3 pistoned engined questions !!!

[dynamite dean]

could someone please answer these following questions as trying to get straight forward straight to the point answers is difficult in my school.the following is from my recentley written Flight instructors exams.

1. "during engine run up prior to flight an a/c equipped with a CSU, explain to a student pilot why an increase in Manifold pressure is noticed whilst exercising the propeller 10 marks?!"

2. your training has one static port on the left hand side of the fuselage side and the pitot tube on the left wing. tell me as you student what will be shown on the primary insrtuments during an exerecise on slide slipping specifically to the left.empahize any errors caused.

3. This is from a question on my recently written ATPL what is de icing paste best used on? toilet ducts,aerials, or pitot heads

Any help would be massively apprecited as here in south africa some people do not know the answers to these questions!

[Stan Evil]

I'll have a go at the first two:

1. When you exercise the prop the rpm is reduced. The MAP reading is always below ambient (non-turbo) and this is caused by the 'suck' from the cylinders and the restricted orifice at the throttle. When you reduce rpm you are reducing the sucking from the cylinders and so the MAP has the chance to recover to nearer ambient - remember MAP is ambient pressure when the engine is shut down.

2. The sideslip will have little effect on the pitot head (unless you're talking horrendous sideslip angles) but will significantly affect the static vent. If you sideslip left with the static vent on the left side you will be adding some dynamic pressure to the static pressure its reading so you should expect a decrease in altitude, a momentary rate of descent until the sideslip stabilises and a decrease in IAS as the same total pressure is being reduced by an apparently larger static pressure. However, just to muddy the water, if the static vent is high on the side of a curved fuselage it is possible that it will get a lower static pressure in a sideslip as the fuselage is working like an aerofoil and dropping the static pressure.

3. Pass - Ask me one on sport.

[Checkboard]

3. Pitot heads and toilet (actually sink) ducts are heated - no deice fluid required, so the answer is the antennae.

For a full explaination of the way the manifold pressure works read:

Manifold Pressure Sucks! (http://www.avweb.com/articles/pelperch/pelp0015.html)

then read:

Putting It All Together (http://www.avweb.com/articles/pelperch/pelp0019.html)

[dynamite dean]

thanks most helpful!