Yesterday, 06:10 PM
Back in the early days of the 80s we were always seeking out ways to improve our fairly unreliable Exec 152s. Nathan F came out with the enlarged eyebrow windows and began producing and selling them. Dan Van Dusen came up with the idea of placing a roller just off the main drive belts on the pilot side to cancel the wild oscillations of the main belts hitting the frame. He began producing and manufacturing those rollers and selling them.
Nathan did not like the idea if the engine oil return hose to the tank being just a standard coolant hose. He decided that he would replace the rubber coolant hoses with Teflon stainless braided hoses. These worked out well except on the engine to tank hose. He was able to adapt a large diameter braided hoses to the engine and tank and was doing some hover testing when suddenly the cabin filled with smoke and the helicopter was on fire.
Nathan had a fire extinguisher on board so he landed and extinguished the flames but the heat wrap on the exhaust pipes was soaked with oil and the hot exhaust kept igniting the oil. He had landed right in front of his hangar so he was able to grab a large fire extinguisher and totally emptied it as well but the wrapped exhaust continued to ignite the oil.
At that point all Nathan could do was watch the fire spread to his plastic fuel tanks and consume his helicopter. When the fire had burned itself out Nathan found that the female threaded casting at the bottom of the engine had broken allowing the modified hose and fitting to separate from the engine pouring the engine oil all over the exhaust system. He surmised that his replacement hose was too ridged to safely absorb the engine vibrations thus cracking the engine casting.
Nathan’s experience is precisely why we began wrapping heavy aluminum tape or foil around the heat wrapped exhaust system to prevent any fluids from being soaked up by the heat wrapped exhaust system. The photo below shows the heavy foil covering the exhaust heat wrap.
![[Image: IMG-4801.jpg]](https://i.ibb.co/xqyHb87Z/IMG-4801.jpg)
Nathan did not like the idea if the engine oil return hose to the tank being just a standard coolant hose. He decided that he would replace the rubber coolant hoses with Teflon stainless braided hoses. These worked out well except on the engine to tank hose. He was able to adapt a large diameter braided hoses to the engine and tank and was doing some hover testing when suddenly the cabin filled with smoke and the helicopter was on fire.
Nathan had a fire extinguisher on board so he landed and extinguished the flames but the heat wrap on the exhaust pipes was soaked with oil and the hot exhaust kept igniting the oil. He had landed right in front of his hangar so he was able to grab a large fire extinguisher and totally emptied it as well but the wrapped exhaust continued to ignite the oil.
At that point all Nathan could do was watch the fire spread to his plastic fuel tanks and consume his helicopter. When the fire had burned itself out Nathan found that the female threaded casting at the bottom of the engine had broken allowing the modified hose and fitting to separate from the engine pouring the engine oil all over the exhaust system. He surmised that his replacement hose was too ridged to safely absorb the engine vibrations thus cracking the engine casting.
Nathan’s experience is precisely why we began wrapping heavy aluminum tape or foil around the heat wrapped exhaust system to prevent any fluids from being soaked up by the heat wrapped exhaust system. The photo below shows the heavy foil covering the exhaust heat wrap.