mikeavison

Guys Guys think about the mechanism. It's nor like an engine part under constant motion. It only gets moved by a few degrees every now and then. So it is not surprising that the mfr does not require a lubricant.

I have an Icon A6E, only a Yaesu model was cheaper when I bought it. I have no problem with range, performance is great. I find programming the stations in is quite painful. The whole user interface not very intuitive but manageable. I don't know if the Yaesu is better in that respect. Good Luck

I would just say about the Savannah , if you go that way make sure you have the vortex generators. Compared with the slat wing version you really are getting something for nothing.

Several people answered the wrong question (why 2 plugs) not what was asked, why the RPM drop. For my money it is due to incomplete combustion (3). Which is why on low rpm engines like Jabiru the drop is too small to notice. Everything happens at half the speed on a Jab compared with a 4 stroke Rotax, everything except the rate of burn progression. So you still get almost complete combustion on low rev engines and little or no drop of RPM.

Mike

Well in UK we are also not supposed to fly recreationally. I think quite unfair. I never feel so alone as when flying solo especially when things aren't going quite right! Just me, the controls, the instruments, the weather above and the ground below. Lets face it I am at least 1000ft from the nearest other human well more than 2m!

Some say, ah but what if you crash , putting additional strain on the health resources. Be honest there are a few crashes per year and most do not require emergency services. Hardly a strain!

Mike (pommie)

About 8 years ago , a Savannah with a Jabiru 2200 was my first plane. And I haven't changed it since . The engine has been completely reliable. I went on a Jabiru owners course soon after I got it which was super-helpful. I learned a lot about some problems with earlier examples of the engine. The two you mention were genuine and serious issues with the engine. Probably not really dangerous, since they didn't cause sudden failure. If you do your engine checks well you would realise the fault was gradually developing. I would say , as well, there may be a lot of reports of unreliability caused by bad use on the owners part. Being air cooled you HAVE to pay more attention to the temperature guages than you would on a Rotax. In standard form the cooling is entirely passive, no thermostats, it relies on a compromise level of cooling built in by the designers and it is easy to make the cylinder heads overheat, and possibly the oil. In UK cold climate there is potential for under temp, which also causes early engine problems. We fitted a TOCA (oil thermostat) which nailed this , though use of blanking tape on the heat exchanger is also a solution. We are up to 850 hours now and it has not missed a beat. I'd advise whoever services it makes careful note of how much tightening is necessary of cylinder head bolts when re-torquing . If it is excessive you are doing something wrong while flying, and storing up problems. Good luck with your purchase, I really like the Jab engine!

Sorry I haven't read all six pages of replies so perhaps someone has already said this.

One bank of cylenders is set back by one cylender width compared withe the other (since the pistons are all in a line).

On our plane the ducts are not different to take account of this, neither is the shape of the the cowling. So when we got it there was a gap between the cowling and the duct which was much bigger on one side than the other. CH cooling was not great. We fabricated a short extension to the ducts so that the cowling meets the duct on both sides now. This improved CH cooling greatly.

I hope this helps

Mike

A lockwire has very limited ability to resist a nut turning, in my view.  If you were in a hurry you'd snap them easily by just undoing the nut or bolt by driving a ring or socket over the wire and undoing the particular fitting. Yes they are supposed to be fitted in  regard to the direction they unwind being immediately noticed as the wire would have to break, before the Bolt moved any real distance. It is NOT any guarantee the bolt has been torqued to the right setting. that's often done with a dob of (usually) yellow paint but that's not foolproof either. I think lockwiring provides a  visual check nothing has moved since it was lockwired and not a lot else. Nev

 

It's actually a force of a very small order compared with the torqueing force and any force required to undo most nuts that are not loose, already.  You only have to break one of the two wires through the bolthead. On a filter it's got a much bigger radius, To be fair many locking devices don't have a lot of strength in their own right. A split pin and castellated nut often permit adjustment, and the nut is not tight at all. Some others have a preload and may be pinned or staked into a groove to lock them. Nev

 

This is to misunderstand how a bolt works. When a bolt comes undone during use, the force retaining it is not the torque applied when fitting it, it is zero. When you tighten a nut onto a bolt it stretches the shank of the bolt (it is elastic). This puts a constant force holding the items together. When there is vibration it causes an oscillating force on the bolt shank, the combined effect is that the net force in the bolt shank increases and decreases around the mean (torqued in force). If the vibration is strong enough the peaks and troughs of the oscillation are greater than the torqued in force, at which point there is no force on the face of the nut during each trough. Of course the vibration does not affect lock wire or loctite in the same way so they tend to keep the nut from turning (notwhithstanding any fatigue and shear effect). 

Incidentally I believe the  reason loctite and wire etc are used so much more on aeroplanes than (for instance) tractors, is that the components are made very much lighter, thinner and so less strong, and unable to withstand the compressive force of a highly torqued bolt. Look at the torque setting on bolts for a wooden prop, barely finger tight let alone hand tight!  Another example is where a bolt is put through a hole drilled in an aluminium tube.

Hopefully my last post on this subject. We used penetrating oil and a G clamp to drive the sleeves out. There was no sign of corrosion so I think they must have been tight from build, which I don't really understand. Anyway we reamed and greased the holes and hopefully all will will now be well. Thanks everyone, especially ibob

Mabel has larger tyres and I was going to get the brakes to bits and see if I could somehow make them better. Might look into doing something with them. The ones on my XL are crappy..as I said they work but only just although I do have 600/6 tyres on the mains. But the caliper sliding doesnt always happen thats for sure

I don't know if maybe the ones on the Sav XL are different and less effective than the ones on the VG.

I was thinking if that were me, I'd sort it out: they'll be even worse now, and the disk isn't designed or mounted to take sideways thrust.Take them off, soak them in kero or some such for a week, then support the plate flat on a steel block and see if a little hammering via a copper drift won't get things moving....

G'day, Mike! (from a southerner now living in Melbourne).Is your Savvy an S? Have had mine for a couple of years now.

 

Cheers,

 

Neil

I bet yours has a Rotax 912 too, instead of the Jabiru engine?

I have a late 2014 S under construction. Brakes appear the same as your pics, and you're absolutely right, those shiny sleeves are supposed to float or slide in the black metal axle plate tubes.(Small difference in what I have is that the black metal tubes are swaged into the plate, not welded like yours, but functionally they should be the same.)

Thanks for your information that is very helpful.

I'd say to you make sure you put a small amount of molybdenum grease on those sleeves they plainly are susceptible to locking up. And re-grease them at every service. Ours are now so tight I think they may be impossible to budge without damaging the sleeve or the plate, and the Sav is not that old. Fortunately the pads hardly wear and for now we have just reassembled it and it works fine.

PS I don't know what brand, there is no writing on them. I'd think they are adapted versions of some other brake repurpossed by ICP the plane kit manufacturer.

It's hard to tell much from the limited info and photo.What brand are the brakes? Are they floating caliper type or floating disc type?

 

If they're the first type then the caliper should float sideways on pins or on the axle to compensate for uneven wear between the inner and outer pad. If they're the latter type then the caliper remains fixed and the rotor (disc) floats sideways on the pins.

 

Either way they can be fitted (or designed) wrongly - here's a link to a post I wrote on HBA about the incorrect design and fitting of the otherwise excellent Black Max brakes - Black Max Brakes

The discs definitely don't float, so I guess the calipers are supposed to. I had not appreciated that many types of brake have been fitted to Savannahs, I imagined just one had and so anyone reading the post who had dismantled one would recognise the picture, and tell me if they had considered the same question. And hopefully arrived at the correct answer. The shiny metal sleeves you can see in the picture, when assembled have bolts through them which hold the piston on one side and the static pad on the other side. So if those sleeves were free to slide in the black metal axle plate, the caliper itself would be able to float. So to my mind this seemed the intention of the design. Our problem arose because all four sleeves ( 2 on each wheel), were locked solid in the black axle plate. We tried some gentle persuasion on 2 of them with no success at all. There was no visible corrosion on either part, so it rather seemed as though they were an interference fit. This seemed contrary to my idea of how they should work, as explained above.

Thanks for your advice.

It's hard to tell much from the limited info and photo.What brand are the brakes? Are they floating caliper type or floating disc type?

 

If they're the first type then the caliper should float sideways on pins or on the axle to compensate for uneven wear between the inner and outer pad. If they're the latter type then the caliper remains fixed and the rotor (disc) floats sideways on the pins.

 

Either way they can be fitted (or designed) wrongly - here's a link to a post I wrote on HBA about the incorrect design and fitting of the otherwise excellent Black Max brakes - Black Max Brakes

The discs definitely don't float, so I guess the calipers are supposed to. I had not appreciated that many types of brake have been fitted to Savannahs, I imagined just one had and so anyone reading the post who had dismantled one would recognise the picture, and tell me if they had considered the same question. And hopefully arrived at the correct answer. The shiny metal sleeves you can see in the picture, when assembled have bolts through them which hold the piston on one side and the static pad on the other side. So if those sleeves were free to slide in the black metal axle plate, the caliper itself would be able to float. So to my mind this seemed the intention of the design. Our problem arose because all four sleeves ( 2 on each wheel), were locked solid in the black axle plate. We tried some gentle persuasion on 2 of them with no success at all. There was no visible corrosion on either part, so it rather seemed as though they were an interference fit. This seemed contrary to my idea of how they should work, as explained above.

Thanks for your advice.

Fitting new tyres I noticed the calipers are not free to slide when the pads wear. From what I can see it seems like the sleeves in the black painted axle plate should slide freely in the plate ( see Photo hopefully.) Ours are locked solid on both sides. Does anyone know if I am right, should the sleeves slide freely or are they pressed in.

Fitting new tyres I noticed the calipers are not free to slide when the pads wear. From what I can see it seems like the sleeves in the black painted axle plate should slide freely in the plate ( see Photo hopefully.) Ours are locked solid on both sides. Does anyone know if I am right, should the sleeves slide freely or are they pressed in.

Just landed from Yorkshire, Savannah with a Jabiru engine