RISK MANaGEMENT
Aviation consultancy Roland
Berger counted 170
electrically-propelled aircraft
in development around the
world for a study published last July. By the time you read
this, the consultancy estimates that the tally will have
risen to almost 200.
By far the largest number of these aircraft are electric
vertical takeoff and landing (eVTOL) aircraft – clean
sheet designs using electric powertrains and propulsion
systems in entirely new ways. The development
programs are taking place mostly in the USA and Europe,
where many startups are beginning to face the reality of
turning CAD drawings into metal and composite that
moves in the sky.
VERTICAL APPROACH
Bristol, UK-based Vertical Aerospace hopes to be one of
the first companies to market with an eVTOL aircraft.
The company plans to complete the testing and
certification of its first aircraft by 2023
and to start services on short, piloted
intercity routes soon after. While it is in
service, Vertical plans to extend the
aircraft’s range and eventually introduce
autonomy to it, while expanding the
number of routes that it can serve.
66 DECEMBER \\ AEROSPACETESTINGINTERNATIONAL.COM
1000kg
Weight of Vertical
Aerospace’s Seraph
eVTOL demonstrator
“you tiptoe out to the
edges of performance.
You progressively get
more challenging to
expand the flight
envelope in a safe way”
failure. The company had to consider
what happens if one or more of
Seraph’s rotors fails. To deal with this
and similar risks, Harper and the rest
of the team at Vertical worked out in
advance of the flight testing program which parts of the
aircraft had a high-risk of failure. The team then worked
to mitigate the risks. Harper describes the process as a
“common-sense approach”.
“Like most aerospace testing, it’s about always doing
things in the least dangerous way. As a company a risk to
life or a risk to people’s property is never acceptable,
so we identify and take measures to mitigate them,”
says Harper.
“We record all of the risks, including the functional
risks. In some cases we are able to design out the risk
from the testing.”
For example, Seraph has an independent, backup
control system in case there is a loss of control as well as
a “kill switch”.
REGULATORY OVERSIGHT
Outside of hardware-design changes, measures are taken
in accordance with aviation authority rules to ensure
testing is conducted in a safe manner. In the UK,
companies developing experimental aircraft have to meet
certain requirements to qualify as a design organization.
They also have a choice of meeting either
the Civil Aviation Authority’s rules on
testing experimental aircraft, CAP 1220,
or the European Union Aviation Safety
Agency’s Part 201J. “They are very similar
to each other and both are similar to the
FAA’s equivalent rules thanks to
agreements on processes and design
approvals,” says Harper.
“The CAA were very involved up front
with us. They wanted to ensure that we
had the right processes and that we had
considered the risks. Once they were
satisfied we were going to behave they
became less involved,” he says.
Processes and resources that are
required to ensure safety during testing
include the production of a
comprehensive operations manual and
test plan. Everyone involved has to be
adequately qualified. Scenario planning
must be undertaken, and the regulator
has to be satisfied that all safety aspects
have been considered alongside the
high-level risks. Once the testing site has
been located, a survey has to be conducted
which assesses the external risks and that
250kg
Maximum load
the Seraph
eVTOL can carry
The company, which was founded in
2016, flew its first proof of concept
demonstrator at Cotswold Airport in the
UK in June 2018. Engineers at Vertical
have recently concluded flight testing of
its second full-size prototype, called
Seraph, which weighs 1000kg, can reach speeds of up to
80km/h and carry loads of up to 250kg.
Seraph, which is now undergoing several months of
ground testing, takes design cues from multi-rotor
drones and like many eVTOL aircraft can be described as
an enlarged drone. Seraph completed its first flight test
campaign without any major incidents, thanks in no
small part to Paul Harper, chief certification engineer at
Vertical Aerospace. Harper is responsible for ensuring
the safety of flight testing Seraph and liaising with the
UK’s Civil Aviation Authority (CAA). He says, “We started
as a small group of people tasked with taking drone
technology and scaling it up into a useful aircraft.
“In the early days we were able to use advanced
hobbyist drone kits for testing. We could build cheaply
and quickly and learn from the tests. As we’ve scaled up
into a heavier full-size aircraft with complex flight
systems we have needed to build in redundancy and
functional safety. We had to start looking at possible
failure modes in dynamic situations.”
One of the possible failure scenarios with Seraph, in
common with all other drones and helicopters, is rotor
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