The Philippine government is arming some planes and using others to ferry troops to battle Moslem rebels in the southern Philippines, although the aircraft were bought with U.S. economic aid intended specifically for peaceful purposes, according to both American and Philippine officials.

R.A. Duchesne, head of excess property sales for the U.S. Agency for International Development in Manila, said the agency already has asked the Philippine air force to remove the machine guns mounted on some of the 30 spotter planes.

These single-engine aircraft, with a total value of $2.9 million, were acquired in June 1972 from Vietnam surplus virtually without cost to the Philippines--for use in development projects, Duchesne said.

Three Lockheed Hercules cargo planes have flown troops to Zamboanga, headquarters of the southwest Philippines command and a center of the fight against Moslems in Mindanao and the Sulu Islands, according to Philippine military officials.

Philippine officials said the three craft were among four cargo planes acquired for development purposes under an $8 million loan from the U.S. Export-Import Bank. The fourth aircraft is still to be delivered.

"They were acquired for development uses," Col. Luis Mirasel Jr. of the office of the executive secretary to Philippine president Ferdinand E. Marcos, to which the planes were assigned. "It is a matter of semantics how you define development. Peace and order flights are part of our development program.

Maximum Utilization

"We also try for maximum utilization of the planes. The cargo planes carry 24 tons of cargo, and if they are available for carrying soldiers, then we have used them. We certainly don't use them to bomb or to carry ammunition," Mirasel contiued.

Mirasel said the smaller single-engine planes had been armed after the fighting in the south intensified. He said they were being fired on while delivering mail, and that he believed now that most of the weapons have been removed.