weighing a plane

Discussion in 'Maintenance Bay' started by hankrausch, Jan 8, 2018.

  1. hankrausch

    hankrausch Pre-takeoff checklist

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    I came into possession of a large amount of strain gauges and I wondering what to do with them. Thinking about putting them into a wheatstone bridge and making a scale. each gauge is rated to 50 kg so was thinking of making 5 bridges which would weigh 1000 kg.

    Is there a market for weighing planes? Who does it? Would people be interested in a set of pads you can roll your plane onto and get a weight? I am thinking I could assemble a set like this for about $100 of parts.

    I found this article which talks to it:

    http://www.kit-plane-advice.com/weight-and-balance.html

    here the author makes this statement:
    "There is no regulation requiring a certified scale, even to weigh a certified aircraft. As long as you or the mechanic performing the weight and balance are confidant in the accuracy of the scale, it is legal."

    Can this be true? Based on what I know of the FAA it seems like it would be more regulated than that.

    Thanks in advance!
     
  2. AKBill

    AKBill Cleared for Takeoff

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    All scales for aviation use, manual or electronic, must be protected when stored or shipped, and they must be checked periodically for accuracy. The maximum recognized period between calibration checks is 12 months; however, this period may be reduced by an airworthiness authority dependent on the conditions of use. Scales in daily use may require a shorter interval and/or testing to determine the continued accuracy of the unit. Scales should be returned to the manufacturer for proper calibration and testing
     
  3. skier

    skier Pre-takeoff checklist

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    Open up a wing and put the strain gauges on the spar. Tie them to a computer in the cockpit. It would be fascinating to see the actual loads imposed during flights.
     
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  4. Bell206

    Bell206 Pre-takeoff checklist

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    No. Just because there is no “regulation” specifically stating a requirement doesn’t mean there are not other performance requirements like Part 43.13(a).

    Had the author simply checked the FAA reference he included at the end of his article, he would have read what AKBill posted and this:
    “Weighing aircraft with accurately calibrated scales is the only sure method of obtaining an accurate empty weight and CG location.”

    There are probably half a dozen other FAA docs that show a calibration requirement of weighing equipment.

    The author might slide by with a DAR certifying his E/AB with that “method”, but not on a TC aircraft.

    As for your idea of scales, if you can get someone to calibrate them or simply develop them as a portable “work-aid” which could be easily shipped, you might be able to rent them for a small amount. Or see if there is a need via some of the experimental websites.

    The market for a DIY set of scales would probably be very limited for TC aircraft.
     
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  5. Bell206

    Bell206 Pre-takeoff checklist

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    No need for the strain gauges. There are a few videos out there where you can actually see the flight loads in action. Which sometimes make you want to stay on the ground.
     
  6. bnt83

    bnt83 Final Approach

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    Lol, you may be able to download a kitplanes article worldwide and even get a pile of folks semi-familiar with FAA regulations to comment on anything online, but this guy sounds a whole lot like his regulating authority is not the FAA.

    Weighing aircraft --If its not calibrated and tracable, I'm not using it.
     
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  7. hankrausch

    hankrausch Pre-takeoff checklist

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    Thanks everyone I seriously suspected that and I did find the FAA circular with the bit about calibration. I like Bell206's idea of the non TC community as a "work aid".
     
  8. hankrausch

    hankrausch Pre-takeoff checklist

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    ha ha this might be one of those don't ask a question you don;t want to know the answer to things!
     
  9. Paulie

    Paulie Ejection Handle Pulled

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    When I contracted at Hawker beech we weighed the planes after interior installation and they were very anal about scale calibration. I doubt the feds don't care.
     
  10. teejayevans

    teejayevans Pattern Altitude

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    You probably can say that about actual weight of your aircraft. I’m pretty sure most would come in heavier than documented. How many log entries do you have with “weight and balance negligible”?
     
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  11. hankrausch

    hankrausch Pre-takeoff checklist

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    I think I will build this just for grins and weigh my own. I have worked with these gauges a good deal and have found them to be linear--enough--along a certain range so don;t anticipate any hurdles calibrating them. Will share the results when I am done.
     
  12. nrpetersen

    nrpetersen Pre-takeoff checklist

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    Individually the gages may be linear, but always check for cross axis sensitivity of any weighing system, even a mechanical one like a bathroom scale. Any transducer has six axes of sensitivity (the three force and three moment axes). Ideally you want five of these to be zero, and one to be the transducer, but in most cases the cross axes sensitivities will give you serious errors. Strain gaging etc is not a trivial art.
     
  13. GLMS_NC

    GLMS_NC Pre-takeoff checklist

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    This author will never touch any aircraft I work on or fly. Period. End of discussion.

    Just like a torque wrench - Calibrated regularly or do not use. This is not go-kart racing - this is aviation where mistakes from cutting corners here is what kills people. Scales and good torque wrenches are not expensive.

    You must also weigh an airplane correctly. I have seen more than one not do it correctly. Then why do it?
     
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  14. denverpilot

    denverpilot Taxi to Parking

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    You mean you don't have the special AvE Canadian torque wrench? Where you just pull until you grunt a little and then say "click!" real loud? :)
     
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  15. Paulie

    Paulie Ejection Handle Pulled

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    In many states the state troopers will lend their portable scales to private citizens. I would imagine that they are calibrated as they may be used in judicial cases. I know they are available in Texas.
     
  16. nrpetersen

    nrpetersen Pre-takeoff checklist

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    A quick check would be to weigh yourself (assuming you probably know your weight within a couple of percent) to see if the calibration remains reasonable, but then see how much your reading varies as you step on the four corners of each wheel platform. Yes this is accurate to only a couple of percent, but how much will that affect the gross weight calculations of an airplane? If nothing else the empty CG calibration should still be more accurate - unless the tape measure on the floor is inaccurate:eek:

    I don't think it is crash and burn stuff.
     
  17. Paulie

    Paulie Ejection Handle Pulled

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    Why bother doing it at all if you're going to half ass it? As I said it's not difficult to get accurate scales.
     
  18. denverpilot

    denverpilot Taxi to Parking

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    That’s very odd. I can’t imagine asking a CSP Troop for their scales...

    “Yeah, just bring those over to my hangar.”

    LOL. And I bet they want nothing at all to do with giving someone paperwork showing they’re calibrated that they can keep. Not just looking at some sticker on the side of the scale or similar.
     
  19. Clark1961

    Clark1961 Touchdown! Greaser!

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    Quit being so negative. Just call the weight-n-scale boys and ask where they are going to be today then land on the highway and drive on the scales. I'm sure they will be helpful in many ways.

    I bet they are in Weld County several days a week. You could just fly around up there until ya find'em.
     
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  20. Paulie

    Paulie Ejection Handle Pulled

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    They did it for me when I called one of the weigh stations in East Texas. They did at their own time, but they arrived. I think they enjoyed the field trip, got them away from the station. Maybe I just got the right guy in the right day.
     
  21. Paulie

    Paulie Ejection Handle Pulled

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    What's wrong with a sticker on the side? I never asked for documentation besides the sticker when I checked calibrated tools out of the tool room at American Airlines. What kind of paperwork would you expect? Troopers are public servants, not our bosses you know. Doesn't hurt to ask.
     
    Last edited: Jan 10, 2018
  22. SoCal RV Flyer

    SoCal RV Flyer Cleared for Takeoff

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    I used this beauty for weighing my plane. About $39 through Amazon; called the EatSmart scale.

    51HUjHyXxUL.jpg

    To check for accuracy, I loaded it up with different combinations of barbell plates of known weights, and across the board the weights were close to spot-on and repeatable to +/- 0.2 lb or so. A lot better than old school bathroom scales, for sure!!

    Max capacity is 400 lb., which worked out perfectly as I weighed the plane without fuel, and the mains came in at about 385 lb. per side, IIRC, and the nosewheel was in the 285 lb. range. I'm lucky my aircraft is pretty light. :)
     
  23. denverpilot

    denverpilot Taxi to Parking

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    I’m sure American has their cap process documented in their Ops docs approved by FAA.

    Not sure my mechanic is going to sign his name on a new W&B done with some scale some cop showed up at the hangar with our of his trunk.

    LOL. Hell if I know. Know what I do know? If I ask my mechanic to weigh the plane, he and his staff will take care of it with whatever tools and documents they’re supposed to. I don’t have to call the State Patrol and ask to borrow scales or anything.

    Amazing. Go figure. :)
     
  24. Paulie

    Paulie Ejection Handle Pulled

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    Yeah amazing. What's your point? I'm rebuilding a Mooney for my brother, as a IA I'll borrow the scales front my friend that owns a crop dusting service. I'm going to trust the stickers. I'm the one signing it off. I forget that people without any actual maintenance experience post on this thread.
    When I was at AA I've had the feds ask to see the sticker on a torque wrench I was using, never had them demand paperwork to back it up. As I said the ones troopers used have been challenged in court I'm sure, what would be their reason to put a bogus sticker on something? I guess some people argue for the sake of it.
     
    Last edited: Jan 11, 2018
  25. denverpilot

    denverpilot Taxi to Parking

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    You have the luxury of signing anything you’d like to sign. Don’t be an ass and assume anything about anyone else’s maintenance experience, however.

    Just because people can’t work on airplanes without a $10,000 piece of paper (and many who have that paper work on them, poorly, quite frankly) doesn’t mean a whole hell of a lot about maintenance experience on anything.

    You want to go borrow the local cop’s scales? You have that option. Most of us live in a world where the airplane goes to a mechanic with the special piece of paper and we don’t worry about such things.

    My airplane mechanic charges less than my diesel mechanic, he just gets to charge stuff more often. The tractor mechanic is the expensive one. Just sayin’. I wouldn’t own any of them if I was balling at paying the bill. They’re tools to get certain things done.

    The airplane’s job is mostly to put a smile on my face. Calling State troopers and asking for scales? Waste of valuable smile time. The mechanic can call them if he likes, I don’t care.
     
  26. Paulie

    Paulie Ejection Handle Pulled

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    Why are you beating this to death?
     
  27. denverpilot

    denverpilot Taxi to Parking

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    I respond when responded to. Little app on the iPad goes ding. It’s nifty. High tech.
     
  28. Paulie

    Paulie Ejection Handle Pulled

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    Denver you made my ignore list, you can give it up. Sheesh.
     
  29. denverpilot

    denverpilot Taxi to Parking

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    My life will be truly and deeply affected. Three decades of online message boards and someone doesn’t like me. I’m crushed. I honestly feel deeply enriched by the knowledge that I can call a cop to weigh my airplane in Texas. How will I ever survive without you?

    Was there any particular reason you needed to make an announcement about it? The button works without commentary, you know. Scroll wheel works, too. More high tech. Amazing stuff.
     
  30. sferguson524

    sferguson524 Cleared for Takeoff

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    I still like you Nate :)
     
  31. denverpilot

    denverpilot Taxi to Parking

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    Awww. PoA lovefest.

    I like you tooooo....er, um..., pizza.

    If you break out the Barry White CD, I’m leaving, however.
     
  32. sferguson524

    sferguson524 Cleared for Takeoff

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    LOL.
     
  33. SkyDog58

    SkyDog58 Final Approach

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    Yes, the FAA guy will ask the floor mechanic to show him the cal date sticker on a calibrated tool he is using. He will not ask the mech for the cal certs. He will however, ask the accountable manager, DOM, tool room manager or other relevant personnel for those certs.