Typically, pilots operate aircraft on the runway at speeds close to 55.5 km/h, but this can be significantly reduced in adverse weather conditions and low visibility.
Airports never post speed limit signs because how fast an aircraft can taxi on the runway depends on the pilot, the airline’s procedures, and the weather conditions. In general, the maximum speed allowed by airlines for pilots on the runway is 55.5 km/h. This speed applies only to straight runways that are clear of other aircraft. Pilots can quickly reduce their speed from this level when applying maximum braking, according to Simple Flying.
Pilots typically taxi aircraft at speeds close to 55.5 km/h. (Photo: Pilot Institute).
Even when taxiing at a speed higher than permitted, pilots usually maintain a ground speed slightly below the maximum. Particularly during taxiing for takeoff, flight attendants move around the cabin to conduct safety checks and perform various other tasks; thus, a slower speed is more appropriate if sudden braking is necessary. Additionally, runway speed is one of many parameters monitored by the airline’s Flight Operations Quality Assurance (FOQA) program. This program alerts the safety department if a pilot exceeds the airline’s limits for more than a few seconds for any reason. This is why pilots might taxi slightly longer than the maximum speed allowed.
Another reason to keep the aircraft’s taxi speed below 55.5 km/h is to maintain brake temperatures at a cool level. This is especially important after landing in summer. Brakes absorb significant momentum upon landing and convert it into heat. Excessive use can cause the brakes to heat up, which could delay the departure time of subsequent flights if the aircraft needs to turn around quickly and the outdoor temperature is high. This is because brakes must cool down to a minimum temperature before takeoff.
55.5 km/h is the typical maximum speed for taxiing on a clear day with good visibility. Poor weather conditions may force pilots to decrease their taxi speed. In icy or snowy runway conditions, the speed limit is restricted to 18.5 km/h or lower. Similar to any other wheeled vehicle, aircraft can skid (primarily the front wheels during sharp turns). For this reason, 18.5 km/h is the fastest speed a pilot can taxi an aircraft on a runway covered in ice or snow or in low visibility due to fog.
In addition to lower speeds, airlines also require pilots to taxi aircraft using both engines in wet or icy conditions. Operating both engines helps maintain better control of the aircraft. For example, if only the left engine is operational, turning left requires more thrust than turning right because the left engine is within the turn radius. The thrust vector is much less effective than using the engine positioned on the outside of the turn. Therefore, control of the aircraft is poorer, and air movement is faster.
Some airports may impose speed restrictions on the runway due to uneven surfaces, construction on adjacent runways, sharp turns, or other operational issues.
