Two Crashes and WWII
In the 1930s Boeing had as many as six full scale engineering development (FSED) programs for new airplanes going on at the same time. Some of the planes under development were significantly more complicated, and thus took longer. Because of this, the sequence of first flights was not in same order as the model numbers might indicate. Thus, the first flight of the Model 314 Clipper or "flying boat" occurred nine months before that of the much smaller, yet far more complex Model 307. Something happened on that first flight of the 314 which should have sounded an alarm on all of the programs, and this did not happen.
Test pilot Eddie Allen got the 314 airborne out on Elliott Bay in Seattle only to discover that he had no ability to steer the plane. An engineer who happened to be on board was able to open a hatch on the crown of the plane with the idea of taking a look to see if there was something wrong with the rudder. Much to his amazement, even though they were flying, there was no wind at the hatch. The rudder worked fine, it was just in a zone of "dead air" created by the enormity of the zone of turbulence around the giant fuselage of the plane. It would take two more test flights, each after making changes to the design of the tail, before they came up with a triple tail configuration that worked.
The tail or empennage of a plane has several functions. One is obviously to serve as a mount for the rudders and elevators that control the pitch of the plane and enable it to turn (this is a huge over simplification). Another is simply to balance the many forces on the plane in flight and trim or stabilize the plane so it can fly smoothly in the direction intended. Think of the feathers on an arrow. The word empennage comes from the French word for adding feathers to an arrow. The English word for the same thing is fletching, but I digress. What should have been suggested by the steering issues on the first few 314 test flights was that there might be some stabilizing issues as well. Boeing was designing its vertical fin or stabilizer on all of its planes far too small to be able adequately stabilize the flight path of a plane, especially when extreme conditions were encountered, such as when multiple engines might cut out on the new four engine planes.
The 314 test flights should have prompted a bunch of wind tunnel testing of all of the designs under development. It did not. This would quickly lead to a disaster.
The 307 was a revolutionary aircraft that pushed the aviation envelop beyond anything that had ever been tried. The idea was to make the plane into a flying pressure tank with supplemental emergency oxygen supplies so it could fly high above the clouds and most weather. Another benefit of flying high where the air is much thinner, is that the range of plane is greatly extended. The 307 would provide a whole new level of passenger comfort for commercial airlines and enable the plane to fly much farther and faster than any other passenger plane at that time.
As can be seen in this photograph taken shortly before it was to crash, killing all on board, both engines on the right side of the plane have been shut down and the rudder has been moved quite a bit to the left to compensate for the effect of the engines on the left trying to force the plane to turn to the right. On board, in addition to the Boeing test flight crew was a team of guests from KLM who were evaluating the plane for possibly making it the cornerstone of their airline. Soon after this picture was taken, they also deliberately shut down the inboard engine on the left as well, leaving only the far left engine (number one, as the pilot thinks of them). The tail and rudder were not big enough to counteract the forces that the outboard left engine was then applying to the plane. It went into what is called a "flat spin" from which they were unable to recover, probably because the flight crew was being pressed to the left in their seats and anyone not buckled down being thrown hard into the left side of the interior as their plane became more like a fast spinning top. The vertical fin design and testing process for Boeing airplanes changed after that sad day.
As a side note, a few years ago Bob Bogash and I were able to tape an interview with the last surviving eye witness to that crash. That video is available in the archives of The Museum of Flight in Seattle.
But the key story here is the impact that these events began to have on everyone who worked for Boeing at the time. The attention to detail and the way people approached their work started to evolve in a much more open and positive way. Wind tunnel testing, and a process of doing a paper analysis of everything that could go wrong in an aircraft design, and formulating tests and design improvements became a discipline in its own right. Eventually, this process would become known as "Failure Mode Analysis" on the defense side of the company, and "Failure Mode and Effects Analysis" on the commercial side, but they are both the same thing. Boeing learned that if you wanted to build a safe plane, performance of a very rigorous Failure Mode Analysis was an absolute requirement.
The Boeing 345, better known by the Army Air Corps' designation as the B-29 Superfortress, was a super secret plane being developed for use in the Pacific Theater of WWII. Other planes simply did not have the range, service ceiling (how high they can fly) and payload needed to fight a war over that vast ocean. It may be helpful here to refer to my section explaining how an airplane flies in order to understand the complexity of the systems that needed to be added to an airplane to give it the ability to meet these mission requirements. Click here for that.
Engines, fuel systems, and hydraulics would all be pushed beyond anything that had yet been produced. The challenge was to get it airborne, with a full load of fuel and bombs, using a runway of two miles in length or less. Engines, fuel systems, and hydraulics would all be pushed beyond anything that had yet been produced.
When installing the tubing for fuel and hydraulic lines on a plane, in some spots it can be difficult to keep the fittings on the first end one tightens tight, while you go to the other end of the line and tighten the fitting there. The direction of turn to tighten the second fitting is the same as loosening the first one. In an airplane factory, cleaning up hydraulic spills from pressure testing is not an uncommon occurrence. Fuel system testing is done outside in a special parking spot where spills can be contained. It is also possible to get your fittings just tight enough to pass a pressurization test, but not tight enough to prevent the vibrations one experiences in flight from nudging them loose. Another challenge can be to simply remember to tighten every fitting when many are in the same vicinity. A momentary distraction during assembly can have huge consequences if not caught.
While we don't know exactly what happened on the first flight of the second 345 prototype, in all likelihood, a fuel line came loose, and it happened to be close enough to spray some part of the engine or exhaust that was hot enough to start a fire. Eddie Allen and his crew were unable to make it back to Boeing Field before losing so much altitude that they crashed into the Frye meat packing plant. All eleven people on board the plane and nineteen in the factory perished. Quality checks and the rigor associated with assembly and pre-flight checks, while already thought to be demanding, became ever so much more so after that.
The Boeing 299, better known by the Army Air Corp's designation as the B-17 Flying Fortress, was the stable mate of the 307. They shared the same wings, horizontal and vertical stabilizers, landing gear, and many systems. The plane became somewhat of a legend for the amount of damage it could sustain and still be landed safely. The addition of a dorsal fin on top of the fuselage and an enlargement of the vertical fin helped. The lessons learned in the 307 crash saved a lot of lives of wartime aircrews. But those damaged planes needed to be rebuilt on-site and gotten back into service as fast as possible.
As mentioned above, Boeing placed support personnel at the forward bases to assist in keeping the planes flying. Out of this service was born what came to be called the AOG (Aircraft On Ground) organization. These teams had blanket authority to grab whatever they needed to repair a plane. It was not unusual for an AOG team to show up at one of the factories where the planes were being assembled . There were three assembly factories, one each operated by Boeing, Lockheed's Vega division, and Douglas - jokingly referred to as the BVD team (think of the references to "Calvin" in the film "Back to the Future"). These teams had the authority to take whatever they needed right off the assembly floor. It could be a whole wing or other major subassembly. The thinking was that it was a lot quicker to repair a plane at a forward base than wait until a new one was finished to replace it. This extreme focus on doing whatever it took to help the customer stay in the air had the effect of extending the same culture that was in the engineering areas and factories out to wherever a Boeing product happened to be. Supporting the customer's mission was was baked right into the DNA of the company.