Harer STC Questions

[t-crafter]

Re: Harer STC Questions

All good points Bill I can see problems with both locations. my latest project has had a single shut off mounted above the control column since the 50,s I believe, so I am thinking of leaving it there. carlton

[flyguy]

Re: Harer STC Questions

On occasion, in any one of my 12D's I have found it necessary to wag the wings or do a couple of up and downs, maybe 2 Gees to get the fuel flowing from the wing tanks.

The one I have now has 2 tanks in the wings and a 3 way valve under the control column. Used to give me some problems occasionally, but has been 100 percent OK for quite some time now. Strangely the valve handle, which is normally straight down, has never been a problem. You would think it would be kneecap city all the time. Should check why it isn't in the way, I guess.
Darryl

[Pearson]

Re: Harer STC Questions

My plane had the wing tank valves located at the wing root. After drawing blood the third time from my balding pate, I decided to move them to under the panel. I took my plane to the IA I bought if from and worked with one of his mechanics to relocate the valves. When the mechanic asked me where I wanted the valves located, I sat in the plane and held the valves under the instrument panel directly between my knees. He fabricated brackets out of sheet aluminum, and held them in place with Adel clamps. We used fuel lube on all the fittings and tightened them SLOWLY. When they wouldn't tighten any more we waited for the heat from the friction to cool down, and then tightened them some more. I have never had a leak or drawn blood on the valves since. I intend to put the valves under the panel on my project plane also. It is the only way to go in my opinion.

[Howard Wilson]

Re: Harer STC Questions

On 20442, a '39. Left wing tank valve at the root, I hang an old digital watch from the valve handle for timing the fuel in both tanks. It hangs down just far enough below the top of the door frame to remind me or the pax to mind our head.
You guys experiencing flow problems from the wing tanks might want to check the gas cap gaskets. Worn seals can contribute to sluggish flow. Make sure that the correct fuel tank cap is installed, unless you like proving that you can land on that random field in the mountains.......

[magman]

Re: Harer STC Questions

We may have to cut some fabric to remove the bundled up vent system from
the wings.
After connecting per STC the plan is to add a "Tee".
AFTER the aircraft is back in service if there is a feed problem it would enable
a "vent test" in a more logical location.

The first 172's used a Top Vent System.
Cessna gave up on that real quick & for over 50 years it's UNDER the wing.
This is in the HIGH Pressure area & behind the strut to shield from ice & bugs.
Leaky cap gaskets cause fuel stains behind the filler.
Seems to me that regardless of tube size the Cap Vent system would always be less effective.

[magman]

Re: Harer STC Questions

REAL HAPPY with the info from you guys!
I've worked on aircraft since the Nina & Pinta projects were completed but
DO NOT consider myself an EXPERT on every particular type.
My opinion is EVERY aircraft owner should join the appropriate Type Club.

It appears that the Wing Attach Fittings on the fuselage do NOT require
any reinforcement per the STC.

Victor Bravo is absolutely right in recommending Teflon hose. (Type D)
Most mfg. state a replacement time of 5 to 10 years otherwise.

For very few $$ more the Temp Rating goes from 250 degrees to 450 degrees.
This is really significant on aircaft where a oil hose is near the exhaust (PA28-140).

We had 2 incidents is this area alone where the hose ruptured.
Engine became a PAPERWEIGHT very quickly!

[Pearson]

Re: Harer STC Questions

Magman,

The wing attach fittings DO require reinforcement according to the Harer STC. Drawings G-115 and G-116 show a U shaped addition to the two original spar straps for the front and rear spar.

Also if you are going to cut into the fabric on the wings, you may want to consider a modification I did to my plane when I had the wing tanks out for leak repair. The mod replaces the fabric over the tanks with sheet aluminum attached with rivnuts in the ribs and #6 screws. There is a 337 form and about 5 pictures posted on this site somewhere. If you can't find it, email me, or Private Message, and I will see if I can find my digital version and email it to you.

Hi to Gallagher!

[magman]

Re: Harer STC Questions

Thanks Pearson

Probably only fabric we'll cut is the Butt Rib to get the "Tubing Bundle" out.

I understand you to be saying that the Attach Points on the FUSELAGE require reinforcement per the STC Dwg. G-115 & G-116.

Several people sent photos of the SPAR Beef-up .

Another reason we NEED drawings!

[Forrest Barber]

Re: Harer STC Questions

"early" 45 was merely a BC-12-65 built very quickly, still had the three hinge tail. IT DID have the BC12D designation. Later on the two hinge tail and the correct fuel valves were added. REMEMBER the wing tanks were options at one point and "required" later on for the 85 HP. READ your Type Certificates. Fuel caps on wing with small J tube are fine, they do not :feed: the engine only the main tank. The F-19 system with the cross over vent is the best with the larger pressure tube, make darn sure the little hole is in the abck , yiou need it if you encounter icing . Yes Dorothy the front of the vent can ice over then you lose venting unless the little hole is open at the rear.

[GallagerG]

Re: Harer STC Questions

Hello Again, Thanks for all the responses. Another question to add to the rest,,,
What type/model/kind of fuel sump/gascolators were used on the original 46 BC-12-D, and what, if any, did the Harer STC call for? I have a glass bowl type, is this aviation technology of the 1940's or tractor parts??

Still looking for drawing or list so i can finish this baby!
Thanks,
"G"

[Pearson]

Re: Harer STC Questions

My 1946 BC12D has a gascolator with a glass bowl. I think they used tractor parts back then. I have heard of people getting replacements from tractor supply stores.

[N96337]

Re: Harer STC Questions

The STC calls out in drawing G-133, "Fuel Strainer, Koehler #K22008-3 or euiv. 3/8" NPT inlet & outlet".
Same style goes with the valve callout.... "Valve-Imperial #108-HD-3/8" or equiv. 3/8" NPT ports".
As far as the vent system goes...the only ones that I've seen have trouble are the ones that aren't set up like the drawings say. That being said, I've had them set up differently and work fine...but I've never seen them have trouble when set up exactly as drawing G-133 states. Alot of people throw flex tubing in there for fuel lines, or use rigid tubing, but have a dip in it somewhere...that's gonna screw you up every time...take a bit of time, keep it all flowing downhill everywhere, and it'll work fine.
John

[Robert Lees]

Re: Harer STC Questions

"{snip}...The F-19 system with the cross over vent is the best with the larger pressure tube, make darn sure the little hole is in the back ...{snip}

Even the B models have the little hole at the back, often covered in paint.

If you fly in cold climes, make sure these are open in case the front of the J tube (great description, Forrest) closes up.

Photo below from my archives...note the brazing of the wings and J tube onto what was evidently a bog-standard fuel cap:

Purchase $5 fuel cap.
Drill #40 hole through cap.
Purchase & bend $0.60 copper tube.
10 minutes brazing wings & J tube
$120 please.
Money for old rope.


Rob

[VictorBravo]

Re: Harer STC Questions

I understand you to be saying that the Attach Points on the FUSELAGE require reinforcement per the STC Dwg. G-115 & G-116.

No, there are no fuselage attach fitting modifications that I am aware of. The drawings deal with the fitting that bolts on to the root end of the wing spar. You need to increase the thickness of the metal from .065 to .095, and according to the drawings this thickness is not on the U shaped piece it is on the long straps.

Oh, you'll be cutting fabric, all right...

[Robert Lees]

Re: Harer STC Questions

Bill is right...these are the wing fittings that need to be made from 0.095":