MODULE 4 Flashcards
NOISE
_________ is any undesirable or unwanted sound.
Noise
The first-generation jet aircraft in the ________ led to a rapid expansion in
commercial aviation and their engines created__________
1950S
significant noise.
To allay public concerns in the
1960s, authorities put in place __________ as traffic grew at major
airports such as ______________________
airport-specific noise limits
London/Heathrow and New York/Kennedy.
In the 1970s, the _____________ introduced the first noise certification standards
and the ______________promoted similar standards
globally (Smith, 1989)
U.S. Federal Aviation Administration (FAA)
International Civil Aviation Organization (ICAO)
Chapter _ of ICAO’s ____________ to
the Convention on International Civil Aviation” (ICAO, 2008a) defined noise standards
for aircraft certified before October 6, 1977 (with some exemptions)
2
Environmental Protection/ Annex 16
Chapter _______ for aircraft certified between then and December 31, 2005
3
Chapter _ for aircraft
certified thereafter.
4
______________
correspond to ICAO Chapters 2/3 I 4. The standards outline noise limits at approach,
sideline and flyover certification points nd cumulative across all three points
U.S. Federal Aviation Regulation (FAR) Part 36 Stages 2/3/ 4
Sound level is measured in ________
decibels (dB)
each new ICAO chapter
imposes increasingly stringent noise limits, resulting in a ___________cumulative
reduction in allowable noise.
10- to 20-dB
airframe sources
fuselage
wing including high-lift devices)
landing gear
vertical/horizontal tail
engine sources
fan
core
exhaust
nacelles
Aucillary Power Units APU
two general sources of noise from aircraft
engine
airframe
Aircraft generate noise whenever there is:
1.high-speed or turbulent airflow and/
2.high-speed mechanical movement and rotation.
____________comes from the flow of air through and rapid rotations of the various
components of the engine fan and core elements, as well as the high-speed gases in
the engine exhaust being expelled into the outside air.
Turbofan engine noise [and noise
from auxiliary power units (APUs)used to provide power when aircraft are on the
ground]
__________includes the turbulent air shed from each blade and the interactions
between the blades.
Turboprop (propeller) engine
is caused by the flow of air over the surfaces of
the aircraft and the turbulent flows created by the structure and cavities introduced by
the deployment of high-lift devices and landing gear.
airframe noise
_________ tends to dominate on the ground, especially during takeoff when
the engines are at very high thrust level, on landing when using thrust reversers and
when taxiing at low speed.
Engine noise
By contrast, airframe and engine noises are about equally
important during approach and landing operations when aircraft are at low altitudes in
____________ with high-lift devices and landing gear extended
and engines at lower thrust levels than at takeoff
11 dirty” aerodynamic configuration
Another source of aircraft noise is
the ________ created by aircraft flying at supersonic speeds which can be very
disruptive to activities on the ground.
sonic boom
This issue severely limited the market for
supersonic commercial aircraft introduced in the ________
1970s
Only the ___________ found a niche market serving transatlantic routes (overland flights were
banned due to the sonic boom concerns) until its retirement in _______ on economic
grounds.
Aerospatiale-BAC Concorde
2003
The increasingly stringent noise certification standards have spurred the
development of________ for new aircraft.These have significantly
reduced noise impacts
low-noise technologies
Most reductions in aircraft noise have
been achieved through improvements in _______, especially the transition
from ________________ to
engine technology
turbojets
high bypass ratio turbofan engines
The ___________ is the ratio
between the amount of air drawn in by the fan that bypasses the engine core relative
to that passing through the core.
bypass ratio
Large modem turbofan engines have a bypass ratio
of around ________
10:1
Although bypass ratios have generally increased over time for modem turbofan
engines, a limit is being reached which manifests as the _________
plateauing in the noise
reduction curve
Higher bypass ratios require_____ fan diameters that increase the weight and drag of the engine and thus increase fuel burn. This implies a
tradeoff between environmental impacts of noise and climate change from fuel bum
emissions discussed later in this chapter
larger
Meeting future noise targets [such as the ____________________________________________ in perceived aircraft noise level relative to _____ from_____(EC,
2011) and NASA’s long-term goal for a cumulative 62 dB reduction below Chapter 4
standards (NSTC, 2010)] will require new noise reduction technologies.
European Commission’s goal for a 65
percent reduction
to 2000 levels by 2050
Near-term
incremental technology enhancements include ___________,____________
(which increase the mixing of the core and bypass air, reducing engine exhaust noise),
and __________(but these also increase weight and hence have
fuel burn impacts).
engine core
nacelle chevrons
streamlined landing gear fairings
UHBR and its other term
streamlined landing gear fairings
unducted fan
In the medium-term (possibly by 2020), ________________AND __________ (UHBR, also called unducted fan) engines are being promoted
for significant fuel savings, but their impact on noise needs to be carefully monitored.
geared turbofans and
ultrahigh bypass ratio
Longer-term (unlikely to be available commercially until at least 2025), more _______________are being
explored. These absorb or heavily shield engine noise, leading to significantly lower
noise impacts on the ground.
integrated
airframe/engine designs afforded by blended-wing body configurations
