jabiru down brisbane

[Dafydd Llewellyn]

If somebody put a gun to my head and said you must fly a single engine over water or tiger country or what ever but you can choose the engine. I would choose a brand new Lycoming o-320 with about 300 hours TT.

You mean, a "first-life" engine. But NOT the el-cheapo 0-320-H with the ball-stud type valve rockers, that Lycoming made specially for Cessna. An 0-320-E, yes.

 

 

[Dafydd Llewellyn]

I've heard (grapevine, not corroborated) that this accident, whilst not total fuel exhaustion, may have been fuel run-out on one tank - i.e. fuel mis-management. Does anybody know of any findings being released?

 

 

[geoffreywh]

How does that work? I thought that there was only the fuel switch on the centre console......Don't both tanks feed the header with no switches....

 

 

[nong]

What's your advice?

Sorry for delay, Turbs. As we know, dipping is useless due physical shape / proportions of the tanks and variations in transverse slope, filler hole position, etc.

As a school operator, I keep flight sheets recording the duration of each flight. From this, fuel useage can be estimated and recorded. Fuel added is also recorded.

 

Fuel gauges are checked during the pre-flight and which ever of the reading or estimate is the lower, is taken to be the fuel on board. We also rock the wings and listen!

 

Occasionally the tanks are filled to capacity, 126 litres by our measurement, and this provides a "reset". I try to carry fairly low fuel loads for circuits and bumps in the interests of achieving a better climb rate, but, more importantly, reducing structural loads during student induced impacts.

 

 

[Dafydd Llewellyn]

How does that work? I thought that there was only the fuel switch on the centre console......Don't both tanks feed the header with no switches....

Does the 170 have a header tank? Will the fuel necessarily flow to it if the aircraft is not flown wings level, zero slip or skid? I'm not familiar with the J 170 fuel system. As I said, it was grapevine, not corroborated.

 

 

[turboplanner]

Sorry for delay, Turbs. As we know, dipping is useless due physical shape / proportions of the tanks and variations in transverse slope, filler hole position, etc.As a school operator, I keep flight sheets recording the duration of each flight. From this, fuel useage can be estimated and recorded. Fuel added is also recorded.

Fuel gauges are checked during the pre-flight and which ever of the reading or estimate is the lower, is taken to be the fuel on board. We also rock the wings and listen!

 

Occasionally the tanks are filled to capacity, 126 litres by our measurement, and this provides a "reset". I try to carry fairly low fuel loads for circuits and bumps in the interests of achieving a better climb rate, but, more importantly, reducing structural loads during student induced impacts.

Thanks Nong that's a great policy, and very consistent with what I found. My method of dipping the tanks and turning the aircraft 180 degrees is not as good as this.

 

The other issue is venting from the breathers. Since the Jab tanks are so shallow this comes into play at a lot lower tank level. If you have wide "fuel consumption readings", and someone put up a graph showing up to 100% variation a few days ago (forget which aircraft), then venting could be a good place to start looking.

 

Normally with a full tank you would fill after the last flight of the day to minimise the amount of air (which contains humidity = water) in the tank,, but I would never flight plan on full tanks on this basis because a surprising amount will siphon out of the lower vent overnight. Similarly the angles of bank of 5 degrees on to crosswind and 30 degrees in the rest of the circuit will minimise venting in flight - which you can't see. It follows that if the aircraft vents fuel at even a slight angle, then bank angles of 45 <60 degrees are going to pour it out as fast as the lower, and at times the upper vents will allow.

 

 

[M61A1]

Similarly the angles of bank of 5 degrees on to crosswind and 30 degrees in the rest of the circuit will minimise venting in flight - which you can't see. It follows that if the aircraft vents fuel at even a slight angle, then bank angles of 45 <60 degrees are going to pour it out as fast as the lower, and at times the upper vents will allow.

If you are flying balanced, how will the angle of bank affect fuel venting?

 

 

[jetjr]

Only early models had separate fuel taps for each wing tank, they also had some with gascolators and had a "sharks fin" central vent, most were upgraded to current setup I think

 

Header location varies from under pax seat to current rear location

 

Venting is internal, and air locks are posible but unlikely. There is an old SB regarding sags and loops in fuel tank vent lines

 

 

[Aldo]

Think about this scenario for a minute and it could happen

 

Enough fuel for flight plus reserves and for whatever reason 80% of the fuel is in the left tank.

 

Most Jabs that I know fly about 1/2 a ball left of centre

 

• flight is conducted without compensation for the out of balance and or left wing low
   
   
  
• fuel in the right tank is exhausted after x minutes of the flight is completed
   
   
  
• flight continues until the left wing fuel pickup is unported (remaining fuel is outboard due to the unbalanced condition)
   
   
  
• flight continues on the header tank for a further x minutes
   
   
  
• engine stops
   
   
  
• fuel still in tank when inspected.
   
   
  

 

 

 

 

[Aldo]

It would not happen that wayYou are describing a wing low suitiation not an out of balance one

that is a crooked pilot and not a problem with the plane

Deb

 

You're more of an expert than I originally thought!!! But maybe not as much as you think.

 

 

[Guest Andys@coffs]

My Jab230 can be set up to fly balanced feet off, by adjusting the Bowden cable ends on the rudder at any one speed. At a speed other than that one, there will need to be a bit of light rudder adjustment one way if slower and the other foot if faster.

 

If you are travelling for any time at a speed not the one configured then out of balance is very possible cause even light pressure is uncomfortable after time and fuel usage at that time in my aircraft will not necessarily be equal from both wing tanks.

 

I'm well aware of this and while I pay it attention when checking fuel usage vs distance in long nav's I'm much more careful of being fully balanced at all possible times the closer I am to fuel empty.

 

I was taught that during my training and I cant imagine many instructors knowledgeable about Jabs not covering similar ground with a student. If that wasn't the case and the pilot was unaware then a real shame to have to put it down one way only in a park for the want of 5 minutes of briefing....... (The If in this sentence is particularly relevant...I'm not judging one way or the other.....)

 

Andy

 

 

[Aldo]

It would not happen that wayYou are describing a wing low suitiation not an out of balance one

Think about it Deb

 

If you have a situation where the aircraft is out of balance (due to design or lack thereof) in this case ball left of centre, the easiest way to counter it is to fly left wing low, it is a pain in the backside to fly all day with your foot on the rudder, I know as I have one, but I'm also very aware if I'm low on fuel this situation is very possible.

 

The best remedy is to have a trim tab installed on the rudder all problems gone.

 

 

[AVOCET]

Think about it DebIf you have a situation where the aircraft is out of balance (due to design or lack thereof) in this case ball left of centre, the easiest way to counter it is to fly left wing low, it is a pain in the backside to fly all day with your foot on the rudder, I know as I have one, but I'm also very aware if I'm low on fuel this situation is very possible.

 

The best remedy is to have a trim tab installed on the rudder all problems gone.

You can bring it around if you like and ill rig it properly for you .

 

Mike

 

 

[turboplanner]

If you are flying balanced, how will the angle of bank affect fuel venting?

If you are flying balanced I agree, but we are dealing here with RA aircraft and RA pilots where the aircraft is usually in balance only part of the time (there was a thread only a few weeks ago in which balance was discussed), and unless you are in perfectly smooth conditions there is also a vertical g force alternation.

As far as one way valves in the fuel cap are concerned, they work about as well as the gauges. I've had the pleasure of gingerly moving a Jab out of a cloud of vapour and hosing down the area one morning.

 

 

[Dafydd Llewellyn]

Think about it DebIf you have a situation where the aircraft is out of balance (due to design or lack thereof) in this case ball left of centre, the easiest way to counter it is to fly left wing low, it is a pain in the backside to fly all day with your foot on the rudder, I know as I have one, but I'm also very aware if I'm low on fuel this situation is very possible.

 

The best remedy is to have a trim tab installed on the rudder all problems gone.

Erhm - I'd rather have a spring-trim device, in a small aircraft; could be as simple (and light) as a piece of exerciser cord ("Occy strap"). Tabs are a potential source of flutter; if you use an irreversible tab drive, it gets to be a complicated gadget and a maintenance pain; if you mass-balance the tab, this un-mass-balances the rudder, so one way and another you get added mass at the tail, which means about four times that mass up front to balance it - or the engine moved further forward, which increases the de-stabilising effect of the propeller - and around it goes. (Definition of an elephant: A mouse, designed to meet a military specification). That's NOT how Rod Stiff got the Jabiru airframe so light without compromising its strength; he did it by subtracting things, not by adding them.

 

 

[Dafydd Llewellyn]

I try to carry fairly low fuel loads for circuits and bumps in the interests of achieving a better climb rate, but, more importantly, reducing structural loads during student induced impacts.

Actually, the wings are still carrying most of, if not all of the weight of the aircraft at the point of landing impact. So downward bending of the wings due to the landing impact is actually more a case of relief of the upward load; so if the wings are what you are concerned about in the student landings, I don't think you need to carry minimal fuel loads for that reason. I agree, carrying less fuel will make life easier for the undercarriage.

 

 

[Guest Maj Millard]

Did some flying on the weekend in the first kit built Jab completed in Australia (now VH-JBU) recently rebuilt and now with a 2200 replacing the original 1600. Did notice a tendency to turn to the RIGHT even with the ball well centrered. Owner said it used to go left prior to rebuild. I suggested he drop the right hand flap down very slightly. Other than that it seem to perform well..........Maj....

 

 

[Jabiru Phil]

Had the same problem some time ago

 

Lame suggested a trim tab

 

After some thought I altered the spat angle slightly which fixed the problem

 

Spats are now marked so that reassembling after a puncture etc returns them to standard

 

Worth looking into

 

Phil

 

 

[Teckair]

I was talking to someone today who seems to have had a similar problem. A Jabiru has crashed after fuel starvation which stopped the motor and still had fuel in one tank and should have had sufficient fuel for the flight.

 

 

[Guest Maj Millard]

Had the same problem some time agoLame suggested a trim tab

After some thought I altered the spat angle slightly which fixed the problem

 

Spats are now marked so that reassembling after a puncture etc returns them to standard

 

Worth looking into

 

Phil

This one didn't sport any spats. I consider myself to be pretty good at trimming aircraft so they fly straight with out any control imput. Generally this can be easily achieved with simple control- surface adjustments, if you know what you are doing. Except maybe the rudder which gets hit with swirling air rotating around the fuselage from the prop. Personally if you need to attach a fixed trim tab you've pretty much failed or something is seriously out of wack on the aircraft........Maj...

 

 

[Guest Maj Millard]

I was talking to someone today who seems to have had a similar problem. A Jabiru has crashed after fuel starvation which stopped the motor and still had fuel in one tank and should have had sufficient fuel for the flight.

Would I be considered a Jab Basher if I suggested that is the result of piss poor design or lack of proper testing ??.....

 

 

[Teckair]

Would I be considered a Jab Basher if I suggested that is the result of piss poor design or lack of proper testing ??.....

Don't know but a plane that is difficult to check the fuel with and relying on what the last guy reckons they put in tank is unacceptable to me.

 

 

[fly_tornado]

More than likely

 

 

[turboplanner]

Would I be considered a Jab Basher if I suggested that is the result of piss poor design or lack of proper testing ??.....

You would by some

 

 

[Dafydd Llewellyn]

Don't know but a plane that is difficult to check the fuel with and relying on what the last guy reckons they put in tank is unacceptable to me.

Well, don't fly any aircraft with bag tanks, then; (and yes, quite a lot of Cessna have them, as well as Beech 33, 35, 55, 58, or a Lancair 4 - or, in fact, about half the GA fleet.) The only practical way with any of these is to start with full tanks. The reality is that fuel contents gauging is a significant problem in a great many aircraft.