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7 2 REVIEW OF SMALL AIRCRAFT PERFORMANCE LITERATURE This section presents a literature review to support the objectives of ACRP Project 03-54 â Small Aircraft Runway Length Analysis Tool. We surveyed appropriate guidance, available research, other information on aircraft runway performance certification, aircraft operations, technical papers on aircraft runway performance prediction. We reviewed documents of runway length data applicable to small aircraft. Our review included: technical journal papers, aircraft performance textbooks, technical reports produced by NASA and FAA, government regulations in the certification and operation of small aircraft, and aircraft manufacturer performance data. The literature review provides insights into extending the performance analysis for small aircraft with limited aircraft performance data. In the study, we found that many pilot operating handbook manuals for small aircraft do not have takeoff runway performance corrections for runway gradient or wet runway conditions. Some of the technical papers reviewed and published performance data for similar aircraft provide information to address gaps in the data collection in Section 4 of the report. The scope of the SARLAT includes aircraft certified under the Light Sport Aircraft (LSA) category, 14 CFR Part 23 standard and commuter categories, and 14 CFR Part 25 (corporate jets). Table 1 shows five types of small aircraft selected in this study. To guide our review of relevant runway length data information applicable to small aircraft, we analyze the United States Aircraft Registry to identify small representative aircraft with maximum takeoff weight at or below 20,200 lb. Appendix A presents tables with representative aircraft in each category presented in Table 1. 2.1 JOURNAL PAPERS ON THE RUNWAY LENGTH PERFORMANCE OF SMALL AIRCRAFT We conducted a review of technical papers on aircraft runway performance prediction applicable to small aircraft. The journal papers provide insight into aircraft takeoff's physical laws and landing using closed-form equations or more complex simulation-based approaches. The following paragraphs summarize the review of the documents. Powers et al. (1) proposed a comprehensive approach to predict takeoff and landing performance in the preliminary aircraft design process. Chandrasekharan et al. (2) developed a method to evaluate ground roll and airborne takeoff distances. The analysis shows the effect of small changes in speed on takeoff distance for low power-to-weight ratio aircraft. Anderson (3) developed an aircraft thrust model that varies with speed to predict takeoff distance. The analysis presents equations to model reciprocating, turboprop, and turbofan engines. Spencer et al. (4) presented a Bayesian modeling framework to predict takeoff distance using hierarchical Bayesian regression. To correct takeoff distance for the influences of non-standard conditions, Lush et al. (5) provides fundamental equations. Lush's work has been updated more recently by Kim et al. (6) with a series of simulation models that include aircraft aerodynamics, propulsion, landing gear dynamics, and pilot interactions. Kim et al. (6) developed the simulation model to study turboprop aircraft's takeoff and landing performance. Orleans et al. (7) presented a modeling and simulation method to standardize takeoff performance data for a wide range of conditions, including air temperature, pressure altitude, wind, runway slope, and aircraft gross weight. Daidzic et al. (8) presents a realistic operational landing and stopping performance analysis model on contaminated runways in adverse conditions. This paper
8 develops correction factors for landing distance calculations. The model considers scenarios, such as hydroplaning, wind, the speed-dependent rolling-friction coefficient, and variations in the piloting technique. The simulation analysis states that a 15% FAA mandated wet runway correction factor may not be sufficient for some combination of adverse effects. Aircraft takeoff and landing performance are affected by friction between the aircraft tires and the runway. Wahi, et al. (9) proposed prediction equations, including seven dimensionless groups to define tire-runway interface friction. Jones et al. (10) calculated the frictional force using a model and principles of tribology. To improve the correlation between friction coefficients and braking coefficients, Cerezo et al. (11) present a friction model using the Engineering Science Data Unit (ESDU) that considers the aircraft's characteristics and the runway contaminants. Initial validation tests show promising results to extend the model to other aircraft. Jiao et al. (12) proposed an Anti- lock Braking System (ABS) control method regulating aircraft wheels to keep tiredârunway friction around its maximum value. Computer software simulations validated this approach, and it can be applied to simulate aircraft operating in diverse runway conditions. Several of the papers reviewed address the impact of pilot technique on aircraft takeoff and landing performance. Advani et al. (13) conducted a pilot-in-the-loop simulated study to understand pilots' visual cues during landing and flare. To reveal the processing flow of visual information, Sakamoto et al. (14) developed a Neural Network (NN) to study the pilotâs visual cues during landing. Visual cues such as the horizon, a runway shape, and runway marker information obtained from recorded flight data. Mori et al. (15) developed a stochastic switched linear regression to construct an aircraft-pilot model from simulated landings using Boeing 747 pilots under different wind conditions. Using the expectation-maximization algorithm, this model attempts to replicate the pilotâs control strategy and decision-making during landing. Mori et al. (16) present a separate model for landings in crosswind conditions. By observing advanced student pilots in the cockpit, Takahashi et al. (17) estimated pilot-induced deviations from nominal landing speeds. The study found actual touchdown speeds higher than the prescribed touchdown speeds, increasing the probability of a runway overrun. Wood et al. (18) developed a model of the landing sequence of transport aircraft (i.e., Airbus A320) and show that slight deviations in approach and landing procedures and reduced braking effectiveness add significantly to field length requirements. The analysis considers that the 115% factored landing distance prescribed by SAFO 06012 may not adequately cover compounding errors associated with landing events. Callahan (2016) presents an in-depth analysis of six wet runway landing overrun events. The study shows that the wheel braking friction coefficient achieved during each accident was substantially less than the accepted braking friction coefficient in certification models (i.e., 14 CFR Part 25.109) and less than wet pavement landing advisory data in the Airplane Flight Manual. Addressing this concern, the FAA has issued several Safety Alerts warning operators that âadvisory data for wet runway landings may not provide a safe stopping margin, especially in Moderate or Heavy Rain (FAA 2019a)â. 2.2 GOVERNMENT REGULATION AND FAA ADVISORY DOCUMENTS We conducted a review of technical documents produced by FAA and the European Union Aviation Safety Agency (EASA) on aircraft runway performance certification and aircraft operational requirements. Documents reviewed include: 1) Federal regulations to certify small aircraft (14 CFR Parts 23 and 25),
9 2) FAA advisory circulars with guidance on training and methods to assess landing performance (AC 120-62 and AC 25-32), and 3) FAA Safety Alerts to pilots and aircraft operators of runway condition reporting changes for contaminated runways with wet standing water, slush, snow, or wet ice. Many of the documents reviewed provide guidance about takeoff and landing operations. Airbus Flight Operations Briefing (19) provides information on aircraft takeoff speeds and human factors associated with takeoff speed calculations. Such guidance applies to transport-type aircraft operations but is also relevant in the operation of very light jets. The FAA Advisory Circular AC- 120-62 (20) is a training aid to help pilots and carriers improve safety during the takeoff phase of flight. FAA AC-91-79A (21) provides guidance to identify and mitigate risks associated with runway overruns. FAA AC-25-32 (22) contains guidance and methods to develop landing performance data for time of arrival assessment to identify and mitigate risks associated with runway overruns. The Federal Aviation Administration Safety Alert SAFO 16008 (23) provides guidance to develop standard operating procedures to reduce the risk of runway excursions during takeoff. The Federal Aviation Administration Safety Alert SAFO 16009 (24) notifies operators and pilots of changes in runway condition reporting for non-dry conditions. The United States Federal Regulations, Title 14, Chapter 1, Subchapter C, Part 23 provide the design requirements for aircraft takeoff performance (23.2115), climb requirements (23.2120), and landing distances for small aircraft (23.2130). Part 23.2105 provides guidance on the performance data produced during the certification of small aircraft. Most of the aircraft included in SARLAT are certified under 14 CFR Part 23 standards. The United States Federal Regulations, Title 14, Chapter 1, Subchapter C, Part 25 (30) provide the certification criteria for aircraft takeoff speeds (25.109), accelerate-stop distances (25.111) and takeoff path (25.113) and takeoff distance and takeoff run criteria (25.115) (29). We also reviewed the States Title 14 Code of Federal Regulations Part 135 (sections 135.361 and 135.377) provided guidance on the operating requirements for commuter and on-demand operations and rules (31- 33). The basis of landing distance correction factors contained in SARLAT are derived from the 14 CFR Part 23 and Part 25 regulations. The Federal Aviation Administration Aviation Rulemaking Advisory Committee: FTHWG Task 9 (25) proposed changes to 14 CFR Part 25 to better reflect the physics of stopping aircraft on wet runways. The proposed standard (14 CFR Part 25.126) accounts for wet grooved and porous friction course techniques or materials that increase wet runway wheel braking. The new standard would increase the level of protection of landing operations at higher altitudes and high temperatures compared to the existing regulations contained in 25.125 (25). At the publication of this report, the new standard has not been adopted, and should not be considered FAA policy unless and until a final rule is published. The Federal Aviation Administration, Safety Alert SAFO 19001 (26) provides recommendations for operators to develop standard operating procedures to ensure sufficient landing distance according to FAA AC 150/5200-30. The Federal Aviation Administration, Safety Alert SAFO 19003 (27) informs pilots that advisory data for wet runways may not provide safe margins for moderate and heavy rain conditions. The Flight Safety Foundation ALAR Briefing 8.3 (28) developed guidance with basic explanations of the factors affecting landing distances. The National Business Aircraft Association (NBAA) developed Pilotâs Runway Condition Assessment
10 Quick Reference Cards (29) with runway braking assessment criteria and time of arrival landing distance assessment. 2.3 OTHER DOCUMENTS We conducted a review of additional technical documents to understand the physics and modeling process of predicting aircraft runway performance. Aselin (34) and Fillipone (35) provide general discussion and principles of aircraft performance. Gallaway et al. (37), Horne and Dreher (38), Horne et al. (39), and provide additional background on the effects of rainfall, pavement cross section, and pavement texture on pavement water depth and friction. 2.4 AIRCRAFT MANUFACTURER DOCUMENTS We conducted a review of technical documents produced by aircraft manufacturers to a) understand the presentation of small aircraft runway performance, b) verify the extent of the data available, and c) identify the parameters considered in the takeoff and landing distance data presented to pilots. References (40-147) present takeoff and landing runway length performance for aircraft used in the development of the SARLAT. 1) Pilot Operating Handbook (POH) 2) Airplane Flight Manual (AFM), and 3) Aircraft Flight Planning Guides (FPG) In general, pilot operating handbooks and airplane flight manuals present information in a single document. For some aircraft, the POH and AFM maybe two separate volumes. POH/AFM documents contain the most extensive set of takeoff and landing field data. For a corporate jet aircraft certified under 14 CFR Part 25, the POH and AFM information is comprehensive and may include hundreds of performance tables. For example, POH/AFM data provided by Cessna for the 560 XLS includes takeoff performance tables for 12 weights, two flap settings, five wind conditions, 12 pressure altitudes, 12 temperature profiles, and two runway conditions (dry and wet). Supplemental performance data for the Cessna 560 XLS includes takeoff performance for gravel runways. Figure 3 shows sample takeoff field length tables included in the Cessna Citation 560 XLS Airplane Flight Manual. Figure 4 shows a landing field length table for the Cessna 560 XLS. Runway length performance data for large turboprops (with more than ten seats) and jet-powered aircraft include takeoff and landing performance information for operations in wet and contaminated runway conditions. There are two variations in the data format presented in POH and AFM manuals: 1) performance tables and 2) performance nomographs. Figure 5 shows the takeoff distance nomograph for the Columbia 400 aircraft. Figure 6 shows the landing distance nomograph for the Columbia 400 aircraft. Many complex turboprops and jet-powered aircraft manufacturers include tables and nomographs in the POH/AFM manuals. Nomographs present correction factors for wind and runway gradient. Aircraft Flight Planning guides (FPG) summarize the information presented in POH/AFM documents with the most relevant airport operating conditions. FPG documents contain dozens of takeoffs and landing distance data tables for different pressure levels, temperature, and flap settings. Figure 7 shows the 14 CFR Part 25 takeoff field length data for the Cessna Citation Jet CJ3 (Model C525B). Figure 8 shows the 14 CFR Part 25 uncorrected landing performance for the Cessna Citation Jet CJ3. The data contained in the FPG shows the climb weight temperature limits
11 for every airport elevation and weight combination. FPG data includes climb weight temperature limits for turbofan and turboprop aircraft. Climb weight and temperature limitations are essential in the development of the SARLAT. The review of the aircraft performance literature provided insight on the best practices to report runway length for airport planning and design. To make the SARLAT flexible to airport planners and designers, we decided to report multiple runway length requirements for each airport design condition. For example, SARLAT reports dry and wet takeoff and landing distances for each design condition. SARLAT also reports landing distances corrected for CFR 14 Part 135 operations (both eligible on-demand and regular Part 135 operations). The inclusion of multiple criteria in reporting runway length should help airport designers to estimate runway length distances according to criterial used for Federally funded airport projects, where dry takeoff conditions and wet landing conditions are the acceptable design criteria. The inclusion of 14 CFR Part 135 landing distance criteria provides useful information to airport designers about the runway length operational requirements for on-demand operations. The following Section of the report provides insight on how the runway length distance information was converted into a database and integrated into SARLAT.
12 Figure 3: Sample Takeoff Distance to Clear a 35-foot Obstacle for the Cessna Citation 560 XLS Aircraft. Dry Runway Condition. Flaps 7 Degrees, 2000 feet Pressure Altitude, Anti- Ice Off, Zero Runway Gradient. Source: Cessna Aircraft Company.
13 Figure 4: Sample Uncorrected Landing Distance Table for the Cessna Citation 560 XLS Aircraft. Dry Runway Condition. Flaps 35 Degrees, 2000 feet Pressure Altitude, Anti-Ice Off, Zero Runway Gradient. Source: Cessna Aircraft Company.
14 Figure 5: Takeoff Distance Nomograph for the Columbia 400 Aircraft. Dry and Paved Runway. Flaps 12 Degrees. Ground Roll and 50-foot Obstacle Distances. Source: Columbia Aircraft Manufacturing Corporation. Figure 6: Landing Distance Nomograph for the Columbia 400 Aircraft. Dry and Paved Runway. Flaps 40 Degrees. Ground Roll and 50-foot Obstacle Distances. Source: Columbia Aircraft Manufacturing Corporation.
15 Figure 7: Sample Takeoff Field Length Table in the Cessna Citation Jet 3Flight Planning Guide. Dry Runway, 2,000-foot Elevation, Flaps 15 Degrees, 35-foot Screen Height, Zero Wind, Anti-ice Off, and Cabin Bleed Air On. Source: Cessna Aircraft Company. Figure 8: Sample Landing Field Length Table in Cessna Citation Jet 3 Flight Planning Guide. Dry Runway, Flaps 35 Degrees, 50-foot Screen Height, Zero Wind, Anti-ice Off, and Cabin Bleed Air On. Source: Cessna Aircraft Company.
