Airport Winter Operations. Motivation, Activities and Coordination

Table of contents

I. List of Abbreviations

II. Introduction
i. Motivation for Winter Operations
ii. The Scope of Winter Operations
iii. Literature Sources

III. Winter Operations Activities
i. Observable and Background Activities
ii. Snow Removal
i. Importance of Snow Removal
ii. Methods of Snow Removal
iii. Procedure and Vehicles
iv. Snow Removal at Munich Airport
v. Snow Removal Research Overview
vi. Path Scheduling of Snow Ploughs
vii. Path Scheduling Approach Applicability
iii. Aircraft De-Icing
i. Importance of Aircraft De-Icing
ii. Procedures of Aircraft De-Icing
iii. De-Icing Fluids
iv. Techniques of Aircraft De-Icing
v. Aircraft De-Icing at Munich Airport
vi. Aircraft De-Icing Research Overview
vii. Efficient Scheduling Research
viii. Efficient Scheduling Approach Applicability

IV. Coordination of Winter Operations
i. Snow Plan
ii. Information Systems at Munich Airport

V. The Future of Winter Operations
i. Current Information Systems State
ii. Airport Winter Information System Implementation
iii. Understand Airport Interdependencies

VI. BibliographyVI

VII. Picture CreditsX

Abstract

Winter months have a huge impact on operations of an airport. Snow and ice may endanger the safety of starting and landing aircraft. Normal airport activities have to be supplemented by winter operations to ensure safety of the air traffic and to avoid delays in the schedule.

This paper investigates those additional activities which have to be planed during the winter months at an airport. Hereby, snow removal and aircraft de-icing are examined in more detail. After explaining the respective winter operation, real life implementation examples of a German airport are shown. Furthermore, aspects of the respective winter operation suited for optimization are discussed. Afterwards, coordination of winter operations is looked at. Ultimately, an outlook is given on how coordinating airport activities may be supplemented by the use of smarter information systems.

List of Abbreviations

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Outline

I. Introduction
II. Winter Operations Activities
III. Coordination of Winter Operations
IV. The Future of Winter Operations

Winter Operations are important for several Reasons

Motivation for Winter Operations

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This presentation discusses winter operations at airports. Hereby, it is crucial to understand why airports need winter operations and why they should be operated efficiently.

There are many events of delays or even airport closures that are caused by snow and ice. Thus, in the first place, winter operations are needed to maintain flight operations, as snow on a runway impedes a timely start of an aircraft or even disables an aircraft from starting.

Going hand in hand with airport operability, safety issues are a major driver for winter operations. Snow deposits on the runway pose a safety hazard for the airport traffic, just like ice accumulation on an aircraft puts safety at risk. For example, during lift-off ice residues on the aircraft can adversely affect the aircraft’s flight properties. During the flight, it can interfere with the aircraft sensors giving the pilot misleading information.

Delays and airport closures cause immense costs for all agents involved: it affects airport operators, airlines and passengers alike. Thus, winter operations are also needed to avoid such delay and closure costs, besides the flight operations feasibility and safety considerations. Also, the quality of winter operations influences the cost side: poor management will result in higher winter operations costs. Therefore, the agents involved are well advised to maintain efficient operations for snow and ice removal.

Furthermore, winter operations also have a strong impact on the environment. Chemicals used during winter operations can seep into the ground and contaminate the groundwater. Environmental contamination must thus be avoided by using modern equipment and techniques.

Different Perspectives bring different Responsibilities

The Scope of Winter Operations

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Source: [1] Federal Aviation Administration, 2016a [2] Federal Aviation Administration, 2016b 4

The scope of airport winter operations includes two different aspects depending on whether the view is on a broad macro level or on a narrower micro level.

On a macro level, airport winter operations primarily deal with norms and standard operating procedures (SOP) of airport snow / ice removal and aircraft de-icing. Such norms and SOPs are necessary to enforce and guarantee high safety standards. Additionally, regulation helps minimizing the environmental damage. For example, national and international regulation might prescribe the usage of certain chemicals; chemicals known for their high toxicity could be banned. With regard to safety, there are norms on how to duly de-ice an aircraft (Federal Aviation Administration, 2016a). Also, there are SOPs on how to correctly carry out snow removal at an airport (Federal Aviation Administration, 2016b). Finally, the macro view includes the inter-airport coordination and communication. Sometimes, an airport is forced to shut down due to severe weather conditions. Aircraft then needs to head for a different airport in order to land safely. In such cases, good inter-airport coordination is needed.

The micro level includes the management of an individual airport affected by winterly conditions. The micro view primarily deals with the snow and ice removal from the airport area and the de-icing of aircraft. Intra-airport coordination and communication hereby plays an important role. Furthermore, the micro level comprises investment and planning decisions regarding the staffing and training of the workforce as well as on the fleet dedicated to the winter operations.

This paper primarily focuses on the micro view as this view sheds light on the true operations of a winterly airport - the removal of snow and ice from the airport and aircraft. However, the final section of this paper will discuss novel approaches regarding improved intra- and inter- airport cooperation. Hence in this context both, the micro and the macro view, are reviewed.

There are four major Information Sources

Literature Sources

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Information sources used for exploring airport winter operations can be classified according to four categories: aviation specialized books, aviation agencies and public institutions, information released by airports and winter operators as well as papers from specialized journals.

With regard to the first category, books specialized on aviation, Wells (2004) and Kazda & Caves (2007) represent important sources.

The second category of information stems from official sources such as aviation agencies or public institutions. They regulate a proper execution of winter operations which is crucial for flight safety.

As winter operations design and execution to a big extent depends on airport idiosyncrasies like climatic conditions, operations density or airport design, there are distinct publications released by the respective airports and winter operators. These publications serve as the third source of information for this report. We have chosen Munich Airport as the airport of interest due to its geographical proximity. Further reasons for the choice of Munich Airport were the significant size and thus the importance for the German air traffic, being the second largest airport in Germany.

Our last source reviewed are papers from specialized journals, which were primarily utilized for identifying operational problems of winter operations management and for looking for optimization potential of specific winter operations.

Outline

I. Introduction
II. Winter Operations Activities
III. Coordination of Winter Operations
IV. The Future of Winter Operations

Winter Operations are a multi-dimensional Issue

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Winter operations include many different activities. On the one hand, there are observable activities like removing snow from the movement areas and de-icing aircraft. On the other hand, there are also background activities, which can normally not be observed by passengers.

Those background activities include, among other things, recycling of chemicals used during the de-icing process, as well as fleet and staffing decisions. Fleet decisions include winter fleet size, its composition and maintenance as well as investment decisions like leasing versus buying considerations. Staffing decisions include staff training as well as the composition of the winter staff.

We would like to concentrate on some of the displayed aspects to be able to provide a deeper understanding of the subject in a limited amount of time. The cost side is a very important aspect for every business and thus also for winter operations management. Snow removal and aircraft de-icing are very cost-intensive, therefore we will concentrate on these operations. We will not only describe snow removal and aircraft de-icing procedures, but will also analyze the scope for optimization and cost-savings of the respective operations.

In a first step, we will shortly describe snow removal and aircraft de-icing, mentioning the most important factors and how these operations impact flight operations of an airport. After examining specific procedures of the mentioned winter operations, we will take a closer look at how these activities are operated at an airport in real life. We have chosen Munich Airport as a real world example. Ultimately, we will shortly discuss aspects of snow removal and aircraft de-icing suited for optimization.

Outline

I. Introduction
II. Winter Operations Activities
I. Snow Removal
II. Aircraft De-Icing
III. Coordination of Winter Operations
IV. The Future of Winter Operations

We will discuss the following Snow Removal Aspects

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Movement Areas have to be free of Snow and Ice

Importance of Snow Removal

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Source: Kazda & Caves, 2007 10

In the following section, the importance of snow removal at an airport is discussed. Hereby, Kazda & Caves (2007) serves as the primary source of information.

Snow on a runway slows down the aircraft during take-off as it causes resistance on the aircraft’s wheel. Furthermore, snow or ice on the runway decreases the braking effect of the surface during the landing maneuver. These factors impact flight safety and could lead to flight operation disruptions or even cancellation. Therefore, snow removal is the most basic activity of winter operations at an airport to be able to maintain safety during take-off and landing and to avoid flight disruptions.

The magnitude of adverse effects regarding snow on a runway depends on the thickness of the snow layer and the density of snow, which in turn depends on the type of snow. Three types of snow can be distinguished: dry, wet and compacted snow. Slush, a mixture of water and ice crystals, is not part of this classification. The three snow types and slush are sorted in ascending order by its specific weight, slush being the heaviest type.

The higher the specific weight of snow or slush, the higher is the hindering effect of a snow layer on the aircraft’s wheels: Runways have to be closed in case a 5 centimeter (cm) layer of dry snow is covering the surface. For slush, the layer thickness of 13 millimeter (mm) is already sufficient for a runway to be closed, as a much thinner layer of slush is needed to affect the performance of an aircraft in the same way a 5 cm layer of dry snow would do.

There are three Methods of removing Snow and Ice

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Source: Kazda & Caves, 2007 11

The following section describes the methods of snow removal at an airport according to Kazda

& Caves (2007).

There are three methods of cleaning the movement areas of an airport: mechanical snow removal, chemical and thermal ice removal. The mechanical cleaning starts as soon as there is precipitation on the runways. It is carried out by a chain of snow removal vehicles, which will be explained in detail on the next slide. Mechanical snow removal equipment cannot eliminate ice on surface. In case of ice, one of the alternative methods has to be applied.

Chemical ice removal is carried out by vehicles spreading de-icing chemicals on the frozen surfaces. After chemicals have softened the ice, the resulting slush has to be cleaned off the runway mechanically to ensure that the surface does not freeze again. Thermal ice removal is done using underground heating systems, which prevents the runway of getting covered with ice.

The mechanical method should always be preferred over the other two methods as it is the most cost and environment friendly method for cleaning the movement areas. Of the remaining two alternatives, the chemical method is the more popular one due to the lower costs compared to the thermal ice removal and the more sophisticated technology existing.

We will concentrate on the mechanical snow removal as it is the most widely used method due to its economic and environmental advantages.

Mechanical Snow Removal is operated by a Chain of Vehicles

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Source: Wells, 2004 12

The following slide describes how mechanical snow removal is operated in detail and which vehicles are being used for this task. Hereby, Wells (2004) serves as the primary source.

Mechanical snow removal is carried out by a chain of vehicles driving in an echelon formation. Hereby, four or five vehicles drive diagonally, whereby following vehicles are positioned behind and to the left (“left echelon”) or the right side (“right echelon”) of the leader vehicle. The formation size depends on the width of the road to be cleaned. Thus, a wider formation is normally needed for cleaning a runway then for removing snow from the taxiways. The type of the echelon formation depends on the side of the road, to which the snow is meant to be transported (Hess et al., 2009).

Mechanical snow removal is operated by a fleet of vehicles of different types. For removal of slush and very thin layers of snow a snow sweeper is used, which is equipped with a big brush sweeping snow from the surface. For bigger snow formations, a snow plough is used, which is equipped with a big shovel. A snow plough pushes the snow from the surface to the edge of a runway. A snow blower blows the accumulated snow from the side of a runway into the open areas, where, in a next step it is collected and transported off the airport area. Other types of vehicles are used for complementary actions of snow removal, like gritting vehicles spreading anti-icing chemicals on the runway or trucks transporting the snow formations off the airport.

Snow removal vehicles are expensive and the fleet size must be adjusted to the size of the biggest runway to avoid long cleaning times. To reduce the capital tie-up in vehicles of different types, multifunctional vehicles are used. A multifunctional vehicle can simultaneously serve as a snow plough while blowing the accumulated snow from the edge of a runway. Another type of a multifunctional vehicle can combine a snow sweeper with a gritting vehicle, which spreads anti-icing chemicals on the runway after sweeping it.

Munich Airport uses multifunctional Vehicles

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Source: [1] Flughafen München GmbH, 2016a [2] Flughafen München GmbH, 2016b 13

At the following slide, we will take a closer look at snow removal facts and processes of Munich Airport. The information is gathered from the homepage of Munich Airport (Flughafen München GmbH, 2016a).

At Munich Airport, there are two runways to be cleaned as well as several taxiways, aprons and service roads. The surface to be cleaned from snow sums up to four million square meters which is approximately the size of 700 soccer fields.

To be able to tackle the problem of snow removal from such a big area, a diverse fleet of snow cleaning vehicles is available, consisting of powerful multifunctional snow sweeper – blower vehicles, snow ploughs and transporters as well as towing and gritting vehicles.

Per shift, 200 vehicles are used, operated by 200 employees. The workforce is composed of regular staff of Munich Airport as well as of farmers and haulers coming from adjoining regions. The regular staff of Munich Airport is mostly responsible for administrative tasks. Farmers and haulers, which are accustomed to driving large machinery, are responsible for operating the snow removal vehicles.

The combined forces of the modern fleet and the well qualified employees of Munich Airport make it possible to clean one of the two runways in 30 minutes. Hereby only a single run of 12 vehicles working in an echelon formation is needed Airport (Flughafen München GmbH, 2016b). This is an impressive performance, which can be achieved due to the highly modern fleet of Munich Airport. The sweeper – blower vehicle can clean up a 5 m wide strip, which means that an echelon formation consisting of 12 vehicles is needed to clean the 60 m wide runway in Munich. A typical runway sweeper can normally clean up a 3.6 m wide strip (Hess et al., 2009), which would increase the number of needed sweepers to 17 vehicles for the runway of Munich Airport.

Snow Removal Research focuses on efficient Path Scheduling

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This slide focuses on research which aims at optimizing snow removal operations at an airport. Beside the scientific papers focusing on winter operations in general, there are only a few papers solely studying snow removal at airports. The snow removal research hereby focuses on efficient path scheduling of autonomous snow plows (Hess et al., 2007; Saska et al., 2008 a/b; Hess et al., 2009; Saska et al., 2010 a/b). The aim of this research field is always to schedule snow sweeping robots efficiently. Hereby, this research field is working on the same scheduling method, constantly improving the robustness of the method and its suitability for a more realistic environment.

The scheduling method focuses on path planning of robotic multi-vehicle formations. The quality of the cleaning process and thus of the scheduling task is hereby represented by the time needed to complete the shoveling of the airport movement area. The resulting objective of the scheduling task is to minimize the total cleaning time.

The first constraint “each road should always be cleaned” is ensuring the completion of the cleaning task, as each road should be clean after one round of scheduled snow shoveling. The other two constraints of the scheduling task are resulting out of security considerations. The constraint “each road should be cleaned by a sufficient number of ploughs at once” is ensuring that there will be no partly cleaned areas. Uneven surface could be dangerous in emergency situations. In case of an emergency landing, a runway with a constant snow layer is a safer option than a runway with an uneven snow cover. The third constraint “a formation is allowed to turn about only in dead ends“ is connected to the second constraint and is also ensuring the safety. When a snow vehicle is turning on the spot, there is snow remaining on the turning spot from the vehicle itself. These snow residues lead to an uneven surface, which could be a danger in emergency situations. Thus a snow vehicle should not turn while being on the

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