In 1994, an ATR-72 crashed at Roselawn, Indiana, USA. It has been speculated that accident was due to Supercooled Large Droplet (SLD) icing. This accident led to a modification of the regulation rules with the definition of the Appendix O which includes freezing drizzle and freezing rain icing conditions. The associated NPRM (Notice of Proposed Rule Making) has been distributed to industry for comments on 29th June 2010 and could be applicable by beginning 2012. In order to comply with this new rule, the simulation tools, as Acceptable Means of Compliance, have to be improved and validated for these conditions.
The paper presents the work performed within Airbus to review, improve and assess simulation tools capability to accurately predict physical phenomena related to SLD. It focuses in particular on splashing and bouncing phenomena which have been highlighted as the first order effects. In a first step, the NASA splashing and bouncing model has been introduced within the ONICE2D ice accretion suite, developed by ONERA, and its implementation has been validated versus the overall NASA SLD experimental database. In a second step, the SLD capability of the DROP3D code, developed by NTI, has been as well assessed by comparing the results obtained on a selected number of test cases from the NASA SLD database to available experimental measurements. For both ONICE2D and DROP3D codes the activation of the SLD model has led to significantly improve collection efficiency predictions. A preliminary SLD capability is now available at Airbus for further assessment on representative industrial configurations.