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Exercise GK2 - MP Sensor Lead Disconnect

  • brentonrule
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brentonrule created the topic: Exercise GK2 - MP Sensor Lead Disconnect

Hi all, may be a silly question but my answer to question 10 on page 2.17 is (a) zero; surely if the lead is disconnected and IF it is the mechanism by which the pressure measured between the butterfly and the inlet valve is captured by the MP guage, there would be no reading of the MP on the guage ???

The answer is (d) 25HG which is logical but only if you can actually read the guage.

What am I missing here?

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bobtait replied the topic: Re: Exercise GK2 - MP Sensor Lead Disconnect

It isn't the instrument that is broken, it's the sensor lead. With no connection to the inlet manifold, the pressure being transmitted to the instrument would be the pressure at the broken end of the lead i.e. the pressure in the engine cowl. A manifold pressure gauge is really just a barometer.

Since manifold pressure drops at about one inch per thousand feet of height increase, the gauge could be expected to read about 25 inches. [the ambient pressure, assuming sea level to be about 30 inches].

It is not an uncommon occurrence, I have seen it on several occasions. The gauge simply reads the ambient pressure and no longer responds to changes in throttle position.


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