Albatross

My Feedback: (7)

Has not been the happiest day of my life yesterday night. I took my airplane and decide going flying just a little bit before the sunset.

1st flight the engine behaved wonderfully, allowed me to practice 3D, things where just going so right!!!

2nd flight, everything looked fine, about the middle of the flight I did an inverted flat spin. I ended the flat spin inverted, then decided to flight around just above the runway still inverted at low speed. When the airplane passed just in front of me, I started adding some power, wanted to see if I could enter a hover from inverted flight (too demanding?).

I noticed how the BME 110 started responding to the throttle stick input, at about 45 degree (still inverted) the engine died. The airplane was at 100 ft above the ground. I immediately leveled the airplane. By then, the airplane already passed the central point of the runway and was too low to glide and try a safe landing.

All I could do was controlled crash. The airplane fell like a rock from the sky.
The damage is large and could not be repairable.

My recollection of the flying session events ever since the minute 5.5 is that I exit the flat spin inverted, then I continued inverted just before the actual crash, minute 7.4 . ( See attached plots in my next post))

I am separating the RPM plots and the barometric altitude. The plots show the last dramatic moments of my airplane (minutes 7.4 to 7.5 approximately). The RPM plot shows exactly when the engine died.

There was plenty of fuel; the engine temperatures were just fine. I tested the ignition battery and it is OK.

What went wrong in this picture?
Did I ask too much when I decided to start hovering the airplane from low inverted pass?
Did I run the engine inverted way too long?

Albatross

My Feedback: (7)

As promised, here you have the flying data:

rmh

Maybe I can't read a chart - the rpm never seem to hold at any given rpm during the flight .
possibly you picked up a puddle of fuel in the crankcase .

Albatross

My Feedback: (7)

You’re right, seems like the plots are kind of saggy, perhaps noise or faulty readings every now and then. All I could do is to look at the "RPM envelope" to make sens out of them.
BTW, I have other RPM plots that look alike in this regarding.

By looking at the last seconds of those plots, there is a ramp from 2000rpm up to 4000 rpm, then the engine decide to die, the RPM plot dives to zero, while the barometric altitude does however at lesser degree. This is exactly when I tried to hover from inverted.

Dr1Driver

Two things immediately come to mind:

1. It's possible your clunk line wasn't flexible enough to allow the clunk to stay in the fuel during inverted flight.

2. It's also possible you have dirty fuel and a clogged carb. Gas engine carbs have some incredibly fine filter screens inside and even a little dirt can clog them.

Dr.1

Albatross

My Feedback: (7)

I only installed one filter just prior to the fueling line of the gas tank.

I removed the filter that goes from the tank to the carburetor. That was part of the steps toward the elimination of my carburetion issues since the needles of this engine are way too sensitive. The engine performed flwaslly for more than couple of weeks, I thought I had already the engine of my dreams.

The clunk seems to be OK, however I will re-check.

Was the venting line way too long submerged in gas; therefore the mixture became way too lean during those couple of minutes?

RTK

My Feedback: (1)

Does the ignition still work??, bad switch, hall sensor,,,,,,,,,

Albatross

My Feedback: (7)

One thing I realized from the plots. I tagged the events.
It is way too low my idle RPM?
Look at the plot at the pits area prior to the WOT test @ ground.
The plots show 1500 RPM. Did I exit at way too low idle RPM, then during the long inverted flight the engine just died due to lack fuel (lean)?

Albatross

My Feedback: (7)

Hi RTK:
I will verify the set; I installed a smart fly kill-switch. There might be a clue in this area; I recall that the LED pilot did not come lit on; even so I was able to start the engine. Although that was not the 1st time I see this happening . Good point!

rmh

I NEVER use a filter in the fuel lines -ever - prefilter the fuel then use NO GoDm fill valves -just a bubble tight T setup with two lines . those valves seep n leak -
one feed -one vent .all you need
that is gas basic 101 in my book --eliminate ALL extra pieces .
as for idle - if the throttle is constantly being goosed (per your diagram )-I really would suspect fouled plugs also could happen
There is a ltearning curve to these things as I am certain you know . find a good usable idle speed, which will not kill if the model is sliding downward . this will kill many engines with the increased load on the prop.

RTK

My Feedback: (1)

Albatros--It appears to me from your graph that your engine crapped out at 4000rpm. I believe you said it was responding to throttle stick then went dead. It appeared to have a steady climb in rpm for about 10-15 seconds, then wham, dead and just prior to that climb in rpm you were not below 2000, or at least that is the way I am reading it.

krayzc-RCU

My Feedback: (31)

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Don M.

My Feedback: (5)

Man the hobby is going the way of F1 [X(]

Albatross

My Feedback: (7)

That's correct RTK; the engine went from 2400 RPM or so up to 4000, and then died.
Indeed I never was at 1500 RPM during those instants.
I only wanted to point about that fact. If the low idle went even lower during taxing, would it be a sign of what was about to happen?


Dick ,I agreee with you, the only filter I used was the pre-filter. The fuel line goes directly from the tank to the carb.

onewasp

Yup.
And that isn't good either.

Edit addition: ------on the other hand perhaps computer print outs could replace the Sears catalog in the out house? A fitting 'end' (pun intended) for many of them.

RTK

My Feedback: (1)

Gotcha, I don't think that could or would be related to what happened to you. Maybe a sign of a trim, linkage adjustment or big climate change.

RTK

My Feedback: (1)

For some it's fun to play and experiment with technology in this hobby, others wish not to, whatever floats your boat. I myself have as much fun building and experimenting as I do flying. Weird huh but that's what makes it fun for me.

Albatross

My Feedback: (7)

That's right, whatever can help to make the model flight better or in this unfortunate case, useful to investigate an accident is OK for me. Common sense prevails, without high tech we have been able to flight. However RC airplanes is all about technology, even during those days when they radio controled airplanes using valves operated radios ... by then, that was high technology, right?

ram3500-RCU

My Feedback: (221)

Pressure in the cowl changes with plane attitude. I use velocity stacks and I run a tube from the carb back into the fuselage to help with this, and make sure I have plenty of exit air. Some guys cheat on this for the sake of esthetics's, but this is unwise. Don't think it would be the tank clunk as the plane would probably have been in a nose high attitude when inverted and slow, as you came across. I also use a high idle setting for inverted stuff so as not to 'load her up', and work the throttle as it looks like you did.

I did have an engine quit on me due to an older tank stopper cracking and coming out. Didn't catch how old the plane/ fuel system was.

I like your approach of trying to get to the bottom of this. Hope you do.

Tired Old Man

My Feedback: (1)

The idle rpm is probably not a factor. 1,500 is actually a bit high for most of my stuff. Prop size has a tremendous impact of idle speeds. Larger permits lower idles. I would guess it's more a needle adjustment issue and you just need to tweak things a little more. The telemetry is good but the way the engine wants and likes to run takes precidence over "hard" numbers. As far as available duration of inverted running, you should be able to do that until the tank runs dry.

Albatross

My Feedback: (7)

Thanks for the reply.

-The gas stopper/fuel system is old. I installed 1 1/2 year a go when I ground tested the engine in Wisconsin before moving back to Mexico. While my moving took place and I could found a place form me here, that system did not touch the gas for almost one year long. Then I start using the same gas tank 8 months ago. I took apart the assembly recently to verify all was OK.

-The openings on the cowl are big enough; this engine has been baffled to avoid overheating issues.

-I ran a tygon tube from the diaphragm to the fuselage to cover on-air needle miss adjustments due to atmospheric fluctuations.

The night before I was doing a lot of flight sim, practicing "ruder control while airplane inverted at low speed". I exited the flat spin inverted intentionally for me feel the real test. However that was the 1st time ever I tried to go from low RPM inverted flight/inverted harrier to hover.

I reviewed other flying session from the day before, looks like I always have consistently idled this engine at 1500 RPM, so that seems to be OK by now.

Later on I will have the chance to check the electric aspect and the fuel plumbing.

krayzc-RCU

My Feedback: (31)

how much gas was in the tank when you arrived back on the ground?

is this a 32 oz tank?

yellow, blue or black fuel tubing?

Albatross

My Feedback: (7)

It is a Dubro 32 oz tank. 3 lines: one for fueling, one for venting and other one going to the carb.
Was about 1/2 way by the time the engine died.

Yellow tubing.

Tired Old Man

My Feedback: (1)

If you are using a clunk on teo of the three lines it's possible that one fuel line and clunk may be laying over the other one, cutting off the supply to the lower line. Not that high a chance but one just the same.

Albatross

My Feedback: (7)

Battery and ignition + switch found OK.
Having the chance of fuel lines tangling each other while violent manouvers, inside the tank is an evil possibility, I will consider.
I may use 2 lines next time; to fuel will use a "T" connector.

By the other hand, I will try to re-build her; it will take time and a lot of patience. It is badly damaged, however still recoverable.

The exhaust of the engine almost came loose off. I wonder if I can try to braze the exhaust tube, any inputs here?. Of course ordering a new set is an option.