Characteristics of Aircraft As They Affect Airports ∗
3.2 THE INFLUENCE OF AIRCRAFT DESIGN ON RUNWAY LENGTH
All commercial aircraft design has its roots in the development of propulsion systems and the application of aerodynamic theory. In parallel with advances in type and effi-ciency of aircraft power plants (Figure 3.2) have come increases in absolute power.
Aerodynamic advances have been made allowing the full use of propulsive improve-ments. In particular, speed capability has increased (Figure 3.3). After the introduction of the supersonic Concorde into commercial service in 1976, it became clear that supersonic flight was not commercially viable. This meant that the development of air transport aircraft for the period 1970– 2010 was concentrated on top cruising speeds within the range of 0.9–0.85 Mach. The combination of improvements in speed and absolute size has resulted in the upward trend in seat mile per hour productivity within the envelope shown in Figure 3.4. Combined with improvements in engine fuel effi-ciency and other economies of scale, these factors have generated a significant long-term reduction in real costs per passenger kilometer and tonne kilometer.
In the days of the DC-3, a wing design that gave economical cruising flight also allowed a reasonably short field length, because the aircraft could sustain flight at quite a low speed.
∗Between short- and long-haul designs, the proportion of empty to maximum weight varies from 63 to 49%, while the proportion of fuel to maximum weight varies from 20 to 42%, though some of this difference is due to the smaller size of the shorter range aircraft.
Figure 3.2 Trends in ratios of takeoff thrust to bare engine weight.
For level flight,
lift (= weight) α ρ V2SCL (3.1)
where
ρ = air density
V = forward speed of the aircraft S = area of the wing
CL= coefficient of lift (nondimensional); approximately proportional to the angle of attack of the wing
or
W
S ∝ ρV2CL
where
W = Aircraft weight W/S = wing loading
Thus, at a given value of CL, higher speeds allow a smaller wing, and hence lower weight and drag. Unfortunately, high-speed wings tend to have a lower maximum value of CL (at which the wing stalls and loses lift abruptly), so the ratio of cruise speed to stall speed is naturally lower, and this leads to much higher takeoff and approach speeds. Even if it were possible to have infinitely long runways, high approach speeds would be unacceptable because of problems associated with landing gear design, pilot judgment, airspace requirements, and air traffic control. Hence, high-lift devices are employed to reduce the stalling speed by increasing the effective wing area and by increasing the maximum value of CL.
19100
100
200
300
400
500
600
700 1920193019401950
Cruising speed (mph)
Year of service entry
Trimotor
DC–3L–649 L–1049 F27 Islander
Piston Turboprop
CitationCaravelle
Cornet
707–120
B80 747SP A300B A300 B737–500
B737– 600, 700, 800, 900 B737–300
A320A330/340
A380 B777400ERB747–400
747–100 Electra DHC–8 1960197019801990200020102020
Trendinfield perform
ance
Trendinfieldperform ance
Figure3.3Trendsincruisingspeedsofsubsonicpassengertransportaircraft.
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19100
50
100
150
200
250
300
350
400 0
50100
150
200
250
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350
400 1920193019401950
Seat miles per hour ( 3 ×10 )
Year of service entry
TrimotorDC–3
L–1049
707–120 Caravelle F27DHC–7
Concorde DC–9–50
DC–10–40 A300B
B747–100
A380 B747–400 ER B777–300 B777–200 A340–200 A330–200 B737–400B737–900 B737–700
B747–400 737–100 L–649 1960197019801990200020102020
nv E op el o e pf d ro
ctu
ivity B747–800 B787 Figure3.4Trendsinproductivityintermsofpassengerseatmilesperhour.
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A measure of the scale of penalty involved in compromises between aircraft design and runway length provision can be gained from the estimate that a twin turbofan aircraft designed for a 1000-nautical-mi (1850-km) range operating from a 6000-ft (1830-m) runway is penalized by approximately 23%, compared with an aircraft of similar specification designed to unlimited field length.∗ The penalty arises from a combination of increased wing area, the high-lift devices, extra thrust for takeoff, and extra fuel. The high-lift devices have more influence on the landing field length, and the extra thrust is of more value on takeoff. The increase in wing area provides a lower minimum flying speed, regardless of the amount of flap or slat being used, thus reducing both the takeoff and landing field length requirements. The takeoff usually leads to the greater field requirement, except with aircraft designed exclusively for short stage lengths; in the latter case, the maximum landing weight is usually very similar to the maximum takeoff weight.
Figures 3.5 and 3.6 illustrate the tendencies for aircraft designed to different field lengths to use different power-to-weight ratios and wing loadings. From the range of types of powerplant and categories of operation selected, it can be seen that propeller-driven aircraft achieve adequate field performance without increased thrust-to-weight ratio because of their use of relatively low wing loadings and the high static efficiency of their low disc loading.†Similarly, the helicopter achieves vertical takeoff with the same installed power as a light conventional aircraft of the same weight. On the other hand, pure jet aircraft require much higher installed thrust if their takeoff field length is to be reduced substantially, with commensurate reductions in wing loading, or more powerful flaps if the landing field length is to be similarly reduced.
Figure 3.5 Effect of power-to-weight ratio on field length.
∗In this case, “productivity” is defined as scat miles per hour per pound all-up-weight (AUW).
†Disc loading is the thrust developed by a fan per unit frontal swept area. Static efficiency is inversely proportional to disc loading.
Figure 3.6 Effect of wing loading on field length.
Requirements of Current Aircraft Types
In the previous discussion, we have attempted to indicate the interactions that take place in aircraft design between the field length and other factors. There are fundamentally three different types of interaction. With long-range aircraft, a long takeoff is dictated by the large fuel requirements. Medium- and short-range aircraft for trunk and local airline operation have to compromise their cruise performance with the need to use a large number of medium-length fields. Aircraft for feeder and general aviation roles normally operate over short ranges where cruise speed is not essential; thus, a low wing loading is permissible, and they can operate with short field lengths without a significant design penalty.
Tables 3.1a, b, and c present the characteristics of a wide range of present-day aircraft. The variation in Federal Air Regulation (FAR) Landing and Takeoff Distances illustrates the preceding discussion. It is important to realize that the speeds, field lengths, weights, and maximum stage lengths given are all for quite specific conditions of operation, which are held constant over the range of aircraft types for ease of comparison. Cases of variation from these specific conditions having an important effect on the field length requirements are discussed in detail below.
Field Length Regulations— Air Transport Aircraft
The field lengths listed in Table 3.1 are determined not only on the basis of the aircraft’s design capability but also by the safety regulations made by the responsible bodies in the individual member countries of the ICAO. In the United States, the regulating authority is the FAA. The ICAO issues worldwide advisories that are similar in philosophy and content to the FAA regulations. Field length requirements for a given class of aircraft are based on the performance of several critical and rigidly specified operations.
Table3.1aAircraftCharacteristicsofAirCarriers:Powerplant,Dimensions,andNumberofPassengers Dimensions(m)Number AircraftTypePowerplantSpanLengthHeight(max)TurningRadiusaWheelBaseTrackPassengers(A Short/MediumHaul B737-3002×22,000lb28.8832.1811.1514.1(65◦ )12.455.23128(2-class) B737-4002×23,500lb28.8835.2311.1516(65◦ )14.275.23146(2-class) B737-9002×27,300lb35.7940.6712.3719.2(65◦ )17.175.72177(2-class) A310-2002×53,200lb43.8946.6615.8231.6712.479.6265 A3202×27,000lb34.137.5712.4514.3(65◦ )12.647.59164 A3212×30,000lb34.144.512.6514.3(65◦ )16.97.59200 MD90-3032.8743.039.526.2(65◦ )23.525.08172 B757-2002×37,400lb38.0647.3213.7420.6(65◦ )18.297.32186 F28-20002×9,850lb23.5629.628.8717.6810.335.0379 BAe146-2004×6,700lb26.3328.568.6312.5611.224.72106 LongHaul 747-4004×58,000lb64.9470.6719.5126.3(55◦ )25.6211416(3-class) B747-400ER4×59,500lb64.9470.6719.5126.3(55◦ )25.6211416(3-class) B777-2002×84,300lb60.9363.7318.7629.9(60◦ )25.8810.97305(3-class) B777-3002×98,000lb60.9373.8618.7635.9(60◦ )31.2210.97368(3-class) B767-2002×52,000lb47.5748.5116.1323.0(60◦ )19.699.3296(2-class) B767-3002×60,600lb47.5754.9416.0326.8(60◦ )22.769.3261(2-class) B767-300ER2×61,500lb47.5754.9416.0326.8(60◦ )22.769.3296(2-class) B767-400ER2×60,600lb51.9261.3717.0130.7(60◦ )26.29.3296(2-class) B787-92×53,000lb60.1255.9116.9123.789.8224 A330-3002×72,000lb60.30463.68917.1827.4(60◦ )25.3710.684335 A340-5004×56,000lb63.4567.9317.5332.3(65◦ )27.58310.684313(3-class) A340-6004×60,000lb63.4575.36217.4338.2(65◦ )33.63710.864380(3-class) A380-8004×80,000lb79.7572.72724.139.6(55◦ )31.72712.456555(3-class) Commuters Brasilia2×1,500eshp19.6919.726.3117.86.86.0730 SAAB20002×3,096kW24.7727.287.7212.57.146.7150–5 F27-5002×2,140eshp29.0125.0828.68.7220.19.637.2256 DHC-74×1,174eshp28.3524.487.9918.98.387.1654 DHC-8-1002×2,000eshp25.8922.257.499.22(60◦ )7.957.8856 ATR72-5002×2,475eshp27.0527.177.65NA10.774.0166 aMaxnosewheelsteeringanglesbetween55◦and65◦. Source:References5,6,manufacturers’brochures.
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Table3.1bAircraftCharacteristicsofAirCarriers:Weight,FieldLength,CruiseSpeed,andPayload PayloadRange:International StandardAtmosphere,StillAir ZeroRwyGradient(Note1) RangeatMaxMaxRange PayloadPayloadWeight(lb×1000) TakeoffLandingEmpty,Nauticallb×Nauticallb× AircraftType(max)(max)Operatingmi1000mi1000
Cruise Speed (knots)
FARFieldLength(m) InternationalStandard AtmosphereISA SeaLevel,15◦ C TakeoffLanding Short/MediumHaul B737-300139.5115.872.542200168042719503427509 B737-40015012474.1725501880450174045250035 B737-900174.2146.394.582300210045090045.4290023 A310-200291261169.516001400488221069.7443027.1 A320-200166.5142.282.120501460450188045.6268034 A321-200196.2166.5103.627501625450135054235038 MD90-3015614288.1721501850438120041.8220029 B757-200220198129.818901470494120064.0466011.8 F282000 BAe146-20088.37747.2151010604191,53522.1164620.9 LongHaul B747-400875630396.3300024004935200148.7700091 B474-400ER910652406.9335025004956200148.1800078 B777-200632.5455299340018404905800131865056 B777-300660524351.7325021754903600143.3550096 B767-200300270178.317221435470222067.7490015.9 B767-300350300189.7526001720470225088.25440051 B767-300ER412320198.4432001910470410090640046 B767-400ER450350229312021704703800101550061 B787-9547NA254NANA4878000NANANA (continues
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Table3.1b(continued) PayloadRange:International StandardAtmosphere,StillAir ZeroRwyGradient(Note1) RangeatMaxMaxRange PayloadPayloadWeight(lb×1000) TakeoffLandingEmpty,Nauticallb×Nauticallb AircraftType(max)(max)Operatingmi1000mi1000
Cruise Speed (knots)
FARFieldLength(m) InternationalStandard AtmosphereISA SeaLevel,15◦ C TakeoffLanding A330-300478.4394.6279.3225017404733300115550062 A340-500804.7520.3370.131502000479700054910023 A340-600804.7560384.2315021254795600145.5785069 A380-8001234.6851610.4290019004956500185.5880076 Commuters Brasilia21.721.712.3108012202875756.01570 SAAB200050.2748.530.213001380NA82050.26128010 F27-500454226.31670100024882513.22180 DHC-D7413924.455055023863711.11740 DHC8-1003433.9221100880238540911.7 ATR72-50049.649.328.551290107027630016.65NA aStandardreservesforholdinganddiversionincluded.NA,notavailable,Jan2010.LandingDistances:Flaps30◦ ,wetrunway. Source:References5,6,manufacturers’brochures.
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Table3.1cCharacteristicsofSelectedGeneralAviationAircraft MaximumMaximumEmptyFARFAR Length,Span,Height,No.ofTakeoffLandingOperatingTakeoffLandingRange AircraftftftftPassengersWeight,lbWeight,lbWeight,lbLength,mLength Gulfstream15056.7655.5819.09826,10021,70015,1001,524878m Gulfstream65099.7499.5725.331899,60083,50054,0001,829914m Hawker850XP51.1854.3318.08828,00023,35018,4501,534808m Learjet40XR55.5647.7814.13621,00019,20013,8611,426811m BeechSuperKing43.8354.514.331312,50015,0009,1101,006442m1400-1974 Air300L13.36m16.61m4.36m5,672kg6,806kg4,133kg Beech400A48.2554.514.33816,10015,70010,250 13.36m16.61m4.36m7,305kg7,123kg4,651kg13081072m TwinOtter51.76518.62012,50012,5006,700366320m CessnaMustang40.5843.1713.424–68,6455,300949729m 12.37m13.16m4.09m39,22kg2,405kg Cessna50.1753.3315.176–813,87012,7508,700970845m CitationCJ3+15.29m16.25m4.62m6,293kg5,785kg3,947kg CessnaCitationX72.3363.9219.258–1036,10031,80021,70015671040m 22.05m19.48m5.86m16,397kg14,428kg9,846kg DassaultFalcon7X76.088625.88–1269,00034,0721678690m 23.19m26.21m7.86m31,307kg15,459kg Dornier228-21247.6349.515.838–1214,55013,4488,243793450m600-1080 14.52m15.09m4.82m6,602kg6,102kg3,740kg Embraer11049.5850.2816.1718–2113,01012,5638,005975430m400-920 Bandeirante15.11m15.32m4.925,903kg5,700kg3,632kg
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In essence, an aircraft type is required to demonstrate the field length required for the following cases: (a) to complete a takeoff to 35 ft (11 m) altitude with all engines operating, (b) to complete a takeoff to 35 ft (11 m) altitude with an engine failure at a critical point, (c) to stop after aborting a takeoff with an engine failure at the same critical point, and (d) to stop after landing from a height of 50 ft (15 m).
The demonstrations take place under carefully controlled conditions of flying speed, aircraft weight and configuration, and airfield altitude and temperature. Safety margins are then added to these demonstrated distances to allow for variation in pilot perfor-mance, aircraft perforperfor-mance, and environmental conditions in service. The margins are typically 15% in the all-engine-operating takeoff case and 67% in the landing case;
the difference is due mostly to the extra difficulty of controlling and monitoring an approach compared with the relatively fixed and known conditions on takeoff. It is also recognized that the in-service performance of old aircraft, while conforming to adequate maintenance procedures, will be less than the performance of new aircraft under certification demonstrations.
Extra margins are implicit in the procedure just described, insofar as most airports accepting commercial flights do not have obstructions at the ends of their fields and most airfields have either visual or electronic guidance on the approach path. However, experience has shown that margins of this order are necessary if a satisfactorily low rate of hazardous incidents associated with field length is to be maintained. In this way, a required field length is assigned to each certificated aircraft, for every practical combination of variations in weight, altitude, and temperature, and the information is published in the official flight manual as a series of charts. This information is collated by the FAA (2) and the ICAO (3). Figure 3.7 is a modified example taken from the FAA’s runway length requirements for airport design. The example shown indicates the runway lengths required at 1000 ft elevation and STD+ 15C for a B737-900 takeoff with maximum design takeoff weight (174,200 lb) and for takeoff with a restricted takeoff weight of 150,000 lb.∗The FAA provides a companion chart for calculating the landing runway length required.
Published field length requirements can be used for the following purposes:
1. Checking the ability of an aircraft to take a specified payload from, or to land