Notice

5.1 Scope

This section describes the aircraft platforms and instrumentation, the aircraft base at Ponca City, the flight

mission modules, crew rest, mission decisions and planning, in-flight decisions, debriefing, post-mission quality control, and post-experiment data processing and quality control.

5.2 Aircraft Platforms and Instrumentation

5.2.1 King Air

5.2.1.1. General Characteristics

This aircraft is a Beechcraft King Air model 200T, operated by the University of Wyoming. Its payload is 14,000 LB; its endurance 4.25-4.5 hours, corresponding to a range of about 1600 km at 100 m/s The King Air operates at a true airspeed of 80-110 m/s. Typical data-sampling speed is 160 kt (30 m/s)

Table 5.1 UW King Air Scientific Payload for CASES 97

5.2.2. NOAA Twin Otter

5.2.2.1. General Characteristics

The NOAA Twin Otter is a DeHavilland DH-6 Twin Otter, Series 300. It is unpressurized, and can operate at altitudes up to 25,000 ft. It can hold up to 4,800 pounds. With a fuel load of 2,500 pounds, its capacity for personnel and cargo is 2,300 pounds. At sea level and an airspeed of 120 kt (65 m/s) , it can stay airborne for 4.2 hours. Typical data-gathering speed is 110 kt (60 m/s).

5.2.2.2. Instrumentation Payload. Figure 5.2 - Twin Otter Aircraft Instrumentation)

5.3 Aircraft Base

The Ponca, City, OK airport will be the aircraft base of operations. This facility meets the needs for hangar space, power, fuel, runway length, ability to make coordinated takeoffs, and ILS landing system. Coordination with the CASES-97 main operations center is discussed in Section 2.

5.4 Flight Mission Modules (Appendix 5A, Modules 1-6)

5.4.1 Use of Flight Mission Modules

Flight mission modules, described in the Appendix, are designed as part of aircraft missions to enable estimates of boundary layer budgets of momentum, sensible heat, and water vapor. They can be used for single or coordinated aircraft missions. Aircraft will fly more than one mission a day; these can be single-aircraft (to optimize time coverage) or dual-aircraft (to optimize spatial coverage) missions.

5.4.2. Low-level Flux Runs

The FAA has granted low-level flight restriction waiver to the NOAA Facilities for CASES-97. The NSF Facility will operate without a waiver under FAA Rule 91 which specifies low-level flight restrictions.

Low-level flux runs require track lines that meet FAA requirements (avoid houses, cattle pens, major highways). Preliminary tracklines have been determined; these will be refined by the pilots, and marked by GPS-determined end points before low-level data runs are made. The flight lines will be used to define the lowest-level (100-200 feet) leg of any of the flight patterns.

These flight lines are based upon Rule 91 which also governs the NOAA waiver, and they have been passed on to Wichita FAA officials. Flight operations are more flexible in the central and eastern parts of the watershed than the western part of the watershed which is close to an urban area (Wichita, KS) and a Military Operations Area (MOA).

5.4.3 Ferry from Ponca City to CASES-97 Domain

Aircraft missions out of Ponca City will begin with a ferry to the Oxford profiler (37.2743N; 97.095W) west of Winfield, KS at either 500 ft above the highest point along the route or 200 ft below cloud base. Upon reaching the profiler, the aircraft will continue on its track for one minute, and then perform a sounding from 100 ft to above the capping inversion. It will then commence the flight pattern chosen for that particular mission.

When there are more than two missions for an individual aircraft in one day, the aircraft will land and refuel at Augusta airport in the middle of the watershed.

5.4.4 Data Assurance Strategies

Low-level flux runs require minimal deviations from straight and level flight. Roll and pitch angles need to be less than five degrees unless perturbed by atmospheric turbulence. Turns to avoid obstructions along the track should be anticipated and made with minimal bank (flat turns). However, safety must not be compromised.

Intercomparison legs will be part of each coordinated mission. The scientific flight directors will log the altitude and start and stop times for each intercomparison.

5.4.4.1. Aircraft Self-Calibration Maneuvers (Appendix 5A, Modules 7-10)

When there are clouds, each mission should include a pop-up sounding that just barely penetrates the cloud base to check temperature-dewpoint depression (Appendix).

Scientific flight directors will also be responsible for insuring each mission contain maneuvers for checking wind velocity biases (Appendix).

5.4.4.2. Aircraft-Aircraft Intercomparisons

Spatially coordinated missions will require that the two aircraft fly wing-to-wing formation along the Ponca-Winfield ferry for intercomparison purposes. Temporally coordinated missions will require a rendezvous and a wing-to-wing intercomparison of five minutes (or whatever is logically possible) before the outgoing aircraft departs for base.

For planning purposes, 20 minutes of flight time should be reserved for intercomparisons.

5.4.4.3. Comparisons with other instrumentation

Comparisons with profilers and surface flux stations will be part of each mission. Surface flux intercomparisons will be at as low above the surface as possible; comparisons to profilers should be at height(s) corresponding to routine profiler observations.

5.4.4.4. Aerial Photos

At least once during the experiment, it would be useful to obtain aerial photographs of each surface stations. A locally-owned, single-engine aircraft can be used for this purpose.

5.5 Communication

Radio contact will be necessary between aircraft as well as between the aircraft and the CASES Coordination Center in Augusta. The primary use of radio contact will be safety (coordination with balloon launches), boundary layer mean wind (for orientation of cross-wind legs) and boundary layer height (communication of sudden changes). Secondary needs include comparisons of boundary layer height, surface-mixed layer comparisons of flux, surface temperature, and meteorological parameters (especially wind).

122.925 MHz is the dedicated frequency for CASES-97. A VHF base station will be located at the CASES Coordination Center at the ABLE Office in Augusta, KS.

5.6 Flight Operations Procedure

Flight mission choices will reflect the accomplishment of the operational objectives associated with the scientific objectives. Crew rest and aircraft availability must also be taken into account in the mission choice decision. Grossman, LeMone, and McMillen will discuss flight mission candidates the night before. There will always be two choices of missions (a Plan A and Plan B), even if Plan B is "Cancel."

5.6.1. Flight-planning time line

5.6.1.1. Decision Sequence (See Table 2.1)

If an IOP for the following day has been ordered, detailed flight planning will begin at 1630 among the PIs at Ponca City and the pilots. Once plans are firm, they will be faxed to the CASES Control Center by 0800 CDT the day of the IOP.

5.6.1.2. Flight Operations Sequence in Ponca City

With emphasis on following the diurnal cycle, early-morning takeoffs (~ 0830 LDT) will be frequent for one or both aircraft. In such cases, the items under Takeoff - 3 hours should be taken care of the night before.

Takeoff - 3 hours

• Final scientific/systems status review.
• Final Decision of Plan A or Plan B.
• Initial weather review (PI).
• Science briefing to pilots (brief description of objectives, special flight operation considerations.
• Pilots and scientists discuss and refine flight plan.

• Final weather briefing (PIs and pilots).
• Final flight plan detailed for transmission to FAA (PIs and pilots).
• Pilots obtain official weather information for flight plan, file FAA-approved flight plan for mission.

5.6.2 In-Flight Operations Decisions

While the Scientific Flight Director may suggest certain flight operations and changes to these operations while in flight, the Flight Commander makes the final decision. This safety principle will never be compromised.

5.6.3. Debriefing in Ponca City (for timing, see Section 2.2.1)

Each flight mission will include a debriefing after the mission is complete to include:

• Operational Overview: (pilots, flight directors): what went right, what went wrong, what can be improved. Pilots released; they can stay on if they wish.
• Systems Overview: (Facilities technicians, flight directors): how did the instruments perform. Problems? Any corrections/repairs needed? Time to correct/repair? Technicians released; they can stay on if they wish.
• Science Overview. (Scientific flight directors, flight observers): given instrument status how well did mission accomplish its objectives? Anything unusual, typical? What can be improved?
• Outlook for future missions of this type (Flight Directors, PIs)

 5.6.4 Post-Flight Quick Look Data Processing

• Facilities staff normally check engineering aspects of the individual data streams such as noisy signals, calibrations, biases, unrealistic values, differences between similar instruments. This evaluation should normally take place after each flight and reported at the next operations meeting under System Status.
• Scientists} will be responsible for assessing

(a) reasonableness of the data in light of the scientific objectives,

(b) adequacy of averaging lengths for flux estimates,

(c) reasonableness of spectra and cospectra of the important variables

(d) intercomparison between aircraft and surface systems

(e) preliminary budget computations.

Probably only (a) (and possibly (d)) will be possible by the next operations meeting.

• Use of Computers. Scientists will be responsible for their own hardware and software to carry out their quality control procedures. If invited, they can use Facility computers and software. The NOAA and NSF PIs are strongly encouraged to use a common software package to estimate airborne fluxes. NCAR/MMM will supply an interactive software package to estimate statistics and fluxes while in the field. The Univ. of Colorado will provide a batch flux computation package which has been used successfully in several previous field expeditions and publications.

 The PIs need to be able to read the aircraft data in the field to evaluate the success of the aircraft and missions in fulfilling the scientific objectives. A common in-field data format would be highly advantageous. Facilities need to coordinate with the PIs to insure the post-flight data media and format are compatible with their hardware and software.

5.7. Post-Experiment Processing and Quality Control

5.7.1 Output format

A common output data format for both NOAA and NSF is strongly encouraged as this will greatly speed post-flight analysis. NETCDF format is suggested.

We expect three data sets to emerge:

• Quick Look data These data may be subject to further refinement and correction by the Facilities. Dissemination is to the aircraft PIs only; in no circumstances should these data be released to the public. However, use by CASES-97 PIs is permitted. These data will reside in a temporary archive.
• Final data set. These data are the basic parameters from the Facilities which is initially disseminated to the aircraft PIs and permanently archived at the Facilities. These data will be made available to the public following procedures outlined in the CASES-97 Data Management Plan.
• Processed data. These data files will consist of simple statistics (median, mean, standard deviation, skewness, frequency distributions, correlations), fluxes, linear trends, spectral-cospectral analysis, conditional sampling analysis products. This output will be the responsibility of the PIs. Making these products available to the public is also the responsibility of the PIs, following procedures outlined in the CASES-97 Data Management Plan.

 5.7.2. Data availability for quick look

• King Air: Quick-look data will be given to the PI before the end of the field program. The final data set will require further QC by the University of Wyoming and by the PI. This process should take several months.
• Twin Otter:

5.7.3. Facility scientific interests

The Facilities are encouraged to take a scientific interest in the data they collect for CASES-97. If such a scientific interest arises within the Facility, coordination with CASES-97 PIs is encouraged as well.

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Last Modified: 20 Aug 1997