Acorn Welding in Edmonton, Canada has been granted STC approval from the FAA on its new exhaust stacks for the DHC-6 Series Twin Otter aircraft. The STC allows Acorn Welding to extend the approval already granted by Transport Canada to those jurisdictions that rely on FAA STC approval.
Acorn says equipping the DHC-6 Twin Otter with its modern exhaust stack will allow the aircraft to better utilise the jet thrust generated by its engines. The PT6A-34 engine generates 82lb of jet thrust while the -27 generates 90lb and it says this jet thrust more than offsets any additional drag created by the exhaust while directing hot exhaust and combustion by-products away from the leading edge of the wing.
The new exhaust installation is lighter than the existing DHC-6-400 exhaust and it is constructed without the use of turning veins to redirect the exhaust rearwards. It says the complete Inconel 625 construction will solve the engine flange corrosion problem that exists for operators in a highly corrosive salt-water environment.
In addition to the DHC-6, Acorn manufactures aftermarket exhausts for the Beechcraft King Air 200, 250, 300 and 350 series of aircraft.