IBob

Only if it's a very tiny aperture: do the maths.

When it comes to multiple high-wing tanks with individual tank vents under the wing: At least one highly experienced member here has written of looking out in flight to see fuel streaming from one underwing vent. And once that starts to happen, you have a siphon which will just keep on going if the tanks are interconnected with no stop valves. I believe that event was caused by the underwing vent ends pointing in different directions, so introducing differential pressure. The (ferry) pilot landed and swapped in his own snorkel style fuel caps. I was told of a similar event where the aircraft was parked sideways on a slope with fairly full tanks: the downslope tank began to empty through the vent and levelling the aircraft did not stop it once the siphon was established. Popping the fuel cap, so breaking the siphon, fixed it on that occasion. And I had an event where, 20mins into a local flight, I looked at the levels on the inboard tanks I was using and was surprised to see one going down and the other going up. The reason turned out to be a fuel cap not sealing properly due to a light deformity in the tank lip (and my failure to pull it down tight). I'm an avid believer in the KISS principal, but I also think we need to be aware of these possibilities. FWIW, with twin unvalved tanks 180mm deep (for example), a differential pressure of just 0.065PSI between tanks will crossfeed all the fuel from one tank into the other. Which I guess is why Cessna tanks share a common vent, and why I'd like to be doing the same...........)

Skippy, Controlling the pressure cannot be done by reducing the aperture (unless it is made very tiny).

I reckon that collector tank is a great innovation, Old Koreelah. On the Savannah it's 5 to 6 litres, with a level switch in the top that lights an indicator 2.5minutes after valving off all tanks when in cruise (I recently measured it). Older Savs did not have a vent line on the collector, so occasionally gave false activations of the indicator due to air trapped in the tank. They now fit a breather back to the top of the LH tank. There is a button on the dash to test the indicator. The gotcha there is that's what it does: test the indicator, but not the switch in collector tank. So if intending to fly tanks to empty (which I rarely do here in NZ), I valve off all tanks prior to leaving and test both switch and indicator. It works for me, as we have a reasonably long taxi from hangar to strip, and both my prestart and preflight checks include identical runs through the fuel system, tanks to engine.

Spacesailor, it's quite a large pipe , bent forward to face into the airflow, but positioned behind where the strut meets the wing. My guess would be that if it was not sheltered behind the strut, it would result in excess pressure at speed, which would cause the fuel tanks to bug out and various other possible complications.

Skippydiesel, if you blow a jet of air across the end of a tube in a certain manner, it creates a low pressure there, drawing air out of the tube. So, while you are correct in thinking the underside of the wing is a (relatively) high pressure area, it is also possible to create a low pressure inlet under there, because the relative air is flowing, not static. For this reason, the likes of Cessna (for instance), who have spent a great deal more time and effort on these issues than you and I, have opted for a forward facing vent, albeit placed behind the strut to limit the pressure. If you have a system that works well in your aircraft, then that is what you have. But it certainly does not convince me that what you describe is all that is required, and everyone else has got it wrong.

Skippydiesel, I certainly don't claim to be any expert, I just know what I have observed with my own aircraft so far, and what I have learnt speaking with other pilots. I have L and R wing tanks which each have their own vent, out of the fuel cap and down through the wing (I've also got L and R outer tanks too, but let's not go there!) I got interested when I noticed the uneven feed from them. I've since learnt that many aircraft with such a configuration feed unevenly, and this is managed in some of them by flying for set periods on alternate tanks. I'm happy that I've been able to at last reduce the unevenness. I think if I was building again I would look at some system like Cessna, with a single vent then cross ported to the upper tanks. The other popular alternative seems to be the solid pipe set into the fuel cap, upwards then bent forward (and down a bit). I doubt there is any one system works well across all aircraft or all tank configurations. And it seems to me that what is vital is to have a working understanding of whatever fuel system you are flying.

Sure, Skippydiesel: My fuel valves for L and R tank are both on the fuselage wall behind the passenger, where I can see them. They then feed down into a receiver behind the passenger. So all lines go to the RH side of the fuselage then down. And initially more fuel was generally taken from the RH. I tried a number of things like adding ballast to ensure I was flying level, without results. I then straightened the LH fuel hoses where they come across the fuselage, by cable-tieing them to a length of al. angle, so removing all undulations. This resulted in a definite improvement. I then fooled with the angle cut on the underwing breathers. They are nylon air line, and do not come out of the wing perpendicular, but tend to lean this way and that. So angling them all the same does not present them all at the same angle to the air flow. One or two cuts on successive flights had the tanks feeding reasonably evenly. The next step would be to run solid tubes down through the wing, instead of the nylon air line. that way i could be confident the tube ends were presenting in a similar fashion to the air stream. I just need to come up with a simple way to ensure the tubes don't rotate on their axis.... It's an interesting problem, and I do think the Cessna setup (cross-porting the upper tanks) is the way to go, if at all possible........

I can promise you it's not 'probably ineffective', Skippydiesel: My tank breathers emerge under the wing, and I can vary the take from L vs R tank by cutting slightly different (forward facing) angles on them.

To add detail to that: The vent is forward facing, but tucked behind the strut to avoid overpressurising the system, which would risk structural damage. And the tanks are then cross-vented to give equal pressure in each side, with the aim of delivering equally from each tank and avoiding transfer of fuel between tanks.

Adjusting yer underpants is likely to cause a degree of levitation tooooo.........)

One very small step for mankind, one giant ego trip for Jeff Bezos. The world’s richest man ejaculated himself into space this week, in what was not quite the first suborbital tourist flight – Richard Branson beat him up there – but definitely the fastest. “Everybody who’s been up into space, they say that it changes them,” Bezos said earnestly, of a trip that lasted roughly the time it takes to hard boil an egg. If you say so, Jeff. https://www.theguardian.com/commentisfree/2021/jul/22/jeff-bezos-space-trip-midlife-crisis-amazon

Not quite: end of 2021, the notification says.......

Peter Gillespie (the Australian ICP agent) tells me that he is able to supply the 3 point door latch kits. Price is A$265 inc GST plus postage. He has them made up as required. His email is [email protected] This is the kit I installed, it is well made and works fine when properly set up.

A recent incident here in NZ involved an automotive oil thermostat on a 912, which reportedly failed and cut off oil flow to the engine. Fortunately, this happened on startup on the ground and the engine was promptly stopped. If I were considering an oil thermostat, I would be sourcing one that cannot fail in this fashion: as I recall, there is one advertised for the 912, and the manufacturer specifically states it cannot cut off the oil flow if it fails.

Mark: I've emailed Peter to ask if he or anyone is now making them. My thought was, if not, then maybe publish the design for the benefit of others?

Bent rod end: Mark, is anyone over there now supplying those door closer kits?

Okay. With my setup, I 'adjusted' the tang on the door handle by modifying the bend in it until the door there closed well, but not too tightly. Then the rods that close front and back have a chamfer on the end of them: I also bent the very tips of these to effectively give a greater chamfer at the tip, so that they pick up their locating holes without the need to pull the door in tightly. It was a matter of working round these closing points, but once I had them adjusted, they work fine. Finally, when operating the door handle, I don't pull in at the end of the handle. I place fingers behind the handle centre and pull in there (otherwise pulling on the handle just flexes the whole handle sideways). I explain this to passengers and we have no trouble closing the doors. I also have rubber seals, as Mark suggested (though I can't claim to get an airtight seal).

Why is it hard to close when seated???

Looks fantastic, Mark! What is the paint system?

I bought the system that attaches to the existing handle to (also) provide slide bolts (rods) front and rear. Works well enough after a bit of fiddling to set up. No difficulty working when seated. Was supplied by the Australian agent, Reg Brost, when I bought my kit from him. I believe he had them made up. However, the Oz dealership has now changed hands, and I don't know if the kit is now available. Wouldn't be hard to make.

I don't know. But I'll ask the locals what and why the next time I run into them.

Are you on level strips, Student Pilot.........or steep uphill ones?

Someone told me that the original design was intended for crop spraying (liquid, rather than solids), but that the wing did not lay down a good wet pattern, which is how it came to be sold on to the NZ manufacturer. I don't know if this is true. There was also the story of someone who picked up several of these aircraft for next to nothing: Some of these pilots used to travel the world with the seasons, perhaps they still do...wheat crops in the UK, then down to the cotton in the Nile delta and so on. The story went that one of the Arab countries had bought several Fletchers, a local pilot had killed himself in one, and the remaining local pilots then refused to fly them. So they were parked near the end of a runway, and about to be bulldozed during runway widening/extensions when a visiting pilot offered to take them away instead.............

I believe the turbine also allows them to make a faster approach, then put the prop into beta on touchdown if required: that's certainly how they put down at the airfield at the end of the day. Then many strips are sloping, so the speed washes off quickly once on the ground, and it's not unusual to be applying power again to get the aircraft back up to the loader.