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“Aircraft Operating Characteristics”
Chapter 4 - Airport OperationsAshford,N. et.al.
INSTITUTO TECNOLÓGICO DE AERONÁUTICADIVISÃO DE ENGENHARIA DE INFRA-ESTRUTURA AERONÁUTICA
DEPARTAMENTO DE TRANSPORTES
José Alexandre T.G.Fregnani
21/03/2007
IT 204 Análise Operacional e Gerencial de Aeroportos
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AO4 - Aircraft Operating Characteristics
Index
1. General Considerations
2. Departure Performance
3. Approach Performance
4. Operations in inclement weather
5. New Large Aircraft
1/24GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA
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AO4 - Aircraft Operating Characteristics
General Considerations : Characteristics
•The function of the design and operation of runways and their approaches must
allow safe transition between flight and ground maneuvering.
• Aircraft operations close do the ground :
�Low speeds (80 to 150Kt).
�Extremes of lift and control envelopes.
�Expose the aircraft to risk of contact with ground.
• Aircraft Performance must match carefully with airport´s
infrastructure:
�Ground Maneuvering.
�Capability to climb and descent over obstacles.
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AO4 - Aircraft Operating Characteristics
General Considerations : Aircraft Performance
• Aircraft Performance has a huge impact on airline economics.
• Reductions of payload
( indireclty weight)
indicate large reductions
in potential profit.
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• At a given speed drag is a function of lift and therefore weight.
• Weight is the principal variable for Field lengh and Climb capability (WAT and
Obstacle clearance).
THRUST - T
DRAG -D
LIFT -L
WEIGHT - W
W•cos
γ
W•se
nγ
θγ
dt
dv
g
1
W
DTgradient climb ) (γtan •−
−==
•Aircraft performance is primarly a function between the excees of thrust to drag and excess of lift to weight.
LIFT – L
THRUST - T
WEIGHT - W
DRAG – D
L
D=
W
T
AO4 - Aircraft Operating Characteristics
General Considerations : Aircraft Performance
Therefore weight is the most important factor for both Performance and Economics !
4/24GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA
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AO4 - Aircraft Operating Characteristics
General Considerations : Matching Infrastructure
• Operators will not use airfields
where significant reduction of
payload is required or are not
adequate for the aircraft size.
• There is an economic limit to
the airport operator´s ability to:
Extend Field Lengh and Protect Obstacle Clearance Surfaces.
Principles in matching aircraft to the infrastructure:
1. Demonstrated Performance of the aircraft;
2. Use of Net Performance;
3. Assesment of Probability of failure (safety assesment);
4. Regulation of operations (JAR-OPS1/FAR 121) and performance (JAR/FAR 25).
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AO4 - Aircraft Operating Characteristics
General Considerations : Takeoff Field Lenght Required
All Engines
distance
Acel-Go
distance
Acel-Stop
distance
• All Worldwide takeoff
Regulations are based on
FAR25 or JAR 25.
• Takeoff distance
demonstration is based
on OEI or AEO
configurations.
• 1 sec. from Vef to V1.
• Takeoff Field Lenght
Required is the maximum
of:• 1.15 x All Eng.Distance
• Acel-Go distance.
• Acel-Stop distance.
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AO4 - Aircraft Operating Characteristics
General Considerations : Takeoff Field Lenght information
7/24GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA
• Runway dimensions Information may be found in AIP (Aeronautical
Information Publication) and NOTAM (Notice to Airman).
• When limited by climb capability (WAT or Obstacle), the excess of ASDA
may be used to increase energy and improve climb gradient. Higher takeoff
speeds are expected (V1.VR andV2).
→ this is called IMPROVED CLIMB or OPTIMUM V2 technique.
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AO4 - Aircraft Operating Characteristics
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General Considerations : Risk Analysis
• Risk of na accident per flight is acceptable, cathegorized and quantified.
• Under and Overshoot analysys (Monk 1981).
• RESA of 1000 ft beyond
runway strip would contain
half of the under/overshoot
accidents.
• Better to Go-Around !!!
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AO4 - Aircraft Operating Characteristics
General Considerations : Risk Analysis
• It is possible to construct protected
airspace surfaces to limit the probability
of aircraft outside them to the remote
risk category (10-7).
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•Safety requirements and economical
operations may not go in the same
direction(Ex: OEI perf. x minimum Fuel
Climb).
• More severe operational limitations are
set once the risk increases.
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AO4 - Aircraft Operating Characteristics
Departure Performance : Takeoff facts
• Takeoff performance is based on on screen height of 50 ft over threshold,
in case of Acel-GO condition.
• 2 seconds added for pilot´s reaction time between V1 and initial braking
action.
• JAR 25 requires wet runway performance accountability for all aircraft
models. This states 15 ft screen height (Acel-GO) , V1set 4 secs earlier and
one thrust reverser credit is allowed (Acel-STOP).
• Until 1998 the FAA did not require wet runway accountability, but it is now
required for airplanes certified post FAR 25 Amendment 25-92.
• Takeoff Overrun incidents :
• Related to pilot´s training and V1 concept (see slide 11).
• Moving the Airport Operator for provision of RESA (Runway Excursion Safety Area) in addition to strip and prepared stopway.
.
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• Analysis of all Jet Transport overrun incidents/accidents statistics between
1950 and 1997.
• Results:
� In more than 75% of the events, aircraft were able to fly with all
engines operating.
� Most of overruns occurred above 80 KIAS, with high energy and
therefore difficulty on braking for complete stopping.
�Less than 25% of the incidents were related to OEI or Fire.
• Actions:
� V1 seen as an action speed ( the decision must be made before).
� FirstPilot´s action to braking the aircraft must occur at V1.
� Only reject takeoff above 80 kt in case of OEI, Fire or Aircraft broken.
� Pilot´s training: V1 callout made 5kt earlier.
� Change in regulations : FAR/JAR 25.
AO4 - Aircraft Operating Characteristics
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Departure Performance : Takeoff Safety Training Aid ( Boeing,1998)
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AO4 - Aircraft Operating Characteristics
Departure Performance : Takeoff Climb Gradients
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• One Engine Inoperative Climb requirements (FAR 121 and 135 aircraft):
Gross Climb Gradient Required
Climb
Segment
1st 2nd 4th
2 ENG 0.0% 2.4% 1.2%
3 ENG 0.3% 2.7% 1.5%
4 ENG 0.5% 3.0% 1.7%
• All engines Climb:
� Gross gradient
reduced by 3.2%.
� JAR requires
minimum of:
�5.2% (2nd)
�4.1% (4th)
�CON thrust
• Light aircraft (general aviation) :“See and avoid obstacles below clound base”
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AO4 - Aircraft Operating Characteristics
Departure Performance : Special Takeoff Procedures
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• “Get them high early” technique (ATA).
� Derivative from
recommended ICAO
NAP procedure.
� Close monitoring of
pitch angle with V2+10.
� Thrust reduction at
1500ft AGL.
• “Full Clean-up” technique (ATA):� Maintain Takeoff thrust until flaps retracted.
� Fuel economy (159kg B737) but reduction on engine´s life.
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AO4 - Aircraft Operating Characteristics
Departure Performance : Takeoff Limitations
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• Other economic or environmental
considerations : noise, emissions,etc..
• Any margin between
the MTOW and Actual
Takeoff Weight may be
used for Fuel Tankering
or;
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AO4 - Aircraft Operating Characteristics
Approach Performance : Landing factors
• FIELD LENGTH LIMITS (FAR 121.195 and JAR-OPS-1.515.):
ACTUAL LANDING DISTANCEdemonstrated in flight test as follows:
� V/S < 6 ft/sec at 3 deg glide slope.
� Zero slope, smooth, DRY, hard
surface runway.
� Manual Wheel braking.
� Other braking devices: auto
spoilers deployment.
� All data reduced to ISA
Temperature.
� Vref at 50 ft over threshold.
� Vref = 1.23Vs1g
� No reverse thrust credit.
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Approach Performance : Landing characteristics
AO4 - Aircraft Operating Characteristics
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• Correct conditions at the threshold are important to
provide the predicted landing performance.
• Stabilized Approach Concept is necessary:
� Correct height (52ft for a glide path of 3 deg).
� Correct Speed : Vref.
� Adequate rate of descent: from 500 to 1000
ft/min.
� Adequate thrust.
� On glide path.
• Ground aids must be satisfactory to provide adequate
performance : PAPI and VASIS systems for visual.
• Full precision approach (ILS CAT I/II and III) are the
best aid to accurate flying. Autoland and Head Up
Display guidance may be used.
Decision Height(DH) and Runway Visual
Ranges (RVR) for Precision Approaches.
CAT DH (ft) RVR (m)
I 200 800
II 100 400
IIIa N/A 200
IIIb N/A 50
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Approach Performance : Missed Approach performance
AO4 - Aircraft Operating Characteristics
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In Cruise Configuration
Required a Positive Net
Gradient at 1500ft AGL
with OEI.
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AO4 - Aircraft Operating Characteristics
Approach Performance : Obstacle Clearance
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• Approach path must maintain
obstacle clearance on expected
flight path.
• ICAO Doc. 8168 defines how to
design approach procedures,
defining MDA/MDH and DA/DH.
• ICAO Annex 14 defines airport
protection areas.
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AO4 - Aircraft Operating Characteristics
Approach Performance : Special Approaches
• Reductions on noise/ fuel are obtained
avoiding unecessary drag on delaying
flaps and gear selection as much as
possible. (Lufthansa : B737 / 200 kg).
• Two Segment Approaches.
• “High and Fast” , unconfottable for
pilots (R/D higher than1000 ft/min on
final approach).
• NASA CDA (Continuous Descent
Approach) : tailored arrivals.pdf
• Constant Mach/IAS
• Decel at 15000 ft to Initial
Approach speed.
• Continuous descent down to FAF.
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AO4 - Aircraft Operating Characteristics
Inclement Weather
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• Inclement weather conditions have direct impact on runway capacity, due to the
increased occupancy time. Runway Capacity reduction is function of:
� Wake turbulence (vortex systems).
� IFR Operations.
� Autoland (requires extended flare).
� Increasing braking distances on wet,contaminated and slippery runways and
thus decreasing values of high speed exits (15 kt on slippery / 40 kt on dry rwy)
• Author suggests the design of exit locations based on poor landing performance.
• Croswind Effect : limitations on Flight Manuals depending on runway conditions (10
kt limitation is usually set for WET runways). Critical for STOL aircraft.
• Performance dificulties may arise with standing water, snow, slush or ice.
� Large reductions on V1 and payloads are expected.
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AO4 - Aircraft Operating Characteristics
Inclement Weather : Braking friction
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• Airport authorities report the friction characteristics of the runways using friction
measuring devices (skidometer, mu-meter, friction tester, etc…)
•These reported friction characteristics, however, do not represent the actual
aircraft braking friction, as many variables like aircraft weight, speed, braking
mechanism, tire and undercarriage characteristics are not considered on its
determination.
Reported Braking Action
Reported Friction Coefficient(ICAO)
Good (wet runway) 0.40 and above
Medium to good 0.39 to 0.36
Medium 0.35 to 0.30
Medium to poor 0.29 to 0.26
Poor ( wet ice) 0.25 and below
• The measured characteristics are
reported by the airport authorities as
"Reported Braking Action“.
• “GOOD” means no directional
difficulties ( as in a WET runway)
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AO4 - Aircraft Operating Characteristics
Inclement Weather :Windshear
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• Windshear is defined as a rapid and strong
variation of wind speed/direction in a given
altitude within a short distance.
• Most of the times is associated to variable
winds near surfaces due to thunderstorm cells
(called Microbursts).
• Strong variable gusts may invert tail to
headwinds almost immediately, leading the
aircraft to AOA variation near to stall.
• Low Level anemometers system may me
installed at periphery of airport area, in order to
provide warning alerts to pilots.
• Windshear scape guidance on aircraft´s F/D.
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AO4 - Aircraft Operating Characteristics
New Large Aircraft
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• In recent years there have been considerable
discussion concerning the introduction of
aircraft capable to carry 800 to 1000 PAX.
• A380 operational in 2Q/2007 and B747-8 in
1Q/2009 are real examples. Larger dimensions
and weights than current heavy aircraft are
expected.
• Some problems are evident to Airport
Infrastructure and capability:
� Vortex systems : runway ocupancy time
extended due to larger separations.
� Increased taxiways, runways, aprons
lateral separations;
� Cleaning and servicing.
� Loading passengers and cargo.
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AO4 - Aircraft Operating Characteristics
New Large Aircraft : Are the airports prepared ?
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AO4 - Aircraft Operating Characteristics
THANK YOU !THANK YOU !THANK YOU !THANK YOU !
José Alexandre T. Guerreiro [email protected]
[email protected]