EXECUTIVE SUMMARY:
The present Report on Weather Hazards, Weather Impact Areas and Evaluation Methods is the first deliverable of WP 2.1. It contains an update of existing knowledge on both identification of adverse weather, assessment of weather impact areas in aviation operations and methods to assess the weather impact on aviation operation efficiency.

Chapter 3 describes in detail the various atmospheric hazards, which pose risks to aircraft. They include the phenomena related to thunderstorms (Cb) like lightning, microbursts/downbursts, convective turbulence, icing and also visibility. CAT, which is turbulence found in the cloud-free atmosphere, often in the vicinity of jet streams, can also be induced by thunderstorms. Depending on the severity, these hazards can lead to fatal accidents and have done so in the past. Loss of orientation caused by low visibility especially, the prime cause for CFIT, is a serious threat.

Another hazard, caused by aircraft themselves, is wake vortices, which form at the wings of an aircraft and persist for several minutes. They can be so strong that smaller aircraft following a larger one can get into serious difficulties, sometimes resulting in loss of control. This is especially true during take-off, when the aircraft speed is low.

Volcanic ash is another phenomenon that can become hazardous for aircraft. The intake of air containing ash particles can lead to flame-out and prevent the engines from being restarted. In the past several near accidents occurred where the crew was able to recover the aircraft just in time to prevent ground collision.
In Chapter 4, methods to determine the weather impact on aviation are described. These include the use of accident and incident statistics as well as efficiency itself and numerous climatologies that provide information on the occurrence and regional distribution of the various hazards. The data sets available to FLYSAFE are also presented in this chapter.

With regard to efficiency, several methods to quantify the weather impact on aviation operation efficiency, namely delays and respectively punctuality, are presented. Next, monitoring tools for delay are shown and discussed. As an example, the monitoring tool “Netline”, used by Tyrolean Airways, is described in more detail. The chapter closes with a listing of available delay statistics and datasets that can potentially be used for further investigations.
Chapter 5 is dedicated to weather impact studies. The impact of weather on safety, efficiency and capacity is identified and partly quantified. With respect to atmospheric hazards, a number of weather impact studies are analysed and described and recommendations are given explaining how to reduce these impacts. With regards to efficiency, first, a general introduction about the effect of weather on aviation operation efficiency is given. This introduction is followed by an analysis of the impact of weather on delays, air traffic operations and ATC and an analysis of the decision-making due to the impact of weather. For a deeper insight, a questionnaire on the impact of weather on business jet operations was set up and evaluated.

The next section of Chapter 5 is an overview of available weather impact studies with regards to efficiency and includes studies on the cost of delays. Many of the studies are from the U.S. but they also give valuable information for the European air traffic system. All impact studies clearly show that there is a need for improved weather forecasts and new products as there is a great weather impact on aviation. For example, Lindsey (1998) found that 40-65% of delays that U.S. domestic airlines experience are attributable to adverse weather.

The chapter finishes with an investigation of the cost benefit of new or potentially new products. A more detailed description is given of the Integrated Terminal Weather System (ITWS) and the Corridor Integrated Weather System (CIWS) as they represent major new products within the U.S. aviation system. Their benefits have already been investigated with respect to costs and safety for several locations and are described. ITWS and CIWS proved high yearly economic benefits. Furthermore, they have become valuable decision aids and have helped significantly to optimise ATC and airport authorities operations and thus also to reduce delays.

For further information please contact:
Mr. Michael Theusner: flysafe@muk.uni-hannover.de