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Got Jet Fuel? Turbine Helicopters > Graupner NH90 Kit

heliVoY
Veteran
Location: NJ

Dave, the turbine actually reached 960c ... at that point the ECU dropped the power down to %80 ... which allowed the turbine to return to a normal operating range, and power resumed at 100% power ...

Here is why it got that hot ... my bell 230 averages in the high 500c range durring max RPM ... i had the heli runnin at full rpm on the ground, and punched in full 12deg of pitch (i had done this regularly on my jetcopter, and had no problems, but the 230 the HP5 is in now is just a "tad" heavier at over 30lbs) .. the heli climbed up with incredible power, and then it felt like it lost power, i though i was going to have to auto there for a second .. but i was able to bring the heli around and as i came in to land, the hp5 kicked in again at full thrust ...

this is what basically happened ... the turbine rapidly was decelerated down from its 96k rpm, without sufficient time for the ECU to respond .. this resulted in the pump voltage being significantly ramped up, with a lot more fuel being squirted into the can .. with the continued load on the rotor head, the turbine heated quickly as the ECU tried to regain its intended RPM on the turbine .... therefore major overheat issue ....

I experimented further with how much load the HP5 can take, .. i can still do full power/pitch climb outs, but i cant just punch it in .. if the load is applied gradually, the ECU has enough time to respond without having to "try to catch up" .....

anyway, check out this video (if you have not seen it before ) .... i think its self explanatory why i overheated it

....... (yea yea yea, i know its a scaler, and im supposed to fly it like one ... , but i just cant help myself ...

)

http://www.voy-tech.net/images/bell3.wmv

http://www.voy-tech.net/images/bell2.wmv

Wojtek

01-17-2004 Over year old.

Dave Hollins
Senior Heliman
Location: UK

Video looks good, but the heli looks very pitchy in flight, why's that?

It's given me more reason to put a turbine in a large Airwolf fus I have

Anyhow, I always thought the Jetcat would shut down on over temp, I was obviously wrong.

01-17-2004 Over year old.

heliVoY
Veteran
Location: NJ

the heli in the video was very pitchy because we had 25mph winds with gusts to at least 35, it was also its first flight out of a hover .. i also still had my pitch curve and throws set up as they were when the HP5 was in the Jetcopter pod/boom setup ... now, i have it flying VERY smooth, and super fast (over 70mph on some passes, no exageration !! ) .. the tail is very responsive, and this heli is super fun to fly !!! ... i am still getting used to pulling out/up of a dives/manouvers wile pushing down on the elevator ..

... Next time i go out, i hope to get some better video of it flying now ...

Wojtek

01-17-2004 Over year old.

edg
Senior Heliman
Location: San Francisco, CA

Actually I was addressing the broken belt to Phil. I was there to watch his Jetcopter fall out of the sky

01-18-2004 Over year old.

HOMEPAGE

heliVoY
Veteran
Location: NJ

which belts was Phil using ? were these the new belts ? I had thought the belt issue had been resolved ? Sorry to hear about your loss Phil (if you are reading this ) .. i know exactly how you feel on this one .....

Wojtek

01-18-2004 Over year old.

edg
Senior Heliman
Location: San Francisco, CA

That was a while ago and I know Phil has been flying it since

I didn't know there were new belts. What's different about them? Sounds like I should replace mine prior to finishing my NH.

01-18-2004 Over year old.

HOMEPAGE

heliVoY
Veteran
Location: NJ

the old belts were made of a diferent material by a diferent manufacturer ... the lower belt was actually coming appart more because of the 96k+ rpm on it, rather than the tension/torque on it .. the new belts are mede by a diferent manufacturer, and are much stronger .. this is why the turbines can not be brought to over 100K rpm now ... since my repair, i have been flyingthe crap out of the HP5, and never had a problem ... Would you be able to find out what belts Phil was using ? I would be very curious, as if it was the new belt, obviously we would all want to know what caused the failure ...

Wojtek

01-18-2004 Over year old.

Phil Cole
Veteran
Location: Redwood City CA

I have one of the early HP-5s, so it had the original belts. I had already scheduled a belt replacement with Wilcox, but he didn't bring have them with him, or something. Bob was actually spotting for me when the belt broke.

The only problem with doing an auto was that it was way out, over some thick brush. I had to land blind. It ended up in a tree, sitting about chest-high with broken blades and a slightly bent boom. Didn't even bend the spindle.

I've flown the crap out if it since without any problem, except when the fuel solenoid wire worked its way loose once. This time the sudden quiet made the need for an auto immediately obvious, and I could see the ground underneath, so there was no drama at all.

It took me a little while to find the problem, since the connector was just sitting loosely on the pins - it would start up no problem, but when I picked it up the engine would quit. I now make sure there is something more than friction holding the little servo connectors onto the ECU.

Ed, if your engine can be set to 94000 RPM you have the new belts. They would have been replaced when the ECU was reprogrammed from 85000. If there is a problem you will see the belt shedding slivers of rudder.

With the 94000 settting I can easily get the engine over 100,000 RPM by suddenly unloading it. The highest I've seen is 105,000 after some tight Cubans going from full power on the upside to a steep auto-like descent coming down. I don't use more RPM due to this. As Wojtek says, the problem is RPM, not the power through the belt.

01-19-2004 Over year old.

edg
Senior Heliman
Location: San Francisco, CA

I will test the RPM.

Yesterday I ran into another problem: couldn't get the turbine started!
It is apparent that the burn won't initiate. Starter motor kicks up ok.
It started just fine the other day.

Stuff I've looked at:

o Glow plug. Even though the existing plug was almost brand new, I put in a new one (OS 8). I pull the wire out a couple of coils as instructed.

o Gas valve seems to be operating ok. When I got home I ran a test of the valve with GSU. Seemed fine.

o Ran GSU test of the glow plug. I'm not sure how to read that this tests out ok. The red Pump Running light blinks every so often. I couldn't find anything in the manual that says if this is ok or not.

During one of the glow plug tests, there was a small exposive "pop". I guess the were some lingering gas in the turbine when I tested the glow plug.

I haven't entirely checked the gas for leaks yet. I will take the NH-90 cover off and do that. I also haven't tried a manual start from the GPU yet. When I tried to start the Turbine at the field with my transmitter I could smell some gas. I could also smell it when I tested the valve. I assume this is normal if it's not getting burned. Maybe not?

Any other ideas, things I could look at, etc...? Generally this turbine has started great every time.

01-19-2004 Over year old.

HOMEPAGE

edg
Senior Heliman
Location: San Francisco, CA

Just discovered on the JetCat site that there was an issue with "false starts" due to imperfect grounding of the glow plug. I'm pretty sure this is the likely cause. I've made the ground strap for it as they describe.
In case this doesn't work, chime in with any other possibilities...

01-19-2004 Over year old.

HOMEPAGE

heliVoY
Veteran
Location: NJ

are you getting the false starts in diferent weather than you usually fly in ?? in the winter, i always alter my gas and plug settings for easier stars in the cold weather ...

Wojtek

01-19-2004 Over year old.

edg
Senior Heliman
Location: San Francisco, CA

Well, it's been maybe a *little* cooler than normal. Still about 60 deg F. I don't think that should be the problem, but maybe?

I just tried manual start with the grounding. Still doesn't work. Any ideas of other stuff to try?

01-19-2004 Over year old.

HOMEPAGE

heliVoY
Veteran
Location: NJ

60 should be fine .... i only have problems when its less than 30 ....

Wojtek

01-19-2004 Over year old.

Phil Cole
Veteran
Location: Redwood City CA

Two things to try:

1. Lower the gas setting in the ECU. If it's too high, you get a rich mixture which won't ignite. The nominal setting is 50%. It generally isn't critical, but I usually have mine set to 40%. Try it either way. New Powermax cans can also cause richness problems. I adjust how much gas I put in according to how full the can is. You would be surprised how little gas it takes to get the engine started.

2. Increase the glow voltage a bit. It really needs to be hot to get reliable ignition.

I use Enya 3s, which have a higher heat range than OS 8s. I tried an Enya 4 once, and it didn't work well at all. Enya 4s are medium heat plugs.

OS-F might be good, since they are really hot plugs. I just couldn't bring myself to do it since they are so expensive.

I get reliable starts in much worse weather than we had over the weekend.

01-19-2004 Over year old.

heliVoY
Veteran
Location: NJ

I have a mcoy 9 in all my turbines ... one has over 15hr on it and still good .... glows hot too ...

Wojtek

01-20-2004 Over year old.

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