The Navy has grounded 39 of its aging P-3C Orion surveillance and anti-submarine aircraft over concerns about possible structural failure in the wings.

It was unclear if the grounding affects Hawai'i-based planes. Three squadrons of P-3Cs are based at Kane'ohe Bay. Each has about 10 aircraft and 450 personnel.

Naval Air Systems Command, which issued a bulletin yesterday announcing the grounding, could not be reached for comment. The command in the bulletin said the 39 aircraft were "beyond known structural limits on the lower section" of the wing.

An inspection of all P-3C aircraft is ongoing, and the service said it's possible more aircraft may be grounded.

The P-3C concern follows the grounding of another aging aircraft, the Air Force's F-15 Eagle fighter, and worries over its structural integrity.

Hawai'i's F-15 Eagle fighters have not been able to fly since a Missouri Air National Guard jet crashed on Nov. 2.

The Air Force required three inspections involving F-15 A through D model aircraft. The grounding affects more than 450 of the aircraft worldwide.

The Hawai'i Air National Guard has 18 of the twin-tail fighters, which serve in a homeland defense role for the state.

In the interim, Hawai'i has been covered by F-16 Fighting Falcons from the Minnesota Air National Guard.

The prolonged grounding is affecting the training of F-15 pilots who are expected to fly between nine and a dozen times each month.

AVERAGE AGE: 28 YEARS

Ten of the Navy's P-3C propeller planes are currently deployed overseas, and Navy spokesman Cmdr. Jeff Davis said they will return to the U.S. for repairs and it has not yet been determined how or if they will be replaced.

"We are acting early, based upon engineering analysis and fleet inspections, to ground these aircraft before a problem arises," Davis said.

The Navy has a total of 161 of the P-3C Orions, which are 28 years old on average.

It will take 18 to 24 months to repair each of the planes, for a total of about three years to complete the process. Those that cannot be repaired will be removed from service.

The Orions are some of the oldest aircraft the Navy has, and they are to be replaced in coming years by the new P-8A Poseidon, a Boeing 737 derivative. The Poseidons are expected to be introduced in the Navy fleet around 2011.

39 CHOSEN BY ANALYSIS

Davis said it is not clear yet whether the rest of the Orions will also have to eventually be taken out of service for repairs.

The 39 were chosen based on their age, number of hours flown and other computer analysis that showed they had exceeded the amount of fatigue on the wings that the Navy considered a concern.

The Navy is looking at whether to base the new P-8A aircraft at Kane'ohe Bay or Hickam Air Force Base, or simply to maintain a detachment presence in the Islands, but the P-8A's arrival will spell the end for the Navy's use of the Orion.

The Navy previously said it planned to replace the P-3C four-engine aircraft with the P-8A at existing continental patrol home bases "while maintaining a maritime patrol presence in Hawai'i."

A typical six-month deployment for the four-engine planes takes one of the three Hawai'i squadrons to locations such as Diego Garcia in the Indian Ocean, the Middle East and countries including Bahrain and Japan.

The Associated Press and Advertiser military writer William Cole contributed to this report. Reach Cole at wcole@honoluluadvertiser.com or 525-5459.

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