The factory has issued a statement- Honeywell Obsolescence Update (PDF) – advising that the majority of the old equipment is considered obsolete and not repairable. However RNB is still able to calibrate / repair the majority of these units: Read the RNB Aviation Capabilities List.
The calibration cycle of Chadwick – Helmuth equipment has always been a mystery. After calibrating / repairing Chadwick – Helmuth equipment for 25 years and for all segments of the aviation industry, RNB has its own recommendations – Read them now in PDF format.
The official factory statement on calibration of the Chadwick – Helmuth equipment is outlined in a letter from Honeywell – Honeywell Calibration Letter (PDF)