Petty Officer Third Class is the fourth enlisted rank in the U.S. Navy and U.S. Coast Guard, just above Seaman and below Petty Officer Second Class, and is the lowest form of non-commissioned officer, equivalent to a Corporal in the U.S. Army and Marines. Petty Officer Third Class shares the same pay grade as Senior Airman in the Air Force, which does not have an NCO rank corresponding with E-4.
Unlike the Seaman and lower ranks, advancement to Petty Officer Third Class is not automatic given time in service, but is also contingent on performance evaluations by their superiors and rate examinations (test of specialty knowledge), except for certain technical ratings which carry automatic advancement to PO3, after successful completion of the rating's "A" school and fulfillment of time in rate requirements. The advancement cycle is currently every 6 months. Only a certain number of billets (job openings for this rank) open up biannually and all Seamen compete. The top scorers are chosen for advancement, but only in sufficient quantities to fill the billets available.
Petty Officers serve a dual role as both technical experts and as leaders. Unlike the sailors below them, there is no such thing as an "undesignated Petty Officer." Every petty officer has both a rate (rank) and rating (job, similar to an MOS or AFSC in other branches). A petty officer's full title is a combination of the two. Thus, a Petty Officer Third Class who has the rating of Fire Control Technician is called a Fire Control Technician Third Class. The term petty officer is, then, only used in abstract, the general sense, when referring to a group of petty officers of different ratings, or when the petty officer's rating is unknown.
Each rating has an official abbreviation, such as FT for Fire Control Technician, STS for Sonar Technician Submarines, or ET for Electronics Technician. When combined with the petty officer level, this gives the short-hand for the petty officer's rank, such as FT3 for Fire Control Technician Third Class. It is common practice to refer to the petty officer by this short hand in all but the most formal correspondence (such as printing and inscription on awards). Often, the petty officer is just referred to by the short hand designation, without using the surname. Thus FT3 Shearer would just be called FT3.
The rating insignia for a Petty Officer Third Class is a white perched eagle, and one specialty mark (designating rank) above a chevron. On more formal uniforms (summer whites and winter working blues or above), the symbol for the petty officer's rating will be placed between the two. On white uniforms, the eagle, rating, and chevron will be navy blue (this has led to the eagle being referred to as the "crow" in common practice, and often the entire rating badge is simply referred to as the crow). On navy blue, the eagle and rating are white, and the chevron is red. Working uniforms and metal rank devices have the rating symbol omitted.
When a sailor is promoted the petty officer third class it is traditional for persons already holding that or a higher enlisted rank to “tack on the crow”. This is done with a gesture ranging from a light tap to a hard punch over the new petty officers sleeve insignia. This, however, has been deemed as "hazing" in the recent past, and as such can subject individuals involved in this practice to disciplinary action. This disciplinary action often includes the individual being demoted. The "tacking on of the crow" has also been known to cause serious injury. It is not just patches that are tacked on but also metal insignia in the chest area that have sharp attachment pins, such as Surface Warfare or Submarine Service. A hard enough punch has been known to cause piercing of the skin by the attachment points. Commanding officers are also known to direct the ship corpsman to perform physical exams for possible abuse and to report all injuries to newly promoted personnel so that punishment for disobeying a direct order (" No 'tacking on of awards' ") cannot be avoided.
The Navy's new High Year Tenure policy has made the good conduct variation for a Petty Officer Third Class all but obsolete. Among enlisted sailors, 12 consecutive years of good conduct (categorized as no convictions by Non-Judicial Punishment or Courts-Martial) entitles the sailor to wear a good conduct variation of their rank insignia: The normally red chevrons under the specialty mark and perched eagle are worn as gold and the eagle is worn as silver. However, the High Year Tenure initiative mandates that a Petty Officer Third Class may only have 8 years of service. If a PO3 fails to make Petty Officer Second Class within those 8 years, the Petty Officer is involuntarily separated for not meeting advancement requirements. This same restriction has recently been placed upon the rank of Petty Officer Second Class, allowing for only 14 years of service before advancement must be attained, and imposing a maximum enlistment of 20 years to a Petty Officer First Class. All of these initiatives, however, may be waived in the event the sailor holds critical training, NEC's or clearances. Today, the few instances when a PO3 has gold chevrons are usually when a sailor has previous military service. The single gold chevron is extremely rare, but can still be found in Navy uniform shops.
All U.S. Coast Guard Petty Officers wear gold chevrons and red service stripes, until the rank of Chief Petty Officers, where both chevrons and service stripes are gold.
In the British Royal Navy and navies of many other Commonwealth counties, the equivalent rank is Able Seaman, although this is considered junior to the nearest equivalent ranks of Corporal or Bombardier in the other military branches.