Flying wings

Flight Journal, Oct 2003 by Tucker, Charles, Quinn, J J

CONTROL SURFACES

The control surfaces on the N-9M, XB-35 and YB-49 were identical in operation. From the wing centerline they were: conventional flaps, elevons and trim flaps. The conventional flaps were like the flaps on any other airplane: for landing, they were lowered fully to increase drag and slow the airplane. They were never used for takeoff. Outboard of the flaps were the elevons, which functioned both as elevators and as ailerons, depending on control input. Nearest the wingtips were the trim flaps. These were split like clamshells; the top surface opened upward and the bottom surface opened downward. They were operated by the rudder pedals and fulfilled the same function as the rudder in a normal airplane. Pushing on a rudder pedal opened both surfaces of the appropriate trim flap to create drag on one side, and this would act like a rudder. In addition, they were used as trim tabs for the elevators and ailerons. They had one additional function that was sort of neat: when both rudder pedals were pushed at the same time, the upper and lower surfaces of both "clamshells" opened simultaneously to act as speed brakes.

THE XB-35

Following my experiences with the N-9M, I was assigned to fly as copilot in the XB-35 and YB-49. The copilot was rather superfluous, as the cockpit was in the leading edge of the wing, and the only visibility was straight ahead. You could not take off or land from this position, as there were no throttles or brakes. I flew about 50 hours in the XB-35, and in that time, I actually flew the airplane for about five minutes. That isn't much, but it was enough to know that I really didn't like it.

To this single-engine fighter pilot, the XB-35 and the following YB-49 were visually impressive. They were huge! Crew entrance was via stepladder through a two-foot by two-foot hatch in the belly. The first man aboard helped the rest of the crew in. Once aboard, getting to the crew stations was quite a job; it required crawling over, under and around various parts of the aircraft's structure. From the command pilot's seat, the view was magnificent! The biggest problem was that if an emergency exit became necessary, you were in trouble because there weren't any ejection seats. Getting out in an emergency would have been almost impossible. This was something you just tried not to think about.

The XB-35 was very sluggish in flight; it always felt as though it was just wallowing around in the sky. It had myriad problems, mostly centered on the engines and propellers. The airplane was underpowered to begin with, and the drive train and propeller arrangement added to the problem. The propellers were mounted at a large angle to the wing's chord line, a la the N-9M, and this considerably impaired efficiency. First, contra-rotating propellers were used, and the propeller gearbox was very weak. Problems with this gearbox quickly led to the redesign of the drive train to eliminate the contra-rotating feature and to use single-rotation propellers. This further reduced the efficiency of the propulsion system.