Proper torque is essential when installing aircraft bolts. With their threaded body or “shank,” bolts offer a convenient way to fasten parts. You can drive a bolt through two or more parts to secure them together. When used to assemble aircraft parts, however, proper torque is required.
The Basics of Torque
Torque is a measurement of rotational force. High torque indicates a strong rotational force, whereas low torque indicates a weak rotational force.
Torque takes into account the total applied force and the perpendicular distance from the point at which the turning or rotation began. It’s essentially the force multiplied by the distance. Applying 10 pounds of force using a 1-foot wrench results in 10-foot pounds of torque.
In aviation, torque is typically measured in one of the following:
- Inch-pounds
- Foot-pounds
- Newton-meters
The Importance of Proper Torque
Aircraft bolts must be tightened with the proper torque. A typical airplane has anywhere from a few thousand to hundreds of thousands of fasteners. if a bolt isn’t tightened correctly, it could pose a serious risk to the airplane’s integrity.
If a bolt is too loose, it may work its way out from vibrations. Airplanes vibrate during flight. Over time, these vibrations can cause loose bolts to come out of the holes in which they are installed. If a bolt is installed too tightly, conversely, the threads may become stripped or fatigue cracks may develop in the surrounding material. Problems such as these can often be avoided by using proper torque.
How Torque Is Controlled
How do aircraft engineers and mechanics control torque exactly? One of the most common solutions is a click-style torque wrench. They feature a spring-based mechanism that clicks once the desired torque has been reached. Engineers and mechanics can set a click-style torque wrench to a specific torque, after which they can use the wrench to install the bolt. The clicking noise indicates that the desired torque has been reached.
There are also beam-style torque wrenches. When turning a beam-style wrench, a pointer will move across a scale to indicate the torque. Beam-style torque wrenches are simpler and less expensive than their click-style counterparts.
Digital torque wrenches have become increasingly popular in recent years. These highly precise tools feature sensors that measure the applied torque and display it on a screen. Some digital torque wrenches have other high-tech features, such as light-emitting diode (LED) lights and torque alarms.
