Trajectory-Based Operations (TBO) - Joint Planning and ...

Trajectory-Based Operations (TBO)
Study Team Report
N72MD climbs to FL250, and in doing so must slow to 160-knot climb speed. Until N72MD reaches
FL250 and once again stabilizes at cruise speed, the ETA being transmitted as part of the ADS-B nearterm
intent message will continue to change and be inaccurate. The ATM system anticipates this and
opens the TBO conformance window to allow the associated uncertainty in time of arrival at VERNL.
This addition of uncertainty relative to time is then used by the ANSP TBO evaluation service to scan
for any downstream conflicts.
Twenty nm prior to reaching VERNL, the ANSP detects a conflict that indicates that N72MD will
conflict with a Sunset Boeing 737 going into SLC. The ANSP’s TBO evaluation offers the controller a
few options, one of which is to slow N72MD to 200 knots until passing VERNL at 17 minutes past the
hour. That will put N72MD behind the Sunset Boeing 737, and in front of the next aircraft 15 miles
away and inbound to VERNAL, providing sufficient separation. The flight object information for
N72MD tells the controller that the aircraft is equipped with appropriate capability from the navigation
system, but without auto-throttles. Consequently, the controller can only expect +/- one minute of
conformance performance from the pilot. The controller asks the N72MD pilot if she can slow to and
maintain 200 knots ground speed, and pilot answers in the affirmative. The pilot slows to a 200 knot
ground speed on her navigation display and then holds the airspeed that represents the ground speed.
The controller issues a clearance to do so and pilot adjusts speed until the GPS navigation unit is
showing 200 knots ground speed. The controller informs the pilot that she needs to cross VERNL at 17
minutes past the hour. Because the pilot must manually fly the time, the pilot programs this time into
the EFB for VERNL. The EFB provides a “how-am-I-doing” status indicator, showing the current
ETA to VERNL at present speed, and an indication of target speed and ETA the pilot needs to fly to
comply with the ETA. The pilot adjusts speed to match it with the desired speed and time at VERNL.
Had the controller requested an increase in speed in excess of five knots, the pilot would have known
she could not comply and would have notified the controller. The controller would have then chosen
another option and negotiated that with the pilot via voice communications. This is an example where
the pilot is able to meet the RTP through the use of simple aids in the cockpit, not requiring a FMS.
Voice is used because of the lack of data link.
Passing VERNL, the satellite weather display shows that the storm system is moving faster than
forecast and there will be heavy snow and moderate turbulence west of BZN at the time of arrival. The
arrival for the RWY 12 ILS approach goes through this area. The pilot requests the RNP 0.3 GLS
approach to RWY 30, an overlay approach, and the ANSP approves. This will keep the pilot out of the
weather during approach and missed approach if necessary. The pilot selects this approach in the
navigation system avionics.
Twenty miles prior to N72MD reaching the RWY 30 RNP feeder fix, the ANSP automation
determines that a regional carrier flight to BZN will be in conflict, and the controller verbally instructs
N72MD to slow to 160 knots and to descend to 14,000 feet. The pilot reduces power to comply.
15.5 Bozeman Arrival/Approach and Landing
The pilot obtains the latest weather and airport information. Weather at the destination ETA is forecast
to be 3,000-foot overcast and three miles visibility in blowing snow. Wind is 300 o at 15 knots, gusts
reported as high as 35 knots. Pilot reports indicate moderate turbulence from 10,000 feet all the way to
the surface. Runway braking action is reported as fair by a Sunset Air 737-900. The pilot selects the
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