IBob

Hi MPeter14, thank you for your clear description. I have a 4 tank Savannah S, but rarely use the outer tanks, so normally fly with the two inner tanks valved on. I have the tank vents piped to the underside of the wing, cut off at 45degrees facing forward. Like you, I have always had uneven feed from these two tanks, though I have not had a low fuel light as a result. I have tried various things since I noticed this: I saw a Savannah with forward facing fuel vents under the wings, like little pitots, thought this looked very neat and converted my own vents to this setup. The result was massive cross-feeding of fuel from one tank to the other...the LH tank was visibly going down, while the RH level went up, I promptly returned and landed. On landing, I found fuel across the RH upper wing. I think the pressure had been enough to cause that fuel cap to bleed air and fuel. It also occurred to me that even modest pressure in the tanks would cause them to swell or bug out, with pressure on the tanks supports and upper wing skin. So I converted back to the standard underwing setup, with the pipe cut at 45 deg to forward. Since then I have done what I can to remove any undulations in the fuel lines (my lines all go to valves on the RH side of the baggage area), especially the lines coming from the LH tanks, which I have tied to an aluminium angle 'splint' to hold them straight where they pass across the upper fuselage. My thought is that any undulations may hold air, so requiring a small amount of pressure to drive the fuel up and over (this is a known phenomenon with gravity feed of water through long undulating hoses: the necessary head of water to cause it to flow is the sum of the undulations). I have also experimented with adjusting the 45degree cut on the vent lines to more or less than 45deg. My fuel feed is now improved, but still uneven, and I have learned that most aircraft with multiple tanks have uneven feed. Which is why many of them are flown with timed use of alternate tanks. In summary, I think it is important to minimise undulations in the fuel lines: in a perfect world they would track always downwards from the tank, but this is not possible in the wing. And I think the tank vents should provide only a very small increase in head pressure: any larger pressure may prevent a tank emptying as happened to you. By my calculations, your 4gals of fuel would be approximately 65mm in the tank. This would require an excess pressure of just .07PSI from the other tank to prevent flow.

Marty, that must feel good! Round here, every single Sav build has involved building a complete new workshop, extending a workshop to clear sufficient space, or erecting a hangar. Long time ago an author called Gail Sheehy wrote a book called Passages, where she looked at people who had made major transitions in their lives. The passage is the transition, and what I recall from the book was that many said had they known how long the passage would take, and what was involved, they may not have had the courage to begin. Building your own aircraft is, I guess, less dramatic than that......but it seems to me there are parallels.......)

Onetrack, I can tell you there are still RAF pilots who think that's fun: I have an aged cousin in the UK, still rides a little, and she put in a complaint a couple of years back having been 'beaten up' by a couple of fighters.

mpeter14 it would be really interesting to know the details of your aircraft where this happened. Do you have the standard 2 wing tanks? What sort of vents do you have on the fuel tanks??

Here ya go: 2.5 Applicability 2.5.1 Models This manual contains JABIRU recommended procedures and instructions for ground handling, servicing and maintaining the following Jabiru propeller models: 4A482U0D - 2200 Scimitar Propeller Assy – Ground Adjustable, 2 Blade Composite. 4A484E0D - 3300 Scimitar Propeller Assy – Ground Adjustable, 2 Blade Composite. https://jabiru.net.au/wp-content/uploads/2018/05/JPM0001-4.pdf

Blueadventures, re the Savannah, that would depend on what model (and, of course, loading): The hugely experienced allround pilot who test flew my S noted in his report: "Abrupt throttle closure in combination with low and reducing airspeed during landing flare...can see a loss of elevator control and potential for the nose wheel to touch down firmly. Recommend trickling off power...alternatively, maintain 35kts into the landing flare." I fly often on my own, with perhaps 40litres in the tanks, no baggage and my adjustable seat 1 notch back from the front position. And (too) many of my landings have seen the nose wheel touch down firmly. I added VGs to the elevator underside, which improved elevator authority some, but there remains a distinct difference between the Sav VG, where the nose comes off readily and may be held there at sub-takoff speeds, and the S where the nose does not come off so readily. Then recently I made up a 10kg sandbag and placed it in the centre of the baggage area. And suddenly I have an aircraft that no longer drops the nose wheel on. I should add that my S is a standard build and all the calcs show my solo flight configuration as well within the forward limit according to the POH.

One things for sure, Mark: with this degree of unsolicited international assistance and oversight.......she's gonna be a verrrry cool plane........)

Mark, the coolant goes from the pump into the underside of the heads, out of the upper heads to the 'spider' with filler cap etc on top of the engine, from there to the radiator LH, from there to the pump inlet. Fig 75-1 in the Heavy Maintenance Manual. The coolant temp sensors are on the top of the heads, which is the hot coolant leaving the head/s.

It's really the coolant temp coming off the head/s you want. Rotax must have had good reasons to move to that, I guess it gives a clearer and/or steadier result. I'm just not sure where you could readily insert a probe, and I do think it needs to be inserted: I have commissioned a fair few industrial hot water and refrigeration systems, at one stage we tried a probe that could be strapped or bonded to the outside of the pipework, but we found them at best not very accurate, and wildly inaccurate unless the probe and all the surrounding pipe was heavily lagged.

PS: I should have said "The Sav has monitoring on front LH and rear RH cylinders and the front always appears to run cooler" Working on industrial hot water systems, we found we needed to be careful positioning temperature probes in pipework etc: since part of the sensor is outside the pipe, it can conduct heat away from the sensing element inside the pipe, resulting in incorrect low temperature readings. This was especially the case with smaller pipes and shorter temperature probes, and we adopted the policy of mounting our probes into a 90deg bend in the pipework, allowing us to insert a longer probe along the pipework, rather than a shorter probe across it. Since the coolant temp probes on the 912 are short, with no thermal insulation on the outside, it is quite possible that the front LH probe reads cooler due to the cold air playing on the external part of the probe.

True enough: your ambient temps are obviously higher than ours. And I understand Mark is tweaking his engine some, and has also remodelled the cowling. So head/coolant temps will be something to keep an eye on throughout the test flights. I have steam gauges marked up with red lines. The Sav has monitoring on front LH and rear RH cylinders and the front has always run cooler, as you might expect. For coolant temp you don't want to get to 120'C as this is boiling point.

Older 912 cylinder heads take a fitting to monitor head temperature. As of about 2013 the design was changed so the fitting now monitors coolant temp, not head temp. Max head temp was 135'C. Max coolant temp is 120'C. See MPD 2017-001 at https://publicapps.caa.co.uk/docs/33/2017-001.pdf FWIW my 912ULS with the annular pipes has coolant temp monitoring, which generally sits at 90-100'C and I've never seen it go over that.

With any pipe type/diameter there is a fluid velocity point where laminar flow becomes turbulent flow, and resultant flow actually deteriorates. Lots of irrigation 'specialists' have lost the plot on this over the years: it doesn't matter how big a pump you fit, you're not going to get any more fluid through it. There are readily available online pipe flow calculators, including for this annular pipe (though I have no feel for how accurate they may be for the smaller IDs eg. 9 or 10mm as used for fuel). As you would expect in what is a corrugated pipe, the laminar to turbulent cutoff is especially sharp.

Mark, my pipes were further secured against vibration after those pics were taken. I also made little aluminium heat shields where the rubber is close to the exhaust, spaced from the rubber but held in place by the hose clips, you can just see the LH edge of one here. I've read a lot of critical opinion on the metal pipes, but much of it seems mainly to be resistance to something 'new'. I figured if they were failing, we would have heard about it.........the proof of the pudding and all that.

My S kit was dated Dec 2014, Mark, ICP supplied steel pipe for fuel, oil and coolant. And you're right, it makes for a wonderfully compact installation, as I recall I formed the big coolant pipes in place.

That's terrifying!........deep respect for the test pilot/s........

Oh dear: Service Ceiling: 10,000 ft (3,000 m) (estimated), 3 ft (0.91 m) (actual)

Some wit set this up outside Gatwick a few weeks back: https://www.bbc.com/news/uk-england-beds-bucks-herts-61541224

What you are needing is an Air Speed Indicator, and GPS will absolutely not give you that: the last thing you need to be looking at to avoid stall is (GPS) ground speed........

It turns out both the above aviation accounts are true: Sabrina soloed in the Cessna she was given at age 14 in Canada. She built, with assistance, Zenith N5886Q, which she flew at 16.

I hate to be picky, but I also hate the casual misinformation, and don't understand the need for exaggeration in this case. Or maybe the problem is the growing inability to read past any first sentence? Sabrina started building N5886Q in March of 2006 at age 12 and she completed it by October of 2007. It was then disassembled, painted, and transported to KARR. It was certified as airworthy E-LSA on January 11, 2008 and flew its maiden flight four days later, on January 15th. It was kept in Phase I flight testing for Sabrina's first U.S. solo which she conducted in it on August 24th of 2009 at age 16. Or maybe this: According to Pasterski’s account on her web site, her grandfather gifted her a Cessna 150 airplane for her 10th birthday. Over the next few years, Pasterski got help from a mechanic and others in rebuilding the plane’s engine and constructing the frame for a new aircraft. She told the Chicago Tribune in a 2015 interview that she first went up in a plane at age 9: The first time was a discovery flight (which typically includes both instruction and a quick time in the air with a flight instructor). It was basically along the shoreline. That was really gorgeous. It’s a nice feeling. It gives you a different perspective; everything’s so much smaller. Then, two days before her 14th birthday, Pasterski flew the plane by herself in Canada. She created a video montage to document her work on the project. Stephen Hawking never followed her on Twitter: neither of them have or had Twitter accounts. And there is no record of anyone at Harvard calling her the next Einstein. ------------------------------------------------------------------------------------- However, someone of extraordinary abilities, no question about that.

Nah......follow your own taste, Franco! I'll just turn the sound down and enjoy the visuals...thank you for posting them......)

Nice camera angle, enjoyed the flight. Not my taste in backing music, but that's subjective..........)

Big job, Mark! And I never did come up with anything to (easily) fill in all the little mat holes on my kit supplied f/glass bits: sourced various products, but every sand/spray iteration showed more holes. If only they'd used a gel coat....what have you used there?

😬