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Operational disruption management
Published in Peter J. Bruce, Yi Gao, John M. C. King, Airline Operations, 2018
Winter is unique not only due to the possibility of heavy snow or freezing precipitation, but because of potentially extensive de-icing delays. Meteorologists have become very accurate in their ability to predict with a high level of confidence not only when snow will begin, but what type of accumulations can be expected, as well as whether the snow is likely to be wet or dry. Airlines can use that information to reduce or suspend operations, depending on the severity of a storm. Safety is always an airline’s highest priority, but ensuring an acceptable level of passenger experience is also important. There are many reasons for which an airline would reduce its schedule at one of its larger airports, but here is one example. An airline has four de-icing pads. With two crews working on each pad in moderate snow, de-icing might average fifteen minutes per aircraft, one aircraft per pad. That means the best throughput they can expect is four aircraft per pad per hour, or sixteen departures per hour, as a best case. Even if the rate were reduced to sixteen per hour, it is important those sixteen are staggered as much as possible to minimize delays. If all sixteen arrive in a bank and then push back at roughly the same time, the delays will be much longer than desired. If they are scheduled at a rate of twenty arrivals per hour, it will not take long for the delays to become unacceptable not only to the airline, but to its passengers.
Airport capacity management
Published in Gert Meijer, Fundamentals of Aviation Operations, 2020
A special type of weather-dependent operation is in de-icing aircraft prior to take-off. This is necessary for aircraft operations in freezing conditions, whereby snow, water or moist quickly become ice on the aircraft’s wing surface, if not at the airport than at low altitudes shortly after take-off. Departing with ice on the wing’s surface is dangerous and often results in a fatal incident; de-icing therefore is directly related to flight safety.
NaCl and Na2SO4 solution effect on weathering steel visual appearance when the ambient temperature changes cyclically
Published in Cogent Engineering, 2019
Mindaugas Daukšys, Evelina Bitautaitė, Jūratė Mockienė, Dalia Nizevičienė
According to the climate conditions, Lithuania falls into climate zones 5 and 6 where ice storms, blizzards, drifting snow, snowing and sleet occur. The average annual total frequencies of freeze-thaw events with the daily maximum +20°C and minimum –20°C temperatures ranges from 9 to 17 cycles. Roads, highways and sidewalks can be covered by snow or ice during the wintertime. De-icing of roads has traditionally been performed using salt, often mixed with sand and gravel, spread by snowplough or dump trucks designed to spread it, on slippery roads. De-icing can be accomplished by use of dry or liquid chemicals designed to lower the freezing point of water (e.g. various salts). The most common de-icing chemical is sodium chloride (NaCl). It has a strong tendency to cause corrosion, rusting the steel used in most constructions. The most popular chemicals used for de-icing purposes in Lithuania are 3% NaCl solution and other mixes of salts. Sodium sulphate (Na2SO4) is relatively common in alkali lakes, ground water and sea water. The facades finished with Cor-Ten steel cladding may be located close to the road treated with de-icing 3% NaCl solutions salts or close to sea, the water of which has some amount of Na2SO4 salts. In the cold season, the facade may be exposed to cyclical temperature fluctuations in water or different salt environment. In this way to imitate winter conditions, which appear in Lithuania, 3% NaCl and 3% Na2SO4 solutions were chosen. The solutions concerning other salts and different ambient temperature were not taken into account in this manuscript. In this case, these factors can have a different effect on the forming of patina layer (e.g. visual appearance and colour) on the surface of Cor-Ten steel plates.
Jiangyin Bridge: An Example of Integrating Structural Health Monitoring with Bridge Maintenance
Published in Structural Engineering International, 2018
The deck surface temperature is a parameter that is important to the bridge operator. In summer, the deck temperature can reach close to 60°C, which is approximately 20°C higher than the air temperature. The high temperature causes damage to the pavement, leading to pavement rutting and permanent deformation; therefore, water-spraying is performed during periods of high temperature. In winter, wet and snowy weather can cause a traffic hazard when ice is formed, so when this occurs de-icing countermeasures are implemented to avoid traffic accidents.
Evaluation of skid resistance of pervious concrete slabs under various winter conditions for driver and pedestrian users
Published in Road Materials and Pavement Design, 2021
Harry Rodin III, Somayeh Nassiri, Othman AlShareedah, Mina Yekkalar, Liv Haselbach
The BPN values measured after applying anti and de-icing treatments were compared to the baseline iced condition as presented in Figure 7 for both PC and PCC. Anti-icing was used to prevent ice from forming on the surface, while de-icing methods are used to melt the ice after development.