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Increased Safety and robust certification for ditching of aircrafts and helicopters

Periodic Reporting for period 2 - SARAH (Increased Safety and robust certification for ditching of aircrafts and helicopters)

Période du rapport: 2018-04-01 au 2020-03-31

Airborne vehicles (i.e. aircrafts and helicopters) need to travel above water to fulfill their mission and thus have to prove a safe water landing under emergency conditions. The challenge for their design is to minimize the risk of injury to persons on board and to enable safe evacuation of the occupants. Accordingly, the motion during the water impact along with the forces acting on the structure are needed to be understood in the design phase of an aircraft. Also the subsequent floatation and the evacuation process have to be considered.
SARAHs (overview see figure) global objective is to provide solution that improve safety of airborne vehicles by
• improving aircraft/ helicopter certification tools in order to deliver accurate loads to safely design aircrafts/ helicopters and deliver input on how ditching needs to be simulated in order to obtain robust, safe and accurate loading information
• deriving a robust way to safely design new configurations (for which no engineering experience is available) w.r.t. ditching
• using methods obtained to analyses and optimize approach, landing and impact phases to supporting the pilot in water-landing scenarios by performing simulations using the codes developed within SARAH.
• delivering test results to validate simulation
The work performed is broken down to the following work-packages.
WP1 is the project management inside SARAH. Standard project management tasks have been performed which are detailed in the interim technical report (D1.1).
WP2 focusses on the method development, concentrating on novel analysis methods and process for improving safety of airborne vehicles.
Progress in WP2 has been achieved and documented in details in D2.1 and D1.1. In particular it includes the following major highlights:
• delivery of “open” (not IP-restricted) geometries used for benchmarking
• support for design of test-specimen (WP5) w.r.t. loads calculation
• setup of tool chain for coupled high-fidelity helicopter and aircraft simulations
• improvement of low-fidelity simulation tools
• implementation of means to simulate waves
In the second project half progress with regard to finalization of the fully coupled high-fidelity simulations will be achieved as well as the finalization of WP2 with regard to improving low-fidelity tools.
WP3 includes the analysis of physical effects during ditching for academic conditions (still water and simple kinematics).
In Wp3.1 a model with rigid and fixed floats has been built and a ditching case in calm water has been simulated. Loads for dedicated components have been delivered to support the WP5 mockup. Simulations in waves have been performed with the Rienecker & Fenton nonlinear regular wave model as well.
WP 3.2 tackles the ground aerodynamics, in particular the ground effect, with regard to its impact on water emergency landings. The work performed by TUHH concentrates on adaptations of the code ditch, which are based on high-fidelity CFD-calculations to understand the impact of the ground effect on the overall lift.
WP4 addresses design solutions to increase safety of conventional and unconventional aircrafts and helicopters.
In WP4.1 concepts for energy absorption solution have been prepared and delivered for A/C and H/C.
The activities in WP4.2 were started earlier than anticipated in order to cope with deviations occurring in other Work-Packages. At the current stage first ditching simulations on a Blended Wing Body configuration have been performed and currently tool updates to improve the simulation are implemented.
WP5: Activities are devoted to updates on both test-facilities used in SARAH.
In WP5.1 (Helicopter tests) the following progress has been achieved:
• Definition and helicopter geometry and realistic loading conditions
• Definition of the instrumentation matrix, chain of measurements and test-matrix
• Finalized project for the guiding system, imminent order
• Last phase of design for helicopter
• Last phase of design for the EFS (imminent order)
• Full planning for the experimental campaign
In WP5.2 (Aircraft tests) the following progress has been achieved:
In the first half of the SARAH project CNR-INSEAN has put most of the effort in the preparation of the experimental setup for the conduction of experiments on Task 5.2. More specifically, the activity concerned:
- Improvement of the facility for safer, faster and more reliable test execution
- Design of the specimen for T5.2.1 and T5.2.4
- Design of the experimental setup for T5.2.4
- Design of the structural component for T5.2.2
- Preliminary definition of the specimen for T5.2.3
- Built of the specimen to be used for T5.2.1
- Preparation of the experimental setup for T5.2.1
WP6 is aims at exploring the full benefits derived in the technical WPs2-5. Major activities occur in the second project half, so far model building activities in WP6 are active to deliver a nonlinear, realistic aircraft model to be used to be used for high-fidelity simulations in other WPs.
WP7 is dedicated to the monitoring, management and reporting of these activities.
A Plan for the Dissemination of project Results (PDR) was delivered and updated. The project visual identify as well as diss. material was distributed.
State of the Art
In general, ditching can be investigated by accident analysis, by experiments and numerical simulations. Model-scale ditching tests are the traditional way of ditching performance analysis of aircraft designs. The level of complexity of numerical ditching simulations ranges from (semi-) analytical water-impact formulas to numerical simulation methods taking into account the complete aircraft and the near field of the surrounding fluids. While the ditching accident analysis is confined to a few well-documented specific incidences, ditching tests and numerical simulations of ditching allow investigating the ditching performance during the design phase considering various parameter influences. The present approach for certification predominantly uses experiments or refers to certified former designs that were experimentally investigated. Such experiments are usually performed at model scale for rigid bodies and the respective loads are transferred to a subsequent structural analysis in a one-way-coupling approach.
Expected impacts
- positive impacts on the safety of the passengers and crews thanks to the optimization of the performances of the simulation linked to ditching.
- better way to understand locally the effects occurring during water impact phase.
- synergy created by the cooperation between skilled entities (tests facilities, numerical developers and manufacturers).
expected results:
SARAH focuses on improving the understanding of the underlying phenomena with regard to ditching. In order to achieve this SARAH improve aircraft/ helicopter certification tools in order to deliver accurate loads to safely design aircrafts/ helicopters and deliver input on how ditching needs to be simulated in order to obtain robust, safe and accurate loading information. Within this field of work SARAH will concentrate on delivering accurate simulation means validated by test-data to simulate the complex pyhsical phenomena taking into account environmental effects