A_T_I_2015_04_

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APRIL 2015

AEROSPACETESTINGINTERNATIONAL.COM

z Undercarriage trials

UTC AEROSPACE

SYSTEMS

In 2011 United Technologies announced its intention

to acquire Goodrich, combining it with Hamilton

Sundstrand to produce UTC Aerospace Systems, a

deal formally concluded in July 2012. The Goodrich

holdings included the undercarriage design, test and

manufacturing facility at Oakville, Ontario and its

portfolio of landing gear products.

Oakville delivers basic gear structures, individual

dressed gears and complete systems across a range

of aircraft including the Airbus A380 (it also has a

contract for A350-1000); Boeing 737, 747, 767 and

777; Bombardier CRJ700, 900 and 1000, and

Q400; and Gulfstream G450, 550 and 650, as well

as helicopters.

The 250,000ft^2 (2,500m^2 ) Oakville plant employs

900 people, including 450 in manufacturing and 120

in engineering.

requirements. Their landing gear must

be able to absorb 30% of the energy in

a vertical landing and their structure

the remaining portion. Descent rates

can be in excess of 18ft/s, especially in

the case of engine failure, so vertical

acceleration requirements for

helicopters are generally a lot higher

than for fixed wing.”

All the dressed gear testing includes

the aircraft tire or tires, which are

integral to undercarriage performance

and safety. These are specified and

supplied by the OEM. Gary Warburton

explains just how important tires are to

the test process: “Tires from different

manufacturers vary in carcass stiffness

and tread, for example, and tire

function and inertia may also differ.”

Depending on program specifics,

there may be an on-site role for UTAS

specialists once landing gear has been

delivered to the OEM and installed in

its prototype aircraft. Perrella says that

test personnel might witness preflight

shimmy testing on the ground, for

example, where the aircraft is taxied

over boards and data collected on

undercarriage performance for

analysis. A proportion of data is

telemetered for immediate use, while

much is recorded for future use. The

latter is especially useful for trend

identification if problems should

subsequently emerge.

SYSTEM RIGS

UTAS employs system rigs – similar to

the ‘iron birds’ used for avionics testing

• to assess the functionality of the full
  landing gear systems it creates, but in
  many cases it supplies only
  components of a wider system. The
  A380’s wing and body landing gear
  units are manufactured by UTAS, for
  example, while Messier-Bugatti-Dowty
  supplies the aircraft’s nose landing gear
  and several other manufacturers build
  components of the aircraft’s complex
  landing gear system.
  Martin Evans, head of fuel and
  landing gear integration test at Airbus,
  explains that all these items are built
  to detailed Airbus specifications that
  include definitions of interfaces

between elements. “The suppliers are

required to verify their compliance to

these specifications,” he says, “and

Airbus then verifies the integration

of these system elements, generally

through test at increasing levels of

physical integration through avionics

tests and ‘0’ Test Means to the aircraft.”

Evans explains that in Airbus

parlance, the initial aircraft is MSN001.

The Test Means that come before it are

therefore numbered ‘0’ and include

High Lift 0, Cabin 0 and Landing Gear

0. “All elements of the landing gear
   systems are integrated into a large ‘0’
   Test Means and tested prior to aircraft
   power-on, when functional tests are
   performed. The systems are then tested
   again to assess performance prior to
   first taxi and first flight.”
   Within the landing gear system,
   the gear doors and their actuators are
   major elements of the extension/
   retraction system. Evans says: “They
   contribute to the hydraulic, timing and
   state control of normal operation and,
   under gravity extension, need to be
   assessed to confirm that they do not

hinder the safe extension of all the

landing gears. Normal extension/

retraction and gravity extension

performance is confirmed when the

aircraft is still on the assembly line.”

During subsequent taxi trials,

performance, flight warning system

and reconfiguration tests are carried

out within a wide suite of testing

that leads up to rejected take-off

performance confirmation. As Evans

explains, telemetry is crucial to these

challenging, dynamic trials: “Telemetry

is extensively used during taxiing and

early flights as it provides real-time

support to the engineers and crew

on the aircraft. Through telemetry,

systems designers and specialists are

able to investigate a high number of

parameters specific to their systems

and give direct feedback, via the

telemetry controller, to the aircraft.

This activity is distributed across

the Airbus engineering sites, where

satellite telemetry rooms are linked

via Toulouse to the aircraft.” z

Paul E Eden is an aviation writer based in the UK

10

The number of

wheels on the

Boeing 787,

mounted on

four bogies

(framework/

structure)

8

The number

of wheels on

a Boeing

Stratofortress

14

The number of

wheels on the

A340-500/600

“TELEMETRY IS EXTENSIVELY USED DURING

TAXIING AND EARLY FLIGHTS AS IT PROVIDES

REAL-TIME SUPPORT TO THE ENGINEERS AND

CREW ON THE AIRCRAFT”

RIGHT: UTAS tests

and manufactures

gear for Boeing

airliners, including

the 777