Acorn Welding is pleased to announce the upcoming approval of reinforced exhaust stacks for the Hawker-BeechCraft 1900D airliner. These new & improved exhaust replace the OEM exhaust stacks when they reach the end of their useful service life.

The OEM exhaust stacks are designed to limit the heat exposure from the exhaust to heat sensitive areas. The resulting angle of the exhaust stacks creates a significant load on the engine attach flange. This stress has been shown to cause excessive cracking of the flange and can result in the separation of the exhaust. Exhaust stacks with part numbers 129-950000-1 and 129-950020-1, have a stainless steel attach flange. Over time, the OEM modified the material and assigned part numbers 129-950000-15 and 129-950020-11. All 4 of these part numbers still have stressed flanges. Acorn PDA parts 129-950000-11AWL and 129-950020-11AWL feature a redesigned flange that is stronger, thicker, and larger in diameter to ensure that any cracking will be limited.

Exhaust stacks repaired, overhauled, or fabricated by Acorn Welding can either be provided in blasted matte finish or polished finish. It is also possible to have exhaust stacks ceramic coated silver or black however this not reccomended.

Acorn Welding can also repair the latest speed stacks that are located on the newest King Air aircraft. These exhaust stacks are wider and feature cowling mounted fairings to improve the speed of the aircraft. Unlike earlier models these exhaust stacks are shorter and can cause soot to deposit on the nacelles. These stacks should not be replaced with the earlier, narrower D4 Series exhaust stacks as the engine EGT is much higher on these aircraft. The wider base of the exhaust stack allows quick and efficient heat exhaustion from the engine.

Acorn Welding obtained its first turbine exhaust PDA for the DHC-6 Twin Otter. This well tested STOL workhorse has some of the hardest working aircraft in the world in its fleet. The exhaust stacks crack with age and vibration. Many aircraft work in hot, humid, or other hard environments and wore out the exhaust stacks. Acorn Welding specializes in manufacturing aircraft parts with organic shapes. The largest project to date was reverse engineering tooling for this legacy aircraft.

Acorn Welding has the capability and certification to manufacture new exhaust stacks for OEM use. Acorn Welding has many years experience providing organic shaped parts for the aviationi industry. We can tailor make you a new exhaust stack to suit your needs. We can provide a solution for you either from our existing tooling or we can custom manufacture tooling to suite your application.

Exhaust stacks can be manufactured from a variety of different materials depending on their applicaction. The following are the most common materials used in exhaust stack manufacturing:

• 321 Stainless Steel 0.040"-0.050"
• 625 Inconel Alloy 0.040"-0.050"
• 800 Incoloy Alloy 0.040"-0.050"
• Hastelloy X Alloy 0.040"-0.050"

• Simple Exhaust stacks without any fittings or weldements
• Advanced Exhaust stacks with fittings/weldements for rain/anti-ice protection or for heating air.
• Advanced Exhaust stacks with intergrated smoke systems for aerial marking or agricultural applications
• Advanced Exhaust stacks with intergrated oil burn off weldements

Acorn Welding also can produce secondary exhaust exjectors like the one shown above. These are often constructed out of light weight stainless steel to save on costs. The exhaust in these ejectors has a lower temperature than that going through the primary exhaust duct and as a result can be safely constructed out of stainless steel. Acorn Welding is certified for resistance seam welding to AMS-W-6858A fabricating larger sized ducts and securely attaching exhaust flanges to the stacks.



Acorn Welding can produce exhaust for virutally any turboprop or turboshaft engine. We stock flanges and can fabricate stacks for the following engines:PT6A, PT6B, PT6C,PT6T, and PW100

• Pratt and Whitney Canada PT6A, PT6B, PT6C, and PT6T
• Pratt and Whitney Canada PW100(by Request)
• Honeywell Aerospace TPE331
• GE Aerospace Walter M601
• Rolls Royce Allison 250, 300, 500