Evaluation of CDA as A Standard Terminal Airspace Operation

Transcription

1 Partnership for AiR Transportation Noise and Emission Reduction An FAA/NASA/TC/DOD/EPA-sponsored Center of Excellence Evaluation of CDA as A Standard Terminal Airspace Operation School of Aeronautics & Astronautics Purdue University June 16, th USA/Europe Seminar on ATM R&D, Berlin Germany

2 Motivation Restrictions to field test CDA evaluation single airports Restrict to low traffic high cost safety concerns. Simulation-based evaluation nationwide evaluation normal traffic conditions low cost no safety issue Objective: Evaluate benefits of CDA and understand the trade-offs to achieve conflict-free CDAs in normal traffic conditions. 2

3 Outline 1. Conflict-free CDA Disadvantage of CDA Constrained position shifting 2. Benefits analysis Inbound traffic Simulation at New York Metroplex airports Benefits analysis Trade-off analysis 3

4 Fuel savings by CDA Fuel flow rate increases during the level-offs. The total fuel burn of stepdown approach is higher than CDA. If step-down is replaced by CDA Increased chance of conflict during descent Increased landing interval (from1.8 min to 4 min on average) Decreased airport throughput 4

5 Sequencing Constrained Position Shifting Assume 4D trajectory is available First-come-first-served runway usage principle P ( t, t ) [ p ( t,,, h ), p ( t,,, h ),, p ( t,,, h )] i i i i i i i i i i i i i i i 0 n i i i n n n n P ( t, t ) [ p ( t,,, h ), p ( t,,, h ),, p ( t,,, h )] j j j j j j j j j j j j j j j 0 n j j j n n n n Conflict detection: Aircraft i and Aircraft j are predicted to arrive in a small time window and request landing at the same time 5

6 Sequencing Constrained Position Shifting (CPS) Stagger the landing aircraft by delaying their arrival at the boundary of terminal airspace P ( t t, t t) [ p ( t t,,, h ), p ( t t,,, h ),, p ( t t,,, h )] j j j j j j j j j j j j j j j 0 n j j j n n n n Solution: assign Aircraft j a minimum delay to avoid the conflict, but keep its preferred descent trajectory and speed profile intact. 6

7 Mixed Integer Linear Program Decision variable for aircraft i: Cost function: minimize total delay L k 0 min N L i 1 k 0 w [ w, w,, w ], i {1,2,, N} i i i i 0 1 L i wk 1 w i k {0,1} i i c wkk T Constraints: minimum separations if ([ t, t ] && CD( i, j, t, t )) p q p q 2.5 nm Protected zone Conflict detected if zone overlap then set: w i k i w 1 tq 500 ft or i i i j j j CD( i, j, t p, tq) C( pi ( t, 0, 0, h0 ), p j( t, 0, 0, h0 )) 1000 ft t t p j k j i j 0 if i i i j j j ht ht H C( pi( t, 0, 0, h0 ), p j( t, 0, 0, h0 )) i j 1 if ( ht ht H ) & &( d D) 7

8 Simulation setup Tool: FACET (Future ATM Concept Evaluation Tool, NASA Ames) Simulation mode: flight plans from ASDI data Simulated trajectories according to FACET aircraft performance database Two scenarios: conflict-free step-down and conflict-free CDA Data: ASDI data on 03/01/2005 (full day) Airport: New York Metroplex airports (EWR, JFK, LGA, TEB) Minimum Separation : horizontal = 5 nm (normally 3 nm for terminal airspace, but higher value can accommodate uncertainties in high traffic) vertical = 1000 ft < FL290 = 2000 ft > FL290 8

9 Simulation Flowchart 9

10 Benefit analysis Scenario 1 Unweighted sequencing: no priority among different aircraft types when sequencing the arriving aircraft Scenario 2 Weighted sequencing: Objective=C1* Heavy + C2* Large + C3* Small C1 = 2, C2 = 3, C3 = 1 10

11 Scenario 1: unweighted sequencing solved solved The CPS is able to solve all the conflicts. But CDA incurs more delays than Step-down Delay distribution Majority of the delays are less than 5 min 11

12 en route boundary Terminal airspace climb 2. Airborne holding descent Origin airport 1. ground holding Destination airport Two strategies to absorb the calculated delay 1. Ground holding : Fuel Savings = Fuelburn Step-down - Fuelburn CDA 2. Airborne holding: Fuel Savings = Fuelburn Step-down - Fuelburn CDA - Fuelburn airborne holding 12

13 Savings in the 4 airports of NY metroplex Average savings histogram 13

14 Aircraft size percentages JFK has 652 landing aircraft and TEB has 267. But different aircraft size percentages lead to different average fuel savings. As Heavy and Large aircraft save more fuel, airports with more large and heavy aircraft achieve more significant savings. This suggests that leveraging the weights assigned to different aircraft type will change the delay, consequently the savings as well. 14

15 Scenario 2: weighted sequencing Cost function = c1* Heavy + c2* Large + c3* Small Scenario2: c1 = 2, c2 = 3, c3 = 1 Scenario1: c1 = 1, c2 = 1, c3 = 1 Due to airborne delay Fuel saving increases by about 3 tonnes by prioritizing the arriving sequence in terms of aircraft types. 15

16 Comparison of weighted and unweighted results (a ) delay (b ) Fuel burn for airborne delay Listed aircraft type are Large or Heavy aircraft, Misc. represents unclassified aircraft types. In Figure (a), by changing the weighs, delays are transferred to the unclassified aircraft types. In Figure (b) more fuel is saved. Because large and Heavy aircraft experience less delay, less fuel is burned for airborne delay. 16

17 Discussion Benefit statistics obtained from simulations are conditional upon the following factors: Number of level-offs, more level-offs in reality Altitude where level-offs are executed is critical to fuel burn Fuel flow rate exactness, current database may be not the most up-to-date Local traffic conditions Practical factors, such as wind, weather, interaction between en route traffic and terminal traffic, are not considered in current 17

18 Summary 1. Compared to Step-down, CDA is more difficult to sequence under minimum separation constraint (8.36% more delay). 2. CDA saves fuel and flight time. Simulation results suggests 56 kg/flight and 1 min/flight on average. 3. Fuel savings depends on aircraft types. The larger the aircraft size, the higher the savings. 4. Prioritizing the arriving aircraft in terms of aircraft size leads to increase of savings. 18

19 Backup 1. Advantage vs. disadvantage Figure 1 Extra delay vs. Time saved. Figure 2 Average value of Figure 1 19

20 Backup 2. A rough estimation =~100 kg/min level-off altitude cruise altitude For B757, the fuel flow rate increases as a flight cruises at lower altitude. This is the same to all the other aircraft types. CDA keeps the aircraft cruising as longer as possible and removes the level-off. Suppose a 2-minute level-off is replaced by a 2- minute cruise, then nearly 200kg fuel is saved for B757, which is the benefit due to employing CDA. Let s say CDA causes 1 minute extra delay than Step-down for conflict resolution (extra delay is less than the time for level-off, this has been verified by Fig. 2). That means the B757 has to cruise 1 more minute, which leads to around 60kg fuelburn. Then the total fuel saved is =140 kg. CDA is still beneficial. 20

21 Backup 3. Vertical profile setup Two vertical profiles are simulated Step-down (benchmark) CDA Two level-offs are simulated at most. The number of level-off depends on the distance between TOD and the touchdown. TOD If TOD > 50 mn, two level-offs If TOD > 30 mn, one level-off If TOD < 30 mn, no level-off 21