The “disappearance” of the Malaysian Airlines Boeing 777 on 8 March 2014 has provoked several possibilities. While not connected, this incident highlights that maintenance of aircraft tyres is important. Aviation tyres represent another small but high margin niche market, since it is also the most technically demanding, with the tyres on commercial jets having to sustain loads similar to large earthmovers, but at speeds more common to Formula 1 racing cars. Even so, there are three separate markets, each with specific and different requirements: commercial, military and general aviation, says Angelica Buan in this article.
Air transport has shown consistent growth for more than 50 years. However, there are increasing pressures on the industry, with changes in its structure and the composition of its fleets. This will inevitably affect the demand for tyres in terms of quantity and, more importantly, design quality.
Nevertheless, headed for a brighter horizon, market analysts suggest that the global aircraft tyre market is poised for growth.
Market research firm Lucintel’s forecast for the industry through 2020 suggests moderate growth of 3.2% that is expected to reach an estimated US$1.1 billion during the period. It says that an increased delivery of commercial, military and general aircraft will spur the demand, led also by the replacement industry.
The report explains that commercial airline passenger traffic is expected to grow over the next 20 years to 1.3 billion by 2030, yielding growth of landing and take-off planes, which consequently will increase demand for aircraft tyres due to wear and tear.
Tyre maintenance
While experts debate on what exactly caused the mishap on Malaysia’s flagship carrier, the incident has sparked a wake-up call for the aviation industry. Not only are the available technologies for the sector being put under scrutiny, but likewise the quality of aircraft maintenance is also being highlighted.
Tyres, which bear the full load of the aircraft especially during landing, seem to be a factor in the list of common causes of aviation disasters. There have been incidences of blowouts or burning tyres in airplanes, causing loss of pressure, hydraulic failure, structural damage and loss of aircraft control. During taxiing, tyres must provide a stable, cushioned ride while resisting heat generation, abrasion and wear. At take-off, the tyre structure must be able to endure not only the aircraft load but also the forces generated at high angular velocities. Landing requires the tyre to absorb impact shocks while also transmitting high dynamic braking loads to the ground. All of this must be accomplished while providing a long, dependable, reliable, service life.
Thus, an important part of aircraft maintenance is that tyres should be checked for cycles, pressure checks and undergo regular maintenance inspections. Just like the automotive sector where proper air pressure maintenance is a must for tyres, even for an airline it is required to achieve optimum performance of its tyres. It not only enhances the tyre life, landing performance but also schedule reliability.
Not only airplane tyres are vulnerable to cruising risks. According to the 2012 report undertaken by the US National Highway Traffic Safety Administration (NHTSA) on tyre-related pre-crash factors, “tyres should be in good condition, in order for a vehicle to handle safely and to use fuel economically.”
It stresses that regular monitoring as well as maintenance of vehicle tyres can prevent road disasters such as what tyre blowouts or failure (due to under or over inflation, below recommended pressure or inadequate tread depth). What these challenges conclude is that tyres must be maintained.
Taking a look inside an aircraft tyre
Aircraft tyres fall into two distinct technologies: bias (also known as cross ply) and radial. Bias and radial tyres are significantly differe nt to each other and both technologies offer operators features and benefits that might be considered agreeable for particular applications. The aircraft tyre is a composite structure of three basic materials: rubber, nylon cord and steel.
While many of the components of bias and radial tyres have the same terminology, each type has unique components reflecting the different technologies applied to design, compounds and materials.
The bias ply tyre consists of casing plies running diagonally at approximate right angles to one another. The number of plies and the angles at which they are laid dictate strength and load capacity. The latest high-performance bias ply aircraft tyres feature inter-tread reinforcing fabric (ITF). This provides additional highspeed stability, reduces tread distortion under load, protects the casing plies from damage and can act as wear indicators on retreadable tyres. According to Dunlop Aircraft Tyres (DAT), bias tyres are currently the most popular tyres fitted by the world’s fleet.
Radial aircraft tyres differ to bias aircraft tyres in that the plies all run radially from bead to bead at approximately 90 degrees to the centre-line of the tyre. Angled belt plies are laid between the tread and the top casing ply, resulting in a flatter tread and adding strength to the tyre. Radial tyres can offer low weight but tend to be less retreadable than a bias ply tyre and can exhibit weaker sidewalls.
What makes aircraft tyres unique is that they are made under stringent conditions, according to the Aircraft Owners and Pilot Association (AOPA). The Maryland-based organisation shares that every tyre is thoroughly constructed and inspected to ensure it complies with the US Department of Transportation’s Federal Aviation Administration (FAA)’s Technical Standard Order (TSO)C62. In this effect, there is no such thing as a “bad tyre”, AOPA says.
For these tyres to meet heat tolerance and required adhesion specifications, close to 100% natural rubber (NR) is required to produce the tyres, according to the Ohio-based Programme for Excellence in Natural Rubber Alternatives (PENRA), which is also undertaking R&D of alternative NR sources, such as the Russian dandelion and guayule, for aviation tyres.
Meanwhile, retreading plays a particularly important role in aircraft tyres, since they are subjected to extreme stresses. Aircraft tyres have to withstand a huge strain at speeds of over 250 km/hour and undergo retreading after around 150 take-off and landing manoeuvres. Retreading can take place up to ten times, according to the European Tyre & Rubber Manufacturers Association (ETRMA), which also says that testing procedures are naturally very stringent here, and safety takes top priority. The retreading of aircraft tyres has been the industry standard for commercial airlines for many years and is said to be a standard operating procedure for the military.
Aviation tyre market passes with flying colours
The extreme demands put on an aircraft require tyres that are highly engineered and precisely manufactured. As such, there are only a handful of manufacturers in this sector.
Among the key players in the industry is French tyre maker Michelin, which supplies bias tyres, radial tyres and tubes for the worldwide aviation community. It has an Asian base in Thailand and says it is a full service tyre supplier for all aviation markets worldwide.
Michelin has been selected as an OEM tyre supplier for Boeing’s 737 Max, the new version of the world’s top selling commercial airplane. Michelin will equip the 737 Max 7 and 737 Max 8 with its radial aircraft tyres with NZG (Near Zero Growth) technology.
NZG radial technology promises competitive advantages such as up to 50% more FOD (Foreign Object Damage) resistance; more than 20% reduction in weight compared with a bias crossply tyre, which translates into significant fuel savings for airlines; and up to a 100% increase in the number of landings compared with a bias cross-ply tyre, which means less maintenance downtime for aircraft operators.
The 737 Max 8 and 7 aircraft are scheduled to enter the market in 2017 and 2019, respectively. Current combined orders stand at more than 1,300 airplanes.
Meanwhile, BF Goodrich was an equally prominent figure in the global tyre sector, but when it divested its tyre business in 1988, Michelin acquired its aircraft tyre division the following year. Inclusive of the deal is the use of the BF Goodrich name.
Another major player is Dunlop Aircraft Tyres (DAT), the world’s only dedicated aircraft tyre manufacturer and retreader that exports about 80% of its products, with a large bulk going to the Asian market.
Birmingham-based DAT has a tyre distribution and retreading facility in China, Dunlop Taikoo (Jinjiang) Aircraft Tyres. Air carriers from Australia, China, India, Indonesia, Japan, South Korea, Philippines and Taiwan are being served by the Jinjiang facility. Confessing to weaker sales in the UK and Europe, it leverages on the strong sales of military tyres to Asia and the Middle East.
At the recent Singapore Airshow, DAT showcased its new radial tyres for regional aircraft, including the Embraer E-Jet and ATR72. The lighter weight of the tyre can offer improved landing life, it said.