This paper deals with a signal-based method for robust and early detection of lock-in-place failures (a.k.a. jamming) in aircraft control surface servo-loops. Earlier and robust detection of such failures is an important issue since they may cause additional structural load and affect the sustainability of civil transport airplane. The proposed signal-based scheme uses a sliding-mode differentiator to provide derivatives of measurable signals in noisy environment. Jamming events are next detected by using a dedicated decision making-rule that is able to detect actuator outage (the stuck value can be near zero). The proposed monitoring scheme has been tested on Airbus test facilities located at Toulouse, France. The results confirm good level of robustness and performance, even in extreme situations. The proposed technique can be applied, with slight modifications, to any type of actuator, e.g. Hydraulic, Electro-Hydrostatic (EHA) or Electro-Backup-Hydrostatic (EBHA) actuators.