The crusty salts in the Navy often say that “sailors belong on ships and ships belong at sea.”

It’s no secret that sailors are busier than ever, especially those who are on sea-duty. Still, the reality of how much time individual sailors spend away from home might surprise you.

Sailors based in Japan, for example, may not spend any more time away from their home port than sailors based on ships back home on the East and West Coasts. (But those based in Rota, Spain do.)

Submariners, overall, spent far less time away than sailors in the surface fleet.

And aviators are typically extremely busy, especially those who operate the Navy’s mine-hunting helicopters and the carrier-onboard delivery C-2 Greyhounds.

“Operational tempo,” a term under the Department of Defense’s microscope after two fatal ship collisions killed a total of 17 sailors last summer, is a separate measure that doesn’t take into account the entire time a sailor spends away from home.

Personnel tempo, or PERSTEMPO, on the other hand, measures the number of days each sailor spends away their home port on official Navy business. The moment a sailor leaves a home port, the PERSTEMPO clock starts.

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The data “allows the Navy to monitor...how much time sailors are spending away from their home port...away from their families,” said Lt. Cmdr. Daniel Day, Navy spokesman at the Pentagon.

Tracking this data “allows us to ensure proper compensation for those sailors who spend more than 220 consecutive days in a deployed status,” he added.

Navy Times obtained the last three years — FY15 to FY17 — of PERSTEMPO data for the entire Navy from Navy Personnel Command. That information was then broken down by individual commands.

And while Navy officials stress that PERSTEMPO data is more about individual sailors than unit operational tempo, they do admit there’s some overlap.

According to Day, the data could be “skewed by people who detached and reported during a specific time frame, individuals who may ‘cross-deck’ to another command during extended maintenance.”

But Navy officials could not say how much the data would be skewed or in what direction.

“What was provided is what the fleet reported to NPC,” a source familiar with data collection process said. “It’s a requirement for commands to report the data about their people and we trust that commands are doing what’s required of them.”

Collecting Navy Personnel Command data another three years from now could arguably look drastically different due to the ever-changing landscape of operational demands. And ships that appear the busiest now will likely change in that span, Navy officials say.

WHAT THE DATA SHOWS

The data provided spans sailors from 221 ships and submarines, and 121 aviation squadrons.

According to the numbers from Navy Personnel Command, sailors stationed on surface ships spent an average of 23 percent of their time away from home, submariners spent 15 percent of their time away and shipmates in aviation squadrons — of all aircraft types — were gone 23 percent of the time.

To get a sense of which command’s sailors were busiest over the three-year span, the numbers from each command were stacked up against one another.

A total of 25 commands had PERSTEMPO totals that topped the 33 percent mark, meaning that on average, these sailors were gone for one whole year over the course of three.

The list obtained by Navy Times contains four aircraft carriers and 12 carrier-based helo and fixed-wing squadrons, eight guided-missile destroyers, one guided-missile cruiser, three amphibious ships, one attack submarine, two guided-missile submarines and three patrol squadrons.

When looking at the forward deployed sailors in Japan, PERSTEMPO data shows that those assigned to the Yokosuka-based cruisers, destroyers, carrier and command ship were away from their home port about 23 percent of the time. This is compared to 24 percent of time spent away for their U.S.-based counterparts.

In layman’s terms, Japan- and U.S.-based sailors are in a near-dead heat in terms of time spent away from home.

The 7th Fleet destroyers Fitzgerald and John S. McCain, which were involved in last summer’s fatal collisions, had reported PERSTEMPO numbers during the three-year span of 32 percent and 30 percent, respectively. Of the destroyers based in Japan, the Fitz and McCain were among the three busiest, the data showed.

Overall, destroyer sailors of FDNF Japan were reported to be away from home 24 percent of the time, an identical number to the rest of the Navy’s destroyer sailors.

On the other side of the world, however, sailors aboard FDNF ships based in Rota, Spain, were shown to be the busiest during the three-year span, spending a reported 35 percent of their time away from their home port, more than 10 percent busier than anywhere else.

Navy-wide, destroyers continue to prove they are the real workhorses of the surface Navy. PERSTEMPO data shows that sailors from 18 destroyers were away, on average, 30 percent or more of the time.

One destroyer, the Norfolk-based Ramage, has a reported being away from home 45 percent of the time over the past three years, the highest in the Navy over that time.

The Ramage provides the best example of the difference between personnel and operational tempos. Although sailors aboard Ramage have worked up and deployed during the last three years, the PERSTEMPO data also captures the ship’s six-month maintenance period that it spent in Pascagoula, Mississippi.

Counter to the increasingly active destroyer sailors, sailors aboard cruisers are reportedly away from home at an average rate of 22 percent. The FDNF Japan-based cruisers, meanwhile, reported sailors as being away only 20 percent of the time.

The Monterey and Anzio were the only cruisers that reported sailors being away from home 30 percent of the time or more during the past three years.

Cruiser-based sailors, however, weren’t operating as much as their destroyer brethren during the three-year span because a number of cruisers were undergoing modernization programs, a factor that most likely lowered the PERSTEMPO numbers. It’s reasonable to expect, once the modernizations are complete, for the PERSTEMPO of these sailors to increase over the next few years.

Carrier, destroyer, cruiser and amphib sailors who spent the most time away from home, according to PERSTEMPO data from FY15 - FY17. (Source: Navy Personnel Command / graphic by Philip Kightlinger)

In the Gator Navy, sailors aboard amphibious ships are away a reported 24 percent of the time. The busiest amphib sailors in this group were from the amphibious assault ship Essex, which reported its crew as being away from home 39 percent of the time.

One amphibious transport dock ship — the Arlington — and three dock landing ships — Carter Hall, Comstock and Fort McHenry — rounded out the units that reported a 30 percent or more PERSTEMPO.

A majority of the Navy’s 13 coastal patrol craft, or PCs, are forward-deployed, based in Bahrain and operating in the Persian Gulf. Two of the three PCs with the highest PERSTEMPO, however, are home-ported in Mayport, Florida, where the Navy supports counter-drug operations in Central and South America.

While supporting these operations over the past three years, sailors aboard the Zephr have been away from home a reported 34 percent of the time, while sailors from the Shamal are gone exactly a quarter of the time.

The ships with the lowest reported PERSTEMPO Navy-wide are the Navy’s mine countermeasures, or MCMs, which reported having sailors away on assignment just 9 percent of the time. The busiest MCM was the Bahrain-based Gladiator, with a reported 16 percent PERSTEMPO.

Data from Littoral Combat Ship crews was excluded by Navy Times because the LCS community is in the midst of switching between multi-crew manning concepts, which Navy Surface Force officials say could skew the data.

LCS crews are changing from the original concept of four crews for every three ships to a pure a “blue and gold” concept similar to what the Navy’s ballistic missile submarines operate under.

On the topic of the submarine community, reported PERSTEMPO numbers, on the surface, may seem low in comparison to the rest of the Navy. Missile boats reported a 16 percent PERSTEMPO, one point higher than their attack sub shipmates.

Missile and fast attack submarine sailors who spent the most time away from home, according to PERSTEMPO data from FY15 - FY17. (Source: Navy Personnel Command / graphic by Philip Kightlinger)

Submarine officials say that it’s tough to compare data to their surface counterparts, however, because subs train and deploy on an 18-month cycle, compared to the 36-month cycles used by U.S.-based surface ships.

Furthermore, officials say submarines don’t generally report PERSTEMPO data into the system used by the Navy because of limited network access. Instead, submarine reports are completed in catch-up mode upon returning to their home ports.

Sailors in aviation units, meanwhile, are among the busiest in the Navy, combining to spend a reported 23 percent of their time away from home.

Helicopter squadron sailors who spent the most time away from home, according to PERSTEMPO data from FY15 - FY17. (Source: Navy Personnel Command / graphic by Philip Kightlinger)

While the Navy’s mine-hunting ships reported some of the lowest PERSTEMPO numbers during the three-year span, the two mine countermeasures Helicopter Squadrons, HM-14 and 15, are, as a group, among the busiest in the Navy, with sailors spending a reported 30 percent of their time away on business.

Almost as busy are the sailors flying the Navy’s carrier onboard delivery missions in the C-2 Greyhound. The squadrons VRC-40 and VRC-30 reported PERSTEMPO numbers of 30 percent and 25 percent, respectively.

All other carrier-based squadrons, regardless of airframe, reported combined PERSTEMPO numbers of about 25 percent, coming in in lock step with their carrier hosts, which report the same numbers.

Squadron sailors who spent the most time away from home, according to PERSTEMPO data from FY15 - FY17. (Source: Navy Personnel Command / graphic by Philip Kightlinger)

Sailors aboard four of the Navy’s 11 active carriers — the Nimitz, Carl Vinson, George H.W. Bush and John C. Stennis — all spent over 30 percent of their time away from home, according to the PERSTEMPO data.

The Roosevelt, which during the documented three-year span completed a round-the-world cruise as part of the Navy’s three-ship carrier swap, had its sailors on the road for a total of 29 percent.