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Bruce Robbins

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Everything posted by Bruce Robbins

  1. Hi Mike, I've only got a few hundred hours in various 172 sized GA (General Aviation) aircraft, but many hundreds in the various Jabiru models. All the Jabirus have shorter travel on the rudder pedals than most GA aircraft and a nosewheel that is closer to the mainwheels. The pedals are also physically shorter, so combine the short pedals, shorter pedal travel for a given nosewheel movement, and closer coupling of mains to nosewheel and you end up with much more sensitive steering on the ground. The shorter pedals and throws also give a "stiffer" pedal feel. (particularly on the larger models like the J200/400). I think that once you re-program your feet to a new tactile feedback loop, you will find the J400 easy to handle on takeoff. Remember to think rudder pedal pressure, not rudder pedal movement. Having said that, I would use some different takeoff techniques. The Jabs are much more sensitive and responsive to nosewheel steering on the ground, and most people get into trouble because they overcontrol and end up in a PIO. By using full forward trim you're loading up the nosewheel even more, and delaying the changeover from nosewheel to rudder steering. So: Method 1) Set the trim Neutral. Lift the nose wheel just off the ground once it is happy to do so, and then let the aircraft fly it self off in that attitude (which should be pretty much your initial climb attitude). The speed to lift the nosewheel will vary depending on the aircraft weight and CG. I have only flown J230s in the J200/400/230/430 series, so cannot comment specifically on the J400, but in some of the 230s I've flown with full fuel and only a light pilot, the nosewheel almost jumps off the ground by 30 kts and can require some forward stick. The response to rudder inputs is "softer" with the nosewheel in the air and avoids that darting from side to side you get if you're overcontrolling slightly. Method 2) Set trim neutral, leave the stick neutral and let the nose wheel stay on the ground till you get to 50-55 kts or so (depends again on the weight). Rotate positively and the aircraft should lift straight off. During the ground roll be sensitive with the rudder pedals, and keep thinking pressure, not movement. If you develop a bit of a side to side swerve, put pressure on BOTH pedals till it stops, then gentle corrections again to regain your desired track. Regards, Bruce btw: There are a few guys on this forum who fly the J400s, so you should get some more model specific advise soon.
  2. Hi Qwerty, By the sound of it, you're a normal human, not a computer geek, so I'd suggest the following. 1) Get a large capacity USB Flash Drive (also known as Thumb Drives or Memory Sticks). Capacity depends on how much data you need to move. 4GB will be about $20, 16 GB about $55. Plug the Flash Drive into a spare USB port and simply Drag and Drop all the files you want off the old computer onto the Flash Drive. Reverse the operation on the new laptop. Alternatively, buy an external USB Disk Drive ($100 will get about 250GB). Use this to do the data transfer, then keep it and USE it for doing your backups. Specially all those irreplaceable photos. 2) Don't even think about doing this unless you have lots of time, patience and a friendly IT expert to call in. You'll need to have a kosher copy of XP on a bootable CD, and ALL the relevant drivers for your new laptop, otherwise half the features like sound, screen resolution, inbuilt modems, and CD/DVD burning won't work properly. 3) AVG Free and Avast Home (free) are both good. I have found Avast a bit better at handling viruses, and less of a drain on system performance than AVG. Avast has to be registered with an email address every twelve months while AVG doesn't. Download FREE antivirus software - avast! Home Edition Regards, Bruce (25 years in IT)
  3. Peter, hard to tell from the photo, but the fibreglass sheathing on the prop seems to be starting to de-laminate. I'd get it looked at asap by someone who knows wooden props. If it is de-laminating or coming away from the timber, it can get worse very quickly in the air, and I guarantee it will get your attention. Cheers, Bruce
  4. Under the new Drug and Alcohol testing regime already quoted, the permissable level of alcohol in the blood is .002%. Under the regulations, "8 hours bottle to throttle" CAR 1988 (Civil Aviation Regulations) (3)A person shall not act as, or perform any duties or functions preparatory to acting as, a member of the operating crew of an aircraft if the person has, during the period of 8 hours immediately preceding the departure of the aircraft consumed any alcoholic liquor. Penalty: 50 penalty units. So the exam is correct. Both .002% and 8 hours apply.
  5. Carby ice forms when the air tempfalls low enough to freeze the water vapour in the air. First you need the water. Dry air - no ice, humid air - potential ice. The temp drop occurs because there is a pressure drop as the air passes through the carby. The pressure drops because the air speeds up going through the restriction in the carby. The smaller the throttle opening the greater the restriction, the faster the air flow, thus the greater temp drop. Carbies are thus more susceptible at low throttle openings. Sometimes the icing occurs while the throttle is low, but doesn't become apparent till you have re-applied power and started climbing away. The ice in the throttle then starts warming up and breaking off. The resultant rough running or misfire sure gets your attention!
  6. The Victorian Bushfire Appeal 2009 [imgalign=right]http://www.theaviatorlounge.com.au/images/bushfire/bushfire01.jpg[/imgalign]On Friday 27th February, 2009, The Illawarra Flyers are using their weekly Friday afternoon BBQ to raise funds for the Australian Red Cross Victorian Bushfire Appeal. Dick Smith has been invited to attend (and will arrive in style in his Augusta helicopter) to give his views on the future for sport and general aviation in Australia. During the evening we will be conducting an auction of items donated by local businesses and individuals. The items range from bottles of wine to joy flights in the Historical Aircraft Restoration Society's Lockheed Constellation, dinner vouchers to aviation memorabillia. Any-one wishing to support the auction and unable to attend, can place a bid at any time with our auctioneer for the night, Ray Peterson, either by phone on 0417 211 092 or by an email to [email protected]. Ray is already accepting bids. There is complete truth in the rumour that Ray is totally corruptible and will accept the highest bid on any item to ensure that you secure the one you want! We urge you to have a look at the magnificent list of donated items at www.theaviatorlounge.com.au/bushfire/index.html The Illawarra Flyers are a group of aircraft owners, pilots, aviation enthusiasts, businesses and employees based at the Illawarra Regional Airport. We are charging ourselves $20 per head to attend the night and ALL proceeds go straight to the Red Cross. Thanks, Bruce ps: Sorry for the saturation cover, but we figure it's a good cause.
  7. Pudestcon, It's the Airborne Aviation spreadsheet. See the details in post #5 above.
  8. Hi John, I've used this spreadsheet for several years. It's great. Simple and quick. When I first got it I used a password cracker to look at the formulae with a view to making a few "tweaks". Took one look and closed the bonnet again very quickly. They are extremely complex. You will find that if you simply enter the data where specified the sheet works out a perfect flight plan for you. In the middle of the sheet are two boxes for fuel. Enter the amount of fuel you have into those boxes (marked Left and Right tanks) and the endurance will be calculated based on the fuel burn you entered into the Aircraft Reference Card. If you only have one tank, just use one side. Regards, Bruce
  9. Captain Geoff, This is the latest info I have. Regards, Bruce Robbins (Illawarra Recreational Flight Centre) =========================== Additional operational information regarding Wings Over Illawarra Sunday 22FEB09 at YWOL This information will be published in a NOTAM closer to the day, but is being distributed now to help with planning arrival times for anyone out of the area planning to fly in. Main items to be aware of is that runway 08/26 is closed all day. Western end of 08/26 only available to light aircraft (in particular taildrag) in strong cross wind, with pilot's responsibility to maintain communications and maintain safe separation. Runway 16/34 operational with closure to GA/light aircraft 1000-1050, 1210-1245, and 1420-1500 local time. These closure times are to allow for Roulettes, r/c model aircraft and Skydive the Beach displays. All arrivals by 0930 where possible, but no later than 0945 to avoid first closure period. If arriving from further afield, please be aware of closure times and plan to avoid these. PLease distribute this information to others planning to fly in. Thanks for your consideration Phil Ayrton Secretary SAAA Chapter 4 =================================
  10. If you gents are having trouble sleeping over all this scientific discussion, please download the 10mb file located at the bottom of this page. It contains very detailed and well written descriptions of what is happening to the aircraft during all phases of flight. http://flightlab.net/Flightlab.net/Download_Course_Notes.html There are some nice videos on the site also, showing some of the things discussed in the notes. I have found the notes explain very nicely many of the behaviours discussed above, including how and why an aircraft rolls into or out of a turn when stalling. As some-one famous once said "Things are not always as they seem". Happy bedtime reading, Bruce
  11. Thumper, This site may be of interest. Potomac Books - Amelia: A Life of the Aviation Legend Bruce
  12. Here's one from New Zealand. Touchdown on the first section which slopes uphill, then hang a right hand turn at the bald patch soon after, and finish the rollout slightly downhill.[ATTACH]6806.vB[/ATTACH]
  13. Last time I took some friends for a local sightseeing trip in a rented Cessna 182, I got a severe fright after 45 minutes or so. Checked the fuel guages for the first time since take-off, after having been questioned/pestered non stop about the fabulous sights passing by below. .............Whoah, whats happened to all the fuel out of the left tank!! Needle seems to be bouncing on empty!! ........Quick change from "Both" to "Right", listen very intently to the engine noise for the next five minutes, and then enjoy the afterglow of adrenaline induced thump, thump, thump noises in the chest cavity slowly subsiding. For a bit of light reading on drawing fuel from high wing wing tanks (no I'm not stuttering) try this ........ http://www.moonflight.org/Documents/Fflow.pdf Cheers, Bruce
  14. Yep, It's caled a Furio. http://www.falcomposite.com/ Seriously though Disperse, it's not as simple as just substituting carbon fibre rovings and or cloth for timber. The two materials have completely different characterisics.
  15. Tony, Interesting point, and one I've not thought much about. If what you've experienced is widespread behaviour in reflex flap designs then you've made a number of very valid points to incorporate into operating such aircraft. Do you know if there are any aerodynamic "fixes" like stall strips, boundary layer trips, wing fences, vortex generators etc etc that may introduce some feel back into the stall? Bruce
  16. Mathew, They both do the job. The one's without a slide (Jepessen CR series) are much easier to take with you in the cockpit. If you're young and still blessed with good eyesight, then the CR2 fits nicely in your shirt pocket. If not, then the CR3 is bigger and easier to read. I agree with the others. Don't waste any money on the electronic ones (and yes, I did!). My CR3 goes on every nav flight. The $150 ASA electronic paperweight is still in its 6 year old box. Bruce
  17. Hi Ian, Like I said, I'm being a little pedantic here so don't take me too seriously. In teaching someone to fly, the actual detailed mechanics of a stall are not so important as learning to recognise when you are getting close to a stall, what might happen if you do, and how to avoid being bitten. Unfortunately people are still killing themselves by stalling in from low altitude, and it should be totally avoidable. Anyway, back to pedantry. I agree that Reynolds number, planform, slots, slats etc etc are usually out of our control in the aircraft we typically fly, which is why I said before "they are not usually relevant". The one that is however is camber change, and so flaps (and power settings) can change the stall behaviour significantly. As an example, go for a fly in one of the LSA55 Jabs and try some stalls. No flap simple stall - benign as anything, basically not really stallable. Full flap simple stall - bit more interesting. Full flap simple stall with 2400 rpm - sudden, sharp wing drop, large nose down pitch. Do that one turning final and you won't survive. As I intimated before, the average student probably doesn't really need to know why and how the plane reacts differently, just that it does. Have a look at this diagram which shows Cl plotted against AoA and you can see what I mean by the stalling angle (of the same airfoil section) decreasing with flap. [ATTACH]5935.vB[/ATTACH] Note how the peak Cl (stalling angle) is shifting left and up. Regards, Bruce
  18. 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
  19. 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
  20. Have a look at the nosewheel. That will give you an idea about the rudder deflection in use. Bruce
  21. Maynard, Have a look on this site for a lot of Rotax info. http://www.800-airwolf.com/articles.htm Cheers, Bruce
  22. 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
  23. 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
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