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AEROSPACETESTINGINTERNATIONAL.COMAPRIL 2015 |^47

Undercarriage trials z

A380 LANDING

GEAR SYSTEM

According to a 2008 Airbus

document, the full A380 landing

gear system comprises:

• Nose landing gear with
  twin wheels;


• Two body landing gears,
  each with six wheels, four of
  them braked;


• Two wing landing gears, each
  with four wheels, all braked;


• Extension/retraction system;


• Braking control system;


• Steering control system
  (nosewheel and body
  wheel steering);


• Wheels, tires and brakes;


• Monitoring systems for the tire
  pressure indication system, brake
  temperature indication system
  and oleo pressure monitoring
  system. The undercarriage doors
  and their actuation systems must
  be added to these.

OFF THE TOP OF YOUR HEAD

How many personnel work in the test department?

Gary Warburton: “There are currently around 25.”

Is the department busy with research outside its

regular test schedule?

Gary Warburton: “We have three projects on right

now, all scheduled for first flight this year or next.”

How long does a landing gear test effort last?

Tim Whittier: “Programs typically last three-plus

years when they include fatigue testing.”

What is the primary function of UTAS’s test effort?

Tim Whittier: “Our test work is most importantly

a validation of our analysis.”

How do you think test will change in the future?

Tim Whittier: “We hope to improve our analysis and

focus on certain parameters, rather than testing entire

landing gear.”

component testing. “For drop testing,

we take a fully assembled landing gear,

place it in a carriage on a drop tower

and release it at different descent

speeds and surface velocities to

simulate its dynamic performance.

Static testing is also performed on fully

assembled gears and we apply loads up

to the maximum they would be

expected to see, assessing whether they

can withstand them.

“We test two types of load. A gear

is expected to recover from yield load

without deformation, while ultimate

load deforms the gear but it must not

fracture. Yield load is actually the

maximum load the gear is expected

to take, while ultimate load is a

factor above.

“In durability testing, the gear is

placed under loads to simulate a flight,

and that is repeated until it’s equivalent

to the lifetime of the aircraft. Then we

add an additional scatter factor of

between three and five additional lives

to demonstrate that the gear definitely

meets its requirements.”

Marco Perrella, director,

in-production engineering, explains

that additional test processes are

applied at component level. “They are

typically carried out on smaller items

such as actuators and steering

manifolds. They go through all the

22

The number

of wheels on

the A380; just

two are on the

nose landing

gear

32

The unique

number of

undercarriage

wheels on the

Antonov-225,

configured in

two bogies

with 14 wheels

each, and four

up front

BELOW LEFT: UTAS

manufactures gear

for a variety of

aircraft types

at Oakville,

including the

Bombardier CRJ

other test procedures, but also undergo

a fair degree of environmental testing.”

UNDERCARRIAGE FACILITY

Given Oakville’s product range, its

test facilities vary enormously in

capability and it has drop towers

capable of handling gear ranging

from the size of that installed on the

Gulfstream G450 right up to A380

and Boeing 777 legs. It tests over this

wide range of dimensions using three

towers, specially equipped to vary

‘weight over gear’ according to

aircraft type. A fourth tower is in

the planning phase and will facilitate

testing across an extended range

from 1,500kg to 500,000kg.

Other variations between aircraft

types are less immediately obvious,

but as Perrella explains, vertical

acceleration is another factor that

testing has to take into account. “An

A380 typically lands at around

5-7ft/s in service, and the maximum

we need to meet is 10ft/s at maximum

landing weight and 6ft/s at maximum

take-off weight. We also perform a

case, called the ultimate drop test, at

12ft/s, with the intention of ensuring

that the landing gear shock strut does

not bottom.

“With helicopters, it’s a different

situation with a different set of

THE TEST PROCESS
Gary Warburton, senior mechanical
designer and project leader – test lab at
Oakville, explains that although there
are variations in test requirements, a
landing gear typically goes through a
series of standard test procedures.
These include dynamic level testing,
perhaps more familiar as drop testing,
as well as static, durability and