Design Considerations for Decongealing Oil Coolers

As commercial aircraft become capable of operating at higher altitudes, designers have become concerned with the possibility of oil congealing in the engine oil cooler when cooling air temperatures reach -30 to -40 F. The initial reaction has been to install so-called “decongealing” type oil coolers.

This paper discusses designs which are presently in use and examines the factors which cause congealing problems so that the engine oiling system can be properly designed to avoid oil congealing in the coolers. It points out that through proper selection of components an oil cooler will decongeal without the added bulk, weight, and expense of special “decongealing” features.