olnico

In view of the recent announcements from Xicoy and Kingtech about rapid auto restart systems for our turbines, I would like to start a discussion thread about this.

Richard posted a very relevant comment on the Kingtech ECU thread:





My opinion on this is very much in line with Richard's. At this stage, I don't see the point of having an auto restart function as a band aid to badly setup fuel systems.

Air bubbles = fix the problem.

Most other situations = danger of fire.

What if the engine flames out while throwing a giant flame at the back and the ECU is trying to re-inject fuel ( example in case of a bearing seizure or pipe implosion ) ?
What if the plane crashes, a fire condition starts and the ECU is pumping fuel into it?



What is your thoughts about this?


I would be very interested in getting the thoughts of the community about this. We've had this function available for years now but never activated it for hobby use. We actually got denied airworthiness due to this function on military ECUs.

basimpsn

My Feedback: (5)

I think not knowing what cause a in-flight flameout and depending on a "auto restart function" to kick-in could go either good or bad...I could see a big distraction to the pilot waiting for a restart and losing valuable altitude and airspeed....Instead of flying a crippled plane back to the runway.

Gaspar

In JetsMunt web site there are some useful notes regarding this subject when used on JM engines.

http://www.jetsmunt.com/wp/2016/07/1...tart-function/


Gaspar

olnico

Great. Thanks for the heads up on this, Gaspar.
I think that it is particularly wise to have this function disabled by default. Enabling this being at the responsibility of the user.

Two things where I 100% agree with you:

1. "Restart function is an emergency procedure and places a high stress on the engine ancillary components. The starter and ignitor are fed with extra power that is not used in normal startups, this places considerable more wear on them, also the engine is subjected to abrupt temperature changes that could shorten its life."

Yes, absolutely. There is a temperature surge in that situation. The combustion chamber and rear bearing see an abrupt rise of temperature, thus increasing the warp/ wear of these components.

2.

• FLY YOUR PLANE. Leave the throttle at mid setting and fly your plane for a dead stick landing.

Yes. The priority is alway: "Aviate" then "Navigate"
"Aviate" meaning: keep your speed, control your roll to stay within reasonable banking limits.
"Navigate" meaning: within the available amount of energy left, try to bring the plane back to a portion of ground where a safe landing can be made. There must be some energy left for the flare.

I have a fantastic demonstration of this from Jorge Escalona:

https://vimeo.com/164908888 And Rei Gonzales:

https://vimeo.com/164937613

FenderBean

Oli I think this system is nice for things like unexplained flame outs or a small air bubble, in my opinion this is an emergency function. Something to get the turbine running again to give you a better chance of landing the jet and preventing possible crashes or even worse a major accident due to a crash. Flame outs happen even with proper fuel and vent systems.

CraigG

My Feedback: (40)

In other words, its a risk management issue. The risk of a dead stick landing versus the risk of an inflight restart.

In my experience, the vast majority of flameouts are fuel issues and the majority of those air bubbles.....so small that there is often no evidence of them afterwards. Not a huge risk to restart assuming temp, rpm etc., are within limits.

I would treat any flameout as though the engine was not going to restart. If it does, great but continue to land as soon as practical to trouble shoot. If you have the altitude/speed/position for a controlled dead stick and don't want the restart, just "shut down" the engine.

I think having the capability/option is good and let each person decide for themselves if or how to use it.

I also think telemetry is an invaluable tool in these situations to let you know the status of your turbine in real time.

Craig

egldriver

Absolutely agree. An alert on the gsu at next start up would be great in case a restart was attempted by the ecu unknown to the pilot

cmp3cantrj

Looking at Gaspar's advice I observe the following Catch 22

Restart takes up to 15s.

So if you have less than 15 s worth of height/ speed restart isn't going t help.

If you have much more than 15s worth of speed/height then a safe deadstick landing should be easy.

If that isn't enough for you then you have no business flying a turbine model. I just looked back though a recent turbine flight on my onboard video - and the last complete (360degree) circuit and landing took only around 30s.

At best it might be useful for the larger models.

CraigG

My Feedback: (40)

If it took 15 seconds I would agree with you. The Kingtech new ECU thread just above this one says restart in 3 seconds after fuel interruption...in which case I would agree with myself.

Eddie P

My Feedback: (4)

We can see in the videos that are out there, that the re-start is quite fast, almost instant depending on how the flameout and re start occur. About 3 times faster than I expected to see initially.

There is an obvious issue here that Oli brings up - this is the Elephant in the room. The mental state of expecting an auto re-start of a failed engine in flight, with the primary demands being proper flight path control and energy management of a dead stick high wing loading aircraft to a dead stick landing presents a severe conflict of intent for the untrained. It adds exponential complexity with the options a pilot has now been presented with. Some options being good, some bad, some likely not considered. Continue to land from the original plan? Add height for a new and better approach? Keep flying? How to handle an in flight fire or torch with no in flight fire fighting capability? Or unknowingly land while turbine is re starting causing other issues on the landing? Or worse yet the engine is starting while aircraft is breaking up?

For me I would like the option for in flight re starts. But knowing these issues make the flight substantially more complex in planning and execution as well as risk management, and being able to demonstrate the knowledge and judgment to handle this - it all has to be a part of the equation. I think for the majority of hobbyists who won't likely bother to consider the issues because "this their is their fun time" and may not want to deal with the demands that a more complex situation needs - Sadly, this may be too much to handle successfully if they happen to wind up in a more judgment dependent, time critical situation.

I would support the initial settings to be auto start off. Maybe the user could get those turned on via some sort of online training program and then the "codes" to get it turned on. Whatever that may entail. Just an idea. Keeps the un-inclined from biting off more than they can chew. But does not protect against stupidity, lack or recency or carelessness; nothing in a voluntary community ever really does.

mr_matt

My Feedback: (10)

I am from Missouri on that claim...."Show Me"

gunradd

My Feedback: (9)

Hello Matt

I count 6 seconds but still pretty fast.
<iframe width="560" height="315" src="https://www.youtube.com/embed/GUt4Kjm9oTY" frameborder="0" allowfullscreen></iframe>

gunradd

My Feedback: (9)

I feel gaspers article was very well written and totally agree. This is not for everyone and nor is it always going to have positive results.

I for one in my big F15 would not use this because the odds of it working in time are slim to none with it being a single. If I had a big twin I would for sure want it enabled or a slick sport jet that had a chance of being restarted.

The best thing is to not have a fuel problem in the first place. Sometimes things happen though. I recently had a UAT problem that was very hard to torubleshoot. Problem was when flipping inverted I would get a pop and on a few times a flameout. I tried running it on the ground inverted and was unable to duplicate. I also removed all the tanks and went through them and checked vents and could not find any problems. The UAT was sealed so only option was to just replace it. After replacing all problems went away. So I took the UAT apart and found the filter element was not properly secured when it was manufactured. This let fuel and tiny airbubbles bypass the UAT filter and cause problems. Auto restart would have helped me here but still at the end of the day I had to fix the problem but the only way to know if it was fixed was to fly it after each time I changed something.

Like anything it has pros and cons.

Dblex

My Feedback: (81)

Evolution in anything we do in life is always scary. You will always have pro's and con's. But at the end of the day, It is up to the individuals to make those decisions. There are risk in everything we do in this hobby. If I have done everything I can do in my build to prevent a bad day, then hitting the switch is a no brainer for me. You will always have failures in anything we do.
1. If you don't tie wrap all your fuel lines properly, then you hold the risk of pouring fuel into the plane on re-start.
2. If you don't load test servos for binding, you run the risk of servo failures in flight.
3. If you don't properly test rx installations, you run the risk of interference.
4....
5......
6.........

I could go on and on, but the list should be familiar to those at this level of flying....

In short, it is a pretty awesome evolution of the ECU platform... COOL as heck to have this in the golf bag. You may never use it, but it's there if ya do!!!

Thanks for the opportunities gunradd

mikedenilin

My Feedback: (67)

Here is a video clip of restart on my Super Viper with Ace Turbine

https://www.facebook.com/mike.d.lin/posts/10201670373318896 I later found that one of the flame out was caused air bubble in fuel filter and one by improper set up of acceleration adjustment.

Mike.

stevekott

What about a restart after a failsafe shutdown?

Recently I lost my FeiBao F4. I was out pretty far to the left. There was a small tower out there with a dish antenna on it .. and I'm guessing it might have been a 2.4ghz transmitter. Long story short telemetry said I lost signal for 1.5 seconds barely long enough to feel anything on the sticks but long enough to put the turbine into a Fail Safe shutdown (per ECU). I was flying back towards me for 15 seconds but had to make a belly landing in the desert. Looked ok from a distance but busted up the nose, wings, canopy too much damage to repair.

To me it seems like it's about 50/50 with the results from a flameout. Some of my best landings have even been with a flamed out engine. But if you can't make the runway your chances of tearing up the airplane are pretty high,

So will these new re-start systems re-start after a fail-safe, once the signal returns?

olnico

Well obviously, a tiny 60 size turbine will restart in seconds due to the little inertia of the rotating assembly and the shorter ramp response.
But this will be multiplied by 2 to 4 for larger sizes like 100 to 200 N...

olnico

If the turbine has dropped outside of the restart envelope when the signal is regained, it will not restart.

olnico

Well, typical example.
On this video, you got a flame out. Announced it, but you didn't try to turn back to the runway to make a dead stick landing. You turned away from it, kept the nose high flying straight ahead till the auto restart system kicks in. What if it would have kicked in while you were crash-landing the plane or during a possible stall?
This system took you out of the essential loop prevailing in aircraft emergency condidtion:
1. Aviate
2. Navigate
3. Deal with the technical

olnico

It is interesting to see how this new function is adding a new dimension in remote controlled models flying.

It is not challenging the pure flying skills of the pilot.
It is challenging his flight management skills.

It will require him to assess priorities in a very short time and make a sound decision within seconds, re-evaluating it in a decisional loop, while keeping the energy of the aircraft and elaborating a safe trajectory to the ground. The reassessment loop will have to be based on the perception of the engine state ( emitted sound,or RPM/ EGT with telemetry), aircraft energy, remaining height, extrapolated trajectory ending point. Very, very complex for a non professional pilot, not trained to this routine.

Up to now, engine failure scenarii would end up with a relatively cold engine getting back to the ground, relatively close to the runway. From now on, we are going to see a lot of models getting back to the ground away from the runway, in a UAS ( Undesired Aircraft State ) with engines at 700 c+.

Vincent

My Feedback: (61)

For me I'm thinking I will need to have good discipline because in a flame out situation especially with a heavy scale jet it requires immediate response by the pilot. If I hesitate and set up for a restart and it doesn't happen I just messed up and I'm ditching. I have a restart capable motor coming and these are things I am thinking about now.
Vin...

SECRET AGENT

My Feedback: (18)

I would think that if you had a twin configuration where the motors are far apart like a C-17 for instance, you would want auto restart instead of possibly losing the jet in a turn.

cmp3cantrj

If you look at the Jets Munt demo videos you will see that it takes much less than 15 seconds. HOWEVER the advice of the guy that made the video is that you need 15 seconds of height for the restart to be useful.

Frankly both Ace Jets and Kingtech are comparatively new to the business. Gaspar has been making ECUs for around 18 years (before Jets Munt he made ECUs for Artes jet and his ECUs are used in many other turbines - including Kingtech until recently). Consequently I would trust him to have experimented more throughly with this than the others.

cmp3cantrj

Actually I reckon a deadstick landing would have been easy enough from the point you flamed out. You had plenty of height !

If the restart had failed you would have been in trouble, if it had worked but taken a bit too long you would have been in worse trouble!

cmp3cantrj

The Jets Munt one won't. There is a good reason for that too - which is that it is likely that the signal might fail again quite soon - and the last thing you want is for the restart to be interrupted!