Aircraft Operations

This is the unofficial, WWW version of the VORTEX-95 Operations Plan. It may differ from the published operations plan which is available by 15 March from the National Severe Storms Laboratory.

Objectives

Two aircraft have been committed to VORTEX in 1995; the NOAA P-3 for 115 flight hours and the NCAR Electra for 100 hours. The P-3 is also scheduled for 45 flight hours to meet ARM objectives. These aircraft will be used to document the entire life cycle of tornadic storms. To do this, the aircraft will be deployed to the area where initiation is expected to occur, arriving there at the time of the development of the first deep cumulus towers.

The primary mission of the two aircraft is to gather pseudo-dual Doppler data sets focusing on the evolution of the low-level mesocyclone region of the tornadic storm which the ground intercept teams are investigating. The emphasis is to monitor the flow structure near the ground. Consequently, flight patterns are normally designed to be flown in the lower levels, as close as safely possible to the mesocyclone region to enhance near-ground data quality and resolution.

Operational Constraints

The Aircraft Operations Center (AOC) of NOAA and the NCAR Research Aviation Facility (RAF) have developed several rules regarding aircraft flight missions to insure safe operations yet allow maximum flexibility to adjust to changing weather and scientific objectives. These constraints are summarized in the following table.


              --- AIRCRAFT OPERATIONAL CONSTRAINTS ---

    CONSTRAINT                             LIMIT
    Anticipated next-day takeoff time      Specified at least 24h in advance
    Crew duty day                          16 hours
    Minimum crew rest between duty days    15 hours
    Maximum consecutive mission days       6 days
    Minimum pre-flight preparation time    3 hours
.

The anticipated next-day takeoff time specifies the start of the crew duty day. The mission must be completed within 16 hours of this time including any delays in takeoff. A "hard-down" day must be given after the sixth consecutive mission day. A mission day is defined as an alert day whether or not the aircraft actually flies a mission. The scientific personnel will also adhere to the crew duty day and crew rest operational constraints.

Daily Flight Operations

Aircraft operational constraints dictate that notification of anticipated next day takeoff must be specified 24 hours in advance. Normally, the aircraft personnel will begin their crew duty day at 12:00 CDT with a scheduled takeoff (TO) time of 14:00 CDT. One to three-hour delays may occur if the weather does not cooperate. TO times after 17:00 CDT will be avoided if at all possible.

TO -1 day

(11:00 CDT) VORTEX Operations Coordinator will notify AOC and NCAR Operations Officer of TO time for operations the next day, or will declare the next day a hard down day for aircraft operations.

The remainder of this section is valid for VORTEX GO days.

TO -4 1/2 h

(9:30 CDT) Key aircraft personnel are briefed by VORTEX Field Coordinator.

TO -3 h

(11:00 CDT) Final GO or NO-GO decision, or delay the TO.

TO -1 1/2 h

Key scientific personnel receive a final briefing and leave for aircraft.

TO -1 h

P-3 chief scientist briefs P-3 pilot, co-pilot, navigator, and flight director, and the Electra chief scientist briefs NCAR pilot, co-pilot, and navigator on expected weather, initial point (IP), and type of flight plans. Immediately after TO, the chief scientists should make contact with the Field Coordinator to obtain latest coordinates and update on cloud development. Close coordination between scientist on each aircraft will be performed on VORTEX radio channel #3. Flights will be daylight flights. Expected landing should not be later than 2130 CDT. Maximum flight time on all VORTEX flights will be 7.5 hours.

Aircraft Flight Patterns and Techniques

Convective Patterns

These are the basic flight patterns to meet the primary objectives documenting the evolution of the low-level kinematic structure of the mesocyclone region of a tornadic supercell.

Pattern: Isolated Supercell

Goal Document the structure and evolution of isolated supercell as directed by ground intercept Field Coordinator.

Sequence Fly racetrack patterns normally on inflow side of storm as close as possible (12-20 km to mesocyclone and as low as possible for safe operations. This may be executed with one or two aircraft. See multiple aircraft flight strategies.

Height 5000 ft or below

Time required 5 minutes to complete one pass

References Accompanying diagram

Pattern: Supercell Imbedded in Linear Formation

Goal Document the structure and evolution of one particular convective storm in a line of storms as directed by ground intercept Field Coordinator.

Sequence Fly racetrack patterns as close as possible to mesocyclone (12-20 km) and as low as possible for safe operations. This pattern may be executed with one or two aircraft. See multiple aircraft flight strategies.

Height 5000 ft or below

Time Required 5 minutes to complete one pass

References Accompanying diagram

Preconvective Patterns

The goal for preconvective flight operations is to document the inhomogeneities and mesoscale features near the boundaries along which convection is expected to occur. These boundaries include such features as the dryline, warm and stationary fronts, and old outflow boundaries. These flight patterns are included because there will be times the aircraft will arrive before storms develop, or it will be deemed important to sample the prestorm environment. As soon as the ground intercept teams are vectored to an initial position, the aircraft will break from the prestorm patterns and enter the convective mode and setup patterns on the convective storm of interest.

Pattern: Dryline or frontal boundary (INIT1)

Goal Survey the structure and gradients across the boundary, and along and in front of the boundary.

Sequence The Electra will fly a "U-shape" pattern at low levels. The P-3 will perform a vertical step pattern across the boundary.

Height The Electra will fly at low levels (500\q = 150m AGL). Approximate altitudes for the P-3 are 150, 1000, and 1500 m. An alternate pattern for the P-3 would be to fly at two altitudes (500\q below cloud base and 1000\q above cloud base).

Time Required The Electra\qs "U-shape" leg will take approximately 20-25 minutes. One cycle for the P-3 will also take approximately 20-25 minutes.

References Accompanying figure , Description of INIT1 in Ch. 3

Pattern: Intersecting boundaries (INIT2)

Goal Survey the structure and variability across two intersecting boundaries.

Sequence The Electra will fly a "L-shaped" pattern at low levels sampling the environment in all three regions. The P-3 will execute a vertical step pattern approximately 50 km east of the dryline to sample the conditions along one of the boundaries.

Height The Electra will fly at low levels (500\q = 150m AGL). Approximate altitudes for the P-3 are 150, 1000, and 1500m. An alternate pattern would be for the P-3 to fly at two altitudes (500\q below cloud base and 1000\q above cloud base).

Time Required The "L-shape leg of the Electra will take approximately 20-25 minutes. One cycle for the P-3 will also take approximately 20-25 minutes.

References Fig.23 on p.71 , Description of INIT2 in Ch. 3

Pattern: Pre-landspout boundaries (INIT3)

Goal Document wind shear and airmass differences across boundary where convection is predicted to develop.

Sequence P-3 and Electra are vectored to boundary and location of predicted convective development. Aircraft then fly box pattern at one-half cloud base height.

Height One-half observed cloud base height.

Time Required 20-25 minutes per box

References Description of INIT3 in Ch. 3

Technique: Convective Storm Fore/aft Scanning Technique (FAST; see diagram )

Goal Gather airborne Doppler radar data to deduce the 3-dimensional airflow during evolution of tornadic supercells.

Time Required 5 minutes to complete one pass.

Note The scanning strategy for the NCAR ELDORA is fixed as shown in the top diagram. To increase along-track resolution of the P-3, the sector-scanning mode (bottom diagram) is performed to one side of the aircraft. It may be deemed necessary, so as to further increase along-track scanning resolution, to execute only fore scans approaching the cell of interest, then all aft scans after passing the cell.

Technique: Multiple Aircraft Scanning Technique (MAST); see diagram )

Goal Gather airborne Doppler radar data to document the instantaneous structure of convective supercells via the aft scans of the P-3 and fore scans of the NCAR Electra.

Time Required 5 minutes to complete one pass.

Scientific Flight Crew Positions

The operation of the specialized scientific equipment on the P-3 is normally performed by the scientific crew. Personnel from AOC monitor the performance and recording of the main data system (in-situ flight-level data). The scientific positions include 2 chief scientists to plan flight tracks, coordinate with the Field Coordinator and Electra, and supervise data collection. Two radar scientists are required to interpret displays, monitor system performance, and maintain tape and event logs.

On the Electra, the flight crew consist of 2 pilots and 1 navigator. Three technicians and one scientist maintain the ELDORA (ELectra DOppler RAdar) radar. Two chief scientists coordinate with the Field Coordinator and P-3, plan flight tracks, and supervise data collection.

Instrumentation

There are three basic data systems on the P-3. These systems include the main data system for the in-situ data, the radar data system, and the cloud physics data system. The sensors that are serviced by the main data system are sampled at a rate of 40 Hz, and then are averaged to yield 1 sample per second. Derived parameters (such as wind) are calculated in post-processing once calibrations and biases are determined and removed.

There are two research radars mounted on the P-3; a horizontally scanning, C-band radar mounted in the lower fuselage (LF), and a vertically scanning X-band radar mounted in the tail (TA). The TA radar has the Doppler capability to estimate radial velocity of precipitation-sized hydrometeors.

The Electra is equipped to collect in-situ measurements of the standard kinematic and thermodynamic variables. The microphysics probes will not be on the Electra for VORTEX-95.

The ELDORA radar on the Electra consists of two X-band (3.2 cm) Doppler radars, pointing approximately 18.5 degrees fore and aft of the normal component to the aircraft heading, respectively. The radar continuously scans and may provide a horizontal resolution of 300 meters (assuming 120 m/s ground speed and antenna rotation rate of 144 degrees per second. The radar's half power beamwidth is 1.8 degrees. The dual-PRF capability of ELDORA provides a large nyquist interval of up to 80 m/s. Furthermore, since the minimum detectable signal at 10 km may be -12 dBZ, the radar's sensitivity should be great enough to detect clear-air echoes, such as along the dryline.

Communications

One of the most important aspects of coordinated observational platforms is good reliable scientific communications. The primary scientific communications mode between the two aircraft (P-3 and Electra) and the Field Coordinator will be by VHF radio. Primary air-to-ground and ground-to-ground radio communications will be carried out through an airborne repeater that will be installed on the NOAA P-3. The ground team\qs VHF radios as well as the airborne VHF radios will have the following frequency (MHz) assignments:

Channel 1: Tx 163.100 Rcv163.100

Channel 2: Tx 163.100 Rcv 165.435 (repeater channel)

Channel 3: Tx 163.275 Rcv 163.275

Scientific communications pertaining only to the airborne scientists will be on Channel 3. Communication between flight deck crews will be on the AOC frequency of 122.925 MHz. Beyond line-of-sight range, communications will be by air-to-ground telephone.

Return to Table of Contents