Two BK-117 pilots failed to notice on preflight inspection that a mechanic had installed the left dual cyclic control backwards. The error was noted prior to flight.

Narrative

I arrived at work for night shift. Upon completion of signing in; checking the aircraft logbook; getting a flight release; checking NOTAMs and TFRs; checking weather; performing the pilot brief; briefing the communications staff; and briefing the medical crew; I drove to the Helipad and performed what I thought to be a thorough preflight. It was dark due to the time of day and misting due to an approaching thunderstorm. I used a flashlight and I paid particular attention to the maintenance that had been done that day involving the #2 Engine Fuel Pump replacement. I was aware that the Dual Controls had also been installed that day per the logbook entry and that both the Fuel Pump and Dual Controls Installation had been checked by the day shift pilot. I completed the preflight noting nothing out of the ordinary. I did not fly during my shift as weather was below my minimums. After leaving work the following morning I drove home and later that day received a call from the day shift pilot informing me that the mechanic had installed the cyclic backwards and that we had all missed this error during the installation phase and during my and his preflights. The day pilot found the error prior to any damage or injuries while preparing to depart on a patient flight. The mechanic was notified; he installed the cyclic correctly. The flight was delayed approximately 20 minutes for this error. Suggestions: 1. Each pilot should sit at each pilot station that has a set of controls during preflight to ensure that the controls are mounted correctly and a full flight control function check (at each station) should be performed each time the duals are removed or installed. 2. To completely avoid this error it may be appropriate for the manufacturer to re-engineer the way flight controls are mounted so that they can only be installed the correct way. The adage 'Change is written in blood' certainly could have applied had this error not been detected prior to takeoff.