MacGregorSailors.com

Terry Chiccino wrote:Where is that fellow Frank Mighetto? I'm sure he could add something to your debate

Moe wrote:The prop is no different and takes no more time to change than a hanked foresail.

Dimitri-2000X-Tampa wrote: Uhhh, my boat is in a wet slip with the prop over water, you sure about that?

Dimitri-2000X-Tampa wrote:Not quite...try 55-68 degree water...

Mike Chapman wrote:The engine is is used to convert fuel energy to airspeed and/or altitude. The rate at which it works to convert energy is power.
Conversion of fuel to airspeed includes paying for drag to maintain airspeed, which is also what allows an airplane to maintain altitude. There are three things that a pilot can use to control the rate at which altitude and/or airspeed are gained and drag is paid for: the engine, the propeller, and the control surfaces. Engine management is concerned about the first two. Here are the main jobs of engine management:

1. Controlling the engine power output
2. Keeping the engine in good condition
3. Controlling the rate of fuel consumption

Every control related to managing the engine must have something to do with engine condition or how to convert that fuel into altitude and/or airspeed. The throttle is one of the primary controls for all three of the above jobs. In fact, throttle can often be considered to be the main control for engine power output, but it would be a mistake to think that it is the only one that matters! It would seem that there is no end to a pilot's woes.

In fact, throttle is only the main control as long as certain other conditions are fulfilled. To understand what is important for engine management, let's look at what engine power output basically is. Everybody, even your flight instructor, knows that an engine produces power by applying a torque to a rotating shaft. As it turns out, the expression of that power is directly dependent on the torque and rotational speed of the engine, measured in revolutions per minute (rpm):

Power = Torque �rpm �6.28

Torque is the force applied by the pistons at a distance around the shaft, and is provided by combustion in the engine cylinders. As a result, the torque is influenced by all factors having to do with combustion. In your airplane, rpm is influenced by the propeller, engine controls and airspeed. The rpm is important because power is a measurement of work over time, that is, it is a rate. (The 6.28 in the equation represents 2�i and is there because we prefer rpm instead of angular velocity.) If the engine moves the pistons with the same torque but at a faster rate, anyone (yes, even your flight instructor) can see that more work is being done per minute. The happy result is that you will fly or climb faster, but of course there is a price.

Throttle can have an impact on both torque and rpm, but it is clear to see that any other factor that influences torque or rpm has to be considered and controlled.

What is the throttle?

So what does moving the throttle lever actually do? In most combustion engines, all it actually does is move a little stop that blocks to a greater or lesser degree the intake manifold of the engine. The intake manifold allows the pistons to suck air into the combustion chamber. Opening the throttle (pushing the control forward, away from 0% in FB) causes the stop to block the intake less, thus allowing the pistons to suck more air. Closing the throttle blocks the intake more, hindering the air flow into the engine. So with the engine running, the engine can simply suck more air the less it is blocked. To put it simply, the more air that the engine can suck, the more torque it can deliver for the production of power. It has already mentioned that this is limited by other factors, but the important thing here is that by manipulating the throttle lever you are just telling the engine how much air it can have.

Let's have a quick peek at the other factors that influence torque and rpm. The fuel has to be burned explosively in the right way, so the mixture of fuel and air must be in the right ratio. The mixture control helps this at higher altitudes, where the second stage of the supercharger (if present) also crams more air and fuel in. The engine works best in a certain temperature range, so if it is too cool or too hot you won't get the best performance. (If things get too hot, you can also kill the engine.) The engine has the job of turning the propeller, and this is what actually converts the engine output power into altitude and/or airspeed. The propeller pitch can load or unload the engine, allowing it turn faster or slower, and this also changes the power. These are the main controls besides throttle, and although they may be considered secondary, they are unquestionably necessary in their own way.

Using throttle

It seems that for many pilots in IL-2 and FB, throttle control is simply a matter of setting the engine either at full throttle or at some point at which they know the engine won't overheat. Although this is a valid approach and certainly the fastest way to build energy and maintain high speeds, it isn't always tactically sound. It is important to have a reserve of higher engine output at critical moments. Part of this reserve comes in the form of engine temperature: keeping your engine cool enough prior to an engagment that in a pinch you can have maximum power output for a short time. You might therefore consider how to use throttle in conjunction with radiator flaps and lower rpms to keep a temperature reserve. In fact, during combat it is a good idea to look for opportunities to cool your engine quickly, even if only a little bit. It's not all that different from finding the right time to reload your weapon during a gunfight, or refuel a car during a race.

Because of the short distances involved in the Eastern Front and the lack of realistic supply shortage in the simulation, fuel economy is an underappreciated aspect of flying in IL-2 and FB. Still, if you are on a long mission, starting with low fuel or for any reason find you need to conserve fuel, throttle and rpm control are the critical controls to get maxiumum fuel economy. More on this later.

Throttle is the primary control for making power changes, especially quick ones. Situations in which throttle control requires special consideration is during takeoff, landing, and various maneuvers, especially dives, loops and low-speed, high-angle-of-attack maneuvers.

Good reading
For more information on energy in aviation, see chapter 1 of See How it Flies, by J. S. Denker.
For a more enlightening presentation of piston engines, EPI Inc. has a good and easy to understand presentation of the fundamental physical concepts.
For a fun and informative read on manifold pressure and how throttle works, see the AVWeb article Manifold Pressure Sucks! by J. Deakin.

Dimitri-2000X-Tampa wrote:

Mike Chapman wrote:The propeller pitch can load or unload the engine, allowing it turn faster or slower, and this also changes the power.