On Thursday, March 28, 2002, Boeing pilots were forced to ditch a vintage Boeing Stratoliner, the Clipper Flying Cloud B-307, into Elliot Bay in Seattle, Washington during practice takeoffs and landings from Boeing Field in Everett, Washington. It is the only surviving aircraft of just 10 Stratoliners put into service by Pan American Airways starting in 1940. The airplane was the first commercial aircraft with a pressurized cabin that allowed it to travel at 20,000 feet, an altitude found to be smoother for flights, and a definite advantage over unpressurized competitive airplanes. WWII interrupted further production, yet most of the wing design and technology was replicated to build over 6,000 B-17 bombers during the war, and the Stratoliners were drafted as military troop carriers.

Volunteers and Boeing employees were in the final stages of a seven-year restoration to its July 1940 delivery condition, smarting the banners of PanAm, its first owner. It had been found as a display at the Pima County Air Museum in Tucson, Arizona, after a variety of services including the official aircraft of the late President Duvalier of Haiti and as a crop duster.

Owned by the Smithsonian Institution, the B-307 is destined for display at the new National Air and Space Museum outside Dulles International Airport in Washington, D.C. – the Steven Udvar-Hazey Center. Painstaking effort to collect original parts worldwide and to restore the plane to its delivery state had been accomplished, as confirmed by former onboard visitors who had been required to slip paper booties over their shoes.

After almost 30 hours in Elliot Bay, graying spots and streaks on the aluminum skin of the aircraft, signs of being immersed in saltwater were noticeable to many witnesses. Experienced pilots were able to minimize the physical damage yet the tally included torn skin under one wing from the lowered landing gear, dented cowlings, water soaked interior furnishings, and swollen flooring and doors.

Salt water pitting of magnesium engine parts, corrosion to the exterior skin, and the threat of corrosion to the interior and structural skeleton of the aircraft led Boeing to execute a plan of removal from the water, and immediate cleaning and flushing of corrosive saltwater. On Friday evening a crane was used to hoist the plane from the shallow bay water just off the West Seattle shoreline and onto a barge. The barge was moved to Terminal 105 on the Duwamish River, a location with environmental permitting to perform initial flushing and cleaning.

Around midnight, while the aircraft was on the barge and with a two hour limit due to tide restrictionsfor moving the loaded barge closer to Boeing Field, a 1% solution of CHLOR*RID soluble salt remover was applied to the exterior with a 3000 psi pressure washer. 15 gallons of the CHLOR*RID concentrate were added to a tank containing approximately 1,500 gallon of fresh water to feed the pressure washer for the 1½ hour exterior wash.

After the CHLOR*RID exterior wash two tests from the CHLOR*TEST surface chloride quantitative analytical field test kits were taken to confirm efficacy of removal of corrosion inducing chlorides. One test, taken under the belly close to the front of the plane indicated 1.5 µg/cm2 chlorides. The second test, taken under the wing at the engine cowling, indicated 3 µg/cm2 chlorides. These are generally considered acceptable levels in the surface preparation industry prior to the application of protective coatings.

The B-307 was moved into a hangar close to Boeing’s previous corporate headquarters in Everett to begin repairs with the objective of putting it on display at the Air and Space Museum in 2003. The four engines were removed and salt water pitting of magnesium parts was very apparent. The engines were flushed and coated with oil to prevent further corrosion. Rusting of parts such as the landing gear was observed. These parts were removed from the plane and placed in large drums containing the 1% solution of CHLOR*RID to dissipate the furthering corrosive effect of the salt contamination.

On April 17th the CHLOR*TEST field test kit was used to make two additional tests of the aluminum exterior. Both tests were from the fuselage close to the cockpit and behind the starboard wing and showed the level of chlorides to be non-detectable. Damaged parts of the aircraft were being removed and aircraft interior had been taken out. Along with the removal of the wing tips, the plan was to then wash down the entire interior as well as the exterior.

The entire exterior and reachable parts of the interior were pressure washed at 3000 psi with a 1% solution of CHLOR*RID. Prior experience with corrosion led Boeing to focus special attention on decontaminating the structural steel ribbing around the bottom of the fuselage in the cargo holds. The wand of the 3000 psi pressure washer was inserted into the wing tips to wash the wings’ structural steel components to mitigate the need for removing the wings.

Further testing with the CHLOR*TEST for the presence of chlorides on washed and accessible structural parts showed non-detectable levels of this corrosion inducing ionic species.

In one other incident of an aircraft recovery from salt water off the coast of Greece in which Boeing participated, repeated water washes were insufficient in stopping the continuation of destructive corrosion.

With the decontamination procedure complete and confirmed, Boeing could then focus on the objective of having the vintage aircraft once again soar into the skies.