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Author Topic: LA46 Engine Speed vs. Maneuvers  (Read 3539 times)

Offline Tim Wescott

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LA46 Engine Speed vs. Maneuvers
« on: July 21, 2014, 11:11:05 AM »
For what it's worth:

Engine: LA 46 with RC carb.
Prop: TT Cyclone, 11x4.5
Airframe: Banshee
Data collection: TUT

The graphs show the engine speed and aircraft pitch rate vs. time.

The engine speed graph is a bit complicated at first: the procedure is that you start the engine with the timer set to hold the throttle in the "flight" setting, and you tach the thing while adjusting the needle as usual.  Then you flip a switch and the engine goes to idle (just like an electric!) for 20 seconds, then it goes to a "launch" throttle setting (and you launch), then finally it goes to the "flight" setting.

Two things I find are of note: first, the amount that the engine unloads in the air, and the steadiness of the RPM once in the air.  It was launched at 9800 RPM according to my tach, yet when it went to the flight throttle setting in the air it flew at over 13000 RPM.  At the same time, if you look at the engine behavior in the loops, you'll see a slight RPM variation, mostly corresponding to altitude, but you don't see any great correlation between engine speed and airplane speed, even though this particular airplane really slows down at the tops of maneuvers.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Online Lauri Malila

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Re: LA46 Engine Speed vs. Maneuvers
« Reply #1 on: July 22, 2014, 10:43:54 AM »
Interesting, Tim.

If laptimes asre same in level flight and upside down, can you find a difference in engine behaviour between inside- and outside loops?

Lauri

Offline Tim Wescott

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Re: LA46 Engine Speed vs. Maneuvers
« Reply #2 on: July 22, 2014, 01:21:37 PM »
Interesting, Tim.

If laptimes asre same in level flight and upside down, can you find a difference in engine behaviour between inside- and outside loops?

Lauri

Dangit -- I had meant to get on before now and mention that AFTER I posted the above I remembered that this was a oh-my-god 4-1/2 second lap when-will-this-end runaway.

The flight ended in a crash, due to -- of all things -- a software bug that cut power in the overheads, so that was the end of test pig #1.

I'll post better data as soon as test pig #2 is flyable.  It's a full-fuselage job without a lot of leeway to shim the tank, so if it happens to show different behavior on insides and outsides we'll see it.  If not, test pig #3 will be a profile with easy to adjust everything, and we'll see then.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Online Lauri Malila

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Re: LA46 Engine Speed vs. Maneuvers
« Reply #3 on: July 22, 2014, 02:08:27 PM »
Ok.
In near future I will get a similar system, it also logs exhaust and cylinder head temperature. Propably not many surprises coming but interesting anyway!

Lauri

Offline Tim Wescott

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Re: LA46 Engine Speed vs. Maneuvers
« Reply #4 on: July 22, 2014, 02:33:06 PM »
Ok.
In near future I will get a similar system, it also logs exhaust and cylinder head temperature. Propably not many surprises coming but interesting anyway!

No surprises is still valuable -- it means that what you thought all along is more likely to be true.

It's the surprises that make for deep learning, though.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Steve Helmick

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Re: LA46 Engine Speed vs. Maneuvers
« Reply #5 on: July 24, 2014, 11:41:50 AM »
If you're using a .46LA, are you also using the stock (POS) throttle? A better throttle might improve the rpm consistency and tracking quite a bit.

How are you collecting rpm data? Optical sensor integrated into the TUT, or something else?  ??? Steve
"The United States has become a place where professional athletes and entertainers are mistaken for people of importance." - Robert Heinlein

In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.  In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

Offline Tim Wescott

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Re: LA46 Engine Speed vs. Maneuvers
« Reply #6 on: July 24, 2014, 02:19:10 PM »
If you're using a .46LA, are you also using the stock (POS) throttle? A better throttle might improve the rpm consistency and tracking quite a bit.

Yes, but that wasn't the problem in this test flight.  I figured out in a ground test two days ago that it was because I had the RPM sensor plugged into the wrong port on the TUT, so the TUT thought it was an Igor timer telling it to go really fast.

How are you collecting rpm data? Optical sensor integrated into the TUT, or something else?  ??? Steve

I'm using a small magnet buried in the spinner and a Hall-effect sensor on the airframe.  It plugs into the TUT, and works great when you plug it into the correct port.

Today I flew test pig #2 and ran out of fuel in the outside loops -- as built the tank needs to be weird to make room for the 'lectronics, and it apparently didn't take to outside maneuvers well.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Howard Rush

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Re: LA46 Engine Speed vs. Maneuvers
« Reply #7 on: July 24, 2014, 08:54:47 PM »
Cool plots, Tim, although the pitch rate sign is backwards. It was interesting to see the + (- on your plot) pitch when the plane was on the top of the outside square.

Is that software bug anything to which my TUT is susceptible?
The Jive Combat Team
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Offline Tim Wescott

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Re: LA46 Engine Speed vs. Maneuvers
« Reply #8 on: July 25, 2014, 10:59:27 AM »
Cool plots, Tim, although the pitch rate sign is backwards. It was interesting to see the + (- on your plot) pitch when the plane was on the top of the outside square.

If that's what I think you're referring to, it's the pitch rate that the aircraft sees when it's flying high.

Is that software bug anything to which my TUT is susceptible?

No, that's the software bug that led to a hurried email from me on the 2nd, telling you that your TUTs would be delayed.  They were sitting in the mailbox waiting for the post-lady when the crash happened, fortunately I got to them before she did and plucked the package out.

It would have only crashed you in AMA mode at any rate -- in FAI mode it would have made the approach lap short.  It effectively made the TUT think that it was rotating twice as fast as it really was, so it saw one loop as two, one lap as two, etc.  So when I did the overhead eight it just cut off in the middle of one of the loops.  I was not on top of my game that day so I stood flat-footed in disbelief for a moment before dashing backwards, which was enough time that I couldn't recover line tension before the splat.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Howard Rush

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Re: LA46 Engine Speed vs. Maneuvers
« Reply #9 on: July 25, 2014, 05:01:43 PM »
If that's what I think you're referring to, it's the pitch rate that the aircraft sees when it's flying high.

Yes.  Seeing data helps you understand what's happening.  Next month I'll talk to you about getting a full, uncastrated TUT.  I'm off to Auburn now to try some new TUT settings I was too conservative to try last week.
The Jive Combat Team
Making combat and stunt great again


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