Monday, December 1, 2014

November XP-82 Twin Mustang Restoration Update

What a Fabulous Year 2014 was for Our 
XP-82 Twin Mustang!

Aft Fuselages
Part of the team has completed riveting of the all of the little hard-to-get-to places on both aft fuselages. They are now concentrating on completing both dorsal fins. 

With the exception of the completion of the riveting work on the aft fuselages and dorsals, the remainder of the team has been working on completing the multitude of systems and small-to-complete jobs. 

Center Section Gear Door Hooks

The up-lock mechanism for activating the gear door up-lock hooks is quite complicated with the amount of moving parts that it has, but very dependable. The mechanism is controlled by one hydraulic cylinder on each side mounted on the forward spar for the forward hook, and then transitioning all the movements through a number of bellcranks, push rods and levers to actuate each aft hook mounted on the center spar. Two team members have spent the entire month locating each casting (ten) that holds the bellcranks, etc. These bellcranks and mounts are all interwoven with the hydraulic lines and wiring harnesses. Pictures of the completed systems will be in next month’s update.

Emergency Up-Lock Releases
In the XP-82, and all subsequent models, there are landing gear up-lock emergency releases controlled by a pull handle, one in each cockpit, that will unlock the main and tail gear and allow the gear to free fall without hydraulic pressure to the down position and positive lock. These back-up safety factors are in place in the event of battle damage to the hydraulic system or the normal gear down actuation system. 

There is an incredible number of pulleys in both wheel wells changing the direction of the cross-ship pull cables and releases. The NAA engineers who designed these complex gear door hook and emergency release systems deserve to take their hats off and take a bow.

Control Cables
All of the primary and secondary flight control cables, chains, pulleys, bellcranks, push rods, etc., are now installed with the exception of the final completion of the trim and balance cables, which will be completed this coming week.

Rudder Pulley Chains and Sprockets are now installed

 Elevator Pulley Chains and Sprockets are now installed

Rudder and Elevator Trim Tabs
The installation of the hinge blocks, new bearing mounts with new bearings, and three trim tabs are now completed. Finding the N.O.S. needle bearings for the bearing mounts has been a challenge, but I think we have bought every last one that was available in the world. We replaced the magnesium needle-bearing mounts and machined the new ones out of 7075-T6 aluminum, giving us a much higher safety factor due to numerous known in-flight trim tab failures. 

7075 T-6 Trim Tab Hinge Blocks with New Bearings

Both Rudder Trim Tabs are now installed

Elevator Trim Tab  is now installed

The team has completed the remaining items on the elevator, i.e., elevator control arms (two), counter weights, close-out panels and the final fitting of the elevator trim tab. We were required to add a small amount of extra counter balance weight to offset the additional weight of the trim tab 7075 fittings that we exchanged for the lighter original magnesium fittings.

 Right-hand Elevator Control Arm with Counter Weights installed

Note: All aircraft control surfaces must be precisely balanced as per the factory data so that the control surfaces, i.e., rudder(s), elevator(s) and aileron(s), does not flutter in flight like a flag on a pole in a heavy wind. A flutter in a control surface during flight is extremely dangerous. Thus our balance calculations must be perfect.

Aileron Hinge Points
The four special machined aileron hinge points that we need are nearing completion at one of our sub-contract machine shops. These are the main hinge point attaching-and-actuating fittings that attach the ailerons to the trailing edge of the wings.

We expect to receive these fittings and have them installed during December or January.

Canopies / Windshields / Aft Fairings
The final adjustments of both windshield bows to match the mating canopy bows has now been completed. Both center windshield glasses are now permanently installed, awaiting the delivery of the four windshield side glasses that were completed and shipped to us this past week. The final fitting of these side glasses will be completed by the end of December. A picture of the completed windshield assemblies will be in next month’s news release.

The aft canopy fuselage fairing located under the canopy is now completed on the left-hand fuselage and well on the way to being completed on the right-hand fuselage.

Left-hand Under Canopy Fuselage Fairing (above) is now complete.

Right-hand Under Canopy Fuselage Fairing

The P-82 series has an incredibly complicated brake system that is not fitted on any other known aircraft type. Thus replacement parts are impossible to come by. We recovered one main brake caliper out of the Fairbanks scrapyard parts that had been exposed to the weather for 50+ years. It appeared to be in terrible shape, but a couple of weeks ago, I decided to try to take it apart to expose the internal hydraulic pistons just to look at their condition. To my surprise, all three of the caliper hydraulic cylinders and bores were in perfect re-buildable condition. 

This leaves us with only one caliper to come up with. Pat Harker has machined new ones for his F-82E in Anoka, MN, and we will talk to him about him supplying us with a newly manufactured one.

Newly Machined Inboard Aileron Sector Controls

 Newly Machined Flap Push Rods (above) and Matching Threaded
Flap Push Rod Fittings (below)

The Katz

“Where are my helmet and goggles? 
Crank up the engines, I’m ready to go fly.”  
-- Allison

 Hope everyone had a Happy Thanksgiving.
Wishing you a very Merry Christmas and Happy New Year!

Tom and the XP-82 Crew

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