It Flies After 9 years

[MarkD 53]

Saturday, 13 June I flew N577MD after it sat in a guys garage for 9 years.  I was only one time around the pattern because I need to re-jet the carbs to keep EGT below 1200 and re-pitch the prop to get a bit more RPM on climb out but it was uneventful.   The flap handle was too loose and the flaps kept creeping toward negative giving me a bit of nose up and I had to keep down pressure on the stick, but it was manageable. 

 

It is amazing that an airplane can sit for 9 years unused and the engine not run, (or stored properly for that matter) and then be made flyable with minimal effort.  I  will be cautious with the engine for a few hours just to make sure that it does not have any defect not yet realized.  I'll get more time on after the jets I have ordered get in and I have them installed.  I have a huge prop, 72", and I took out a whole degree of pitch to try to get the RPM to come up into the power range.

 

I'm really looking forward to getting some dirt on the tires.

 

MarkD

[KFfan 151]

Congratulations.   Nice to hear...

 

(probably gigantic cuhonies?)

[Av8r_Sed 82]

Good to hear you've saved another of our birds from oblivion.  Good Job!

 

Keep the Hacman system in mind if managing the EGT's ends up giving you the blues.  It's great just dialing in the EGT you want and not worrying about rejetting for changing conditions.

[dynomike 91]

good job man ,another one of these great planes brought back.

[dav8or 20]

Also consider putting together your own leaning system like the Hacman. The only hard part to find is the needle valve. The other pieces can be ordered from McMaster Carr pretty cheap. I put mine together using diagrams from Chris B. and it works great. I run fairly rich jets and lean the engine to conditions with the needle valve control mounted in my panel.

 

Dan

[MarkD 53]

Dan, Do you have schematics of the HAC system? I've been looking online but have not found anything comprehensive yet. You mentioned drawings from Chris B. but my search of the forum did not show anything (or at least I was unable to find it). The jetting thing is getting tedious and the more I read the more I think I want to try the manual HAC thing.

MarkD

[Dusty 126]

Hacman is one of my "wouldn't be without" items

Probably be worth starting a separate thread for this one?

[EDMO 1078]

Was the Hacman the control designed by my friend, the late Mike Jacober, who owned Arctic Sparrow ultralights in Birchwood, Alaska, and set altitude records - Or, was his a different control?

EdMo

[1avidflyer 1983]

I believe Mike's system actually raised and lowered the needles to change mid range jetting.  Jim Chuk

[ChrisBolkan 130]

Here are some files I posted to the Yahoo group to build a mixture control. There are a bunch of photos related to the carb mod document that I will try to locate and post later.

 

These files are for reference only. I made these notes as I went along designing my own system and the different sketches show things differently. For instance the sketch that discusses my reasoning is not the same as how I ended up building it. My final setup didn't end up exactly like any of the sketches. The concept is what is important.

 

You should not undertake this type of project withot a pretty clear understanding of what you are trying to do and end up with. It is better to understand the concept of how it works and do your own variation that makes sense to you than just copy and hope for the best. This system has the capability to burn up an engine if the reference restriction isn't fine tuned to the valve and the specific installation or it isn't operated properly.....like leaving the valve at lean following a long decent to low elevation and forgetting to enrich it again before takeoff.

 

One really nice thing is my engine idled and taxiied much nicer leaned out, but I had to remember to enrich for takeoff.

 

I used this system for years and it really worked well for me.

 

One other thing. I am not flying behind a two stroke now, and it has been years since I did this project. I am happy to help out a bit where I can fill in missing stuff, but I have probably forgotton a lot. Also I do not want to be resented or held responsible in anyone's mind if someone builds this and nukes their engine as a result. 

 

That said it is a very fun project that really works when set up right and costs virtually nothing to build.

 

Chris

Chris Diagram.pdf

Manual mixture.PDF

Carb mod.pdf

[MarkD 53]

Thanks Chris,  I had already started design drawings for a system,  interesting how we came up with very similar arrangements.  Obviously your drawings were quite a bit more refined as to sizes of tubing and orifice placement due to having already built the system and operated it. 

 

I have a mill, lathe and other capabilities in my shop so the carb mods will be no problem.  I have also reviewed the "Green Sky" web site information.  One difference is the Hirth has 38mm Bing 54 carbs installed and the jet sizes are different from ROTAX specifications, but the basic carb casting is the same and the concept is still valid.  My Carbs are not drilled for the venturi tap but that is easy machine work. 

 

I'm glad you kept the information and are willing to share it.

 

Where did you source the needle valve that worked for your application?  How fine does the control need to be?   I think Grainger has a 10 turn valve but I'm not sure how it is mounted.  Maybe I could make one if I can't find an appropriate one.

 

MarkD

[KFfan 151]

Thanks for sharing Chris.

I have been thinking about this modification/feature for my 582. Although my operating environment will not vary as radically as many here, my thinking has been about optimal performance from the power plant under even seasonal density altitude variations. In looking at the tables it seems to me the jetting variations seem to be pretty minimal. In your, and others, opinion(s) am I in "left field"?

Lou

[ChrisBolkan 130]

I used a 3 or 4 turn needle valve by SMC. I "ported" the valve by drilling out the threaded fittings and soldering little tubes in place so the valve had the largest "open" cross section I could obtain so it had minimum restriction when open. I think this thing works as much off pulses as pressure, so I kept the lines as short as possible to keep pulse phase shift minimized just in case that made a difference.  In hindsight I think a 1/4 turn ball valve would have been better. Problem with needle valves is the precision of the valve means a very restrictive valve overall. 10 turns is a super overkill. What if you take off leaned out? t takes time to turn those little valves 10 turns! One turn would be perfect and would have provided all the "accuracy" I ever needed but I could not find a 1 turn valve. I really think A 1/4 ball valve would work super well and still provide adequate fine adjustment. The nice thing about ball valves is that there is no restriction when they are open.

 

Also You really want to size the restriction so opening the valve all the way only makes 100 or maybe 200 degrees max difference in EGT. Too much adjustment range can lean way too much even killing the engine as I found out developing it. I found one of those little plastic tube couplers worked perfect as a restriction. It doesn't take much. I think it is all visible in the photos i took of the install.

 

I just checked on the avid yahoo group site and all my pictures are there. There are two photo albums. One is "Carb mods" these pictures go along with the carb drilling instructions above. The other photo album is "mixture control. Those pictures are of my actual finished installation that I flew for years.

[ChrisBolkan 130]

It depended on the year but I usually changed main jets seasonally with my system. I probably didn't need to. I could have used a super small restriction to get more range, but I also had a couple near incidents with the system when it had a ton of adjustment range. I ended up using a simple plastic tubing coupler as the restriction and with the valve I used it gave somewhere around 100 - 150 degree total change in EGT. That limited range allowed me to keep EGT's fairly optimal through a wide range of conditions, but didn't go so far as to create a catastrophic condition if I left the valve in the wrong position which I did sometimes.

[MarkD 53]

Thanks again Chris,  Your advise is well taken.  The local hardware suppler at the Port Townsend Boat Yard has tons of different valves and hardware. Armed with knowledge I'm sure I can find the needed materials.  I may mount the valve on the firewall and just make a stem extension to operate the valve from the panel.  That way I woould not have to run any more tubes through the firewall.

 

I flew for an hour tonight,  temps were in spec for the conditions, 60F OAT, baro 3006.  By the weekend we will be in the 40 degrees at morning and 80s in the afternoon routine again.  That would mean at least two adjustments to jets and needle positions.

 

I have to make the HAC to get away from that.

 

By the way, I'm enjoying this FORUM, unlike some others I have attempted to participate in, in the past, this is a neat place.

 

MarkD

[Dusty 126]

The restricter Is a very critical part and requires a bit of experimentation.

200 f is ample adjustment, any more could end in tears with a momentry laps in concentration on decent

Mine operates full range at 1/2 turn on a needle valve,

[ChrisBolkan 130]

In my setup I kept the stock needle, needle jet and idle jet. I ended up bumping the main jet all the way up to 200. At first it didn't make sense that I would have to go to a jet much larger than sea level. I eventually reasoned that with the valve turned to full rich (off) that acoustic pulses present in the aircleaner where I had the reference port were producing a pressure lowering effect in the floatbowls.

 

I had the choice of placing the reference port inside or outside the aircleaner. I reasond that inside was best because as the aircleaner got dirty, Iit would not change the mixture b/c the carb inlet and ref port shared the same relative air pressure.

[Bandit 286]

Hmm, seems like the Artic Sparrow Mixture control would be much simpler. I have used mine for years with no problems.

[Av8r_Sed 82]

The Hacman style is very effective and simple once it's installed.  I haven't had any issues with mine.  

 

Is the Artic Sparrow system still available?

[Bandit 286]

I don't think so.