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EEC Temperature Control System Disclosure Number: IPCOM000249648D
Publication Date: 2017-Mar-13
Document File: 8 page(s) / 63K

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The system described herein permits better control of the environment of engine-mounted electronic boxes, and more specifically the engine electronic control.

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This is the abbreviated version, containing approximately 44% of the total text.

EEC Temperature Control System


The system described herein permits better control of the environment of engine-mounted

electronic boxes, and more specifically the engine electronic control.


As known in the field, a full authority digital engine (or electronics) control (“FADEC”)

includes a digital computer (often called an "Engine Electronic Controls” (EEC) or "engine

control unit" (ECU)) and its related accessories that control all aspects of aircraft engine

performance. FADECs have been produced for both piston engines and jet engines. The EEC is

a complex and critical component of the FADEC.

However, in certain type of jet engines, EEC units may fail at an unusually high rate,

which may be caused by the thermal cycling that occurs in a typical flight evolution.

Traditionally, the EEC is installed in a cold compartment around the aero-engine and is cooled

by ram air to survive the hot weather take-offs. In such traditional configurations, the EEC is

cooled on the ground by natural convection when the jet engine is off or at ground idle. On other

engines, when the engine is operating while on the ground, cooling air is drawn around the EEC

by the low pressure produced at the engine inlet.

During flight conditions, cooling flow for the EEC is provided by a ram air inlet. The

amount of cooling air is passively controlled by an orifice (or a venturi), part of the ram air inlet

system. As the aircraft accelerates to cruise speed, the amount of cooling flow increases, which

can cause two problems: a) overcooling the electronic circuitry at cruise and cracking of the

solder joints because of thermal fatigue, b) freezing of the condensed water within the EEC

pressure sense lines which may result in an unacceptable loss of thrust during cruise.

Thus, a typical EEC may experience in a single flight a range of ambient temperatures

between very cold at cruise (approximate range of -20 °C to 0 °C) to hot on the ground and low

altitude (approximate range of 70 °C to 90 °C) . Because of the extreme differences in these

operating temperatures, thermal expansion and contraction of the electronic components and of

the solder at the junction of these components to the circuit boards within the EEC occurs,

thereby leading to thermal fatigue and failure. Freezing in the EEC pressure sense lines may

cause an uncommanded loss of thrust.

When failure or temporary loss of thrust occurs, the EEC may need to be replaced at the

end of the flight; in some instances, the engine may even need to be shut down during the flight.

In any case, an engine maintenance action must occur. These situations are very costly to both

the airlines and to the engine/aircraft manufacturers due to flight disruptions, engine

maintenance, and component replacements. In-flight shutdown typically costs thousands of

dollars due to an aircraft having to land at a non-destination airport, and a back-up aircraft

having to be called or other form of transportation arrang...