IBob

Hi Ian, yes all of that makes good sense. And while I had good hearing for most of my younger life (as a young 'un in the UK I could tell you when there were bats around at night) I have always struggled to make out what people are saying in noisy pub type environments. I don't know why, and I find it very tiring trying to maintain contact in such environments. Since taking up flying much later in life, and while my hearing for normal conversation remains fine, I have found I need all the help I can get in the cockpit. I am very happy with my Lightspeed Zulus, and even without the ANR switched on, they really do a great job of reducing the ambient noise.

I grew up near High Wycombe, in Buckinghamshire. Ansons were a common sight overhead in the '50s, I believe they operated out of Booker airfield and were used for navigation training.

I think APenNameAndThat's original proposition is quite cunning, and certainly worth considering: 1. 'Turn down' hearing by inserting earplugs (hopefully without sacrificing clarity). 2. Compensate by turning up headset volume. 3. Ratio of headset sound (radio and comms talk) to external sound is now improved.

Skippy, the Sav (amongst other aircraft) has a 6L 'receiver' tank behind the passenger seat with a drain cock underneath (this being the low point in the system) and a float switch in the top which activates an indicator on the panel unless it is full. This arrangement gives approx 20mins of warning of fuel exhaustion. It also compensates for unporting of tanks, as may happen in long descents or momentary unbalanced flying. And some folk run their fuel return back to that tank, so avoiding the problem of overfilling a wing tank with returned fuel. All in all, I see the receiver tank as a very worthwhile innovation. Might it be possible to fit something similar, albeit smaller, in the Sonex?

PS here's a further minor complication for you: the air behaviour under your cowl quite probably alters not only with speed, but also with angle of attack. For instance I found the Naca scoop on my cowl top doesn't work well at high angles of attack, so I was drawing air from under the cowl instead of outside air. I was able to correct that by greatly reducing the gap between Naca scoop and airbox inlet. How much such things may affect your fuel pressure sensor mounted in the engine bay.......if at all.......we'll never know, without something else to check it against. But I'm not surprised to hear that some pilots get odd results, if that's where they are putting them.

Skippy, I confess I have not spent time studying my fuel pressure in flight. I do know that sometimes it is at or just above 2PSI in a climb, other times (and more usually) it is at or above 4PSI. And I have seen it shift quite quickly from one to the other, but I don't know why it should do that. I shall watch it more carefully when next out, and see if I can add to that. I am on steam gauge. I don't know why your sensor would be slow to catch up with air pressure. Having said that, these sensors (once you get away from the VDO stuff) are standard industrial equipment, and I suppose it is possible they could have a very tiny or filtered internal atmospheric aperture....since they are normally deployed in static applications, not required to respond to rapid or large atmospheric changes, and the manufacturers quite probably have internal filtering etc to protect the works from the ingress of moisture and dirt. It's certainly interesting. If problems persist, one option would be to borrow a steam gauge and plumb it in, You would then be able to clearly establish if you have a fuel pressure problem, or a fuel pressure sensing problem.

Nev, this is bizzare. As a person living on a pair of islands with about 25minutes water between, I take a real and ongoing interest in this stuff. And I fly a Savannah , so I am doubly interested in how that might behave in a ditching. What I am not so much interested in is Walruses or airliners in Tanzania. I certainly made no claim that my own position was 'representative'. As for facts, I'm not sure what your problem is with the statistics that Bertorelli dug up, but I personally am far happier going with those than some notion of 'physics. And that's it from me on this.

Nev, nobody here at any point has suggested that ditching is a piece of cake. However, stirring a big pot full of stale theories, adding a few airliners and dishing up the results in a doom-laden fashion does nothing to help- anyone. Did you miss the recently posted Savannah accidental ditching? High wing, fixed undercarriage, didn't flip. Could have but didn't. However the doors (which cannot be opened safely inflight) were held shut by water pressure until the fuselage filled. They then opened. I found that description of actual events useful.

I see that, Bluedaventures and it does need investigating. But we need more info: Is this a bottle just for the fuel pump vent, or is it also for oil reservoir vent. If so, which is the oil coming from? Also, is oil still coming? I was taught to troubleshoot by formulating a theory, based on my understanding of the machine, that matched the symptoms...then formulating tests to test the theory. And doing all that before actually picking up any tools. In Skippy's case here, I am very interested to know more precisely when the problem appears and also to what degree. Does it appear immediately on takeoff, or does it increase with altitude? I have also learnt to simplify wherever possible: remove extraneous stuff rather than adding to it, in order to focus on one specific thing.

To explain the gauge/sender/transducer thing further: All of these devices have some sort of diaphragm (or similar setup) normally open to atmosphere on one side and connected to fuel/oil/whatever on the other. They work by measuring how much the diaphragm is flexed or deflected. So, on the ground, engine off, there is equal atmospheric pressure on either side of the diaphragm, pressure reading zero. Start the engine and there is atmospheric pressure on one side and atmospheric pressure plus fuel pump pressure on the other side. The atmospheric pressures cancel out, so you get fuel pressure. Climb to altitude and the atmospheric pressure is reduced, but equally on both sides, so it still cancels out. But if the atmosphere side of the diaphragm is not open to atmosphere (the shipping bung is left in the gauge) the atmospheric pressure reduces on one side of the diaphragm as the aircraft climbs, but not the other. And the result is what looks like a loss of fuel pressure. I have seen this twice with steam gauges, and the fix is simply to pop out the rubber shipping bung on the top of the gauge body. If this is the problem, then the setup will read okay on the ground, but the the fuel pressure reading will appear less the higher you go. (This probably needs to be checked with the aircraft level in cruise, as a hard climb may show a reduction in fuel pressure, confusing the picture some.) In a perfect world, the atmosphere side of the transducer would be hooked to the static port setup. But a gauge mounted in the cockpit (and so accessing cockpit atmospheric pressure) is accurate enough for practical purposes. A sender or transducer mounted on the front of the firewall is accessing atmospheric pressure there: if mounted in a high or low pressure part of the airflow, this would also affect the reading. In this case I would expect to see the effect immediately after takeoff, rather than progressively as altitude increased.

Skippy, reading back over this, you stated that fuel pressure meets the Rotax spec on the ground. That is quite a wide range, I believe. FYI I normally see approx 4.5PSI at fast idle (booster pump off).

The boost pump raises the pressure further, so certainly will improve the reading. I'm not saying the gauge is the problem, I'm saying it's the way it is hooked up: it's a differential gauge, close off the atmosphere side, and this is what you get. And nobody so far mentioned altitudes or circuits. I just worked an example.

Come at it another way: 912 min fuel pressure 2PSI More normally it is between 2 and 4PSI, I think. The pressure gauge is differential, fuel pressure one side , atmosphere the other. If the atmosphere side is blanked off in some way, that side remains at ground pressure. If you then take the aircraft to 5000', the outside air pressure...and the actual fuel pressure....is reduced by approx 2.5 PSI. So your fuel pressure will appear to have dropped by that much.

You might not think, Nev..........but I've now seen this twice with 912 installations.

Skippy, with a mechanical gauge, this is exactly the result you get when the builder has forgotten to take the little shipping plug out of the body of the gauge: so the gauge internals stay at ground pressure, while the fuel pressure does actually fall with altitude. So: whatever the fuel pressure sensor is, it should have fuel line on one side, and be open to atmosphere on the other. That's where i would be looking.

Me too, Student Pilot......)

Right, well, my view is this: When it comes to ditching there is a fair bit of theory and speculation, but not a lot of what one could call hard data. By digging back into what data from actual events he could find, and extracting some stats, I think that Bertorelli has helped shed some real light on the subject.

Well, Nev, if you have insights not touched on in the thread so far, could you please share them?

Maybe so, Nev. But for those of us flying light aircraft, and sometimes over water, I would say it gives valuable insight.

And a good segment from Paul Bertorelli:

Student Pilot, here ya go: https://www.aviationsafetymagazine.com/features/the-myths-of-ditching/

Who..............wants ta know?????????????? I'm distinctly average........but with a few outstanding bits.........)

Oo...ouch! ...................)

M.........while all this has been going on I have put 20L across 2 tanks, the old fashioned way and been out flying.......twice!