Bruce Robbins

Hi Happy Flyer, I can understand the icing, but how does C of G and trim affect the stall AofA ? Or are you just referring to the stick position? Regards, Bruce

Just to clarify, The new Jab engines use roller Lifters, not roller rockers.

G'day Ozzie, I'm probably getting into semantics, and definitely off topic, and I'm sure you know all this, but the important point to me is that it is the plane moving through the air, not the air moving relative to the ground, that makes the wing work. Quite a few students and enough qualified pilots to be scary still think of wind in respect of the ground and relate that to how the aeroplane is affected. ( " I need to hold rudder to counteract drift", "I get more lift when I turn into wind" etc etc etc) Relative wind (which I prefer to call relative airflow) is the movement of air relative to the aeroplane only, with no reference to the ground or any other point of reference. In a dead still air mass ( no wind), an aeroplane flys nicely by moving through the air, thus generating what the pilot in his open cockpit feels as relative airflow. Wind tunnels reverse this, and move the air past a stationary object, so it is easier to study. This must however distort the behaviour being measured to some extent, because the air now has movement and inertia that it does not have in real life. I rarely fly in 120 knot winds, but I often fly in a 120 knot relative wind. :) That was the point I meant to make in the previous post. The behaviour shown in wind tunnels by streamlines and staccato puffs of smoke may not be the same as in real life. Daffyd and the aerogeek might be able to show the difference is negligible, but it must still be there. Going back to my feeble joke. If the plane is attached to the ground by a rope in a 50 knot wind, you can sit in the plane and make it fly nearly as high as the rope is long. Cut the rope and the flying soon stops. It is not the wind that makes us fly, it is the movement of the aeroplane through the air.

Not so, I'm sure I've read something about it somewhere. :) We fly aeroplanes, not kites, so unless you forgot to remove the tie-downs, then it's not wind that makes a wing work.

Sorry Aro, I type too slow. Dafydd said it better.

Remember that wind tunnels are used to enable us to study and measure what is happening. In real life the air stays still and the wing moves. Sometimes it's more important to just know what happens, rather than why.

........because the leading edge of the wing has "split" the air molecules that were just hanging around together, and forced a whole pile of them to go under the wing, leaving a large area above the wing with fewer molecules and thus lower pressure. Easier to visualise if you hold the wing at a reasonable angle of attack.

Just to clarify,.... Local QNH as in relevant to the aircraft location, not the " local QNH" you might have set before departing Bob's farm

The Transponder reports Pressure Altitude, and the ATC software system uses the local QNH to see the aircraft altitude. Prevents the dumb pilot reporting wrong altitudes cause he has the wrong QNH, thus assisting noise minimisation.

And it is Magnetic Track, not heading.

0 - 179 is Odds (plus 500 for VFR) 180 - 359 is Evens

Engine has always been operated on Avgas

Louie, Check with the prop manufacturer. The torque settings vary depending on the prop and the mounting method. Props can be dangerous things to experiment with. Bruce

It is a factory built 230, which I cross hire from the owner. 2.5 years old, hollow pushrod hydraulic motor with 480 hours, used for owner's trips and our cross country training.

Hi Andrew, Both were failures of the valve train. First one was due to the top valve spring retainer suffering from rapid wear, then detaching, allowing the valve to drop down into the cylinder. Engine remained at idle through to touchdown. Second was due to a detached valve head, followed thirty seconds later by the engine stopping with a pretzel shaped Conrod after the valve head had smashed the piston into pieces. We were about 4 miles away from Mittagong at the time, but with sufficient height to setup for a safe dead stick landing. I don't know as yet whether the valve head detached first, or the valve stuck open and the head was then broken off by the piston. Regards, Bruce

Frank, We have also had a faulty electric pump cause a similar problem. The two pumps are in series, and Jabiru do not plumb in a bypass line. In this case it was Boost pump off - ops normal, pump on - engine faltered. Replacing the electric pump solved the problem.

Reduce the MTOW by a few kilograms.

The English Jab is a different model, based on the SP, and with lighter MTOW, thus has better performance than our 160/170's.

NavBag, available on Play Store.

Using a centre line check is good but measuring from the spinner doesn't work due to most aircraft having engine thrust line offset.

It is very difficult to use a GPS to calibrate your ASI to the required accuracy. It requires you to fly a triangular course and then compute the crosswind effect to arrive at the actual airspeed. You also have to factor in density height, and of course fly very accurately. A few minutes with Google will dig up various spreadsheets that have been made up for the purpose. OK for basic accuracy tests. Much easier is to build a manometer and do it in the comfort of the hangar. I have found this to be very simple and accurate, and can also be used for static instrument tests and pitot and static pressure tests. Again, use Google for all the details. The requirement has always been there, along with the transponder checks. Now that we are flying above 5000 feet AMSL and mixing with RPT and IFR traffic it becomes even more important.

G'Day Russ, I have 3 x Jabs in a flying school, so change tyres often. We used to battle breaking the bead and removing tyre until showed an old LAME's trick. Wipe a thin (very thin) smear of silicone grease (available from Bearing Supply shops) on the bead and rim before replacing the tyre. Next time you change the tyre it can be pushed off by hand. I was initially worried about the tyres spinning on the rim, but after four years, a few thousand hours, and about ten thousand student landings, we've never had a tyre move. Cheers, Bruce btw: "Glue" the brake pad nuts in with silastic or epoxy, remove the bottom bolt only, then swing the aluminium pad carrier out of the way to remove the wheel. (Might only work with the factory wave discs)

Hi Luke, I can do taildragger endorsement at Wollongong on a LightWing, and Two Stroke at The Oaks (near Camden). SRFC at The Oaks also used to operate a two stroke LightWing, but have an idea they have sold it. Pm me for more detail. Bruce

Hi JetJr, I agree. It's not the new nuts causing the problem. I know of shops replacing broken through bolts in the past, only to find that the engine wouldn't turn over after torqueing up the new bolts. I did the 12 point upgrade before they were officially released, and have had three engines with broken through bolts. My opinion is that the old nuts were losing torque, thus reducing the clamping force, and allowing the crankcase to start fretting , and the bolts to experience cyclical loading leading to metal fatigue and failure. Deadstick, if the mains closed up after replacing the nuts, then you were on the way to a broken through bolt. Can't see how the crankcase halves closing up would affect cam followers, unless it was damage from debris in the oil, or more likely low oil pressure in the galleries due to the larger clearances in the main bearings and crankcase halves due the fretting. The standard Jabiru oil pressure pickup point will not always show up low pressure in the gallery either. Bruce

Volksy, Just the opposite. At touch down the wheel simply castors in the direction of travel. The "exit stage left" is usually caused by fat feet on the brakes, instead of "heels on the floor", or putting the aircraft down pointing off to the left 'cause the pilot is looking through the prop centre rather than straight ahead. Pushing around the hangar though, I agree is a bit of a pain in the **se. So is taxying in a strong crosswind. And there is that time on takeoff and landing when the airspeed is not high enough for the rudder to work, but the crosswind is turning the aircraft, requiring brake pressure to steer. In general I agree with you, I don't like them.