Introduction Flashcards
what are teh three categories of an aircraft
airframe
powerplant
systems
airframe purpose
rigidity (structures) l
lift (aerodynamics)
what weight are systems
1/3 of empty mass
percentage of development costs to systems
1/3 developmetn costs and production cost (higher military)
percentage of systems for DOC and DMC
1/3
what is a source of major improventes in systems
digital data processing technology
give an example of multidiscipline disign optimization
aircon affecting engine design
load gust aleviations to reduce loads on wings
what is WATOG
world airlines technical operations glossary
what document groups aircraft systems? how does it do it?
specification 100 of the Air Transport Association of America
3 two digit numbers for system, subsystem, and part
list the subdivisions between system and part
system subsystem component subassembly part
what is a system
interrealted items working to perform a function
what is a subsystem
a functional portino of a system. which contributes to operational task
what does ATA call aircraft systems
airframe systems
ATA 21
aircon
ATA 24
ELECTRICAL POWER
ATA 27
FLIGHT CONTROLS
ATA 26
FIRE PROTECTION
ATA 28
FEUL
ATA 29
HYDRULIC POWER
ATA 30
ICE AND RAIN PROTECTION
ATA 32
LANDING GEAR
ATA 35
OXYGEN
ATA 36
PNEUMATIC
ATA 38
WATER/WASTE
ATA 49
AIRBOURNE AUXILARY POWER
which systems are avionics? what characterizes avionic systems
auto flight, communication, indication and recording, navigation
processing information
what is the primary purpose of gerneral systems or utility system? examples
transfer of energy
aircon, electrical, pneumatic, feul (non avionic)
what document has spec 100 ATA become a part of?
ATA 2200
secondary power systems-> define, list
nonpropulsive generation and transfer of power
electrical power (24), 29 hydraulic, 36 pneumatic, 49 auxilary power
what is the enviornmental control system? which systems do it
maintain immediate temp and pressure of enviornment
2-> aircon 21 and 35 oxygen
describe the basic process of certification
OEM of aricraft works with aviation authorities to develop a certification plan
analysis, flight tests, and ground test show compliance with certification requirements
a type certificate is issued for the aircraft
each craft must show airworthiness and conformity to prototype
follow agreed upon maintenance schedule
what is certification based off of for large aeroplanes?
europe -> JAR 25
us -> FAR part 25 Airworthiness Standard: Transport Category Airplanes
how to interpret FAR part 25 and JAR 25?
matericals provided.
FAR: AC (Advisory Circulars) AC 25-17 and AC25-22
JAR: ACJ (Advisory Circulars Joint)
AMJ (Advisory Materials joint)
define safety
risk is lower than permissible risk. risk is probabilty of failure
how is risk defined in safety definition?
probability of failure
how are the safety requirements categorized? where stated?
section 1309 of jar 25
prob of failure 10 ^ __ per flight hour -> effect
0 to -2 -> normal
-2 to -2 -> nuisance
-3 to -5 -> operational limitation, emergency procedure
-5 to -7 -> pax injury, less safety
-7 to -9 -> a lot of safety lost, some pax death
< -9 -> catastrophe, many death and aircraft loss
what is reliability
probability of survival. made via strictly defined failure criteria
how do prob of failure and prob of survival relate
F(t) + R(t) = 1
relation between failure rate (lambda) and MTBF
MTBF = 1/lambda
what is the difference between z(t) (hazard rate function and lambda (failure rate)
lambda assumes constant hazard rate function
what is the maintenence cost driver and how is it calculated
MTBUR (mean time between unscheduled removals) = MTBF * FTRR (failure to removal ratio)
equations for reliaility and failure in terms of failure rate
R(t) = e^(-lambda * t) F(t) = 1-e^(-lambda * t)
how to prob of failure and reliability and failure rate combine with systems in series and paralel
Series: multiply reliability rates, add failure rates
parallel: multiple failure rate, multiply failure rate
How can reliability and faiulre of complex systems be determined?
Reliaility block diagrams of fault tree analysis. (There is software for this). Each component (mech and elec) has listed failure rates in documents (Rome 1985 and MIL_HDBK-217.
define and classify redundancy
redundancy is more means than would be necessary to accomplish a task
homogenous and inhomogenous (multiple means different)
active-active (both normally working. with failure one has heavier load) or active-standby (one working ony. can have hot (actively monitoring) and cold standby )
difference between active-active or active-standby?
active-active (both normally working. with failure one has heavier load) or active-standby (one working ony. can have hot (actively monitoring) and cold standby ) . Avoid dormant failure by switching primary system
what is a common cause failure
simultaneous failure from the same event. come from errors in design, operation, maintenance, or the environment,
methods to avoid common cause failures in design phase
inhomogenous redundancy segregation of distributino software redundancy made by different teams safety critcal components in safe areas saparate redundant components
what is steady state availability?
prob that a system will be available when required.
Ass = MTBF/(MTBF + MTTR)
what is dispatch reliability and a method to increase it?
Instantaneous availability and moment of dispatch from the gate. Depends on dispatch reliability of systems combined primarily.
BITE (built in test equipment to provide detail failure reporting) extra redundancy (beyond what is required for cert) ie with flying spares, beyond minimum equipment list
what is thte minimum equipment list?
The list of subsystems and components which need to be available at time of takeoff) (airline)
master minimum equipment list provided by certification authorities
how is reliability assurance performed
fault tree analysis or reliability apportionment via top down approach.
failure mode, effects, and criticality analysis via bottom up approach
zonal analysis
how is software and environmental reliability dealt with?
defy above calculations.
software DO-178B
environment DO-160D
which aircraft size has higher percentage system weight of oem?
business jet (40%)
larger have 23%
ata chapter systems with high and medium mass %
high:
32 landing gear
25 equipment and furnishings
medium:
21 aircon
27 flight controls
29 hydraulic power
how is comparing masses done?
Statistics taken
difficult to compare because of different mass breakdowns
what is a main reason to detail system mass calculate
cg
how do mass predictions progress throughout design
statistical
use older aircraft
subcontractor offers item masses of similar components
delivered items of known mass
what can mass estimations be used for as well to estimate
cost (unless expensive mass saving operations used)
what are main secondary power SOURCES?
APU -> uses feul, independent from main engines,
RAT -> uses velocity (while consuming PE)
aircraft batteries
ground power (direct ground electricity, HP hydraulic fluid, pressurized air, airconditioned air) (or sometimes just ground electricity and power conversion)
one classification of secondary power loads
technical (required safe operation)
commercial (required for pax comfort)
explain trends in secondary power
increasing technical and comercial loads and longer flights require more and more secondary power.
There is not linear potential to collect secondary power (potential deadlock)
possible solution: all powered by electricity
what is a tradeoff study and which is the most important factor (and the less important factors)
comparison of different system design principles
most: cost
less: safety (certification is boolean) and performance (set in design and over perform is more cost)
in terms of operational cost, what are evaluated criteria and what are two ways to approach this?
aspects: system cost, maintenence, reliability, mass
methods:
aircraft system level: one weighted sum based on individual criteria
aircraft level: DOC
describe the reason for and workings of the system level DOC method
C_DOC,SYS = C_dep (depresiation) + C_F (feul comsumed) + C_M (Maintenence) + C_DEL (delays) + C_SH (spare holding)
