June 2017 Issue

NTSB Takes On Pireps

A special investigation report says submission and dissemination issues reduce their effectiveness:

Iced Up Jet Windshield

The Learjet Model 35A pictured here encountered severe inflight icing conditions on approach to Anchorage, Alaska. The conditions exceeded the airplane’s windscreen anti-ice system capabilities and it iced over. The flight crew lost all forward visibility. While landing, the airplane veered off the runway and came to rest in a snow bank.

Pilots love to disrespect the FAA’s Notice to Airmen (Notam) system. It’s been the subject of federal legislation in recent years, and now the NTSB has published a Special Investigative Report (SIR-17/02), “Improving Pilot Weather Report Submission and Dissemination to Benefit Safety in the National Airspace System,” a 68-page collection of everything that’s wrong with the system. The Board undertook the investigation after investigating 16 accidents and incidents that exposed Pirep-related areas of concern between March 2012 and December 2015.

The report highlights what the Board considers problems with the current Pireps collection and dissemination system. According to the Board, “For Pireps to be most effective, they must be numerous, accurate, and made available quickly in the [National Airspace System (NAS)]. Apart from its investigations into the Pirep-related accidents and incidents described above, has Board discussed the service with various user groups, identifying “delays, errors and data losses” in the system.

“These types of issues—because they affect the accuracy and timeliness of the weather information upon which flight safety decisions are made—can play a role in the complex interaction of events and conditions that lead to aircraft accidents and incidents,” the report states.

The NTSB said it determined Pirep-dissemination issues contributed to only two incidents of the 16 events it investigated. In both cases, “flight crews were not provided” submitted Pireps about hazardous weather before they flew into it. While the information may not have prevented the incident, its delivery would have “increased the weather situational awareness of the incident flight crews, which could have helped them avoid the weather hazards and prevent the aircraft-damaging events.”

In the other investigations, the Board said it discovered similar concerns. “The prevalence of these issues across numerous investigations, as well as the similarities” between them, plus concerns raised by user groups, “suggests that such problems are widespread.” Correcting them, the Board added, “can help reduce the occurrence of hazardous weather encounters in the NAS.”

Reasons Pilots Give For Not Filing Pireps

Approach Lights

1. Lack of Awareness of Importance of All Pireps

Surveys cited by the NTSB indicate that pilots “believed that the primary purpose of PIREPs was for reporting bad weather” only and that the Pirep system wasn’t designed for good weather, or to confirm conditions that were forecast.

2. Pirep Format/Weather Assessment Skills

Those same surveys reveal pilots are not confident in their ability to assess the weather they encounter accurately. “[I]mproved weather recognition skills and improved familiarity with the PIREP format would likely lead to an increase in the volume of reported weather.”

3. Cockpit Workload

Whether submitted by voice or automation, pilots in high-workload environments “may find it difficult to file a Pirep.” Pilots also are reluctant to interrupt “an already congested” ATC frequency with one.

4. Fear of Enforcement Action

Pilots are afraid issuing a Pirep may result in an enforcement action against them when reporting “an inadvertent encounter with adverse conditions for which either the pilot is not rated to fly (such as an encounter with IMC without having an instrument rating) or the aircraft is not certificated to operate (such as an encounter with airframe icing in an aircraft that is not equipped for such operations).”

5. Past Experience with Reports Not Disseminated

After they land, pilots routinely look to find Pireps they filed to ensure their message got through. When they don’t find the Pirep they submitted, they’re reluctant to submit new ones.


The Board’s report included 16 conclusions reached during its study. Some highlights:

- “Pilots who learn how to file pilot weather reports (Pireps) during initial flight training and who practice the skill during recurrent training and flight reviews are more likely to routinely submit Pireps.”

- “A single source of standardized guidance for pilot weather report (Pirep) reporting and coding, as well as weather assessment and classification criteria for low-level windshear, turbulence, and fair weather, can help reduce omissions and subjectivity errors in Pireps.”

- “Unrestricted sharing of pilot weather report information, without exception to operator or weather service provider, should be encouraged as a standard operating procedure for all operators to improve flight safety and runway surface safety in the National Airspace System.”


The Board also made numerous recommendations to the FAA, the National Weather Service (NWS) and others. For example, the Board urged both the FAA and the NWS to “revise and harmonize” Pirep guidance in the Aeronautical Information Manual (AIM) and Advisory Circular (AC) 00-45H, Aviation Weather Services, especially relating to reporting low-level windshear, turbulence and fair weather.

Standardized mountain-wave activity reporting, for example, should include an airspeed range, and classify the difference between a smooth and turbulent mountain wave encounter. And a recommendation to streamline controller tools used to publish Pireps once they’re received highlights the workload requirements of the existing system.

One of the Board’s most interesting recommendations, however, is that the FAA “provide a reliable means of electronically accepting pilot weather reports directly from all users” and that it “ensure that the system has the capacity to accept and make available all such reports to the [NAS].” The Board also recommended that Pireps be archived for at least a year, in support of various research purposes.