For operators flying with cathode-ray tube RM-850 radio management units with screens that are getting hard to read, Honeywell is offering an upgrade to the RM-855 with a liquid-crystal display (LCD). While Honeywell bought a quantity of the RM-850 displays, “[that] stock has now become depleted,” according to the company. “Honeywell is no longer able to repair units with CRT failures.” The RM-855 is a form, fit and function replacement unit; however, it requires a new mating connector. The existing wires need to be re-pinned into the new connector. Switching to the new display (priced from $42,500 to $46,500), offers new capabilities such as ADS-B interface, HF and third com tuning, Acars, CPDLC (switch com radios from voice to data mode), nav radio backup tuning and options to show RMI and engine backup display.
Manufacturers are now writing service letters for ADS-B upgrades for aircraft equipped with Primus II avionics. According to Honeywell, “These upgrades require modification to the Primus II communications unit, the mode-S transponder and the cluster module. Also required are a new communication unit strap module, upgrade to the RM-855 RMU (RM-850 RMUs do not support ADS-B) and upgrade of the GPS.” Other modifications may be required, such as to the display system and FMS.