Is there anything more captivating than flying over rolling hills in a historic airplane at sunset? It was this fascination and the good condition of the octogenarian AT-16 Harvard IIb that motivated Natascha Wirth (39) and Clemens Rüb (37) to restore it. The five-year project has been organized by Verein U-328, an association set up specially to restore the aircraft. MOTOREX products give the team, which is based at Bleienbach airfield in Switzerland, that extra bit of lift.
They share a passion for flying. Natascha (aerospace underwriter and pilot) and Clemens (aircraft mechanic and pilot) met a few years ago while helping restore a Harvard IV. Together the restorers returned the plane, one of just five in Switzerland, to airworthy condition. In addition to the joy of a successful outcome, the experience was a source of valuable knowledge and a motivation to do it again.
In 1948, Switzerland purchased forty surplus AT-16 Harvard IIb’s from Canada. Originally built in the United States as military aircraft, the planes were extensively overhauled by Swiss specialists and converted into training aircraft to teach aspiring pilots instrument flight skills. The rear section of the cockpit was able to be covered over to remove all visual points of reference and simulate full instrument flight conditions. The aircraft were in service for almost 20 years before they were replaced by more up-to-date Pilatus P-3s in 1966. U-328 escaped the scrapyard and was converted to a museum exhibit. It was on display at the aviation museum in the Swiss town of Dübendorf until 2015, when, by a series of coincidences, it made a happy landing with the Obersimmental Hunter association. The U-328 association was established to restore and subsequently operate the aircraft.
The aim of restoration is to return the aircraft to airworthy condition while keeping it in original condition as much as possible. At the same time, the team hopes to share valuable knowledge about historic military aircraft and preserve a piece of cultural heritage. The project is also a way for different generations to share their enthusiasm for aviation and engineering professions. The many different operations involved in restoration provide a surprisingly broad range of opportunities to apply and expand professional skills—an approach that even young people find appealing. As a result, the team includes young automation, avionics and electronics engineers as well as seasoned professionals.
“Luckily, the aircraft was complete except for just a few parts”, Natascha tells us, standing next to the now largely dismantled plane. There are around 30,000 individual parts. Spare parts are still readily available for the once mass-produced aircraft. U-328 made the journey from the museum, wings detached, by semitrailer in spring 2024. The issue of preserving its original condition immediately sprang to Clemens’ mind. The fuselage consists of a tubular steel frame to which aluminum panels have been riveted to create the bodywork. The passivated surface gives the plane the characteristic light gray color that was typical of its era. Clemens was on the lookout for a tightly adhering fluid to protect the surfaces against external influences during the restoration.
It was important that the fluid did not form lumps, like wax, for example. Instead it had to provide a light, dustdry protective film that could also be easily removed.
MOTOREX’s Technical Customer Service was able to assist by supplying polyvalent all-rounder INTACT MX 50. This universal spray is suitable for both cleaning and protecting metal surfaces. The biggest challenge according to Clemens is restoring the wings, which have a total span of 12.8 meters. They have riveted aluminum sheeting and are covered with fabric in places. They also house the fuel tanks and jacking points. Since the wings will not be opened, INTACT MX 50 also has the task of protecting them from inside by forming a light but effective film that displaces water and provides long-term protection against moisture-related corrosion. The restoration team is also using sprays such as SILICONE, GREASE SPRAY and POWER CLEAN. Clemens is a firm believer in FETT 2000 for lubricating wheel bearings and various other lubrication points, using it on various other historical aircraft that he takes care of. “It adheres very well, is pressure-resistant and extremely water-resistant. So water-resistant in fact that I use it for the retractable wheels in the floats of an amphibious aircraft”.
Lubricants and operating fluids used in aviation have to satisfy specific demands. When U-328 was built in the 1940s, engineers took their bearings from the best products available on the market at the time. But that was more than 80 years ago now. Today there are specialists such as motor engineers who know exactly which motor oil to use for a historic plane or which grease can be used on propellers. As a certified aircraft mechanic, Clemens Rüb also knows what needs to be cleaned, lubricated and preserved, and how. He is the person with accountability to FOCA, the Federal Office of Civil Aviation, for the restoration project. Restoring an airplane is a complex procedure, which has to be documented step by step with thousands of photos and painstakingly completed renovation and inspection lists.
Powerful engines are a feature of many military aircraft and make them great fun to fly. The AT-16 is no exception. It has a Pratt & Whitney R-1340 AN-1 “Wasp” engine. The nine-cylinder, air-cooled single-row radial four-stroke engine has a huge 22-liter displacement, weighs just 401 kilograms and can generate 550 hp at 2,200 rpm. A crankshaft the thickness of a forearm transmits this power direct to the adjustable, 2.75 meter-long, two-blade propeller. The engine and propeller will be overhauled in due course by specialists, after which they will be good for a further 1,000 hours’ flying time. The association has budgeted some 125,000 Swiss francs for this work, a figure that brought them down to earth with a slight bump.
The project demands a lot of skills from participants. There is no doubt that it needs plenty of tenacity as well as specialist knowledge. When you see how painstakingly restoration is proceeding—and indeed has to proceed— it becomes clear why it will take five years until U-328 shows new signs of life for the first time. No one is in a hurry, though; restoring the aircraft to a professional standard is what the project is all about. Once it’s back in the air, U-328, the legendary AT-16 that was once condemned to an existence as a museum piece, will more than compensate for all the challenges that have been overcome.