Flight testing the Boeing 747

[Music] [Music] from that moment boeing flight test personnel had their work cut out for them the decision had been made all tests required for federal aviation administration certification must be completed before the end of 1969. they had to carry out approximately 1500 hours of in-flight testing that would take the 747 to the outer limits of performance well beyond what would be required to meet all boeing and customer requirements as well as faa requirements it was a big tap it required using the first five airplanes built to get the job done on time each of the flight test aircraft had its own select crew and in general each aircraft had its own special assignment number three with a special nose boom would measure air gus during in-flight maneuvering while flying through turbulence and on landing number two concentrated on landing number one on stalls and system testing with plenty of work for all five aircraft the planning for that work all began when the 747 was just a paper airplane and the engineers began making the first of many performance predictions wind tunnel testing resulted in predictions about drag or wind resistance and resultant range and fuel consumption fatigue testing made it possible for engineers to predict structure life span static testing would establish outer limits just how much the aircraft could withstand and in this test the wing was flexed 26 feet from normal position one and one-half times the maximum load the airplane would ever be expected to encounter in normal airplane operations and still the wings did not break but even more testing was to follow the torture was continued till the wing failure finally occurred well in excess of all design criteria completion of this test resulted in still higher confidence in the structural integrity of the 747 and established a firm baseline for planning future operations at increased weight testing to these limits is not required by the faa but was accomplished at boeing's own option many tests were conducted at remote bases number one aircraft has to take off requirements and capabilities at edwards air base in california edwards has the longest runway in the united states weather conditions at edwards are very good too tests here included taking off for the aircraft three thousand pounds above the maximum takeoff weight and then cutting the fuel supply to one of the engines making it inoperative this not only showed the aircraft would perform as predicted but also that procedures to be used in such an unusual situation were satisfactory another test performed at edwards turned out more spectacularly than intended the test a refuse takeoff call for bringing the 747 up to its takeoff speed at which point all the brakes would be applied to bring the aircraft to a complete stop without use of the engine's thrust reversers the aircraft was brought to a stop in the required distance but the unexpected happened a malfunction in the anti-skid system resulted in excessive stress causing one of the tires to blow out and catch fire in order to comply with faa test regulations none of the standby emergency vehicles were permitted to come to the aircraft aid for five minutes that's judged to be adequate time for emergency vehicles to reach an endangered aircraft finally time was up the burning tire was quickly extinguished detailed examination showed no structural damage the test wasn't planned that way but it was reassuring proof that the landing gear had indeed been designed for safety to a large extent the success in meeting the test schedule was the result of the ground crews attitude the man treated the aircraft as if they owned them the result was a feeling of friendly competition to see which airplane could outdo the other each team was anxious to prove themselves and their airplane by taking on certain tasks number two airplane was sent to new mexico for landing performance tests refused takeoff and autopilot work the reception was impressive the whole town of roswell turned out to greet the crew the friendly attitude made it easier to put up with the long hours of work that were in store the braking system was given a severe workout all 747s are equipped with an anti-skid system when brakes are applied the wheels don't lock there is no skidding tests are conducted with the system in operation and with it in various failure conditions two wheels disconnected from the anti-skid all wheels disconnected and so forth to show the performance of the aircraft under varying conditions frequent visual checks are made of wheels landing gear and underside of the aircraft it's hard on brakes approximately 200 of them were used but it does prove the safety of the aircraft even when pushed well beyond normal operating limits while number two was in roswell number three was conducting hard landings at seattle tests proved that the landing gear is very forgiving even these hard landings felt soft and presented no control problems [Music] performance of the aircraft could only be judged in relation to environment it was essential for example to have accurate measurements of weather conditions at the time of each test a 10 mile an hour wind can make a big difference during landing flight manuals dictate the proper landing procedures and are very conservative the stall speed is established and then the plane is always operated 30 above that established stall speed there's always that extra built-in margin of safety the speed at which the 747 will stall and its reaction was established in approximately 500 tests conducted at various altitudes 747 excellent flying characteristics are evident stalls are gentle and fully controllable the 747's inherently good flying qualities were also evident during flutter testing a chase plane was used to help observe vibration or flutter induced by special red veins attached to the wings the aircraft was pushed to limit well beyond any that would be encountered in normal flight but the 747 reacted as predicted and the structures proved to be self-dampening the flutter or vibration did not amplify or grow recording devices were located throughout the aircraft and all control surfaces to radio information to monitoring ground stations engineers on the ground observed and confirmed results of the test and gave instructions or clearance to proceed to the next test situation during tests the aircraft reached a speed of mach .991 or just five miles less than the speed of sound at all speeds the 747 proved to be highly stable as often as possible testing was done concurrently it was frequently possible to conduct certain system tests hydraulic air conditioning electrical and so forth at the same time as a drag or level flight performance test this was one of the techniques that made it possible to complete flight testing in such a short time the 747 capability was evident during the spectacular vmu test which determines maximum takeoff performance in this test the tail section of the aircraft is purposely put in contact with the runway a hardwood skid protects the tail section the speed at which liftoff occurs is called the minimum unstick speed or vmu demonstrates the 747's ability to withstand inadvertent abuse as well as determining the aircraft's ultimate takeoff performance the most important time saver in the test schedule was the simultaneous use of five aircraft many different tests were conducted at the same time in many different locations taxi tests to prove visibility and ease of handling on the ground spray test at various speeds to check against water being ingested by engines or air conditioning testing the autopilot in various failure modes to prove that the pilot can always recognize any abnormal situation and control it [Music] landings at 35 to 40 knot crosswind hard landing with initial impact on the left or right gear shimmy testing nosegear linkage by machine grinding parts to simulate excessive wear and testing the results every test pushed the 747 limits it would never encounter in normal use massive amounts of data from these tests were then fed into computers real key to how such a complicated testing program was completed in such a short time analysis of all the data compiled would have required approximately 10 years without the use of computers ten months after the start of flight tests the results are in the 747 is all and more than the designers and engineers had said it would be it has proved its capabilities to the satisfaction of everyone involved including the people who issue the official certification of their worthiness the federal aviation administration as expressed in this statement by arvind basnite director of faa western region as a result of this effort which included some 1500 hours of test flying we are convinced this airplane beats or exceed standards for safety involved in civil aviation we therefore recommend that boeing 747 receive the faa types faa representatives charged with 747 certifications rode with boeing flight crew during critical tests and learned airplane performance capabilities first hand the joint effort of boeing and the faa resulted in a testing program that pushed the 747 to the outer limits of performance and proved the integrity of this advanced technology transport thus late december 1969 the 747 was certified as the largest jet aircraft in civil aviation history to the air traveler the result of the 747 extensive test program unparalleled comfort convenience and safety a new hallmark of excellence for airlines around the world [Music] you