Wind Shear of Low-Level Jets and Their Influence on Manned and Unmanned Fixed-Wing Aircraft during Landing Approach

Abstract

Wind shear at low altitudes represents a potential hazard to landing aircraft. Based on two wind lidar data sets of one year, the occurrence of low-level jets (LLJs), the vertical wind shear and the rotation of the wind direction were analysed. The lidar system was located at the sites of Braunschweig in the North German Plain, Germany, and Clausthal-Zellerfeld in the low mountain range Harz, Germany. The observed wind shear gradients between the altitude of 40 m and the altitude of the maximum wind speed was in the range of −0.23 s−1 to +0.20 s−1. The rotation of the wind direction with altitude occurred both in clockwise and anticlockwise direction. The ratio of clockwise versus anticlockwise occurrence of directional shear was 4:1 for Braunschweig and 3:1 for Clausthal-Zellerfeld. The observed wind shear gradients were compared to values for hazard potential of different levels for a typical aircraft. Although the LLJ was not hazardous for manned aircraft in any observed case, the awareness of LLJ helps to reduce the pilot’s workload and possible pilot-introduced oscillations caused as a result of the wind shear and aircraft characteristics. In contrast to manned aviation, the value of changes in wind speed and direction during LLJ conditions can cause significant risks for unmanned aerial system operations with less than 25 kg of take-off weight. This is a result of the lower airspeed-wind-speed ratio and the flight control and flight planning.

Wind Shear Operation-Based Competency Assessment Model for Civil Aviation Pilots

“…However, regardless of the wind shear threat and the wind shear alarm, pilots must initiate timely and effective operations [19]. Pilots can use different methods to identify RWS wind shear events, such as predicting them in advance; observing the wind direction, speed and other characteristics during the phases when the FAC is unable to provide wind shear detection; and paying attention to changes in the avionic system's flight parameters when the FAC provides wind shear detection information.…”

Missed Approach, a Safety-Critical Go-Around Procedure in Aviation: Prediction Based on Machine Learning-Ensemble Imbalance Learning

“…Te ensemble's threshold is ∆ j , i.e., H j (x) � sgn(􏽐 that model H j has to achieve. Te ∇ pr is the basically misclassifcation rate of a majority class instances to the minority class (4) repeat (5) j ⇐ j + 1 (6) Sample a subset B j randomly from B such that |B j | � |A| (7) Learn the model H j by using minority class set A and subset B j . H j is the base estimator with weak classifers h j,l and corresponding weights distribution ω j,l .…”

“…Low-level wind shear during the fnal approach phase can have two potentially catastrophic efects on the aircraft, and pilots feel enormous pressure: (1) low-level wind shear can destabilize the glide path, and (2) it can induce the approach speed to veer away from the predefned threshold [7]. Te efects of decreasing and increasing shear from the headwind on an aircraft are depicted in Figure 2 under the assumption of no pilot intervention and a standard instrument landing system (ILS) approach with a glide slope of 3 degrees.…”