PROMOTION OF TRANSPORT AIRСRAFT FLIGHT SAFETY TAKING INTO ACCOUNT UPDATED CERTIFICATION REQUIREMENTS FOR ICING CONDITIONS

Due to the implementation of new certification requirements for icing conditions provided in Annex О to CS-25, there is a necessity to analyze the impact of the requirements on the possibility of transport aircraft certification for flights under such conditions. The particularities of such certification requirements and their impact on three main directions of aircraft certification have been considered for icing conditions: icing annunciation system, air data system and anti-icing system. It has been shown that new requirements have no effect on certification of air data system sensors but they have an impact on icing annunciation and antiicing system. Timely annunciation of icing is important for safe operation of aircraft. The procedure providing timing annunciation was developed earlier in Annex C to AR/CS/FAR-25. It is highlighted that this procedure is also actual for new icing conditions but taking into account relevant updates in calculations of the growth of ice accretions on ice detectors, air inlets and lifting surfaces. One of the problems is to detect the moment of coming into icing conditions, determined by new requirements. It substantially determines the possibility of immediate escape from icing area if the airplane does not meet the safe operation requirements for such conditions. The techniques of removing ice accretions from lifting surfaces are described. The case of icing the wing surface behind the slats area with barrier ice accumulation was studied. The possibility of an aircraft limitless operation under icing conditions determined by new certification requirements was estimated.

Qualitative Description of a Shoulder Ice Barrier-Ice Interaction During Model Tests

This paper describes, qualitatively and through visual observations, the ice-sheet interaction with a shoulder ice barrier (SIB) during model tests. The model tests were performed in the Hamburg Ship Model Basin (HSVA) during July 2007. Since the SIB represents a new concept in ice barrier structures, model tests were intended to evaluate the general performance of the SIB. The paper describes seven different experiments where the ice thickness, the ice flexural strength, and the shoulder angle of the SIB are the parameters which are varied among them. The results are presented in two sections. The first part refers to observations common to all the experiments, where the ice failure mode and shoulder performance are given special attention. The second part describes the phenomena observed in each particular experiment in more detail. The former analysis allows for the visual identification of three phases (as mentioned in previous publications) and gives a deeper insight into the characteristics of each phase. The latter analysis on the contrary, allows us to achieve interesting conclusions about the SIB performance under different ice conditions and with different shoulder inclinations. A comparison between the failure mode observed during the model tests and observations presented in the literature of full scale vertical and sloped structures, ice interaction with rubble accumulation, is performed. The similarities found in the study between the model and full scale observations lead us to assume that the observed model test behavior may be expected during ice-SIB interaction in full scale conditions. However, some events that could be associated with the problems of the model, such as ice scaling, are highlighted. As a conclusion regarding the SIB performance, it is shown that the shoulder section, which is the principal innovation of the concept, satisfactorily accomplishes its task and represents a key modification to traditional ice barriers in generating smaller ice pieces and avoiding ice overriding.

Shoulder Ice Barrier Ice Tank Testing—Part I: Qualitative Description of a Shoulder Ice Barrier-Ice Interaction During Model Tests

This paper describes qualitatively and through visual observations the ice-sheet interaction with a Shoulder Ice Barrier (SIB) during model tests. The model tests were performed in the Hamburg Ship Model Basin (HSVA) during July 2007. Since the SIB represents a new concept in ice barrier structures, model tests were intended to evaluate the general performance of the SIB. The paper describes seven different experiments where the ice thickness, the ice flexural strength, and the shoulder angle of the SIB are the parameters varied among them. The results are presented in two sections. The first part refers to observations common to all the experiments, where ice failure mode and shoulder performance are given specially attention. The second part describes more into detail the phenomena observed in each particular experiment. The former analysis allows the visual identification of three phases (as mentioned in previous publications), and gives a deeper insight of the characteristics of each phase. The later analysis, on the other hand, allows achieving interesting conclusions about the SIB performance under different ice conditions and with different shoulder inclinations. A comparison between the failure mode observed during the model tests and observations presented in the literature of full scale vertical and sloped structures-ice interaction with rubble accumulation is performed. The similarities found in the study between model and full scale observations lead to suppose that the observed model test behaviour may be expected during ice-SIB interaction in full scale. However, some events that could be associated with problems of the model ice scaling are highlighted. As a conclusion regarding SIB performance, it is shown that the shoulder section, which is the principal innovation of the concept, accomplishes its task satisfactorily and represents a key modification to traditional ice barriers in generating smaller ice pieces and avoiding ice overriding.

Sea Ice: Terminology, Formation and Movement

Anchor ice. All submerged ice attached to the bottom irrespective of the nature of its formation. Barrier ice, or Shelf ice. A form of land ice or land ice afloat, produced by an accumulation of horizontal layers of snow which has reached the intermediate opaque névé or firn stage before passing into true glacier ice. Portions of the barrier break off to form tabular bergs.