June 30, 2015

It is a frustration that many Part 135 operators are familiar with: en route to an FAR Part 139 airport, which depends on an automated weather observing system (AWOS) or automated surface observing system (ASOS) without benefit of a human back-up, the station stops transmitting data on the surface temperature. That’s when it’s time to look for landing alternatives because in cases where surface conditions are not reported, regulations may require Part 135 operators to delay, divert or cancel operations to or from that airport.

“When there’s a failure with the automated system, most of the time, it’s the temperature sensor,” said Rich Boll, who chairs the Airspace, ATC and Flight Technologies Working Group of the NBAA Access Committee. “The result is time and money lost.”

It is a problem that continues to grow as more airports rely on automated weather reporting without having a human observer available to make surface reports when the machinery breaks down.

To address that, FAA issued Notice of National Policy 8900.305, along with Information for Operators (InFO) 15006, which indicate that Part 121 and 135 operators may continue using approximately 540 airports where AWOS/ASOS surface conditions are not reported, provided there is an alternative report available called a real-time mesoscale analysis (RTMA).

View the full FAA Info.

View FAA Notice N 8900.305.

The FAA, in conjunction with the National Weather Service (NWS), developed the RTMA system to combine surface conditions data from observation posts surrounding the airport where no automated data is available. Flight crews can use the RTMA result in place of the missing AWOS/ASOS data and continue flight operations as normal.

“RTMA surface-temperature reports are provided by the NWS; therefore, they fall under the category of ‘Weather Reports Prepared by the NWS.’ A certificate holder does not require additional operations specification (OpSec) authorization to use an RTMA,” the FAA said in its notice.

Certificate holders may begin using RTMA surface temperature reports immediately at airports where automated observations are not available, according to the FAA notice. But it also says principal operations inspectors and aviation safety inspector – aircraft dispatchers “must work with certificate holders who conduct Part 121 and/or 135 operations to ensure each certificate holder adopts policies and procedures governing the use of RTMAs, as soon as possible, but no later than 30 days from the publication of this notice,” which was June 1.

“That 30-day window gives operators time to develop policies and procedures describing the use of RTMA as an alternative report,” said Boll.

The use of RTMAs is limited to instances in which AWOS/ASOS surface reports are unavailable, Boll pointed out. RTMA reports are web-based. When using them, Boll said, make sure you clear the cache memory of your smartphone or tablet, or refresh your computer’s web browser, to ensure the RTMA you are using is the most current available.