Timing Your Off-Field Landing<\/h4>\n
When it comes to flying any aircraft –\u00a0 particularly 2-stroke engine powered Ultralights<\/strong> – you can improve the odds that you will not experience an in-flight engine failure by altering the MTBF Continuum<\/strong>. MTBF <\/strong>( Mean Time Between Failure)<\/em><\/a> – is the concept that there is a predictable or estimable point in time when a machine or system (or any other object for that matter<\/em>) will fail during use. A hammer has an MTBF as does a computer hard drive. I have experienced the failure of 2 hammers in my life but seen many more hard drives “go South”. The soon arrival of the point of failure for a hammer is usually evident by visual inspection. Hard drives, on the other hand, give you little or no warning before they give up the ghost. In addition, they often provide the additional “negative bonus” of taking countless hours of your hard work to “hard drive heaven”. My experience in using them for the last 25+ years is that their advertised MTBF<\/strong> figures are pure fantasy<\/span> – absolute meaningless speculation.<\/p>\n I say all this because I had to make a decision at the end of the 2012 Flying Season<\/strong>. My Rotax 503 Engine<\/strong> had faithfully rotated the air screw of my MXL<\/strong> over the last 4 years providing me with 327 hours of flight<\/strong>. Without a doubt it has been the finest engine I have ever had the good fortune to own. Back in the 1980’s, when I flew my first<\/strong> <\/a>Quicksilver<\/a> (an MX)<\/strong>, engine failures were a constant and real occurrence. Over a few years of flying with the old Cuyuna<\/a> engines, I had the opportunity to land without power no less than 6 times.<\/p>\n My flying instructors taught me well before receiving my Private License<\/a> as a 17 year old. They would jerk the throttle at seemingly random moments and say “OK. Where are you going to land?<\/strong>“<\/em>. After lowering the nose to get airspeed stabilized I would look around, point and say “Over there”. If the spot met with the instructor’s approval he would say “OK. Give it some power”<\/strong><\/em> and we would level off and move on to other tasks. I went through the exercise so many times that I was really surprised one day when the instructor didn’t call for me to power the Continental back up<\/span>. So, I just followed through and made a dead stick landing on a mowed grass farm field. He said, “Good job. Now you get to make a soft field takeoff<\/strong>“<\/em>. We jumped back into the air. Even though that was good training, it is pretty rare in the Certificated Aircraft World<\/strong> that an engine-out landing is required. Most guys figure they can do it if they have to, but never really have to prove it. When flying an Ultralight<\/strong>, though, the possibility of needing to demonstrate one’s proficiency at making an “unscheduled” dead stick landing is not “academic” – at least in the early days. Much about that has changed in the intervening 30 years. I bought my current Rotax 4 years ago from Air-Tech of Louisiana<\/strong><\/a>. It has run flawlessly during that time. I can’t tell you how nice that is… (I have to constantly warn myself not to get complacent, though)<\/p>\n Which brings me to the point of this writing exercise. Rotax<\/strong><\/a> tells everyone to replace a 503 crankshaft<\/strong> at 300 hours of use. Some very reputable guys will tell you this is a Lawyer’s Ploy<\/strong> so as to exempt Rotax<\/strong> from any blame for crank failure should a particular owner be less than careful with his engine power settings or fuel\/oil mixtures. They will tell you the cranks are good up to 1,000 hours. I tucked that data into the “deep consideration” memory partition of my cranial computer<\/strong>.<\/p>\n There is also the idea out there that you can run the pistons and rings “somewhat indefinitely<\/em>” as long as the measured cylinder compression is in tolerance. I filed that info in the appropriate place also<\/strong>.<\/p>\n The third major area of wear consideration in these rather simple engines is the bearings and seals<\/strong>. This is where the great seers of the Rotax World<\/strong> become less confident in their prognostications. The PTO<\/strong> (Power Take Off<\/em>) seal<\/strong> is visible on the exterior of the motor and can be examined for dryness, cracking or distension. Not so for examination of the inner crank bearings or the front seal. Some will say the condition of the bearings can be detected by feeling the crankshaft as it is gently turned. I believe this “bumpiness” or “sliding” can be reliably detected in the mechanic population at the same percentage as the rarest of safe crackers using “finger feel” to detect the movement of tumblers within the lock of a wall safe. This talent is extremely rare and I suspect tales of\u00a0 success using this method have a tendency for exaggeration. It comes off to me like “dowsing” for water wells.<\/p>\n Upon evaluation of all this evidence, my solution was to “blow it all out<\/strong>“. I decided to have the engine completely overhauled<\/strong> with a new crankshaft, pistons, rings, seals and bearings. In addition, I replaced all three of the propeller reduction drive bearings AND<\/strong> all the fuel lines. In other words, I decided to replace all wear items on the plane – tires & inner tubes<\/strong>, too.<\/p>\n Don’t Wait For The Failure – Continually Move It Out To Infinity (and Beyond…) Over my years of flying Ultralights<\/strong> I have listened with wonderment to guys who talk about “making ’em last” (there is some of this thinking with certificated airplanes, too, and definitely automobiles)<\/em>. What I mean by that is they will look at an old drive belt or an old spark plug or an old nylock nut or some old fuel line or a worn electrical wire and actually be proud to leave it on their plane rather than changing it out with a new part. They seem to actually believe they can “read” the MTTF<\/strong> (Mean Time To Failure<\/em>) of various objects. At the root of it, I think they think they are saving money. I don’t get that<\/strong>. There is absolutely NO SAVINGS<\/span><\/strong> in running stuff ’till it breaks. This follows with cars, bikes, motorcycles, hoses on washing machines – you name it. Invariably when you play that game, the part will fail at a time which will cost you way more<\/strong> in time, money and hassle factor<\/strong><\/em> than it ever would cost when you <\/span>replace <\/span>it on your terms<\/span><\/strong>.<\/p>\n Here’s a good method: Envision old wear parts<\/strong> as broken parts<\/strong>. When you do this you give yourself the power<\/span> to take that “failed part<\/strong>” and throw it in the garbage. That is how you can best eliminate the possibility you ever learn what I’ll call the ATTF<\/strong> – Actual Time To Failure<\/em><\/strong> – of your motor or other system.<\/p>\n Of course we live in a fallen world and failure can still occur when everything has been done to prevent it. The odds go with prudence, though, every time.<\/p>\n In an earlier posting (HERE<\/a>), I described the brain wrangling I put myself through to arrive at the conclusion that The Sky Surfer<\/strong> was not up to the skill level I expect<\/strong> as the person to rebuild my Rotax 503. There is no reason to go over that again. I had Rotax Rick of Naples, Florida<\/strong> to re-build my engine.<\/p>\n Rick did his job. Now I’ll get to some pictures and\u00a0 descriptions of my part<\/strong> of this major overhaul.<\/p>\n Friday, 30 Nov 2012 – Quicksilver At Rest Minding Its Own Business<\/p><\/div>\n I came out on Friday afternoon to check things over and remove spark plugs and fuel lines and things like that in preparation for the engine drop the following day.<\/p>\n Before starting, I took loads of pictures of the engine and drive train as “templates” to increase my chances of re-assembling the different sections the same way.<\/p><\/div>\n I arrived early in the morning Saturday 1 December to take the engine off. I had it in my mind I would do this in a couple of hours, pack it up, take it to FedEx to ship it to Rotax Rick and be back in my office with time to get some “business” work done that the afternoon. Get Real. I wasn’t even close. Definitely “wishful thinking”. I was in the hangar until darkness started to fall.<\/p>\n Brian The Ultralight Surgeon – Photo by Joe Bryant<\/p><\/div>\n Above you can see that I like to use a lot of light<\/strong>. The spotlight in the background is one I use for shooting TV spots and other moving pictures. It has a 1,000 watt tungsten bulb and is very bright. It has the additional benefit in a chilly hangar of putting out substantial heat. Sometimes I use 2 or 3 of them. Of late, I have also taken to wearing the headlamp you see. If you haven’t used one of these LED headlamps<\/strong> when working you should try it. They help a lot<\/span>.<\/p>\n My buddy Joe Bryant<\/strong> showed up at the hangar around 10:30 am. I asked him to take the picture. It looks like I had not accomplished much in 2+ hours. At least it is not obvious<\/em> what I had accomplished in a couple of hours. My method is slow but meticulous. Every bolt, nut and washer I removed was tagged and described using that special blue tape<\/strong> you see sitting on the pilot seat. I am glad I did this because I had no problem putting the right bolt in the right hole 3 weeks later.<\/p>\n Brian and Joe Prepare for The Big Lift<\/p><\/div>\n The MXL Is Officially A Glider<\/p><\/div>\n Since my buddy Joe<\/strong> was hanging out with me, I enlisted him in the critical phase of lifting the motor out from under the wing. It only weighs about 70 pounds<\/strong> but it is suspended in a myriad of aluminum tubes. Because I am 6′ 1″ tall and the underside of the wing is about 4.5′ off the ground, I had to reach in to lift the motor out from a “hunched over” stance. It is not a completely horrible job but for about 20-30 seconds it can be rather intense. Once the engine is released from the root tube mount<\/strong>, you have 70 pounds of dead weight<\/strong> to ease out<\/em><\/strong> of the maze. Dropping it on the floor is not an option.<\/p>\n I have made one contribution to the art of Quicksilver engine removal and replacement. At least for those that feature an “under wing” engine placement like the MXL (some models have the engine on top of the wing).<\/p>\n The first few times<\/strong> I removed an engine, the guys who coached and\/or assisted me would just let the thing hang from the engine mount bolts and then hold the engine while unscrewing the nuts. That method turns seconds into hours as you hold the motor in place while your buddy tries to get all 4 nuts off the mount bolts in quick order (I actually did it that way by myself once!). Almost always,<\/strong> a bolt would start spinning and not release its nut OR<\/strong> suddenly a nut just flies off without warning OR<\/strong> the last nut would not come off at all. In the event of the last listed bad turn of events, you would need to quickly re-apply at least<\/span><\/strong> one nut diagonally so you could rest and try again. It was a real hassle<\/span><\/strong>. One day I decided to analyze the situation to find a better way. The solution came in the low-tech guise of The Tie-Wrap<\/strong>. These amazingly cheap but strong plastic things are employed all over the Quicksilver to guide wires and cables along the tubing. I decided they would be strong enough to temporarily hold the engine up while I removed ALL the engine mount nuts and bolts. Then all I had to do was slide the bottom engine mount out of its Tie-Wrap “loops” and the engine was free. This method has helped enormously ever since and it worked well Saturday. You’ll see a closeup photo of the tie-wrap application during the re-mount phase of this report.<\/p>\n Like Two Hunters With A\u00a0 Trophy<\/p><\/div>\n Of course we were very pleased with ourselves after accomplishing this feat and documented the moment of triumph above. It was 4 pm in the afternoon when I finally got the motor into the trunk of the Mini. By then I was too tired to mess with packing it up. All I could do after that was go home and take a nap…<\/p>\n The Drive Section With The Belts Removed<\/p><\/div>\n The drive section was left for another day.<\/p>\n Props, Pulleys, Belts and Bearings Removed<\/p><\/div>\n I figured after getting the motor off, removing the Prop drive Assembly<\/strong> would be a breeze. Wrong<\/strong>. It took me TWO (half) days<\/strong> to get the Prop Drive<\/strong> stuff off. The prop shaft goes into that box tube you see above (called the Root Tube<\/em>). It has a bearing at the front end where you see the empty bolt hole on the side of the root tube. The trailing edge wing spar bolts must come out before the bearing carrier can be removed. It was not easy to do. If I had been smart enough to lower the king post<\/strong>, which would have relieved the tension<\/strong> of the taut flying wires – it would have been MUCH easier. I won’t forget that next time…<\/p>\n Tagged And Stored For Later<\/p><\/div>\n Above you see the work table I used to array the parts I took off the plane. Also you can better see the special blue tape<\/strong> I used to mark all the items as I took them off the machine. If you look closely you can see descriptions on them. This method takes a little more time<\/strong> during dis-assembly but sped up reassembly<\/strong> enormously. Here’s a trade secret for you. This tape doesn’t come from a Federally Approved Airparts Store<\/strong>. The blue color is just happenstance. Before heading to the airport the day of the dis-assembly, I looked around my garage for some duct tape for tagging. I am SO GLAD I didn’t find the duct tape, but instead, found this blue masking tape<\/strong>. Masking tape removes easily without leaving glue behind (like duct tape does). It worked perfectly for the job. Duct tape would have been a mess.<\/p>\n The Drive Assembly (Sans Pulleys)<\/p><\/div>\n After spending an inordinate amount of time removing the drive suite, I took the picture of it above. To the lower left you see a pillow block bearing<\/strong>. This bearing needs to handle rotational speeds up to 6300 RPM<\/strong>. While that is not an outrageous speed for a bearing to handle in the world of engineering, I am told that the shaft, which attaches directly to the PTO of the Rotax, flexes<\/strong> “quite a bit” as the motor goes through different power settings. The Black Cylinder<\/strong> at the top of this shaft is a vibration-dampener<\/strong> to soften up the 2 Stroke Pulses<\/strong>.<\/p>\n Inside the cylinder at the middle of the picture is the front prop shaft bearing<\/strong> that goes on the tapered end of the rod to the right, which is the propeller shaft. The business attached to the prop shaft<\/strong> contains another bearing<\/strong>. In keeping with my desire to push the system’s MTTF off to infinity, I replaced all three bearings<\/strong>.<\/p>\n Santa Brought Me A Late Present<\/p><\/div>\n Merry Christmas!<\/strong><\/p>\n Above is the box left on my porch containing the overhauled Rotax Engine<\/strong> after being shipped to me by Rotax Rick of Naples, Florida<\/strong>. Even though the porch decoration represents Christmas, the picture above was taken on 4 January 2013<\/strong>. Regardless, it was<\/strong> my Christmas present for this year (and a few more Christmases into the future…)<\/em>. Rick did a great job on this overhaul and I recommend him highly to you. He is an A&P Mechanic<\/strong> and has done hundreds of rebuilds. I know he works on the Rotax line of engines so you can count on him for that. He may work on other brands of motors, too, but I cannot say. Here is his address and phone number if you want him to quote you a deal:<\/p>\n He gets it done faster than you expect and is very reasonable on price.<\/p>\n Packed And Ready To Roll<\/p><\/div>\n Above you see my Cooper S Production Vehicle<\/strong>. I call it that because it can hold the Camera, Tripod, Lighting, Green Screen and Grip Tools<\/strong> I need to shoot pretty much any TV commercial or interview. The only time I need a bigger vehicle is when I use my 12′ Crane<\/strong><\/a> or 10′ Slider Dolly<\/strong><\/a>. Other than that the Mini<\/strong> performs like a Maxi<\/strong>. (I should point out that I removed the rear seat and replaced it with an after-market platform)<\/em> It has plenty of room. In the picture above I had loaded every part and tool I might possibly<\/span> need at the hangar in addition to 3 work lights. Selby Aerodrome<\/a><\/strong> is 20 minutes from my home. I avoid wasting time driving back and forth. This day, I had planned well and put in a whole day re-installing the engine without having to come back for anything. The only downer was that it was 31 degrees in the hangar. But, I kept moving and did not feel the cold much.<\/p>\n Shiny – Like New<\/p><\/div>\n Top Side – Showing Engine Mounts<\/p><\/div>\n Again, Buddy Joe Bryant<\/strong> showed up to help me with the critical lift<\/strong> portion of the re-install. I took the two pictures above so you can see how nice the Rotax<\/strong> looked after coming out of the box. Rotax Rick<\/strong> painted it up nicely. The shipping crate was solid, too. The first order of events was to re-attach the motor mounts. They are obvious in the shot directly above. The mounts mate to two others of similar dimension attached to the MXL Root Tube<\/strong>. Bringing them together is when the previously described Tie Wrap<\/strong> Solution<\/strong> pays off.<\/p>\n A Close Up Of “The Tie Wrap Solution”<\/p><\/div>\n Once the nuts are tightened under the fender washers you see above, the tie wraps are cut. One of these days I am going to eliminate the group of 4 extra fender washers seen at the bottom of the suspension assembly. When we installed the 5 Belt High Thrust Kit Upgrade<\/strong>, it wasn’t certain how many shims (washers) might be necessary to align the engine<\/strong> with the PTO shaft. The alignment is done by adding shims to the center of the assembly. It turned out just 3 were required, so the bolts are a little long. On the chance that something might shift, I left it this way at first but basically forgot about the issue until now. I’ll downsize the bolts “soon”.<\/p>\n I had to acknowledge the inaccuracy of my typically, over-enthusiastic time estimate about 5 o’clock in the afternoon. I still had LOTS to finish before the plane was ready to fly. The shots below give some idea of the progress to that point and the path that lay ahead.<\/p>\n Day One Ends In Disarray<\/p><\/div>\n Engine On But No Prop, Wiring or Fuel Connections<\/p><\/div>\n Another Learning Experience<\/p><\/div>\n I started Day 2<\/strong> with high hopes of completing the rest of the re-installation that day. After 4 hours all I had accomplished is what you see above. By then I was completely worn out and went home. Though a deceptively simple assembly, again, I learned some “tricks of the trade<\/em>” the hard way<\/strong>. Going into this phase, I was a little<\/span> ahead of the game because I had the sense to lower the king post<\/strong> before starting the job. This released the tension on the cables which hold the wings in stasis. If I hadn’t done that there was absolutely no way to reattach the trailing edge spars to the root tube. Even after releasing the tension though, it was still a monumental effort…<\/p>\n The good thing about my plane is that the tolerances are still tight in this section. The rear end of the root tube<\/strong> of a Quicksilver<\/strong> takes a lot of stress. The reason this<\/span> root tube is fairly new is that my Buddy and Quicksilver Expert Steve Ewing<\/strong> discovered a spiral crack in the root tube when I bought the MXL<\/strong> used 5 years ago. He was replacing my fabric and cables, etc. when he noticed a spiral crack<\/strong> in the aft section of the root tube.<\/p>\nWhat Is The Rotax 503 MTBF?<\/h4>\n
\n<\/strong><\/p>\nPart Of Prudence Is Picking A Prime Partsmith<\/h4>\n
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<\/a>Prep Work<\/h4>\n
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<\/a>Did I Really Believe That?<\/h4>\n
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<\/a>Let There Be Light<\/h4>\n
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<\/a>Calypso Isometrics<\/h4>\n
Brian’s Big Contribution To Aircraft Maintenance<\/h4>\n
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<\/a>Looks Can Be Deceiving<\/h4>\n
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<\/a>Aircraft Dis-assembly Marker Blue Tape<\/h4>\n
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<\/a>Drive Assembly Gets Attention, Too<\/h4>\n
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<\/a>Ron Davis
\n940 Ninth Street S.W.
\nNaples, Fla. 34117<\/h4>\n(239) 572-0021<\/h4>\n
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<\/a>The Mini Cooper S Production Vehicle<\/h4>\n
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<\/a>As Good As New<\/h4>\n
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<\/a>Production Grinds To A Halt<\/h4>\n
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<\/a>Day Two<\/h4>\n
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<\/a>Slow Going<\/h4>\n
Tight Tolerances<\/h4>\n
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