Ultralight crash into lake Jindabyne

[winsor68]

Bubbleboy, It is common practise on our level of aircraft to use screw-clamps and rubber fuel hose. I won't use any fuel line unless it is black, from the US. I have been dissappointed with the red rubber hose, as it seems to crack the outer sheath fairly readily. If you putting fuel line in a position where it won't be easily accessable, like for instance Savannah wing-tanks, than I would definitly use US made, black rubber hose, and nothing else.All rubber hose looks good and equal when it is new. I see a lot of fuel line with years of use on it, so I am in a position to make good comparisions. It is something I take a particular interest in, and there is nothing but US made hose in my plane.

If you are pushing rubber hose onto barb fittings, look for a good tight fit, but not so tight that you need to be Attula the hun to push it on. Also not so loose that you use the clamp to squeeze the rubber onto the barb to seal it. you can double clamp on lines that are pressurized by boost pumps if you have the room for two clamps. I use nothing but quality Tridon brand Stainless clamps. Do not overtighten clamps.

 

Fuel line leaks are a pain, and dangerous, so do your best to avoid ever having any !...remember keep it as simple as possible, for added reliability.............................................Maj...

Maj... Do you know what comes standard in the wings of the Sav S Certified? The one I fly has long range tanks... apparently they are an option.

 

 

[Bubbleboy]

Hi BubbleboyYou picked up on that mistake I made back then. The wings were one of the first things I made getting on to almost a year ago now. Those clamps are stainless Tridon clamps that Maj suggested BUT they are not like the rest of the clamps supplied in the kit. Those clamps are all solid no "teeth" holes in them. The main fuel line has them you can see in the pic and I have these now in the smaller size for the ones you picked out in the pics. Although there is no pressure on these lines I am replacing them with the norm used throughout the kit on all fuel lines. I will fix these up when the wings come back over to here. I made them at my mother inlaws place as I didnt have the room here then. I also have nutserted all the cover panels for the tanks rather than rivet the panels as done in the kit. This will give me easier access if anything goes wrong in the tank area or I have any leaks...a lot of work to do all the nutserts but better than having to drill out all those rivets and there is a lot in 4 tank covers

 

Mark

Hi Mark...I wasnt trying to be smart or anything it was just one of those things that "rung a bell" when I saw it. I had no idea if it was right or wrong hence why I posed the question. Im glad you posted them so now I know. Keep up the good work!

Scotty

 

 

[Powerin]

Fuel systems have to be the safest (& simplest) possible. Fancy gauges are not the answer either. The more complex the fuel system the more chance it will bite you. (one day).

I've been reading quite a few fuel starvation accident reports today. I'm yet to be convinced that simplest is best (with the greatest of respect to you Nev). I would argue that the simple fuel systems we have now bite very hard. I'm new to aviation, but I operate a wide range of machines and my experience is that usually the more sophisticated the machine the more reliable it is. I could bore you with many examples.

The measure of a system's overall reliability is not a function of its pure mechanical reliability and simplicity. Human factors come in as well in terms of ease of use and ergonomics. I can't help thinking that the humble fuel tank selector is a good example. It's simple, and if it's used correctly it's extremely reliable. Yet pilots continue to die as a result of incorrectly using this simple device.

 

If a fancy fuel gauge system or a series of automatic valves could help in fuel management it might save lives just by removing a level of human interaction.....even if the extra complexity introduces a slight increase in the risk of pure mechanical failure. There's always the argument that passive fuel monitoring as opposed to active fuel management might encourage complacency. But I think that the statistics show that complacency is just as big a danger with simple active fuel management.

 

 

[Guest Maj Millard]

Mark, Generally the solid type clamps that you refer to are fine. They do come in a couple of styles, Rotax uses them on thier engines both for fuel and coolant hoses. If the hose is the correct size, and the fitting that it is going is a barbed or raised type, then the rubber hose should fit on firmly, and not want to come off.

 

The use of clamps ensures that it doesn't come off, or leak in service. I wouldn't recommend the non-use of clamps in aircraft......................................................Maj...

 

 

[turboplanner]

Pow and Nev you are both right in the areas you are referring to.

 

Aviation history is littered with fatalities caused by bad design and Human Factors.

 

The simplest design of having a single tank above the Carby, which self drains, with a carby float valve strong enough to lock off the flow and seepage when the carby is not supplying fuel would be foolproof, but I've never seen a float valve reliable enough that dangerous seepage doesn't occur whenb the unit is not being used, and this can create a fire hazard.

 

The next step, to prevent this, is a positive tap and this introduces three issues:

 

(a) If the designer isn't careful (and most just guess), the tap bore reduces fuel flow to the point where at full throttle this becomes the main jet, and seizures follow

 

(b) If the Tap location isn't obvious, or isn't reachable in flight (as in the case of John Denver's accident) there will be HF issues

 

© As soon as you have a tap Human Factors comes into play big time, and from past posts on this Forum, most people seem to hate the study of Human Factors

 

As people step up from this, the combination of design and human factors make a fuel starvation more and more likely.

 

For example a lot of layouts cause the self draining dynamic to be lost, and allow air locks to form in the line creating a whole raft of issues. and the undoubted advantage of wing tanks which reduce the need to allow for COG changes in flight introduce new dangers. Examples of the are the bizarre lengths needed just to correctly identify the amount of fuel in a Jab, where the tanks are so flat that even physically dipping them requires the aircraft to be dead level. One of the reasons we are taught in GA to crab down and sawing straight at the last minute is for problem layouts like the 172 where the the pickup is raised above the fuel level and you lose power just when you realise you're a fraction low for the threshold.

 

The Savannah layout has been mentioned several times, and a gravity feed into a sump which will allow substantial roll and provide a low fuel warning with plenty of time to find a place to land is an ideal layout (bit only IF the wing tanks drain)

 

Putting clever fuel control taps into that system re-introduces Human Factors, particularly of you have passengers or weather issues.

 

By Human factors I mean something like my own case - the simplest of mistakes with a one tap system in a Victa. It was flying club policy to rotate the selector to OFF when shutting down for the day. So you knew in the pre-start Checks that Fuel On meant turn the selector to ON. I jumped in one morning in a hurry, turned the selector and the engine cut out on the long taxi to the Moorabbin Holding Bays.

 

Or in flight where a fuel switch from Left to right, right to left etc is easy to schedule and comply with every 40 mins on an uneventful cross country flight, but a Human Factors issue when bad weather closes in, the terrain requires a lot more navigation work, or the Pilot and passenger are chatting to each other.

 

This becomes magnified on a long local flight, maybe looking at local scenery where there is no formal Flight Plan and the looking, postioning and talking produce a Human Factors issue.

 

I've always wondered about the supposed safety of aircraft fuel systems with this reliability and human factors achilles heel, and what Powerin is talking about is a sophistication which would take away these threats.

 

 

[facthunter]

Thanks for your lengthy and considered response Turbo. Human factors are very much involved with fuel management, as you say. Even the simplest of systems can be 'cocked up". Some of this is just bad design also. (Ambiguous fuel selector knobs).

 

Perhaps a guard over the engine start switch saying remove only after checking fuel selector ON, or a fuel pressure gauge fitted. ( no use with a gravity system). . The most perfect engine performs badly with no fuel.. Thieves have stolen fuel and the pilot has not noticed the missing amount, having filled it the night previously. I guess we just keep emphasizing the need for vigilance and care. Know and understand your fuel system. Nev

 

 

[turboplanner]

The guard over the engine start switch reminds me of the lateral thinking of an old Scottish Engineer from Leyland.

 

Leyland produced a bus for South Africa called the Kudu.

 

They were having a lot of engine failures on the Capetown - Durban run so the Scottish Engineer was sent out.

 

He quickly found that the indigenous drivers were ignoring the temperature lights.

 

Lachie made up some kits using a 3" diameter red stop light and sent them to the operators.

 

Unfortunately the engine blow ups continued.

 

"How could the miss THAT" he thought and caught another plane out to South Africa

 

This time he found the drivers had complained about the red lights glaring in their faces, and solved the problem by smashing the lights.

 

Now Lachie wasn't stupid and he'd observed the absence of footwear on the drivers

 

He called the buses in one by one and carefully re-routed the radiator overflow pipe into the driver compartment exiting just above the big toe position

 

That was the end of the engine blow ups.

 

 

[facthunter]

Lateral thinking. Wouldn't work today. OH&S would require heat resistant shoes be supplied. Nev

 

 

[turboplanner]

And you are 100% correct!