Assessment of a C-17 Flight Test of an ESTOL Transport Landing Approach for Operational Viability, Pilot Perceptions and Workload, and Passenger Ride Acceptance

Abstract

In order to alleviate future congestion and increase the capacity of the future National Air Transportation System, innovative air vehicles that implement new procedures in the Terminal Radar Approach Control (TRACON) airspace are necessary. With the capability to take-off and land in less than 2,000 feet, and yet cruise efficiently at Mach = 0.8 or higher, the Extreme Short Take-Off and Landing (ESTOL) aircraft is such a vehicle. This aircraft has the potential to fly in and out of crowded hub airports by using the unoccupied airspace and the underutilized runways and tarmac currently unused by the Conventional TakeOff and Landing (CTOL) transports (Reference 1). Additionally, by flying Simultaneous, Non-Interfering (SNI) take-off and approach procedures, the number of arrival and departure streams for a given airport increases while still maintaining safety and potentially reducing the impact of the ground noise footprint on sensitive areas of the community. Due to the unconventional and yet untried nature of the SNI approach (Reference 2), many issues exist that will need to be explored. These issues include: operational feasibility, measurements of the noise propagation to the local community, pilot handling quality and workload assessment, and passenger ride acceptance. On September 10, 2005, a flight test was conducted at Rogers Dry Lake Bed within Edwards Air Force Base of an Air Force Flight Test Center C-17 Globemaster III flying various landing approaches. These approaches varied from the standard 140 knot straight-in landing approach with a three degree glide slope in two ways; one of the approaches was flown like a conventional approach, but was flown at a steeper glide path angle of 5.5 degrees and airspeed between 125 and 130 knots. The other approach was flown with the aircraft remaining at a higher altitude of 3,000 ft Absolute Ground Level (AGL) until the aircraft was above the landing runway threshold. The aircraft then made a spiraling, descending 360 degree left hand turn with a descent angle of 5.5 degrees, a turn radius of about ¾ of a mile, a bank angle of about 20 degrees, and an overall flight speed of about 120 knots. At the end of the 360 degree turn the aircraft was back to the threshold, on the runway heading angle, and at the appropriate decision height of 250 ft (Figure 1). Although the C-17 did not fly as slow in the terminal airspace as the future ESTOL aircraft (65 – 85 knots), these landing approaches were representative of the ESTOL SNI approach. Additionally, all of these approaches were flown under Visual Flight Rules, with the understanding that implementation for a future ESTOL would require an all-weather capability comparable to current CTOL traffic. This paper addresses the operational issues, the handling quality and workload, and the passenger ride acceptance examined during this test. Other papers examine in more detail the community noise reduction potential from the SNI approach (Reference 3), the noise measurement techniques used during this test (Reference 4), and the mathematical modeling of the flight track (Reference 5). This paper will discuss the initial work conducted in the NASA Dryden C-17 simulator to program the Flight Management Computer (FMC) to fly the approach on autopilot, and the changes that became necessary during the actual flight when the crosswinds were higher than expected and the autopilot could not maintain the ground track. This