electric gliders - nadler - nadler & · pdf fileelectric gliders dave nadler “yo...
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Electric Gliders
Dave Nadler “YO Electric”Robert Mudd
Slide 1SSA 2012 Convention
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SSA 2012 Convention Electric Gliders © Dave Nadler "YO“ 2012 Slide 2
Why Power a Glider ?• The Promise of Freedom !
From Tows, Landouts, Crews…• Motor Penalties:
• Weight• Cost and Complexity and Maintenance• Decision Altitudes Higher (stop Soaring to Land):
Plan for motor out and not running situation• Compromises for Different Missions • Touring Motorgliders vs. Performance MGs
(electrics are not for Touring)
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SSA 2012 Convention Electric Gliders © Dave Nadler "YO“ 2012 Slide 3
Why Electric ? Gas Problems...• Reliability (* Jonas De Rese PhD thesis at Delft University)
• Both for the self-launching and sustainer engines, 30 % of the pilots have had an engine failure after having performed a successful test run at the beginning of the flight.
• 30 % of the pilots indicate that some kind of damage was done to the aircraft as a result of having and operating an engine.
• Operational and Maintenance Difficulties:• Air-start time, difficulty, sink rate prior starting• Vibration, noise, heat, fuel, drive belts, etc.
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SSA 2012 Convention Electric Gliders © Dave Nadler "YO“ 2012 Slide 4
Electric Advantages• Reliable – electric motors usually start !
Safety still precludes air-start without field.• Fast air-start (Antares ~ 10 seconds)• Typically automated systems - easy• Low sink rate “engine out not running”
(no cooling radiator) – lower decision height• Low vibration and heat – low maintenance• Negligible density altitude effect• Plenty of disadvantages too !
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SSA 2012 Convention Electric Gliders © Dave Nadler "YO“ 2012 Slide 5
Electric Power Issue: Batteries● Every battery is a trade-off:
● Energy density● Cost● Lifetime – Cycles, years● Max discharge current● Weight● Safety● Memory effects● Temperature requirements
● Battery Care and Feeding:Balancing, heating, coolingSignificant complexity & cost.
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SSA 2012 Convention Electric Gliders © Dave Nadler "YO“ 2012 Slide 6
Energy Density of Batteries• Gasoline: 13 Kw*hr/lb, relative efficiency of
gas/electric drive (.93/.15) or equivalent:~ 2 kw*hr/lb effective energy
• SAFT Lion 300 w*hr/lb as used in Antares*,around 1/7th effective energy/weight of gas
• Nissan Leaf battery about the same,Kokam Lion about 90%.
• Electric motor weight makes up only a bit...• Experimental batteries heading > 1kw*hr/lb
Not yet real...
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SSA 2012 Convention Electric Gliders © Dave Nadler "YO“ 2012 Slide 7
• The energy you need to climb depends on aircraft weight; same for sustainer or SL.
• After you start a gas sustainer, you may spend a long time climbing to get high enough before crossing the woods home.
• Level flight takes much less power than climb• Battery is ~2/3 of e-propulsion weight & cost• Why make a e-sustainer ? Batteries need enough
energy for a climb ! A powerful electric motor is inexpensive. If you're going to spend weight/cost for batteries, might as well make a self-launch.
Enough Math: Glider Issues
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SSA 2012 Convention Electric Gliders © Dave Nadler "YO“ 2012 Slide 8
Real Performance• Distance in level flight specs sound great, But
With full charge, and you will need to climb...• Cruise range specified as level / sawtooth
Antares 20E example 76 / 103 nm• You're low in the boondocks:
Climb 3000 ft using ~1/3 of battery power,then cruise 70nm sawtooth using ~2/3 battery.
• Published numbers assume you had a full-charge (ie took a tow to launch)
• So far, no electrics for long-distance cruising: self-launch+reserve or sustainer only !
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SSA 2012 Convention Electric Gliders © Dave Nadler "YO“ 2012 Slide 9
Lange Antares 20E and 23E• High-end of glider performance and cost• Antares 20E: 56:1 Max L/D, >800 fpm climb-rate
Typical 9000+ foot climb, >7500 at max gross• Antares 23E: 60:1 at 78 knots, ultimate for WGC
Higher weight, lower climb altitude and rate• >70 delivered (> total of all other electrics)
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SSA 2012 Convention Electric Gliders © Dave Nadler "YO“ 2012 Slide 10
Taurus Electro 15m Side-by-Side• Compared to pure glider, gas or electric adds
50% to price. • With recommended optional larger battery:
– 50 lbs heavier than gas-powered– Stated climb 6500 ft, or cruise ~ 1 hour
• Big cockpit, easy to taxi
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SSA 2012 Convention Electric Gliders © Dave Nadler "YO“ 2012 Slide 11
FES Configuration• Simpler than pylon, retrofit existing planes ?• No pylon drag engine not running, instant on• Drawbacks: Drag from prop (prop plus
disturbed flow on fuselage), prop diameter• Retrofit Issues – Maybe not...
• Weight of non-lifting parts may preclude retrofit• Structural complexity (batt), Round nose
• Possibly a good solution for moderate performance sailplanes. Currently available on LAK-17B and Silent.
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SSA 2012 Convention Electric Gliders © Dave Nadler "YO“ 2012 Slide 12
Alisport Silent Electro (LAK FES)• Nose-mounted propeller 13.5m self-launch• Compared to unpowered glider, about:
– 50% more expensive (less difference after trailer, instruments, and options)
– 25% heavier (160kg-205kg electric-190kg gas)• Climb 5900 ft, or cruise 80 nm
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SSA 2012 Convention Electric Gliders © Dave Nadler "YO“ 2012 Slide 13
LAK-17B FES• Contemporary 15/18-meter glider• Climb 3600 ft, or cruise 62 nm• Only adds 80 lbs over pure sailplane !• See the LAK-17B in the exhibit hall
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SSA 2012 Convention Electric Gliders © Dave Nadler "YO“ 2012 Slide 14
Who Knows This Glider ?
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SSA 2012 Convention Electric Gliders © Dave Nadler "YO“ 2012 Slide 15
Have Aliens Invaded ?
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SSA 2012 Convention Electric Gliders © Dave Nadler "YO“ 2012 Slide 16
Who Knows This Glider ?
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SSA 2012 Convention Electric Gliders © Dave Nadler "YO“ 2012 Slide 17
What happened here ?
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SSA 2012 Convention Electric Gliders © Dave Nadler "YO“ 2012 Slide 18
6000 km range ?
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SSA 2012 Convention Electric Gliders © Dave Nadler "YO“ 2012 Slide 19
Who Knows This One ?
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SSA 2012 Convention Electric Gliders © Dave Nadler "YO“ 2012 Slide 20
Questions To Ask before buying...• Climb altitude at your weight ?• Cruise range sawtooth and level ?• Battery lifetime ?• Measured performance, power & glide ?• Make sure range meets your needs !• Number planes delivered to customers ?• Flight Trial available ?• Customer references
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SSA 2012 Convention Electric Gliders © Dave Nadler "YO“ 2012 Slide 21
A List of Electric Gliders • Eric Raymond's SunSeeker, SunSeeker II• Lange Antares 20E and 23E,
Schempp-Hirth Arcus E• Pipstrel Taurus electro G2, Apis E• Silent electric (original and FES)• LAK 17B FES• Waiex E• Experimentals: Pipistrel G4, Icaré II, eGenius,
Solar Impulse, Lange H2 and H3, Lazair E