XP-82 Twin Mustang Project: November XP-82 Twin Mustang Restoration Project Update

Firewall Forwards

Two of the team members have spent the entire month manufacturing replacement lower cowl ribs. These are the ribs that the lower cowling attaches with Dzus fasteners. We had some of the original ribs to use as patterns, but they were totally non-usable due to the aircraft being moved countless times when it was in the field in Ohio. All of the upper cowl ribs were completed last month, and when the lower ones are completed this month they will all go together for heat treat up to T4 condition (hardened).

Four of the sixteen lower cowl formers

Electrical

All of the generator and starter firewall forward electrical harnesses have now been fit, cut to length, and their large amperage terminals crimped and soldered on.

We are in the process of completing the low amperage firewall forward Cannon plug harnesses that go forward and attach to all the miscellaneous electrical components: tach, start and pre-oil relays, generator field, supercharger solenoid, mixture and carb air temperature controls, oil, glycol and carb air temp probes, prop feather and chip detectors.

Both feather pumps for the MT Propellers are now permanently installed on the left-hand lower firewall armor plate.

Start and pre-oil relays are mounted

MT Propeller feather pump mounted on firewall

Carb Air Temperature (CAT) Control Motors

These two CAT motors have been an ongoing headache. For years, we have tried to find replacements because the originals were open to the weather and full of water for fifty plus years. Both motors, all the sequential limiting switches, and all the wiring and gearing were nothing but a pile of rust and corrosion. We offered this task to one of our wizard volunteers, Gerald. He took this task on to find replacement limit switches (the original style is no longer available), get the motor armatures and fields rewound, and remanufacture all the interior motor and switch mounting brackets.

Original CAT control motors

He found an electric motor rewind shop that rewound the tiny motors and fields, and repaired the brake assemblies which instantaneously stop the motors at the proper selected positions. There are four positions for this carb air control system: ram air, half-hot air, full-hot air, and filtered air. The carburetor air-induction trunks of an aircraft engine must have the ability to control the temperature of the air being forced into the carburetor due to different environmental conditions (temperature and moisture) during flight. The pilot controls this temperature by rotating a switch on the instrument panel to stop the control in each desired position.

All of the limit switch and Cannon plug wiring has now been completed.

One lingering problem was that we could not find the microscopic 16-tooth gears that were on the end of each armature as the originals were rotted away. With much research, Weezie found new ones from Stock Drive Products in New Hyde Park, NY.

Oil/Fuel Pressure Senders, Oil & Coolant Lines

All four are now permanently attached, Aeroquip-hosed from the engine to the sender, and sender to the firewall. These four NOS Rochester units were contributed to our project by Larry Kelley, B-25 “Panchito.” Thank you, Larry. See the article about Larry Kelley’s B-25 Mitchell in the December issue of AOPA Pilot magazine.

The trip to mandrel-bend all of the firewall forward oil and coolant lines scheduled for last month was postponed. Hopefully, the trip and the mandrel bending can be accomplished by the end of December.

Belly Scoops

The final fitting and riveting of the fairing panels have now been completed on the left scoop, along with both forward airfoil attach rails. This fitting has been a complex process to rivet all of the required threaded nut plates for attaching the fairing panels to the lower side of the center section. These nut plates had to be installed between and under the hat channels in the 95-gallon center section fuel tank bays, and a number of them had to be installed in the hydraulic bay compartment in amongst all of the hydraulic lines and components. A fun job, but now finally completed.

The airfoil support rods for mounting the forward part of each belly scoop

Seats/Armor Plate/Weight & Balance, Center of Gravity (C/G)

The final assembly of all the seat elevation parts is now complete. We have replaced the original steel armor plates with the exact same dimensions using 1/4” aluminum plate . We originally made a decision to wait until we were doing the ‘weight and balance’ of the aircraft to see where we needed to add or subtract weight. The position of the original steel armor plates was so close to the neutral C/G point that it would not make any substantial difference in the center of gravity of the aircraft.

(When manufacturing and/or restoring any aircraft, one has to be very careful when it comes to the weight and balance of the finished aircraft. All aircraft must maintain a specific balance range of inches so that the aircraft flies properly. The ‘weight and balance’ is determined by weighing the aircraft after it is completed to determine where the center of gravity is. The center of gravity can be corrected by adding or taking away factory lead balance weights positioned in the tail.)