sentences:  A copper tubing system was installed in an attempt to adequately lubricate the rocker arms of the engines inflight.Doorways were cut on each side of the cockpit and catwalks built on the wings to enable mechanic Roy Hooe to access the engines for emergency maintenance.To reduce propeller noise, the two wing engines were mounted with Westinghouse twin-blade Micarta propellers, while the nose engine used a Standard three-blade steel propeller.