THE SMALL AIRCRAFT TRANSPORTATION SYSTEM (SATS), HIGHER VOLUME OPERATIONS (HVO) OFF-NOMINAL OPERATIONS B. Baxley, D. Williams, M. Consiglio, S. Conway, and C. Adams NASA Langley Research Center, Hampton, VA T. Abbott Booz Allen Hamilton, McLean, VA Abstract weather to make decisions regarding flight path sequencing, separation, and spacing based on The ability to conduct concurrent, multiple aircraft information displayed in the cockpit.2 A supporting operations in poor weather, at virtually any airport, document to this paper is the normal HVO procedures offers an important opportunity for a significant paper.3 More information can be found on NASA’s increase in the rate of flight operations, a major web page http://ntrs.nasa.gov. improvement in passenger convenience, and the potential to foster growth of charter operations at small Review of HVO Normal Operations airports. The Small Aircraft Transportation System, During periods of Instrument Metrological Conditions (SATS) Higher Volume Operations (HVO) concept is (IMC), a block of airspace is established around the designed to increase traffic flow at any of the 3400 non- airport within which pilots will separate and space radar, non-towered airports in the United States where themselves from other similar SATS HVO equipped operations are currently restricted to “one-in/one-out” aircraft. A ground based system provides the pilots procedural separation during Instrument Meteorological their arrival sequence. All participating aircraft within Conditions (IMC). The concept’s key feature is pilots this airspace provide their own separation using a maintain their own separation from other aircraft using combination of procedures and specialized tools, procedures, aircraft flight data sent via air-to-air including localized surveillance data. datalink, cockpit displays, and on-board software. This HVO relies on participating aircraft to broadcast critical is done within the Self-Controlled Area (SCA), an area flight information, such as position, heading, airspeed, of flight operations established during poor visibility or and projected flight path to other aircraft (e.g., ADS-B). low ceilings around an airport without Air Traffic Flight information is received by all aircraft and Control (ATC) services. displayed to the pilot. The pilot’s awareness of this traffic, along with HVO procedures, enables a The research described in this paper expands the HVO distributed decision-making environment where the concept to include most off-nominal situations that pilot maintains separation and spacing regardless of low could be expected to occur in a future SATS visibility or ceilings. environment. The situations were categorized into routine off-nominal operations, procedural deviations, The SATS HVO concept does not depend on a control equipment malfunctions, and aircraft emergencies. The tower or designated approach times but rather allows combination of normal and off-nominal HVO the pilot to descend and then follow the preceding procedures provides evidence for an operational aircraft on the instrument approach with appropriate concept that is safe, requires little ground infrastructure, spacing. The pilot uses the onboard equipment to verify and enables concurrent flight operations in poor that the altitude and location to which his aircraft is weather. descending is free of other traffic. Once adequate spacing behind the preceding aircraft is achieved and can be maintained throughout the approach, the pilot HVO Off-Nominal Procedures would begin the approach. The Problem HVO Off-Nominal Research Conducted NASA’s Small Aircraft Transportation System (SATS) HVO off-nominal procedures are similar to today’s Higher Volume Operations (HVO) Project was instrument flight procedures in that the pilot is expected designed to provide a means to accommodate the to communicate the emergency and intention4, has the anticipated 20% increase in air traffic by 2010.1 One authority to deviate from regulations for flight safety5, approach is a concept that allows pilots flying in poor and use judgment since not every off-nominal or 1 American Institute of Aeronautics and Astronautics emergency is governed by procedures. The Airport Procedural Deviations Management Module (AMM, defined in reference 3) • Aircraft returning to the incorrect Missed and HVO procedures cannot handle every conceivable Approach Holding Fix (MAHF). emergency just as today’s rules do not provide guidance • Loss of aircraft spacing on approach. for all situations, and voice communication remains key • Unable to use an assigned Initial Approach Fix to the safe resolution of off-nominal situations in both (IAF) or MAHF. today’s and HVO’s operating environments. Equipment Malfunctions The SATS HVO project ended prior to completing • Loss of aircraft state data output, arriving aircraft. research in this area, therefore this paper presents: • Loss of aircraft state data output, departing aircraft. 1. a comprehensive but not complete list of off- • Loss of aircraft state data input, arriving aircraft. nominal HVO procedures that addresses enhanced • Loss of aircraft state data input, departing aircraft. operations, procedural deviations, equipment • Loss of AMM output. malfunctions, and aircraft emergencies; • Loss of AMM reception by a single aircraft. 2. a draft implementation that has been validated for • Loss of aircraft voice communication capability. the Pilot Cancellation of an Approach Request, and Priority Landing Request from Arriving Aircraft Aircraft Emergencies procedures (selected because they have a practical • Priority landing request from arriving aircraft. expectation for occurrence, stretch the concept, and may be the most difficult handle)6; • Priority landing request from departing aircraft. 3. and a non-validated draft implementation for the Implementation Considerations remaining identified conditions. The consideration of off-nominal conditions and the development of their operational procedures have led to The development of off-nominal HVO procedures also an incremental increase in the complexity of the normal required changes and enhancements to the original operations. However, as in the development of the configuration of the AMM and HVO normal procedures.7 In particular, communication equipment normal operations, these new procedures were based whenever possible on similar, existing procedures for failure meant adding messaging hand-shake protocol to off-nominal events. the AMM functionality and the HVO normal procedures. Off-nominal operations, especially equipment failure detection, require system-to-system periodic checks and Significant further development is needed for HVO off- some data retention. These seven requirements were nominal procedures, to include identifying situations or identified to support HVO off-nominal procedures: conditions requiring procedures, hazard and safety analysis, fault trees, input from a broader range of 1. Changes to the Self-Controlled Area (SCA) state experts, and procedure validation experiments. data information. a. A system-to-system information exchange Finally, off-nominal procedures can be implemented in requires confirmation from the receiver back various ways. Any mention in this paper of a Pilot to the sender (e.g., AMM to the aircraft). Advisor or Multi-Function Display (MFD) in these b. An aircraft-to-pilot information exchange procedures is just one approach to implementation, and requires confirmation (e.g., the pilot responds does not preclude other implementation solutions. to a change by pressing a button). 2. Periodic AMM status messages to all aircraft. Off-Nominal Categories 3. Periodic ADS-B messages from the AMM to The off-nominal conditions were categorized as: participating HVO aircraft. This message is enhanced procedures (expected operations), procedural necessary to alert aircraft to their: deviations (pilot error), equipment malfunctions, and aircraft emergencies.8 a. Loss of ADS-B transmit capability b. Loss of the Airport Pilot Data Link Communication (APDLC) receive capability. Routine Off-Nominal 4. Prior to takeoff, departing HVO aircraft would • Pilot cancellation of an approach request. require reception of both an AMM status message • Change of approach (runway) direction. and an ADS-B reception message from the AMM. • Pilot cancellation of a departure request. 5. Current SCA status information would be sent • Leading aircraft conducting a circle-to-land. from the AMM (e.g., the number of operations and aircraft identification). 2 American Institute of Aeronautics and Astronautics 6. Participating aircraft retain sequence data from the it is not considered for the HVO arrival sequence AMM on all surrounding SCA traffic (used by and is not a factor for IFR clearance requirements). pilots in situations when reversion to pilot-to-pilot 2. For aircraft with an approach sequence that has procedural separation is required due to loss of been changed (re-sequenced by the AMM), the aircraft state data information). MFD notifies the pilot of changes in information 7. Periodic AMM normal operation status messages (e.g., new leading aircraft and/or MAHF). sent to ATC (e.g., the number of operations and 3. Each respective MFD inhibits further Pilot Advisor aircraft identification). messages (e.g., OPEN 3000, OPEN APPROACH) until that pilot of the re-sequenced aircraft It is also important to note that while ADS-B would be acknowledges the re-sequence. the primary means for the dissemination of aircraft state data, an addressed datalink could be used to provide a For all procedures that require an information exchange secondary means for data exchange. Therefore, failures between the pilot and the onboard system (e.g., such as the loss of state data transmission are cancellation request), an acknowledgement by the pilot procedurally addressed only if all means of is required. Similarly, information exchange between transmission have failed. the onboard system and the AMM also requires an underlying, or system-to-system data exchange confirmation. This acknowledgement could occur via a Routine Off-Nominal Operations data link “handshake” between the two systems. Pilot Cancellation of an Approach Request Change of Approach (Runway) Direction A routine off-nominal event is for pilots to cancel their Who and how the active runway will be established and approach request and continue under VFR. This how that information will be disseminated has not been procedure would be used when weather conditions determined as part of this project. It could be a function within the SCA allow for transition from IMC to Visual of ATC, however, pilots should be able to provide Metrological Conditions (VMC). This procedure was feedback and input into the decision regarding the one of two selected for the HVO-Off-nominal selection of the approach and the active runway. simulation experiments conducted at NASA Langley in January 2005. The pilot workload and situation It should also be noted that normal changes of runway awareness results from these tests were very good, and landing direction should be managed prior to aircraft indicated the HVO procedures as developed are safe being assigned approach sequences. That is, ATC and can be flown while in IMC (reference 6). should inhibit arrivals until all ongoing SCA operations have been completed, holding the new arrivals above Actions by the pilot and AMM when canceling HVO: the SCA until all current SCA operations have been 1. The pilot cancels the approach (button on MFD). completed (akin to ATC procedures in radar approach 2. The AMM sends cancellation notice back to the environments). For those less than desirable situations canceling aircraft. where a change to the approach direction (active 3. If the canceling aircraft has not received an runway) must take place while aircraft are conducting approach sequence (i.e., it was outside the SCA HVO operations, the following should occur: with a “Standby” notification): a. AMM deletes the aircraft from request queue. All pilots, ATC, and AMM involved in runway change: 4. If the canceling aircraft has received an approach 1. ATC directs AMM to inhibit all new operations. sequence (whether inside or outside the SCA): 2. The AMM confirms to ATC that there are no new a. Pilot announces cancellation over the radio. operations, and identifies all active HVO aircraft. b. The AMM removes the canceling aircraft from 3. All landing aircraft either land or conduct a missed the approach sequence. approach; all departing aircraft hold their position. c. The AMM re-sequences the remaining aircraft 4. Missed approach aircraft contact ATC to obtain a to follow the aircraft canceling HVO. clearance, preferably to the IAF of the new d. The AMM sends the new sequence runway. If unable to obtain a clearance, the aircraft information to all HVO aircraft. remains in the SCA and flies to the MAHF 5. The AMM marks the aircraft as non-participating. previously assigned by the AMM. This data is passed to all aircraft for display. 5. At the completion of all HVO approach operations, ATC directs the AMM to resume SCA operations. Other aircraft within the SCA: 1. Each respective MFD identifies the canceling aircraft as non-participating aircraft (i.e. indicating 3 American Institute of Aeronautics and Astronautics Pilot Cancellation of a Departure Request This condition may occur due to the pilot experiencing mechanical difficulties or being unable to depart prior to the Clearance Void Time. The following should occur for a canceled departure: 1. Pilot Advisor alerting would be inhibited for the canceling aircraft, i.e., no OPEN DEPT message. 2. All other aircraft continue their normal operations. 3. Pilot requests a new clearance from ATC. Leading Aircraft Conducting a Circle-to-Land This situation could occur if the leading aircraft plans to circle to land (normally due to wind). This situation received only rudimentary attention prior to the Program ending, and further development is required. For aircraft within the SCA: 1. Prior to departing the IAF to initiate the approach, Figure 1. HVO MFD (white own-ship, traffic to follow the pilot of the leading circle-to-land aircraft double-blue chevron, green “Entry” message, solid line broadcasts this intent to all other aircraft. instrument approach, dotted line missed approach) 2. The following aircraft adds an additional distance or time interval to the nominal spacing value for Loss of Aircraft Spacing on Approach the approach spacing. This procedure is for aircraft on approach that is about to lose, and will not be able to regain, spacing with the preceding aircraft. (Loss of separation while in holding Procedural Deviations or on missed approach will be examined in the next phase of research.) For loss of spacing to occur: Aircraft Returning to the Incorrect MAHF • the pilot did not adhere to HVO procedures (left This procedure addresses the pilot who flies the the IAF too soon, flew too fast, etc); incorrect missed approach procedure to the wrong • the pilot ignored, or could not resolve, cautions Missed Approach Holding Fix (MAHF). Note that for and warnings from onboard conflict detection a pilot to turn toward the wrong MAHF, the pilot: software (a requirement for HVO equipage). • performed the wrong missed approach procedure; • if implemented, ignored the Pilot Advisor (or Trailing aircraft that will lose spacing on approach: Cockpit Associate, etc) alert for an incorrect 1. The pilot begins a climb to its missed approach missed approach procedure (text box in Fig 1); altitude as required for vertical separation. • ignored the MAHF identified in the MFD “to 2. The pilot flies the lateral path of the approach and waypoint” data block (text box in Figure 1); missed approach to the MAHF. • and ignored the missed approach procedure depicted on the MFD (dotted line in Figure 1). Unable to Use an Assigned IAF or MAHF Actions by the pilot who turns to the wrong MAHF: This condition may occur because of weather at the IAF. 1. Make a call over the local radio frequency Aircraft that cannot use an assigned IAF or MAHF: announcing the problem. 1. If still in ATC managed airspace, the pilot: 2. Continue climbing along the errant missed a. Coordinates with ATC to proceed to the other approach path to an altitude above the SCA (due to IAF or divert to another airport. potential loss of separation with other aircraft on 2. If within the SCA, the pilot: the instrument approach, this aircraft must not a. Climbs in the safest possible manner to avoid attempt to return to the assigned MAHF). obstacles, other aircraft, and severe weather. 3. Contact ATC as soon as possible and announce the Contact ATC prior to departing the SCA. problem and requests an IFR clearance from ATC b. Notifies ATC of the situation and intentions. (if possible, this clearance should be obtained prior to departing the SCA). Equipment Malfunctions 4 American Institute of Aeronautics and Astronautics Loss of ADS-B Output on an Arriving Aircraft Prior to conducting an SCA departure operation, This situation occurs if an HVO aircraft loses the aircraft would perform an ADS-B and APDLC check capability to transmit state data information via ADS-B. with the AMM. If a successful link check can not be performed, SCA operations cannot be done by that Aircraft Without an Arrival Sequence: aircraft. In this instance, this departing aircraft would (Part of the arrival sequencing process that the AMM be required to revert to unequipped operations. performs is the confirmation of ADS-B state data output from the requesting aircraft.) 1. The AMM would attempt to confirm the aircraft’s Loss of ADS-B Input on an Arriving Aircraft ADS-B transmit capability (and all other output This situation would occur if an HVO aircraft has lost capabilities) prior to the sequence notification. the capability to receive ADS-B information from other 2. If there is no ADS-B output, the aircraft would be aircraft within the SCA. Several options were notified of this condition and it would be denied an developed, and further effort is required to determine approach sequence. the most appropriate procedure. Aircraft With Arrival Sequence and with APDLC Output: Aircraft Without an Arrival Sequence: (The aircraft has an approach sequence and APDLC 1. Prior to the sequence notification, the AMM capability, but subsequently loses its ADS-B output.) attempts to confirm the aircraft’s ADS-B reception 1. The AMM, noting the loss of the ADS-B signal, capability (and all other input capabilities). would inhibit all new SCA operations and set the 2. If there are no ADS-B inputs to the AMM, the SCA status message to no-new-operations. aircraft is denied an approach sequence. 2. The AMM notifies ATC that the SCA is in an inhibit status. Aircraft With Arrival Sequence and with APDLC Input: 3. The AMM sends that aircraft a “lost ADS-B 1. The aircraft with the equipment problem would output” message that could be displayed as an alert notify the AMM of the loss of ADS-B reception. message on the MFD. The problem aircraft 2. The aircraft with the equipment problem would use transmits its position data over the APDLC. the APDLC-received state data as necessary. 4. The AMM resumes normal operations after the 3. The pilot would continue SCA operations. problem aircraft has landed and would also reset the SCA status to allow new operations. Aircraft With Arrival Sequence but no APDLC Input: 1. The aircraft with the equipment failure would Aircraft With Sequence but without APDLC Output: notify the AMM of the loss of ADS-B reception (Aircraft has an approach sequence but subsequently capability. loses both its ADS-B output and its APDLC capability.) 2. The AMM inhibits all new SCA operations. 1. The AMM, noting the loss of an ADS-B signal 3. The AMM notifies ATC that the SCA will accept from an aircraft and all other output capability, no new operations. inhibits all new SCA operations and sets the SCA 4. The AMM would send all aircraft an “unable to status message to no-new-operations. receive” message, identifying the aircraft that had 2. The AMM notifies ATC that the SCA is in an lost its reception capability. inhibit status. 5. All aircraft conducting approach operations would 3. The AMM would send all aircraft a “lost signal” revert to procedural separation using voice message via the APDLC, identifying the aircraft communication and continue approach operations that had lost its transmission capability. using their original sequence assignments. 4. All aircraft conducting approach operations revert 6. The AMM would resume normal operations after to procedural separation using the local radio the problem aircraft has landed and would reset the frequency, and continue the approach operations SCA status to allow new operations. using their original sequence assignments. 5. Departure operations would be inhibited until the Loss of ADS-B or APDLC Input on Departing Aircraft aircraft with the problem lands. Part of the departure process is confirmation of ADS-B 6. ATC would notify the AMM that the problem state data input to the requesting aircraft. The pilot aircraft has landed or departed the SCA via a must confirm the aircraft’s ADS-B reception capability ground-based message. (and all other input capabilities). If this confirmation fails, this aircraft reverts to unequipped operations. Loss of ADS-B or APDLC Output on Departing Aircraft Loss of AMM Output 5 American Institute of Aeronautics and Astronautics The AMM sends a periodic operational status message 5. ATC enables the AMM for new HVO operations to ATC and to all proximate aircraft via APDLC. Loss after the lost communications aircraft has landed. of this operational status message indicates a failure of the AMM, and all new operations must cease. Arriving Aircraft Inside the SCA: 1. Normal operations continue (voice-communication Action by pilots and controllers: loss should not be a critical issue since the 1. ATC restricts new SCA entries and departures communication radio is only used as a secondary (ATC is informed of an AMM failure though the means for situation awareness and for redundancy loss of the periodic status message). in other off-nominal procedures). 2. Onboard aircraft systems provide notification to the pilot that the AMM has failed (identified Departing Aircraft: through the loss of the AMM status message). 1. Aircraft on the ground may not depart. 3. Pilots with an assigned arrival sequence use the 2. Departing aircraft already airborne use current IFR radio to corroborate their landing sequence. lost-communication procedures. 4. At the completion of all HVO operations, the airport reverts to non-HVO operations. Emergency Procedures Loss of AMM Reception by a Single Aircraft As noted previously, the AMM sends a periodic status Priority Landing Request from Arriving Aircraft message to all aircraft via the APDLC and to ATC. This procedure applies to aircraft that have an approach Loss of this operational status message indicates an sequence and that must land immediately due to an APDLC receiver failure on the SATS aircraft. emergency. Aircraft without an approach sequence are under ATC control and coordinate using today’s Pilots operating within the SCA: procedures. This procedure was one of two selected for 1. Pilot announces the loss of the AMM on the radio. a simulation experiment conducted at NASA Langley If more than one aircraft has lost AMM reception, in January 2005. The pilot workload, situation use the Loss of AMM Output procedure. awareness, and usability results were very good, and 2. Pilots use the radio to confirm their sequence. indicate the procedures as developed so far are safe and can be flown while in the weather in airspace not managed by air traffic control (reference 6). Loss of Voice Communications HVO procedures were developed to accommodate the The Requesting (Emergency) Aircraft: situations when aircraft lose their radio communication 1. Announce the emergency and intentions via voice capability. Following normal HVO procedures assures communication. pilots the ability to self separate within the SCA and 2. Broadcast “Emergency Landing” to the AMM and land according to the AMM generated sequence. For other aircraft (MFD, Cockpit Associate, etc). aircraft in ATC airspace, traditional procedures are used 3. The AMM inhibits all new SCA operations. in conjunction with the HVO arrival procedures. 4. The AMM notifies ATC that the SCA status has been changed is not accepting new operations. Arriving Aircraft Outside the SCA: 5. The AMM sends the identity of the priority aircraft 1. ATC and pilots in managed airspace use traditional to ATC and all other HVO aircraft. lost communication procedures. 6. The priority aircraft begins the approach as soon as 2. The AMM inhibits all new operations except for possible, spacing behind the last aircraft to have the lost-communications aircraft, and sets the SCA already started the approach. If the approach status message to no-new-operations. spacing interval becomes too close, the pilot of the 3. The lost-communications aircraft is provided with priority aircraft has the responsibility to request the a normal, non-priority approach sequence via preceding aircraft to perform a missed approach. APDLC if all other entry constraints are met. 4. The lost-communications aircraft descends into the NOTES: SCA at a time appropriate for traditional lost- • The aircraft requesting priority is not assigned an communications procedures.a approach sequence; it is at the pilot’s discretion to begin the approach (based on emergency, a FAR 91.185(c)(3)(i), “When the clearance limit is a checklists, etc). fix from which an approach begins, commence descent and approach as close as possible to the expect-further- not been received, as close as possible to the estimated clearance time if one has been received, or if one has time of arrival…”, FAR/AIM 2005 6 American Institute of Aeronautics and Astronautics • If the requesting aircraft is higher at the IAF than altitude with a normal descent (e.g., 500 foot-per- the approach altitude, the aircraft is not expected to minute descent rate) after crossing the IAF. enter holding but begins the approach at that • The pilot of the priority aircraft must request the altitude with a normal descent (e.g., 500 foot-per- preceding aircraft to perform a missed approach if minute descent rate) after crossing the IAF. the spacing interval becomes too close. • The pilot of the priority aircraft must request the preceding aircraft to perform a missed approach if Other SCA Aircraft: the spacing interval becomes too close. 1. The aircraft symbol on the MFD for the priority (emergency) aircraft would be highlighted. Other SCA Aircraft: 2. Arriving aircraft already on the approach (past the 1. The aircraft symbol on the MFD for the priority IAF) would continue with the approach. If the (emergency) aircraft would be highlighted. emergency aircraft requests that the approach path 2. Arriving aircraft already on the approach (past the be cleared immediately for the emergency, these IAF) would continue with the approach. If the aircraft execute an early missed approach. emergency aircraft requests that the approach path 3. Arrival aircraft holding at the IAF and at the lowest be cleared immediately for the emergency, these altitude would be re-sequenced, if necessary, such aircraft execute an early missed approach. that they would leave the IAF for the approach as 3. The AMM re-sequences aircraft for the approach soon as possible (i.e., the intent is to make a clear retaining their relative order but excluding the approach path for the emergency aircraft). priority aircraft (no re-sequence if the priority 4. For arrival aircraft that are holding at the IAF and aircraft was already on the approach or was the are not at the lowest altitude, they are: first aircraft in holding at an IAF). a. Re-sequenced and given a “Standby”. 4. Onboard systems notify pilots of the new sequence. b. Onboard systems inhibit continuing operations 5. Onboard systems also inhibit SCA operations Pilot Advisor messages (if implemented) until messages (if implemented, e.g., Pilot Advisor the emergency aircraft lands. OPEN 2000) until the priority aircraft has landed. 5. Normal operations are resumed once the priority 6. Once the priority aircraft has landed, normal aircraft has landed. operations resume and the AMM notifies ATC. This procedure is shown in figures 2 through 5, with the Priority Landing Request from a Departing Aircraft example portraying the worst approach sequencing This procedure is for a departing aircraft unable to situation prior to start of this procedure. The start of continue the departure operation and must return for an “Priority Landing from a Departing Aircraft” procedure instrument approach to the airport. is shown in figure 2, with an aircraft on approach, three other aircraft waiting to begin the approach, and a Requesting Aircraft: departing aircraft with the emergency. The approach (The first 5 steps of this procedure are the same as for sequence numbers are shown for these aircraft. Priority Landing Request from Arriving Aircraft.) 1. Announce the emergency and intent over the radio. AAAiiirrrcccrrraaafffttt ###333 2. Select “Emergency Landing” button on the MFD. AAAiiirrrcccrrraaafffttt ###222 3. The AMM inhibits all new SCA operations. AAAiiirrrcccrrraaafffttt ###111 4. The AMM notifies ATC that the SCA status has AAAiiirrrcccrrraaafffttt ###444 AAAiiirrrcccrrraaafffttt been changed to no new operations (NNO). rrreeeqqquuueeessstttiiinnnggg ppprrriiiooorrriiitttyyy 5. The AMM sends the identity of the priority aircraft to ATC and all other HVO aircraft. 6. The priority aircraft proceeds as soon as possible at Figure 2. Departing Aircraft Priority Landing Request the lowest altitude to either IAF to begin the (1 of 4): Initial Condition, #1 on approach approach, and procedurally spaces behind the last aircraft to have started the approach (if any). Figure 3 portrays the situation immediately after the NOTES: departing aircraft makes the priority request. At this • The requesting aircraft is not assigned an approach point, the AMM has re-sequenced and issued new sequence; it is at the pilot’s discretion to begin the sequence numbers STANDBY notifications as approach (based on emergency, checklists, etc). appropriate. Note that the action by the AMM has • If the requesting aircraft is higher at the IAF than affected all of the holding aircraft. the approach altitude, the aircraft is not expected to hold to lose altitude, but begins the approach at that 7 American Institute of Aeronautics and Astronautics Advisor Messages SSSTTTAAANNNDDDBBBYYY AAAiiirrrcccrrraaafffttt ###222 In the event of any system failure that results in the AAAiiirrrcccrrraaafffttt ###111 aircraft reverting to procedural separation, it is envisioned that a Pilot Advisor type functionality will AAAiiirrrcccrrraaafffttt ###333 AAAiiirrrcccrrraaafffttt rrreeeqqquuueeessstttiiinnnggg ppprrriiiooorrriiitttyyy use the SCA status information of participating aircraft state data to assist the pilot in performing the HVO procedure. Although not required, this tool also provides assistance to the pilot in self-separation tasks, Figure 3. Departing Aircraft Priority Landing Request flying within a containment area along the approach (2 of 4): AMM re-sequence, #2 starts approach path, and alerting the pilot to potential conflicts. Interactive communications between aircraft and the AMM were displayed via dynamic messaging windows Figure 4 shows the situation as the second aircraft to the pilot, one of which was the PA (top right of begins its approach. Note that the standard HVO Figure 1). The PA provided procedural cues about the airborne tools, using the AMM sequencing information, integrity of the pilot’s flight path for the purposes of have provided the information to the second aircraft self-spacing and conflict detection and alerting .9 This that it is safe to initiate its approach. Also note that the information is transformed into three types of dynamic first aircraft has landed. messages used by the pilot to make decisions regarding the IFR approach: alert messages (appearance and SSSTTTAAANNNDDDBBBYYY changes in MFD information); AMM sequencing; and PA procedural cues. AAAiiirrrcccrrraaafffttt ###222 AAAiiirrrcccrrraaafffttt ###333 AAAiiirrrcccrrraaafffttt Conclusion rrreeeqqquuueeessstttiiinnnggg ppprrriiiooorrriiitttyyy The SATS HVO concept was expanded to include procedures for off-nominal conditions and situations. Figure 4. Departing Aircraft Priority Landing Request These draft procedures encompass routine enhanced (3 of 4): #2 on approach, #3 ready for approach operations, procedural violations, equipment failure modes, and aircraft emergencies. A range of experts developed these procedures over an eighteen month period, and two of the procedures were down-selected Figure 5 shows the situation after the third aircraft and tested in a simulation experiment. The results from begins its approach, again using its onboard tools to that experiment indicate pilots were able to determine when to begin the approach. accommodate anomalies to normal flight without experiencing higher levels of workload or a reduction in SSSTTTAAANNNDDDBBBYYY situation awareness. Significant further work is required in the HVO off-nominal procedures area. AAAiiirrrcccrrraaafffttt rrreeeqqquuueeessstttiiinnnggg ppprrriiiooorrriiitttyyy AAAiiirrrcccrrraaafffttt ###333 AAAiiirrrcccrrraaafffttt ###222 Operational concepts such as the one proposed in this SATS HVO off-nominal concept document, could enhance the opportunity for point-to-point air taxi or charter operations into smaller airports, providing Figure 5. Departing Aircraft Priority Landing Request greater convenience to the traveling public. These (4 of 4): #3 on approach, Priority ready for approach types of aircraft need avionics to participate that include near-term technologies like ADS-B, communications While the standard HVO airborne tools have provided data link, and appropriate self-separation tools. The the information to the third aircraft to initiate its ability to operate multiple small aircraft, in near all approach, the pilot of the priority aircraft, because of weather conditions, at virtually any small airport, offers the emergency situation, will initiate the approach as a unique opportunity for revolutionary transportation soon as possible. If the approach spacing interval growth and passenger convenience. becomes too close, the pilot of the priority aircraft has the responsibility to request the preceding aircraft to perform a missed approach. Once the priority aircraft has landed, the STANDBY aircraft will be allowed to resume approach operations. 8 American Institute of Aeronautics and Astronautics Acknowledgments The authors wish to thank the Consolidated Information Technology Services (ConITS) members for their outstanding work, in particular James Sturdy, Hazari Syed, Ken Peplow, and John Lapinski. References 1 Holmes, B., “A Vision for 21st Centaury Transportation Alternatives”, NASA, May 2002 2 Abbott, T., Consiglio, M., Baxley, B., Williams, D., Jones, K., and Adams, C., “Small Aircraft Transportation System, Higher Volume Operations Concept”, NASA/TP in preparation, September 2005 3 Baxley, B., Williams, D., Consiglio, M., Adams, C., and Abbott, T., “The SATS HVO Concept and Research”, AIAA 2005-7379, Sept 2005 4 FAR 91.187, Operations under IFR in controlled airspace: Malfunction Reports, FAR/AIM 2005 5 FAR 91.123, Compliance with ATC clearances and instructions, FAR/AIM 2005 6 Abbott, T., Consiglio, M., Baxley, B., Williams, D., and Adams, C., “Small Aircraft Transportation System, Higher Volume Operations Concept: Off- Nominal Operations”, NASA/TM in press, September 2005 7 Abbott, T., Consiglio, M., Williams, D., Jones, K., and Adams, C., “Small Aircraft Transportation System, Higher Volume Operations Concept”, NASA/TP in preparation, September 2005 8 Consiglio, M., Conway, S., and Adams, C., “SATS HVO Procedures for Priority Landings and Mixed VFR/IFR Operations at Non-Towered, Non-Radar Airports”, 24th DASC, October 2005 9 Adams, C., Consiglio, M., and Conway, S., “The Pilot Advisor: Assessing the Need for a Procedural Advisory Tool”, 24th DASC, October 2005 9 American Institute of Aeronautics and Astronautics