|Wheels, Tires, and Brakes: The Unloved Components|
|Written by Max Lundin|
|Wednesday, 17 October 2012 09:42|
Unlike an automobile’s, an aircraft’s wheels, tires, and brakes are rarely the object of obsession. They fall well behind many gee-whiz, budget-draining cockpit upgrades. However, these three components are as critical as ailerons and rudders during two of the most important flight moments: takeoff and landing.
These components are typically taken for granted as long as they pass an annual inspection, but (relatively) modest upgrade investments can make dramatic improvements in an aircraft’s safety and ground-maneuvering capability.
Wheel, tire, and brake manufacturers have been diligently innovating an interesting variety of products to increase the efficiency and robustness of these critical elements. Brakes infused with nitrates, tubeless tires, and specific “brake modernizations” for classic aircraft models are just a few of the products that have been on display at this year’s air shows. Although you won’t find Escalade-eqsue spinners available for an antique airplane, you can find products that might make you think twice about waiting until your aircraft’s OEM landing system starts losing air before finding a set of wheels.
Choose the Right Wheels
The selection of a wheel upgrade brings several conditional factors into consideration. Where will you be flying? How much weight must be accounted for? How much are you willing to pay? These variables may not seem overly relevant when you’ve got your eyes on a new navigation system, but the right wheel selection will make a difference.
Regarding the location of flying, wheel choice is crucial. Plan on landing in a rugged dessert runway in the Sahara? Don’t use the same wheels you trained on in Peoria when you were landing on smooth asphalt. In situations of rough landings, pilots must consider wheels with higher static load ratings to withstand more abuse. Making sure that your wheels are static rated for at least the weight of your plane is a must. Ignoring this detail is nothing short of catastrophic. However, with a few calculations, you should be well on your way to choosing an appropriate wheel.
The weight of your wheels must also be considered. If you can afford more weight and prefer wheels that will last longer, choose aluminum. Aluminum wheels fare very well against corrosion.
There are wheels for small planes that work very well and are affordable. These wheels account for a static load of 700 pounds per wheel and a kinetic energy of 72,000 foot pounds.
If weight is an issue and you are working on a larger plane, magnesium is the solution. This material handles heat far better than aluminum, making the chance of brakes overheating less likely. Magnesium wheels will shed a little bit off of your plane’s overall weight, but they are slightly less corrosion resistant and may not last as long as aluminum. At the time of this writing, one company is offering a popular 5-inch wheel and brake combo. The wheel is rated for 1,285 pounds and a kinetic energy of 118,164 foot pounds. The wheel and brake combo costs $719 for two wheel assemblies.
Tire Selection and Maintenance
Anyone who can remember flight training knows that the maxim on tires was simple, “If they’re not bald, they’re okay.” Tire maintenance is a monotonous part of any pilot’s routine, but it is a safety procedure that cannot be ignored. It’s a hassle replacing tubes and constantly maintaining tire pressure, but neglect can be fatal. Tire tubes that haven’t been properly inflated can grow folds and wear through the tube. This issue can lead to minor problems, such as occasional leakage, or serious problems, such as deflation while taxing or mid-air.
Because of such potential hazards, it’s the wise pilot who thinks past the “bald” training and puts time into tire selection and maintenance. Here’s a little-known or oft-cited factoid: Tires can be selected on more criteria than just size. Factors such as landing zone and reliability should be reviewed when purchasing and maintaining tires.
Ken Fare, vice president of Desser Tire and Rubber Co., Inc., explained some different landing situations. “Pilots landing on grass strips suffer virtually no wear to their tires, but this landing is not as common in the United States. The opposite can be said for pilots landing on commercial runways in which the landing strip wreaks havoc on the tires.”
According to Fare, most general aviation pilots use bias-ply tires with inner tubes. Pilots who perform landings on asphalt and concrete should consider buying more resistant tires than those pilots who land mainly on grass. At the moment, the tire with the most efficient technology is the Goodyear Flight Custom III. These tires include Kevlar belts inside for greater stability and longer life. The tires range from 4-10 plies for a wide variety of planes, and prices range from $250- $400.
Tubeless tires are seen much less often in aviation. These tires have a far superior lifespan, but many pilots are hesitant to make the switch. “The reason that most pilots don’t switch over to the tubeless option is the fact that it also requires the purchase of new brakes and wheels,” adds Fare. Michelin offers a complete range of tires for everything from military to general aviation aircraft and has recently released the top-of-the-line Michelin Air series. These tubeless tires are made from two proprietary rubber compounds that promise extended life, with an optimized sidewall compound to provide maximum UV and ozone protection.
Beringer offers a complete brake, wheel, and tubeless tire assembly for pilots willing to go the extra mile. The Beringer set includes two wheels with calipers and stainless steel discs, two tires (mounted and pressure tested), two axles or two sets of adaptation parts (as required), master cylinders, two fluid reservoirs, one parking brake valve (only in home-build kits), and one anti-lock regulator or pressure limiter stainless steel brake lines. The investment is around $2,800, depending on what type of plane you’re flying.
After you’ve picked out your dream tires, you need to take care of them. Ken Fare provides this list of important checks that every pilot should perform. “First off, every pilot should keep a log of tire pressure to notice deflation patterns. Pressures should be checked daily maintaining a target pressure of 100 percent to 105 percent of optimal pressure. You must also make sure that the expected pressure is adjusted based on loaded pressure, about 4 percent added to the tire’s optimal pressure (this can obviously be ignored if the plane is elevated). These pressures should be checked in moderate temperatures; those too hot or cold will influence the pressure reading.”
The main issue in the maintenance of tires comes from improper inflation. Ken said, “Under inflation is so common it’s almost an epidemic. Incorrect inflation is the most detrimental and life-shortening problem that a pilot can put his tires through.”
Brakes have seen more innovations than any other component in the landing process. From throwback brakes for antique planes to the chemically engineered brakes of Aviation Products Systems, Inc. (APS), these taken-for-granted components are receiving some much-deserved attention.
Grove Aircraft Landing Gear Systems, Inc. has a solution to bring the braking system of some antique aircraft out of the Stone Age and into the 21st century. The company’s new disc brake conversion system is FAA PMA approved and easy to install. Best of all, pilots can use their existing wheels, tires, tubes, master cylinders, and brake lines for the installation.
The Aviation Products Systems Black Steel discs and lines are a step up from the average brake system. The process by which these brakes are manufactured gives them significantly more strength and resistance to corrosion than your average brake. Dan Andrews explained, “First, our brakes are forged from aerospace steel in one piece; this avoids the problems associated with weld lines. Next, the forged steel is machined and prepped for heat treatment. The final step is our signature heat treatment in which carbon, nitrogen, and oxygen are bound to the top layer of the brake. This gives our brakes a substantially more efficient resistance to corrosion.” Dan noted that these brakes are “the only brakes in the industry that are enhanced with nitrite; this is an FAA PMA-approved process.” The brake lines are also of very high quality. The Kevlar-infused, non-metallic lines give the brake system maximum gripping and disc integrity.
Selection of new products for the “unloved components” may seem costly at first, but the investments can certainly pay off over time. If you have the cash, high-grade and tubeless tires have significantly longer lifetime than your everyday tire. The same applies to heat- and chemically treated brakes. And unlike glass cockpit technology, which seems to be changing at breakneck speed, your landing gear upgrades won’t be obsolesced by the next supplier’s catalogue.