Date of Issue:     February 7, l986            Effective Date:     February 7, l986

In Reply Refer To:     W/OTS22             File With:     B-50

Subject:     Policy Guidelines for Monitoring RRWDS Data Signals

Reference(s):    MOA between Department of Transportation (FAA) and NOAA/NWS,
dated February 12, 1982 (Attached)

Purpose. Through the Memorandum of Agreement (MOA), between the Federal Aviation Administration (FAA) and the National Weather Service (NWS) concerning the FAA's Radar Remote Weather Display System (RRWDS), the NWS has the responsibility to monitor RRWDS data generated from NWS radars, usually through the NWS's radar information display (RADID) system. In the event any remoting system affects the operations of the NWS radar or if incorrect information is being transmitted, the NWS has the authority to disconnect the remoting system. This OML outlines quality control procedures, limitations, and corrective actions concerning the RRWDS data signals.

NWS Quality Control Monitoring Responsibility. Quality control of transmitted radar information shall be done as described below. Each office with an RRWDS equipped radar is responsible for quality control of the RRWDS. The standard radar performance checklist (WS form B-74 for WSR57, WS form B-75 for WSR-74S, WS form B-76 for WSR-74C) shall be used for this purpose and maintained with entries to verify when the quality control was accomplished and by whom. This log should be retained for a period of 90 days or 3 years in the event of an aircraft accident. If problems are noted, they shall be described on the checklist, along with what action was taken. Each monitoring office shall include in its Station Duty Manual, and have readily available, the phone numbers of the appropriate maintenance personnel to call for repairs when problems are noted.

Quality Control Procedures. Monitor the RADID to assure the display is consistent with echoes on the NWS radarscope (PPI).  RADID displays should be checked at least once every 8-hour shift.

Tolerances Allowed.

    a.     Geographical location - errors no more than + 10 kilometers within 230 kilometers of the radar site and no more than +5 kilometers between 230 and 450 kilometer range. This can be checked using the map background, isolated echoes, and the D/VIP test pattern.

    b. Intensity levels - for VIP Level 1, the RADID system should display no more than i20 percent echo coverage of D/VIP Level 1, as compared with the radar PPI. For D/VIP Levels 2 through 6, the intensity level displayed on the RADID must be the same as displayed on the PPI. Echo coverage normally should be the same on the RADID as on the PPI. However, because of differing display techniques, a slight blooming in echo coverage on the RADID may be seen. In addition, certain D/VIP levels may occasionally be displayed on the RADID which are barely visible on the radar's PPI. This is normal and no corrective action is necessary.

    c. Checks and appropriate entries logged each shift by the radar operator - check azimuth readout on Isolation Distribution Equipment (IDE) in each quadrant. Azimuth readout must be within +1 degree of the radar's console azimuth indicated reading. IDE elevation indicator readout must be within + l degree of the radar console readout. When the RADID status bar is updated check the time readout to ensure it is correct and set to GMT. The IDE time readout must also be correct and set to GMT.

Corrective Action.

If tolerances are approached, met, or exceeded, reset the RRWDS (if RRWDS is not equipped with an automatic reset) and reexamine the display before taking the following corrective action:

    a.     Deviations approaching or meeting those listed above require notifying the appropriate maintenance personnel for corrective actions. The remoting system can be allowed to continue to operate, with normal monitoring for the above tolerances.

    b.     Normally, deviations that exceed those specified above require notifying the appropriate maintenance personnel immediately and terminating service until the fault is corrected.

    c.     In addition, if the RADID should continuously show data gaps (often indicated by rapid changes in data update sweep position for extended periods), obviously uninterpretable or misleading data, the appropriate maintenance personnel should be notified immediately and the service terminated until the fault is corrected.

    d.     If service is terminated, the reason and time of termination should be noted on the equipment checklist. Also, the respective office's regional radar focal point and area manager should be notified as soon as possible.

    e.     Termination of the data to the RRWDS is accomplished by pulling the B&C connector for the RRWDS line out of the IDE connector panel assembly shown on attachment (line may be connected to any of the following serial output connectors, J2-J6 or J8-J10). However, before disconnecting the line, a complete test pattern should be displayed on the RADID by hitting the test mode key on the radar's D/VIP unit. This procedure is in lieu of contacting external users of RRWDS data. If a test pattern cannot be displayed, then the RRWDS digitizer should be turned off to prevent transmission of old data. A station's electronics technician shall perform the disconnection. However, in his/her absence, the senior duty person in charge will be responsible.

Richard E. Hallgren
Assistant Administrator
   for Weather Services

Attachments

    WHEREAS, the Department of Transportation, Federal Aviation Administration, hereinafter referred to as the F M, and the National Oceanic and Atmospheric Administration, National Weather Service, hereinafter referred to as NWS, acknowledges that the NWS is operating weather radars in the U.S.; and that the FAA requires data from these radars to support the National Airspace System; and that the FAA will buy equipment for installation and operation at certain NWS locations to remote the weather radar data to FAA facilities.

NOW, THEREFORE, the FAA and NWS mutually agree as follows:

ARTICLE I - Description of Project

    The NWS will permit the FAA to install weather radar remoting equipment at designated NWS locations to provide weather radar data from NWS radars for use by FM briefers/controllers and NWS meteorologists at FAA facilities. The FAA will access antenna position and digital video integrator and processor (DVIP) data through appropriate isolation and distribution equipment as specified by the NWS.

Background

    The FAA presently uses an air route surveillance radar (ARSR), weather fixed map unit (WFMIU) and common digitizer (CD) for the detection and processing of weather radar data at long-range radar facilities. The detected weather is digitized at two levels - a low intensity level and a high intensity level. These levels outline weather in general terms and are not calibrated.

There have been major aircraft accidents where thunderstorm activity was involved. The FM initiated experimental projects at a few locations to determine the applicability of remoting data from NWS weather radars to FAA facilities to provide them with more useful weather detection and intensity information.

ARTICLE II - FAA Responsibility

The FAA will provide, install, and maintain the remoting equipment and communication lines to the FM facilities.

The FAA will ensure that weather radar information received from the NWS is accurately relayed by the remoting system to the display equipment by providing means of checking the data.

The F M shall give the NWS the installation schedule for each site proposed and coordinate the installation of all equipment designated for NWS radars with the NWS.

The FAA will give NWS access to dial-in-or connection--to--the remoting system.

The FAA may disconnect any NWS access to the FAA remoting system, after coordination with the affected facility, if the connection affects the FAA's operation or the connection is needed to meet FAA requirements.

ARTICLE III - NOAA/NWS Responsibilities

The NWS will operate its radars in accordance with established NWS procedures. (Network radars are operated continuously when weather is detected; local warning radars are operated on an "as needed" basis only.) NWS maintenance on these radars and the interface/isolation distribution equipment will be performed according to NWS operational priorities. Future discussions on the availability of the radar information and the operational practices of the NWS may be entered into with the purpose of formulating an amendment to this Memorandum of Agreement.

The NWS will assist, where possible, in providing site preparation information to FAA for installation of remoting equipment at NWS facilities.

The NWS will, where possible, provide available space for the FAA's remoting equipment.

NWS may disconnect any remoting system if it affects the operation of the NWS radar or if misleading information might be transmitted after coordination with the affected FAA facilities.

ARTICLE IV -NWS Sites

A list of NWS weather radar sites where the FAA plans to install remoting equipment is attached, including a proposed installation schedule.

ARTICLE V - Amendment

    Any change to this agreement shall be formalized by an appropriate written amendment to this agreement.

AGREED:

National Oceanic and Atmospheric
Administration/National Weather Service

BY: ___________________________

TITLE: Director, National Weather Service

DATE: ________________________________________

Federal Aviation Administration

BY: ___________________________________________

TITLE: Director, Airway Facilities Service

DATE: _________________________________________