Flight International - 04

Environment Action
The UK Royal Air Force has experimented
with Velis Electro as part of training study
“There are a lot of people in the industry who really
hope for progress and to see the services become a
large buyer of SAF,” says Csonka. “And while it is a
question of when, not if, the question can be asked:
will the military be the last purchaser of SAF? Or
will the recent NDAA mandate to evaluate various
options for SAF supply initiate an earlier uptake?”
While FlightGlobal’s research has not found
any military forces regularly using SAF, there are
many military models on the path of testing and
certification, including with the Japan Air Self-
Defence Force and the Republic of Singapore Air
Force, and there are infrastructure developments.
From January, the NATO Central Europe Pipeline
that supplies Brussels airport with kerosene was
opened for the transport of SAF.
In parallel there is a frenzy of R&D work around
disruptive propulsion technologies with direct
applicability between the work being done in the civil
Fierce project saw unmanned jet flown
on 100% Airmade SAF in mid-2022
world to military platforms, says Winter. All of P&W’s
military engines are approved for SAF use based on
today’s fuel specifications and the F135 engine for the
F-35 has run on 100% SAF.
“When you look at a military, and when you look at
a commercial engine, they both have fans, compressors
and combustors,” says Winter. “There are some
nuanced differences, but the way you optimise one
and the way you optimise the other are similar; you are
relying on the same physics and the same chemistry.”
P&W is among all the majors and a plethora
of smaller players working on electrification,
hybrid-electric and hydrogen powerplant technologies.
For instance, Pratt & Whitney Canada is leading
development of a hybrid powerplant, which incorporates
a 1MW electric motor to equip a De Havilland
Canada Dash 8-100 with the system. It is planned to
fly in 2024 and is targeting a 30% reduction in fuel
burn and carbon dioxide emissions compared to
today’s turboprops.
“Those same technologies have direct applicability
[to military platforms],” explains Winter. “In terms of
larger engines, we’re also looking at that sweet spot of
around one megawatt. The military would love another
megawatt of power on board – that’s an order of magnitude
more than they have on board fighters today.”
The extra electrical power could be used for an
electronic warfare suite, for directed-energy weapons
or for silent operations, he notes.
Airframe efficiencies
While much of the focus is on disruptive propulsion
solutions to decarbonise military aircraft, the OEMs
are seeking efficiencies from airframes as well.
“This journey doesn’t stop here,” says Guzman.
“We keep improving our aircraft with initiatives like
Herwingt (Hybrid-Electric Regional Wing Integration
Novel Green Technologies), which is a [EU] Clean
Aviation project focused on the design of a more
performant wing for military aircraft.”
The idea of not flying altogether is another prospect
by using synthetic training as an alternative to avoid
flight testing and training emissions, says Guzman.
“By nature, our products and services contribute
to reducing the carbon footprint of our customers,”
says Helene Gagnon, chief sustainability officer at
global training giant CAE. “It is estimated that one
minute of live training in a Eurofighter generates
as much carbon emissions as a full day in the same
platform simulator.
“Although simulation will not take the place of
live flight training, it allows students to practice and
master abilities, making live flight training more
effective and efficient, supporting our environment
and our customers,” she says.
Elsewhere in the military training world, the RAF and
the Royal Danish Air Force have been trialling the use
of Pipistrel’s all-electric Velis Electro two-seat trainer
with a view to replacing traditionally-powered types.
There are many opportunities for the defence
sector to decarbonise, but clearly many complexities
and challenges too.
The question of sustainability has arrived front and
centre on the agenda for military leaders. Progress
is too slow for some, however just as in the commercial
aviation arena the bandwagon is rolling and
cannot be stopped. ◗
April 2023 Flight International 59