Operators of the Cessna Citation Latitude and Sovereign+ can obtain approval to fly Required Navigation Performance Authorization Required (RNP AR) approaches when the aircraft is equipped with the Litef LCR-100N Inertial Hybrid Navigator. Generally, the attitude and heading reference systems (AHRS), even in modern aircraft, aren’t precise enough to meet RNP AR requirements.
The LCR-100N recently received FAA certification on the Citations, in accordance with Advisory Circular 20-138D. RNP AR approaches are flown to 0.3 nm performance standards and are gaining in popularity as business jet operators apply for approval to use them and more aircraft meet the equipment requirements and pilots train to fly these approaches.
The LCR-100N blends global navigation satellite system and inertial data from the unit’s fiber-optic gyro to enable continued precision navigation, even with loss of the GNSS. Both versions of the LCR, the LCR-100 AHRS and LCR-100N, offer “hybrid position solution” capability, obtained by connecting the LCR to an external GNSS receiver. In addition, when equipped with the LCR-100N, an aircraft doesn’t need a separate magnetic sensor for heading alignment, as the LCR “facilitates autonomous heading alignment,” according to Litef (Booth 445). The heading data is available in Arinc 429 format, and Litef offers optional synchro (analog) interfaces for the AHRS data.
The MEMS-based LCR-100 AHRS replaced the earlier LCR-92 and -93, and both the -100 AHRS and -100N are installed in a variety of turboprops, business jets, helicopters, regional airliners, and military aircraft.