Next year, the National Air and Space Museum will begin restoring and preserving aircraft in the brand-new Mary Baker Engen Restoration Hangar, part of the Phase Two complex now under construction at the Steven F. Udvar-Hazy Center. To treat the aircraft, the Museum applies a philosophy and range of techniques that have steadily evolved through the years. A project may start with an incomplete grouping of components or a complete aircraft in pieces, but most aircraft that pass through the Engen Restoration Hanger will be largely intact with worn exteriors that often hide extensive corrosion beneath fabric, wood, or metal skin. The treatment team, consisting of curator, lead specialist, and conservator, must first decide on the overall objective of the work after discussing a range of options:
- Stabilizing conservation that protects the aircraft from further loss or depletion.
- Preservation that maintains the aircraft in unaltered condition.
- Minimal structural, mechanical, and cosmetic restoration.
- Significant structural and mechanical restoration with minor cosmetic restoration.
- Restoration to a particular period.
- Restoration to production specifications.
Whatever course is chosen, the primary goal is to maintain authenticity, what I define as tenacious, unwavering concentration on the original history, not just of the aircraft type, say all Piper Cubs, for example, but whenever possible, the specific Piper Cub airframe that is undergoing treatment. The decision to jettison strict authenticity and adopt a paint scheme and markings never actually applied to the specific airframe during its operational history is widely regarded by curatorial and collections management staff as a choice of last resort. Photographs, documents and text, scale models, film, and audio are all available to tell the history of almost all types of aircraft. However, once gone, the original finish, condition, or configuration is forever lost. Structural damage and original paint and markings contribute to the artifact as an original document with a story to tell, just like an ancient manuscript. Of course, we must balance the ideal goal of pure preservation with practical requirements such as the safety of our visitors who often are in close proximity to the aircraft on display.
When selecting specific treatments, the project team choses ‘reversible’ treatments that will not permanently alter the artifact in any way and compromise its authenticity. Treatment specialists at the Museum combined restoration and preservation techniques when they prepared Bowlus BA-100 Baby Albatross for display at the Udvar-Hazy Center in 2000. We had accepted the Baby Albatross in 1963 and suspended it in the rafters of Building 20 at the Paul E. Garber Facility for more than 35 years.
The original fabric covering was beyond repair but the wooden airframe was in remarkably sound condition. Specialists had to apply several patches to the Mahogany skin, which they stamped. Such careful documentation of repairs or replaced parts goes back to the notion of the artifact as an original document. The right aileron control rod was found bent and because the damage may have occurred in service, it was not repaired. Original varnish on the wooden cockpit pod, wings and struts, elevators, and vertical fin was preserved by cleaning, polishing, and waxing.
Treatment specialists chose to cover parts of the wings and tail with a clear plastic film called Monokote (favored by enthusiasts of radio-controlled model aircraft) because it allowed visitors to see the delicate internal wood structure, the film was easy to apply using a hot air gun, and it is reversible.
The cockpit was in excellent condition so the specialists thoroughly but gently vacuumed it out, cleaned the area with mild Ivory Liquid dish soap and water.
The specialists wanted to preserve the colorful rudder fabric painted red, white, and blue with yellow stars. Once cleaned and gently vacuumed, they found it in sound condition except for a long tear, which they repaired with Monokote. They did not repair a small puncture near the right wingtip because it may have occurred while flying the sailplane, and the hole threatened neither visitor safety nor the integrity of the artifact.
Preservation can be just as difficult to carry out as restoration, but the results are no less attractive.
Sources White, John H. “Facadism: Is This Really Preservation?,” Locomotive & Railway Preservation, July/August 1988, 33. McManus, Edward. “A Restoration Philosophy,” in Collections Care, Report Number 2, (Smithsonian Institution, October 1991). Mikesh, Robert C. Restoring Museum Aircraft, (Shrewsbury, England: Airlife, 1997). Outdated in a few respects but basically excellent. Milbrooke, Anne. National Register Bulletin: Guidelines for Evaluating and Documenting Historic Aviation Properties, (U. S. Dept. of the Interior, 1998).