What is the big deal about ageing aircraft?

Submitted By: KANHAIYA KUMAR

MECHANICAL 5TH SEMIT-GURU GHASIDAS

UNIVERSITY,BILASPUR,(C.G)

What is age ?1.Chronological age.

• 25-30 Years

2.Flight Hours.

•40000-60000 Hours

3.Flight cycles.

•45000-50000 cycles

• There is no single criteria that defines an aircraft as ‘old’ (Kizer, 1989).

• Determining the age of the aircraft is further complicated by the fact that individual aircraft components age differently depending on variable factors.

• Parallels with human.

Areas common to airplanes that are typically susceptible to ageing : • Engine • Fuel System • Propeller • Controls • Fuselage • Electrical Systems • Instruments • Empennage • Landing Gear • Wing

Three main aspects of ageing of aircraft:

Fatigue

Maintenance

Safety

Effects of Ageing: Fatigue Damage Component failure Structural failure Corrosion Environmental

Degradation Wiring failure

Fatigue: cyclic loading Environment exposed Extremes of

Temperature And Moisture

Wear Deterioration corrosion

Ageing Mechanisms:

An airplane spends far more time on the ground than it does in the air.

Statistics:

‘What the bathtub curve tells us is while there’s no reason why an older aircraft should be inherently unsafe, there’s also no escaping the increased time, effort and money needed to keep it airworthy.’

Aerospace Industry Worldwide

• Global Aerospace and Defense Projections• Most aircraft(96%) have retirement age of 25.2436 years• In Africa maintenance is not up to global standards and

environmental factor have result in early retirement of 20 years

Accidents statistics: Accidents were defined as events where the aircraft

sustained substantial damage, became missing or completely inaccessible as well as events where fatal or serious injury resulted from being in the airplane or direct contact with the airplane or its jet blast.

Fatal accidents were defined as accidents which resulted in a fatal injury.

52%

13%

35%

Accidents distributionFatal ac-cidentsNormalothers

Aloha Airlines flight 243 is an example of corrosion and fatigue interacting to produce the failure of a structure.

Approximately 5.5 metres of the cabin skin and supporting structure separated from the aircraft, leading to the decompression.

Although the aircraft sustained extensive structural damage, it was able to land safely.

Aloha flight 243 crashed due to ageing, due to high flight cycles,

ductile tearing.

Case Study: Corrosion and fatigue – Aloha flight 243, 1988

At the time of the accident, the aircraft was 19 years old and had completed 89,680 take-offs and landings, with an average flight time of 25 minutes

Maintenance in ageing aircraft: In 7 out of14 recent major accidents, deficient

maintenance is the culprit. 15% increased inspection time for 10 years of age.

(Robinson) Shortage of skilled maintenance staff and existing

staff over stressed. Staff spend around 25-40% time for documentation Sometimes diagnosis can be wrong due to human

judgement Modern aircraft have thousands of sensors, which

stored failure history on ground databases. Data stored remains stagnant due to large

complexity.

Economics of Ageing AircraftsReplacement of fleetReplacing componentsMaintenance costAnnual check

Present Solution: Pulsed eddy current Transient eddy current Vibration based method(chirp vibration) Time domain reflectometer Joint time frequency reflectometer Radiographic testing(x rays)

To analyse data recorded by sensors to create predictability in failure of components for operational exposure

To create various software which will indicate component life both in air and on ground

To build reliable mathematical models, which will evaluate and synthesize such a large complex data

Newly developed technique : PZT wafer transducer active sensors offer special

opportunities for developing sensor arrays for health monitoring of aging aircraft structures.

The detection of damage due to corrosion, structural cracks, and active sensor self-diagnostics with electro-mechanical (self propagation wave) impedance method are developed.

An array of four sensors were installed along a line emanating at a right angle from the crack, and E/M impedance readings were collected from all sensors.

The tendency of frequency to shift in the vicinity of the crack was noticed.

full understanding of the correlation between crack presence, simulation of crack and corrosion damage and sensors readings is achieved.

Technology development:

Data recording Maintenance data must be recorded digitally

Flight data and operational exposure must also be recorded

Data classificationAnd working

Databases must be correlated.

Cross validated.Creating mathematical

models and algorithms

Integrate into asoftware

Integrate algorithms and compile into user friendly

software

Must be installed and usable on board and on

ground.

Indian scenario :(as on sept 2015) Air India scare of its Kajuraho-Varanasi flight catching

fire while landing and plans to replace its ageing fleet of Airbus A 320 planes.

The airline has a fleet of 64 A 320 planes and 14 of them are close to 20 years old that need urgent replacement. In the next six months, said a senior aviation ministry official, five new Airbus planes will join the airline's fleet.

The airline has also asked European plane manufacturer - Airbus - to refurbish three existing planes and enhance their lifespan by one and half years. Ministry say that the airline cannot replace all its old aircraft in one go.

The airline had planned to induct 19 new planes as a replacement but the process has acquired a new impetus after 153 people on board its Varanasi flight -- flown by a 21-year-old aircraft -- had a narrow escape after the hydraulic system of the aircraft that controls its movement malfunctioned.

Advantages and summary: This method will help us identify reliability in components , for

consideration in redesign Helps in taking feedback from maintenance , towards creating in design

of parts for better maintainability. Increase safety in ageing aircraft and reduce maintenance cost.

The purpose of this report was to investigate the relationship between ageing aircraft and flight safety, as well as to examine current and future methods for ensuring the safety of ageing aircraft. This research examined the literature on aircraft age in relation to safety and reliability, and statistical data on the age of the aircraft fleet.