Js3 jet catastrophic failure.

On Tuesday, 11 September 2018 04:49:04 UTC+10, wrote:
On Monday, September 10, 2018 at 5:56:11 AM UTC-5, AS wrote:
On Monday, September 10, 2018 at 3:39:49 AM UTC-4, wrote:
One potential problem with multiple jets is if one starts while the other doesn’t but pumps fuel through.
Good engineering may help but there is a known issue there. (PM)

Tom - good point but each turbine has its own controller monitoring what it is doing. If it doesn't ignite and run within the set parameters, fuel to it is cut off.

Uli
'AS'

I have been using the twin Jet Cat P300's for a number of years on my homebuilt experimental HP-18J. I have to say that they can be troublesome, especially if they are not operated according to specifications. I have been using diesel fuel with 5% oil for the bearing lubrication. If you use Jet Cat oil or Aeroshell 500 turbine oil the bearings are reliable for one or two seasons tops. This includes a full summer of self-launches and sustainer starts at our mid-west altitudes. I attended Parowan and Dave was one of my helpers who graciously assisted me retrieve the glider from an out landing. That day the failure was pilot error and not the turbines. I had failed to plug in the CPU's prior to takeoff so the turbines and fuel were just extra ballast that day. During the rest of the event, I used the turbines for sustainer. They started consistently at the airport altitude of 6K and also at flying altitude when needed, sometimes above 10K. With the two turbines, I feel more confident that at least one will start when needed. I typically will do a start sequence for both turbines for a climb and shut one down if I go into sustainer mode to extend my fuel endurance. The problems that I have encountered over the years have been bearing failures, one glow plug ignitor failure and one EGT failure. The turbines are in my opinion good but not great. They still have their issues, two of them are better than one for redundancy and for my application of self-launch. In the mid-west I can take off with a 1K runway roll and climb at 500 FPM. During flight one or both can be started for another climb or for sustainer operations. Operation at high density altitudes and elevated temperatures greatly decreases the performance so I choose to use a tow and use them only for sustainer ops. Here is a link for short clip from our mid-west airport https://www.youtube.com/watch?v=xeQIRrZ7JCU I am currently putting a salvaged ASW-27 back together, I am happy enough with the twin turbines to incorporate them into the rebuild of the glider for the same self-launch and sustainer abilities.

Thanks,
Chris

Thanks Chris, always nice to get actual operating experience.

As I said earlier using larger than you think you need turbines is a great idea as you can operate at reduced power. Ask the airlines why they do reduced power takeoffs. Even the military sometimes derate engines a little to get better engine life although in a shooting war against a near peer adversary I think they'd remove the limits.
Also it is VERY important to minimise deployed engine drag. Done right with adequate thrust to weight the best rate of climb speed should be in the region 80 to 100 knots for most modern 15/18 meter gliders. If it is lower than this the drag increment is too high.
Installation can help prevent fratricide/fuel events in the event an engine has a RUD event and if you are going to run on one engine, they should be independently retractable OR the intakes should be blanked off if the engine isn't running as otherwise the bearings on the non running engine are windmilling and getting no lubrication. It also isn't too difficult to install a Halon fire extinguisher and adequate fire warning sensors. The German self launchers I've seen have a fire warning light on the panel - and no extinguisher.

As for the ASH25 that burned and crashed in Australia in January, we currently have NO IDEA what happened. ATSB is investigating although I do not hold any hope that anything definitive will be found. The wreckage was cleared away before the investigators found out what questions to ask and what to look for. Australian civil aviation is a disgrace.I've seen the images of it on downwind with flames coming out the top of the engine compartment area and the landing gear well.
We did have a similar event some years ago with a Stemme S10 where the fuel system let fuel drip on to the Rotax 914's turbo. Pilot and 4 year old son were killed. Petrol/Avgas (Flash point minus -43 deg)is way more dangerous than Jet A-1/diesel (flash point 38 deg C to 60 deg C).
The expense of self launch/self retrieve? - depends on your priorities. My wife and I drive an 18 year old Honda Accord, only driven by little old couple to airport on weekends :-). I'm not a car person and it has only 149,500 kilometers on the clock. We do live on top of the shop.
Yep, it is a lot of work to install the FIRST setup. Subsequent ones won't reguire the design time.
Winch launching has small margins where if things go wrong they do so very quickly and instant correct, corrective action must be taken. The BGA did look at it and managed to improve the record. I've only ever done a couple of winch launches but hundreds of auto tows from both ends of the cable. I have no interest in doing any more winch/auto tows.
We will know that self launch has come of age when the gliders do not even have a tow hook option. Progress will only come when enough people experiment with piston, jet and electric self launch. I'm not prepared to go the electric method just yet as the current high energy density battery cells are dangerous when shorted, damaged in any way, run down, or indeed suffering from hidden manufacturing defects. It has been 10 years since the Tesla Roadster came out and current batteries have higher energy density but the other defects are still there. Any battery technology announced now is likely 5 to 10 years from being able to be bought commercially. I'm willing to be proved wrong on this but electric gliders need both high energy density and high power density and reasonable cycle life(at least 200 cycles depending on cost)along with resistance to catastrophic failure that results in fire..

Mike

I'm not prepared to go the electric method just yet as the current high energy density battery cells are dangerous when shorted, damaged in any way, run down, or indeed suffering from hidden manufacturing defects. It has been 10 years since the Tesla Roadster came out and current batteries have higher energy density but the other defects are still there. Any battery technology announced now is likely 5 to 10 years from being able to be bought commercially. I'm willing to be proved wrong on this but electric gliders need both high energy density and high power density and reasonable cycle life(at least 200 cycles depending on cost)along with resistance to catastrophic failure that results in fire.

Mike


Mike,

Today only safety is a "concern". Because we are very used to accept that if something with fuel exploded is a normal thing and if a battery catches fire its a big news story. Of course there is a long road ahead to make everything fail and fool proof.

Most of the times you will not land out at more than 100km from your home base.
For the same weight of an internal combustion sustainer system you get the self launch capabilities and a very long retrieve with electric (maybe more than 100 depending in a lot of variables).
For the life cycles, only if you land out in every flight you will get 200 cycles with very safe and proven cells. If you only self launch you can get 400 cycles or more.
Power density is not a problem for this application, neither the energy density. Of course that would be perfect if the batteries weight only 10kg, but with today's 30kg that is not much an issue.


Emir

On Thursday, 13 September 2018 11:52:53 UTC+10, Emir Sherbi wrote:
I'm not prepared to go the electric method just yet as the current high energy density battery cells are dangerous when shorted, damaged in any way, run down, or indeed suffering from hidden manufacturing defects. It has been 10 years since the Tesla Roadster came out and current batteries have higher energy density but the other defects are still there. Any battery technology announced now is likely 5 to 10 years from being able to be bought commercially. I'm willing to be proved wrong on this but electric gliders need both high energy density and high power density and reasonable cycle life(at least 200 cycles depending on cost)along with resistance to catastrophic failure that results in fire.

Mike


Mike,

Today only safety is a "concern". Because we are very used to accept that if something with fuel exploded is a normal thing and if a battery catches fire its a big news story. Of course there is a long road ahead to make everything fail and fool proof.

Most of the times you will not land out at more than 100km from your home base.
For the same weight of an internal combustion sustainer system you get the self launch capabilities and a very long retrieve with electric (maybe more than 100 depending in a lot of variables).
For the life cycles, only if you land out in every flight you will get 200 cycles with very safe and proven cells. If you only self launch you can get 400 cycles or more.
Power density is not a problem for this application, neither the energy density. Of course that would be perfect if the batteries weight only 10kg, but with today's 30kg that is not much an issue.


Emir

OK Please tell us the name/part number of the cells, the cell chemistry and the manufacturer.

Mike

Samsung INR18650 - 25R 2500mAh 30A 3.7V
SONY VTC6 18650 3000mAh US18650VTC6 IMR

Depending on power needed, weight limit and money limit. Any of those.

On Thursday, 13 September 2018 12:57:27 UTC+10, Emir Sherbi wrote:
Samsung INR18650 - 25R 2500mAh 30A 3.7V
SONY VTC6 18650 3000mAh US18650VTC6 IMR

Depending on power needed, weight limit and money limit. Any of those.

Emir, those are both Li Co type chemistry. Not safe. You cannot ship on a passenger aircraft and maybe not by air at all.
Sure you get about 200 watt hours per Kg. You need about 2KW hours to launch a 500 Kg glider to 2000 feet allowing for prop inefficiency. You might want another 6000 feet for a retrieve so 8 KW hours. While the cells may have 200 watt hours/kg you'll need to interconnect them, monitor each cell and at least make an attempt to isolate cell problems. This can drastically reduce the watt hours/kg. I once discussed this with some people at a commercial drone shop (they also flew R/C and used LiPos all the time and had a professional interest for their drones) and was told Tesla had 180 watt-hour cells in the original Roadster but when all the packaging and protection was added they were 108 watt - hours/kg. the cells you mention are about 10 watt - hours each so you need 800 of them. That is a lot of interconnects. What do you think is the probability of of a badly manufactured cell catching fire? What about 800 of them?

Mike

Mike,

For me is weird to fill the glider with 12l of explosive liquid behind my back that makes explosive fumes with a lot of electronics around.

You have risks all the time, even without a motor.

On Thursday, 13 September 2018 20:46:33 UTC+10, Emir Sherbi wrote:
Mike,

For me is weird to fill the glider with 12l of explosive liquid behind my back that makes explosive fumes with a lot of electronics around.

You have risks all the time, even without a motor.

Yeah, but a Halon extinguisher has a fighting chance of putting out a jet A-1 fire. Try putting out a lithium battery fire. The youtube clips of lithium battery fires are quite entertaining.
There's no reason to have explosive fumes from fuel in the glider with proper tank venting and drains. The piston engine motorglider fires that I know of have been mainly caused by problems with the fuel plumbing. Using crummy automotive fuel fittings instead of AN aero types. In the last few years the German glider industry has been a little better but the Quintus engine I fixed recently still had a lot of automotive type hose clamps in the fuel system which is interesting as the fuel injected system runs at 3 bar. A leak could easily ruin your whole day, particularly with the proximity of the hot exhaust not far away.
I have nothing against electric gliders, the motors controllers, props etc are fine but the batteries are a problem, which is the conclusion I came to in 2008. Ten years on I still haven't seen anything to change that conclusion.
BTW didn't the Siemens test electric airplane (an Extra 300) crash recently, killing the pilots? The report I read said that it caught fire in the air..
We had an Antares in Australia catch fire a few years ago while parked in a hangar at Narromine. Seems there was a short between a point on the circuit board of the 300 volt to 12 volt converter and large hole got burned in the aluminum cover until the arc was no longer able to bridge the gap. Fortunately nothing else caught fire.
As I said, experiment away. If nobody does it, progress will not be made.

Mike