Sunday, December 18, 2011

Winter Maintenance Program - The Stearman

By B.Reid

When winter time arrives, so does annual inspection time. One of the first aircraft to work its way through this process is the latest acquisition by Vintage Wings - our recently restored Boeing Stearman. A few minor irregularities were fixed up, such as the replacement of a leaking carburetor and adjustment of elevator stops. Next on the list is the replacement of the oleo struts, as they too  have been leaking.

After careful research through Second World War photographs, we have concluded that all the engine cowls were yellow and therefore, by springtime, our bare metal engine side cowls will be bright yellow (and hopefully the fixed rudder trim tab as well). While researching the RCAF Stearman colours, a photograph was found showing an Alberta-based BCATP Stearman with a bare metal cowl cover. This, we believe, was the result of a repair and was not normal for Stearman aircraft. Perhaps that is why our aircraft at purchase had the bare metal cowls. An expert will be arriving soon with a special computer to figure out the exact shade of Federal Yellow required.

Some of you may have noticed that the blue colour of the roundels is a very incorrect shade of blue. Our roundel expert, Dave O’Malley created some new properly coloured roundels in decal form (yes, some decals were used on aircraft in Canada during the second World War). However, when applying the decals, it was discovered that the blue paint on the original painted on roundels was peeling off in large pieces under the just-applied decals. This meant that the decals would not adhere properly, so the blue paint is being removed by simply sticking tape to it and peeling it off. Electrical tape seems to work best. The aircraft has six roundels and two fin flashes.

Stearman is in fact the name of the manufacturer created by Lloyd Stearman initially in Venice, California and then moved to Wichita, Kansas. In 1934, the year of the Model 75's first flight, Stearman was purchased by Boeing which since that time has maintained its Wichita presence until its planned closure in 2013.

Several earlier aircraft types were designed by Stearman, but the model 75 that became its most successful type by far. Like the Finch and Tiger Moth, it came from earlier designs. In this case, the Model 75 was a militarized version of the civilian model 70 which itself had been a redesigned from the short-lived Model 6 Cloudboy. Several different engine types were used on the Navy and Army versions. Named as the Kaydet they were were fitted with Lycoming (PT 13), Continental (PT 17) or Jacobs (PT 18) radial engines. The export verion to Canada was the PT-27. A later, more powerful version of the Stearman, the Model 76, was purchased by Argentina, Brazil and the Philippines. The Model 76 with a Wright Whirlwind engine featured wing mounted .30 caliber machine guns, a bomb rack between the landing struts and a single machine gun for the rear cockpit. These aircraft were used as light attack or reconnaissance aircraft.

The Canadian version was supposed to be a winterized version like the Tiger Moth and Cornell, however, due to production delays, they were not delivered this way but as PT-17's. Although introduced into RCAF service, they were quickly withdrawn and returned to the US having been replaced by Cornells.

Our Stearman with its silver side cowls patiently awaits the end of its annual inspection. Note the silver bucket underneath due to the fuel leaking out the drain hole of the intake pipe.

Maintenance technician Vanessa helps with the compass swing on a nice November afternoon.  This picture gives a good view of the stagger which is especially noticeable at the trailing edges. Notice that there are twice as many flying wires as landing wires. All of them pass through the javelin. An N strut is used instead of incidence wires. As can be seen, ailerons are on the lower wings only.

In this picture, you can see the difference in blue shading between the newly applied Type A roundel in proper colours and the lighter blue fin flash. There are 6 roundels on the aircraft, however, the two on upper wings are type B which does not have any white in it.

Part way through the blue paint removal process on one of the roundels. Like the Cornell and the Tiger Moth, there are cutouts in the wingtip for handles to assist in ground manouvering. The Finch and Harvard did not have this feature.

Reminiscent of the snorkels sometimes seen on Australian off-road trucks, the air intake on the Stearman is on the top cowl which then drops straight down to the bottom of the engine compartment(passing the large green air filter housing in view) and the goes forward to the engine as can be seen on the lower right side of the cowl where it rises up to the carburetor. The rights side exhaust points straight out from the exhaust ring. In lower light conditions, flame can be seen here when the engine is running.

Last updated on Jan 29/2012

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