Bruce Robbins

Geoff, You will not need any more than a few grams, certainly not any lead. One common method is a spray can of clear lacquer. Couple of coats on the light end till it just becomes the heavy end, let it dry, and you should be pretty close to the mark. Bruce

Tim, Do you have a time in mind? Bruce

Hi Matt, Ever "captained" or been for a ride in a tinnie with a little outboard motor attached? Grab said tinnie, sit yourself and Kaz up the back so you can hang onto the control arm attached directly to the outboard motor and Kaz at the same time. Start 'er up (the motor that is), point the bow out to sea and twist the throttle to the stop. The nose of the old tinnie shoots up to an angle of attack resembling the start of an aileron roll and stays there while the motor howls away and the tinnie plows along at a fabulous five knots. Let go of Kaz for a minute and ask her to go up the front of the boat and hang on. Voila, as Kaz moves the CofG forward, the nose comes down, the hull starts to plane instead of plowing, and all of a sudden you're "on the step" and belting along at twenty knots with the same power setting that was only producing five knots a minute ago. The concept can be applied also to flying. Pour on full power and set climb attitude in the old CT44 Mk33. The nose sits up in the air, the airspeed stays at some pre-defined "climb speed" and you convert fuel into noise, heat and height. Once you've reached your chosen altitude you can level out a number of ways. 1) Reduce power to cruise, lower the nose, and watch the airspeed gradually creep up towards normal cruise for that power setting. Keep re=trimming for the next two minutes as the speed increases. 2) Leave climb power set, lower the nose to what you already know is close to the normal cruise attitude, wait a few seconds while the aircraft accelerates, then reduce power once you see normal cruise airspeed. Hold attitude for a couple of seconds then trim, probably only once. 3) Overshoot desired altitude slightly, reduce power at the same time as you lower the nose, and dive down on to desired altitude. Trim. Methods 2 & 3 are what people refer to as "getting on the step". While it may be a nicer/better/faster way to level off, I don't know whether it will actually get a higher cruise speed for the same throttle setting. Some of the old-timers believed it did, and they have many more hours behind the stick than me. I tend to use and teach method two because it just seems to me to be a neat and logical way of leveling out. Cheers, Bruce

Have a look at the nosewheel. That will give you an idea about the rudder deflection in use. Bruce

Maynard, Have a look on this site for a lot of Rotax info. http://www.800-airwolf.com/articles.htm Cheers, Bruce

From the matronics forum. Not a jabiru airframe, but sheds some light on the uneven inlet distribution none the less. Bruce Oct 23 2005 Cooling improvements on the Zenith 601HDS w/Jabiru 3300 During my first few hours of flight, I experienced elevated cylinder head temperatures on my Zenith 601HDS with Jabiru 3300A engine. Also had issues with Exhaust Gas Temperature imbalance at full throttle. The following is a summary of changes made to improve the situation. This really just builds on the recommendations of Jabiru and Zenith to provide plenty of cooling for the 6 cylinder engine. I would like to thank Jeff Small, Fred Hulen, Stan Challgren as well as Pete Krotje at US Jabiru and Andy Sylvester at Sun Coast for their contributions. As a place to start, US Jabiru provides some good cooling suggestions at their website: My aircraft has the following modifications: 1) Fuel Economy Carb Kit as supplied by Jabiru. 2) Gull wing baffles between cylinders as recommended by Jabiru 3) Full deflectors angled down between the spark plugs of cylinder #5 & #6 as recommended by Jabiru. 4) Smaller deflectors angled down between the spark plugs of #3 & #4. These middle cylinder deflectors usually need some tuning. Would suggest starting with 3/4" tall. On #3, I stayed at 3/4", on #4 ended up trimming down to 1/2". 5) The inlet to the ram air ducts has a gap between the duct and the cylinders at the bottom. This allows air to escape downward without doing any useful work. I added some .025" aluminum plates that butt up against cylinder's #1 & #2 to prevent this from happening. To reduce the over cooling of the front two cylinders and force more air upward to the rear cylinders, I angled the material upward about an 2-3??. The exact height needs to be determined by trial end error. The new XL cowl has openings that are quite small and located high on the cylinders. My modification attempts to duplicate the XL cowl openings and seems to work quite well. At the onset, this change appears to be counter-intuitive. Just keep it mind, the goal is to get as much use out of every air molecule as possible! 6) Small baffles mounted between valve tappet covers. This prevents more air from escaping without doing any useful work. 7) There is a temptation to add an L angle to the bottom rear of each ram duct. I tried this change and it elevated my temps rather than reducing them. 8) The oil cooler inlet is keep quite small to allow more air to find it's way through the cylinders. I ended up with about a 1.75" x 4.00" opening. The Jabiru website provides a good discussion on this. I tried a much bigger opening as can be seen in the picture and it provided very little benefit. 9) Don't forget to keep your oil level midway between the Full and Add mark. Jabiru indicates that overfilling can cause high oil temps. 10) My #1 cylinder was running much cooler than the #2 cylinder with identical intake openings. I rotated the bottom of the carb 5-10 degrees towards #1 and that took care of it. The main jet feeds the carb at the bottom so if the carb is tilted, it can direct more fuel towards one bank of cylinders than the other. At full throttle, EGT's from left to right bank were 150 F different. I suspected that air entering the carb through the 90 degree intake elbow was piling up on the outside of the curve. I installed a vertical divider in the elbow to keep left side air separated from the right side air. This worked beautifully. My EGT's are now balanced within roughly 50 F at all throttle settings including WOT. The divider was fabricated out of a piece of 6061T6 aluminum - 5.25" x 3" x .016". The upper and lower edges were rolled around a 1/16" cable to add stiffness and prevent cutting of the rubber elbow. Finished height is just slightly over 2.25 inches so it fits snuggly within the elbow. After rolling the edges, the part was bent 90 degrees to fit the elbow contour by wrapping around a 2" diameter plastic pipe. After it springs back, you end up with a 2" bend radius which is equivalent to the center radius of the elbow. Once the part is finished, the cable can be removed (prevents a potential corrosion issue). The rubber elbow is quite pliable in the free state, so the flow divider installs quite easily. After installation, the divider is trapped pretty well in all directions. With the Aid of my Engine Information System from Grand Rapids Technology, I was able to monitor my progress for each Cylinder Head Temperature: I now have the following readings at 60 F ambient temperature (my engine has 28 hours TT, so temps have fallen after break-in): ------------------------------------------------------------------------------- RPM IAS CHT1 CHT2 CHT3 CHT4 CHT5 CHT6 EGT5 EGT6 ------------------------------------------------------------------------------------- 2600 110 247 228 259 247 272 245 1465 1423 2700 120 242 221 253 239 265 240 1486 1451 2800 125 242 226 252 242 265 244 1512 1498 2900 130 253 246 260 260 268 262 1482 1538 WOT 138 288 293 293 298 301 297 1463 1482 ------------------------------------------------------------------------------- This was a quickie test and temps/speeds were not totally stabilized. Oil temps varied from 200-230F depending on Throttle setting. This is an area where a NACA inlet could improve Oil Cooler efficiency. The new XL cowl incorporates one of these. The Flight Test was run at 3500 ft MSL and an ambient of 60F. Wheel pants and gear fairings are installed with an otherwise stock airframe. The Jabiru is running very nice. I'm happy with the installation, power and smoothness after getting through these initial teething problems. Fuel burn at lower cruise settings is estimated at a miserly 4 gph. With the fat wing, I suspect fuel burn will go way up at the higher cruise speeds. Chuck Long Zodiac 601HDS N601LE, 28 hr TT

Darren, The Airforce Museum at Wigram (Christchurch suburb, not far from the airport) is a good visit. Nice cafe for Emma to sit in reading books while your playing aeroplanes. The do free tours through their workshop area too, which is interesting. Once you've finished with the museum (allow at least half a day) its time for some notplanes. Take Emma down to a place called Akaroa. It's about an hour and a bit drive from Christchurch. Absolutely beautiful place. Do a harbour tour (or swim with the dolphins), have a nice feed, then go to the pictures. Great little theatre holds about 30 people max, in big armchair style seats, and the owners will supply bottles of wine, food and expresso coffee for you to take into the movie. Then back to the motel/B&B where I'm sure you'll find it's a lucky place.;) Cheers, Bruce

Matt, Nice to see you exploring the envelope. Yours and the CT4, and thanks for letting the rest of us peek over your shoulder. If you have trouble getting to sleep with your inner ear still doing loops, the following link should assist. Once you'ved memorised all the theory, you'll be able to answer the proverbial posed by Professor Julius Sumner Miller (Why is is so??) as well as demonstrate. I'm sure Kaz is trembling with anticipation! http://www.flightlab.net/download.html Cheers, Bruce

Shouldn't full flap max speed be the top of the white arc? Bruce

Chris, I believe Ken Garland from AeroV (manufacturer of the Vampire) is acting as an agent for HKS. 02 4257 7053 Bruce

Troy, The Instructor's too busy looking out the front window (or side window the way some guys fly their final approach) at whatever obstacle the student's trying to fly them into to worry about a little thing like an oil pressure gauge. Well dressed instructor --> Student de-brief --> :hittinghead:

It WAS broken, so I emailed Jabiru and they fixed it so we can all get our "info fix".

Picture13.jpg, third row, third pic, is Lukla in Nepal, instigated by the late Sir Hillary. Flew in there in a chopper whilst it was still gravel. There was a crashed twin otter you flew over on short final.

John, Re-arrange your flights. It's one of the best airshows you'll ever see if you like WWI and WWII vintage aircraft, not to mention spine tingling aerobatics by people like Jurgis Kairys. This will be my third time, and my wife even lasts for at least two days, when two hours is her more normal "are we there yet?" limit. Bruce.

The Jab motors use coils, powered and triggered by the flywheel (Just like the old Victa lawnmower). That's why you have to spin them over at about 300 rpm to generate a spark. Rotaxes similar story, which is why this wouldn't work to well with a Jab motor. [ATTACH]4657.vB[/ATTACH] :;)1: Bruce

Paul, A partial blockage in the pitot (dynamic) will do what you describe. Have you also checked for any leaks from the pitot tube right through to the ASI. I think a leak would also cause those symptoms. ie: the faster you go the more air pressure therefore more leakage therefore more percentage drop in dynamic pressure.

3 x LSA55's online, 1 with a GPS No Tecnam

Hi Motzartmerv, I currently instruct on LSA55 Jabiru's, and have about 25 hours in the Tecnam P92 (high wing) from the right hand seat. Also done a few hours in Jab 160/170/230. From my perspective the Tecnam is a much easier aircraft to fly and particularly to land. The controls in the Tecnam are lighter and better balanced than the Jabs, and the dual sticks make it easier to instruct. The Tecnam also approaches 5-10 knots slower than the Jabs which makes it easier for low time pilots. Visibility from the Tecnam is a lot better than the Jabirus. Cruise speed is much the same as the 4 cylinder Jabirus with a slightly higher fuel burn. I also found getting in and out of the Tecnam easier. All in all the Tecnam is a more refined design, but unfortunately dearer to buy, and spare parts are much dearer than Jabiru. I suspect that what looks like touchiness in the video is just strong and gusty winds. Cheers, Bruce

Graham, Joining crosswind is done as before, except that you fly across the strip (the crosswind leg) between the midpoint of the strip and the end of the strip, not directly over the end of the strip as we used to do. The recommended method to join downwind is at 45 degrees, joining at mid downwind point. Have a look here for all the info. http://www.dotars.gov.au/aviation/airspace_reform/nasys/training.aspx Bruce

Merv the composer, Props make a big difference on the Jabs, or most aircraft for that matter. The J160 tends to suffer from rather poor climb compared to the older LSA55 model due to having extra weight but the same engine. The aircraft owner may well have fitted a "climb" prop rather than a "cruise" prop. ie: The prop is a finer pitch, so it's like driving your car in fourth gear instead of overdrive. Better acceleration, but more revs and thus fuel burn for the same speed.

From the Mercury picture (last post) it appears to be a trike.

Sorry Mike, Guess you'll have to grade me "Unsatisfactory" I didn't do the full Mountain Flying course that Fly Wanaka offer, but based on the abridged "taster" I did do, it would be money very well spent. Just the couple of hours I did were enough to pick up quite a few valuable tips, and instill a healthy respect for the conditions you can encounter flying around in and around mountains and valleys. Even when sitting there looking sunny, clear and peaceful, the mountains can still bite! I think I have some shots tucked away somewhere, will see if I can dig them out. Bruce.

John, Drop a line to flywanaka.co.nz. I did a few hours af mountain flying with Wayne Allanson, their CFI last year in a Tecnam Bravo fitted with a variable pitch prop. Wayne claimed that he could get a reliable 120 knots out of it on a cross country by getting "up on the step" and increasing the propellor pitch. Cheers, Bruce

Geez Darren, you got ripped off. I only paid one dollar and 13 cents!

Hi Troy, Never fear, your first flight was in an historical aircraft! The LSA55 Jab was the start of a long line of Jabiru aircraft, and is a factory built model so eligible for flight training. The J160 came along later, and has the same engine as the 55, but a wider, taller body. The 160 still does the same speed as a 55 even though it's bigger and heavier, but doesn't climb quite so well.