May XP-82 Twin Mustang Restoration Update

 NACA via the National Archives

 Our XP-82 when it was with NACA in Cleveland, OH being used as an 

armament test bed 1945 through December 1949

 The end of our ten-year XP-82 restoration project is in sight. 

The light at the end of the tunnel is not an oncoming train. 

We are down to a rather short punch list with another ten weeks to go. A few of the outstanding punch list items that would have precluded us from making Oshkosh this year are now solved.

Outdoor Gear Doors

Both inboard pressings were delivered to us about three weeks ago and the fitting of these doors I thought was going to be extremely difficult and time consuming. Paul had them fit perfectly within a week and the internal framework is now fit and both have been completed with the spot-welded outside skins.

New outboard gear doors without outside skins

 Gear doors with skins

Tailwheel Doors

The two tailwheel door retract brackets have been completed and attached. The four doors  are mechanically retracted by rods attached to the tailwheel arm structure(s). The two retractable tailwheel assemblies are retracted not by hydraulics but by a 3/16 stainless steel cable running the full length of each fuselage up to a set of pulleys attached to each main landing gear retract arm. When each main gear retracts, each tailwheel is drawn up into its up-locked position along with the doors. On extension, both tailwheel assemblies unlock, gravity extend and cable-latch the down lock. A very unique NAA factory-installed retract system.

 Bent and corroded original part with two new ones

Tail wheel retracted (above) and extended (below)

 Landing Gear Retractions

We have completed the landing gear retractions and timing valve adjustments that sequence the inboard gear doors opening and closing. The main gear inboard doors are closed with the landing gear in both the up and down positions with timing valves sequencing the proper opening and closing for the gear to pass. A very straight-forward NAA design that works extremely well.

In the following photos the gear will start to retract, then the gear will lock in the up position, then the door will close, then the door will open and the gear will extend to the down locked position. Then the gear door will close. 

Brake Assemblies

The last two major items that we have been waiting for to complete our XP-82 restoration are the two brake calipers. This style of brake assembly was used only on the XP/F-82 Twin Mustang series and no other production aircraft, thus none could be found in the surplus market.

Non-airworthy and broken original brake

 Two new aluminum calipers are being 3D computer milled

The most serious of these missing brake items were the two small pressure check valve boxes. Pictures are attached. Our main machinist, John, is progressing nicely to have both calipers completed for us within the next week.  John was able to 3D print off of one unairworthy magnesium caliper that we got out of the Alaska wreck site recovery and he is well into completing the machining on both new aluminum calipers. BUT, we had no sample of the small pressure check valve boxes to copy. The big problem was that the entire brake assembly was manufactured by Goodyear and the XP-82 parts books did not give us any breakdown or part numbers of any of the associated Goodyear brake parts. Thus we had nothing we could take apart and copy on the two pressure check valves.

Last week, John Soplata, the grandson of Walter and Margaret Soplata, who found for us the second needed wheel in the cellar of the house, discovered a complete XP-82 brake assembly WITH one pressure check valve. The entire brake and check valve has been shipped to us FED EX. Now having both brake assemblies, all the original pistons, springs, depth indicators and slave cylinders can be salvaged out of both original brake packages. The two original calipers are cast out of magnesium and due to corrosion they could not be made airworthy. So, along with the two new calipers being machined, all we have to do is duplicate the one small check valve box which will be completed within two weeks.

   Not having these pressure check valves was a grounding item. A very time consuming bump in the road was avoided.

Items on the “to complete” punch list.

1. After this coming week’s hard two-hour engine and propeller run-ins (we do not expect any problems), the entire XP-82 airframe will be lightly washed down with aluminum etch and a soft Scotch Brite pad to blend out any small scratches. This will highlight the color differences between the three different alloys of aluminum that had been used on the exterior of our XP-82. If one looks at the original pictures of our aircraft during its prototype first flight, you can definitely make out these color changes. 

2. We have received all of the stencils for all of the painted markings that are all over the airframe.  These will be applied after the etching.

3. We have now exceeded 202,000 man-hours invested in this XP-82 restoration.  So if nothing goes bump in the night, we will make Oshkosh this July with time to spare. 

The left-hand, right-hand and center section flaps are now permanently installed and adjusted to their four different degree stop positions

Original Radios

We were able to find the seven radios that were originally in our XP-82, including all of the Cannon plugs. For authenticity we have duplicated the exact color wires that we soldered back into the original plugs. We still have one more Cannon plug to solder,  the antenna wires that plug into the radios and tie ups to complete the original installation.

Ailerons

All four ailerons are also now permanently attached. Randall now has the range movements, balance, cable tensions and stops set to match each stick in both cockpits.

Rudders and Elevator

Both rudders and the elevator are now permanently installed. Range movements, balances, cable tensions and control movements have been done and synchronized to both sets of pedals and sticks. This was quite a time consuming job getting all four pedals matched to each other and to both rudders, but now they are completely done. All turnbuckle safety wiring is now completed.

Leading Edge with Gun Ports

The entire leading edge is now totally attached. This job took Paul and Randall a complete week due to the final riveting and the hundreds of screws and nut plates throughout the forward spar.

 Starrett Level

Right forward of the left-hand tail wheel there is a 3” round hole in the left side of the fuselage that houses a mounted Starrett level that is visible to set the pitch (tail up/tail down) of the two fuselages when doing a weight and balance.  In the 1944 North American Aviation XP-82 plans it showed a very detailed picture of the level with part number and the mounting structure. I instructed Weezie to contact Starrett to see if they had one of these levels in their museum that we could get for installation in our XP-82 to make the restoration as original as possible.  Within a few hours, she found an identical brand new one in stock at Grainger in Orlando. What were the chances of finding a Starrett level absolutely identical to the 74-year-old parts book drawing?

Outboard Wings

Both outboard wings are now totally bolted and torqued, 300+ internal-wrenching bolts in all. All of the fuel feed and vent hoses are now installed, tanks filled with fuel and all connections and pumps tested for leaks.

Pitot Static Systems

The pitot (air speed) and static (neutral air pressure) systems going to both cockpits are now completely hooked up and pretested for leaks. A technician from a FAA-approved repair station facility will come to give us our required altimeter, transponder and encoder (tells ground controllers your altitude, air speed, etc.), pitot instrument and static air going to each air speed, climb and altimeter instruments for accuracy sign-offs. I cannot do these final checks and sign-off as a FAA-licensed avionics facility must do these tests. 

Engine/Prop Test Runs

Since October we pulled our XP-82 outside two more times for engine/prop test runs. Each time we would tie down each tail to strong tie down anchored rings, add sand bags to the top of the horizontal to stop the tail from lifting during hard run-ups.

So far, I have brought the power up on each engine to 1500 rpm, about half power and test- cycled the props. I will start the prescribed three-hour run in schedule dictated by Vintage V12s, the company that overhauled our two Merlin engines. To date we have 1.5 hours time of ground runs and system checks on both engines with no squawks.

 Weight & Balance (W & B)

A few weeks ago a weight and balance company from Lakeland, FL came to perform the required W & B on our XP-82. The wood underneath the propeller hubs is not supporting anything; they are just there for a safety to prevent a nose over.

 14,979 lbs. with 400 lbs. of sandbags on the horizontal stabilizer

Indicators

We were able to locate two NOS ID-42A/APS-13 radar indicators. These are installed just below the pilot and co-pilot’s glare shields. When the light comes on it lets you know that an uninvited guest is on your tail.

“Can I have a B-25 ride … 

can I, can I?”                         

—Allison

B-25 Mitchell Panchito who owns 

Larry Kelley.

Who owns who??

 Happy Memorial Day from Tom & the XP-82 Crew

Quote of the Month

“The object of war is not to die for your country but to make

 the other bastard die for his.”                  — Gen. George S. Patton