Putting Names to the Pieces
Airplanes are made up of thousands of parts, from the simplest assemblies of sheet aluminum and rivets to the most complex system of gyroscopes or radio navigation receivers. No two airplanes are exactly alike, of course, but they all have certain very basic features in common:
•The tail, or empennage •The landing gear
Let’s examine these common components and the role they play in producing flight.
The propeller, engine, and cowling together comprise the airplane’s powerplant.
Powerplants can consist of a number of different types of engines with varying capabilities of power, durability, and capability to perform at high altitude.
Reciprocating engines, the type of engine you have in your car, are familiar to most of us, and the engines in airplanes are not a lot different from those in cars. In many ways, airplane engines are simpler than car engines. Many of them use carburetors, which in automobiles have been replaced by fuel injection systems. One major difference between the two engines is that airplane engines are typically air-cooled,
because radiators, water pumps, and the rest of the mechanical components that go along with the water-cooled engine of a car are too heavy for an airplane to carry.
An airplane with just one engine is called, quite logically, a single-engine airplane, while those with two or more engines are called twin-engine or multiengine airplanes. In a single-engine airplane, the cockpit and cabin that house the pilot and passengers rests behind the engine. In a twin-engine airplane the engines generally are mounted on each wing about a third of the distance outward from the cabin.
A common misconception is that twin-engine airplanes are necessarily more powerful than singleengine ones. Simply counting engines isn’t enough to judge engine power. The Cessna Caravan cargo plane has only one engine, while a Piper Seminole has two engines. But the Caravan’s single engine is capable of churning out 675 horsepower, while the Seminole engines combined can manage only 360 horsepower. Sometimes, one really beefy engine is a better choice than two lightweight ones.
Twin-engine airplanes can fly at higher speeds than a plane with just one engine, assuming the engines are of comparable power. However, because drag increases with speed, a principle we’ll explore in greater detail in the next chapter, twice as many horsepower doesn’t translate into twice as much speed.
Also, twin-engine airplanes offer a backup engine in case one fails. That’s reassuring to some pilots, but it must be said that flying some small twin-engine airplanes with only one operating engine is very demanding, and more than one pilot has crashed because he wasn’t up to the task.
Even some jetliners, such as the twin-engine Boeing 737, are notoriously difficult to handle in the event of the failure of one of its engines. Because of the difficult one – engine handling characteristics of some twin-engine planes, simply having two engines sometimes adds to the complications that can arise from the failure of one engine.
By the Book
The pitch of a propeller blade is similar to the pitch of helicopter rotor blades that we’ll discuss in Chapter 10, “How Do Helicopters Fly?" Simply put, the pitch is the amount of twist that designers create in the blades, which helps propel the plane much as the twist built into the blades of a room fan creates a movement of air.
Powerplants can feature propellers with a host of characteristics. They can range from the simplest carved wood-and-lacquer prop that drives some older, smaller airplanes to the massive, four-bladed metal-and-composite propellers able to shed ice and to automatically adjust theirpitch during flight. These “constant speed” propellers turn faster or slower during different segments of flight, almost like an airborne version of an automobile transmission.
The small airplanes that most private pilots use for flying lessons are equipped with the simpler fixed-pitch propellers. Their shortcomings in not being able to adjust to different speeds during flight—fastest rotation during takeoff and slowest rotation during cruise—is more than made up for in simplicity.
When a student pilot is learning how to control and maneuver an airplane, simplicity in a prop becomes a virtue. A fixed-pitch eliminates one thing the pilot must think about. Later, when he is more experienced, the pilot can more easily transition to a more complicated airplane, including one with an efficient constant-speed propeller.