Page 12 Par 16 systems in detecting turbulence, and the feasibility of using them
• Consider graphical onboard turbulence display systems
• Work with FAA, NASA, and other Government organizations, and with equipment manufacturers to develop industry standard weather formats for flight deck display systems (carry-on and new production panel mounted)
ORIGINAL SIGNED BY JOHN M. ALLEN (for)
James J. Ballough Director, Flight Standards Service
Appendix 1 APPENDIX 1. COMMERCIAL AVIATION SAFETY TEAM (CAST)
TURBULENCE TEMPLATE
The CAST Turbulence Template comprises two parts:
STANDARD TERMINOLOGY FOR TURBULENCE, endorsed by the Commercial Aviation Safety Team, from the Aeronautical Information Manual (AIM)
PROCEDURES KNOWN TO BE EFFECTIVE AGAINST TURBULENCE, procedures identified by the Commercial Aviation Safety Team and suggested as standard operating procedures for voluntary implementation by U.S. air carriers
STANDARD TERMINOLOGY FOR TURBULENCE
The following terminology is endorsed by the Commercial Aviation Safety Team, from the Aeronautical Information Manual (http://www.faa.gov/atpubs/)
DURATION OF TURBULENCE
Occasional. Less than 1/3 of the time.
Intermittent. 1/3 to 2/3 of the time.
Continuous. More than 2/3 of the time.
NOTE: Duration may be based on time between two locations or over a single location. All locations should be readily identifiable.
TURBULENCE INTENSITY
Light Chop. Slight, rapid, and somewhat rhythmic bumpiness without appreciable changes in altitude or attitude.
Light Turbulence. Slight, erratic changes in altitude and/or attitude. Occupants may feel a slight strain against seatbelts. Unsecured objects may be displaced slightly. Food service may be conducted and little to no difficulty is encountered in walking.
Moderate Chop. Rapid bumps or jolts without appreciable changes in aircraft altitude or attitude.
Moderate Turbulence. Changes in altitude and/or attitude occur but the aircraft remains in positive control at all times. It usually causes variations in indicated airspeed.
Appendix 1 APPENDIX 1. COMMERCIAL AVIATION SAFETY TEAM (CAST) TURBULENCE TEMPLATE (Continued)
Occupants feel definite strain against seatbelts. Unsecured objects are dislodged. Food service and walking are difficult.
Severe. Large, abrupt changes in altitude and/or attitude. Usually causes large variations in indicated airspeed. Aircraft may be momentarily out of control. Occupants are forced violently against seatbelts. Unsecured objects are tossed about. Food service and walking are impossible.
Extreme. Aircraft is violently tossed about and is practically impossible to control. May cause structural damage.
TURBULENCE TYPES
Thunderstorm Turbulence. Turbulence associated within and in the vicinity of thunderstorms or cumulonimbus clouds. A cumulonimbus cloud with hanging protuberances is usually indicative of severe turbulence.
Clear Air Turbulence. High level turbulence (above 15000’) not normally associated with cumuliform cloudiness. Typically windshear turbulence even when in cirrus clouds.
Mountain Wave Turbulence. Turbulence as a result of air being blown over a mountain range or a sharp bluff causing a series of updrafts and downdrafts.
PROCEDURES KNOWN TO BE EFFECTIVE AGAINST
TURBULENCE
The following procedures have been identified by the CAST and are suggested as standard operating procedures for voluntary implementation by U.S. air carriers
MAXIMIZE THE INFORMATION ABOUT YOUR FLIGHT CONDITIONS
Inform ATC of turbulence at check in with new controller.
Inform ATC when unforecasted turbulence is encountered en route.
Inform company via ACARS or dispatch frequency so that following flights will be aware of the flight conditions or be planned on another route.
Inform/query other aircraft operating in the area on a common frequency.
Query ATC about “the rides” when you check in with a new controller/sector.
Appendix 1 APPENDIX 1. COMMERCIAL AVIATION SAFETY TEAM (CAST) TURBULENCE TEMPLATE (Continued)
WHEN INFORMED OF TURBULENT FLIGHT CONDITIONS:
Prior to departure, seek alternate routing to avoid the affected areas or delay departure until conditions improve.
Change en route altitudes or routes to avoid the turbulence.
Slow to the manufacturer’s recommended turbulence penetration speed.
Prior to descent, seek alternate routing to avoid the affected areas or, if severity dictates, hold or divert to alternate.
AVOID any convective activity (CBs) en route by at least 20 nautical miles.
GENERAL TURBULENCE PROCEDURES
If flight into forecast turbulence is unavoidable, timely notification to the cabin crew is crucial to their safety.
If turbulence is expected before the flight departs, the preflight briefing to the lead flight attendant must include turbulence considerations. The briefing can be the same as an inflight briefing for expected turbulence including:
• Actions the captain wants the cabin crew to undertake any time turbulence is expected
• Intensity of turbulence expected
• Methodology for communicating to the cabin the onset or worsening of turbulence,
e.g., cabin interphone or PA
• Phraseology for the cabin crew to communicate the severity of turbulence
• Expected duration of the turbulence and how an “all-clear” will be communicated
Utilize a positive signal of when cabin crew may commence their duties after takeoff and when they should be seated and secured prior to landing.
Passengers will be informed of routine turbulence via the PA system. Do not rely on the seatbelt sign alone.
Cabin crew will be informed of routine turbulence via the interphone.
If at any time the cabin crew experiences uncomfortable turbulence without notice from the flight crew, they must immediately take their seats and inform the flight crew.
All service items must be properly stowed and secured when not in use.
Appendix 1 APPENDIX 1. COMMERCIAL AVIATION SAFETY TEAM (CAST) TURBULENCE TEMPLATE (Continued)
TURBULENCE ONSET CATEGORIES
Expected Turbulence. Advance notice exists for the Captain to brief the cabin crew either prior to the flight or in-flight via the interphone.
Little Warning. Sufficient warning exists to seat the passengers and for the cabin crew to perform their duties.
Imminent Turbulence or Turbulence Occurring. Sudden, unexpected or imminent turbulence requiring immediate action to protect cabin crew and passengers.
INJURY AVOIDANCE ACTIONS
Expected Turbulence
Captain can thoroughly brief the cabin crew on the expected turbulence level and its duration.
Clearly articulate expectations from the cabin crew and request confirmation of completed actions.
Instruct the cabin crew to immediately and plainly report any deviations from the expected turbulence level.
Develop a method to inform the cabin crew of the completion of the turbulence event.
Little Warning
Captain turns on seatbelt sign and makes a public address announcement, ”Flight Attendants stow your service items and take your seats. Passengers please remain seated until this area of turbulence has passed and I have cleared you to move about the cabin.”
Cabin crew stows all applicable service items, performs cabin compliance check, and secures themselves in their jump seats.
Lead flight attendant informs captain of the completion of these items.
When conditions improve, captain uses the public address system to advise the cabin crew that they may resume their duties and whether or not the passengers may move about the cabin.
Appendix 1 Page 5 (and 6) APPENDIX 1. COMMERCIAL AVIATION SAFETY TEAM (CAST) TURBULENCE TEMPLATE (Continued)
Imminent Turbulence or Turbulence Occurring
Captain turns on seatbelt sign and makes a public address announcement, “flight attendants and passengers be seated immediately. Passengers please remain seated until this area of turbulence has passed and I have cleared you to move about the cabin.”
Cabin crew take first available seat and secure themselves.
No compliance checks are performed and items are secured only if they present no delay in securing a person in a seat.
When conditions improve, captain makes public address announcement advising the cabin crew that they may resume their duties and whether or not the passengers may move about the cabin.
Appendix 2 Page 1 (and 2) APPENDIX 2. USAF PRACTICES TO AVOID THUNDERSTORMS AND
ATTENDANT TURBULENCE
The practices shown below are excerpted from United States Air Force Flight Publications for pilots of the Air Mobility Command (AMC).
Many of the airplanes operated by AMC compare closely to the transport category airplanes operated by U.S. air carriers under 14 CFR part 121 in respect to size, weight, and other characteristics. Practices effective in AMC operations are often effective in commercial (air carrier) operations, and vice versa.
The following practices have been developed by the Air Force for AMC pilots as measures to prevent thunderstorm penetrations and to mitigate effects of proximate thunderstorms, especially loss of control and turbulence that might cause injury.
These practices are reprinted here for reference by managers and trainers of pilots operating transport category airplanes in commercial aviation, especially those carrying passengers and flight attendants under 14 CFR part 121. These practices are comprised of clear and objective criteria to facilitate recognition of cues associated with severe convective activity and guidance to improve flight crew decision-making.
During flight, use any means available to avoid thunderstorms by at least:
20 nautical miles at or above flight level (FL) 230 10 nautical miles below FL 230
In order to minimize exposure to thunderstorm hazards when approaching or departing an airport in an area where thunderstorms are occurring or are forecast;
Attempt to maintain visual meteorological conditions (VMC).
Maintain at least 5 nautical miles separation from heavy rain showers.
Avoid areas of high lightning potential, i.e., clouds within ± 5,000 feet of the freezing level.
NOTE: Approaches or departures may be accomplished when thunderstorms are within 10 nautical miles. The thunderstorms must not be producing hazardous conditions (such as hail, lightning, strong winds, gust fronts, heavy rain wind shear, or microburst) at the airport, and must not be forecast or observed to be moving in the direction of the route of flight (to include the planned missed approach corridor, if applicable).
Appendix 3 APPENDIX 3. DETECTION: NEW AND EMERGING TECHNOLOGIES,
PRODUCTS AND SERVICES TO DETECT TURBULENCE
(1) Turbulence Prediction and Warning systems (TPAWS). Currently NASA and FAA are leading a multi-disciplined Government/industry team directed at developing the scientific basis, algorithms and performance requirements for the detection of convective and non-convective related turbulence (http://tpaws.larc.nasa.gov). TPAWS efforts are focused on two areas:
• Enhancements to existing aircraft radar systems – this includes new signal processing algorithms and alerting capabilities for predictive wind shear radars.
The goal is to improve convective turbulence detection in the 25-40 mile range and deliver meaningful alerts to the crew
• New onboard turbulence detection/mitigation technologies – this includes research into look-ahead detection systems such as Light Detection and Ranging (LIDAR), and automated flight control systems to mitigate turbulence initiated cabin accelerations
NOTE: NASA and FAA are jointly conducting workshops for developing performance and certification criteria for development of turbulence sensors.
(2) MDCRS (Meteorological Data Collection and Reporting System) – The goal of the MDCRS program is to significantly increase the availability of automated aircraft weather reports. MDCRS is the result of collaboration between the FAA, NWS, and six participating U.S. air carriers. Currently, MDCRS provides over 100,000 daily-automated aircraft wind and temperature reports to the FAA and NWS.
(3) EDR (Eddy Dissipation Rate) – As part of the FAA Turbulence Product Development Team (PDT), the National Center for Atmospheric Research (NCAR) has developed the technology to use existing aircraft performance systems to derive an automated turbulence measurement (EDR). In collaboration with the FAA and NCAR, one airline has installed EDR software on over 100 aircraft. Since 2001, these 100 aircraft have been providing automatic downlink of peak and average turbulence readings at one-minute intervals. This information is currently being used for research and as input into automated turbulence forecasts (see GTG below). Future plans include installation of EDR software on as many as 1200 commercial aircraft, converting the metric into aircraft specific ride reports, and distribution of this information nationally.
Appendix 3 APPENDIX 3. DETECTION: NEW AND EMERGING TECHNOLOGIES, PRODUCTS AND SERVICES TO DETECT TURBULENCE (Continued)
(4) GTG (Graphic Turbulence Guidance) – MDCRS and EDR aircraft reports are being used to update forecast models (RUC and GFS), as well as being used to develop automated turbulence forecast products, such as the newly developed Graphic Turbulence Guidance (GTG). The GTG has been under development for several years by NCAR. The GTG provides a graphic depiction of clear air turbulence potential for altitudes above FL200, over the contiguous U.S. at 3-hour intervals out to 12 hours. This product is available on the FAA funded Aviation Digital Data Service (ADDS) web site hosted by the NWS Aviation Weather Center (http://adds.aviationweather.noaa.gov/).
(5) OCND (Ocean Convective Nowcast Demonstration) – Convection over oceanic areas has been and continues to be a major source of air carrier turbulence encounters and related injuries. This issue is being addressed by the FAA Oceanic Weather Product Development Team (OWPDT). As OWPDT members, NCAR and the Naval Research Lab (NRL) have developed an experimental graphic oceanic convective product, the Oceanic Convective Nowcast Demonstration (OCND). Using real time oceanic satellite data and associated analysis algorithms, convective cloud top graphics are generated at 30-minute intervals. During initial development the OCND graphic was available to dispatchers and oceanic controllers via Internet, and also uplinked to aircraft in flight over the central and south Pacific. Currently, experimental OCND products are available for the Pacific and Caribbean, with plans to expand coverage to include the North Atlantic in the near future. These graphics are available on an NCAR web site: (http://www.rap.ucar.edu/projects/owpdt).
(6) CIWS (Center Integrated Weather System) - CIWS is an FAA sponsored program to develop an improved aviation convective weather graphic. CIWS uses radar inputs from NWS Next Generation Weather Radar (NEXRAD), FAA Terminal Doppler Weather Radar (TDWR), and FAA Airport Surveillance Radar (ASR) radars, to generate automated, high update information on storm locations and echo tops along with 2-hour high resolution animated growth and decay forecasts of storms. Coverage is limited to the Great Lakes and northeast corridor (Chicago to the East Coast). Airline systems operations centers had access to the products via servers on the Internet and CDM-Net as well as via dedicated displays.
(7) ADDS (Aviation Digital Data Service) – ADDS is an operational FAA/NWS web site dedicated to providing graphic aviation products in real time. Developed by NOAA’s Forecast Systems Lab (FSL) under FAA sponsorship, the site includes leading edge products such as GTG and the NCWF, as well as traditional aviation products such as SIGMETS and convective SIGMETS in graphic format. Many of the available products provide critical information on turbulence (pilot reports, forecasts, convective products, SIGMETS, etc.) in graphic form. (http://adds.aviationweather.noaa.gov/).
APPENDIX 3. DETECTION: NEW AND EMERGING TECHNOLOGIES,
Appendix 3 Page 3 (and 4) PRODUCTS AND SERVICES TO DETECT TURBULENCE (Continued)
(8) NCWF (National Convective Weather Forecast) - The NCWF, designed and implemented by NCAR, provides current convective hazards and 1-hour extrapolation forecasts of thunderstorm hazard locations. The hazard field and forecasts update every 5 minutes. The NCWF development is sponsored by the FAA AWR program as part of the Convective Weather PDT. The Convective Weather PDT consists of MIT Lincoln Laboratories, National Severe Storms Laboratory (NSSL), National Weather Service's Aviation Weather Center (AWC), and NCAR. This graphic can be accessed via the ADDS web site under “Convection” (http://adds.aviationweather.noaa.gov/convection/java).