak | Editor
Electronic flight instrument systems (EFIS) have been around the aviation community for quite awhile now. They bring the advantages of less weight, less wiring and less power consumption to the helicopter. The level of integration EFIS employs greatly simplifies the interface required with other systems on the helicopter. Couple this with the concentration of essential flight information in the pilot’s prime viewing area, and it’s easy to understand the growth of these systems on today’s helicopters. The performance advantages of display integration, flexibility, redundancy and reliability are tough to beat. Cobham’s 3-D synthetic vision EFIS for helicopters is truly a system for flight in the 21st century.
The system’s integrated display units (IDUs) are available in two sizes. The IDU-450 has a four-by-five-inch display area, whereas the IDU-680 has a six-by-eight-inch display area. The IDU-450 can be installed as a primary flight display (PFD) and also as a multifunction display (MFD). The IDU-680 has two display functional areas. The PFD and MFD are on the same display unit. The IDUs are full-color, high-resolution, sunlight readable liquid crystal displays (LCDs), with fully-adjustable brightness control. They include a voice warning system and illuminated controls with tactile differentiation. The units are line replaceable and are upgradeable and expandable. They even have a built-in simulator to better facilitate training!
There is also available the EICAS-450, (primary engine instrument crew alerting system), not pictured here. The IDU is essentially two parts: the user interface module or faceplate and the electronics/power supply.
The system offers a host of display capabilities as a function of what other systems are on the helicopter and interfacing with the EFIS. These displays include; moving map, flight management system (FMS) data, terrain awareness and warning system (TAWS) data, and flight director steering information typically related to the pilot via “Highway In The Sky” (HITS), or, can be displayed as legacy reactive “V” bars or cross hairs. Weather radar, automatic dependent surveillance–broadcast (ADS-B) and traffic avoidance system, traffic collision avoidance system (TAS/TCAS I/II) data can also be displayed, as well as an automatic helicopter hover mode.
This EFIS was designed from the ground up to satisfy FAR Part 29 IFR requirements, the most rigorous certification path. It can be installed and is certified in helicopters flying FAR Part 27 and 29. It can be installed as a single-side PFD and MFD (two IDU-450s), or a dual installation with the pilot and co-pilot each with its own PFD and MFD (four IDU-450s). The IDU-680 displays can also be installed single side (two displays), or dual side (four displays).
The display unit’s primary interface is ARINC 429, RS-422 and RS-232. An optional analog interface unit (AIU) is available to integrate into legacy airframes. The IDUs can accommodate an air data attitude heading reference system (ADAHRS) and a 15-channel global positioning system/space-based augmentation system (GPS/SBAS Class Beta 3) receiver secured to the rear of the IDUs as an integrated hardware package enhancing reliability, and reducing installation and design effort. This applies to either the IDU-450 or 680 displays. The system can also have ADAHRS and GPS stand-alone units.
A single-side system would include two IDUs, an ADAHRS with outside air temperature (OAT) probe and a magnetic sensing unit (MSU), a GPS receiver and antenna. This approach creates a panel mounted avionics “rack” incorporating multiple systems formally remote mounted or separate such as EFIS, flight director (FD) computer, moving map, TAWS, FMS, GPS, heading and attitude systems, air data computer, weather radar display, conformal TAS/TCAS-I/II display, ADS-B, FIS-B, TIS-B and satellite weather display.
The engine instrument crew alerting system (EICAS) capability and display of engine instrumentation and master warning system is an option and if installed, a data acquisition unit (DAU) is required.
Software updates are accomplished via a USB connector on the front of the IDU. The system employs BIT and it is active from power-on to power-down.
The ADAHRS is a solid-state strap-down AHRS with a mean time between failure (MTBF) of 13,000 hours. The GPS is a 15-channel Class Beta 3 receiver and includes receiver autonomous integrity monitor (RAIM). The fully integrated FMS supports all ARINC-424 leg types.
3-D Synthetic Vision
Cobham’s EFIS is currently the only one that displays conformal traffic on the PFD. There are a number of other systems that have 3-D terrain and obstructions displayed.
Highway In The Sky (HITS)
HITS is the latest in flight director navigation. It allows the pilot to fly to literally any point in the world with ILS precision. The route appears on the PFD as a series of green boxes superimposed over the flowing terrain of the 3-D synthetic vision. The pilot needs simply to fly through the boxes to follow the route.
The system is normally installed at the OEM or an authorized installation facility. The STC is owned by various OEMs, installation facilities and of course Cobham. Installation time is a function of system complexity. If a single MFD to be installed, or a full dual side configuration. In any event, integration of the ADAHRS, GPS and TAWS reduces the overall installation time required.
Maintenance actions are minimal and straight forward. All LRUs are changed on condition. The ground maintenance mode allows for plain language troubleshooting. Software is field loadable via USB connection, and a fault log is also downloadable via USB connection. A comprehensive service kit consists of a single 9/32 Allen wrench which is used to install and remove the IDUs from the helicopter. It is also used to install and remove the integrated sensors from the IDU, as well as the installation and removal of the IDU display face.
EFIS have really transformed the flight deck for helicopters, from large, bulky cathode ray tube (CRT) displays, to smaller, lighter LCD displays. Sensor integration has also allowed the benefits of today’s technology to become the norm rather than the exception in the world of rotorcraft. Climb aboard for a ride with avionics for the 21st century.
Editor’s Note: I would like to give special thanks to Ed Gaines, Cobham’s business development manager (communications) for his timely efforts in helping me write this article.