Twin Commander Aircraft has developed a replacement for the troublesome Sundstrand environmental control unit (ECU) for JetProp models (840, 900, 980 and 1000). The replacement system is based on an improved version of the Enviro Systems ECU. The original Enviro ECU was developed in conjunction with Gulfstream Aerospace when it was producing JetProps as a warranty replacement for factory-installed Sundstrands.
According to Twin Commander Aircraft, Sundstrand ECUs have been plagued by reliability issues, while Enviro Systems has improved its original ECU by making it more reliable and by using a new temperature controller that does a better job of maintaining cabin temperature at the selected value. The improvements will be made available to JetProp owners with Enviro units, and the entire Enviro Systems ECU is being offered as a kit to JetProp owners with Sundstrand units.
The kit provides for complete replacement of the Sundstrand ECU with an Enviro system and includes heat exchangers, blowers, bleed-air plumbing, and new air inlet and outlet vents mounted on the aft fuselage. A separate air-conditioning unit is required for the Enviro ECU. Sundstrand-equipped airplanes with air conditioning would not have to replace their AC units when converting to an Enviro system. Twin Commander is working on an air-conditioning package for the Enviro system
for those operators who do not already have an AC unit.