A Look at the Capabilities of the GV

When HIAPER starts supporting scientific research in mid to late 2005, it will signal the beginning of a new era of environmental research opportunities for the community. The performance capabilities of this new platform (see the table below and the figure at the end of this newsletter) will make it possible for investigators to deploy payloads as high as the upper troposphere and the lower stratosphere and to perform measurements over significant portions of the earth's surface.

The GV business jet is a finely designed, high performance aircraft, and the ability of investigators to fully capitalize on the research potential of this platform will require that certain principles and performance attributes be closely followed. For example, HIAPER will be capable of carrying payloads weighing up to nearly 8,000 lbs (3,629 kg). However, investigators should note that it will not be possible to deploy the largest possible payload to the maximum range or altitude of the aircraft. Payload weight added to the aircraft forces a reduction in the maximum achievable range and altitude for the GV. The specific metric for this relationship is as follows: for each additional 100 lbs (45 kg) of payload weight, approximately 24 miles (39 km) of range and roughly 30 ft (9 m) of altitude must be subtracted from the maximum obtainable range and altitude.

In a similar fashion, drag counts (i.e., the penalty due to aerodynamic forces on the aircraft) applied to the GV airframe also result in range and altitude reductions: 1 drag count (approximately equivalent to one small wing pod) applied to the airframe results in a reduction of roughly 24 miles (39 km) in range and approximately 66 ft (20 m) in altitude.

The above-outlined performance guidelines will not, however, translate into sacrificed research capabilities on the part of investigators. Rather, as the table at left illustrates, the GV will provide significant new opportunities for long range, long duration, and high altitude missions provided that careful attention is paid to the design and configuration of payloads for the aircraft. One of the cornerstones of successful mission performance with HIAPER will be the need for lighter, more power efficient, and aerodynamically "clean" instrumentation to be developed and deployed on the aircraft. Such instrumentation will make it possible to reduce payload weights and – in the case of sensors mounted on the exterior of the aircraft – reduce the drag counts on the airframe. Additionally, NCAR and external community scientists need to begin pursuing the development and usage of autonomous or semi-autonomous instrumentation that can either run in flight without an on board operator or that can be operated remotely by an investigator on the ground. These latter two categories of instrumentation will reduce the need for large numbers of investigators to fly on the aircraft, thereby making it possible to make room on board for more instrumentation or to reduce the total payload weight and provide opportunities for higher altitude or longer range flight.

The GV performance guidelines and associated instrumentation design considerations will, for some members of the community, require new methods of sensor development, and NCAR is prepared to partner with and support investigators as they pursue new instrumentation construction ideas and develop plans for deployment of the GV in support of various research missions.

A Work in Progress: Snapshots of the Start of the GV Modifications

The task of modifying the basic GV aircraft to prepare it for environmental research began in earnest in August, when Lockheed Martin personnel moved HIAPER into its modification "home" (Hangar 10) at the Lockheed modification facility in Greenville, SC. From 4-5 August, Gulfstream and Lockheed staff jacked the aircraft and shored it on rigging constructed specifically for the NSF/NCAR GV. This procedure went extremely well, and at the completion of the two days of work, the aircraft had been leveled to within a few thousandths of an inch (well within factory tolerances for the airframe). Leveling of the aircraft will be checked at regular intervals throughout the modification process in order to ensure that the GV fuselage and wings are not being twisted or distorted in any way by the work being performed to install the required modifications. Shown below is a picture of HIAPER after jacking and shoring had been finished.

HIAPER Following a Successful Jacking and Shoring Effort
(Click on image to enlarge)

Following the completion of jacking and shoring, Lockheed personnel began removing systems from the belly of the aircraft. This work was completed in September, and Lockheed engineers and technicians next turned their attention to preparing sections of the aircraft fuselage for the installation of modifications.

In late October, a small group of NCAR and UCAR staff members traveled to Greenville to participate in a series of meetings to review the status of work on HIAPER and to discuss detailed plans for the design of the liquid cooling system (LCS) and chemical exhaust system for the aircraft. This site visit also provided the NCAR and UCAR meeting participants with an opportunity to visit the GV and to see first-hand the work currently in progress on the aircraft. During this October visit, Lockheed personnel were working on the installation of support jigs and the removal of hundreds of rivets from the forward section of the top fuselage (see picture below) in preparation for the installation of a modification section known as the forward upper crown. The upper optical view port, three aperture plates, and three fuselage hard points will be installed in this forward upper crown area.

Lockheed Martin Personnel at Work on the GV Upper Fuselage
(Click on image to enlarge)

At present, it is planned that installation of the forward upper crown will take place during early 2004. Additional major milestones in the HIAPER modification effort are as follows:

In mid-November, NCAR personnel began conducting monthly site visits to Lockheed's modification facility to watch and document the work being done to the GV. Site visit personnel will be taking pictures of the GV modification effort as work proceeds in the coming months, and some of these pictures will be posted to the "Photo Gallery" section of the HIAPER web site to provide an ongoing pictorial record of the effort to develop the GV. Interested readers are invited to visit the HIAPER web site often in order to see the GV take shape as an environmental research platform.

Certified Versus Public Aircraft and Planned Operations of the GV

One issue of concern that has been raised by the scientific community is the planned operational status of the NSF/NCAR GV: specifically, will it be maintained and operated as a FAA certified (civil) platform or as a public aircraft? Before outlining NCAR's position on this matter, it is helpful to first present some background information to delineate the critical differences between these two types of aircraft operations.

The HIAPER aircraft will be delivered to UCAR/NCAR with a valid standard airworthiness certificate. This certificate will ensure that all modifications that have been made to the aircraft have been done in accordance with standards set forth in the federal air regulations for aircraft of its type. Following delivery to UCAR/NCAR (and once NSF owns title to the aircraft), it will be possible to operate the GV under either the rules that govern public aircraft or those that govern civil aircraft. By comparison, the NSF/NCAR C-130 – because of its former status as a military aircraft – can only be operated as a public aircraft. This is because this aircraft was built according to military standards, rather than civil aircraft standards. Public aircraft such as the C-130 are exempt from most FAA oversight requirements for modification and operation of the aircraft. In modifying and operating the NSF/NCAR C-130, however, NCAR personnel follow the same types of standards for engineering, installation, and maintenance as are required for civil aircraft. This is done to ensure that an adequate level of safety is maintained. However, operators of public aircraft are not legally required to follow these standards.

There are a number of advantages to operating an aircraft under civil standards. First, these standards are a guide to the safe operation of an aircraft. (Indeed, one would wish to follow these standards even if operating the platform as a public aircraft.) Second, the oversight provided by the FAA in the case of civil aircraft is an additional assurance of safety which is a critical factor in obtaining clearances to operate an aircraft in a foreign country. The types of operations permitted for public aircraft are limited (e.g., transport of cargo or passengers on public aircraft is not allowed), and operations of public aircraft may be further limited in the future. Thus, it is apparent that even if HIAPER were to be operated occasionally as a public aircraft, NCAR would want to be able to return the aircraft to civil operations at a later date. To do so would require returning the aircraft to its original, unmodified state or obtaining approval of all unapproved modifications. The latter can be very difficult to do after installation of such modifications and operation of the aircraft.

So, in order to maintain the greatest degree of flexibility regarding operations of the GV, NCAR intends to preserve the ability to operate the aircraft as a certified platform (i.e., to retain its civil status) through FAA approval of installations. NCAR will consider operating the aircraft in the public category, but only if a return to civil status can be assured through the removal of a particular installation and if the installation itself meets civil safety standards.

NCAR wishes to stress to investigators that the approval process for scientific equipment to be deployed on the GV is not expected to be adversely impacted by the decision to operate the aircraft in the civil category. The equipment approval process will be handled by NCAR and will not be significantly different from the process currently in use for equipment deployments on the C-130. Most GV research instruments will either be approved as non-required, miscellaneous equipment (following FAA guidelines) or will be approved under a restricted category airworthiness certificate, which is designed to allow for the deployment of special purpose equipment on civil aircraft. As an example of the latter, both the NSF/NCAR King Air and Sabreliner were operated with restricted category airworthiness certificates.

The goal of HIAPER operations will be to maintain the high level of safety that is afforded by a modern aircraft like the GV while also allowing for the greatest flexibility in operating the aircraft in accordance with the needs of the scientific community.

– Content in this section provided by Mark Lord (Aeronautical Engineer) and Jeff Stith (Manager) of the NCAR/ATD/Research Aviation Facility (RAF)

Infrastructure Overview

Following delivery of the modified GV to UCAR/NCAR in October 2004, NCAR staff will commence the installation and testing of a number of infrastructure components in the aircraft. The specific components to be designed and integrated by NCAR personnel are as follows:

• Data acquisition system
• Data display and access software
• Cabin research signal wiring and research power provisions in cabin equipment racks
• Intercommunication system (ICS)
• Cabin equipment racks and baggage compartment pump rack
• Wing pods
• Satellite communications (SATCOM) system
• State parameter and air motion sensing systems

The work to develop the specifications and design the above systems is being carried out by infrastructure integrated project team (IPT) subgroups that were established by the HPO in 2002. Each of these IPT subgroups is co-chaired by two NCAR staff members, and these co-chairs report directly to the HPO Engineering Manager and Project Director.

Efforts to develop the infrastructure systems for the GV are now well underway, and a special "HIAPER Specifications" section of the HIAPER web site has been created in which regular updates on the status of the various design and build efforts are posted. Interested members of the community are invited to bookmark this section of the web site and to check back frequently for the latest news and information.

Provided below are summaries of the basic specifications and intended capabilities for each of the infrastructure systems. Additionally, the present status of work on each task is described briefly.

Data Acquisition System: The new GV data acquisition system (DAS) currently under design will rely on distributed data sampling via small (approx. shoebox size) modules that will be located in the aircraft nose, cabin, baggage compartment, and wing pods as needed. The data acquisition development team has identified and purchased a new high speed, low power processor board for use in each sampling module that will allow for the efficient sampling and processing of collected GV data products throughout the full environmental regime (low temperatures to high) of the aircraft. The critical design review (CDR) for the data system effort was conducted in November 2002, and work is now progressing on the construction of the data sampling modules, the data interface boards (e.g., analog to digital [A/D] sampling boards, and ARINC 429, USB, and digital parallel/serial boards) and the real time sampling and digital signal processing (DSP) software for the GV system. To the greatest extent possible, the DAS will take advantage of commercial "off-the-shelf" boards that implement industry standard interfaces.

Data Display and Access Software: It is planned that investigators performing research with the GV will have access to a wealth of real-time data displays, including time series, histograms, soundings, and spectra. Additionally, the software being designed for the GV will make use of a structured query language (SQL) database for the storage of low-rate (1 sample per second) data products, and this database will be readable and writable by all instrument investigators. Other capabilities to be incorporated into the new data display and access package will include real-time data quality-checking to provide for the flagging of bad data values, real-time internet communications and data access both in flight and remotely from the ground, distribution and recording of imagery from the X-band weather avoidance radar mounted in the GV nose, and digital video camera display/image storage.

Intercommunications System (ICS): While the components of the ICS will be procured and installed by a third party vendor, NCAR staff have developed detailed specifications for the desired system. The system selected will be compatible with the GV flight deck ICS to be delivered with the aircraft. Presently, NCAR is planning on providing several stations in the main GV cabin, and one each in the nose and the baggage compartment. Cabin stations will provide users with the capability to talk over SATCOM and the aircraft VHF radios and also to the flight deck. NCAR personnel presently intend to purchase and have installed a hybrid analog/digital system that will allow for the system functions to be configured according to the requirements of a research aircraft. A preliminary request for proposals (RFP) for the GV ICS was released in late August 2003, and it is presently planned that the final RFP for the ICS will be released in early 2004.

Cabin Equipment Racks: The basic rack currently under design by NCAR personnel will provide investigators with a standard 19-in (48.3-cm) rack mount interface for instrumentation and equipment. Each rack will have dimensions of 22 in (55.9 cm) wide, 26.5 in (67.3 cm) deep, and 49 in (123.4 cm) tall. The maximum capacity of each rack will be 340 lbs (154 kg) of equipment with a center of gravity (CG) 29 in (73.7 cm) above the floor attachment plane. Ceiling attachment points are also being installed in the GV to which racks can be secured to compensate for high rack overturning moments.

Wing Pods: Over the course of the past several months, NCAR personnel have been researching a number of wing store options for the GV. At present, NCAR is considering commercially available pods for possible deployment on the aircraft. In late December 2003, Gulfstream completed an aerodynamics study of two commercial pods that have been proposed for use on HIAPER, and NCAR personnel are presently in the process of reviewing these study results and determining the next steps to be taken in making an initial pod selection for the aircraft. Updates on the pod selection process will be provided to the scientific community as soon as possible in the coming weeks. For additional information regarding the GV wing pod selection process, interested readers can visit the following URL: www.hiaper.ucar.edu/specs/aircraft_infrastructure_systems.html
#engineering_design_pods.

SATCOM System: A critical component of the GV data distribution and communications system will be the SATCOM selected and installed on the aircraft. The desired capabilities of the system planned for HIAPER include global coverage (where available), multi-channel configuration (for simultaneous voice and data transmission), high bandwidth (the presently achievable rate is 128 kbits/sec), and the ability to interface to the 4 cabin ICS for easier communications between the aircraft and the ground and vice versa. The SATCOM system components will, as with the ICS, be procured and installed by a third party vendor, and present plans call for the RFP for the HIAPER SATCOM to be released in early 2004.

State Parameter and Air Motion Sensing Systems: NCAR staff members are presently making plans for the installation of a non-deiced radome gust probe (three-dimensional winds) system on the GV during the infrastructure integration window of November 2004 to June 2005. Additionally, a research pitot-static system (to be installed by Gulfstream and separate from the aircraft pitot-static systems) and ambient pressure, temperature, and dew point sensors will be installed on the aircraft for basic state parameter measurements. Should available HIAPER infrastructure funds permit, NCAR will also consider purchasing additional standard instrumentation (e.g., trace gas sensors, high altitude radar altimeter, etc.) for the GV.

A Plan for the Start of GV Operations: The 2005 Progressive Science Missions

After extensive discussions with members of the HIAPER Advisory Committee (HAC; see www.hiaper.ucar.edu/hac.html for more information about this advisory body) and other representatives of the scientific community, NCAR and NSF have elected to pursue a gradual start to operations of the GV in support of environmental research. To that end, a series of progressive science missions will be conducted with the aircraft from approximately July to mid-December 2005 from the GV base of operations, Jefferson County Airport in Broomfield, CO. The following specific objectives have been established for these initial missions:

• NCAR/ATD staff charged with ongoing operation and support of the GV will be provided with a significant time period during which to become thoroughly familiar with the operation and performance capabilities of the aircraft and with the operation of the various infrastructure components on the aircraft;
• NCAR staff will be able to support the gradual development of fundamental (standard) instrumentation for the GV;
• ATD staff will be given a suitable time period during which to work through payload certification processes and issues;
• The capabilities of the aircraft will be showcased to the scientific community, as flight profiles will be executed that involve taking the aircraft to its maximum certified ceiling of 51,000 feet (15,545 m) and fully demonstrating the new data acquisition, display, and transfer capabilities of the GV infrastructure systems;
• Members of the scientific community will, at the same time that the above objectives are met, be given a valuable opportunity to perform initial, well-defined scientific missions using the GV.

In early December, ATD and the HPO released an announcement to members of the scientific community inviting interested investigators to submit Letters of Intent (LOI) to ATD requesting consideration for participation in the progressive science missions. The deadline for submission of these LOIs was 15 January 2004, and ATD and HPO personnel are now in the process of reviewing the submitted requests.

All submitted LOIs will be considered by the Observing Facilities Advisory Panel (OFAP) during the April 2004 session, and it is anticipated that final decisions regarding selected mission participants will be announced as soon as possible following the April OFAP meetings.

Following the conclusion of the progressive science missions (i.e., in late December 2005), the GV will formally become available for the support of full-scale research operations.

Comparison of NSF/NCAR C-130 and HIAPER Altitude and Range Capabilities
(Click on image to enlarge)

Comparison of the Maximum Ranges for HIAPER (Black Circle*), the NSF/NCAR C-130 (Red Circle*), and the NASA ER-2 (Blue Circle*)
* Note: The circles shown represent the maximum distance to which each aircraft can fly from a base at Jefferson County Airport in Broomfield, CO (represented by the star) and return to the same base. Ranges shown correspond to flight of each aircraft at optimum altitude for ferry (12,497 m for HIAPER, 6,096 m for the C-130, and 19,812 m for the ER-2) and with the maximum possible payload deployed on each aircraft.

Questions about this Newsletter or about the HIAPER project in general? Please contact the HIAPER Project Office at hiaperinfo@ucar.edu or 303-497-2005.