RFguy

I've never seen any stone damage in the very low mounted Jabiru oil cooler. Do propellors (on GA) 'suck' stones in from in front of them , or do they stir up the stones beneath them ? As I commented elsewhere, its all about whether you can acheive an air pressure differential across the radiator, which is VERY cheaply assessed with a clear bit of tube and some water. if its frontal facing, you can estimate the frontal pressure using the formula for inches of water = ((airspeed knots * airspeed knots ) * 25 ) / 40000 Then have a tube from behind the radiator to static . performance will be compromised by how much air is getting into the cowl (if the radiator exit is in the cowling) If the radiator is ducted, like many GA, have the tube across both sides of the radiator.

Hi Marty. Have you had time to read through the 912 and 914 (has more useful info) rotax installation manuals ? there is lots of meat in them, Now, what i would be looking for is : can you satisfy / provide the required pressure differential across the cooler? That's the $64 question. The thin coolers like std rotax - well there is very much ambient temp and heat input variables, but they can work for typical 912 usage with as little as 2.5" of water , but the deep coolers like #800075 , needs about 5 inches of water for typical loads. Slowish aircraft like the Archer, (100 kias cruise) they have an # 800075 aeroclassics cooler ( a deep cooler that needs lots of differential pressure to work) - it is mounted on some 4" scat from the nose of the plane and tghe cooler, with the duct mounted at the firewall. that cooler is same as factory Jabiru used for 3300. so really, it comes down to if you can make pressure across the cooler. poke a tube with water meas into the shroud at the cooler to find out ... Dont forget you need to duct air over the cylinders (per Rotax) where possible. otherwise a ton of extra heat load goes into the water system usually from the rear cylinder not getting the blast.

Nice comment Nev : "If the plane is already loaded say in a turn or a dive recovery the effect of a gust will compound the air loads you already have. " yes, very true. In the simulator, I've overdone the airframe a few times during (radical) upset recovery in IMC....I'll calculate at what height (minimum) a vertical dive and consumate airspeed is unrecoverable (IE insufficient height to pull the aircraft out of the dive without damaging the airframe) .

Dynamic Gust Loads in https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_25_341-1.pdf Required reading for everyone everyone to read sections 5 and 6 from that AC. (dont need to read the lot)

not quite , It is the speed beyond where the the lift produced can damage the aircraft. example: your aircraft is 1250 lbs, and rated for 2G. and.. that the maximum lift AoA is 25 degrees. and it produces 2500 lbs of lift at 56 kts at 25 deg AoA. now, say you are flying along at 5 deg AoA at 56 kts, and the wing is producing 1250 lbs = IE same as your weight, S&L flight. then you yank the control stick back and produce 25 deg of AoA, -- now yoru airspeed is still 56 knots, and now the wing is producing 2500lbs, which is 2x the 1250 lbs weight, - and thus 2G of force - this is the maximum you can tolerate. if you yank the stick back and push the aircraft through the maximum lift AoA, and BEYOND , then the wing goes down the other side of the lift curve in a stall. no bother. So, you survived, the wings didnt fall off . But if you'd been flying S&L at 80 kts, and you yank the control stick back to produce 25 deg AoA, now the wing produces ( 80/56 )squared = 2.04 x as much lift as at 56 kts, now you have 5000 lbs of lift, or 4G. your wings fall off. for a GUST and TURBULANCE - and this is what I didnt first explain - this is for a fictional gust of , if the aircraft gets belted up by a gust, or the pilot applies some control input in resposne, IE hit by a gust causing the aircraft attitude to change its AoA - the aircraft goes from flying S&L to perhaps being steeply pitched up, high AOA- then below Va, this will result in lift being below the maximum that the airframe can tolerate. If it gets hit by a gust etc and the aircraft gets pushed HIGHER than its maximum lift AoA, no bother- the wing will stall - IE beyond the maximum angle on the lift curve - IE putting an upper bound on the lift produced. The same limit can occur if the wind gust vector is such that it produces a high AoA. Like, a gust from under forward of your nose. See section on Dynamic Gust Loads in https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_25_341-1.pdf

No. google "FAA definition of Va". FAA defines this as : the airspeed at which the airplane, subject to a sudden control input , or , gust will stall rather than exceeding the design structural limitation / maximum load limit. And more weight on board means higher stall speeds (as usual) . If you fly faster, the wing can produce more lift. IE for Va = 80 kts.....you are flying along at 70 kts and yank the column back to maximum AoA. below Va, the wings dont fall off. you are flying along at 100 kts, and yank the column back to maximum AoA , the wings produce a sh1t ton more lift (2.04x precisely) , you exceed the structural limitation of the aircraft, the wings fall off. The relationship with flying in turb is that you are hit by a gust at some angle which emulates a higher AoA and hence instantaneous lift. bad. See section on Dynamic Gust Loads in https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_25_341-1.pdf

C210 crash : Well, the weather radar/ time/ location of crash has good correlation. Not sure why the pilot did not fly around the storm, if indeed that was the cause. Always slow down to Vmaneuvering in turbulence ! It might be slower than you think if the aircraft is low in weight compared to max weight. According to the (pressurized) P210N POH : (and same in a T(urbo)210N) empty weight abotu 2200, so 210 litres, 2 pax and some luggage and tie downs etc probably 2950 lbs - IE around 111 kts

So, I see Justin has some coarse finned heads, they might be good. there are a few from time to time as you know on jab parts facebook. another option is ask on jabcamit forum. I have some but they've got plenty of recession . Need milling down 0.9mm (to take the recession out to get square again ) and dropping copper shims in (I have the shims- got them water jet cut) these guys have the new heads - recommended : Philip Gibbs Shadow Lite CC t/a Jabiru Aircraft SA CAA AMO L14 & 909 George Airport, Aviation Area, Hangar 22, National Rd, George, Western Cape, South Africa PO Box 2540, George, 6530, South Africa Ph: +27 44 - 8769991 / 2 Fax: +27 44 - 8769993 Email: [email protected] <mailto:[email protected]> Website: www.jabiru.co.za <http://www.jabiru.co.za/> Office Hours: Mon-Thurs 08h00 - 16h45 Friday 08h00 - 15h45 Click on this link for a view into our factory: https://youtu.be/vPYUwuFTKSM

flat top pistons were still used up to at least3300#2575. (mid gen 3) the springs in jabs are weak. I went right through that investigation, and it is elsewhere on the site- jab valve springs are about 1/3 the tension that those lifters are usually used with. Double springs are approx same overall tension as singles. New head. simple fix. you might replace the rocker bushes while you are at it. (small arbor press required) - watch out for slithers of the material being extruded during the extraction and insertion)..

time for a new head. Jabiru South Africa. AUD1250 I think

Looks like quite alot of recession there- or is that a high crust ? Alot of recession would indicate long term overheating. remember, once they get soft, essentially over tempered, its all over even if you keep the temperatures down....

I think the "there is no point unless it makes a 5 knot difference" statement is not the right way to look at it. Many 5 knot gains come from numerous 1 knot gains all put together.

yes, grounds carry return currents. because the ground wire of your speaker carries significant current, if it shared a ground wire with the microphone, there might be enough voltage drop in the (common) ground wire , and inject voltage into the microphone circuit, and you could get feedback. happy to do a diagram... so, where possible, bring the mic grounds and the speaker grounds back separately to these pins.

Hi Neil- good info - yeah- SKyecho should see a 200W TSO Mode S about 30nm away, if everything is goign for you ***However for terminals right above or right below - there is (usually) significantly less antenna sensitivity for a body mounted whip antenna above and below - compared to our on the horizon. probably reduces the immediate up and down range by 10x . which is rarely an issue.... once outside a 60 deg cone, you're probably less than a factor of 2 down on max range.

geez you lot.... doom... gloom battery wont catch fire if installed and operated correctly.

I would not expect a TSO receiver to pull in any better than a the Skyecho receiver - assuming they had the same antenna. That's unless the skyecho implementation was suboptimal, and I would have no reason to think that it is. The skyecho ( internal ) antenna is compromised to some degree because of housing, PCB location, internal airplane bits etc The TSO uses an external antenna but might be connected on a piece of lossy cable (but if the correct teflon orangey stuff is used, probably not) . On transmit though, the TSO device will usualyl be 200W, 10dB more than the skyecho into the known antenna, and likely to have at least 3x the range of the 20W unit. (for same antenna) Range from TX skyecho to an air services ADSB base station should be at least 20nm - the ADSB base station uses gain antennas (amongst other things) . all calcs assume optical line of site. -g.

on average, expect about 10nm line of site on transmit from a Skyecho to another Skyecho... Yep - a man's Mode S runs 200W pulse...and a good antenna.

Norm for canberra in winter. fog rolls in 15 min after sunrise and hangs around till 2pm.

Battery fire risk is extremely low if properly designed, derated, sourced and qualified. especially you are you willing to sacrifice 20% in capacity to have a battery that will never catch fire from a maximal capacitor/weight type. (LIFEPO4 versus Lithium Polymer). But Lithium batteries with new elecrodes, etc are much much better They get a bad rap from the bad old days, and all the sh1tbox batteries used in scooters etc which are often the factory seconds......

batteries are to electric as fuel is to ICE motor controller for electric is a carb/thottle body is to an ICE a brushless motor is to electric as the pistons and cylinders are to an ICE not sure where fuel vapourization, fuel contamination, fouled plugs, worn rings, burned valves, worn bearings and lobes, leaking gaskets, broken thru bolts, CO2 poisoning , selecting wrong tank, mixture controls, detonation, bad leads, faulty magnetos , intermittant starter solenoids not sure where they all fit in to electric, in analogy.

And quality of instructors, like all industries varies enormously. I've flown with about 4 instructors : There is teaching the basics, which any 25 yo flight instructor can do. And then there is teaching airmanship, something I have only felt well communicated by the older folk. glen

Most likely, the motor controller, a highly complex , specialized bit of electronics may have failed. Batteries DO NOT disconnect themselves from the load if they overheat- Well maybe some consumer POS you buy . There is temperature and balance awareness for the charging system, that's all. Best option is a 2nd motor controller, or a very well derated single controller that never gets hot. Or a 2nd motor and controller on single shaft.

Dont quite agree, but anyway that's fine. by the way, PULP has a higher vapour pressure. ... not lower, than 100LL, but I think that's what you meant. I have thought a bit more about my (wrong) use of the phrase "sort of surprises me because I would have thought that only 7:1 Lycos would tolerate the ULP quality issues. " ( with reference to suitability for 8.5:1 compression also for the MOGAS STC) But the STC relates to fuel of a particular standard. Then in practical terms, this means probably buying PULP in a drum where there are no quality issues compared to the variability of running automotive bowser ULP. IE if the PULP you are buying meets the STC standard, then its fine. Buy automotive ULP, and your mileage (and altitude! ) may vary. If 95RON PULP (just ) gets you over the line (min = 94 RON equiv) , then if using automotive bowser PULP, you'd be wise to give yourself some headroom I suspect by using only 98 PULP. Putting aside potential of adulteration of the fuel....

I'm in the process of buying an Archer. The 8.5:1 Lyco has a MOGAS STC, which sort of surprises me because I would have thought that only 7:1 Lycos would tolerate the ULP quality issues. So they must be tough......and 8.5:1 isnt all that high. The engine is originally factory specified for 91/96 MOGAS (~ 91AKI) which is something like (AUstralia) 94RON from memory (will check) but the heads do get hot. enemy #2 of course is the higher vapour pressure. but clearly, with STC issued, not seen as too much of a Vapor lock problem , as least evidently... low wing, aux fuel pumps . maybe in warmer weather if you do not use the fuel pumps on takeoff there is a low pressure in the lines == vapour bubble issue which could cause trouble at the wrong moment just after takeoff... Potential for trouble also at high DA.....It might be something I only use in winter..... . See my earlier posts of symptoms of vapour in the fuel lines- cycling fuel pressure over 20-200 seconds I'll dig up the STC and take a read to what was done. and if there is any specific placarding. And remember MOGAS does NOT mean 'automotive bowser dispensed'.....

The other thing is, in the ACT, there is a new rule that requires medical practitioners to (compulsory) advise the ACT motor vehicle regulator (vehicle license) , or CASA (air) if their patient has anything out of tolerance. IE the patient has no say in it. This has caused an exodus of ACT heavy vehicle licensed drivers apparently, and medical doctors dont like it either.