Element Materials Technology’s experienced team has performed major test programs to support the certification for ditching compliance on the following aircraft:
- EADS-CASA CN235-300M
- Mitsubishi Regional Jet (MRJ)
The projects utilized a large scale aircraft model to support ditching clearance against the regulations put down by the Federal Aviation Authorities FAR 25.
The use of large scale models reduces the risk of scaling errors when reading across to the full scale aircraft and the test technique is recognized by the certification authorities. The incorporation of scale strength attachments additionally further add validation to the method allowing external parts to breakaway as in a real event.
This ‘Free Flight’ test methodology has been used to support CFD analysis by both aircraft manufacturers detailed above.
Three main phases in a planned ditching event are detailed below:
- The preparation of the crew
- The impact with the water
- The subsequent floatation phase.
Element’s Hydrodynamics subject matter expert has supported all these phases across a large number of programs since the late 1960’s.
Definition of Airworthiness Requirements
The hydrodynamic ditching test should be part of the airworthiness compliance verification program which will be used to demonstrate the ditching compliance to the related airworthiness regulations FAR25.
Objectives of the Ditching Process
The objective of the ditching test with a scale model is to characterize the aeroplane behavior in water landing and to obtain the data to prove the safety of passengers and crews, and the availability of exits during water landing. The scale model shall simulate the configuration of the actual aeroplane and the scale strength attachments. The required measurement values shall be measured under defined test conditions.
The test results will be reflected into the Aeroplane Flight Manual as the recommended safety ditching procedure.
The purpose of the scale model test for ditching has typically been performed as evidence to satisfy the Federal Aviation Authorities:FAR Part 25 Airworthiness Standards: Transport Category Planes
Subpart D - - Design and Construction: Emergency Provisions
Section 25.801 Ditching
Aircraft must meet
- 25.801 (Ditching)
- 25.807(e) (Emergency Exits)
- 25.1411 (Safety Equipment)
- 25.1415 (Ditching Equipment)
Additionally data can be gained to help satisfy the following FAA Code of Federal Regulation:
FAR Part 25 Subpart C, Section 25.561, para (b)(3):
The occupant experiences the following ultimate inertia forces acting separately relative to the surrounding structure:
- Upward, 3.0g
- Forward, 9.0g
- Sideways 3.0g on the airframe
- Downwards, 6.0g
- Rearward, 1.5g