The effect of runway roughness on aircraft operations

Most airport owners & operators think about runway roughness only when complaints from pilots and passengers start occurring. However, there is a recent interest in adding runway ride quality as a part of Pavement Maintenance/Management Systems (PMMS). It is important to monitor airport pavements for smoothness for several reasons. It is known that smooth pavements last longer. Studies show that the dynamic loading of pavements can significantly reduce their life (Gerardi & Johnson, 1994). What is not so well known, is the effect of runway roughness on aircraft operations. Not only can runway roughness increase aircraft stopping distance, it can also be a safety issue, particularly in an aborted takeoff. It also adds fatigue damage to the aircraft by amplifying the Ground-Air-Ground (GAG) fatigue cycle effects. The added fatigue damage is subtle in nature, but its effects are felt as the "aging fleet" approaches their fatigue design lives. This fatigue damage occurs in primary aircraft structure as well as subsystems. This paper presents several case histories of aircraft operations on rough runways that contributed to aircraft incidents. It will describe one case in point where an aborted takeoff on a particular US airport runway could have likely ended in a blown nose landing gear tire or broken nose landing gear strut. This paper also describes a scenario that may have contributed to the TWA Flight 800 disaster. This paper concludes by describing a statement of need to establish a limit on allowable runway and taxiway roughness. This smoothness standard should be based on aircraft ride quality. Pavements would be periodically checked and maintained to that established standard. By maintaining pavements to a "not to exceed" level of roughness, pavement life will be extended. It will also enable aircraft designers to more accurately define the loads experienced over the life of the aircraft, therefore improving the design. In summary, tracking and maintaining smooth pavements is cost effective and is a technology ready for engineering and management use.