Multi questions...

[braidkid]

I'm getting ready for my multi and have a few questions. I've stated the question and the only answer I can think of...any help is greatly appreciated.

1) If the cylinder head temp and oil temp approach the caution range, what can be done to assist in cooling?

Open cowl flaps. Decrease engine RPM

2) Why does manifold pressure decrease approximately 1” every 1000’ during climb?

Because the air is less dense with altitude. Therefore, the engine is less efficient.

3) When an engine is inoperative or feathered, what indication will be observed on the manifold pressure gauge?

When an engine is inoperative or feathered the manifold pressure gauge should read lower than normal.

4) Why is the manifold pressure gauge not necessarily a good indicator in determining an inoperative engine?

I have no idea??

 

[jtrain609]

A manifold pressure gauge is not a good indicator of a dead engine because it will show the ambient pressure when the engine is not running. That's how I understand the thing at least, and that's why it reads whatever the current barometric pressure is before you start the engine.

Cheers


John Herreshoff

 

[ILSstud]

When an engine is inoperative or feathered, it should register the approximate atmospheric pressure at altitude or if you are on the ground, it will register the current altimeter setting.

The manifold pressure gauge is not necessarily a good indicator in determining an inoperative engine because if the approximate cruise setting (say in the duchess 20'') is the approximate atmospheric pressure, you will be unable to determine which engine is inop. To determine what engine has failed simply see which direction the ball in the inclinometer is leaning to. If it goes to the right (left engine has failed); if it goes to the left (right engine has failed). Remember STEP ON THE BALL, then place your foot that is not pushing the rudder "dead" on the floor. That way it is very easy for you to properly identify which engine has possibly failed. Then follow your checklists to verify that you are correct

 

[jtrain609]

Word

 

[EatSleepFly]

[ QUOTE ]
The manifold pressure gauge is not necessarily a good indicator in determining an inoperative engine because if the approximate cruise setting (say in the duchess 20'') is the approximate atmospheric pressure

[/ QUOTE ]

If the atmospheric pressure is anywhere near the MP that a light twin cruises at (or even redlines at for some), the weather is likely going to be veeerrrrry f^%#*d up.

Although at altitude, they would be close.

 

[EatSleepFly]

[ QUOTE ]
When an engine is inoperative or feathered, it should register the approximate atmospheric pressure at altitude

[/ QUOTE ]

Not necessarily...

If the engine is inoperative and the prop is still windmilling, it will continue to show lower than atmospheric pressure until it stops (or maybe slows beyond a certain RPM, I'm not sure). The prop is turning, so the pistons are going up and down. When they are going down on the intake stroke they are still creating lower pressure in the intake manifold which will register on the MP gauge. The fact that combustion is not taking place is irrelevant.

 

[ananoman]

For a hot engine, you want to increase airspeed (level off from climb), enrichen the mixture, open the cowl flaps, and reduce power if possible. Unless you lean improperly, the engine should not overheat in level flight, usually climbing at high power settings is what heats up the engine.

There is really not an engine gauge that gives good, instant indication which engine has failed. EGT is probably the best option , but on an aircraft with only 2 engines, you should not need to look at a gauge to tell which engine quit. The yaw and heading change should be enough of a clue.

As others have said, the MAP gauge is not a reliable indicatior of engine failure. It will often read close to the same as the good engine. Once feathered it will read ambient pressure.

 

[ILSstud]

oops sorry...should have read "inoperative AND feathered"

 

[SUSPilot]

[ QUOTE ]
When an engine is inoperative or feathered, it should register the approximate atmospheric pressure at altitude or if you are on the ground, it will register the current altimeter setting.



[/ QUOTE ]

actually it will not read the altimeter setting on the ground unless you are at sea level, becuase the altimeter setting is used in respect to sea level being zero. If you are higher than sea level, and the engine is shut down AND feathered in the air, or not turning on the ground, the manifold pressure guage will read the outside barometric pressure not corrected for sea level which on a standard day will decrease one inch for every 1000 feet above sea level.

 

[bluelake]

here's a good time to visit John Deakin's AvWeb article "Manifold Pressure - It Sucks"

http://www.avweb.com/news/columns/182081-1.html

 

[cime_sp]

If th engine is feathered it will show ambient pressure....example

Altimeter setting = 30.00
Cruise Altitude = 3,000'
Normal power setting for maneuvering = 18", 2300 RPM
Feathered and stopped engine will show about 27" (1"/1,000 ft)

If the engine were still windmilling, it would show nearly the same as the operating engine....if anything it would probably show slightly higher MP because the engine is turning slower

EGT guage is a good double check though...the dead engine will obiously go towards the low end. But as another poster said, in VMC conditions, you should have NO problems noting which engine is dead

 

[braidkid]

Thank you so much for all your comments. They were very helpful especially the article.