Guest Maj Millard Posted June 21, 2012 Share Posted June 21, 2012 On props and spinners,........... the prop is the highest stressed item on the aircraft, for the number of different forces it is subject to in-flight, especially at full power. Obviously the hub that holds the blades is subject to heaps of rotational stresses also. 2nd most stressed is the engine crankshaft, followed by the pilot in 3rd !............. Seriously, alum prop hubs can crack, and need to be checked closly. The potential results of not finding a crack are serious indeed, and can easily lead the the engine departing the aircraft in the worst-case scenero. Over-torquing prop hub bolts can also lead to non-normal stresses, that can then lead to cracking. Always observe the correct torque for prop-hub bolts, and if you don't know what they are, make a point of finding out !.... I have split a lot of alum prop-hubs, and generally I find some corrosion in them all, to some degree.Some serious, some just starting. The European and Russian ones are the worst, and the alum on them appears to be sub-standard at times, and particulary prone to corrosion, especially in coastal and inland dusty areas (minerals in dust reacting with the alum). The alum blade butts fitted to some blades, also corrode badly on some types. This is not an area you want corrosion on !...... I will generally split my personal alum hub at least once a year, (Powerfin 3-blade) for a clean, close inspection for cracks, (internally and externally), and I'll often replace all the securing bolts at the same time. I don't like alum spinners personally, although some types properly fitted, will give good service and look great. I have found lots of spinner and back plate cracks over the years, and a spinner that separates can cause serious prop damage as it departs. One ended up firmly lodged in the leading edge of a wing, and others have been driven back by the prop straight through the windscreen. Some well made composit spinner and back plates are a good buy, and appear to be more capable of absorbing rotational stresses and vibrations in service. Always check that your spinner is firm during your pre-flight, with no loose screws and no movement at all. Small movements quickly become big movements when rotating at 3000 rpms or so............................................................................................Maj.... Link to comment Share on other sites More sharing options...
Sapphire Posted June 22, 2012 Author Share Posted June 22, 2012 The most significant preflight "find" for me was to discover that one exhaust manifold pipe had broken away at the cylinder flange (IO-470K) on my (ex) Beech C33 Debonair. As my proposed trip was from Jandakot to Yulara, I consider this a life saving find. I actually went looking for an exhaust defect as my GEM engine monitor had shown high CHT and low EGT on that cylinder during the previous flight. Another time (many years earlier) I discovered a hole the size of a five cent piece in the rear of a Pawnee muffler, immediately in front of the firewall. As the fibreglass fuel tank was right behind the firewall, I grounded the gliding clubs tug for the weekend. Some club members were incensed at this and I actually got dropped from the tug pilot roster because of it. Thirty years later, I still fail to see that I did anything wrong. I wanted to fly as much as they did! John. Of course you had to ground the plane but were there no facilities to weld it there? One gliding club I was with had continual problems with cracked muffler on a Pawnee. Many mornings they had it pulled off and someone was welding it up. Talking about welding, I am restoring a boat trailer and have to do vertical welds and welding underneath which is the worst when "lava" dribbles down on you. Is gasless mig welding easier than the stick welding I am doing? 1 Link to comment Share on other sites More sharing options...
68volksy Posted June 23, 2012 Share Posted June 23, 2012 Hey 68volksyCan you remember the brand of the prop. RickH No luck there i'm afraid. I thought I did pretty well remembering the name of the aircraft! It's an aluminium hub and the Vision had a Jabiru engine at the time i think. If i remember i'll ask when i'm out there later today. Link to comment Share on other sites More sharing options...
turboplanner Posted June 23, 2012 Share Posted June 23, 2012 Of course you had to ground the plane but were there no facilities to weld it there? One gliding club I was with had continual problems with cracked muffler on a Pawnee. Many mornings they had it pulled off and someone was welding it up. Talking about welding, I am restoring a boat trailer and have to do vertical welds and welding underneath which is the worst when "lava" dribbles down on you. Is gasless mig welding easier than the stick welding I am doing? No joy there I'm afraid, it looks very daggy too and I wouldn't guarantee it's strength. Downhsnd welding is a skill acquired. I haven't acquired it. Link to comment Share on other sites More sharing options...
Guernsey Posted June 23, 2012 Share Posted June 23, 2012 Of course you had to ground the plane but were there no facilities to weld it there? One gliding club I was with had continual problems with cracked muffler on a Pawnee. Many mornings they had it pulled off and someone was welding it up. Talking about welding, I am restoring a boat trailer and have to do vertical welds and welding underneath which is the worst when "lava" dribbles down on you. Is gasless mig welding easier than the stick welding I am doing? Try sending a PM to KJFAB ( he may not be watching at the moment) as he is an expert on all forms of welding. He has his own Fabrication factory Alan. Link to comment Share on other sites More sharing options...
facthunter Posted June 23, 2012 Share Posted June 23, 2012 Oxy welding is still used by the oldtmers for airframe welding in some places. It can be very neat done well. There is a lot of heat associated with it. Mufflers are contaminated when used, with combustion by products, but if cleaned well should OK with oxy. TIG is an easy technique but can have hard edges if it cools quickly and be brittle. and crack. Nev Link to comment Share on other sites More sharing options...
eightyknots Posted June 23, 2012 Share Posted June 23, 2012 As a low-time pilot-in-training, I have only found one thing of concern in a preflight. I was checking the fuel in a Piper Super Cub and it looked consistent. There was no interface between two liquids as you'd expect to see if there was a bit of water in the avgas. However, my previous flight instructor said: "always smell the fuel as well" which I did. There was no smell on this occasion so what I was looking at was 100% water. Taking more and more liquid out via the gascolator I finally got both and ultimately it became 100% fuel. I will continue to use my nose as well as my eyes during the fuel check: I was very pleased to have found the H2O before flying off. Flying schools have a big advantage here, but there's nothing to stop owners checking each other's aircraft every now and again. A different pair of eyes will often find and issue you've been subconsciously ignoring. That sounds like an excellent suggestion t-p. I wonder how many people on this Forum (who don't fly a club aircraft) actually get another person to check their aircraft over with a different set of eyes? 2 Link to comment Share on other sites More sharing options...
Sapphire Posted June 23, 2012 Author Share Posted June 23, 2012 How does so much water get into the fuel? After I got rid of it I'd be looking at that. A car I worked on had mostly water instead of oil in the crankcase-blown head gasket. Link to comment Share on other sites More sharing options...
facthunter Posted June 23, 2012 Share Posted June 23, 2012 Sapphire , you get some condensation. We used to completely fill the tanks of all aircraft prior to putting them in the hangar each night. Some may go in with the fuel if you are using drums. Some must get in throught the fuel tank caps if they're recessed. We never found the amount of water that seems to be around these days. You should go to a lot of effert to get it all out. Some fuel systems will trap it more than others. Nev Link to comment Share on other sites More sharing options...
Studentbiggles Posted June 23, 2012 Share Posted June 23, 2012 Hi eightyknots,I always use the the abbv. "C.O.W.S"......Colour, Odour, Water, Sediment.......when I do a fuel check.............and easy to remember.........Alley 3 Link to comment Share on other sites More sharing options...
facthunter Posted June 23, 2012 Share Posted June 23, 2012 There is a paste that you are supposed to use. It changes colour with water. Nev Link to comment Share on other sites More sharing options...
rdarby Posted June 23, 2012 Share Posted June 23, 2012 For me it's what you don't find. I have found loose spats before. First what I didn't find was that the flaps didn't work. I selected full flaps and gave them a wiggle. All good. At the holding point before taking off I select first stage of flap and this time the lever is just loose like it's not connected to anything. A spring had come loose in it. The preflight didn't detect this, and couldn't. Second was years ago flying an Avid Flyer. Part of the prefligth was to push on the metal frame and see if it moved, to see if a strut or spar etc. had come loose. I did that and didnt' detect anything. Taxing out the instructor asked if I felt the plane was bouncing like a boat? We got out and he cut some fabric away with his pocket knife, and there was an old repair on one of the four fuselage spars that had been SPOT WELDED to join it again, and had now come loose. My preflight should have picked that up if it was broken at the time. As a result I have the fuz of the SportStar a good hard shove on my first preflight with it, much to the horror of the instructor! Ryan Link to comment Share on other sites More sharing options...
M61A1 Posted June 23, 2012 Share Posted June 23, 2012 Those who do not do preflight checks need to ask themselves one question:"Do I feel lucky?" Well, do ya punk? I feel more comfortable going on a Kiowa maintenance test flight than a Virgin or Qantas flight because I'm allowed, even encouraged to do my own walkaround(I'm a maintainer, not a test pilot). Most of the time, if I know I'll be on the test flight, I'll make sure I do the B/F as well. Link to comment Share on other sites More sharing options...
Ballpoint 246niner Posted June 23, 2012 Share Posted June 23, 2012 I have a very simple mantra I teach students, The three C's...... Correct operation and assembly-- is it the way it should be? Condition. -- is it safe and per manufacturer standard? Change-- has it changed since last time I checked it? Remember assume there is something wrong with the aircraft, thoroughly , uninterrupted and patiently try to find what's wrong-- if you can,t find anything then it's been checked ok for flight. 3 Link to comment Share on other sites More sharing options...
M61A1 Posted June 23, 2012 Share Posted June 23, 2012 How does so much water get into the fuel? After I got rid of it I'd be looking at that. A car I worked on had mostly water instead of oil in the crankcase-blown head gasket. If the a/c is left outside in rain, sometimes caps can leak. More often from fuel drums left outside, and not stored chocked up on one side, if water is on top of the drum and is cooled overnight, the resulting vacuum can draw in the water, the drum pump then picks up the water at the bottom of the drum. Link to comment Share on other sites More sharing options...
kgwilson Posted June 23, 2012 Share Posted June 23, 2012 Someone left the fitted cover off an Aeroclub C172 which lived outside & as I was walking out to do the preflight the next morning, I spotted a bird flying out from the exhaust area. I looked in through the oil filler cover & saw a bit of dry straw. When the cowl top was removed we took out enough straw, grass, leaves & twigs to make a good bed for a medium sized dog. I was amazed at how a couple of starlings had managed to get all that in there in only a few hours. Link to comment Share on other sites More sharing options...
Guest Maj Millard Posted June 23, 2012 Share Posted June 23, 2012 Birds can and do built nests in aircraft in less than a day. Often you spot some debis that they have left as a clue. Years ago a gentleman who had just flown down from his mountain retreat in a Bonanza, came to me after landing complaining of a burning smell in flight .......... A quick look into the engine cowl showed a large mass of sticks and kindling, sitting on one bank of cylinders just ready to ignite !! This was no sparrow nest, with lots of large twigs suggesting more like an owl or small hawk........would have made a great engine-bay fire. Don't think this pilot (?) had done much of a preflight.................................Maj... Link to comment Share on other sites More sharing options...
turboplanner Posted June 23, 2012 Share Posted June 23, 2012 How does so much water get into the fuel? After I got rid of it I'd be looking at that. A car I worked on had mostly water instead of oil in the crankcase-blown head gasket. There is always water in air - often radio stations broadcast the humidity level for the day, so if the humidity level is 30% and you do a long trip and arrive with minimum fuel, then park the aircraft overnight, the humidity is going top turn to water when the tank cools. If you do it repeatedly, you've got yourself a water producer. This is also why drums at remote strips often have water in them. There's a correct way to store a drum, on it's side with the bung location immersed, but day to day filling with a new plug of air is contributing to the water. The old farmer's trick minimises this. After everyday's work, the tractor tank is filled, so there's no air left to drop its humidity. 1 Link to comment Share on other sites More sharing options...
motzartmerv Posted June 23, 2012 Share Posted June 23, 2012 You have to be carefull, if you have a lot of water, your fuel samplaer can fill with water alone, so theres no bubbles in the bottom. You think its clear and go onto the next tank, but really all you got was a full sampler of water. Its an old chestnut that has got quite a few people. A few months ago I was shifting a Partnavia for a friend for her IFR test. She was draining the fuel from the stbd engine and I thought it looked a bit clear to be avgas. Further drains revealed it was water. She got about 7 or 8 full samplers full of water before fuel finally came out. I suspected that seeing it in the sump of the engine it had been sucked through on a previous start attempt...Sure enough the Maintenance relase confirmed the gentlemen who attempted to fly it the day before could not start the stbd engine. And nor could we.. a week and a few thousand dollars later, the fuel injectors were overhauled. The regs state that a small sample of fuel must be added to the sampler before draining fuel. But a bit of a close inspection should suffice, some people poor a few mls over there fingers to feel and make sure its avgas/mogas. 2 Link to comment Share on other sites More sharing options...
turboplanner Posted June 23, 2012 Share Posted June 23, 2012 I like the "smell it" comment earlier on. 1 Link to comment Share on other sites More sharing options...
Louis Moore Posted June 23, 2012 Share Posted June 23, 2012 Best one was with an Auster. Just happened to see some saw dust near the right inner wing on the ground. Undid a zipper and the spar was 1/2 chewed through by rats. Nev Expensive Rats Nev! I am going to go check my spar ...... be back later! Link to comment Share on other sites More sharing options...
motzartmerv Posted June 24, 2012 Share Posted June 24, 2012 I like the "smell it" comment earlier on. Yea the problem with that is that if you have just drained a "real" bit of fuel the sampler still stinks of fuel, even with water in it. I like to demo that when Im teaching peeps about the whole fuel drain thing. Aswel as how to test for ethanol, which is quick and easy with your standard fuel sampler. Link to comment Share on other sites More sharing options...
Louis Moore Posted June 24, 2012 Share Posted June 24, 2012 Yea the problem with that is that if you have just drained a "real" bit of fuel the sampler still stinks of fuel, even with water in it. I like to demo that when Im teaching peeps about the whole fuel drain thing. Aswel as how to test for ethanol, which is quick and easy with your standard fuel sampler. Motz I have heard people talk about the ethonal testing, any chance you could explain the procedure to me on here? If it is going to be thread drift would you mind starting a new thread on it? Cheers Link to comment Share on other sites More sharing options...
Sapphire Posted June 24, 2012 Author Share Posted June 24, 2012 Expensive Rats Nev! I am going to go check my spar ...... be back later! I like the way this thread is going-people rushing out to check things they never thought of and I'll be doing the same. One more. Long time ago an aeroclub plane had a spear pushed through the rudder-something you'd want to pick up. I understand that interference with an aircraft carries an automatic jail sentence, as opposed to, say, interfering with a car. I had three windcreens on my cars smashed by some Homeswest lunatic kid. Had video of him doing it, fingerprints, knew where he lived and the pub he frequented. The police did nothing. The jails must be too full. Link to comment Share on other sites More sharing options...
motzartmerv Posted June 24, 2012 Share Posted June 24, 2012 No worries Louis. Your normal yellow (and black) fuel samplers have markings on the clear tube. Theres a line down the bottom about 3/4 of an inch up the tube. All you need to do is add water to the sampler up to this line. Then fill the sampler with the fuel you want to test. Theres a line at the top to tell you where to fill to. Once this is done, you shake the sampler for about 10 seconds. Inspect the line at the bottom. If there is ethanol in the fuel, the water absorbs it, and the level of water will increase. There is a gradiant scale on most samplers, i think its in 5% increments. So it will even tell you what % of ethanol is present in the fuel. :) cheers 2 Link to comment Share on other sites More sharing options...
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