Testing for Aviation Safety

Flying is by far the safest form of transportation. That is because the aviation industry and the government agencies that oversee air travel work really hard to make it safe. AerospaceAerospaceengineers do a lot of tests on airplanes and spacecraft before they are put into service. Let’s look at some of those tests.

Supersonic Bears!

Sometimes, flight testing can be very dangerous. So dangerous that it is not safe for people at all. So how can people make sure that aircraft are safe? One way is to use stand-ins for people. Let’s check out a few of these.

To get out of a fighter jet quickly most have ejection seats. In case of an emergency, an ejection seat is fired out of the aircraft by an explosive charge or rocket motor, carrying the pilot with it. You can imagine how dangerous a seat like that would be if it did not work properly!

Ejection seats have the potential to be even more dangerous when a plane is flying at supersonic speeds.

The first supersonic jet bomber was the Convair B-58 Hustler. It flew at about MachMach 2 (about 2 000 km/h or 1 320 MPH) and at an altitudealtitude of about 18 000 m (60 000’).

Image - Text Version

Shown is a black and white photograph of a large, sleek silver jet plane flying from left to right across a clear sky. It has a long, pointed nose, a large triangle-shaped wing, and a tall tail at the back of the plane. The nose and tail of the plane are red with a large white chevron on them. There are four large jet engines underneath the wing, and a large pod with a pointed nose and four fins at the rear under the body. Printed on the side of the nose are the words "Convair" and "B-58," along with an American insignia.

 

At the time, people were worried about what would happen to the crew if they had to leave the airplane when it was flying that fast and high. They were afraid that if they had to use regular ejection seats, the force of the supersonic airflow would almost certainly kill the crew as soon as they left the plane.

To solve this problem, engineers at the Stanley Aviation Company designed individual escape capsules for the plane’s three crew members.

Each capsule was fully enclosed and kept at the proper internal pressurepressure. This would protect the crew member from the extreme environment they may be launched into. The capsule also came with its own oxygen, food and water. It could even serve as a boat if it landed in water.

Image - Text Version

Shown is a black and white photograph of a large, sleek silver jet plane sitting on a runway in the desert with a clear sky behind it. The has a long, pointed nose, a large triangle-shaped wing, and a tall tail at the back of the plane. The nose and tail of the plane are red with a large white chevron on them. There are four large jet engines underneath the wing. Printed on the side of the nose are the words "Convair" and "B-58," along with an American insignia. There are four cranes and some scaffolds on the ground around the plane. The middle of the plane is covered with white smoke. There is a dark oval shape in the upper right of the photo, with dark smoke streaming back from it to the top of the plane.

 

But before it could be used with people, it first needed to be tested. Human dummies fitted with sensors were used for some tests. But engineers still needed to know what ejecting at supersonic speeds would do to a living creature. Engineers began with Chimpanzees and got some useful data, but it still wasn’t good enough. They wanted to test the capsule with an animal that was closer to a human’s size and shape. For this they turned to unlikely test pilots - black bears.

On March 21, 1962, a two year-old female black bear named Yogi became the second living creature to survive an ejection from a plane flying at supersonic speeds. To keep her calm, Yogi was slightly sedated for the test. She ejected from a B-58 flying at a speed of Mach 1.3 (1 300 km/h or 850 MPH) and at an altitude of 10 700 metres (35 000 feet). She safely landed 7 minutes and 49 seconds later.

Big John was another black bear who ejected from the B-58. He ejected at an even higher speed and altitude. His trip wasn’t as smooth as Yogi’s, though. His capsule tumbled in flight and landed hard. Big John suffered a few broken bones and some internal injuries, but he fully recovered. None of the bears ever flew more than one test flight.

The results of these tests helped engineers to perfect the design of the escape capsule. It also gave them the confidence to let a human try the escape capsule in flight. Although only a few aircraft have ever used escape capsules, this idea was a good solution to protecting aircrew who flew these types of aircraft.

Tests like these would not be done today because there are much stricter animal rights regulations. Testing would likely be done using computer models and simulators.

Did you know?

North American Aviation test pilot George F. Smith was the first person to survive ejection from a plane at supersonic speed. He made an emergency ejection from an F-100 Super Sabre at Mach 1.05 on February 26, 1955. He was very badly injured in the process. 

Flight Testing the Space Shuttle

Early human spacecraft were tested with unmanned flights before they ever flew with humans aboard. This was not possible when it came to the space shuttlespace shuttle. This spacecraft was launched like a rocket, but it came down to Earth like a glider.

Many wind tunnel tests were made with models of the space shuttle. But nobody really knew what it would be like to fly the space shuttle once it came back into the Earth’s atmosphere for landing.

NASANASA engineers came up with a bold idea for how to fly the space shuttle without sending it into space. A specially modified Boeing 747 has already been built to carry the space shuttle from its landing sites back to the Kennedy Space Center. Why not use this 747 to carry a space shuttle up into the air and then release it to fly back to the ground on its own?

This posed a lot of problems. For one, the 747 had to fly in a very precise way so that the space shuttle would safely separate it. The 747 would need to fly in a shallow dive in order to release the shuttle. Then, while diving, the 747 would slowly pull down away from the shuttle. Technically, the 747 was dropped by the space shuttle!

Another problem was having two very large aircraft fly so close to one another. No one was sure how the air moving around the two aircraft would affect each other. This made people very concerned that the two planes could collide. But in the end, NASA decided that there was no other way to give test pilots experience flying and landing the space shuttle.

Five Approach and Landing Tests were flown over the California desert at Edwards Air Force Base in 1977.

The fifth test flight revealed a potentially dangerous problem with the flight control system, but the shuttle Enterprise was able to land safely.

Data from these tests helped engineers perfect the space shuttle’s flight control system. It also let pilots develop procedures for flying the space shuttle.

All of this testing paid off. During 135 missions, no space shuttles had accidents during landing.

Image - Text Version

Shown is a photograph of a large silver jet airplane flying from right to left with a large white rocket plane above it, in a blue over a mountainous desert. The jet plane is pointed slightly downwards, Two silver, red, barrel-shaped engines can be seen below the left wing, and there are struts on the top of the plane. There are many small windows visible along the side of the airplane. At the front of the airplane, the top is bulged, with windows for the pilots at the front of the bulge. There is a red, white, and blue white stripe running along the side of the plane, with the word "NASA" printed in red on the tail, with the number "905" in black below the word. The rocket plane is just above the top of the silver plane. It is about half as long as the silver plane, and has a black nose and belly. The word "United States" is printed in black on the side of the rocket plane just above the wing. Three large black, cone-shaped rocket engines are at the back of the rocket plane.

 

Learning From Accidents

Aircraft and spacecraft are some of the most complicated machines ever built. You can imagine that if any system doesn’t work properly, terrible things can happen. This is why lots of planning and testing goes into aerospace engineering. Which isn’t to say that accidents don’t happen.

When accidents occur, engineers quickly go to work to try to figure out what happened. Then they suggest ways to prevent similar accidents from happening again.

Did you know?

Countries around the world have agencies that investigate aircraft accidents. In Canada, the Transportation Safety Board is responsible for the investigation of all accidents involving transportation.

The Comet Disasters 

Aviation often involves new technology. But sometimes problems with new technology are not really understood until accidents happen.

For example, Britain built the world’s first jet airliner in 1949. This was the de Havilland Comet. The Comet flew much faster and higher than any other airliner at the time. It was also much quieter and more comfortable for passengers. It looked like Britain would be the world leader in airliners for years to come. Then in early 1954 the world was stunned by two Comet crashes that killed everyone onboard.

Image - Text Version

Shown is a photograph of a large, sleek jet airliner sitting on a runway with a cloudy sky behind it. To the right of the airplane is a three-storey building with antennas on top of it. The plane has a sleek, rounded nose with windows for the crew in the front. There is a row of windows along the side of the plane, inside a dark stripe that runs along the middle of the side of the plane. Below the stripe, the plane is silver, and above the stripe the plane is white.  Printed above the windows at the middle of the plane are the letters "B O A C." There are two oval openings for the jet engines in the right wing, right beside the body.

 

A major investigation was launched into the cause of these two crashes. Underwater television cameras were used for the first time to locate the wreckage of the first aircraft to crash. The Royal Navy recovered much of the wreckage for analysis.

As a result, investigators concluded that the metal had failed after being stressed by the repeated pressurizingpressurizing and depressurizingdepressurizing of the fuselage. These pressure changes happened when the plane climbed and descended from its 12 000 metres (40 000 feet) cruisingcruising altitude. Other design features, like the method of rivetingriveting and the square cabin windows, also contributed to the crash. The main lesson learned from these crashes was how the wear and tear of flight could affect the metal used in aircraft. This lesson influenced the design of all airlines that came after.

Crash Tests

Not all of the crashes that engineers study are accidents. Sometimes, the only way to understand what happens when an aircraft crashes is to crash one on purpose. Crash tests are very carefully controlled experiments. They help engineers observe how a plane’s structure and systems behave when it hits the ground. These tests are very carefully planned, because engineers often have only one chance to get it right!

One of the most famous crash tests was the Controlled Impact Demonstration (CID). This test involved the crash of a real Boeing 720 jet airliner in the California desert. The aircraft was remotely piloted and there were 113 ‘passengers’.These were crash test dummies.

NASA and the US Federal Aviation Administration ran this test on December 1, 1984.

Image - Text Version

Shown is a colour photograph taken inside an airliner looking towards the rear of the plane. The plane is filled with rows of red seats, with a walkway down the middle and each row having three seats on each side of the walkway. Most of the seats have adult-sized crash test dummies in tan pants and shirts strapped into them, but the front seat in the middle of the photo has a child-sized crash test dummy strapped into it. Cables run along the floor of the walkway, and test instruments are visible at the back of the plane. The plane's windows can be seen beside the outboard seats.

 

The test took four years to plan. It had three goals:

1. To test an anti-misting kerosene fuel, which was supposed to have less of a chance of catching fire in a crash.
2. To gather data about how aircraft design impacts the chances of passengers and crew surviving a crash; and
3. To test the effectiveness of seat belts and seat attachments for passengers in jet airliners.

Aside from the special fuel that was being tested, a number of cabincabin safety improvements were also on board. These included fire-resistant windows and interior materials and crash-resistant flight data recordersflight data recorders.

Did you know?

This was the first time that a four-engine jet aircraft had been flown by remote control. 

In the test, the aircraft was supposed to approach a runway with the landing gearlanding gear up. It was then to fly very low between two sets of steel posts. The steel posts were to rip open the wings and let the fuel out. The aircraft would then skid to a stop. Engineers hoped that it would land in such a way that would allow most of the passengers to survive. To record what happened, the aircraft was filled with sensors and high-speed cameras were used to film the crash in slow-motion. This allowed engineers to study what happened during the crash in great detail.

The test did not go as exactly as planned... As the plane was approaching the runway, the nose began to turn or yawyaw to the left. This resulted in the left wing hitting the ground earlier than it was supposed to. When the plane hit the posts, they tore the fuselage open, and the plane burst into flames. The test of the non-exploding kerosene had obviously failed. In spite of the fireball, investigators thought that about 26-28 of the dummies would have survived the crash and fire. Nonetheless, the data gathered from the CID was still very useful and led to many safer airliners.

Conclusion

Testing plays a very important role in aerospace engineering since people’s lives are at stake. Aerospace engineers use all sorts of innovative tests to make planes fly higher, faster, farther, and safer. Thanks to the efforts of aerospace engineers, air transport is the safest as well as one of the most exciting ways for people to travel.