I'm getting ready to weigh my 180 & do a new W&B. I'm curious what everyone else's C180 empty weight & CG is. How about posting that info, along with a brief description of any weight-changing mods on the airplane? I'm also curious as to the arm of the mains & the tailwheel.

The best way to get the arm for the main wheels and the tail wheel is to level the aircraft by the upper door frame, per the TCDS. Then use a plumb bob hanging off the forward face of the firewall, your reference datum line, and make a mark on the ground. Run a line from the center of each axle to mark the location of the main wheels. Then measure from your reference datum line to the line you ran between your axles, this will be your arm to use for the main wheels. Then measure from the RDL to the point directly below the tailwheel axle to come up with that arm. This is the most accurate way to determine the arm of each location. Also, look at the TCDS and it will specify how much unusable fuel you have to add to your empty weight and wether or not you have to include oil. It is different depending on what year your 180 is.

Follow Rob's instructions for the math. Its actually the only way to do it correctly. Here is a graphic illustrating my numbers.

FYI... ALL C180's should be weighed with only unusable fuel and unusable oil. Although foolish, the unusable oil in most C180s is 0 qts. Arm of the oil is -15. Exceptions are later models where all 12 qts are incl. Some folks weigh it full and subtract, but you should really drain the tanks at the wing root then weigh. (its obviously more of a pain that way, but correct.)

My 66 weighs 1798 on 8.5x10's with an arm of 34.63 weighed on certified scales. Useful is 1392. I can shed another 55lbs on 8.5x6 and no jump seats.



Here are the instructions.

I lied...actually I weighed the airplane yesterday. Leveled per TCDS at the upper door sill, plumbed down the firewall t/w & mains. Weighted including 12 qts of engine oil, and (per the owners manual) 2 gallons unusable (in level flight) fuel (drained at gascolator when level). Regarding weighing wih "unusable" oil, I think it's silly-- IMHO oil is not a variable like fuel people and cargo.
*Correction: I ended up with 1550 on the mains at 18" and 113 on the t/w at 260.7, so
1663 empty with the CG at 34.49". When I typed up the W&B report, I added 5 gallons unusable (30#) at 48", for 1693# and 34.73" CG.
I may have screwed up measuring the arm for the t/w, had to plumb down forward of the t/w then measure back as the t/w was sitting on the scales on a table & a couple milk crates. Gonna hoist it back up today and re-measure all the arms. AND mark them all on the floor in pencil for permanent reference. Ended up with the firewall over the hangar door tracks so used a piece of plywood to mark both that & the mains, so I can't just go back today and re-measure.
I see Renna's arm for the mains is the same as mine at 18, but interestingly his arm for the t/w is 257.75 vs my 255.5. FWIW mine's got the big stinger & 10" t/w from XP Mods. A previous W&B with the stock t/w & stinger indicated 259.7", the W&B from when the XP Mods stuff was installed says 260".

That CG seems fishy... I think you are right and would re-check your calculations. Even if you used 260 as the measurement, the CG would only move to 32.99. Seems like your TW weight is light? Is it possible you dont have the "gear forward" legs? There are some that are 21" aft of the datum. This would make more sense as your CG would be 35+ rather than 32+.

FWIW. My measurement is inclusive of the ABW TW Fork kit and not the stock 3400. Also, my TW weight was 120lbs. That is with rear battery removed, no hat shelf, ultra light ELT, and carbon fiber EB. I do have the STEC autopilot servo back there behind the EB so there is some extra weight.

RE: WB. I would recommended using the type cert rather than the owners manual for the WB info. Note 1. (attached) explains.

Unusable fuel for 180, 180E, 180F, 180G, 180H, 180J, and 180K through S/N 18053000 is 30lbs (5gal.) Weight should be with zero oil.

Unusable fuel for 180A, 180B, 180C, and 180D is 60lbs (10gal) through S/N 1805260. Weight should be with zero oil until after S/N 18052621 and then its full oil.

If you are draining at the gascolator, I assume you using that as zero fuel are adding the "unusable" fuel back in?

Here is note 1. from 5A6. Hope it helps.

When you get your numbers settled. PM me with the info and I will make you one of these....

"Unusable fuel"-- yes, the unusable fuel per the TCDS is 5 gallons. However Cessna figured usable fuel as usable in all corners of the flight envelope-- in other words, nose up nose down, banked left & right, or any combination of these extremes. The owners manual says only one gallon on each side is unusable in level flight. This is why I drained the fuel from the gascolator in a level attitude and figure that the weight includes that 2 gallons unusable fuel.

I hoisted the tail up again today and levelled it. I'm kind of embarrassed, as it turns out I fouled up measuring the arm for the t/w. The mains were correct at 18", but the t/w turned out to be 260.7" instead of the 255.5" I came up with yesterday. I plumbed & measured everything very carefully and marked it out on the hangar floor.

As far as the tail being pretty light at 103, I agree. But the scales (good digital ones, recently certified) don't lie. FWIW this is a 53 model 180 with:
82" Mac prop
K engine
185 gear legs
850 GY's
Double-puck brakes
v-brace
firewall Odyssey battery
BAS jumpseats
aluminum floor extended baggage
HD stinger
10" XP mods t/w
What with the new t/w arm measurement, it works out to 33.03" CG. Still pretty far forward, and still forward of the fwd limit with just me & minimal fuel aboard. Flies just fine though.

It's interesting that the CG range expanded over the years, from the 180's 35.0" > 45.8", to the 180K's 33.5" > 47.0". Any reason's why?

hotrod180 wrote:"Unusable fuel"-- yes, the unusable fuel per the TCDS is 5 gallons. However Cessna figured usable fuel as usable in all corners of the flight envelope-- in other words, nose up nose down, banked left & right, or any combination of these extremes. The owners manual says only one gallon on each side is unusable in level flight. This is why I drained the fuel from the gascolator in a level attitude and figure that the weight includes that 2 gallons unusable fuel.

I've often wondered about the unusable fuel and if it's really accurate. So a few months ago I ran one tank completely dry while in cruise. As soon as the engine started sputtering I switched to the other tank with plenty of fuel. When I landed I filled the tanks. The tank I ran dry took exactly 18.5 gallons, exactly what is supposed to be useable.

My 1962 180E with the following
8:50's
Double puck Cleveland
FWF odyssey
LR fuel
Float fittings
O-470R
84" 3 blade hartzell
No rear seat

Weighs in at 1725.7lbs at 32.38. Also puts me quite far ahead. I'm hoping to help that by going with an extended baggage and putting a good first aid/survival kit in the far back. Currently my tail weighs 100 lbs at 260.3.

David

I don't feel quite so bad about my far-forward CG now. Like I said in an earlier post, it sure doesn't seem to hurt the way it flies. Although I have heard that an aft CG tends to make an airplane cruise faster and also stall slower.

One very positive aspect to the forward CG is that you have a lot more leeway in loading everything (including the kitchen sink) in back. The guy I bought it from usually loaded it to the gills when camping out and he told me it handled just fine that way. Now I know why.

Mine seems to fly great as is. But I've never flown another 180. I've heard the same about aft CG, but I think the planes with move able stabilizers aren't as affected by this as trim tabs.

I really appreciated the wide CG range of the 180 last summer when flying my whole family and a bunch of camping gear to Alaska and back. We sometimes get caught up in the minutia of different mods and years, but in the end any 180 is just such an awesomely versatile airplane.

I have the firewall battery and extended baggage also. It's true that if it's two big guys up front and nothing in the back, it'll be pretty forward CG. I'd rather have it that way than the other way, for sure. I just keep some survival/camping stuff in the extended baggage, which helps a lot. I appreciate the empty forward CG when flying my family, which is the whole point of having a 4-seater for me.

1768lbs at 34.45 cg for me in my 58 180B on 29" BW's. Just weighed it yesterday after adding the wing X.