Js3 jet catastrophic failure.

I've been digging around trying to find out what the process has been for pilots that have added jets other than the MD-TJ 42. This group seems to have a lot of knowledge on this niche subject. The jets are coming down in price and getting a lot more reliable to start, so it seems it would be a more considered option for a lot of pilots. Are there many self-installs, or are there a handful of companies that specialize in the retrofit?

On Monday, October 26, 2020 at 6:33:02 PM UTC-4, wrote:
I've been digging around trying to find out what the process has been for pilots that have added jets other than the MD-TJ 42. This group seems to have a lot of knowledge on this niche subject. The jets are coming down in price and getting a lot more reliable to start, so it seems it would be a more considered option for a lot of pilots. Are there many self-installs, or are there a handful of companies that specialize in the retrofit?

You didn't say where in the world you are but for the US, Bob Carlton in Moriarty would be my first choice to call, if I wanted to have 'my ride pimped out' with a jet.

Uli
'AS'

P.S.: Bob - as soon as that lottery thing works out for me, I'll be giving you a call! ;-)

I'm in the US and familiar with Bob. What he does is fantastic, but I'm more curious about some less expensive, less pimped out options. Everything I've seen of his so far uses PBS engines which are extremely expensive. The Jetcats and some other options are much more affordable and I know there are pilots that use them.. I'm wondering how they went about the retrofit.

a lot more reliable to start
mmm, on the RC side I'm not sure they are much better since I last posted on this thread couple years back. Since then:
-bad egt probe
-bad glow plug
-newish turbine had stiction on the starter motor but if you could reach in and spin the bendix by hand it would start.
-another with bad starter motor.

But no catastrophies. Above were all fixable for a price.
Darren

I've been operating the microturbines for about 15 years (only up to the 90lb thrust class) and all those problems have been addressed for much more reliability. The EGT probe sheaths were switched to much higher temperature materials and were moved internal to avoid being deflected in any way that would fatigue the material to a point of breaking. The glow plugs were horrible and failed all the time. They used to be the ones used in RC nitro engines but are now ceramic and have proven to last way beyond multiple service intervals. The starter motors have transitioned from high friction brushed motors to virtually zero friction brushless. Same with the fuel pumps. I'm just addressing Darren's list but there are a lot of other improvements. The biggest issue I ever found consistently with starting the microturbines is variations in the atmospheric conditions that don't jive with the programmed start parameters which are set for a most likely "window" of conditions. But there are operator techniques to remedy even this scenario on the fly.

Obviously I'm biased toward the jets but always looking for the failure stories because it motivates me to figure out how the potential for those situations can be minimized.

I'm actually reporting on turbines less than 5 years old and it was a ceramic "glow plug"(igniter) that failed. In the case of the Jetcat starter motor I was able to fix that myself which was nice.
Darren

I'd be curious to know which Jetcat models. The P300 and P400 have the ignitors situated differently than the smaller engines and I found that the wrong location contributed to faster wear. Also, the most typical reason for failed ceramic ignitors (that I've experienced) was from too much voltage. The ignitors that Jetcat uses are very happy with 6V and that's plenty for consistent starts but I know of a lot of guys that crank theirs up. Was the starter problem perhaps a jammed open bendix that was holding the o-ring against the compressor nut? Or were they disengaged and the motor itself was jammed up? The former is always an easy pre-flight fix but the latter is obviously the motor. If that was the case, is it brushed or brushless?

I'll admit I'm a bit of a jet addict and always trying to eliminate their nuances. Sorry if this is the wrong place to be posting the technical stuff but maybe it will help others.

wrote on 10/26/2020 3:32 PM:
I've been digging around trying to find out what the process has been for pilots that have added jets other than the MD-TJ 42. This group seems to have a lot of knowledge on this niche subject. The jets are coming down in price and getting a lot more reliable to start, so it seems it would be a more considered option for a lot of pilots. Are there many self-installs, or are there a handful of companies that specialize in the retrofit?

Chris Esselstyn has converted a Schreder glider and an ASW 27 to twin jet self-launch. You can
probably find his contact info on the SSA website or the FAA aircraft registration lists. Both
have flown successfully at Parowan during the annual motorglider event there.

--
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

On 10/26/20 9:39 PM, Eric Greenwell wrote:
wrote on 10/26/2020 3:32 PM:
I've been digging around trying to find out what the process has been
for pilots that have added jets other than the MD-TJ 42. This group
seems to have a lot of knowledge on this niche subject. The jets are
coming down in price and getting a lot more reliable to start, so it
seems it would be a more considered option for a lot of pilots. Are
there many self-installs, or are there a handful of companies that
specialize in the retrofit?

Chris Esselstyn has converted a Schreder glider and an ASW 27 to twin
jet self-launch. You can probably find his contact info on the SSA
website or the FAA aircraft registration lists. Both have flown
successfully at Parowan during the annual motorglider event there.


Chris posted extensively to the earlier version of this thread,
9/17/2018 he talked about his uncontained Jet Cat rear turbine wheel
failure on his HP-18 conversion. Easy to find if you Google
rec.aviation.soaring.

That ship is Miss August 2021 if you have the new SSA calendar.

Dave

I really like what Chris has done and have reached out to him. What's on my mind is two 40kg class engines. You would have 175lbs of thrust, and in the event of one failing, you still have an adequate sustainer. I'm estimating the system would be around $25,000 (15k for the engines and 10k for the install). Where I am guessing entirely is the cost of the install, and if there would be enough room for two of this size engine. Two P300s are 10.5" wide next to each other, while two 40kg motors would be 11.5". So it seems they would fit in a lot of cases.

Interestingly, the P300 has a bit of a track record of catastrophic failure.. I'm sure there is an explanation out there as to why, but I followed many incident threads and I never found a definitive answer. There was speculation that the rotor sizing resulted in a resonant frequency that was causing stress on the bearings.