Saturday, November 25, 2017

4th Annual Inspection

The RV has 227.0 hours on it and a few things started to indicate that some work had to be done. The engine had started to run a bit rougher than I remembered it from the first year. The vibrations were noticeable at all RPMs and even at idle.
The carburetors are supposed to get overhauled at 200 hours which felt overdone to me but I decided to do it as I could not explain the roughness other than by being carb-induced (the balance was fine last year).
Also, my oil temperature indication was going haywire since a few hours ago. In the middle of a cross country the indicator would erratically drop below 120degF which would make B*tching Betty call out "Engine Speed!" 3 times in a row for every drop below 120degF. As it would frequently go back to a more believable reading and then drop again one can imagine how annoying and distracting this can be. Thank Van's for the "Isolate" switch on the intercom which shuts off dear Betty and lets you focus on flying the aircraft.
I also wanted to use the occasion to finally stop the oil drain bolt from leaking by installing a quick drain valve using Loctite 243 to seal it.

And so another Annual begins!

The spark plugs (these were the Iridium version of the NGK plugs) had reached a hundred hours and they definitely didn't feel that great anymore during the ignition check, so I decided to replace them. As I still have a stack of standard NGKs I decided to put the regular type in to reduce my inventory.
The plugs that came out showed the usual rich pattern with the exception of the top aft plugs on both sides that showed a healthy light brown color. It escapes me how this could be possible but that's what I found.

I ordered more of the Iridium plugs as they really make a difference in the Rotax when they are new but I'll first use up the old stock that I have accumulated. 

The visual inspection of the engine looked good. A very slow leak on the bottom of the oil canister as I have grown used to but creating enough of an annoyance to make it onto the to-fix list. 

The temperatures all looked within tolerances with the voltage regulator still being a bit on the high side. Something I am planning to address next time around by adding a fiberglass laminated scoop in the tunnel to increase the air flow for cooling. 

VR abit higher than I'd like

No indication on either ignition module

The oil change didn't reveal anything abnormal. And after 4 years of flying I also removed the magnetic plug for the first time only to find a very small amount of shavings on it. Just as you'd expect from a Rotax.
I installed the oil quick drain valve with Loctite 243 as planned and safety wired it to ensure it could not open in flight.

So far no leaks, so I hope the inside of the cowling will stay clean from now on. 

Off came the carbs for he first time/. The air filters looked really good by the way. No cracks, no chafing, no dirt. I think these green ones will be staying with this engine. 

A little bit of build up on the intake side

I had not taken these off in the first years as nothing had pointed at any type of issue and I am a strong believer in leaving a system alone if it isn't broken but I was very curious what I would find inside this time.

Opening the bowl revealed that on theleft side I had a small piece of debris in the carb and I have no idea how it could have gotten through the system that far.

Nothing else was found that didn't belong there. The floats were removed and put on a scale and - WOW - what surprise! As I said, nothing had indicated an issue but when I put the floats on the scale it showed that one had drowned.

Drowned float

still good

I assume the carb never showed a problem because one floating float is enough to keep the bowl from overflowing. I never had an issue with fuel smell or fuel residue in drip pans below the carbs.

old parts coming out

Needle shows signs of wear

Viton valve and arm were replaced for good measure although the valve did not show signs of wear yet. The needle though did and so I replaced needle and jet hoping that this was the reason for my rough running engine.

The interior was cleaned, seals lubricated and put back together.

The way I did the overhaul was one side ata time so I would have an untouched carb to look at if I was in doubt how something would go back together. So the next day I installed the overhauled one and took off the remaining carb of the engine and did it again.
The right side carb also had one slightly sunk float!

Too heavy

Still within tolerance

No other findings on the right side carb, and doing the overhaul for the second time was a lot faster than the first time around. 

The engine test run revelaed that the roughness was gone. The engine was running very smooth, almost purring, with no indication of imbalance. The only thing that did change was the idle setting. You have to know that the way I removed the carbs from the engine was by removing all throttle and choke linkages from the carb so the balance settings would not get affected. So I was quite surprised to see the engine idling at 2200 RPM now, given that the throttle cable was in the very same position. Apparently the engine was running leaner now at idle which increased the RPMs. 
I opened the idle cable stops and readjusted the setting after the engine had heated up and set the idle to 1400 RPM which feels like the engine is just about to quit on its own. On final with forward movement the prop will turn easier and the engine will be ok with that low idle but it will allow me to slow down as much as possible.

The Skyview battery test next and it passed ok but it looked like it was just at the edge of failing. So I'll be prepared next year to swap it out with Dynon again. Probably do the test early on so I don't have to wait for shipping when I'm done with the mechanical part of the annual inspection.

Pretty low voltage close to end

The oil temp sensor was an interesting chapter. I tried to find a replacement from VDO to have one on hand in case it turns out that the temperature fluctuations I saw were caused by the sensor itself and not just by a bad connection. Don't get me wrong, the behavior strongly suggested a connection issue but I want to be ready in the case it did turn out to be the sensor anyway.
As I have documented on the forum, the cost of a Rotax temperature sensor for oil or CHT (p/n 965-531) is somewhere between $195 to $275 (as of 2017) which is completely ridiculous. VDO builds these for them and they usually run around $18-$25 when bought in an auto parts store. So to protect their business Rotax decided to use a thread on the sensor that was not commonly sold by VDO and so finding the correct type was a bit of a hassle. What you would be looking for from VDO is not one of their regular part numbers but a more complex internal ID system:: 323-801-010-001D, a.k.a. 801/10/1,  which should translate to 300 degF (150degC) NTC with a M10 x 1.5 threading and a flathead connector that allows a female spade connector to slide over it.  The regular VDO sensor in M10 (VDO #323-423) comes with a 1.0 pitch thread and will not fit on the Rotax.

Now back to my case of fluctuation. I removed the spade connector and found a very slight movement when tucking on the wire. So I decided to solder the wire in the crimp and add silicone on the connection between wire sleeve and crimp to help dampen the movement caused by vibrations.
The readings were a lot more solid on the ground where I had previously seen a ibt of a nervous 5 degree fluctuation up and down. Now it just sits there rock solid, so I have good hopes that this did indeed fix the problem and I won't be needing to replace the sensor.

This concluded the burning issue list items. A while back I had decided to finally add the carpet interior to my 12 as the interior noise on long flights was somewhat tiring and I hoped that the carpet could help with that - next to looking really nice of course.

Needed some custom trimming as I still have a sight gauge and my Moeller is not in the official spot as I added before Van's adapted this to their kit

It will be nice for the passenger to have something to rest their feet on

I did not install the carpet over the forward tunnel as this part gets very hot in the summer on take-off and I am worried that carpet would increase the interior heat to a damaging point.
The other part I did not install yet is the upper triangular piece that covers the area around the vents. I have a headset hook installed there that I 3D printed and I need to see how I can keep that with the carpet.
Next time at the hangar I will perform a dynamic propeller balance and hopefully notice that the interior is really quiet now.

I'll post a separate article about the prop balancing as I have a feeling this will be a longer story.

Also, after the balancing I am going to install a new battery as preventative maintenance. The 4 year old one got a bit tired in the winter before and I was getting worried about not being able to start the engine. Voltage dropped to 9V when cranking longer than usual and any small engine hiccup that would have delayed engine start could have left me with a dead battery on the ramp. IThis winter is really mild and so far no issue but I thought after stressing the old battery with a succession of engine starts for the balancing, I might just retire it before I get stranded somewhere on a cold morning.

I also forgot to take a full cockpit picture once all the carpet and seats were back in which I shall add after the next weekend.

On to another 11 months of fun flying!

Update on the Fuel Pump

After about 25 hours on the replacement pump all the pressure readings are back to normal. The first 5 hours or so I was watching a break-in period though. The pressure would oscillate at about half a Hertz. Rise about half a pound, fall about half a pound and so on. It all worked itself out over the first few hours and the overall pressure also came back up to known levels.
So if you ever have to do this and the new pump appears to be behaving differently, give it some time and stay in gliding range of a landing opportunity during evaluation.

I finally got around to open the old pump and I was a bit disappointed.

This is the inside of the head

I actuated the diaphragm but regardless how close I looked I could not find any tear in the diaphragm material. Still, I know the pressure dropped to zero when I turned the electric fuel pump off, so there has to be a leak I just can't see it.

Monday, July 31, 2017

Fuel Pump Failure

End of June I wanted to depart on a breakfast flight to Benson with my wife, when ~3 minutes after take-off the cockpit quickly filled with a strong stench of gasoline. It wouldn't pass for a minute or two and I knew what that meant.
I turned around and climbed to 10,000 feet. Once over the field I turned off the electric fuel pump and watched the fuel pressure drop quickly to 0.2 PSI when the engine started running rough. I turned the electric pump back on and landed the plane, canceling our breakfast plans. Apparently the diaphragm on the engine-driven fuel pump had ruptured and leaked gas out the weep drain and overboard. At just 207 hours, that's rather frustrating.

out comes the old one....

It didn't take too much time replacing the pump, besides the inaccessibility of course. With crow's feet it's pretty impossible to put any controlled torque on the bolts and that includes the fuel distributor block.

... and in with the new one.
I did an extensive engine ground run at full throttle with only the engine-driven pump running to see if it was working alright. Then I headed for a test flight, steep take-off staying over the field and climbing to 10,000 ft.. Stayed there for 20 minutes before moving away, always staying in gliding range.
Without the electric pump running, the fuel pressure was oscillating between 2.6 and 3.4 PSI. I never saw that with my previous pump. It was a very repetitive oscillation pattern, almost rhythm-like.
Even on a cross country flight a week later I could still see this oscillation pattern but it never dropped below 2.6 PSI.
After coming back from Oshkosh (flying commercial) I had another flight where the mechanical pump produced rock solid 3.9 PSI. No oscillation and no jumps. Apparently, a new fuel pump does need some break-in period.

Let's see how long this one will last. Fingers crossed!

I'll disassemble the old pump to verify the failure mode of a ruptured diaphragm and I will update this post when I have the pictures.

Monday, January 9, 2017

Operating Limitations Overly Limiting

One of the things that most builders forget quickly after the exhilarating experience of turning a heap of metal into an airplane - also known as "receiving an Airworthiness Certificate - is that the whole world of experimental flying our kit planes is built upon something called Operating Limitations.
Without the OpLims, there is no experimental flying.

You will receive your Operating Limitations on the day you get your Special Airworthiness Certificate, better known as Pink Slip, and it explains in detail what you can do with the airplane in the initial trial phase, aka Phase I and what you can do once Phase I has been completed - which is referred to as Phase II.

You airplane will likely spent most of its flying life in Phase II, so those limitations are the most important ones for any owner of an experimental airplane.
When I received mine, I studied them and I found one odd set of limitations regarding Phase II and doing anything but flying in VFR conditions during the day.
I have to admit that because of the excitement of accomplishing a successful airworthiness inspection as well as the fact that I was going to fly the plane as a Sport Pilot this tiny weirdness did not bother me too much.
What it was you ask?

Well, here are the two limitations quoted from the OpLims:

10) This aircraft is to be operated under VFR day only

11) After completion of phase I flight testing, unless appropriately equipped for night and/or instrument flight in accordance with 14 CFR part 91.205, this aircraft is to be operated VFR day only.

The way the limitations were applied to Phase I and II respectively was by adding the numbers of the limitations that applied to a paragraph titled Phase I and II respectively.

Mine looked like this:

Phase I Limitations: 1, 2, 3, 4, ..... , 10, 12, ......

Phase II Limitations: 1, 2, 3, 4, ..... , 10, 11, 12, ......


Of course, you wouldn't want to fly your plane during the trial phase in adverse meteorological conditions like IMC or at night. So having 10) in phase I is perfectly fine. As 11) wouldn't apply, it is not listed under Phase I.
However, Phase II has apparently 2 limitations that deal with flying at night.
10) prohibits it altogether, and 11) would allow it if the plane was properly equipped (mine is).
10) is clearly more restrictive and I would think the FAA would use the more restrictive one as we are dealing with LIMITATIONS which are restrictive by nature.

Why do I even care? Didn't I say I was flying as a Sport Pilot anyway and Sport Pilots are prohibited from anything other than flying VFR day.

Yes, that was the case. However, I have started to work on my Private Pilot License and I wanted to use my RV-12 for all the required lessons I have to take with a CFI. That would include 3 hours of flying VFR Night and my OpLims clearly prohibit that.

I searched VAF and found that at least one other builder in Arizona was hit with the same mistaken limitation and that his DAR had told him that the FAA would not issue new OpLims but that this is clearly a mistake and only 11) would apply.
Hm, sounds like one would have to trust the federal government. That's quite a stretch, isn't it. And on top of that your CFI would have to be satisfied with this "explanation" too. Pretty unlikely as their job depends on it.

I contacted my DAR who had made my RV-12 an airplane about 3 years ago and explained the situation. He agreed that this set of limitations made no sense and contacted his person at the FAA who also agreed(!). What were the chances? Honestly!
My DAR was given authorization to issue amended  OpLims in accordance with the latest updated regulations and I should have them in my hands before the weekend. The new limitations are fully spelled out, much more narrative than the old ones and more importantly the issue of no night flying in Phase II has been eliminated.

What is the morale of this little story? Check your OpLims when you get them and get them straightened out if you find anything that strikes you as odd. It's likely easier when they just got issued and the copies haven't made it to the FAA yet.