Tag Archives: faulty design

A single human error resulted in the deadly SpaceShipTwo crash

By Kim Smiley

The National Transportation and Safety Board (NTSB) has issued a report on their investigation into the deadly SpaceShipTwo crash on October 31, 2014 during a test flight.  Investigators confirmed early suspicions that the space plane tore apart after the tail boom braking system was released too early, as discussed in a previous blog.  The tail boom is designed to feather to increase the drag and slow down the space plane, but when the drag was applied earlier than expected the additional aerodynamic forces ripped the space plane apart at both high altitude and velocity.  Amazingly, one of the two pilots survived the accident.

Information from the newly released report can be used to expand the Cause Map from the previous blog.  The investigation determined that the pilot pulled the lever that released the braking system too early.  Even though the pilots did not initiate a command to put the tail booms into the braking position, the forces on the tail booms forced them into the feathered position once they were unlocked.  The space plane could not withstand the additional aerodynamic forces created by the feathered tail booms while still accelerating and it tore apart around the pilots.

A Cause Map is built by asking “why” questions and documenting the answers in cause boxes to visually display the cause-and-effect relationships. So why did the pilot pull the lever too early?  A definitive answer to that may never be known since the pilot did not survive the crash, but it’s easy to understand how a mistake could be made in a high-stress environment while trying to recall multiple tasks from memory very quickly.  Additionally, the NTSB found that training did not emphasize the dangers of unlocking the tail booms too early so the pilot may not have been fully aware of the potential consequences of this particular error.

A more useful question to ask would be how a single mistake could result in a deadly crash.  The plane had to be designed so that it was possible for the pilot to pull a lever too early and create a dangerous situation.  Ideally, no single mistake could create a deadly accident and there would have been safeguards built into the design to prevent the tail booms from feathering prematurely.  The NTSB determined the probable cause of this accident to be “failure to consider and protect against the possibility that a single error could result in a catastrophic hazard to the SpaceShipTwo vehicle.”  The investigation found that the design of the space plane assumed that the pilots would perform the correct actions every time.  Test pilots are highly trained and the best at what they do, but assuming human perfection is generally a dangerous proposition.

The NSTB identified a few causes that contributed to the lack of safeguards in the SpaceShipTwo design.  Designing commercial space craft is a relatively new field; there is limited human factors guidance for commercial space operators and the flight database for commercial space mishaps is incomplete. Additionally, there was insufficient review during the design process because it was never identified that a single error could cause a catastrophic failure. To see the recommendations and more information on the investigation, view a synopsis from the NTSB’s report.

To see an updated Cause Map of this accident, click on “Download PDF” above.

Nearly 2.6 million GM Vehicles Recalled, Costs Soar to 1.3 Billion

By Kim Smiley

During the first quarter of 2014, General Motors (GM) recalled 2.6 million vehicles due to ignition switch issues tied to at least 13 deaths.  Costs associated with the issue are estimated to be around $1.3 billion and, possibility even more damaging to the long term health of the company, is the beating the company’s reputation has taken.

The ignition switch issues are caused by a small, inexpensive part called a switch indent plunger.  An ignition switch has four main positions (off, accessories, on, and start) and the switch indent plunger holds the ignition switch into position.  In the accidents associated with the recent recall, the ignition switch slipped out of the on position and into the accessories position because the ignition switch plunger didn’t have enough torque to hold it in place.  When the ignition is put into the accessories mode, the car loses both power steering and power braking, and the air bags won’t inflate.  It’s easy to see how a situation that makes a car less safe and more difficult to control can quickly create a dangerous, or even deadly, situation.  Additionally, it’s important to know the problem is most likely to occur when driving on a bumpy surface or if a heavy key ring is pulling on the key.

The other key element of this issue is how the problem has been handled by GM.  There are a lot of hard questions being asked about what was known about the problem and when it was known.  It is known that the faulty part was redesigned in 2006 to address the problem, but the new design of the part wasn’t given a new part number as would normally be done.  Multiple federal inquiries are working to determine when it was known that the faulty parts posed a danger to drivers and why there was such a long delay before a recall was done.  The fact that the redesigned part wasn’t assigned a new part number has also lead to questions about whether there was an attempt to cover up the issue. GM is not civilly liable for deaths and injuries associated with the faulty ignition switches because of its 2009 bankruptcy, but the company could potentially be found criminally liable.

No company ever wants to recall a product, but it’s important to remember that how the recall is handled is just as important as getting the technical details right.  Consumers need to believe that a company will do the right thing and that any safety concerns will quickly and openly be addressed.  Once consumers lose faith in a company’s integrity the cost will be far greater than the price of a recall.

If you drive a GM car, you can get more information about the recall here.  The recalled models are Chevrolet Cobalts and Pontiac G5s from the 2005 through 2007 model years; Saturn Ion compacts from 2003 through 2007; and Chevrolet HHR SUVs, and Pontiac Solstice and Saturn Sky sports cars from 2006 and 2007.

To view the Outline and Cause Map showing the root cause analysis of this issue, please click “Download PDF” above.  Or click here to read more.