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Home✈️Aircraft🚁HelicopterAerial Photography and Video › Routine AP Ship Maintenance Thread
10-26-2006 09:58 AM  12 years ago
FCM

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Surrey, England

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There has to be a means of tracking the airframes and "proof" of what you have done or haven't done to the aircraft in case of an investigation.
Just how is the FAA or any other regulatory authority going to know what you have or haven't done to a model helicopter? Sorry, I know this is a bit off topic but coming from a full-size aircraft maintenance background, the idea of tracking components, OEM's time lifed items and certified maintenance recording is a complete joke and whoever it is at the FAA that is considering these regulations has been getting too much wacky - backy as far as I can tell.

Paul.
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10-26-2006 02:16 PM  12 years ago
BigguyOz

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Forster, New South Wales, Australia

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Thanks Jason. Paul, I can agree with the general thrust of your comments, but what Jason is working on ie "self-certification" is by a huge long way the lesser of evils. Here in Australia, despite this being totally impractical, unenforceable and ridiculous, commercial R/C flights can only be officially made under very stringent conditions with all sorts of restrictions and hoops to climb through.

At least in Canada there seems to be some sort of cooperation by the authorities, whereas in Australia the local equivalent of the FAA, CASA, has its hands full trying to keep up with administration of airports and GA.

Consequently, I understand there are only TWO legal R/C AP operators in this country.

Jason and others are trying hard to strike a balance, and I believe self-certification is the best that will be obtained. The alternative doesn't bear thinking about...
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10-26-2006 02:29 PM  12 years ago
TCGliderguy

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Albuquerque, New Mexico

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Is it too much to ask that this thread stay on topic? There are lots of places to debate the "what if" aspects of political decisions.....

-Taylor
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10-26-2006 02:42 PM  12 years ago
Brett Horton

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Yes I agree
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10-26-2006 04:04 PM  12 years ago
BigguyOz

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Sorry! I was just picking up on why Jason wanted the information in the first place...
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10-26-2006 04:38 PM  12 years ago
Brett Horton

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No problem!
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10-26-2006 09:41 PM  12 years ago
AceBird

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Utica, NY USA

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I don’t know if this is off topic or not but someone mentioned twin batteries (redundancy). Using two batteries is not redundancy by themselves. It would require some kind of monitoring and switching circuit to provide any advantage at all. It is a bad idea to just put two batteries in parallel (it seemed like this was the case for one example). Maintenance of batteries has already been well documented. Cycle the cells based on hours of use and or periodic time intervals. If the capacity of the cycled cell comes up less than 80% of the rated capacity of the pack then replace them, they are considered warn out.

For gas powered helicopters I would highly recommend an on board charger as a redundant power source. It usually covers a bad switch as well as dead cells and depending on the wiring it can also cover a bad connector. However battery cycling is still required.

Someone mentioned never using a nylon locknut over again. I ask why? They are the least effective method of fastener retention anyway. If you use loc-tite on a used nylon nut you are better off than a brand new one by itself. So why can’t they be used again?

If you are writing a book about maintenance with the intention of creating a manual you need to do trending analysis. That starts with the log books that you mentioned and ends with an analysis of mean time failure. Anything less is just a collection of opinions.
Ace
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10-26-2006 09:56 PM  12 years ago
Torsten

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Germany

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i recommend to read the book "fatal traps for helicopter pilots"

it´s from the full scale boys, but very good reading as most things apply to us as well in some way or another.
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10-26-2006 10:03 PM  12 years ago
Professorwiz

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Livonia, Michigan - USA

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According to Amazon, the Fatal Traps book is not out yet.
Russ
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10-26-2006 10:09 PM  12 years ago
aambrose

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Pana, IL

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Someone mentioned never using a nylon locknut over again. I ask why? They are the least effective method of fastener retention anyway. If you use loc-tite on a used nylon nut you are better off than a brand new one by itself. So why can’t they be used again?
Ace,
Go ahead and Locktite the bolts that go into your nylon insert locknuts! For that matter, Locktite every bolt and screw that goes into plastic/nylon. Just let me know when and where you're flying so I can stay far away!

The whole concept behind the nylon insert isn't rocket science. The nylon insert grips the threads of the bolt once the threads pass through the slightly smaller opening in the nylon insert. Once the threads cut their way through, they're held in place by a tight friction fit. Once you back the bolt out, the nylon is malformed in a way that a new bolt inserted into the nut will not have the same snug fit as the original did.

Again, this all boils down to personal preference. When I have a huge liability riding in the air, I don't want the fact that I saved a fraction of a cent by using a nylon insert locknut more than once to be the reason my ship comes down. Just isnt worth it. In my ultralight flying days, it was my own butt in the air. The practice just carried over into the AP business.

Tony
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10-26-2006 10:30 PM  12 years ago
Brett Horton

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Changing Fibre lock nuts is a standard thing in the Full Scale arena. I have been an A&P for 13 years or so.... Don't second guess tried and true full scale techniques.
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10-26-2006 10:44 PM  12 years ago
TCGliderguy

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Albuquerque, New Mexico

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I'd like to pursue a conversation about something that AceBird said...

>Using two batteries is not redundancy by themselves. It would require some kind of monitoring and switching circuit to provide any advantage at all. It is a bad idea to just put two batteries in parallel (it seemed like this was the case for one example).< but I'm going to start a new thread to do it.....

-Taylor
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10-26-2006 10:52 PM  12 years ago
Torsten

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Germany

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Russ,

i have mine since last year. maybe a reprint ?
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10-27-2006 12:19 AM  12 years ago
Professorwiz

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Yes, I just read that the 1st edition is out of print and they are getting a 2nd printing ready. Thanks, should have examined the info more closly.
Russ
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10-27-2006 06:45 PM  12 years ago
talk the torque

rrApprentice

SA

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I also had the rubber washer of my Zenoah Z230 choke bolt perish and pop out. Luckily the loose choke was closing and opening so the engine would cut and then start again. I made it down in one piece but was emotinally finished. Either screw the choke into the open position and just clip off the cover and place finger over carb to choke or replace the rubber washer but put a spring on the choke lever to pull it open. I prefer choking the carb over using the carb primer pump because It fires much sooner by choking it and puts a lot less wear on my pull start.

In addition to all the other checks I also spin the rotor up by hand and just listen for a second or two to the belt and the bearings of the main and tail.

Jason
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10-27-2006 07:32 PM  12 years ago
mwp

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Chatham, Ontario, Canada

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I am a firm believer that high stress hardware such as the main shaft bolts (upper and lower) should be a long shank version for added shear resistance.

In this case of this helicopter (Hirobo Sceadu Evo 50) the upper M3x20 cap screw was substituted with an M3x35 version cut to 22mm in length to allow for the washers.

The substituted bolt offered a sufficient unthreaded length to pass fully through the shaft and hub. Some of the extra unthreaded length needed to be taken up with the flat washers to allow for proper tightening.
(Edit - 3 washers likely needed in this case.)


Mark
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10-27-2006 08:12 PM  12 years ago
mwp

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Chatham, Ontario, Canada

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One more tip for the interested here.

I am documenting my build modifications of a backup camera helicopter and wanted to pass this on.

I have found that pivot balls of the pictured type tend to be a slightly loose fit on the 2mm screws resulting in some play if the screw loosens slightly. The addition of the shim also helps with the accuracy and consistency of the control systems particularly when trying to match pairs of push rods.


Mark
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10-27-2006 10:07 PM  12 years ago
AceBird

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Utica, NY USA

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Yikes Mark, the bolt is too long or the spacer is too thin. The shearing action is on the inside of the bore so the unthreaded part of the screw does not have to be outside the clamp. You want at least two full threads more than the point that the nut gets tight. There really should be a flat milled on the outside of the collar so the head of the screw and nut have a place to bear on the clamp. I have to give Century a gold star on their head design. They not only have the flats for the shear bolt they have two other screws for clamping.


(I tried to show the century head pic but it doesn't work)
Ace
What could be more fun?
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10-27-2006 11:10 PM  12 years ago
mwp

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Chatham, Ontario, Canada

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the bolt is too long or the spacer is too thin
Good point Ace, actually I was thinking the same thing. The final assembly will have extra washers added as necessary. The unthreaded portion of next smaller bolt would not fully pass through the main shaft.

Mark
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10-28-2006 12:48 AM  12 years ago
AceBird

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Utica, NY USA

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You might consider putting the extra washers on the head side to balance the bolt off.Ace
What could be more fun?
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