More Harer STC questions

[Dano"T"]

We keep beating this up but...I have a BC12D modified under a 337 in 1981 for the addition of C-85 and gross weight increase to 1280 land 1351 sea. While doing a float certification on my plane last fall the FAA decided that before they would issue Baumann floats an STC at 1351 gross (which my plane is already approved at since they accepted the 337 in 1981) they wanted data or (proof) that the modifications done indeed make the plane safe at 1351 lbs.....even though the 337 already says it does (the 337 was rather poorly written...but it was accepted). So, after talking with many folks I purchased the Harer STC for $250...we then said...we'll inspect for compliance. Well, The 7/16" bushing were replaced, but with 5/8" not 11/16" per the STC...No big deal, a certain FAA inpector that we know said he'll do a field approval as long as the plane stays a BC12D-85 and never exceeds 1280 lbs land and 1351 sea without going to 11/16" bushing (don't I already have this approval?...the existing 337 clearly says 5/8" bushing installed). Okay, the wing root and strut attach fittings were replaced in 1981 with the proper ones required for the gross weight increase (in fact, the part nos listed on the 337 match those of an F-19...Very good. Now the fuel system, my plane has 2 wing tanks....valves under the dash...increased dia lines so on....however, there is no fancy vent system from the main tank...just the caps on the wing tanks...my IA says oh oh...now we are not I.C.W the STC. I said...the main tank is vented through the cap also....where the wire fuel gauge comes out the top. My question is this..since I purchased the STC and the mods were already done and documented on a 337 previously, must I submit a new one stating we Inspected...and it is In accordance with the STC...and all that or do you think the data provided in the STC documentation along with a copy of the already approved 337 will satisfy the FAA engineering office that is doing the flight test? In my mind, This is an example of the FAA being difficult....they said they'd give approval at 1278 lbs sea because the plane is a BC12D and that's what ATC 696 says is the gross weifght for a BC12D on floats....I disagree...Its approved under 337 dated Jan 29, 1981 as a BC12D-85 with 1280 gross landplane, 1351 sea.

[VictorBravo]

Re: More Harer STC questions

If you have a 337 that says your aircraft is STRUCTURALLY approved for 1351 pounds sea, and the FAA's concern is that the airplane structure will accept the floats, then you can make a case that the only areas of concern that are in play are those directly related to the structure. You should be able to claim that your existing fuel system, engine, etc. are already APPROVED DATA and are not affected by the float issue. You should be able to say that you bought the STC to provide double coverage on both ends for the structural issue only, so the FAA cannot say that the structural parts of the new STC can threaten to invalidate a pervious approval on the engine and fuel installation.

I also believe that an IA can also make certain reasonable deviations from the STC when installing an STC, if the deviations are specific to one particular airplane for a valid reason and noted on the logbook entry. "Installed Harer STC on this aircraft per STC drawings, with the exception of drawing XYZ which woulld conflict with a previously approved 337 installation in this area... all three fuel tanks remain fully vented per original factory design..."

When I did my Harer STC I made a couple of deviations, and I know others have done so as well. The deviations were mulled over, the pros and cons analyzed, and the effect on safety was very well considered. For example, my wing spar root fittings have MORE metal thickness than the STC requires at the critical point (bolt hole, for "tear-out" resistance), but they have the original metal thickness where the fitting straps bolt to the wood spar. This is because the bolts would tear out of the wood long before they would tear out of those .065 steel straps... the additional strength was needed at the attach bolt. I also chose not to remove the fuselage fuel tank and start adding vent lines, but while I had the wing tanks out I installed the additional tube stubs in them. Thest two wing tank vent stubs were connected to each other with a urethane cross-vent line Ty-Rap'ed to the forward cabin cross tube. If it is ever REALLY necessary, I can put a Tee in this line and run it down into the main fuselage tank and be in full compliance with the STC.

[N96337]

Re: More Harer STC questions

DanoT,
I'd say it's sounding like they're not understanding what's already been done and approved on your aircraft. If you complied with the Harer STC, then you'd be at 1500# (and it's not where you're trying to go in the first place)... but if the previous field approval specifically states 1351 gross in seaplane configuration, that should be adequate. (I'm assuming they're trying to do a one time STC for the floats, and not a multiple... if it's a multiple, that's a whole different can of worms)
As for a mechanic being able to "deviate" from an STC.... that's absolutely incorrect. The STC provides specific instructions that you MUST follow, or you're not in compliance. Does it happen? Yes... is it strictly legal??? No.
John H.

[Dano"T"]

Re: More Harer STC questions

No, the Harer STC allows modification to models BC12D-85, BC12D-4-85, Model 19. The addition of a new enginge mount which is 4" further forward changes the C.G. allowing for the increase to 1500# The same wing modifications are done for all models included in the STC. The STC cosists of a bunch of drawings and no step by step instructions except for the required drawing list for the desired level of modification. For instance: if you only want a BC12D-85 with 1280 gross land 1351 sea, then use drawings XX. XX, etc. and so on. The main idea is to install the enlarged phenolic bushings, wing root fittings, re-inforced strut attach fittings SEE HERE to accomplish the structural re-enforcement required for the gross weight increase. The addition of wing tanks allows for added fuel consumption of the higher HP motor. The model 19 requires addition of a new engine mount, electic system, extended baggage, battery box etc in addition to the above. The BC12D-85 uses the C85-8 the others use The C85-12 to accomodate the electrical system. My plane IS the equivelent of a BC12D-85 which according to ATC696 has GW of 1280 land 1351 sea. The modifications were done under a 337 before I owned it and IS approved data. The STC for the floats is intended for all models BC12D-85 and below...the FAA said they want documentaion toi prove that the mods approved via 337 in 81' are what is needed to safley operate at that weight...they can't recind the 337...but they can exercise the right to only test at a weight they feel comfortable with hence they only want to give Baumann Floats 1278 sea. My point is that purchasing the STC proves that the aircraft was adequately modified to sustain 1351, in fact, structurally it's good to 1500...remember it's the CG change with the longer mount that changes this. I dont feel it is necessary to submit another 337 saying it is good to go when the approved data (existing 337) along with supporting documentation included in the STC says its good already. My IA wants me to fly the plane back to his shop so he can inspect it some more...and list deviations such as the omission of the reduntant tank venting etc. and I am on skis now, so that means putting the wheels back on and flying 100 miles and leaving the plane with him again for something that I don't believe is required.

[Forrest Barber]

Re: More Harer STC questions

A "conformancy inspection" comes to mind. The aircraft must conform to original Type Certificate and any subsequent STC applications. ( At all times ) WE are working to help out on on a Taylorcraft in a shop right now that has the full Harer STC BUT has 13 rib wings.... either somebody changed them or somebody falsified the paperwork when the STC was applied OR THEY did not know any better.
Each FAA office moves in strange and mysterious way... The best thing an Owner can have is a good IA that has a good working relationship with a PMI at the FSDO , and ALL of them understand the regulations...keep the info coming.