How Do You Know When an Aircraft Tire Needs to Be Replaced

In this commodity—the first in a series describing diverse preventive maintenance deportment—A&P Jacqueline Shipe goes through the entire process of removing and reinstalling an aircraft tire.

All aircraft owners will periodically have to replace a tire. Even planes that don't get used much eventually crave tire replacement due to dry rot and sidewall cracking of the condom.

Tire replacement is one of the items the FAA considers preventive maintenance that owners may legally perform on their shipping. Changing a tire isn't mechanically complex, but information technology does require the owner to use some caution.

Proper aircraft jacking procedures have to be used, and if the plane is jacked outside, first check the weather condition conditions to ensure that the wind is non going to exist also high. Major damage can be done to the airframe structure whenever a plane falls off a jack.

Once the plane is properly jacked, the removal of the wheel assembly can brainstorm. (For information about shipping jacks and proper procedures, have a look at Shipe's "Aeroplane Maintenance for the DIYer: First Steps" in the May 2016 effect. —Ed.)

If the plane is equipped with wheel pants, the wheel pant has to be removed first. This is commonly a pretty straightforward process, simply be certain to keep the removed screws and bolts identified as to which receptacle they came out of, because sometimes several different diameters and lengths are installed.

Removing a main bike

The next footstep is to remove the outboard brake backing plate (if the wheel is a main bike) so that the brake disc volition exist free to slide off the axle with the cycle assembly.

There are two or more bolts that connect the backing plates to the caliper that have to exist removed. They may or may not take safety wire on them, depending on the design.

Once the outboard brake is off, the next step is to deflate the tire by removing the valve cadre. It is important to do this before removing the big beam nut, because if whatsoever bolts holding the wheel halves together are loose or damaged, the bicycle assembly could accident apart every bit the axle nut is loosened.

Almost axle nuts have either a clevis pin with a modest cotter key or a single large cotter fundamental to continue them from bankroll off.

When the axle nut is removed, the wheel assembly volition slide off. Some manufacturers use a spacer that may or may non slide off with the bicycle; care needs to be taken to ensure it doesn't get misplaced.

Removing a nosewheel

Nosewheels commonly have a removable axle that slides through the bike and nose fork. This is generally held in identify with a single long bolt and lock nut that secures two cup-shaped retainers.

Nosewheels are fairly easy to remove unless the steel beam is corroded and frozen in the aluminum fork, in which example the axle has to exist driven out. A wooden dowel should be used to drive out the axle because information technology won't gouge or mar the aluminum fork.

Breaking the tire dewdrop

Once the wheel is removed, the tire bead needs to be broken from the rim of the cycle halves. Get a slice of plywood to lay the cycle on (and then it won't go marred), and then forcefully push the tire down all the mode around. It will eventually pop down off the rim. This process has to be repeated on the reverse side as well.

Some folks utilize flat blade screwdrivers or pry bars to pry the tire abroad from the wheel, but this tin can issue in major scarring of the relatively soft cast aluminum that the wheels are made of.

If the bead is actually stubborn and just won't break loose, y'all may have to enlist the aid of a mechanic and a bead-breaking tool made specifically for the job.

Splitting the wheel and removing the tube

Most wheel assemblies are two-piece, and the wheel halves are split by removing the through bolts and nuts belongings them together. After separating the wheel halves, the tube can then exist removed from the tire.

Some mechanics replace the tube with every tire alter, and some re-employ the old tube every bit long every bit it looks good. Tube manufacturers recommend e'er replacing tubes when replacing a tire because they stretch while in use.

Once an old tube is removed, it tin can be barely inflated—just plenty to expand it a lilliputian—so the unabridged exterior tin be inspected. Tubes with deep wrinkles or that take signs of damage or age, such as dry out rot cracks around the valve stem, should always be replaced.

When ordering a replacement tube, pilots may want to get the type that doesn't lose air, such equally a Leakguard or Airstop inner tube. They do reduce the frequency of having to air up the tires by quite a bit, especially if they are serviced with nitrogen instead of compressed air.

Reinstalling the tube

The outside of the tube and inner part of the tire need to be coated in talcum pulverisation before installing the tube. The powder keeps the tube from sticking to the sides of the tire and helps forbid chafing.

The tube should accept a balance marker on it. This needs to exist aligned with the balance mark on the tire, which is by and large a carmine dot.

In the absence of a balance mark on the tube, align the valve stem with the cherry dot. This matches the heaviest part of the tube with the lightest part of the tire and makes it much easier to balance.

Reassembling the wheel

Once the tube is installed in the tire, the wheel halves (and the brake disc, if it is a main wheel) can be assembled together. Slightly inflating the tube a tiny amount helps to ensure it won't be pinched between the wheel halves.

Place the bike halves together so the bolt holes marshal. The bolts tin then be slid through and the washers and lock nuts installed. Lock nuts should have enough tension on them then that they cannot exist tightened by paw, otherwise they should exist replaced.

The correct torque should exist observed when assembling the bicycle halves. These are made of bandage aluminum and are potent, just over-tightening the nuts and bolts can atomic number 82 to dandy.

Balancing the tire

A wheel balancer is a fairly expensive tool to purchase, and tires aren't commonly replaced on an individual airplane often plenty to merit owning one for most folks. Large imbalances in a bicycle associates can be detected by mounting the wheel on the beam and installing the axle nut, but leaving it slightly loose so the wheel rotates freely.

Once the tire is spun a few times, if the same spot always ends up coming to rest on the bottom, this indicates an imbalance and weights will demand to exist added to the light side. Using stick-on atomic number 82 type weights purchased from an aviation parts warehouse or automotive store, add enough weight so that the bike comes to a cease in random places as it is spun freely on the axle. The balance is more disquisitional on the nosewheel associates because it will cause a shimmy if there is even a slight imbalance.

Reinstalling the bike on the shipping

Once the bike is balanced, it is prepare for installation. The axle should be wiped off and greased, and any corrosion should be removed with an abrasive cleaning pad.

A general-purpose Scotch-Brite 7447 pad (maroon color) works well and can be purchased anywhere automotive paint products are sold. These pads are abrasive enough to clean off rust, but not and then annoying so as to scratch the metallic. Use elbow grease to scrub the axle until it is shiny.

The nosewheel axle is prone to rusting internally. Any rust should exist removed here as well, and the internal part of the axle should be either painted with a rusty-metallic primer, or coated in LPS 3 or other corrosion-inhibiting compound.

During the final installation, the axle nut needs to be tightened enough so there is no complimentary play detected as the tire is grasped and pushed inboard on the tiptop while pulling outboard on the bottom, or vice versa. (This checks for side-to-side free play, and in that location should be none.)

The wheel should spin somewhat freely, only there needs to be a slight amount of tension on the axle nut. If the nut is too tight, the bike won't spin much at all past manus, and the bicycle bearings volition be more likely to neglect from having too much of a pre-load placed on them.

In one case the correct tension is achieved, align the cotter fundamental hole in the beam with the opening in the nut and install the cotter cardinal. Be certain to curve the edges of the cotter central in such a mode that they won't get entangled in the valve stem or rub on the wheel bearing servant.

After the wheel is secured in place, the valve stem should be removed and the tube inflated and deflated ii or iii times to remove any wrinkles. Then the valve stem can be reinstalled and the tire inflated to its proper pressure. (Right tire pressures are found in the POH.)

Later on the outboard restriction and/or wheel pant are reinstalled, the tire change will be complete. The aircraft owner will as well have the satisfaction of having completed the work himself (or herself)—and volition have hopefully have saved a few bucks in the process.

Jacqueline Shipe grew upward in an aviation domicile; her dad was a flying instructor. She soloed at historic period 16 and went on to get her CFII and ATP certificate. Shipe attended Kentucky Tech to obtain her A&P license. She has worked as an airline mechanic and on a variety of General Aviation planes, and has logged over 5,000 hours of flight instruction fourth dimension. Send question or comments to .

Resources >>>>>

Leakguard butyl inner tubes by Aero Classic

Aircraft Spruce & Specialty

Airstop® aircraft inner tubes

Michelin Due north America Inc.

LPS 3 Premier Rust Inhibitor

ITW Pro Brands

How Do You Know When an Aircraft Tire Needs to Be Replaced

Source: https://www.piperflyer.org/maintenance-technical/item/1155-airplane-maintenance-for-the-diyer-changing-a-tire.html

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