FES vs Gas Engine – Finding a Thermal?

On Saturday, August 26, 2017 at 12:15:08 PM UTC+2, Dave Walsh wrote:
Another comment: the only vicious and totally-unexpected spin
entry I ever...

Well that sounds horrible! Are pylon powered sailplane
manufacturers required to demonstrate spin recovery with the
engine out and stopped?

Not flown a Ventus M of any type but this looks like another
example of poor systems design. If the engine retraction sequence
consists of switching off ONE switch (e.g. DG808) or moving one
lever (Antares) then the pilot has nothing to do but control the
airspeed. Many of these other self launch/turbo retract systems
look like an invitation to "finger trouble".

I've heard dozens of stories of pilots outlanding their motor gliders when the engine wouldn't start, to discover on the ground that they'd forgotten to switch the fuel on.

At some point you have to ask - is this a pilot problem or a design problem?

There is a need for a fuel shut off valve. But it's a pilot problem if the pilot

A) Doesn't do a short engine run of say 30 seconds before leaving gliding distance of the home airport.

B) Chooses to close the fuel valve in flight unless there is a serious need to.

C) Chooses to pass on the opportunities to use and follow checklists.

At some point better design isn't going to save those who can't or won't take steps to protect themselves or who wait until they have run out of time by getting too low.

On Saturday, August 26, 2017 at 6:15:08 AM UTC-4, Dave Walsh wrote:
Another comment: the only vicious and totally-unexpected spin
entry I ever...

Well that sounds horrible! Are pylon powered sailplane
manufacturers required to demonstrate spin recovery with the
engine out and stopped?

All pylon-drive machines suffer some degradation of tail effectiveness
because of the pylon wake, much worse with a big radiator as in gas
powered machines. The V2cm in plummet-mode is not real stable in yaw
with much reduced elevator and rudder authority, and I was specifically
warned to be extremely careful with this configuration...

On Saturday, August 26, 2017 at 8:23:08 AM UTC-4, wrote:
I've heard dozens of stories of pilots outlanding their motor gliders
when the engine wouldn't start, to discover on the ground that they'd
forgotten to switch the fuel on.

At some point you have to ask - is this a pilot problem or a design problem?

It is a design problem. A start checklist that seems quite trivial on the
ground becomes unmanageable when you're low, dehydrated, hot, stressed,
exhausted, trying to stay in save position for safe landing when the motor
doesn't start...

I worked with manufacturer and ILEC on this some years back.
The fuel shut-off is required for certification, even though
far more accidents have been caused by fuel valve in wrong position
than fire incidents (fire is why shut-off is required).
Work-around is fuel shut-off that normally remains "on", as is
done in ArcusM for example. That's not possible on some older
designs (for example, fuel can siphon through carb when motor
is in retracted position - don't ask me how I know).

Ergonomic design is not so easy!
The newer systems are MUCH better, but still leave room for screw-up...

Really wish the Lange or Lange type, electrical propulsion system was more widely adopted, for both self launch and sustainer, looks like a great design. I see Schemp-Hirth does offer an electrical Arcus on their web site, but have heard they can not deliver a glider with the the E motor. Schleicher is offering an electric sustainer with the new ASG-32 and the video of an FES ASW-27 self launching was amazing.


On Saturday, August 26, 2017 at 6:58:17 AM UTC-7, Dave Nadler wrote:
On Saturday, August 26, 2017 at 6:15:08 AM UTC-4, Dave Walsh wrote:
Another comment: the only vicious and totally-unexpected spin
entry I ever...

Well that sounds horrible! Are pylon powered sailplane
manufacturers required to demonstrate spin recovery with the
engine out and stopped?

All pylon-drive machines suffer some degradation of tail effectiveness
because of the pylon wake, much worse with a big radiator as in gas
powered machines. The V2cm in plummet-mode is not real stable in yaw
with much reduced elevator and rudder authority, and I was specifically
warned to be extremely careful with this configuration...

On Saturday, August 26, 2017 at 9:30:12 AM UTC-4, wrote:
...it's a pilot problem if...
At some point better design isn't going to save those who can't or
won't take steps to protect themselves or who wait until they have run
out of time by getting too low.

The rate of incidents and accidents clearly shows it is not just a pilot problem.
Perhaps better training and respect for the problem could help,
but reality of the pilot population and incident rate says its design problem...

On Friday, August 25, 2017 at 5:28:52 PM UTC-4, Tony wrote:
Twice in my FES career I have not been able to make it back home
during a self retrieve....

Hasn't happened to me yet in Antares in over 1200 hours.
Did my first trailer retrieve recently in Uvalde; wall of water between
me and home, plus no confidence it would clear before dark...
Only once previously did I land out (again T-storms), but after the
storms passed I dried it off, took off, and flew home. Really annoyed
the other pilots that landed with me ;-)

Lowest I've ever had the battery pack was around 25% after
a long self-retrieve.

http://wingsandwheels.com/class/classified.php?id=685

Not the answer for everybody, but try a jet!

https://youtu.be/HQVWCASrZyw

On Saturday, August 26, 2017 at 12:43:51 PM UTC-4, wrote:
Not the answer for everybody, but try a jet!

I think all of my buddies with jet (JS) have had at least one failure.
None of these contraptions is 100% or even close.
Plan A is always landing.
If it starts, be delighted.
WHEN it DOES NOT start, just finish the landing.

Be safe out there,
Best Regards, Dave

I think all of my buddies with jet (JS) have had at least one failure.
None of these contraptions is 100% or even close.

None of the "sustainer" jet engines are much more than slightly upgraded "toy" R/C engines, with only partially developed Engine Control Units. I am not surprised at the reliability issues, as Bob Carlton and I used these in a jet powered Alisport Silent on the airshow circuit from 2005 to 2008. We carried four engines to make sure we had two operational at any time.

After switching to the PBS TJ-100, a true Mil-Spec turbine with total FADEC control, the problems disappeared. PBS has been manufacturing turbines since the sixties (or before), with much of their product geared toward Auxiliary Power Units for Soviet fighter aircraft and helicopters, (L-39 and L-59 Albatros and Mi-8, among others). After the collapse of the Soviet Union, the engine was redesigned into a pure turbojet, as well as a turboshaft and turboprop, with more sophisticated materials and a vastly enhanced computer controller.

PBS is a large company in the Czech Republic, with over 1,200 employees in a very modern manufacturing facility. They build turbine machinery for everything from hydroelectric power generators to small aircraft. Over 300 employees work in the aircraft division. More than 700 PBS TJ-100 engines are in the field, on everything from target drones to manned aircraft like Bob's airshow planes.

Since 2008, Bob has installed the PBS TJ-100 on his Salto airshow glider, a TesT-14 two seat glider (retractable engine configuration). Sonex Aircraft Inc. has sold over ten subSonex kits, with at least five flying and about five BD-5 aircraft are on the airshow circuit using the PBS-TJ100 engine. We are currently completing the installation of the PBS-TJ-100 in a third Arcus airframe.

In our personal experience with these aircraft, over 750 inflight engine starts have occurred with no failures. Of course, reliability comes from the engineering experience the PBS company has demonstrated, and that doesn't come cheap.

As Dave pointed out, reliability of the Arcus M powerplant and retraction system is somewhat "failure prone." The PBS-TJ-100 engine and Desert Aerospace retraction system has been extremely reliable, but it comes at a high price.