A10FLYER

Has anyone ever tried to restart their turbine inflight? I figure if it's possible it would only take a couple seconds for the turbine to cool down enough but my concern would be not having enough propane flow to light while the plane was flying.

Anyone willing to give it a try? lol I'm not planning on trying it anytime soon with my MiG but I think a Bobcat would be perfect to experiement on.

Ehab

My Feedback: (44)

You must be kidding!!!! It takes quite more than few seconds to cool down the mass of a hot turbine after shut down then it takes over 20 seconds to get it started again..... meanwhile your plane at 74-80 oz wing loading is losing attiude a little fast while you are waiting for the turbine to come to life AND throttle up!!! Yes, the jetcat has plenty of propane to restart........but that is your least problem....I think

A10FLYER

You're right it does take time to cool down but I don't think it would take 20 seconds to in the air. It may take 20 seconds on the ground with the auto cool down but a good 45MPH wind should help things quite a bit.

How long does the Jet Cat start up sequence (from when you say go till you have throttle control) take? I know with the RAMs you can adjust your ramp up time so it's faster, but hotter.

See, this is why you need a light airplane that glides well...not a Bandit, F-4, or MiG.

Ehab

My Feedback: (44)

"It may take 20 seconds on the ground with the auto cool down but a good 45MPH wind should help things quite a bit"

What the hell are you doing at 45MPH in the air trying to restart a trubine... man you are asking for trouble
The Bandit LANDS around that speed!!!

I always wanted a glider with a trubine on top... A 100" J3 Cub perhaps

Most correct auto start systems will take about 20 sec to throttle control!!!! just the physics of the beast!!

I-NAV

My Feedback: (3)

The cool down is the problem. If there was a way to disable this parameter then it woiuld be possible. I'm not sure if you would get good propane ignition with 50 Kts of wind through the motor. I've never seen a cooldown requirement for airstart on a full size. Anyone know why this is a requirement?

Mike

Ehab

My Feedback: (44)

Hot re-starts!!!!!

mr_matt

My Feedback: (10)

for other applications.

A normal motor (in a normal installation) would not restart, due to the inability to control the propane mixture with all of the air blowing through the motor. You would not really be able to get it rich enough to light

One would need a door or some other way to control the air going through the motor.

Also time is an issue, as mentioned.

And you would need a very large Depends undergarment for obvious reasons

hunterman

Hi Guys,

I have seen this done a few times here in the UK. John Palmer does it with his Kangaroo with a Simjet in it.

Don't think I would try it though.......

Ehab

My Feedback: (44)

Hunterman;

Would you be kind enough to give us more details or have the gentleman, who restarts in the air, do the same?

turbine guy

My Feedback: (266)

I don't have it with me at the moment but,in the latest RCJI mag. I thought I read that the AMT NL has inflight restart capability (Back page advert for the electric start Mercury.)

Made me wonder!

Jake

hobbyboy

My Feedback: (1)

Mike, there is a requirement for cool down on CFM engines of 3 minutes before shut down in-flight or on the ground to cool the engine or better yet to stabilize the engine temperatures before shut down. Bob

Johng

My Feedback: (4)

Many FS turbines need to cool down before restart or the turbine temp will go over during restart. Some can be started right away though.

Anyway, I'd like to see some real refences on this subject - since I have a U-2 that I'd like to power with a turbine whenever I do get around to putting it together. THat one could concievebly stay aloft by means besides the engine. Being able to shut the engine down and then restart later would be pretty cool. I don't think I would ever try to restart and engine that quit on it's own in the air.

hunterman

Hi Ehab,

Yeah I have seen a couple of guys do it with the Kangaroos. They tend to take them way up high, cut the engine and do some aerobatics in the glide before relighting. I guess this would allow the engine to cool down before a restart.

As far as I know they don't do anything special before restarting the engine.

hobbyboy

My Feedback: (1)

John, there is no minimum time between start/shut down requirement for any full size turbines that I am aware of. The requirement of cooling the engine before shut down at idle is for thermal stabilization (usually 3 minutes). Now having said that, you do see a little cooler peak EGT during the start if you let a turbine engine go to max motoring before introducing fuel but again this is a technique rather then procedure and is not required by CFM or Pratt on the CFM56 or JT8D series. By using the max motoring technique you may exceed the max motoring limit during a non-normal start.
Anyway, I don't see how you could have an overtemp problem on a model turbine because in-flight there would be such a high airflow over the EGT sensor ( if not, I guess there is no need to restart:-) ) and even if it was at 700c, it would decrease almost immediately to below 100c. It would be interesting to programming the ECU to recognize a rapid EGT decrease, compare it to the thrust lever position and to start a modified automatic in-flight restart sequence?

Bob

JohnVH

My Feedback: (38)

I dont have mine with me either, but I believe it does say that!

Johng

My Feedback: (4)

Never said there was, but there is a max temp for all, so some amount of time ( dependent on conditions) is required between shutdown and restart for those that may exceed limits on startup. For instance the PT-6 on aircraft that I am often around ( and in) often take between 10 and 15 mintues to cool into a safe starting range. Many others don't need to wait.

Looks like there shouldn't be a problem for air-restart.

hobbyboy

My Feedback: (1)

John,I'm not going to make a issue out of this .I will tell you how it all works in a PM. Bob

SECRET AGENT

My Feedback: (18)

I heard (never trust what you hear and question what you see) that the new BMT turbines won't need propane to start, could make in flight re-starts easier. Who knows, I barely have enough time to say "OH S**T" when my motor cuts.

garrett_mcdonal

The BMT 120-KS does, indeed, start on Kero. Those who have seen my engine start and run have been amazed by how not only simple it is, but also by the low EGT throughout the start.

I haven't tried an in-flight restart though.

The kero start also significantly simplifies the on-board installation. Very few components to deal with. What you see in the photos is everything needed on-board.

Regards,
Garrett

Ehab

My Feedback: (44)

" and even if it was at 700c, it would decrease almost immediately to below 100c. "


After landing my Bandit and shutting down, I use a leaf blower that is SUPPOSED to deliver 150 mph wind to cool down the plane. I watched the turbine temp go down fast but not immidiately, it took quite a few seconds. ASSUMING you are flying at 150 mph and shut down and try to start again, the temp will STILL be seen by the ECU as too high and abort retatrt. THIS IS the case of my Bandit that I can speak of. So, I suspect that hi temp and propane not been rich enough will prevent a restart UNLESS you reprogram the ECU and fly a much lighter plane for a better glide ratio!!!

hobbyboy

My Feedback: (1)

I will go out and measure the time it takes, but my P-120 seems to cool very fast after shut down ( maybe 10 seconds to get down to 150c). It also has a lot to do with what engine you are running. You are right, that there is not much time to go through the start up sequence This is why it probably be better to have the ECU determine if it is a flame out (fuel flow, thrust lever angle, EGT vs RPM) and to have a modified automatic in-flight start attempt sequence. There would have to be additional protections that would recognize a failed sensor vs a flame out too. I really would think that getting the propane to light off with all that turbulence would be the problem. I really would have no interest testing this out but it would be nice to have a flame out protection/in-flight restart program available. The BMT looks the most promising. By the way, I have tried and tried to buy one of these kerosene only engines and the BMT importer just keeps telling me that he will get a hold of me when they come in. Are they really available? I would love to get away from propane. Thanks, Bob

BMT

Hi Hobbyboy,
The inflight restart capability you have on your wishlist could well be possible given enough time to develop. This capability is on our list of projects as well but has not progressed due to other R&D priorities. Apart from being a fairly involved software issue the main chalenge is the rapidly changing conditions within the engine once it has flamed out. A considerable heat source would be required to get combustion going again while the mass flow within the engine is still quite high. The best chance is with a fuel injector ignition system such as we have developed for the BMT KS series engines. Of course the best defence against flameouts should be a well integrated engine/electronic design in the first place, coupled of course to good fuel installation practice. Here we believe to have an advantage as our turbine installation is much simpler than any other autostart system out there. If you look at Garrett's post you can see just how few components are involved, even discounting the fact that there are no propane tanks or valves. Yet inluded is the unique added feature of an automatic fuel priming system to remove air from the system at each start-up.
For more info on availability mail me off list at [email protected]
Cheers
Andre Baird

hobbyboy

My Feedback: (1)

Thanks Andre,
Your fuel system in definitely leading the industry in the model turbine arena. I have always thought it would be next to impossible to have a kerosene only start up on such a small turbine engine using a low-pressure fuel pump. It is amazing that you can atomize the fuel on such low pressure/low temperature and light it with a glow plug! Another problem would be keeping the injector clean. Apparently you have found a way to avoid a reliability issue with a clogged injector. I wonder if this system opens up the possibility of a true diesel only injected model engine!! Good job! Would a capacitor type igniter be an option for your engine? I know the glow plug is so much simpler but it seems that air/fuel mixture would be less critical with a high-energy ignition system and in-flight re-starts could be more of a possibility. You could even run with the ignition on for take off’s and landings for extra protection during critical phases of flight. On another note, can I order a BMT KS120 direct from you in the US? Thanks, Bob

garrett_mcdonal

Hi Hobbyboy,

I actually asked Andre the same question regarding doing away with glow plugs. There are a bundle of other problems that come with the benefits and, on average, the glow plug is the simplest way to go about it. Andre may chime in again with an explanation. If not, I'll see if I can dig out the email and paste in the reasons.

In terms of the injector, I haven't had mine clog up once. I pulled it out the other day just to check the spray pattern and it was still as good as new after about 75 starts.

The critical component in the kero-start sequence isn't the hardware so much as the fuel flow algorithym, coupled with the ramp sequence software.

In order to pull off the kero start, Andre has developed a means of monitoring the actual fuel pump rpm to determine exact fuel flow, even when the fuel pump is subjected to a mechanical loads such as pump shaft restriction or different length/diam fuel tubing between the tanks and the pump or the pump and the engine.

Again, I'm sure Andre will chime in with further details.


Regards,
Garrett

Ehab

My Feedback: (44)

So, Is BMT available for sale in the US?

I heard about all its good abilities years ago thru desert winds who are out of business under that name anyway. I would like to have more options in the US other than jetcats and amt's which I have flown and enjoyed their reliability...

For me, I'd rather see improvements in fuel cosumptions, reduction in weight, more sophisticated ECU's, better throttle repsonse than to see in flight restarts. BUT, If you guys can do it w/o losing any other qualities, then I'll take it for my $$$$

BOB: did you check the spool down and temp decay in your P120?