The Federal Aviation Administration last night ordered all domestic operators of commercial Sikorsky S61 helicopters to conduct special inspections of tail rotors and gears as a result of the crash of an S61 in Newark Wednesday night that killed three people.

The mandatory order came 24 hours after the National Transportation Safety Borad had recommended to the FAA that S61s be grounded until a means was found to conduct the inspections.

Simple visual examinations will not locate the fatigue cracks that the board believes caused a large piece of the tail rotor to separate from the rest of the rotor in the Newark accident.

President Carter's S61 helicopter, Marine One, is technically not subject to the FAA rule because it is a military aircraft. However, White House officials said that Marine One received a special inspection yesterday and all was found to be in order.

Robert Whittington, administrator of the FAA's New England region, signed the mandatory order last night. He said in an interview that the directive will meet the reqirements of the safety board recommendation because "we're confident that these tests will detect this set of fractures."

The directive requires a "dye-penetrant" inspection of the blades and tail rotor gear box mounting lugs, followed by regularly scheduled ultrasonic and visual inspections of the rotor blades.

Alan Wayne, a sopkeman for Sikorsky in Stratford, Conn., said that the type of blade that must be inspected is mounted on only 30 helicopters in commercial service here and overseas. However, more that 900 S61s have been sold to military services, all of which have been notified of the FAA directive. Wayne said he did not know how many helicopters in military service had the type of rotor that required inspection.

Pentagon spokesmen said yesterday that they were in touch with Sikorsky and would take appropriate action if their helicopters were affected.

The FAA first learned of the safety board's recommendation not from the board, but from Sikorsky because of a breakdown in communications, The Washington Post has learned.

Between 5 and 6 p.m. Thursday, a safety board official called FAA chief Langhorne Bond's office and said an emergency message would be hand-delivered shortly. Bond was not there and the message was accepted by a secretary, who placed it in the "normal distribution channels," according to an FAA spokesman. That means, in effect, that the officials notification of a potentially fatal aircraft problem stayed in an out-basket overnight.

However, Sikorsky officials learned of the recommendation from reporters who called them for comment. They called the FAA's Whittington, whose New England regional office controls the "airworthiness certificate" for the S61, which is manufactured in Connecticut.

Whittington and other FAA officials started working on the problems Thursday night. The White House was officially advised of the recommendation about 9:30 p.m. by an FAA officially notifies the military of possible safety problem on a military aircraft is if a presidential aircraft is involved the FAA said.

Wayne, the Sikorsky spokesman, said last night that Sikorsky was sending respresentatives to assist commercial operators in testing the rotor blades. Foreign purchasers S61s were being notified last night through international aviation channels, the FAA said.