U.S. Department

of Transportation


Federal Aviation



Air Traffic


A Communication from the  Director of Air Traffic                        



       Issue # 2001 - 3

      March 2001                                                                                             

     *** SPECIAL EDITION ***                                                             Return to Air Traffic Publications Home Page

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In this Issue:




CFIT and Stabilized Approach Procedures






/*TEFR/  Do you hear that low, rumbling sound? You know what it is - it is the far off growl of thunder, and chances are, it is headed your way. Just as sure as the daffodils will bloom in the spring, the thunderheads will blossom, too, and that is bad news for us. Why? Because those of us in the safety business know that thunderstorms mean danger. Whether it is called a microburst, low level wind shear, turbulence, hail, a downdraft, or the worst of all scenarios, a funnel cloud, we know the extra danger thunderstorms can produce. Year in and year out we are faced with the same phenomena. You probably know exactly where the storms will be when spring comes.


If you do not know where the convective activity will be, it is time to find out, before the boomers arrive. Thunderstorms are predictable only in the sense that we know when conditions are right. Forecasters can measure and observe the atmospheric conditions and say with assurance only that storms might form. We play a vital role in the confirmation of that forecast, because we form a direct link to thousands of informal observers in the sky: pilots. It is this source of data that we should take advantage of as often as possible. Through the eyes of the pilot, we can learn about the actual conditions aloft, whether a line is forming or dissipating, whether lightning is cloud-to-cloud or cloud-to-ground, whether the tops are building, static, or decreasing. All of these elements contribute to our knowledge of the real situation, and more knowledge for us increases the level of safety for all.


Wherever you work, convective activity has its own personality. Florida, for example, is prone to "pop-up" type thunderstorms - storms that build quickly and produce localized, violent weather. In the Southwest, storms form in advance of a front or dry line, creating a long, thin line of dangerous weather. Both of these situations call for knowledge, vigilance, and experience on our part, and in each case forecasters can say when conditions are right, but the confirmation, the where and how big, the how fast, mean, ugly, and nasty might come from you, and you only.


Thunderstorms are dangerous, true, but we know how to deal with that danger. We use weather radar. We use pilot weather reports (PIREP). FAAO 7110.65, Air Traffic Control, paragraph 2-6-3, PIREP Information, says: 


Significant PIREP information includes reports of strong frontal activity, squall lines, thunderstorms, light to severe icing, wind shear, and turbulence (including clear air turbulence) of moderate or greater intensity, volcanic eruptions and volcanic ash clouds, and other conditions pertinent to flight safety. Solicit PIREP's when requested or when one of the following conditions exists or is forecast for your area of jurisdiction: ceilings at or below 5,000 feet, visibility (surface or aloft) at or less than 5 miles, thunderstorms and related phenomena, turbulence of moderate degree or greater, icing of light degree or greater, wind shear, volcanic ash clouds, and for terminal facilities, when braking action advisories are in effect.


Once we receive the PIREP's, relay the information to concerned aircraft in a timely manner.


We also use convective significant meteorological information (SIGMET), forecasts, vectors, deviations and severe weather reroutes. We use communication and coordination. But most of all, we use our judgment and common sense. As well-trained professionals, we know where to obtain a weather brief when we come on duty. We know how to broadcast hazardous inflight weather advisory service (HIWAS) advisories for airmen's meteorological information, SIGMET, and center weather advisory alerts.


FAAO 7110.65, Air Traffic Control, paragraph 2-6-2, HIWAS, says:


Controllers shall advise pilots of hazardous weather that may impact operations within 150 NM of their sector or area of jurisdiction. Hazardous weather information contained in HIWAS broadcasts includes Airmen's Meteorological Information (AIRMET), SIGMET, Convective SIGMET (WST), Urgent Pilot Weather Reports (UUA), and Center Weather Advisories (CWA). Facilities shall review alert messages to determine the geographical area and operational impact for hazardous weather information broadcasts. The broadcast is not required if aircraft on your frequency(s) will not be affected.


Controllers within commissioned HIWAS areas shall broadcast a HIWAS alert on all frequencies, except emergency frequency, upon receipt of hazardous weather information. Controllers are required to disseminate data based on the operational impact on the sector or area of control jurisdiction.


Controllers outside of commissioned HIWAS areas shall advise pilots of the availability of hazardous weather advisories. Pilots requesting additional information should be directed to contact the nearest Flight Watch or Flight Service.  Controllers shall also apply the same procedure when HIWAS outlets, or outlets with radio coverage extending into your sector or airspace under your jurisdiction, are out of service.


Remember that terminal facilities have the option to limit hazardous weather information broadcasts as follows: Tower cab and approach control facilities may opt to broadcast hazardous weather information alerts only when any part of the area described is within 50 NM of the airspace under their jurisdiction.


We also know how to monitor Low Level Wind Shear Alert System and Terminal Doppler Weather Radar (TDWR) and the phraseology for passing warnings to pilots.


FAAO 7110.65, Air Traffic Control, paragraph 3-1-8, Low Level Wind Shear Advisories, states that when low level wind shear is reported by pilots or detected on any of the Doppler or Low Level Wind Shear Alert Systems (LLWAS), controllers shall issue the alert to all arriving and departing aircraft until the alert is broadcast on the Automatic Terminal Information Service (ATIS) and pilots indicate they have received the appropriate ATIS code. A statement shall be    included on the ATIS for 20 minutes       following the last report or indication of wind shear. 


LLWAS "Network Expansion" (LLWAS III) and LLWAS systems that are integrated with TDWR provide the capability of displaying microburst alerts, wind shear alerts, and wind information oriented to the threshold or departure end of a runway. TDWR is designed to detect wind shear and microburst activity. The associated ribbon display allows the controller to read the displayed alert without any need for interpretation.


Brush up on your procedures now, while it's quiet.  Listen. Do you hear the thunderstorms coming?  (ATP-100)




Controlled Flight into Terrain (CFIT) and Stabilized Approach Procedures.

/*TER/  CFIT is one of the greatest causes of accidents involving large aircraft. In an effort to reduce CFIT, many flight instructors are now emphasizing stabilized approach procedures when nonprecision approaches are being executed.  Stabilized approach procedures are characterized by a constant angle - a constant rate of descent approach profile ending near the touchdown point where the landing maneuver begins. Complying with FAAO 7110.65, Air Traffic Control, and good operating practices facilitates these procedures.  When low cloud ceilings exist, vector an aircraft so that it is established on the final approach course at least two miles outside of the approach gate at an altitude not above the glide slope/glidepath.  Additionally, for a nonprecision approach, place an aircraft at an altitude that will allow descent in accordance with published procedures.  These procedures facilitate stabilized approaches.  Slam dunks, dive and drive, and other procedures that require abnormally high descent rates inhibit a pilot's ability to descend toward the runway in a stabilized constant descent configuration.  These procedures can significantly increase pilot workload at a critical phase of flight.  (ATP-100)



                                   Questions/comments about content should be addressed to ATP-100