T-34 Doubler Plate AMOC

The T-34 Spar Corp. Doubler Plate Alternate Means of Compliance (AMOC)
You can click on a picture to enlarge.

Sioux Gateway Airport - Col Bud Day Field. Conveniently located with great facilities.

JetSun owner, George Wilen is one of the first T-34's to receive the AMOC.

Special tools and technician training are a small part of the AMOC fix. The JetSun culture is what's really special.

The aircraft weight is distributed between the gear and jacks to provide the proper spar stresses.

Flaps are removed.

Fuel bladders are removed.

The wheel wells are used for aft spar access

Fasteners are carefully removed.

A view of the wheel well after fastener removal

A view from the forward side of the spar through the fuel bladder access.

The technical drawings are placed for easy access

Much R&D was expended to develop the AMOC plate.

Each hole is drilled precisely centered and squared with the spar.

Plates are milled to exacting standards, then modified to exactly fit each spar.

It's a very time consuming job that must be done right the first time -- there is no room for error!

The shape of the plate is milled with a slight bow, and thus the holes are not perpendicular to the plate's face. To have the fastener heads have proper contact, the plate's face must be ground for each fastener.

Prior to installation of the plate, an eddy current test is made of each hole. Above, the eddy current equipment is being calibrated with the standard

Non-destructive inspection (NDI), accomplished with calibrated eddy current equipment.

The required NDI inspection is performed on the rear bath tub fitting

Necessary cold working is completed using hydraulic puller and other necessary equipment.

Doubler plate installed with all fastners.

The fuel cells are replaced (what a great time to replace your old bladders), flaps and other components reinstalled and final inspections are made.

As of March 15th 2004, the FAA grounded T-34s (except for ferry permits) because a spar failed due to stress where the main landing gear attaches to the wing spars. For now, T-34 owners can have their spars inspected for cracks and if no cracks are found, they will gain 80 hours of unrestricted flying time. Hopefully, before 80 hours of flight, there will be a permanent fix available to solve this problem. The approved procedure is to drill out three rivets where the MLG support brackets attach to the spars. Then, using NDI Eddy current procedures, we inspect these holes for cracks. If no cracks are found, the rivets are replaced with screws. The pictures below show these screws circled in blue. (pictures can be enlarged by clicking on them)

The pictures on the right show the rear spar inspection point. Two rivets were drilled out then each hole was NDI inspected and the rivets were replaced with screws.

Two screws in the trailing edge spar replace rivits after NDI inspection of the holes

The pictures on the right show the main spar inspection point. One rivet was drilled out then the hole was NDI inspected and the rivet was replaced with a screw.

One screw in the leading edge spar replace a rivit after NDI inspection of the hole

Completion modification plate installed.

The proud customer flies away in a T-34 who's wing spar is stronger than it was when new.

The proud customer flies away in an UNRESTRICTED T-34 who's wing spar is stronger than it was when new.