NTSB: radio gaps preceded Marine One near-miss with airliner at Reagan National

A preliminary report from the National Transportation Safety Board has tied communication failures to an August 4 incident in which Marine One, the presidential helicopter, came close to a departing Envoy Air Embraer E170 near Ronald Reagan Washington National Airport.

The FAA estimated the two aircraft passed within 0.82 nautical miles laterally and about 700 feet vertically, according to the NTSB. The agency said that distance still met the radar-separation standard required for the surrounding Class B airspace.

The report notes that tower staff at DCA and personnel from Marine Helicopter Squadron One, known as HMX-1, had met five days before the incident. Controllers had reported not receiving the required three-minute advance notice ahead of presidential helicopter departures, and HMX-1 described communications as having been intermittent. An alternate notification procedure was put in place after that meeting. An attempt to use it on August 4 did not work.

Recordings reviewed by the FAA showed that Marine One's initial call to the tower was never received. A follow-up transmission came through unreadable. A subsequent FAA review attributed the failures to inadequate line-of-sight radio coverage between the Ellipse, near the White House, and the radio site serving the area.

The FAA has since moved the radios used to control helicopter traffic to the top of the DCA control tower. Follow-up test flights using two HMX-1 helicopters afterward found no further communication problems, the report said.

The NTSB's findings are preliminary. A full investigation into the incident is expected to continue.