Tail Weight 46 BC12D

[Robert Lees]

Robert,

Check out the attached advisory circular, chapter ten starting on page 51 will help you. The file is a portion of AC43.13-1b.

Dave

Is that aimed at me Dave?

[Guest]

Is that aimed at me Dave?

No, sorry for the confusion. the man that started the thread and asked the question is also named Robert.

My bad, sorry.

Dave R

[astjp2]

I posted a whole advisory circular on weight and balance, go to the references section, that is why I post things there! Tim

[swift1b]

So..Hank. I weighed the tail with the aircraft level using a carpenters level on the horizontal stabilizer. The weight: 68.8 lbs. I have the Alaska Bush tailwheel which adds a few extra pounds. Dave's weighed 70 lbs so I must be in the ballpark!

[Hank Jarrett]

Same ball park, but remember that number DOES NOT tell you where the CG is! Is 68.8# what your W&B says from the last time? If not, I would do a weighing and make up a new W&B sheet.

Hank

Actually I would do a new W&B any way, but I kind of enjoy doing that kind o stuff. ;-)

[swift1b]

Well, I used a plumb bob yesterday hanging it from the leading edge with aircraft level. The measured distance from the plumb bob string (Datum} to the center of the tailwheel with the the measuring tape level and I got 201 inches. I assume the is due to the
scott 3200 Alaskan Bush Tailwheel? Any thoughts as 197 inches is the norm?

[Robert Lees]

Could be. The original length between the datum (leading edge of wing) and the centre of the axle of the tailwheel was in the order of 197 inches or so. Most vagaries to this "nominal" dimension are due to either improper leveling, or different lengths of tailspring. The original length was when the Taylorcraft had a tailskid!

To be honest, a half- inch here or there, or a pound weight here or there is not going to make a flight safety issue. It's gross aft-tailweight that can cause an issue.

When I do a W&B (on any aircraft), I do it to the best of my ability, and I sign the form...that becomes legal data but only for that particular aircraft.

[Hank Jarrett]

Also make sure when you drop the plumb from the LE of the wing you do it from BOTH SIDES AND DRAW A LINE BETWEEN THEM! The distance to the tail wheel contact point is from a point on the datum ON THE CENTER LINE OF THE FUSELAGE!!! I had one guy who was measuring from the main gear tire. THAT WILL GIVE YOU A LONGER TAIL MOMENT!!!

[Scott]

beg to differ with you Hank... all the distances must be horizontal. The easiest way to do this is to simply plot all the distances on a level floor below a level aircraft.

So, drop your plumb bob from the leading edge, mark station zero on the floor. Drop the plumb bob from the tail wheel axle (or any other location), mark the floor. Measure the distance between your marks. This is the arm.

Note that all else being equal, the longer the tail wheel arm, the lower the weight on the tail wheel. This is why the "weight of the tail" in and of itself really doesn't tell us anything.

[3Dreaming]

Scott, I think you and Hank are saying the same thing.

Here is what I do. I level the airplane on a level floor. I then drop a plumb bob from the tail post and the center of the firewall to mark the centerline of the airplane. I then drop the plumb bob from the leading edge on both wings, and strike a chalk line across between those points crossing the center line. I do the same for both axles. I then drop a line from the tailwheel, and use a square to transfer it to the centerline. Once this is done all measurements come from the centerline.

BTW when I am doing the measurements I use an engine hoist to lift the tail, so I am not having to work around a tail stand.

[swift1b]

I am getting 19.46 as my "Empty WeightCG Position". The TCraft Manual gives the CG range of 14.8 to 17.9.. I plan to remeasure the the distance from Datum to TW center today to make certain my measurements are correct. Should I be concerned about the 19.46 CG? I noticed the spreadsheet for N39240 shows 14.2 - 20.0.

[3Dreaming]

If you have an airplane that is outside of the empty weight CG range you need to pay closer attention to your CG calculations. Don't just figure the take off CG, but also figure the landing CG. It would be possible to take off with the airplane within the CG range close to the aft limit, and have the airplane move outside the CG range while in flight. If the airplane is within the empty weight CG range you don't have to worry about that.

[Robert Lees]

I am getting 19.46 as my "Empty WeightCG Position". The TCraft Manual gives the CG range of 14.8 to 17.9.. I plan to remeasure the the distance from Datum to TW center today to make certain my measurements are correct. Should I be concerned about the 19.46 CG? I noticed the spreadsheet for N39240 shows 14.2 - 20.0.

I would be concerned...not just because as 3Dreaming says, you have to do an accurate W&B for every flight, but also because I'd be asking: "why is the empty weight CofG so far aft?" Let us know the result of your re-check of the tailwheel arm. Another issue is not using a level floor, and not levelling the aircraft properly. As you know, the levelling datum is the horizontal stabiliser...has the tail ever been repaired?

We have one UK BC12D that was imported from the USA in the late 80s...an unknown restorer in the USA had used EMT steel conduit for the stringers, and had welded in a huge steel seat frame! I weighed it in 2013 and the empty weight was 874lb, with the tailwheel weight being 76lb at 198 inches!

It effectively made it a single-seater!

[Hank Jarrett]

Scott, we are saying the same thing. When i said I had a guy measure from the main contact point I was saying he thought the tail moment was from ONE of the mains to the tail. That was farther than from the point BETWEEN the main contact points on the center line.
Just for grins and giggles when I did my W&B I also did a LATERAL CG to see if the CG was on the center line of the fuselage (it wasn't) and I also did a tail down CG to be able to calculate how high UP the CG was (don't even remember how high up it was and I will probably do it again just out of curiosity).
I also did CG measurement with a weight in the baggage sling to see if the factory moment was correct (it was) and weighed with full fuel in the nose and empty just to see if the fuel moment was right (it was very close).
All of these measurements really only taught me one thing. Don't leave an engineer in a hangar on a rainy day with no tools. It was still more fun than watching TV.

Hank

[Scott]

Glad we cleared that up!

Re aft CofG... the futher aft the empty CofG is the more attention you need to pay to loading. Pretty much everything you do in normal operations moves the CofG aft. Load moves CofG aft. Burning off fuel & oil moves it aft. Seems to me there is some additional requirements (perhaps in the TDS?) if the empty CofG falls to far aft.