The Navy said "several" of the 39 aging P-3C Orion aircraft grounded because of structural concerns are based at Kane'ohe Bay.

Citing operational security concerns, officials last week said they couldn't be more specific with the number.

Nearly a quarter of the fleet of 161 of the Cold War-era sub hunters, whose surveillance and reconnaissance capabilities have given them new life in the war on terror, will be out of service for 18 to 24 months as repairs are made, according to the Naval Air Systems Command.

Navy officials also said the grounding could grow.

"It's possible, based on what the data continues to tell us," said John Milliman, a spokes-man for the command based at Patuxent River, Md.

Milliman said the Navy took the proactive step of grounding the 39 P-3s after studies of a test airframe and computer modeling showed there could be "significant" issues with fatigue on the rear portion of the wing between the two propeller engine nacelles.

There was no crash, as was the case with an older Missouri Air National Guard F-15 fighter that went down in early November, leading to an ongoing grounding of all A through D models of the aircraft, including the 18 flown by the Hawai'i Air National Guard.

Three squadrons of P-3Cs are based at Kane'ohe Bay. Each has about 10 aircraft and 450 personnel. One of those squadrons, Patrol Squadron 47, or VP-47, the "Golden Swordsmen," is deployed in support of the war on terrorism, the Navy said.

Naval Air Systems Command issued a bulletin Dec. 17 saying the 39 aircraft were "beyond known structural limits on the lower section" of the wing.

Milliman said the fatigue issue isn't necessarily a function of chronological age of the aircraft but rather of the stress and usage airframes have been put through.

"We know which particular aircraft they are," Milliman said. "We just have to know where those particular aircraft are physically located today."

Ten of the 39 suspect aircraft are deployed, according to the Navy.

According to the Federation of American Scientists, the Navy in 1959 awarded Lockheed a contract to develop a replacement for the aging P-2 Neptune. The P-3V Orion entered the inventory in July 1962, and more than 40 years later it remains the Navy's sole land-based antisubmarine warfare aircraft.

The Orion is scheduled to be replaced by the P-8A Poseidon, a Boeing 737 derivative, beginning about 2011.

P-3 Orions flew out of Barbers Point Naval Air Station, and Patrol Squadron 4, or VP-4, became the first P-3C squadron to be based there in 1984. The aircraft subsequently moved to Kane'ohe Bay.

Following the Sept. 11, 2001, attacks, the P-3, with its long range, was pressed into overland service in Afghanistan, and Patrol Squadron 9 out of Kane'ohe Bay conducted imaging, long-range targeting and firing of Stand-off Land Attack missiles against Taliban and al-Qaida targets.

More recently, Kane'ohe Bay P-3s with long-range electro-optical sensors have patrolled the waters around the Horn of Africa providing information about ship traffic to the command ashore.

Reach William Cole at wcole@honoluluadvertiser.com.

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