Ever fly with plane overloaded? Experiences?

Discussion in 'Lessons Learned' started by LongRoadBob, Apr 30, 2017.

  1. Salty

    Salty En-Route

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    You guys seem to be confusing CG in flight with the moment created by the wheels being on the ground in a taildragger. They are not the same thing.

    Or maybe I'm just confused by the conversation.

    At any rate, weight behind the wheels, but in front of the CG is going to make the tail harder to lift when the wheels are on the ground, but will actually make it easier to lift the tail when the wheels are off the ground. This is because the plane doesn't rotate around the CG when the wheels are on the ground (it rotates around the wheels), but it does in flight.
     
  2. Mtns2Skies

    Mtns2Skies Super Moderator Management Council Member

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    There's no "you guys" there's only one here that has that confusion.
     
  3. Salty

    Salty En-Route

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    Sorry, I'm even confused by who has what confusion. ;)
     
  4. flyingcheesehead

    flyingcheesehead Touchdown! Greaser!

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    Read what I was replying to, which is quoted right there in my post:

     
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  5. Stewartb

    Stewartb Final Approach

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    Let's use Mtns2skies' Skywagon as an example. Do a sample loading sheet with as much weight as you want as far aft as you want. Let's assume we use 50 gallons of fuel. We identify the CG in calculated inches aft of datum, right? That's the fulcrum in the see-saw cartoon, right? The fulcrum varies with weight and station, right? That's why we do W&B to assure the fulcrum falls in the acceptable range, right? Remove 30 gallons of fuel from the load calcs and what happens? The CG moves forward toward the datum. That's why many W&Bs plot a zero fuel weight as well as a take off fuel weight, to account for the change. I've never seen my zero fuel weight CG move aft. It always moves forward in my planes.

    If you don't like the wheels example you can do a similar demo using pitch trim in slow flight, like on final. Some Skywagons are right on the forward CG line when flying solo with minimum fuel. Add fuel and the fulcrum slides aft. Fly a Skywagon on Fluidyne hydraulic skis and you get very familiar with the forward CG thing and how to manage it.
     
  6. Tantalum

    Tantalum En-Route

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    Not me. Someone else is confusing datum with CG and how a taildragger behaves when you put stuff in it.
     
  7. flyingcheesehead

    flyingcheesehead Touchdown! Greaser!

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    Uh, what he said. The datum is an arbitrary point. If you wanted to, you could change it, if you did the appropriate calculations.

    Some planes use the tip of the spinner as their datum, so clearly it would be impossible to have a tank in front of the datum. Do you think that means you couldn't have a forward CG on those planes?

    Now, if you want an example of a plane with a tank in front of the datum, I'll point to the venerable (and common) Piper J-3 Cub. There's a tank in front of the cockpit, while the datum is the leading edge of the wing.

    As opposed to "old engineer syndrome" which means you think you're right because of your experience, even when presented with evidence to the contrary, and you point out your experience as an argument instead of actually discussing the specifics of the subject at hand? :dunno:
     
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  8. mondtster

    mondtster Pattern Altitude

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    I can tell you that the Husky I did my seaplane rating in did. I was surprised to see that the CG moved aft when I calculated it.

    It was a topic of discussion during the oral portion of the checkride.
     
  9. Clark1961

    Clark1961 Touchdown! Greaser!

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    Naw, as opposed to being practical and reading the rest of the presented material to know what is relevant, not just “evidence”.
     
  10. Salty

    Salty En-Route

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    Yes, I see that there is also a fundamental misunderstanding of the datum line, which is surprising since it's a building block needed to get through your PPL.
     
  11. Tantalum

    Tantalum En-Route

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    ^yeah. It's imaginary.. you could place it 5 miles in front of the plane if you wanted to. Or like someone said above the spinner.
     
  12. Stewartb

    Stewartb Final Approach

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    Datum is a reference point. In my 180 the standard envelope is +38.5" to 47" and my empty CG is 40.64" aft of datum. The pilot seat station is 36". Fuel is 48". Passenger seats 70". Baggage area 95". Extended baggage 120". Useful load is around 1500# and all but the front seaters is behind the aft limit, so one can surmise that the plane is nose heavy when empty. I can manipulate load numbers with varying fuel quantity and reduction in fuel always moves the CG forward, as I'd expect given the aft limit-fuel station relationship.

    With a typical load of myself, wife, dog, 170# of cargo, and 40 gallons of fuel my CG is 43.86". Burn off 30 gallons with no other changes and my CG is 43.56. I can run variations of the loading all day and the reduction of fuel will move CG forward every time.
     
  13. Salty

    Salty En-Route

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    Your fuel is behind the CG (48 is behind 40.64), burning it off moves the CG forward (43.86 to 43.56 = CG has moved forward).
     
  14. wilkersk

    wilkersk Cleared for Takeoff

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    I think the statute of limitations is probably up on this. Once upon a time, long ago, a flying club manager tasked me to go pick up an IA from another nearby airport.
    He didn't tell me the IA weighed about 350lbs. He was so big, he had to put the seat all the way back, and scrunch down and lean in. I was kinda pressed against the pilot side door of the little 152, sure the door was gonna pop open. I'm positive that with the 2 of us and a full bag of gas we were well over max gross.

    When I voiced my concern, he said,"son, its a 5,000' runway and a cool morning. Just fly smooth and keep it below Va and we'll be fine. The boys up in Alaska do this all the time." Being a young and dumb, low-time pilot, I figured he and the manager must know what they're doing. We made it OK. And, it was a learning experience. Because after that I decided to learn everything I could about weight and balance, and how it was those "boys up in Alaska" were getting away with it.

    Bottom line, its not worth it. I'm not getting paid anything, let alone enough. So, why take unnecessary risks.
     
  15. Fearless Tower

    Fearless Tower Touchdown! Greaser!

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    Yup. It can happen in the Beech 18. If you have fuel in the Aux tanks and burn fuel from the Mains (which you are supposed to for at least the first 45 min) the CG will indeed move aft.
     
  16. BillW

    BillW Filing Flight Plan

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    Probably just due to moisture absorbed by the feed after packing.
     
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  17. zaitcev

    zaitcev En-Route

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    In my Carlson, half the fuel is ahead of the wheels even, let alone the in-flight CG. Guess what happens when it is consumed. The other half is in the wings. People really like to make assumptions in these threads. Also! The tail does not lift? That's the oldest, stupidest misunderstanding that pilots still cling to. Poor Denker even attached streamers to the tail of a 172 to prove that its tail may both push down _and_ up, depending on where the CG is within the approved envelope. And they are still sure that tails do not lift.
     
  18. Mtns2Skies

    Mtns2Skies Super Moderator Management Council Member

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    I understand that tails generate lift. I was referring to the fact that Stewart said you pick up the tail to determine CG. The plane does not lift itself in flight from the tail but rather from the center of pressure which is over the wing and has nothing to do with the wheels or tail.
     
  19. Stewartb

    Stewartb Final Approach

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    The tail is what you use to control the AOA, which is what you manipulate to get the plane to take off. Go fly with minimum fuel. Pay attention to control feel and trim settings. Then load the plane to gross with a normal weight distribution. Tell me you can't feel it in the tail when taking off. You absolutely can. Because every ounce you put into that airplane moves the CG aft. What you recognize at takeoff applies to landing, too. Fly it over gross? If you don't maintain a little extra airspeed to landing the tail may drop as you get to your traditional landing speeds. You're used to holding a little back pressure to landing. Wait til the tail drops unexpectedly. You won't be ready for it. Flying floats is another great way to learn about your airplane's loads and CGs.
     
  20. Mtns2Skies

    Mtns2Skies Super Moderator Management Council Member

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    What you're talking about is the total weight of the airplane... not the CG. They're different things. I still give up.
     
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  21. Tantalum

    Tantalum En-Route

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    Just to recap
    *there was a debate that CG will always move forward as you burn fuel. To prove this point, someone talked about picking the tail on their tail dragger up with and without fuel and how much force that takes

    ^While most planes do move the CG forward as fuel is burned, that is not a universal rule for all planes. Some planes, like the Glasair, actually move the CG aft as fuel is burned. Fearless Tower also stated that there are configurations where the Beech 18 will also move the CG aft as fuel is burned

    It all comes down to the specific airplane and where the fuel is located and how changing that weight moves the CG forward or aft. It sounds like in Stewart's plane the CG always move forward as fuel is burned
     
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  22. Checkout_my_Six

    Checkout_my_Six Final Approach

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    yup....it depends. o_O
     
  23. Mtns2Skies

    Mtns2Skies Super Moderator Management Council Member

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    No. Stewart believes that the main landing gear on his airplane is the CG. That is false.
     
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  24. Stewartb

    Stewartb Final Approach

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    What happens to YOUR Skywagon's CG when you add gas, passengers, and cargo? Plot it in an envelope. Don't give up til you get it right!
     
  25. Mtns2Skies

    Mtns2Skies Super Moderator Management Council Member

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    That's irrelevant. The point is... if you add weight behind the main gear of the plane the tail will feel heavier while the main gear is supporting the plane. That has NOTHING to do with the CG of the airplane in flight - because the wings support the airplane not the landing gear. The wings are in a different location than the landing gear.
     
  26. Tantalum

    Tantalum En-Route

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    No. That might be true on your plane, when it is on the ground, because the main gears are well forward of the CG.. so the heavier it is the more initial force it takes to get the tail off the ground. But there are plenty of configurations I could have in a Cirrus where adding weight will move the CG FORWARD.. or AFT

    The front seats, rear seats, front and aft baggage, fuel, etc., all have their own stations with regards to the reference point and the CG. It comes back down to the seesaw thing someone else posted. Put more weight ahead of the CG, the CG moves forward. Put more weight behind the CG, the CG moves back

    Imagine a 747 with only the front half of the plane loaded, vs only the back half.. the CG will be dramatically different in either case. Definitely not true that every ounce you add will move the CG aft.
     
  27. denverpilot

    denverpilot Taxi to Parking

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    To elaborate, the main gear is just a fulcrum point when lifting by the tail. It’s not related to CG at all. When he adds fuel to the tanks it’s essentially at the same station as the nearly empty tanks are.

    It just makes lifting the tail harder because there’s more weight aft of the fulcrum point at the wheels. It’s not necessarily a change (much) in CG at all.
     
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  28. Tantalum

    Tantalum En-Route

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    Yep. I figured that out when I read more of the thread and posts after hastily posting my reply. I didn't realize that we were this far off track confusing landing gear and how easy or hard it is to pick the tail up on the ground on a tail dragger when you load it up

    there was a reason I stopped following this tread back in April..

    This really isn't that hard to grasp. I feel like I am being trolled. That soccer ball in the picture below is the center of gravity, with the shaded area the for and aft limits. Start putting things (people, baggage, fuel, cinder blocks, whatever) in front of that ball, it moves forward. Put it behind the ball, it moves back. That's it.

    Note that the landing ear is in front of the CG, that's obvious, otherwise the plane would fall on its nose on the ground.

    #disappointed
    upload_2018-7-11_13-52-6.png
     
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  29. Stewartb

    Stewartb Final Approach

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    You guys are making it literal. Fine, the wheels are indeed ahead of the datum, so ahead of the CG. Is there a fulcrum in play? Absolutely. But let's be practical. In a Skywagon everything you put into the plane other than the pilot moves the CG aft. Including fuel. I can move my load fore and aft and manipulate the CG from central to aft limit. Can I judge that difference at takeoff? Yes, I can. And after 20 years flying the same plane I know pretty well how the plane is going to react to control inputs and how it's going to perform from the feel on the elevator.

    Probably the best teacher about the subtleties of CG is float flying.
     
  30. Stewartb

    Stewartb Final Approach

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    But earlier in this thread it was stated that burning off fuel moves the CG aft in a Cessna, and that's incorrect. THAT's where all this started.

    If a Skywagon's aft CG limit is 47" and the normal fuel station is 48".... what happens to the CG as fuel is burned off?
     
    Last edited: Jul 11, 2018
  31. denverpilot

    denverpilot Taxi to Parking

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    I understood that. That’s why I elaborated on why the anecdote about lifting the tail was completely irrelevant to the CG.
     
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  32. Capt. Geoffrey Thorpe

    Capt. Geoffrey Thorpe Touchdown! Greaser!

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    Pitts, older Cubs, T-18 come to mind.
     
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  33. eman1200

    eman1200 Touchdown! Greaser!

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    what if your skywagon was on a treadmill and you raised the incline angle?
     
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  34. mtuomi

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  35. Salty

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    This sentence implies reasoning that isn’t sound. It implies that if the wheels are ahead of the datum, they must also be ahead of the cg, which is not true.

    I think you have an aversion to using terms accurately. I also have this affliction, but it’s important in a discussion like this to do so, or nobody will understand what you mean without pages and pages of explanation.

    The datum is an arbitrary point, chosen with no relationship to the cg, center of pressure, location of the landing gear, etc. It can be anywhere.
     
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  36. Stewartb

    Stewartb Final Approach

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    I was addressing a Skywagon comment. If you can paint a scenario where the CG is ahead of the wheels? You have a problem.
     
  37. Salty

    Salty En-Route

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    Any tricycle gear airplane.
     
  38. overdrive148

    overdrive148 En-Route

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    Thanks Kerbal Space Program!
     
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  39. denverpilot

    denverpilot Taxi to Parking

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    ????

    Fun game, and it does have that little ball indicating where the CG is...

    But not sure what you’re saying? Just that you can change loadings and stuff and see it not move in the game?
     
  40. overdrive148

    overdrive148 En-Route

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    Solving the "why the hell won't my airplane rotate I'm pulling the stick all the way back" problem with the gear location, center of mass, and center of lift in KSP was a blast.
     
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