Gross Weight Increase

[smmilke]

I am about to purchase a BC12-D that has the Harer STC: C85, extended baggage, rear windows, sky light. The weight and balance currently shows a 1200 or 1280 # gross and I don't need to worry about my medical so I would like to get this bumped up to 1500#. I did a little research on the old threads in the forum, but I didn't find a definitive answer as to ho this works. The type certificates for the BC12D-85 and BC12D-4-85 look like the gross weights are 1280 with 50#'s in the baggage. The model 19 looks like what I'm hoping to bump things up to, 1500 gross and 72# baggage. I guess the big question is, beyond the Harer STC what is needed for a mechanic to sign off the gross of an originally BC12-D to 1500# gross. Is it possible to convert a BC12-D to a model 19? The serial number on the airframe is 7212 and so I think this would rule that out. Any info would be greatly appreciated!

[Jim Herpst]

Re: Gross Weight Increase

If it has ALL the mods of the Harer including the wing fittings and electrical system then it should already be bumped up . If not that is strange. The STC spells it out.....

[magman]

Re: Gross Weight Increase

It will stay a BC12-D.

The upgrade could make it equivalent to a Model 19 , or?

Personally; I would be a little sceptical if a conversion was "done" & the Weight & Balance portion was not addressed.

As Jim Herpst pointed out the GW should have already been addressed.

Any A & P wanting to raise the GW will want to VERIFY that all modsto do so have really been accomplished.

Best get your Tech on board with this BEFORE you buy.

[smmilke]

Re: Gross Weight Increase

I've read a lot about the engine mount being a factor in the gross weight. Does the Harer STC call for a long mount when the c85 is installed or are they regularly certified 10 1500 without the long mount? I talked to the previous owner about doing the conversion, but didn't think to ask why he didn't have the gross weight increased on paper, I think it was done well before light sport came to be so this is a little strange. I didn't know the Harer STC called for an electrical system, this has very basic wiring for an electrical system but no starter, alternator, battery, etc. at this point.

[Robert Lees]

Re: Gross Weight Increase

For 1500# you DO need the long mount (and new/modified cowls to suit). Otherwise you are limited to 1280# with the original 50lb baggage allowance (and in theory the small baggage sling/compartment).

Welcome to the forum!

Rob

[smmilke]

Re: Gross Weight Increase

That's what I was afraid of. I am not sure if this plane has the long mount or not. I can take a look, what should I look for to determine if it is a long mount? Is the typical thing to do during the conversion to use the long mount rather than the short? Also, what do you mean by small baggage sling/compartment; is that just a reference to the original baggage area setup? Thanks for the help.

[barnstmr]

Re: Gross Weight Increase

Shaun,
I am the STC holder. Mr. Lees is correct. However, I want to point out some things that I recommend you should be aware of. It does not matter a whole lot whether the maximum weight is 1280 or 1500 when it comes to the possibility of having your CG out of whack. If the airplane has a large extended baggage compartment but does not have the 4 inch extended engine mount, you should be very careful about aft loading and aft CG. At 1280 or 1500, (either way) it is possible to load that baggage compartment and cause an unsafe CG. I highly recommend that you check into that. Quite a few things go into the loading scenario. But it isn't too complicated. Things such as starter/generator/metal prop/battery location etc.. have an effect on the CG. Mr. Gilberti established the STC for the -12 engine with a metal prop and Prestolite starter and Delco generator... the heavy-weight ones... on the engine which was located 4 inches ahead of the original A65 engine placement. To offset all of this, he specified a battery at a certain location and gave the extended baggage compartment provision.

These days with light weight starters, alternators, and batteries, you really have to assess each airplane individually to make sure the combination of equipment is appropriately installed to keep your CG in check. I would suggest to have your A&P weigh the airplane and compute the empty CG on this airplane then go from there in making any decisions about whether the weight and balance is correct.

[smmilke]

Re: Gross Weight Increase

Thanks for the input Terry, I plan to have the airplane weighed and get the WB updated so I know exactly what I'm dealing with as far as loading is concerned. I understand that the max baggage figure is simply a max load and that loading to this weight is not safe in all situations. I am just as concerned with staying safe as I am staying legal. I just don't want to ever have to worry about getting ramp checked and getting dinged for being loaded within structural limits but not paper limits. I found some pictures of long and short mounts in some old threads and I will check what this airplane has before I buy it in hopes of getting the gross weight raised.

[avenger1949]

Re: Gross Weight Increase

Thanks for the input Terry, I plan to have the airplane weighed and get the WB updated so I know exactly what I'm dealing with as far as loading is concerned. I understand that the max baggage figure is simply a max load and that loading to this weight is not safe in all situations. I am just as concerned with staying safe as I am staying legal. I just don't want to ever have to worry about getting ramp checked and getting dinged for being loaded within structural limits but not paper limits. I found some pictures of long and short mounts in some old threads and I will check what this airplane has before I buy it in hopes of getting the gross weight raised.

My Tcraft has the long motor mount all electrics and lights, metal prop, 85 hp cont, and all the other things that make it the 1500 plane but in the A&P papers it says it was done completely without a request for the weight upgrade. Which right now I am happy about since I only have a light sport license. Does say the battery was located to make the plane come into W&B. Was this something that was regularly done as it appears in the paperwork that an increase in weight wasn't requested?

[barnstmr]

Re: Gross Weight Increase

The STC # SA1-210 has two options (A or B) as shown in the attached photo. Summarizing, the STC says this...
A. Equivalent to BC12D-85 (per TCDS A696) which has a C85-8 and 1280 max wt.
B. Equivalent to BC12D-4-85 (per TCDS A696) which has a C85-12 and 1280 max wt. or Model 19 (per TCDS 1A9) which has a C85-12 and 1500 max wt.

Some airplanes have the STC with deviations that were approved under a 337. Airplanes which have the STC # SA1-210 but 337 approved with a different engine model than shown on the TCDS or with a different max wt. are NOT equivalent. Therefore, they do not comply directly with the STC. This means a separate approval must exist to properly document this deviation from the STC.

I have seen all kinds of configurations and very few that are actually "equivalent" to the factory BC12D-85, BC12D-4-85, or 19.