This is not what a CFI wants to hear when the learner is doing the preflight inspection. The learner was looking at the nosewheel of the Cessna 150, specifically, at a scalloped pattern on the side of the tire. She’d never seen this before—and frankly, in my more than 30 years of flying, neither had I. But I knew ugly when I saw it. 

One of the things I teach my learners is not to be embarrassed about asking for help, or asking a more experienced pilot or mechanic a question about something you find during a preflight. With this in mind I took a photograph of the tire with my smartphone and sent it to an A&P/IA with the text question, “OK to fly?” although I had a pretty good idea what the reply would be.

And I was right. 

The reply came back immediately: NO. A few more lines followed, mostly caveats about tires blowing at awkward moments and inquired if I needed help. I quickly explained the situation and ended with the phrase, “Decision: no-go.”

Although disappointed we could not fly, I was happy the learner had the opportunity to see a less-than-standard tire, because it allowed us to have a discussion about aircraft tires. They take a beating at a flight school, so it’s important for the learner to know what is normal and what is not. There is a reason that the checklist includes “check tires for proper inflation, damage, and flat spots.”

Negative transference—that is, applying information from something similar but different—can bite a pilot, especially with tires. One of the big mistakes made by fledgling pilots, especially those who are renting aircraft, is that they think airplane tires are the same as automobile tires, according to Randy Hedrick, customer support engineer for Michelin Tire. 

“Car tires have a wear bar. Aircraft tires don’t,” Hedrick said, noting that the flight students may not realize the aircraft tires are worn to the point of impending failure or more commonly, improperly inflated. 

“We recommend doing a pressure check before the first flight of the day. It’s normal for tires to lose pressure during the day, [so] losing up to 5 percent in two to four hours is acceptable.”

Renter pilots often don’t check the pressure of the tires as part of the preflight inspection. Improperly inflated tires can cause vibration—and that will definitely get your attention during ground operations, especially during takeoff and landing. 

Can You Change the Tire?

Most flight schools keep spare tires stocked, especially when they are also an FBO and have a visiting aircraft in need of maintenance. If they have a replacement tire, you have the tools, and it is your aircraft, so the FARs permit you to change the tire. But please don’t try to do it unless you have the proper tools and know how. 

Every mechanic contacted for this story said the same thing: It’s best to have someone with experience (like an A&P) show you how to do it at least once. There are more steps involved when changing an aircraft tire than there are when changing a tire on a bicycle or automobile, and different techniques and the right tools are a must.

For starters, you need to chock the other tires, find the jack point on your aircraft, and then have some blocks of wood to balance the jack. You have to be careful as you jack up the airplane and reposition the jack because the tire may move in.

Once the airplane is jacked up and the tire off the ground, you have to cut the safety wire. This releases the bolts that hold the brake pad in place, allowing you to take the wheel apart. That’s right—take the wheel apart.

The inner tube can take on a life of its own. Be very careful about the valve stem and be sure the tire tube is not kinked or folded. Installing the tube, whether new or used, involves talcum powder to guide in the inner tube. You have to be careful not to allow the tube to crease or fold, because that can introduce uneven wear, which you will feel when the tire rotates during ground operations.

These are just a few of the things we were warned about. There are many more steps to it, and even if you’ve done it before, you’ll probably want your A&P to check your work. You also need to log the tire change in the aircraft maintenance log.

Even putting air in the tire is not as straightforward as it is with cars. With automobile tires you find the pressure printed on the sidewall. On an airplane, that information is printed in the aircraft’s pilot’s operating handbook or airplane flying manual. Be able to find that information, noting the pressure for the nosewheel and main gear are usually different. 

Always verify those numbers before you ask someone to put air in the tires.

Flight School Tire Challenges

The flat spot is the most common issue found on flight school tires. This is caused by slamming on the brakes and locking them up.

Flat spots can be a challenge to see if the aircraft has wheel pants, so be ready to gently roll the aircraft forward by hand and check the tires all around during the preflight inspection. If the chords are showing through the tread, it’s usually a no-go situation. But there are some pilots who want to make the flight so badly that they get hit with an invulnerability stick and take the aircraft out anyway.

Please don’t be this person.

When you report an issue with a tire to the flight school you expect the maintenance crew to take a look at it. Most of them are good about this, as the aircraft doesn’t make any revenue when it is sitting on the ground.

If you are skeptical that the tire has been inspected, you can do the old chalk trick – make a line on the tire with chalk. If the tire is inspected the chalk line should disappear as the tire rolling over the ground will erase the mark. If the chalk line remains, the tire was not checked.

The post What You Need to Know About Tires When Learning to Fly appeared first on FLYING Magazine.

Extreme heat and stress are all part of an airplane tire’s lifespan, and each aircraft must have the right number of wheels to support its operations. So how many wheels do airplanes have, and how do manufacturers determine the amount needed? This article will answer these questions and more, giving you a fully comprehensive understanding of the wheels and other components that make up the landing gear.

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How Is the Number of Wheels Determined?

The size and makeup of landing gear on an aircraft is determined by the airplane’s maximum gross weight. Airplane tires need to sustain the airplane’s weight while the aircraft is stationary and distribute its weight evenly when the wheels touch down on the runway surface during a landing. The runway will be damaged if it’s forced to handle a concentrated amount of weight at high speed–another reason why runways are designed to handle certain loads. 

Do Any Airplanes Have 4 Wheels?

Most commercial, transport-category airplanes have two wheels within the nose gear assembly, and each main gear assembly may carry two (or more) wheels as well. That is a total of six airplane wheels, which is a rough average. 

A single landing gear unit can have multiple wheels but counts as one assembly. Therefore, it’s possible to have four assemblies, but they do not necessarily have four individual airplane tires.

For light aircraft, one wheel comprises the nose gear, and there’s also one wheel within each main landing gear assembly.

So why doesn’t an airplane have four landing gear assemblies, like a car or truck? That’s because this is unnecessary for an airplane, as pilots tend to turn an airplane very slowly while on the ground, and the airplane only moves straight ahead during takeoff. An extra landing gear assembly would only add unnecessary weight.

How Many Wheels Does a Boeing 747 Have?

There are a total of eighteen airplane wheels on a Boeing 747. There are four main landing gear assemblies—two on each side of the jet and each containing four wheels—with two aircraft tires in the single nose-gear assembly. 

What Are Airplane Wheels Made of?

Airplane wheels are composed of conductive rubber to absorb any electricity generated by the friction between the tire and the runway. Flexibility is an important element of the tire’s makeup, and Kevlar, a strong, lightweight, heat-resistant, pliable plastic, is often used for transport category airplane wheels. 

The tires are generally made up of three rubber layers, each laid in a different direction to strengthen the airplane tires and increase their traction. They also have a layer of special aluminum steel reinforcements to keep the airplane tires from losing tread or coming apart during a landing.

Constructed into the grooves of the airplane tires are conducting strips that dissipate built-up electric charges. This is to avoid any sparks that would result from the friction and potentially ignite the airplane’s fuel supply. 

These tires are often filled with non-flammable nitrogen gas to eliminate corrosion of the metal parts within the transport category airplane’s structure. Nitrogen gas also does not oxidize and destroy the rubber comprising the airplane wheels.

Can an Airplane Land with a Flat Tire?

Flat airplane tires are rare occurrences but can happen if a wheel is under or overinflated. Because most transport category airplanes have more than one tire as part of the landing gear, it is possible to land the plane safely with a flat. 

Another reason airplane tires are not likely to blow out during a landing is the amount of air pressure pumped into them. They are six times more inflated than a car tire. This pressurized air keeps them strong, and the airplane wheels don’t suffer immense amounts of damage, although they take a beating regularly. 

Why Are Plane Wheels so Small?

Compared to the size of the fuselage, airplane wheels are relatively small in size. However, smaller airplane tires still support the aircraft during landing effectively by distributing the weight evenly amongst them. Larger airplane tires would also weigh more, causing the airplane to use more fuel, and therefore costing the operator (such as a flight department or airline) more money. Engineers make it their mission to make the tires as small as possible while retaining an adequate degree of safety. 

Types of Airplanes and the Number of Wheels They Have

Now that we know why tires are so important to the aircraft structure and what makes them so strong, let’s look at a few different types of airplanes and the number of wheels needed to operate them safely.

Airbus

Airbus is the world’s largest aeronautics and space company and for the moment leads the industry in commercial airliner orders. They have been designing commercial, defense, space, and surveillance aircraft for fifty years, along with helicopters. Airbus’s large commercial airplanes transport people worldwide; therefore, safe airplane tires are a necessity.

• Airbus A330: 10 wheels or tires
• Airbus A340-200/300: 12 wheels or tires
• Airbus A340-500/600: 14 wheels or tires
• Airbus A350-900: 10 wheels or tires
• Airbus A350-1000: 14 wheels or tires
• Airbus A380: 22 wheels or tires

Boeing

The Boeing Company is the biggest airline OEM in the United States. They manufacture airplanes that support U.S. air carriers and conduct business in more than 150 countries. They deliver hundreds of airplanes each year to their customers.

• Boeing 717, 727, 737: 6 wheels or tires
• Boeing 747: 18 wheels or tires
• Boeing 757, 767: 10 wheels or tires
• Boeing 777: 14 wheels or tires
• Boeing 787 Dreamliner: 10 wheels or tires

Light Aircraft

A wide range of airplanes serve general and business aviation for private or corporate flights, as well as transporting freight and passengers. The maintenance of these airplanes usually falls under the pilot’s responsibility, and if that’s you, make sure your airplane tires are ready to carry you to your destination safely. Here are a few popular models, along with their tire count.

• Gulfstream G650: 6 wheels or landing gear
• Dassault Falcon 7X: 6 wheels or landing gear
• Learjet 70/75: 5 wheels or landing gear
• Beechcraft King Air 350i: 5 wheels or landing gear
• Embraer Phenom 100: 3 wheels or landing gear
• Cirrus SR22: 3 wheels or landing gear

COMAC

The Commercial Aircraft Corporation of China (COMAC) is China’s largest aerospace manufacturing company. China could potentially become the world’s largest aviation market and the country’s aerospace manufacturing complex is busy designing aircraft to keep up with the demand. 

• ARJ21: 6 wheels
• C919: 6 wheels
• CR929: 6 wheels

Airplane Wheels Are the Unsung Heroes

Airplane tires can withstand huge amounts of pressure and come in contact with the runway 500 times before they need to be re-treaded. The technology that goes into constructing airplane wheels is designed to keep passengers and cargo safe as they travel through the skies. 

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The post How Many Wheels Do Airplanes Have? appeared first on FLYING Magazine.

We have all been there on a preflight: You come to the point in the checklist when it calls for a check of the tire pressure. Be honest. How many times have you just eye-balled the tire and considered it safe for flight?

Most of the time, that’s been good enough.

But there have been countless incidents—and a handful of accidents each year—that stem from runway excursions. Many of them come down to a tire failure of some kind, and most likely a few would be prevented with foreknowledge of inadequate tire pressure.

Beringer-Aero has built upon its knowledge of wheels, brakes, and landing gear for light aircraft with the SensAir tire pressure monitor and app. The French company—with its US headquarters and service in Greenville, South Carolina—built its reputation serving high-performance cars and motorcycles beginning in 1985, but transitioned over to focusing exclusively on aircraft in 2009.

According to company founder Gilbert Beringer, “Using technology similar to automotive TPMS systems, we have developed a balanced, lightweight module that can fit into any Beringer wheel and communicate with your smartphone.” And it gets you past the hurdles introduced by wheel pants, restricted movement in the parking area or hangar, and lack of time.

Installation comes readily, said Beringer: “Split your modular Beringer wheel and slip the sized and balanced band on. Then reassemble. The encapsulated batteries last for two to three years; change them when you change tires.”

A single wheel assembly weighs 3.3 ounces, including the batteries.

Once installed, the app will show the tire’s pressure and internal temperature, in degrees F or C.

The STC for experimental and light sport aircraft is pending approval, and the kits will fit all 4-inch, 5-inch, 6-inch, and 8-inch Beringer wheels.

The company produces wheel kits for a wide range of aircraft makes and models, including:

• Piper
• Cirrus
• Van’s
• Kitfox
• CubCrafters
• Just

The post Tire Pressure Monitor Puts Data to a Smartphone App appeared first on FLYING Magazine.