jabiru down brisbane

[Dafydd Llewellyn]

OK, it's a while since I looked at a 160, and I've never looked closely at a 170. In that case, an outboard pickup running down the lift strut would work well, I believe. It would be "messy" for rigging and de-rigging, and may increase the risk of fire in a crash, those aspects would need to be assessed against the design standard. It would also allow the header tank to drain to the low wing, unless it had non-return valves - which introduce a diabolical "hidden function" into the equation. The overall benefit of this versus simply teaching people to fly coordinated seems dubious.

 

 

[aro]

An outboard pickup should siphon if it is run through the wing, as long as the join is well below both pickups and fuel can flow freely both directions?

 

 

[AVOCET]

I think you'll find the tanks go all the way to the wingtips; they did on the prototype. However I suppose an outlet at the tip than ran inboard to the lift strut and then down inside the strut might siphon.

The prototype had long thin full length tanks , but had issues with fuel leaking out the vents on uneven ground.

The later jab wings are about 1500 mm long from the wing root and sit behind the main spar .

 

Also having fuel lines front and rear draining into the sump means that all the fuel drains out of the wings .

 

The fuel left in jab wings is minimal , may be 200 ml ?

 

Mike

 

 

[Dafydd Llewellyn]

Ta - that clarifies it. Candidly, I try to avoid non-return valves in fuel systems if at all possible; they have to work at such minimal pressure differentials that they are a considerable reliability issue; and extremely difficult to check in many in-tank installations.

 

 

[Oscar]

It still seems to me that adequate attention to one's flying - and adequate knowledge of the 'peculiarities' of the aircraft being flown - is the simplest and most effective way. The J170 POH does not contain any warning / information regarding flight with low fuel levels, perhaps that might be an upgrade that Jabiru might consider.

 

It it were my Jab with wing tanks (and especially no header tank) on the line, I'd write up an information sheet for users that included a note re flying with low fuel levels (amongst other things!) that the intending user should be given and required to read and (probably) sign off - if for not other reason than trying to limit recourse to my insurance company and incurring later increased premiums.

 

 

[motzartmerv]

The 170 suffers extreme adverse yaw, and is one of the most difficult 'rudder' aeroplanes around. That being said, flying with fuel levels low enough for this to cause a starvation, is always going to end in tears. It may cause a tank to empty faster then the other one, which is standard for most types anyway.

 

Proper planning will stop this type of accident ever happening.

 

 

[turboplanner]

It still seems to me that adequate attention to one's flying - and adequate knowledge of the 'peculiarities' of the aircraft being flown - is the simplest and most effective way. The J170 POH does not contain any warning / information regarding flight with low fuel levels, perhaps that might be an upgrade that Jabiru might consider. It it were my Jab with wing tanks (and especially no header tank) on the line, I'd write up an information sheet for users that included a note re flying with low fuel levels (amongst other things!) that the intending user should be given and required to read and (probably) sign off - if for not other reason than trying to limit recourse to my insurance company and incurring later increased premiums.

That would win you Dufus of the year Oscar, better to get that Jab built, and start real world measuring; it's not hard, you just have to do a little homework, the sort of thing that used to be done when Endorsements were around.

 

 

[Oscar]

Heck, Turbs, you can be hard to please! Still, ANY award is better than none, as long as they spell my name correctly..

 

 

[Old Koreelah]

Surely, a simpler idea than four fuel pumps, is to have a header tank and if you want, inboard feeds from both in the normal location plus outboard feeds that come down the lift struts (they have to have fall from the end of the tank to the header tank so that no point of them is above the tank-end with that wing low, obviously).

In my experience, if air is available, a pump will draw that instead of fuel. Why complicate matters and install more failure points?

 

 

[Dafydd Llewellyn]

Are you being logical AGAIN? I've spoken to you about that . . .

 

 

[Oscar]

The 170 suffers extreme adverse yaw, and is one of the most difficult 'rudder' aeroplanes around. That being said, flying with fuel levels low enough for this to cause a starvation, is always going to end in tears. It may cause a tank to empty faster then the other one, which is standard for most types anyway.Proper planning will stop this type of accident ever happening.

I bow to your experience here, Merv, but for adverse yaw, a 20-metre span Janus-C certainly required a healthy bootful of the bits that your feet sit on to get it to turn decently. A bit of string on the canopy in front of your eyes is a damn good heads-up display of uncoordinated flying.. My power experience is way too low to comment with other than 'newbie' curiosity, so don't flame me for that admitted situation, but is it common that people fly power without realising that they're holding the aircraft in an unnatural position? I used to routinely and consciously take my hands and feet off the controls probably about every five minutes, except when climbing in thermals, to simply ensure I wasn't fighting the aircraft through the sky without realising it, that I had trim set correctly etc. In a glider, on a hot day, you have to remember things like fluid intake and getting muscle-bound from tension; it's the equivalent of the 'check the instruments' on the straight in motor racing.

 

Here's a serious question: would it help if light aircraft that don't have wing-leveller servos, had a simple thin line across the windscreen in the eyeline set at the horizontal so one is constantly reminded of the aircraft orientation vs the horizon? I need bi-focals these days to monitor the panel and even with an A/H, a simple reference to the horizon would be handy for out-of-the-cockpit flying. That line doesn't need to be set at 'the horizon' to be useful, it just needs to be an aide memoire of the relative angle of the aircraft vs the horizon. We used the same technique in yacht racing: as the skipper, you'd sight the next mark when coming off a tack, note its position vs say the forestay, and once you'd gotten to best AoA vs the wind direction, try to hold that line.

 

 

[turboplanner]

Build the Jab, build the Jab, and you'll be a power flyer and can then share the excitement we wall experience in this exciting sport, and it will save your keyboard too.

 

 

[Oscar]

Turbs - I'm building, I'm building! Fuselage is back on its wheels after the repaint (yesterday), but engine developments have intervened in the grand march of progress. The devil is in the details, and this machine was originally a factory 'hack' for the development of the 2200 engine (was build no #50), and there's a lot of more modern and better practice to be included. SBs to be incorporated; seriously crap maintenance work to be remediated; flow-on effects of changing major aerodynamic components to be compensated for, tested, and incorporated in the EO. A winter so far that has had temps. below the workable limits for LC3600 for the last nearly three months hasn't helped, either..

 

Hey, and my keyboard is about due for an upgrade anyway.

 

 

[gandalph]

That would win you Dufus of the year Oscar,

Why's that Turbs?

 

 

[motzartmerv]

oscar, yes a lot of guys fly one wing down, and/or half a ball out. It drives me nuts!!!

 

The jamtar used to be quite a ruddery acft to fly, but to be fair, powered acft with no rudder trim are suffering from an added influence, which is generally the reason for the half a ball issue.

 

A bit of pressure is almost always needed in the 170 to keep it true. Again, to be fair ive only flown 2 170's so not as much of a 'stat" to draw on, but i am often having to tell pilots something like this:

 

Me" Ok we have full power set and the climb attitude attained, keep pressure on the right rudder to keep the ball centered"

 

Student: " Ok turning left, clear right-center-left, left aileron and rudder to roll on bank of 20 deg's"

 

Me: " No, not left rudder, just less right rudder"

 

Student " Huh? Im using left aileron, ??"

 

me : " yes, I know, but your in the climb attitude and have full power set, so right rudder is needed"

 

Student: Uumm...I swear you said, when turning, use rudder and aileron together, so left aileron, left rudder yea?"

 

Me: Yep, i did say that, but it doesnt always work that way..Im sorry..i dont design them, I just fly them"

 

Student:" Ok, can we make this a full stop..Im confused.."..

 

And so on...

 

 

[turboplanner]

Which is what the academics need to keep in mind rather than just talking about theory, assuming balanced flight just naturally occurs.

 

 

[pmccarthy]

I have two balls which hang differently. They are about half a ball different. Some days I centre one, some days the other, trying to find out which gives the better balanced flight and best GPS groundspeed. It seems to differ on different days, depending on a range of factors which I haven't yet figured out.

 

 

[Dafydd Llewellyn]

Which is what the academics need to keep in mind rather than just talking about theory, assuming balanced flight just naturally occurs.

So how would you fix it, Turbs? 99% of single-engine propeller-driven aircraft are fundamentally assymetrical; only the ones with contra-rotating propellers are not (Seafire 47, Macchi-Castoldi MC72, and I'm sure there was another one . . .). I'd dearly like to know how, and I've been studying aircraft design for 50 years. (Contra-rotating props are out of the question nowadays, due to noise regulations).

 

 

[coljones]

So how would you fix it, Turbs? 99% of single-engine propeller-driven aircraft are fundamentally assymetrical; only the ones with contra-rotating propellers are not (Seafire 47, Macchi-Castoldi MC72, and I'm sure there was another one . . .). I'd dearly like to know how, and I've been studying aircraft design for 50 years. (Contra-rotating props are out of the question nowadays, due to noise regulations).

Fairy Gannet

 

 

[turboplanner]

So how would you fix it, Turbs? 99% of single-engine propeller-driven aircraft are fundamentally assymetrical; only the ones with contra-rotating propellers are not (Seafire 47, Macchi-Castoldi MC72, and I'm sure there was another one . . .). I'd dearly like to know how, and I've been studying aircraft design for 50 years. (Contra-rotating props are out of the question nowadays, due to noise regulations).

I don't need to fix it; I walk away from any aircraft that flies like a thrown toilet roll, particularly certificated ones that do that, as we all should walk away, and I'm happy with the handling of the ones I do choose to fly, and I recognise that I have to learn how to accurately measure fuel capacity and fuel burn for these.

 

I wasn't one of the several who assumed automatic balance in a turn.

 

 

[Dafydd Llewellyn]

Fairy Gannet

No -that was a twin-engined aircraft in disguise. Westland Wyvern. (And Wright Flyer, if you think about it).

 

I don't need to fix it; I walk away from any aircraft that flies like a thrown toilet roll, particularly certificated ones that do that, as we all should walk away, and I'm happy with the handling of the ones I do choose to fly, and I recognise that I have to learn how to accurately measure fuel capacity and fuel burn for these.I wasn't one of the several who assumed automatic balance in a turn.

Adverse aileron effect always increases with increased wing span in proportion to fuselage length; that's why doing some early training on gliders is good for curing "lazy feet". To a degree, it's a price you have to pay for increased aerodynamic efficiency. However, I agree that quite a lot of aircraft seem to have their vertical tails designed by eye; and what we are accustomed to thinking of as "pretty" in this regard is based pretty much on WW2 fighters - almost all of which had vertical tails that were barely adequate; you only have to look at the development history of the Spitfire - its vertical tail almost doubled by the Mk 24. As my flying experience increased, I found myself increasingly irritated by aircraft with inadequate directional stability, so I know what you mean. There are quite a lot of aircraft I'd walk way from, too.

Also, most vertical tails are, even now, incorrectly designed for spin recovery. If the designers MUST imitate the F 86 swept tail, they could at least learn something from the evolved form of it on the F-18 - it has two of them, and each is large enough to be worth hiring as advertising space . . .

 

Another aspect of this problem is improper control harmonisation; and both the early Jabiru and the Skyfox suffered from this; the rudder forces were too light, so it had very little "feel". Quite a few gliders also have this defect; the H201 Libelle and the Ka2 were amongst the worst - but people get used to them and love them (I didn't). I've not sampled much of the current crop of recreational aeroplanes, they don't turn me on, so I can't comment on them; but the desirable control harmonisation is generally considered to be that the ailerons should be the most responsive control relative to the pilot effort; the elevator should be twice as "heavy" as the ailerons, and the rudder twice as "heavy" as the elevator. I've found many gliders and such recreational types as I've flown, the opposite way round - the rudder is lightest and the ailerons heaviest. This does not make them good training aircraft, I should imagine. Once you'e experienced an aircraft with correct harmonisation, the others become quite annoying to fly.

 

So I agree, Turbs, but that does not answer the question. Adding rudder trim is treating the symptoms, and it's something you can forget in pre-take-off checks and it can be a real nuisance in an aborted landing.

 

 

[Teckair]

No, remember that the report on the Brisbane prang that was the original subject of this thread, has not yet been issued - unless I've missed something. This question of fuel-still-in-tank-due-to-flying-crabwise is still conjecture. Teckair mentioned another, but did not identify it or give a link to the report that reached that conclusion. I asked whether anybody had knowledge of a verification of this rumour, and this whole debate took off without anybody answering that question.

OK finally got permission to give details on the second prang The aircraft was E24-7758 and the incident happened in Gascoyne Junction last Sunday. This aircraft had major modifications carried out on it. From memory it was a J 230 with a 120 HP Lycoming or Continental fitted. The pilot said it is a write off but he may not know how good the factory is at repairing smashed aircraft.

 

 

[motzartmerv]

Not the mag issue again?

 

 

[Teckair]

Not the mag issue again?

I was told it was fuel exhaustion with about 40 litres remaining in one tank.

 

 

[Teckair]

was that a 233 or a 235?

I do not know.