On Sunday, December 13, 2020 at 2:31:33 PM UTC+10, Eric Greenwell wrote:
kinsell wrote on 12/12/2020 3:22 PM:
On 12/12/20 2:56 PM, Eric Greenwell wrote:
2G wrote on 12/12/2020 12:31 PM:
On Friday, December 11, 2020 at 8:17:42 PM UTC-8, wrote:
I actually helped put one of those three into a hangar last weekend. I'm friends with the
IA who just inspected it and an acquaintance of one of the owners who flies it. I've seen
it fly twice and he seems to have a good bit of fun with it.

Here is a review of the Silent 2:
https://www.aviationconsumer.com/ind...ctric-gliders/


My take on it is you can self-launch and do one low save. If you want to self-retrieve you
will need to get an aerotow to maintain a fully charged battery. Even then, retrieve
distance is quoted as cruising at level flight w/o a headwind. If you have to climb to clear
a mountain range, for example, you will exhaust your batteries and may not even clear the
range. This happened to one pilot at Ely last summer. Faced with that dilemma, he used his
battery capacity to search for a suitable landing field. He was fortunate and got a weak
cell phone signal to send his situation to fellow pilots back at Ely. They left the airport
in the dark and returned at about 2 am.

Other considerations a
1. Is the launching altitude specified at max gross weight (the GP15 is not)? If not, what
is the launch altitude at the weight you will be flying it? Will you fly with water ballast?
2. How high do you typically launch to where you fly?
3. Do you have hills or mountains that you will have to clear on a self retrieve?
4. Do you even care about self retrieving?
5. The battery safety at this time has a big question mark (I consider it unproven and will
not fly one).
6. How are you going to recharge the battery on field (you will need a dedicated 20A
circuit). Most remove the batteries and take them to a suitable circuit at the hangar or
motel or home.

Tom

The review was very limited, with no remarks from users of the Silent Electro. That's
important, because the reviewer would have learned that Silent owners rarely end up 100 miles
from home, needing a retrieve. Shucks, that rarely (once every 5 years?) happens to me, and I
fly an ASH 26E. The Electro's lower performance means the pilot turns around not as far from
home, and ends up needing to retrieve only 50 miles out while Al is 100 miles out. And, since
the pilot knows how much retrieve distance he has, he can makes his decisions accordingly.

Again, any pilot considering one should definitely talk to owners that fly them a lot. Jeff
Banks is the Electro pilot I know who has had a lot of good flights in the Parowan/Richfield
area, and usually self launching. Take a look at his OLC logbook for the 2020 season:

https://www.onlinecontest.org/olc-3....t=olc&pi=10497

Tom's remarks are more useful than the review, I think, and point out that where you fly
could make a big difference in the amount of motor duration you will need. Nevada and Utah
are going to be much more demanding than Kansas and Florida, for example.

One point from Tom's remarks I disagree with: Jeff did not use a dedicated 20A circuit to
charge his batteries while he was at RIchfield, but just a standard 15A socket in the lounge
of the FBO.


I agree the article was not not very in-depth.

Interesting that the June 4 flight had a landout after a meandering flight, 122 km scoring
distance, no points due to late submission. If he had been in a gas powered glider, it would
have been an easy self-retrieve.

One thing about the electric gliders, battery voltage isn't constant at all, you are likely to
get a couple minutes of good climb rate, then significantly less with continued motor use.

I'm sure some people have fun flying those things, but others get frustrated with the lack of
power they pack in the batteries. I suppose there were 17 registered in the U.S. until that
Silent 2 went through the roof in Connecticut, making international news. Apparently you don't
always have as much energy left as the little computer display says you do.

-Dave
I don't know how general this is, but I've read the last 20% or so of the battery charge can
only produce a significantly reduced climb power. It was in reference to FES systems. Perhaps
an FES owner can be more specific about the power available at lower charge levels.
--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

Once I get to about 40% remaining, I can only get ~15kW instead of 22kW. Around 30% it warns me to reduce power below 8kW to prevent battery damage, but doesn't prevent me from continuing. I need about 3.5kW for level flight and 8kW is a ~200ft/min climb. Haven't discharged past 20% yet but it was still able to achieve 8kW at that level.
The default charger is 1200W, so even at 110v 10A should be fine, I also purchased a small 600W 'travel' charger that fits more comfortably in the cockpit with me if I outland at a remote airfield and wanted to recharge overnight, or to tour with.