When the Navy discovered an exam-cheating ring aboard one of its submarines, it swiftly fired the commanding officer and kicked off 10 percent of the crew.

Navy officials describe the case aboard the USS Memphis as a rare lapse in integrity, but some former officers say the shortcuts exposed by the scandal are hardly unique to a single vessel.

The former submariners tell The Associated Press it is not uncommon for sailors to receive answer keys or other hints before training exams. They say sailors know how to handle the nuclear technology, but commanders competing with one another to show proficiency have made tests so difficult — and so detached from the skills sailors actually need — that crew members sometimes bend the rules.

An investigation report obtained by the AP through a Freedom of Information Act request describes an atmosphere aboard the USS Memphis that tolerated and even encouraged cheating: Sailors were emailed the answers before qualification exams, took tests outside the presence of proctors and openly asked officers for answer keys. One sailor told investigators that test-takers were encouraged to "use their time wisely" during breaks, insinuating that they should look up answers to exam questions.

A submarine force spokeswoman, Navy Cmdr. Monica Rousselow, said the Navy holds its officers and crew to very high standards and denied that cheating is rampant.

"The evidence we have shows that it's very rare," said Rousselow, who is based in Norfolk, Va.

But three former officers said the episode aboard the Groton, Conn.-based Memphis was an extreme example of shortcuts that occur aboard many of the roughly 70 American submarines in service.

One of the former officers, Christopher Brownfield, wrote in a book published last year that his superiors aboard the USS Hartford urged him to accept an answer key to pass a nuclear qualification exam. He said other crew members received answers by email, and the sub's leadership ignored him when he complained about cheating.

"It was almost universal," Brownfield said in an interview. "I don't know anybody on the ship who could have passed that exam without cheating on the first try."

As an instructor at the Navy's submarine school in Groton in 2005, Brownfield said he heard from members of roughly a dozen other crews that cheating also took place on their boats. He blamed pressure to hit ever-higher performance targets.

"They've expected more and more paperwork, with higher levels of compliance, and over time those expectations diverged from what people are actually doing," said Brownfield, who is now researching nuclear sustainability as a graduate student at Columbia University. "In the nuclear department, the test became so difficult it really had no bearing on what people were doing on a daily basis."

Two other former submarine officers who spoke to the AP on condition of anonymity for fear of losing connections to the Navy said that cheating is pervasive.

"Most people have great integrity except in this one area. On a lot of boats, they'll bend the rules and try to juice the results," said one former officer. He said it was not unusual for crew members on his submarine to receive hints to study particular areas before exams. As an instructor at the submarine school, he said he learned of similar practices on other subs.

Submariners have to make it through rigorous, highly technical training and testing before going to sea. Once deployed, they face more exams to test their knowledge and preparedness for worst-case scenarios. Low scores can lead to consequences up to removal from a sub, and hurt the overall rating of the crew.

The scandal aboard the Memphis broke in November when Navy brass learned that an answer key to one such test had been discovered in a junior officer's email.

The sub's commanding officer, Cmdr. Charles Maher, was relieved of duty within two weeks. He wasn't accused being involved in the cheating, but the Navy said he fostered an environment that failed to uphold the expected standards of integrity. He did not respond to messages left by the AP.

Of the 13 crew members who were punished, only three returned to the Memphis for its final deployment. The other crew members were reassigned, kicked out of the Navy or are awaiting possible dismissal, said Navy Lt. Jennifer Cragg, a submarine group spokeswoman at Naval Submarine Base New London in Groton. The 33-year-old submarine was decommissioned in April.

John Fischer, a former officer who used to help oversee exams from a Navy base in Washington state, said the tests are about much more than the knowledge displayed by individual test-takers. Officers aboard each sub create their answer keys, and the process is meant to sharpen the superiors' skills as well. He said the exams are supposed to be difficult, with a certain number of failures designed in to identify areas for improvement.

He said the collegial atmosphere aboard a submarine, where exams are administered by fellow shipmates and even friends, could be a factor in the cheating.

"If you get one guy in there who doesn't have the integrity to do the right thing, then it can progress really easily," said Fischer, who now works as a manufacturing engineer.

Like the other ex-officers interviewed for the story, Fischer said the safety of the reactors is not in question.

A spokesman for Naval Reactors, the agency that oversees the Navy's nuclear propulsion program, said the Navy works diligently to understand the root causes of any cheating case and to make changes. Spokesman Thomas Dougan said that out of 16,000 nuclear-trained officers and enlisted sailors taking several exams annually, there are on average one or two cheating cases per year that result in the removal of nuclear qualifications. Most cases involve only a few sailors, he said.

Dougan said the written exams are one of several measures used to assess the effectiveness of a continuing training program, and the kind of cheating that occurred on the Memphis would not put the ship or reactor plant at risk.

He said commanders use other measures, including supervisors' observations, drills and oral exams, to assess how well-trained crews are.

On the Memphis, the Navy investigation concluded that some of the mechanical operators decided to cheat partly because problems with the exam's design prevented questions from lining up with the expected answers. Five of eight sailors stopped using the answer keys after the problems with the exams were addressed, the report said. It suggested that the exam program could be improved by requiring that all qualification exams be proctored.

In light of the scandal, Rousselow said squadron commanders and commanding officers have been encouraged to make any changes that might be necessary to prevent such cheating. She said the Navy was leaving it up to commanders to determine what steps if any should be taken to implement lessons learned from the Memphis.