President Obama’s oil spill commission spent six months examining the “root causes” of the Gulf disaster, yet never inspected the failed blowout preventer — the part of the well that could have, as its name suggests, prevented the explosion.

At a House Natural Resources Committee hearing this week, the co-chairmen of the National Oil Spill Commission faced a barrage of questions from Republicans and Democrats about why their final report is long on regulatory recommendations but short on engineering explanations.

Lawmakers took issue with the commission’s apparent lack of effort to explain the failure of the blowout preventer. Republicans said it calls into question the commission’s recommendations — and, more seriously, leaves the Gulf vulnerable to a similar malfunction in the future.

“Why should we take [the commission] seriously if [it] did not even make that modicum of effort to determine the actual cause of the disaster?” asked Rep. Tom McClintock (R-Calif.). “We’ve never had a blowout failure like this one. Until we find out why it failed, it could happen again. It could happen anytime — and the commission has not advanced our understanding of how to prevent that. … We have before us a report recommending bureaucratic solutions to engineering problems authored by bureaucrats rather than an engineering solution authored by engineers.”Up until Wednesday’s hearing, the oil spill commission has largely avoided sharp questioning. Its 381-page final report on “The Gulf Oil Disaster and the Future of Offshore Drilling” was released earlier this month, the result of six months of research.

Republican lawmakers expressed alarm that the commission — made up of Obama appointees who lack engineering experience — would offer recommendations without attempting to identify the precise mechanical cause of the Deepwater Horizon oil rig explosion.

“We still don’t know what caused the explosion,” said Natural Resources Chairman Doc Hastings (R-Wash.). “We don’t know how or why the blowout preventer malfunctioned.”

Commission co-chairman and former Sen. Bob Graham (D-Fla.) responded: “It is true that no one at this point has had the benefit of a full examination of the blowout preventer. What we do know is that it didn’t perform as it should have.”

When Obama created the commission last May, its top priority was to “examine the relevant facts and circumstances concerning the root causes of the Deepwater Horizon oil disaster.”

The commission’s report heavily explores the human error and managerial mistakes behind the spill — again, at the relative expense of exploring the technological causes. It could have done both, McClintock said, citing the work of the Rogers Commission, which examined the causes of the 1986 explosion of the space shuttle Challenger.

“When the Challenger exploded, people only knew one thing for sure after the accident — that this was a launch that was fatal and catastrophic,” he said. “The Rogers Commission was a panel that was filled with technical experts that painstakingly recovered the wreckage from underneath the ocean and reassembled that wreckage and then determined the precise cause of the disaster. It then recommended changes so that the space program could move forward.”

Commission co-chairman William Reilly deflected criticism and defended the report. Reilly, a former Environmental Protection Agency administrator, drew an interesting analogy.

“I think you can draw an analogy between a blowout preventer and a seatbelt in an automobile accident,” Reilly said. “It’s obviously important to the survival of someone that a seatbelt wasn’t fastened, but it doesn’t really explain why the accident occurred. We explain why the accident occurred. We identified all the major contributors. … Examining the blowout preventer is not going to cause those other factors that we have covered to go away. They are there, they are distressing and they do have implications for policy.”

Those policy implications worry some committee members. The report’s imbalance suggests a desire to limit the capabilities of the oil industry, which is evident from the phrase “systemic, industry-wide failure” — without examples from more than three companies to back up its use. In fact, the report implies the need for a complete governmental overhaul of the industry when no such overhaul is needed.

“Here’s the issue,” Rep. Bill Flores (R-Tex.) said. “Congress has considered legislation, the Department of Interior has issued new regulations, lease sales have been canceled, other areas of potential offshore activity have been put off-limits again and it’s all based on a report that doesn’t give a full post-mortem of what happened.”

Even committee Democrats questioned the report’s most sweeping claim.

“Some of the verdicts, sometimes even just the words used in the report, I kind of have some concerns about,” said Rep. Dan Boren (D-Okla.). “One was the use of the term ‘systemic,’ that there are ‘systemic’ problems in the industry. If you look at a 30-year history, over the last 30 years, the history of the offshore oil industry, there have been some incidents, but I think a major incident is very rare and, if you compare it with the airline industry or the consumer trade industry, the oil and gas industry has done quite a good job.”

But Reilly and Graham stood behind this conclusion. While the report only cites as safety offenders three companies, those companies are highly prevalent in the industry, they said.

“It is simply inconceivable to us that this is a problem so exclusive, so especially circumstantial to one rig,” Reilly said.

That perspective is likely to shape future policymaking, a point that wasn’t lost on Flores. “This report is being relied upon to continue moratoria, either de facto or regulatory or however they want to be described, and it goes back to this ‘systemic, industry-wide’ failure comment.”

Going one step further, Flores asked the commission to remove the phrase from its report.

“Based on what I see, and the weight which this report is being given for the energy future of this country, I would respectfully ask the commission to remove from the report the phrase, ‘systemic, industry-wide failure.”