Kick the tires and light the fires — colorful jargon but poor advice concerning safety and the service life of aircraft tires.
Modern aircraft tires are dependable and capable of dealing with weather extremes, less than stellar landings, high-speed turnoffs, long taxi routes, and significant vibrations on rollout and takeoff.
Aircraft tires are expensive, complex components that are vital to safe aircraft operations. They are dependable and reliable but not indestructible. They require a significant amount of care and maintenance from owners, operators, and maintainers. Servicing tires should be as important as the check and replenishment of engine oils and hydraulic fluids. The recommendations and requirements for tire care and preventive maintenance are straightforward and clearly stated in both OEM and FAA documentation. They provide advice and direction that should be the foundation of tire maintenance programs.
Tire care and preventative maintenance
FAA Advisory Circular AC 65-15A (Chapter 9) and AC 20-97B dated 4/18/05, initiated by AFS-306, titled “Aircraft Tire Maintenance and Operational Practices” provides recommended tire care and maintenance practices needed to assure the safety of support personnel and the continued airworthiness of aircraft. Specifically, this AC provides guidance on the installation, inflation, maintenance, and removal of aircraft tires. In addition, it provides guidance on the operational practices necessary to maintain safe aircraft operations. The AC recommends that “operators should comply with tire inspection recommendations specified in the tire manufacturer’s CMM, and consult the tire inspection advice set forth in this document.”
Both the FAA AC and the Goodyear Tire Care and Maintenance Manual stress tire preventative maintenance. Chapter Four: Preventative Maintenance in the Goodyear manual states, “Tires cannot be taken for granted on any aircraft. Tire maintenance costs will be at their lowest and tire life will be at its longest if proper maintenance practices are observed. Safe tire operation also depends on proper maintenance. Thus, preventive tire maintenance leads to safer, more economical operations.”
They specifically address daily inspections and inflation checks. The AC states that “accurately maintaining the correct inflation pressure is the single-most effective task in the preventive maintenance regimen for safe tire operations.” Both recommend that tire pressure should be checked daily or before the first flight with a calibrated gauge that is rated to read the pressure of the tires being checked.
OEM inflation procedures
Larry Rapsard, Goodyear’s North American aviation product support manager for GA Tires, agrees that the most important factor of any aircraft tire maintenance program is maintaining proper inflation pressure. His experience is considerable and as a Goodyear rep and Inspection Authorization (IA) renewal trainer, he’s seen and heard firsthand the detrimental effects of inadequate tire maintenance. Rapsard also recommends that aircraft tire inflation pressure should be checked daily because aircraft tires can lose up to 5 percent of their pressure each day.
Compensating for differences in temperature is one area where maintainers have room for improvement. For example, if pressure is checked in a warm hangar and then the aircraft is taken outside into a much colder condition and it sits for an hour or so before takeoff, tire pressure will drop.
Which is worse: over- or underinflation?
Rapsard replies that “both over and under tire inflation have consequences. Under pressure can damage the tire and over pressure can stress the wheels and landing gears. Underinflation creates faster tread wear on the shoulders and increases the stress and flex resulting in excessive heating in the tire that can lead to tire failure.”
When asked which factors have the greatest influence on the service life of aircraft tire, he says, “Tire maintenance first and weather and taxi speeds next. High taxi speeds and especially high speed turns can really stress and wear the tires.”
Asked if he had any training tips, he recommended that they always follow the Goodyear Tire Care and Maintenance Manual and call with any questions and concerns about Goodyear Aviation Tires. He also shared his list of tire tips that he includes in his IA renewal training (see “Ten Tips”).
Tire maintenance in business aviation
It is always interesting to learn how the aircraft OEMs support their customers and staff. I asked Gulfstream Aerospace Corp. if it would give its perspective on tire care and maintenance. A team of professionals that included Mark Fulkerson, technical specialist II; and Fred Karst, director, services engineering, provided a quick response.
According to the Gulfstream team, “Tire service life in general is trending up. Increased attention to maintenance, and the manufacturers’ dedication to improve tire tread compounds and manufacturing processes, have resulted in an increase in the number of landings per tire. A vast majority of “early removals” are due to FOD, not tire wear. The increased awareness to proper care and maintenance seems to really be paying dividends for everyone.”
When asked about tire care and maintenance training for its customers and staff, it partners with FlightSafety International for both customer and staff training. FlightSafety’s Total Technical Training is an aircraft systems training program for all Gulfstream aircraft delivered at its joint Maintenance Training Center in Savannah, GA.
New maintenance issues
Asked if Gulfstream is seeing any new problems in tire care and maintenance, they stated a concern about some of the current tire cleaning practices. “Everyone likes to see shiny new looking tires on their Gulfstream. The problem is with some of the chemicals used to make them shine. The harsher cleaners actually remove waxes and oils from the outer surface of the tire, which help protect the rubber from ozone attack. In addition, these products are usually applied heavily and by spraying. The overspray can lead to corrosion on the landing gear, wheels and brakes, even affecting braking performance.”
Their final recommendation was to remember that underinflation is the No. 1 tire maintenance issue and it’s 100 percent avoidable. They presented a seven-step job-aid to help with this issue:
7 Easy Steps to Proper Inflation
1. Check pressure daily when tires are cool.
2. Use dry nitrogen.
3. Allow for a 12-hour stretch after mounting.
4. Never reduce pressure on a hot tire.
5. Equal pressure on each gear.
6. Use a quality, accurate, properly calibrated gauge.
7. Consult aircraft maintenance manuals for proper levels.
The message is clear, don’t just kick the tires, service them. If you want a safe tire and a long service life for your aircraft tires, check pressure frequently and keep tires inflated to the appropriate pressure.
If you access the Goodyear Aviation Tire home page you will find two excellent training videos: “Aircraft Tire & Maintenance Training — Tire Types, Reading a Sidewall & Proper Mounting & Inflation” and “Aircraft Tire & Maintenance Training — Operating Conditions and In-Service Inspections.” Field Editor Charles Chandler is based in Michigan.