Oil Temp Caution Light

[mdogan]

Hi, At UH1 and AB-206 helicopters, there is not an Engine Oil Temp Caution light. For AB-206 there is only one data for engine oil temp limiting(Temp of Oil)and for UH1, there are two datas for engine oil limiting(FAT and Temp of Oil relationship). Is the absence of this Caution light because of a design choice or because of an engineering requirement?
Thanks for help and ideas.

[gulliBell]

The answer to your question is to think of this from the system perspective.

The engine oil system has an OIL PRESS low warning light, which is triggered by a pressure switch (typically at about 24 psi). Other indicators in the system are oil pressure and oil temperature, which indicate their particular values from pressure transducer and temperature probe. These 3 components are all you need to determine the health of the engine oil system for continued operation.

A single indication of low oil pressure, indicator, or warning light should not be treated as an oil system failure.

The flight critical malfunction is loss of engine oil pressure, because an engine without oil flowing through it (i.e. pressure) will cease to operate very quickly. Which is why it has a warning light. Confirmation of the malfunction is engine oil pressure gauge indicating low, or oil temperature gauge indicating high.

What if the engine oil temperature indicator alone was high? An oil cooler blower malfunction may cause the oil temperature to indicate high (above about 115 degC), but this is not such a big deal. The oil can get a lot hotter than this and still provide sufficient lubrication for the engine to continue to operate. You have time to fly somewhere to land safely and have the cause investigated (the oil in the engine is a lot hotter than 115 degC, the oil temperature probe is usually in the oil system loop after the oil has passed through the radiator/cooler).

Short answer: oil temperature is a secondary indication of an oil system malfunction which is why there is no ENG OIL HOT warning light.

[SASless]

My alcohol ravaged brain causes me to disremember exactly the layout of the Huey Engine Oil System....but if it used a wet bulb sensor for temperature after the cooler in the return line....an absence of flow of oil might yield inaccurate or unusual indications contrary to the actual temperature.

The absence of oil over the bulb would also create an issue as it is measuring the temperature of the air or structure touching the bulb and not the oil.

Knowing the normal indications and being attuned to being to changes from normal temps or other unusal indications is important.

Gullible is right...a single indication is of some concern....two or more are of real concern.