Frequency as airlines means to accommodate growth, and implications on e-taxiing Terence Fan terencefan@smu.edu.sg
Past: bigger aircraft was better Before the advent of revenue management and liberal air service agreements, larger aircraft boosts airlines profit with their lower per-seat costs Source: https://qph.ec.quoracdn.net/main-qimg-ccfb5658c0f2e248b9e3a5add2f284-c; http://aero.stanford.edu/bwbfiles/largeacopt.html 1
Now: better revenue management lets airlines price-discriminate passengers, e.g., LHR-NRT-LHR on BA: Source: Fan & Leung, Journal of Revenue & Pricing Management 2
lets airlines right-size capacity Based on the profile of airfare obtained ($ and demand), airlines reduce their aircraft size in the long run to capture higheryielding traffic, and to increase frequency to capture growth Operating surplus per flight, USD From Fan, Journal of Transportation Research Forum Profit maximizes at small aircraft size with price disparity & proper fare fencing 3
iberal policy + budget carriers more flights That was the case for non-stop flights between UK & Ireland, and continental Europe in the early 00 s Cumulative average growth of 6%/year Source: Fan, Journal of Transport Geography 4
Frequency growth at Changi (1) Disproportionate use of (smaller) narrow-bodies to accommodate growth on existing routes ~ 1-2 hrs Weekly frequencies for 1-2.9 block hrs, Official Airline Guide SIN-Penang SIN-Denpasar SIN-Bangkok 0 0 0 180 180 180 7 83 160 160 160 107 140 140 140 1 1 1 100 80 95 100 80 35 100 80 112 60 60 70 60 62 40 40 40 18 24 0 14 05 15 0 7 05 15 0 05 15 Narrobody Widebody-ex747380 Narrobody Widebody-ex747380 Narrobody Widebody-747380 Widebody-ex747380 5
Frequency growth at Changi (2) Disproportionate use of (smaller) narrow-bodies to accommodate growth even long routes of ~ 4 hrs Weekly frequencies for 3-5.9 block hours, Official Airline Guide SIN-Taipei SIN-Manila SIN-Hong Kong 140 140 140 7 105 1 1 1 100 100 35 100 28 80 60 80 60 79 80 60 49 40 24 18 29 40 30 40 21 35 0 7 05 15 0 12 05 15 0 05 15 Narrobody Widebody-ex747380 Narrobody Widebody-ex747380 Narrobody Widebody-747380 Widebody-ex747380 6
Frequency growth at Changi (3) Disproportionate use of narrow-bodies to open new routes 15 weekly frequencies for some cities not served from SIN in 05, Official Airline Guide 40 35 37 30 25 19 15 10 14 15 5 0 Krabi Hangzhou Tiruchirappalli Bandung 7
As no. of flights increase, delays soar Sample no. of flights scheduled per hour at New York LaGuardia 1 100 80 Nov, 00 Aug, 01 81 flights/hour 60 40 A small increase in frequency at a busy airport can lead to huge delays Hours of the day (e.g., 7 = 0700-0759) 0 5 7 9 11 13 15 17 19 21 23 1 3 axiing delay per departing flight (mins), Aug 01 Taxiing delay per departing flight (mins), Nov 00 90 80 70 60 50 40 30 10 0 5 7 9 11 13 15 17 19 21 23 1 90 80 70 60 50 40 30 10 0 ASQP actual OAG+GA OAGcancel+GA OAGcancel+GA 5 7 9 11 13 15 17 19 21 23 1 ASQP actual OAG+GA 8
...and simulation is realistic Sample flight delays at New York LaGuardia without slot control Taxi delay based on scheduled departure time (minutes/flight); Delay (actual wheels-up time actual pushback time) 15 mins of standard taxiing out time 90 80 70 60 50 40 30 10 OAG + GA 3-Nov-00 8-Nov-00 13-Nov-00 OAG + GA - Cancel Simulated Actual fineweather days Simulated 0 5 7 9 11 13 15 17 19 21 23 Hours of the day (e.g., 7 = 0700-0759) 9
Situation for Asia & beyond Airport responses Stop-gap slot control* Longer-term capacity expansions (more in Asia) Airline responses: Schedule creep/padding ($$$, see next) Potentially, more efficient taxiing 10 * See, e.g., Fan & Odoni, Journal of Air Traffic Control Quarterly for variations in practice
Schedule creep Schedule creep a fact of life Refers to the gradual increase in scheduled block times for the same city-pairs over the years Route Past (year) 15 (hr:min) ORD (Chicago) SFO 4:25 ( 05) 4:43 ORD LHR 7:49 ( 10) 8:02 MDW (Chicago) MSP 1:23 ( 05) 1:27 LGA (NYC) ORD 2:25 ( 96) 2:55 LGA IAH (Houston) 2:30 ( 73) 4:10 Overall, increase in block times: 18% worldwide in 1999-09 4% to 6% worldwide in 05-15 E-taxiing can stop schedule creep Source: http://www.chicagotribune.com/news/columnists/ct-airline-flight-times-getting-around-met-17-151214-column.html ; http://www.telegraph.co.uk/travel/news/why-flight-times-are-getting-longer-fuel-flying-slower/; http://www.businesstravelnews.com/aviation/schedule-creep-demand-drop-redefine-air-delays/12243 11
Schedule padding also a fact of life Schedule padding Scheduling longer-than-necessary scheduled block times, with the potential aim of improving on-time performance Southwest s example illustrates the fine line among shorter scheduled block times, no. of aircraft required & on-time performance Tightened schedule: removed equivalent of 16 aeroplanes (out of 680) 80.2% on-time performance Rank: 7 th of 16 airlines 71.1% on-time performance Rank: Tied for last 12 months before Aug 13 12 months after E-taxiing can help reduce schedule padding needed Note: On-time defined by percent of flights arriving within 14:59 minutes of schedule Source: https://www.dallasnews.com/business/airlines/14/10/27/schedule-adjustments-put-southwest-airlines-on-time-performance-back-on-course 12
Delay simulation principle Based on the airport as a single-server, with a queue of departing and arriving aircraft Queue of departing and arriving aircraft Airport Departed or arrived aircraft It pays to be at the head of the queue, and e-taxiing helps airlines get there Legend: departing and arriving aircraft 13
Delays & turnarounds have big impact Longer turnarounds, as necessitated by increased airport-related delays, require more aircraft to operate the same schedule 06 schedule with 2773 daily turnarounds Number of aircraft needed 461 Actual schedule 479 18 more 737s needed! Minutes saved from each turnaround can save a lot of $$$ Add 5 mins to each turnaround 14 Source: http://www.nytimes.com/06/11/14/business/14boarding.html
same with slightly longer engine starts Longer engine start-up time contributes to longer turnaround times apparently a big turn-off PW1100G-JM engines on A3neos require longer start-up times, from 150 seconds to 350 seconds in hot conditions (2-3 mins extra) Qatar Airways refused to take an aircraft before fixes were installed to the PW1100G engines The longer startup time required for cooling of the PW1100G engines is making it difficult for IndiGo to maintain flight schedules The extra warm-up time creates problems for Lufthansa because of a shortage of space to taxi at Frankfurt airport 15 Sources: http://aviationweek.com/commercial-aviation/qatar-airways-cancels-more-a3neo-orders; http://aviationweek.com/commercial-aviation/indigo-impacted-a3neostartup-time-issues ; http://in.reuters.com/article/interglobe-results-idinkcn10c28z; http://www.reuters.com/article/us-pratt-airbus-a-iduskcn0vz1ke
Taxiing takes up 19% of block hour Based on A3 fleet 12-month average till Apr 12 1.8 hours/flight average gate-to-gate ( block ) time mins/flight spent on taxiing 8.9 hours/day daily utilisation 19% of gate-to-gate time actually on taxiing! 3-min reduction in taxi time per flight translates into a 15-min reduction in block time every day, or ~2% reduction in scheduled crew expenses! Source: <http://www.airbus.com/fileadmin/media_gallery/files/brochures_publications/fast_magazine/fast51.pdf> p.8, accessed 10 May 17 16
Shorter turnarounds increase profits While aircraft taxiing delays are difficult to obtain, short aircraft turnaround times have been associated with increased profitability Note: Ground time of over 3 hours ignored; only narrow-bodies included; using FlightRadar24 data Source: https://airinsight.com/17/05/08/correlation-airline-ground-time-profits/ 17
E-taxiing can reduce turnaround time Source: Airport Cooperative Research Program Report 158: Deriving Benefits from Alternative Aircraft-Taxi Systems, Transportation Research Board, 16, p.2, p.9, p.16, p.17 Among various electric aircraft taxiing technologies, Dispatch taxiing (e.g., using existing pushback tractor) Semi-robotic dispatch taxiing (e.g., using a hybrid external tractor for taxiing) Nose-wheel-mounted electric aircraft taxiing systems Main landing gear electric aircraft taxiing systems Replacement of the APU with on-board taxi jet engine those without the need to attach and detach external systems can save up to 2 minutes in push-back procedures 18
Plus, e-taxiing saves fuel (1) Up to 10% of fuel burnt on ground Source: <http://www.airbus.com/fileadmin/media_gallery/files/brochures_publications/fast_magazine/fast51.pdf> p.6, p.8, accessed 10 May 17 19
Plus, e-taxiing saves fuel (2) Without the main engine thrust, e-taxiing reduces fuel burn and associated emissions during taxiing Source: <http://www.airbus.com/fileadmin/media_gallery/files/brochures_publications/fast_magazine/fast51.pdf> p.9, accessed 10 May 17
Conclusion As passenger air transport demand increases, capacity-related delays will soar, schedule padding and creep will be a fact of life seconds shaved off the usual taxiing process or turnarounds matter! efficient e-taxiing can give one airline an important advantage, leading to increased profits, against others To improve airline and airport planning: need better operational data for analysis 21
Summary Economics encourages airlines to use frequency to accommodate growth In the world of increasing flight delays, The U.S. experience (no slot control) shows that being able to get to head of take-off/landing queues can save a lot of time & costs Experience from Asia (with slot control) shows relentless rise in frequency, bearing some similarity to the U.S. experience E-taxiing Better able to place an airline s aeroplane at head of takeoff queues to save time & cost 22