This paper introduces a method to efficiently monitor the status of a piston engine during flight. ECUs (Electronic Control Units) make it possible to fly safely without emergencies or urgencies with random electronic failures of components and connections. The same can be easily done on older engines by adding a reliable digital monitoring system and an automated calibration of the carburetors. In fact, their reliability is several order of magnitude inferior to modern turboshafts. In modern

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... gines with FADEC (Full Authority Digital Electronic Control) as the "on" button is pressed the sensors and actuators are checked. The CPUs will then run start-up during the cranking phase (engine running without ignition). If everything is all right, then the engine starts and the post start checks are also performed. During flight, the ECU checks CPUs, sensors and actuators. Therefore, the electronic system can be monitored with high reliability without much effort. The sensors may crosscheck the engine situation and may output very reliable early diagnosis of incoming failures. Statistical data on spare parts are invaluable for monitoring application, signaling weak or not-lasting components and failure modes. This is another advantage of automotive piston engines conversions to aircraft use. Drones 2018, 2, 10 2 of 15 drivers would call the wrecker every two years for an engine failure. Detailed statistical records are available in references [1] [2] [3] [4] [5] [6] [7] [8] [9] . A main factor of this poor performance is due to the small number of engines that are produced. Rotax 912/914 constitute more than 80% if the whole piston engine powered aerial vehicle fleet. Only slightly more than 50,000 engines of the Rotax 912/914 series were delivered since 1989, with approximately 45 million flight hours. In the same period, over eight million Fiat Fire engines were produced with approximately 20 billion hours. A production rate of 3000 engine per day is common for automotive engines. Therefore, the total number of the Rotax 912/914 engines sold in nearly 30 years would have been produced for a car in 16 days. This means that the amount of money that can be invested in the design, development and production of an automotive engine is several order of magnitude larger than aircraft engines. Since the design process even in modern days it far from perfect, the development of a new engine and of its production line usually encounters several unforeseen problems that have to be solved. In automotive engines, strict quality control is performed on the production batches with full traceability of the parts. Tolerances and fits measurement of main components are fully executed by expensive automatic machines and the assembly is fully automated. The defects should be measured in a few every 100,000 items produced. The run-in of the production line can be of 250,000 engines. This massive investment is justified by the fact that an even minor recall for defects can involve hundreds of thousand vehicles with huge costs. On the contrary, the aircraft engine runs out of budget easily. This fact compels engineers to patch the problem and not to solve it. A typical example is given by the camshaft early-wear-problem on a popular aircraft engine. The solution given is to use a special lubricant and to reduce the lubricant replacement interval. When the same problem arose in the FIAT Fire engine, a proper system of oil jets was designed to lubricate the camshaft in critical positions.