Zenith Aircraft Builders and Flyers
Online Community of Zenith Builders and Flyers
"Aircraft Quality" - Something To Think About.
We all know the old joke about the cost of hardware - put the word "marine" in front of a product description and you can double the price. Put the words "aircraft quality" in front and you can quadruple the price again.
I've lost count of the number of stories I've heard or been told about how certain bits of aircraft hardware are really vastly overpriced consumer items that have simply been "re-badged". For example, the internal door handle for a C172 is from a 1958 Rambler car or whatever and the oil filter for your engine is the same as the one from Home Depot that costs a quarter of the price, etc. etc. I'm sure we all have examples, and in many cases I'm sure its true. However, I'd like to add a little note of caution. We all know the standard retort to someone who tells us they have a new way of flying an aircraft; "Do you want to be your own test pilot?" I'd like to add another caution; "Do you want to be your own mechanical / electrical / aeronautical Engineer?"
There is a lot of stuff around that LOOKS like its aircraft quality or is "just as good as" aircraft quality. Quite a lot of it actually is....But here is the problem, how do YOU know? I submit, most of us don't know, but even then, if we may be talking about something that really doesn't matter to airworthiness anyway so who cares? Or so we think..........
For example, I know for a fact that the sheet metal of modern cars is made to tighter tolerances than that of an F18 fighter because I've messed around in the Airline and Aerospace industry a long time ago. I'm also pretty sure that the manufacturing technology in the auto industry is way ahead of the aviation industry in many respects. The trouble is that the quality dictum about "Fitness for purpose" means what it says. "Fitness for purpose" means one thing when you are talking about a something that merely annoys you if it fails in your car. It may be terrifying rather than just annoying when the same failure happens at Five thousand feet, in turbulence over forest with no landing place in sight.
Take ball bearings for example. Aircraft grade and automotive quality look the same. They may even have the same part number and of course look identical - to you., the reality is that the finished bearings got graded - the best went to the aviation industry, the average to the auto industry and the rejects went to Home Depot for the schmucks to buy. To put it another way, do I buy an aircraft grade switch or just something that looks like it will do the job? Do I buy a converted automotive engine or a purpose built aircraft engine? They both do the same job don't they? You find out.
Replies to This Discussion
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Permalink Reply by Paul Bonasera on
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Hope your not building an aircraft with those noncertified pop rivits, brakes, wing struts, and glass panels, just to put a certifed engine in front of it. Do you think Matco buyes there bearings from the same place Cleavland does? I would guess from the price differance, NO.
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Permalink Reply by Mack P. Kreizenbeck on
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Got to add my 2-bits.
You forgot about the Tucker Automobile!
Used a Cont. or a Lyc. (can't remember which) 6 cylinder in the area where the trunk is supposed to be. Water cooled too.
Fastest car made during the 1940's - set a world records, with marathons at a continuous 100+ MPH.
Now, who said they didn't use aircraft engines in autos?
Couldn't match the quality, safety and engineering aspects of the car so GM, Ford, Chrysler and a couple of others (who are no longer in business) ganged up and put Tucker out of business by using tactics not becoming to corporations.
Sorry about the history lesson - got carried away.
Mack
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Permalink Reply by Louis W. Ott on
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Mack,
The Tucker used a Franklin engine. I think an O-335. Inline 4 cyl engines have a nasty 2nd order harmonic vibration. It can be minimized by using two balance shafts rotating at twice crankshaft RPM. Mitsubishi pioneered relatively modern use of the balance shafts. Other companies such as Porsche (944, 968), Saab, Fiat, and others licensed Mitsubishi technology for their inline fours. Opposed engines are inherently balanced and need no balance shafts. http://www.autozine.org/technical_school/engine/smooth2.htm
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Permalink Reply by Bob Pustell on
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Yes, the Tucker used Franklin engines. Franklin had a 65 percent market share in light aircraft engines before Tucker bought the company to get engines for his cars (because he did not have deep enough pockets to develop his own engine and the big auto makers would not sell him engines, he bought an airplane engine company). He canceled all outstanding aircraft engine orders and stopped taking orders from anyone. Then, he had Franklin concentrate on the engine for his car. Then, his car went bust. Franklin never recovered. It went from the dominant engine in the field to a straggler who never recovered. They shut down in the 70's.
My 1947 Stinson has a 165 HP Franklin. Fabulous engine!! Smooth and strong. Way ahead of the others. A worn out Franklin has tighter internal tolerances than a brand new Lycoming or Continental. Replaceable cylinder liners, balanced components, inspectable bottom end, the list goes on and on. What a shame that the engine line fell victim to auto maker politics. There is a move afoot now to bring back the line, I hope it prospers.
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Permalink Reply by Chris Aysen on
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Looks like I got to add my 2 cents also. Geoff you make a very good point. When you look at the Lyc. and Cont. they have been around for a long time and are PROVEN quality. However, the catagory of Light Sport offers some unique challenges (weight sensitivity for one). I think thats why Jan's engine can find a place in the market. But I think inherit with any NEW technology new challenges arise. I find, for auto-conversions, its going to be the amount of time the engine can stay at an elevated rpm range without to much negative affect on the internals, not normal for its initial purpose. Most auto engines do their jobs in the cars at half or less than rpm range required for that same engine in an aircraft. But we are making advances in oil viscosities and metallurgy so its a wait-n-see proposition. I don't believe we can use the argument of BMWs in WWI. The infantcy of flight can't be a standard we have made leap years of advances in comparison. Geoff is totally right in my opinion when he supports proven technology. However, common sense tells us anything can happen at anytime; its just what are the odds.I like water cooled aircraft engines thats just me personally. Jan's engine is a step in the right direction and he's right in having TOTAL belief in his engine; if he doesn't then the project would probably fail. At the same time he should realize that challenges are still ahead. I do hope the engine can meet those challenges.
Geoff's take on quality of materials is also a factor; main reason; LIABILITY. Lyc. and Cont. are probably exposed to liability more than all other engine manufacturers (general aviation) put together. However, I have no doubt that some things fall thru the cracks sometimes. But I would assume they take quality VERY SERIOUSLY. It is common practice in the manufacturing of any product to pass on substandard parts to areas of less liability.
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