Production of Defective Products Must Not be Continued

Engineers are the professionals whose responsibilities cover the creation of new products and processes for the good of human society, as well as to improve the convenience and beauty of our society. They are the people who make possible great technological leaps that were thought possible only in science fictions.

Major aeronautical and aerospace projects can take a long time to implement and incur a great cost. Cost overrun and project delay have great repercussion financially, sometimes even politically and socially. Correcting a design defect can incur a great cost and can lead to serious delays with dire consequences. Economic cost consideration itself may prohibit any major redesigning to be performed and so sometimes only remedial actions can be taken. The remedial actions, if at all carried out, may not always be enough to ensure good safety. In order to appreciate the problems faced by engineers when they have to manage design faults, we shall centered our discussion on the following two infamous cases:

1. Challenger Space Shuttle case
2. DC-10 Jumbo Jet Case

Case Number 1 - Challenger Space Shuttle

In order to better appreciate this case, it is useful for us to first look at some of the background information.

The main space vehicle in the space shuttle is called the orbiter. There are three main rocket engines in the orbiter. Most of the hydrogen fuel, together with the oxygen needed to support rapid engine combustion, is carried in a huge external tank. The tank is jettisoned when empty after about eight and a half minutes from lift-off.

Due to the heavy load and the nature of the hydrogen-fired rocket engines, additional thrust is needed to speed up the shuttle to escape from gravitational pull. Two solid rocket boosters are employed. Solid fuel is used because it provides much greater thrust than liquid hydrogen fuel. One disadvantage with the sold-fuel rocket is that once fired, it cannot be stopped until the fuel runs out.

Because of the heavy load and nature of the hydrogen fuel rocket, additional push is necessary to accelerate the shuttle to escape from the gravity pull. Two additional rockets that use solid fuel are employed because they can provide a push much larger than the equivalent liquid hydrogen fuel rocket engines. A disadvantage with the solid-fuel rocket engine is that once it fires, it cannot be stopped before the fuel is exhausted.

The booster rockets are huge and long. While the booster rockets are manufactured in the factory, they are manufactured in segments and transported to the space center in five segments. These five segments are put together at the launch site at the space center. Since the segments are joined together at the launch site, the joints are called field joints. The field joint design, while creative and with engineering ingenuity, was found to be less than desired. The redesigning process was slow and the new design was not ready. Tests had indicated less than desired performance for the existing field joint design especially when the operating temperature is low.

On the night before the Challenger space shuttle was to be launched on Jan 28, 1986, Morton-Thiokol, the maker of the solid rockets boosters, were worried that the solid rocket boosters might cause problem due to the cold weather. They held a teleconference with NASA managers to present their concerns and recommended that the launch be postponed till the temperature rose to a more suitable level.

The NASA managers rejected the recommendation as they believed the solid rocket boosters would be able to perform well, even at the expected low temperature of 26 degree Fahrenheit as their design called for performance at as low as 31 degree Fahrenheit. Under the pressure from NASA manager, Morton-Thiokol managers changed their recommendation to proceeding with the launch, despite the strong protests from their engineers who could not prove conclusive that the filed joints were indeed faulty.

Case Number 2 - The DC-10 Jumbo

In 1974, the first fully loaded DC-10 jumbo jet exploded over the suburbs of Paris, killing 346 people, a record at that time for a single-plane crash. This was said to be an accident waiting to happen because it was known to the designers that the design of the plane was defective because the cargo door could burst open during flight.

The fuselage of the DC-10 jumbo subcontracted to Convair by McDonnell Douglas. Dan Applegate worked as Convair senior engineer directing the project. Dan wrote a memo to the vice president of Convair identifying the various dangers that could arise from the design of the fuselage. He highlighted a few potential dangers, especially with regards to the possibility of disaster due to the failure of the cargo door. He detailed how the cargo doors could burst open during flight resulting in the decompression of the cargo space, leading to the collapse the floor of the passenger cabin above. When that happens, the control lines running along the cabin floor would be damaged and the plane could not be controlled.

The senior engineer therefore recommended that the doors be designed and at the same time strengthen the cabin floor. He warned that such making the changes as he recommended would lead to some of the DC-10 cargo doors being forced open during flight and plane crash would result.

While the top management at Convair did not disagree with technical analysis of Applegate or his warning, they maintained that Convair might face possible financial liabilities if they were to pass on this information to McDonnell Douglas. These liabilities could be severe since the cost of redesign and the delay to make the necessary safety improvements would be very high and would occur at a time when McDonnell Douglas would be placed at a competitive disadvantage.

Observations:
There are close parallels between the two cases. Both designs were known to be flawed by the engineers who tried to alert the management but the management decisions were clouded by monetary considerations which led to the eventual loss of the crafts and the lives of the occupants. In both cases, engineering hats were removed and management hats put on.

Published Articles: http://www.rhinoarticles.com/

Jacob Gan PhD (Michigan) has more than 20 years of teaching experience in a university and 8 years of business/industrial experience after graduation. He writes for succezz.com, JacobGan.com, JacobEducation.com, DemystifyCancer.com, understanding-orchids.com, motivate2success.com and JacobLearning.com. He hosts Jacob.TheeLearningcentre.com, an elearning portal.

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