Metrology
including activities on ditching and numerical
simulation,” Adden says.
VIRTUAL COMPLEXITY
SARAH used two test centres, one in Italy and one in
France. Testing in Italy included several campaigns from
June 2018 to June 2019. SARAH’s researchers are focusing
on developing ways to improve the physical and virtual
methods of testing an aircraft’s behavior when it is
ditching. Each phase of the research and testing
examines a different aspect of ditching, including one
looking at high speeds, one examining deformation of
the aircraft and another analyzing variable pitch, the
angle at which the aircraft hits the water.
“One simulation does not tell us anything of value,”
says Adden. “We need different conditions. We normally
have some sort of off-test matrix or simulation matrix we
have to go through.”
A holistic approach to simulation is needed to help
improve the modelling. “We need to be able to do it
without the simulation taking half a year,” he says. “The
technical problem is so complex, because it’s
multidisciplinary, that if we look at high-fidelity
simulations, we still need to have four to six weeks of
testing to validate one simulation.”
Test equipment was upgraded for SARAH to measure
more data when the model specimen hits the water. “It’s
the first time that we have tested double curvature
specimens,” says Adden. A double curvature specimen is
a model that is identical with the fuselage when it hits
34 DECEMBER 2019 \\ AEROSPACETESTINGINTERNATIONAL.COM
“The technical problem
is so complex because
it is multidisciplinary”
the water. All models are scale-models of aircraft,
although the models are all of a similar size so they are
appropriate for the water tank being used. The scale
model’s results can be extrapolated mathematically for
the full-size aircraft.
PHYSICAL MODELS
Airbus is a participant in the SARAH project and the
work in France saw helicopter models tested with and
without mock emergency flotation systems. Airbus
Helicopters stress engineer, Severin Halbout, explains
what was measured in ditch tests: “We are focused on
the impact phase and the loads that might happen
during the impact. We chose at the beginning to have as
a helicopter reference the Super Puma.”
However, the test model became a generic design
because it is an EU research program and the results of
which are made public. “The design is a generic shape
and it is the heart of our work for the rotorcraft. The
mock-up has a scale of one-third,” Halbout adds.
Ditch testing for certification of commercial
passenger aircraft takes a different approach to the
models. For certification they are built by craftsmen to
be almost identical to the final design of the aircraft.
Aerospace testing services provider Element conducts
ditch testing of aircraft models in a water tank in the UK
with civil engineering firm, H.R. Wallingford.
“We do the physical part, not the virtual testing. Just
last year we completed ditch testing of the C919 for
Comac in China,” says Element Materials Technology US
aerospace product qualifications testing operations
director, Stuart Brown.
Inside those physical models, sensors collect data to
ensure the testing is reliable. “We’ve got a microsystem
inside the model similar to that which is used in crash
test dummies,” says Brown.
“It’s a small data acquisition system that sits
inside the plane and captures all the data.”
After the model has ditched, it is
1 // US Airways
Flight 1549 is lifted
out of the Hudson
after its now famous
ditching in 2009
2 // The partial
structures of aircraft
can be investigated as
part of ditch testing
1
2
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