Aircraft tires
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Airplane tires are the tires on the landing gear of an airplane. The aircraft tires are exposed to very strong forces during landing and especially when taking off. At the moment of touchdown, they are accelerated very quickly to landing speed. They heat up and there is heavy wear of rubber on the runway. The even greater material load at take-off is explained by the significantly higher take-off weight and the higher speed at take-off.
technology
Airplane tires are mostly tubeless. Their profile consists only of longitudinal grooves that are designed to divert water when it rains to avoid aquaplaning and to indicate wear . Fabric is worked into the tire rubber so that the tread is not destroyed by the centrifugal forces that occur at high speeds . In contrast to car tires , the visibility of fabric is therefore not a sure sign of excessive wear, and aircraft tires are generally retreaded regularly for reasons of cost .
wear
Aircraft tires, also called aircraft wheels (tires and rims), are not driven to rotate for landing , so the abrupt acceleration when contacting the runway leads to heavy rubber abrasion. During take-off, the tires are subjected to even greater forces due to the heavier weight of the aircraft and its significantly higher speed. In addition, tight curve radii on the runway create strong shear forces, i.e. forces that do not act in the taxiing direction, since the main landing gear, which bears almost the entire weight of the aircraft, is usually rigid.
Operation with incorrect tire pressure, high ambient temperatures, hard braking maneuvers at high speeds as well as fast and tight cornering (main wheels are fixed on rigid axles) lead to increased tire wear.
filling
The tires are filled with nitrogen for fire protection reasons . The brakes in the rim get extremely hot, especially during emergency braking (aborted take-off, heavy landing). The resulting overpressure in the tire is blown off by special temperature-dependent melt valves and cools the glowing brakes. An air filling, on the other hand, would rather fan a fire. Since normal air contains some water because of the humidity , it would freeze at high altitudes, at temperatures down to −56 ° C. In contrast, nitrogen only becomes liquid under normal pressure at −196 ° C and at a high altitude at −173 ° C.
The FAA has been calling for nitrogen to be used since 1990 as a number of cases had occurred in which tire components vaporized from external heat would self-ignite when the tires were inflated.
Because of the lower speeds, this does not apply to small aircraft , the tires of which are usually filled with air.
Designs and names
Aircraft wheels are called Wheels , the main landing gear tires are called Main Wheels and the nose landing gear wheels are called Nose Wheels . The mostly larger wheels of the main landing gear are arranged just behind the center of gravity of the aircraft. They carry most of the aircraft's weight, and the aircraft brakes are located on their wheel axles. In the case of the nose landing gear, the tire dimensions are smaller, since only a small part of the aircraft's weight is supported here and therefore there are usually no wheel brakes.
Maximum tire speed
The maximum rolling speed of the aircraft tires ( maximum tire speed ) can be a limiting factor in special cases.
In the case of landings without the flaps up landing (e.g. due to defects in the flaps), the landing speed can come close to the maximum tire speed .
Likewise, starting at high altitude ( high altitude take-off ; e.g. starting from high-altitude airfields - La Paz Airport 13,325 feet) may require a high take-off speed that comes close to the limit of the maximum permissible tire speed.
Examples of maximum tire speed:
- Cessna Citation I / SP (Model 501) - 165 knots
- Cessna 172 - 160 knots
- CRJ - 210 knots
- A320 - 225 knots
- A330 - 235 knots
- Concorde - 279 knots
Others
The tire wear is checked regularly. Before each take-off, the captain or co-pilot generally goes around the aircraft and inspects the condition of the tires and brakes. With daily maintenance on the aircraft, the technician in particular decides whether the tire is worn or damaged and, if necessary, has to be replaced as a preventive measure. The check for matching slip marks is part of the external visual inspection as part of the preflight check for small aircraft with tubular tires .
Aircraft tires are retreaded , which does not mean that the tires are inferior, as it is a very complex and technically careful process. The tread is planed off and the remaining carcass, the basic structure of the tire, is carefully checked by visual inspection and X-ray. A new running surface is applied by vulcanization . When the wheel is changed, it goes to the tire workshop, where the tire and the two rim halves are dismantled. The tire is sent to the tire manufacturer, the rim halves are usually washed, checked and fitted with new tires in the tire workshops of the airlines or maintenance companies.
See also
Web links
Individual evidence
- ↑ a b Jürgen Heermann: What is it like in aviation with the tires? Retrieved February 5, 2014 .
- ↑ a b Matthias founder: Highest load for aircraft tires. Retrieved February 5, 2014 .
- ↑ a b c d e f g Aircraft Tire Data Book. (pdf; 2.9 MB) (No longer available online.) Goodyear , January 20, 2003, archived from the original on September 13, 2012 ; accessed on November 7, 2012 (English). Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ FAA : 14 CFR Part 25 [Docket No. 26147; Notice No. 90-7] RIN 2120-AD37: Use of Nitrogen or Other Inert Gas for Tire Inflation in Lieu of Air.
- ↑ Highest load for aircraft tires. In: FlugRevue. August 9, 2013, accessed April 23, 2018 .
