Tail Weight 46 BC12D

[PA1195]

The Gilberti/Harer/Bowden/STC and TCDS 1A9 create a new range of loading and handling options versus to original type designs. There's maybe something for discussion here regarding that I believe. Something like an analysis of plus and minus factors and why. Is anyone interested in offering some analysis and comments? All I've heard from previous threads and posts is one flys differently from the other and that's bad or at least different enough to note.

I'm suggesting a new topic with actual data and cause and effect. Engineering guys are you available?

Gary

[swift1b]

Gary

I think you suggestion re: actual data-cause and effect is an excellent idea and be of great benefit.

I remeasured the TCraft and there were some measurement off (less) which resulted an a CG of 19.18 (the previous CG was (19.46).. Better but still out of range.
I will continue to review with additional W&B to hopefuly find the reason for the difference.

[PA1195]

It's a challenge trying to visualize over the Internet a remote W&B and equipment list for your Taylorcraft. Maybe Bob you could offer examples for your plane...copies of each plus any modifications and a description or pictures? Things installed to the front and rear of the Datum that might contribute to a rear CG. Any repairs or changes to the basic aircraft after it left the factory? Is there a hunk of ballast in the tail?

Do you have the FAA's records from first build that may help determine how you got where you are? http://aircraft.faa.gov/e.gov/ND/

Gary

[swift1b]

Gary

Thank you for suggesting reviewing the past records. Fortunately the TCraft was restored in mid 80's by a professional who also researched and bound documents all the way back o the factory. If needed I will get the records on Cd from the FAA as I have done before for my J35 Bonanza, Globe Swift and other aircraft. With that being said I appreciate the many comments concerning the methods to use for a TCraft.
The reason I started on the W&B quest was to make certain it was done and found to be within the required parameters before I loan it to my young friend to get his TW endorsement and then build time tor his commercial. I will pursue this request with the utmost tenacity until I work out the problems.
.

[PA1195]

Bob your concerns for another who will fly your plane are well founded. I hope the apparent aft CG issue is resolvable and the other pilot can eventually fly a legally loaded and airworthy Taylorcraft. If anything happens during flight training the inspectors will investigate and then nobody happy.

Gary

[swift1b]

Gary

I agree with your wisdom. I feel competent in aircraft W&B calculations but I am open to any advice offered. I have been flying since 1956. Got my private in my first airplane 46 BC12D in 1957.Additionally I was a Civil Engineer/Surveyor for 40 years and know that there is a great deal to consider when making horizontal measurements. Before the advent of Laser technology/Total Station Transits we use a 100.00 foot steel chain..to acquire the required accuracy the chain had to be held horizontally with plumb bobs at each end over a tack..a pull type scale was used to pull the required amount to correct for sag.. followed by the recording of the outside temperature when the measurement was taken. These allowed for a corrected measurement..the steel chain would be longer or shorter..depending n the temperature. I am confident that I will find the cause for my particular W&B .being out the required limits. Once I get the correct W&B for my 46 BC12D my son, also an engineer will create an XL spreadsheet that I will share.

[Scott]

I think this (from the BC12D TDS) is what I was trying to remember with respect to CG range:
(I removed the references to floatplane for ease of reading)

"Center of Gravity (C.G. Range) Landplane: (+14.2) to (+20.0)

Empty Weight C.G. Range Landplane: (+14.8) to (+17.9)

When empty weight C.G. falls within pertinent range, computation of critical fore and aft
C.G. positions is unnecessary. Ranges are not valid for non-standard arrangements."

The last paragraph is what I was referring to. I can't say that I'm completely certain what it means in practice but it does seem to contemplate empty CG aft of 17.9".


My Empty wt CG is 17.7". There is nothing other than an ELT, a couple of antennae (about 3lbs but partially offset by a fire extinguisher fwd of the CG), and some tubing splices that is non-oem about my BC12D/W&B.

761 pounds on the mains and 65 pounds on the tailwheel (stock tail wheel at station 198). Empty weight 822 after netting out 4 Lbs for oil.

At Gross weight, with wing and main tank full, max cargo of 50lbs CG is 18.17"

With half the fuel burned from the main tank, CG is at 19.1" this is the point where we're supposed to transfer fuel. After transfer, as fuel continues to burn off CG continues moving aft until at 1 gal remaining CG is 19.6" This would be the worst case scenario, in terms of the CG moving aft.

However if your Empty weight CG is aft of 17.9, it's obviously easier to exceed the loaded aft CG during flight. So you need to calculate this "critical" aft CG position with half main and full wing at or near gross. If you have two wing tanks I suspect it would be quite easy to exceed the aft CG limit. This is what the TDS is drawing attention to (I think) with the note about critical for and aft CG positions.

[PA1195]

My BF/BC12-65 was modified via Gilberti/Harer/CAP STC SA1-210 to the equivalent of a BC12D-4-85. Gross weight land 1280# with 1500# optional when moved to the equivalent of a Model 19.

For the BC12D-4-85: C.G. range (+14.2) to (+20.0); E.W range (+14.9) to (+16.3)

Mine from factory 6/41 as BF12-65: Left 345#; Right 348#; Tail 56#; C.G. 16.5".

Currently after a few changes: Left 398#; Right 389#; Tail 47#; C.G. 14.26". Datum to tailwheel 199.4. Moving the engine with light weight starter, alternator, metal 74" prop -4" alters things.

Gary

[N96337]

Mine from factory 6/41 as BF12-65: Left 345#; Right 348#;

Currently after a few changes: Left 398#; Right 389#;
Gary

I just weighed a Champ the other day and it was 13# heavier on the right main than the left. He's had this Champ down to bare bones in the past year and I sure never saw ANYTHING that could make it weigh so heavy on one side.... I've run into that a few times. Just gotta shake my head and walk away!
John

[Hank Jarrett]

Remember you are talking about "ARM" side to side just like front to rear. It doesn't take much weight at the wing tip to get a 13# weight on the main tire (which has a VERY short arm!). Very few planes are balanced well laterally.

Hank

[PA1195]

My Field Approved Odyssey battery sits a bit to the right in the rear baggage. It's wiring going forward does as well, and it's placed more forward in the baggage area behind the front seat. The SA1-210 STC calls for a more rearward battery location like the F-19's had. That probably contributes to the lighter tail in mine. But regardless when loaded with full nose fuel the rest of the load weight migrates aft.

With me (200#) and full front fuel 12 gal (72#) the weight is 1106 and C.G. 14.3" the most forward C.G. possible. Forward limit is 13.4" at 1200# or less.

With me (200#) minimum front fuel [METO horsepower of 85/2] = 7 gal (42#) rear baggage (50#) full wing fuel 12 gal (72#) dog on front seat (52#) front floor baggage (27#) I'm at the most rear C.G. possible 17.3" at a G.W. of 1280#. Rear C.G. limit is +20.0".

Gary (math is close enough)

[astjp2]

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!

Rob, if all of the possible load configurations keep the airplane within the CG limits, you don't need to calculate for every flight, that is written in an AC somewhere.

[Robert Lees]

Rob, if all of the possible load configurations keep the airplane within the CG limits, you don't need to calculate for every flight, that is written in an AC somewhere.

I believe that you (and Scot) may mis-understand the TCDS, and sorry if I am wrong, but here goes: It's not in an AC somewhere...it's in the TCDS

TCDS A-696 says:
"When empty weight C.G. falls within pertinent range, computation of critical fore and aft
C.G. positions is unnecessary. Ranges are not valid for non-standard arrangements."

What this means is that if your empty weight Centre of Gravity lies within these limits, then as long as you do not overload the aircraft in terms of weight (i.e 1200lb), you can never exceed the fore of aft limits of the in-service Centre of Gravity limits. So as long as for every flight you are under 1200lb, you are within the CG range for all flight situations.

The situation with our friend is that his empty weight CG position is NOT within this range...that's why the TCDS says "Ranges are not valid for non-standard arrangements"

Rob

[swift1b]

Well... I have taken new measurements and found the distance from the DATUM to center of tailwheel axel is 198 inches. 1 inch more than the factory dimension of 197 inches. This is probably due to the Alaska Bush tailwheel I installed. I found the reason my previous measurements were off due to a cloth engineering tape that had shrunk over the years! My steel tape made the difference.
And that being said... I agree that the Factory CG data does not apply if changes have been made. The factory CG was with a wood prop.. I have a McCauley that was installed in the past that certainly cause a different CG range...

[Hank Jarrett]

NO, NO, NO, NO!!!! The metal prop DOES NOT change the acceptable CG range! It moves the CG forward but you still have to stay in the same CG range on the aircraft!