A magnificent piece of
The FES is designed and
manufactured specifically for use in sailplanes by
LZ Design. It is aerodynamically clean, effectively
maintenance free, and operationally very uncomplicated compared to a
retractable power plant. While initially designed as a sustainer for
use in conventional gliders, the FES also serves as a Self-Launcher in
lightweight airframes (such as the SILENT 2 Electro).
The FES is comprised of
several key components:
Two purpose built battery
Two purpose built battery
packs - each comprised of 14 Lithium Polymer cells of the very highest
quality deliver a total of 4.2kWh. The packs themselves are built by
LZ Design to very exacting standards and incorporate a sophisticated
Battery Management System (BMS) to ensure optimum performance and
safety during both charge and discharge cycles. The cells are
automatically balanced to within 2 mV and voltage, current and
temperature are continuously monitored.
Each pack weighs 15.5kg
and is very easily removed for re-charging.
A brushless DC motor..
Designed and manufactured
entirely by LZ Design, this DC brushless out-runner motor is designed
and manufactured in meticulous detail and exudes quality in every
All the the components are
produced in-house from highest quality materials and to extremely
exacting mechanical and electrical standards using a combination of
the latest in Electric Wire Discharge Machining and modern CNC
The bearings are sealed
and the motor is essentially maintenance free.
Weighing just under 8 kg,
the motor is capable of delivering 20kW continuous power (23kW peak)
and is up to 95% efficient. The coils are hand wired and rotor
position is precisely controlled via Hall effect sensors. The entire
system, including motor, propeller and spinner is dynamically
Its like no other!
FES Control Unit ..
This standard 57mm
instrument is produced jointly by LZ Design and LX Nav. The FES
Control Unit (FCU) provides the all important interface between man
All key system parameters
are displayed including, Propeller RPM, Battery Capacity, Time
Remaining (at current power setting), Voltage/Current, and
Power is virtually
instantaneous and variable, from zero to maximum (23 kW), simply at
the twist of a knob. Stopping the motor in flight is as simple as
reducing the power to zero, whereupon automatic electric brake parks
the propeller neatly along the fuselage sides. Nothing could be
Produced entirely by LZ
Design, the lightweight Carbon fibre propeller and associated spinner
is designed to offer minimal drag while folded against the fuselage
sides but is deployed is seconds to deliver very respectable climb
rates of up to 3m/sec at full power (4,500 RPM).
Manufactured to the
highest standards in precise moulds, the propeller has a diameter of
1m and each blade weighs just 240 grams.
Performance, Simplicity &
The system provides a
powerful and very highly reliable source of clean aerodynamic thrust
at the twist of a knob. Straight and level flight is typically
achieved at a power setting of about 4kW, which provides endurance of
about 1 hour. However climb rates of 2-3 m/sec are possible, depending
on the weight and type of sailplane in which the FES is installed.
Self launching at full power (20-23 kW) is allowed only in the case of
light sailplanes, in which case ground runs of the order of 80-100m
can be expected.
The benefits compared
to a combustion engine on a retractable pylon are numerous:
- No forward moment on
instantaneous start & stop.
- Operationally very
- Consistent motor
performance regardless of altitude.
- No aerodynamic
change when deployed.
- No smelly or
flammable fluids on-board.
- Relatively quiet and
- Provides more than
adequate battery capacity for even the most complex panel!
As a keen advocate of the
FES from the start, we have followed the development closely and have
considerable personal experience of the system.
Having been factory
trained at LZ Design, we are very pleased to offer advice or
assistance on any aspect of operation and maintenance to FES users in