Three basic questions on complex aircraft: do I have this right?

1. throttle - controls how much BOTH air AND fuel are getting into the cylinder. Or does it just control how much fuel gets into the cylinder?
2. propeller - controls how fast the prop rotates
3. mixture - controls how much air enters the cylinder

Thanks.

 

1 Yes

2 No

3 No

see https://en.wikipedia.org/wiki/Aircraft_engine_controls

34 minutes ago, qqwertzde said:

1 Yes

2 No

3 No

see https://en.wikipedia.org/wiki/Aircraft_engine_controls

I read the link. Very informative. Thank you. I hope you don't mind follow-up questions.

1. How is the fuel-air mixture ratio calculated at take-off? Is it fixed or is it calculated based on the airport elevation?
2. Pushing the prop lever forward increases the pitch angle of the propeller blades? Or does it decrease it?
3. When air pressure declines at higher altitudes, my understanding is that in a turbo engine plane some of the exhaust air from the cylinder is recycled to provide more air to the cylinders. Assuming the mixture is constant, in a turbo engine plane the speed then is not affected, whereas in a non-turbo engine plane the speed will decrease (because now there is less of both air and fuel)?

The prop levers sometimes travel the reverse of normal (especially in older planes). 

Usually, pushing prop lever forward decreases the prop pitch. Which means it pulls the plane through the air a lesser distance for each revolution of the blades. Which is easier on the engine and increases torque. Which acts like using a lower gear in an automobile: torque is increased and speed is decreased. Used in cars for instance when going up steep hills which requires more torque. But speed is decreased when you shift down to that lower gear, even as your ability to climb is increased. 

On takeoffs, you need full torque, just like going uphill in a car.

The way I learned to keep it straight was to think like low gear and high gear when driving a car. In low gear in a car, the RPM gauge needle moves to a higher number. 

 

In a car, when you shift to a lower gear the tachometer RPM jumps to a higher number and speedometer jumps down to a lower number. Assuming you have a nice sports car with lots of nice round dials which God invented to save us from the Devil's glass screens. 

One of my favorite forum posts was (I think it was Birdguy) saying he hand to pull over off the road and learn how to read the information on the big glass screen in a new car. 

10 minutes ago, Fielder said:

Usually, pushing prop lever forward decreases the prop pitch.

Hmmm.... higher torque mean higher pitch (or higher angle and lower rpm which takes a bigger bite of the air)?

2 hours ago, Matt Sdeel said:

1. How is the fuel-air mixture ratio calculated at take-off? Is it fixed or is it calculated based on the airport elevation?
2. Pushing the prop lever forward increases the pitch angle of the propeller blades? Or does it decrease it?
3. When air pressure declines at higher altitudes, my understanding is that in a turbo engine plane some of the exhaust air from the cylinder is recycled to provide more air to the cylinders. Assuming the mixture is constant, in a turbo engine plane the speed then is not affected, whereas in a non-turbo engine plane the speed will decrease (because now there is less of both air and fuel)?

1. I don't know how it is calculated, but it mainly depends on the airport elevation. For most airplanes, keeping mixture rich until 3000' should do fine. Then it gradually has to be lowered to retain optimal engine performance. You can monitor your airspeed, EGT (exhaust gas temperature), or you may have a dedicated gauge (like the Milviz C310R) to find the right setting.

2. Prop levers full backward means that the props are "feathered", i.e., the blades are parallel to the wind. This is needed if an engine fails to minimize drag from the blades. The more forward you push the levers, the more you increase the pitch, which creates more torque. And torque is what propels you forward, so you want that usually as high as possible without going into any red band in the engine gauges.

3. Turbo engines don't really have a mixture gauge. The purpose of the turbine is to compress the airflow so much that the decreased air density at higher elevations is not a factor anymore. Turboprops instead have a condition lever, which normally only has three positions: cut-off, low (for ground operations), and high. Since the turbine compresses the air, turboprops can fly much higher, and therefore also (usually) much faster.

Peter

8 minutes ago, qqwertzde said:

Turbo engines don't really have a mixture gauge.

By a mixture gauge are you also referring to the absence or presence of the red lever? The PA-28 Turbo Arrow has that red lever.

3 hours ago, Matt Sdeel said:

Hmmm.... higher torque mean higher pitch (or higher angle and lower rpm which takes a bigger bite of the air)?

Perhaps I should have used 'thrust' instead of torque.

In a 3 lever plane (black, blue, red) :

Blue forward = high rpm, high thrust, low pitch, low speed. You want high thrust for takeoffs. Each revolution of the prop pulls the plane through the air less because of that low pitch. This obviously gives you way more pulling power, more thrust to accelerate and lift the plane from the runway.

Blue backward = low rpm, low thrust, high pitch, more speed. You don't need a lot of thrust to cruise, you do want this increased speed and the better gas milage. The high pitch is pulling the plane further each revolution of the blade = more speed.

The mantra is : Low pitch High RPM.  High pitch is Low RPM.

It's very similar to a manual shift automobile. Low gear to get rolling, high thrust and low speed. High gear to cruise, you don't need all that thrust because you aren't accelerating. You do want the resulting higher speed and better gas mileage. Your tachometer hand will fall drastically to a lower RPM when you shift into high. 

 

8 hours ago, Matt Sdeel said:

By a mixture gauge are you also referring to the absence or presence of the red lever? The PA-28 Turbo Arrow has that red lever.

Yep.Some turboprops have no (red) condition lever. If I recall correctly, the TBM 930 does not (I don't fly it often, so don't sue me if I am wrong 😉 ). For those with three levers, the red lever usually changes engine parameters a bit for noise reduction and lowering fuel consumption on the ground. However, it varies a bit in general, see https://www.skybrary.aero/articles/condition-lever