Restoration of L749A Constellation N749NL

Connie's Comeback - Restoration of L749A Constellation N749NL

September 2002

Dutch Connie

The Dutch National Aviodome Museum recently decided to undertake a very exciting and challenging aircraft restoration project. The aircraft involved is L749A Constellation N749VR, a long time resident of Avra Valley Airport in Marana, Arizona. On August 23, 2001, I traveled to The Constellation Group's headquarters at Avra Valley and visited with Arno van der Holst, Raymond Oostergo and Erling Blom. Arno is the museum's managing director while Raymond is the museum's Manager of Special Projects. Erling, an avionics specialist, is a KLM employee volunteering his time to the Aviodome.

The Aviodome Museum is located at Schiphol Airport in Amsterdam, Holland. Its collection includes over fifty-five aircraft and was visited by 100,000 people last year. Like most aviation museums, most of those involved are volunteers and, at last count, the museum had twenty-four paid employees and over 180 volunteers. The museum has an excellent website, in Dutch, English, German and French that can be accessed at The website also has a page with the latest updates on the project, including some very interesting photos.

I first saw this Constellation in March 1997 when I participated in The Constellation Group's Flying Program at Avra Valley. It was parked on the far end of the ramp and looked rather forlorn. I was told that it was a sistership to the MATS Connie and was owned by an organization named the Dutch Constellation Society that planned to restore it. Since that time, I had visited Avra Valley on numerous occasions and noticed little or no progress being made. It wasn't until my latest visit in late March of this year that Frank Lang, The Constellation Group's chief pilot, told me the airplane was going to be restored and flown to Holland in October. Needless to say, I didn't believe him!

The aircraft, c/n 2604, was one of a group of nine short-fuselage C-121A's and one C-121B built for the USAF in 1948. It was assigned military serial number 48-612 and entered service with the Military Airlift Command in 1949. Based at Westover AFB, Massachusetts, it was used during the Berlin Airlift to shuttle high priority passengers between the US and Europe. In 1950, along with a number of other C-121A/B's, it was modified as a VIP transport and re-designated a VC-121A. It was based in Wiesbaden, Germany during the 1960's where it flew VIP missions before being retired from active service in 1967 with 14,541 hours. It then spent a number of years parked at Davis Monthan AFB in Tucson before being sold to Christler Flying Service in 1970 as N9465. The aircraft was converted for agricultural spraying by the installation of two chemical tanks in the cabin, and spray nozzles on the wings. Christler used the aircraft until 1979 when she was sold to Beaver Air Spray, Inc and registered C-GXKR. Conifair Aviation of Quebec, Canada bought the airplane a few months later and, along with two of her ex-USAF sister C-121A's, it was used in the war against budworms in the woods of eastern Canada. Conifair flew her, as aircraft #2, until 1988 when she was stored at Mont Joli, Quebec and offered for sale for $200,000 with a total of 15,600 hours. Vern Raburn, of The Constellation Group, bought her in the spring of 1993 as a spares airplane for the MATS Connie, N494TW. The Dutch Constellation Society purchased the aircraft from Vern in November 1993 and Frank Lang and a flight crew from The Constellation Group ferried it from Mont Joli to Avra Valley on September 9-12, 1994. Since arriving at Avra Valley, she had not flown.

Interesting to note is that the Curtis electric propellers installed on this airplane were worth more than the airframe at the time it was flown to Avra Valley. Immediately upon arrival, the propellers were removed and shipped back to Canada for use by the Forest Industries Flying Tankers on their Martin Mars fire fighting flying boats, based at Sproat Lake on Vancouver Island, British Columbia, Canada. The Mars uses the same propeller blade on its four bladed propellers. Very few Connies had Curtis electric propellers installed and it is often said that when the few remaining spare serviceable blades are exhausted, the MATS Connie will end her flying days.

Almost immediately after N749VR arrived in Tucson, the Dutch Constellation Society started experiencing financial problems. One of the R3350 engines was sold to The Constellation Group to raise money for parking fees and rent. For almost seven years the airplane sat at Avra Valley with yearly visits from the Society to perform minimal preventive maintenance. By the end of 2000, the Society realized that they were going to need help with their endeavor and contacted Arno van der Holst of the Aviodome. At this point, there were three options open to the Aviodome. (1) Decline the project, at which time the aircraft would have been sold for parts and scrapped; (2) Disassemble the airplane and ship it to Holland via surface transportation; or (3) Restore the aircraft to airworthy condition and fly it to Holland.

Arno had visited Avra Valley four years ago on an unrelated trip. He made a cursory inspection of the airplane and felt it was not a good candidate for restoration. However after a closer technical inspection by Marc Westenberg in January 2001 and, after a meeting with representatives of the Dutch Constellation Society, he decided to return to Tucson and assess the feasibility of restoring the airplane for a flight to Holland. A team from the Aviodome arrived on March 9th and got right to work. The team found the airplane to be in much better condition than thought before. There was minimal corrosion and the #2 and #4 engines were successfully run. In addition, the hydraulic, fuel and electrical systems were found to be in good working order. At the end of two weeks, the team gave a thumbs-up to the project and the project was officially kicked off. The airplane couldn't have been parked in a better location. Avra Valley Airport is home to The Constellation Group and its maintenance facility. Between JR Kern, Tim Coons and the remaining technical staff, there are many years of radial engine experience and, more important, expertise with the L749A Constellation. The Aviodome wisely decided to utilize this expertise for the project. I visited Avra Valley a few days after the team departed in March and, with the exception of a test prop installed on the #1 engine, everything looked much the same as it had been during my previous visits. Since March, six additional teams have been dispatched to Avra Valley and the transformation of N749VR has been amazing.

The second team arrived on May 4th and work continued on engines #1 and #4 resulting in successful engine test runs. The three rudders were removed for recovering and control cables were inspected and replaced. The cabin flooring was removed and work began on fabricating plywood replacements. The wiring and fuel systems were inspected and necessary repairs made. After enduring somewhat less than ideal working conditions, with temperatures in the 100*F+ range, the team returned to Holland on May 19th.

The third team arrived in early June. The cabin floor was completed and all cabin windows, which were severely crazed, were removed. The fire bottle system was removed for repair and initial landing gear retraction tests were performed. The wing bolts were inspected, fuel and air hoses were inspected and replaced, and the arduous job of stripping the many layers of paint was begun. In addition, Tim Coons began the process of inspecting, assembling and balancing the Curtis Electric props. Tim, a Constellation Group mechanic, learned this skill in Canada a few years ago and the #1 prop was successfully installed the week of June 12th. A high-pressure cleaner was procured to speed up the paint stripping operation.

Team number four arrived on June 18th and volunteers continued the task of stripping paint while the technical staff concentrated on the engines and propellers. The "long" nose was removed and replaced with a "short" nose, which had been borrowed from the French Musee de L'Air at Le Bourget. Work continued on the engines and propellers and the #1 engine was test run with its new prop. A significant milestone is reached when an engine borrowed from the Constellation Group was installed in the empty #3 position. The fire bottle system was installed and successfully tested and refurbished instruments were installed. The airplane was beginning to look different and the team sensed success was within their grasp.

Group number five arrived the first week of July and continued with the work started by previous groups. Work on the R3350's continued and the final gear swing was successfully performed. The center cockpit and cabin windows arrived and installation began. Paint stripping continued and the brakes received much needed attention. The delicate task of propeller assembly and balancing continued slowly. The cockpit floorboards are removed and cleaned along with the careful cleaning of cockpit windows. The three rudders, which were sent out for recovering, were received and were ready for installation. Radios were checked and the restored glareshield was replaced.

The sixth group arrived in late July and joined the Constellation Group's mechanics, who had continued working on the airplane during the absence of the Dutch volunteers. Propeller assembly, balancing and painting operations continued. Props were installed on engines #2 and #3 and the wing leading edges were cleaned and painted black to simulate the original deicing boots. The team also painted the roof of the aircraft white again. Additional engine work was completed and engines #1 and #4 were test run. The installation of cabin windows was completed.

The seventh group of Aviodome workers arrived on August 10th and work continued on completing the remaining propeller assembly for engine #4. During x-ray testing, one blade was found to have a crack, which necessitated the use of a spare blade. Propeller blades are normally retained as a matched set for the life of a propeller but, due to the scarcity of propeller sets, this could not be done and a spare blade was used. This significantly increases the difficulty of assembling and balancing the propeller and the group was very lucky to have the expertise of Tim. Work continued on cleaning and polishing the airplane and replacement of the main and nose wheel tires began. It's interesting to note that after years of not being available, tires for the Constellation were found at Desser Tires, a large aircraft tire distributor. The airplane would be ready for its ferry flight in late September or early October.

The eighth group arrived on August 29th and went to work immediately to complete the few remaining items. Rudders and the tailcone were installed and work continued on polishing the fuselage. The fourth propeller was installed and the propeller synchronization system was cleaned and repaired prior to engine testing. Cockpit seating, an antenna and a few remaining instruments and radios were installed and high speed taxi tests were performed on September 12th and 13th. During taxi tests on September 13th, a piston rod broke in the #4 engine, destroying it. Faced with the prospect of a winter crossing of the North Atlantic, the group decided to suspend operations until next spring. The aircraft was sealed from the elements and the group returned to Holland to search for a new engine and formulate a new plan.

Work resumed on the Connie in February 2002 with removal of the #4 engine. Two “new” engines had been found by the museum over the winter and by the end of March one of them was in place and had been test run. During this time an APU was installed and many minor details were attended to, including the continual chore of polishing the exterior. During April and May, engine adjustments continued as well as detail work in the cockpit, fuel system adjustments and installation of an oxygen system. The FAA issues an “Experimental” airworthiness certificate on April 25th and the first high speed taxi test with the new engine was performed on April 29th.

The big event everyone had been working towards occurred on May 9th when the old girl took to the air for the first time since 1994. Captain Frank Lang, Chief Pilot of the Constellation Group, was in command of the flight and commented after it that no serious problems were encountered and the airplane flew beautifully. A second test flight, lasting one hour, was made a few days later on May 14th and, like the first, no major problems were encountered. A third flight was made on May 16th to Pinal Airpark where the airplane was weighed for the required weight and balance calculations. Things were now looking good!

By late May 2002 the restoration of N749NL was nearing completion and anticipation was building about the ferry flight to The Netherlands. The Internet was abuzz with people attempting to predict the departure date and route of flight. While the airplane was physically ready for the flight, the FAA had still not granted an airworthiness certificate, although a restricted certificate allowed test flights within the borders of Arizona.

A fourth test flight was flown on May 26th with Frank Lang in command, Henk de Waard, a KLM 737 captain, in the right seat and JR Kern performing flight engineer duties. Assisting JR was Tim Coons and along for the ride was Clint Fraser, an America West captain, who has flown extensively with the MATS Connie. The flight lasted only thirty minutes and concluded with some low fly-bys at Avra Valley to allow a Dutch film crew to shoot some video and still photographs. After returning, a number of minor squawks were written up and work began immediately to correct these items.

After completion of the minor repairs and adjustments, a longer two-hour test flight was scheduled for May 30th. Again, the purpose of the flight was to put some time on the aircraft and engines prior to the long ferry flight to Holland. Departure was planned for 0600 to avoid the forecasted 107°F high for the day and a Beech King Air was chartered by the Dutch film crew to get some air-to-air shots of the Connie. Although the air was thick with smoke from a huge forest fire in the mountains just east of Tucson, the King Air flew in loose formation with the Connie for about an hour taking photographs and video footage. The flight returned to Avra Valley and again the aircraft was pronounced to be in fine condition, with little more than a few minor squawks noted.

There was a feeling of optimism amongst the team that the ferry flight was finally close in hand and preparations for it began in earnest. FAA approval of the radio installation was received on May 30th with approval of the oxygen system a short time later on June 3rd. The only remaining box to be checked was the issuance of an airworthiness certificate by the FAA, which proved to be a very complex and frustrating exercise requiring massive amounts of paperwork and patience. By mid-June it was obvious that approval was not going to happen soon and the last of the Dutch team returned to Holland to await further developments. After a number of false starts, Raymond Oostergo returned to Avra Valley in late July to work out the final details with the FAA. One item that proved to be particularly troublesome was the need to properly document the removal of the aircraft’s engine superchargers. More than one meeting was held with the FAA before the problem was finally resolved.

On July 30th another setback occurred when, during an engine test, a rod broke in the #1 engine necessitating another engine change. It is very likely that this problem would have probably occurred during the ferry flight if all things had gone on schedule back in May. Much easier to change an engine at Avra Valley than over the mid-Atlantic! The museum had purchased two spare engines when the #4 engine failed in September 2001, and the second spare was readied for installation. During the next three weeks, the team worked hard on replacing the engine and completing the remaining paperwork to allow the FAA to issue the airworthiness certificate. The team was rewarded for their hard work during the week of August 17th when, on the 20th, the “new” #1 engine was run for the first time and, on the 22nd, a special airworthiness certificate in the “Experimental-Exhibition” category was issued by the FAA. While this was not the hoped-for “Standard” airworthiness certificate, it would allow the airplane to begin it’s long journey east.

Before the ferry flight could depart, the #1 engine had to be fine-tuned, ground and flight-testing performed to verify the performance of the #1 and other engines, spare parts loaded on the aircraft and the flight planning performed for the flight. With many thousands of man-hours of work performed on the restoration and almost twenty-five hours of flight time logged since September 2001, the aircraft was finally ready for its journey and departed Avra Valley at 8:12am on the morning of September 15, 2002. Thirteen days later on September 28th, N749NL successfully completed her transatlantic journey and arrived in Holland. The route of the flight was Fort Worth, Texas – 9/16; Alpena, Michigan – 9/18; Goose Bay, Labrador – 9/20; Keflavik, Iceland – 9/22; Duxford, England – 9/25; Manston, England – 9/25; Lelystad, Netherlands – 9/28; and Schiphol International Airport – 9/28.

The work performed at Avra Valley was focused almost exclusively on making the airplane airworthy for the flight to Holland. Once it arrived at Schiphol Airport, the four borrowed Curtis Electric props and one borrowed R3350 engine were removed and packed for shipment back to The Constellation Group at Avra Valley. The aircraft was towed into hangar 14 and the process of final restoration began. The museum plans on painting the aircraft in late 1940's KLM markings and to install a full passenger interior. New props need to be found as well as a replacement engine. I wish the museum much luck in their endeavor and look forward to seeing this aircraft perform on the European airshow circuit.

Ralph M. Pettersen
September 2002

Photo credits: Günter Grondstein, Bo-Goran Lundkvist, Dutch Aviodrome Museum, Ralph M. Pettersen

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----Created 28 January 2004------Updated 7 March 2004----