Area-51

The previous owner being overly cautious and everything by the book by nature, motor would of been using what ever Rotax recommended, prob SHELL AERO SPORT+ 4 out of the 8 lifters were not rotating as required; end of story. The other 4 lifters are as good as new.

Modding out the crankcase to retain roller lifters would be a good update providing the camshaft's valve timing still functions correctly afterward. Certain that would come with other failure moments. Really not convinced by the 9XX lobe profile either, it's extremely acute with very little duration at the top, but the engines fly pretty reliably and that's what matters most to me.

I don't expect to find the camshaft at fault here, but i could be wrong. 50% faulty lobe grind in a production facility the size of Rotax just doesn't make sense, but I could be wrong again. Will try another set of fresh lifters first and see if they spin as in your video.

They are definitely rotating! Are the lifters standard rate leak down or fast rate? Any EDM port to the lobe face? What brand lifter are they?

This is all correct, however the 9XX cam lobes do not appear to be offset to the lifter, but they may very well be machined with a slight taper on the rear of the lobe; have not had one out and dial gauged yet to verify. Have read in a lot of auto performance forums engineering shops, after trialing all the brands just use Johnson Michigan produced lifters. The latest hydraulic lifters used in the 915is look to be totally flat bottomed rather than convex. Latest lifter technology by COMP uses application of a diamond shield friction coating on the lobe contact face. And it seems to be holding up in the field.

Have been trawling through various forums. Apparently Hylift Johnson, Michigan are produced in Michigan from imported Taiwanese manufactured blanks. Johnson Lifters, Michigan (in the rotax) are wholly manufactured on site in Michigan.

How many hours since fitted or removed and inspected?

Inlet exhaust, both showing similar results on four of the eight.

No, i did not answer my question well enough. Rotax have changed the part number for both the lifter and lifter set a lot prior to 2008, and a few times since. Today I tore down an old 912 and it did not have Johnson lifters in it, and they still looked ok after 2000hrs use, where as the Johnsons are heading to the bin at just 100hrs. (Maybe they were a bad batch). Does anyone have any info on this?

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Its ok, found it, Johnson HT-900; Laser etched on the lifter 351 Windsor and 4.1 straight 6, thought they looked familiar. Guess Rotax knew where all the real power always comes from 😄

Does anybody know who manufactures and supplies Rotax lifters for the 9XX engines? Just need an answer about manufacturers and suppliers, thanks.

I too have many decades dealing with precision mechanical components and criteria and was equally in absolute disbelief when first being introduced to pellet bags some eight years ago; never ever heard of them before that. And the whole concept just sounds physically impossible; but it works! The balance master brand use mercury as the moving mass media; lesser quality brands use granulated lead shot which does not provide as precise result. If your aircraft is already kitted out it will display what looks like a 5mm black ring directly behind your prop hub assembly.

Centrifugal force keeps the bag hard up against the inner wall of the tyre. Because its a bag of pellets it will roll around and reposition itself again and flatten out, so if its a front wheel driven setup wheel spinning or the front wheels lockup under brakes then the steering will shudder again momentarily. The bags are used to mitigate inconsistent wear of the tyres during service such as flat spots etc.

Totally the opposite; the bag goes to where its required. The steering vibrates like hell momentarily from the standing start then once the bag places itself it stays there until the wheel comes to a full stop, and the process repeats again. There is no other pre-balancing of the rims applied; the bag is the method used for dynamic balancing.

Da 🥳 Это круто, мы живем, мы мечтаем, мы авиаторы !!! 🥳

Correct. The balance master adjusts for any fine deviation and inconsistency of both the static and dynamic balance. If you spend time getting the static balance right the balance master style disc will take care of the rest on each startup. The same concept is used on larger units for automotive car and truck wheels and tail shafts, and for motor racing a small bag of lead shot is placed inside the tire to move around freely to where the balancing is required during driving.

I have one already fitted on the 912 prop flange; they work great. With the carburettors sync'd it runs as smooth as a button at all rpm ranges. Bought another two for the rainy day shelf. They are cheaper to buy in Spain than the USA.

Screw all this, i'm relocating to an undisclosed pacific island atol with my freshly developed 125hp plutonium pico reactor powered stol lightwing and box of iced vovo's.

I'm just not excited. I used to be excited, but just can't seem to find the inspiration to get excited here. We still have not yet seen the 115hp 250cc multi cylinder honda enya aerosport motor come out of japan. And we are all still eagerly awaiting the 225hp single cylinder side valve DangDeng ductile iron motor to ship from north korea. Iran are refusing to release any of their rebadged stolen rotax rebirth units due to sanctions. And the soviets flatly continue to refuse to reconsider everything under 12000hp as an insult to aviation. Just not excited. Going out to the shed to listen to 2GB and play with the victa again.

Its just a very very tragic situation, and clearly something somewhere went very wrong. And the speculation will abound. I just find it extraordinary that two aircraft can start their roll on two seperate runways without the other knowing. Its almost saying one or both of the aircraft had the radio muted or completely tuned off. Or as someone else pointed out confusion from surrounding off field radio calls maybe played a part. Surely somebody working in a nearby hangar was listening to the ctaf

That's all totally correct; poor planning can lead to a poor outcome. And poor design can also lead to a poor outcome, hence the use of a header tank and low level warning. Why? Because the LSA manufacturer in this case refuses to acknowledge and rectify a known issue that results in an EFATO 15-20min after takeoff with full tanks. Why? Because Rotax require a choked return line to mitigate vapour lock and the AC manufacturer in all their wisdom has sent the return line back to only one wing tank, and switching to the opposite wing tank will provide the pilot an EFATO within 15-20 minutes, or less depending on fuel volume being less than max. Why? Because the return line pumps all the opposite tank's contents out through the fuel vent of an already full fuel tank.. So what? Well if you've been flying on the opposite tank for 10-15minutes, switch tanks and fly some more before landing, then take off on both tanks and switch to the opposite tank thinking you have plenty fuel (because you have correctly run your inflight fuel logs haven't you), well you are at maybe 500', or less, departing and get an EFATO? Hope the training kicks in but better to identify and fix the problem long before it gets to that; three forced landings due to unexplainable fuel starvation were trying to tell the pilot something was not right with the AC. The idiot light is not there to deal with poor planning. The idiot light is there to notify the pilot that there is a situational issue with the planned fuel reserve and that an unforeseen leak down of the fuel system has occurred. This is why a low level warning indicator and a header tank with 20min useable reserve is a good idea.

That's not true. Jab's can fly through buildings. 🧙🏽‍♂️

"Such projects are geared toward helping the Pentagon prepare for potential conflicts in the Indo-Pacific region – where vast swaths of open ocean and small, lightly developed islands present substantial challenges to military planners." - WTF? 🤦🏻‍♂️ These people are just pathologically insane.