A new temperature correction algorithm for FAA engine cooling tests

Abstract

An analysis of the Federal Aviation Administration (FAA) certification requirements has revealed a potential error in the temperature correction formula the FAA requires manufacturers to use to process engine cooling data for compliance with Part 23 of Title 14 of the Code of Federal Regulations (14 CFR Part 23). The FAA engine cooling performance temperature correction formula, which predicts the critical temperature of engine components, was quantitatively evaluated using data acquired with a single-engine aircraft powered by a normally aspirated, air-cooled, reciprocating engine. Previous research has failed to analyze the effect ambient air temperature has on oil temperature and has failed to propose a more accurate model for predicting critical cylinder head and oil temperature. Engine cylinder head and oil temperature data were acquired during FAA-defined, cooling-performance climbs performed on three days with different ambient air temperatures. The acquired data revealed the FAA correction formula, when applied to cylinder head temperature, did not correct data to the most critical test condition, potentially leaving certified aircraft vulnerable to overheating. The acquired data showed the FAA correction formula, when applied to oil temperature, worked fairly well. Nonetheless, there was room for improvement. Thus, new temperature correction formulas were developed to predict both critical engine cylinder head and oil temperature for compliance with 14 CFR Part 23. The FAA can evaluate these correction formulas for use in 14 CFR Part 23 to ensure engine cooling performance is properly tested and general aviation aircraft remain safe from overheating.