Another Jabiru engine thread

[Guest Andys@coffs]

I also love my Jabiru. With the engine now I hope under control, the only other thing that needs a mod are the brakes. What brakes?

have you got the single or dual calliper brakes on the mains......I was told that the dual calliper wasn't that much better than the single but I found it to be much better with just me on board and better at MTOW but still not ideal. Duals were put on about 50hrs ago

Andy

 

 

[mkennard]

have you got the single or dual calliper brakes on the mains......I was told that the dual calliper wasn't that much better than the single but I found it to be much better with just me on board and better at MTOW but still not ideal. Duals were put on about 50hrs agoAndy

I'll have to have a look next time...

 

 

[facthunter]

I'm not convinced you nee "electronic" fuel injection. A plane engine is nothing like a car environment you are not braking accelerating etc. Fairly simple mechanical is fine with manual leaning and flowmeter. Most of the time you are cruising in a barrow range. There would be RPM settings you should avoid there somewhere too. Nev

 

 

[frank marriott]

have you got the single or dual calliper brakes on the mains......I was told that the dual calliper wasn't that much better than the single but I found it to be much better with just me on board and better at MTOW but still not ideal. Duals were put on about 50hrs agoAndy

Andy's post I find interesting. I have not seen a Jab other then the J120 with single calliper brakes - mine is a 2008 J230, and I was unaware of single calliper brakes on 230s? You live and learn.

Time on brake pads I also find intersting [and I must exclude training aircraft] - as a comparison I got a new set of pads to fit at 400hrs after reading some of the posts here over time and at the 100hrly I found my pads were still the same size as the new ones [to the eye at least] - now at 600 hrs they are still the same, so I haven't fitted them yet. A friend with one has 400 hrs and his are still near new as well. Then another friend with a J230 is on his second set of pads and at least 50/70% gone at 300hrs.

 

My conclusion is the way the brakes are used - posssibly landing speeds?

 

The only difference I can identify is the difference in total time between aircraft pilots in aircraft 1,2 and 3 [in these cases they are all owner drivers, so multiple pilots can be eliminated.]

 

I would be interested to hear what times others are achieving and if need replacing then what is their opinion as to why.

 

 

[Dafydd Llewellyn]

I'm not convinced you nee "electronic" fuel injection. A plane engine is nothing like a car environment you are not braking accelerating etc. Fairly simple mechanical is fine with manual leaning and flowmeter. Most of the time you are cruising in a barrow range. There would be RPM settings you should avoid there somewhere too. Nev

Its main advantages are (1) it's much easier to get a more uniform mixture distribution (as long as the injectors stay clean and keep working properly); (2) The ability to modify the mixture to compensate for a batch of reduced octane fuel - this is likely to become more important in the future; and (3) it's not so inviting to people to tinker with it.

The downsides are: (a) Many more potential failure modes; (b) Needs electrical power; © Needs a purely mechanical "get you home" system. It's MUCH more difficult to certificate than a carburettor system. AND it presents the engine manufacturer with a more difficult liability issue than does a carburettor. So making that leap is no small matter for an aero engine manufacturer, at least for his certificated engines.

 

 

[Dafydd Llewellyn]

Andy's post I find interesting. I have not seen a Jab other then the J120 with single calliper brakes - mine is a 2008 J230, and I was unaware of single calliper brakes on 230s? You live and learn.Time on break pads I also find intersting [and I must exclude training aircraft] - as a comparison I got a new set of pads to fit at 400hrs after reading some of the posts here over time and at the 100hrly I found my pads were still the same size as the new ones [to the eye at least] - now at 600 hrs they are still the same, so I haven't fitted them yet. A friend with one has 400 hrs and his are still near new as well. Then another friend with a J230 is on his second set of pads and at least 50/70% gone at 300hrs.

 

My conclusion is the way the breaks are used - posssibly landing speeds?

 

The only difference I can identify is the difference in total time between aircraft pilots in aircraft 1,2 and 3 [in these cases they are all owner drivers, so multiple pilots can be eliminated.]

 

I would be interested to hear what times others are achieving and if need replacing then what is their opinion as to why.

Them's the breaks (brakes?) - I can't speak from experience with Jabiru brakes; however I can do so for Cleveland brakes: My Cherokee 140 had, as do all Pipers except the ones with those execrable expanding tube types, Cleveland brakes; and the brake discs were very prone to corrosion, unless the thing was in daily use. By the time I acquired it, the discs were badly pitted, and it chopped out pads very fast. I replaced the discs with hard chrome plated ones, and the pad wear all but disappeared. The chrome plate was just starting to get a trifle ragged around the edges when I sold the aircraft three years later, but the pads had hardly worn at all.

 

 

[frank marriott]

Dafydd

 

Yes I should have proof read before hitting the send button

 

 

[mkennard]

re: brakes

 

I couldn't do run ups at 2000 rpm, I found flying during summer the brakes were almost useless. I had to adjust them every 2 - 3 weeks. I use long strips so wasn't in a hurry to stop so I don't think I needed to be hard on them.

 

 

[Bruce Tuncks]

This thread started with a post about how doing anything to your engine could negate your insurance policy. It implied that even if the modification had nothing to do with the claim, you had still negated your policy.

 

Is this accurate? If it is, how can anybody think they will get paid out if they had a claim? How could you prove that you had never done anything at all to the plane you owned?

 

Surely you would need to be wealthy enough to take the insurance company on legally... but if you were this wealthy, why are you not carrying your own risk?

 

 

[jetjr]

J200/400 had single caliper brakes and yes they didnt work

 

Duals are definitely better but not inspiring

 

Im fiddling with different rotors and pads

 

 

[Guest Andys@coffs]

I'm no mech eng so may well be wrong but it seems to me that the master cylinder we have and the leverage available on the brake lever means the pressures available to the callipers is probably below what is really needed, I found that in moving from single to dual the amount of sponginess in the system doubled (and cant be removed with a proper bleed) and under hard prolonged braking the braking affect just fades away even if your biceps are still doing a full arm wrestle on the brake..... where as with the single it didn't fade away, it was just never there to start with......

 

Bottom line, as Frank suggests, don't come in fast if you can avoid it.

 

Oh and something worth knowing if you didn't already, the brass bleed nipples corrode into the aluminium caliper and will snap off when you try to loosen for a bleed, there is a replacement set of nipples from Jab that don't seem to have the issue but in any event I was told to use rubber lubricant on the assembly of the nipple to the calliper body, and to ensure that you change the brake fluid each major service because the corrosion is exacerbated by moisture in the fluid....

 

Andy

 

 

[Oscar]

I'm not convinced you nee "electronic" fuel injection. A plane engine is nothing like a car environment you are not braking accelerating etc. Fairly simple mechanical is fine with manual leaning and flowmeter. Most of the time you are cruising in a barrow range. There would be RPM settings you should avoid there somewhere too. Nev

Nev - it's the fuel availability in the future issue that has me most concerned, with better mixture control second and no icing third on my list, that makes me want to have efi. Perhaps I am overly concerned but what with the Avgas production situation in Australia plus the diminishing number of regional airports (and the airport charges and fuel call-out charges!) I think it very likely that we all are going to find ourselves in the situation of having to fill up with what's available and hope it's OK more frequently - unless we are flying only from/between busy-ish airfields that have the facilities and the fuel turn-over to be able to ensure deliveries of consistently reliable fuel.

 

Jabs. are finicky about what they are fed as we know; but they're not the only engines in the universe that are. Just about all the European 'performance' cars (and the Japanese ones too) run de-tuned versions in Australia because of our known lesser-quality mogas. Even with the ability of the almost ubiquitous efi systems in cars to compensate fairly invisibly to us for differences in batches of fuel, I think we've all experienced instances of 'dud' tankfuls of fuel, and not always from some petrol station way out in the bush. Since we as RAA aviators are really a very, very small batch of users, as we find our available landing sites pushed further from the centres of population, I think our chances of being relegated to the hind tit on the fuel supply cow will only increase.

 

 

[Oscar]

it seems to me that the master cylinder we have and the leverage available on the brake lever means the pressures available to the callipers is probably below what is really needed, I found that in moving from single to dual the amount of sponginess in the system doubled (and cant be removed with a proper bleed) and under hard prolonged braking the braking affect just fades away even if your biceps are still doing a full arm wrestle on the brake..... where as with the single it didn't fade away, it was just never there to start with......Andy

High performance motorcycles have amazing brakes, but almost without exception they either have as standard or are improved by the use of braided brake lines that don't allow swelling of the lines under pressure.. Those lines allow for the use of better hydraulic advantage between a simple hand-operated master cylinder and up to six piston calipers pushing c/f pads onto (huge - 330mm diameter on the top racing bikes) c/f discs. If you watch the motogp racing, you'll see that the riders mostly use just two fingers to pull a bike travelling at over 300 kph down to around 50 kph at around 1.8g retardation - with the discs ending up glowing almost white-hot.

 

Our brake systems are pretty appallingly crude, because to a degree, they are sort of adequate for task (mostly). They could be seriously improved without adding much weight or ridiculous cost,but that probably won't happen unless there is user demand placed on the industry.

 

 

[mkennard]

I remember Rod Stiff at a couple of Natflys ago saying why do you need brakes. Maybe the brakes should have been another thread. Sorry about that.

 

 

[geoffreywh]

the calipers and the way they are "adjusted" are the source of the problem. The discs could be a lot better too.....use m/bike stuff and it will improve out of sight. There are lots of disc manufacturers in Oz.............Have a look at Marc Ingegnio in Italy, That's where I got my stuff. .....Of course the manufacturer says there is no problem! :LOL

 

 

[turboplanner]

The biggest factor in improving brake performance is the disc diameter, and that can't realistically be less than a deflated tyre - around rim size, and with small wheels that may not be enough. Just 25 mm increase in diameter (with the pads correspondingly 25 mm further out) makes a big difference.

 

The second biggest factor is the leverage from the centre of the hand point to the master cylinder.

 

When either of these is less than optimum it becomes very difficult getting a workable result, and in such a light airctraft this is likely to be the big challenge.

 

There are a number of reasons why good brakes are needed to prevent aircraft damage, for example:

 

• A shortfield forced landing into a confined area less than the aircraft's landing roll where survival is your prime objective
   
   
  
• A landing on a very short runway where you have floated longer than expected
   
   
  
• To avoid a runway incursion, or another aircraft's runway incursion
   
   
  

 

 

 

Sure you can fly an aircraft without brakes, or with just enough brakes to do your runups - older aircraft like Tiger Moths had no brakes, but they were designed to operate from all-over fields.

 

While some people have referred to motorcycle brakes, the discs are usually a lot bigger than can be fitted to a recreational aircraft with it's small wheels. There's nothing wrong with adapting motor cycle calipers, lines, master cylinder etc. but if you can't get the fundamental of the diameter optimised, the rest doesn't help that much. Motor cycle brakes are designed to operate from 300 km/hr to zero repeatedly, whereas with an aircraft it's usually one spike brake only, so heat dissipation is not so much of an issue. If you can get an aircraft brake disc red hot, you can pretty much assume the pad/caliper/pressure design is optimum.

 

 

[Dafydd Llewellyn]

Dead right, Turbs - but this should be a separate thread. I'd like to canvass views on whether taildraggers should have an anti-locking valve operated by weight on the tailwheel, to prevent overturn - but not on this thread.

 

 

[Guest ozzie]

I watched the owner of a Storch have a lot of problems trying to get it to stop. Took a while but once convinced to try a softer brake pad braking power increased no end.

 

 

[turboplanner]

I watched the owner of a Storch have a lot of problems trying to get it to stop. Took a while but once convinced to try a softer brake pad braking power increased no end.

Playing around with this could be dangerous and expensive - see Aircraft Brake Systems thread for more comments: http://www.recreationalflying.com/threads/aircraft-brake-systems.121292/

 

 

[biggles]

Andy's post I find interesting. I have not seen a Jab other then the J120 with single calliper brakes - mine is a 2008 J230, and I was unaware of single calliper brakes on 230s? You live and learn.Time on brake pads I also find intersting [and I must exclude training aircraft] - as a comparison I got a new set of pads to fit at 400hrs after reading some of the posts here over time and at the 100hrly I found my pads were still the same size as the new ones [to the eye at least] - now at 600 hrs they are still the same, so I haven't fitted them yet. A friend with one has 400 hrs and his are still near new as well. Then another friend with a J230 is on his second set of pads and at least 50/70% gone at 300hrs.

 

My conclusion is the way the brakes are used - posssibly landing speeds?

 

The only difference I can identify is the difference in total time between aircraft pilots in aircraft 1,2 and 3 [in these cases they are all owner drivers, so multiple pilots can be eliminated.]

 

I would be interested to hear what times others are achieving and if need replacing then what is their opinion as to why.

My recollection is that all Jabs were fitted with single calipers until about 2008 . I have not updated to the dual calipers and seem to manage OK on short strips , using full flap and min speed when possible . I have been known to shut the engine down once safely on the ground and rolling out as ,even an idling prop still generates a fair degree of thrust . Many years ago Jab were supplying disc pads with very soft material but my current ones have been on for around 250 hours and still have minimal wear.

Bob

 

 

[rankamateur]

as we find our available landing sites pushed further from the centres of population, I think our chances of being relegated to the hind tit on the fuel supply cow will only increase.

Fear not Oscar,on all mammals the richest milk comes from the most nether teats so you, like the strongest pup will be well served.

 

 

[facthunter]

It's not a practice with universal application. You have systems not operating. OK in a basic plane. A few six cyl jabiru's have idle speeds too high. You float too far and have to use more brake. Keep you approach speeds on the button. Easy to get fast as a habit. Nev

 

 

[biggles]

A few six cyl jabiru's have idle speeds too high. You float too far and have to use more brake. Keep you approach speeds on the button. Easy to get fast as a habit. Nev

Or come in downwind !!

 

 

[rankamateur]

Interesting aside - Although there are bucket loads of Jabirus coming on the market lately, it is interesting that 5 out of the last six in the members market have the same airframe time as engine hours.

 

 

[fly_tornado]

4 out of 5, is a pretty good record for Jabiru