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nsitu is a Boeing subsidiary that
specialises in UAVs; its three current
platforms are the ScanEagle, the
Integrator and the RQ-21 Blackjack.
The latter was developed for the US
Navy as a spin-off from the Integrator
project. The ScanEagle has been
deployed by the US military since 2004.
The ScanEagle has a 10 ft wingspan
and is currently powered by a naturally
aspirated, small-displacement, spark-
ignited two-stroke engine built to Insitu’s
prints by a third-party manufacturer.
Insitu manufactures the ScanEagle
and operates it on behalf of certain
customers. Recently it decided to put all
its UAV expertise and experience into
developing an Insitu dedicated-UAS
engine in the quest for superior reliability
and performance.
This bespoke engine, internally
designated the N20, was devised
by a special Propulsion Engineering
group within Insitu. Headed by Kevin
Beloy, the group started by defining the
requirements for a clean-sheet-of-paper
propulsion system – “and there were
hundreds of high-level requirements”,
Beloy notes. A procurement competition
was then held to select the source of
design and manufacture.
Of the proposals received, “Orbital had
the strongest technology, with the best
design and manufacturing expertise,”
remarks Beloy. Of particular interest was
its unique direct injection (DI) technology.
“We could find no better provider of
fuelling technology for a small two-stroke
running on heavy fuel,” he adds.
“The Orbital compressed-air assisted
direct injection technology that our new
N20 incorporates is compatible with
multiple fuel types, provides resilience
to variations in fuel properties, is reliable
and no glow plug is required,” he says.
“Normally a spark-ignited engine
runs hot to burn jet fuel properly, but
the Orbital technology allows the N20
to run much cooler, increasing the time
between overhauls by at least three times
compared with other heavy fuel engines.
It also requires only minimum scheduled
maintenance such as air filter and spark
plug changes, and no de-carboning or
reconditioning procedures are required.”
Beloy explains that the target was to
increase reliability tenfold by controlling
engine design and manufacture. “We
When Insitu wanted a bespoke engine for its small
unmanned aerial systems family it chose Orbital to
provide the solution.
Ian Bamsey
reports
Double
act
The Insitu/Orbital N20 two-stroke
features advanced direct injection
June/July 2016 |
Unmanned Systems Technology