Flight International - November 10, 2015

LETTERS

50 | Flight International | 10-16 November 2015 flightglobal.com

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SAFETY

Scrutinising design standards

In response to your article

about maintenance personnel

fitting a hydraulic actuator on

a Virgin Atlantic Boeing 747

upside down, (Flight

International, 27 October-

2 November): this event is not

the first time that incorrect

fitting of a component has

occurred resulting in a flight

safety incident.

I remember a Royal Air Force Sepecat Jaguar where the two

hydraulic systems were cross-connected, contributing directly to

the loss of the aircraft. I also remember a damper on a Boeing

Chinook helicopter being fitted in reverse orientation, resulting in

a serious incident.

It should be impossible to fit a component in a safety-critical

system incorrectly. As previous incidents show, if it can be fitted

i ncorrectly, one day it will be fitted incorrectly. If we really want to

prevent recurrence, we need to make these kinds of maintenance

errors impossible. Design standards for future aircraft and major

modifications should be clear on this point.

I accept the difficulty in changing the design of legacy aircraft but,

in my view, there should be a risk assessment made in each case by

the type certificate holder. This is an airworthiness issue. I hope that

is what the Air Accidents Investigation Branch report recommends.

Dave McCormick

Via email

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FLIGHT

INTERNATIONAL

We welcome your letters on

any aspect of the aerospace

industry.

Please write to: The Editor,

Flight International, Quadrant

House, The Quadrant, Sutton,

Surrey, SM2 5AS, UK.

Or email flight.international@

flightglobal.com

The opinions on this page do not

necessarily represent those of the editor.

Letters without a full postal address sup-

plied may not be published. Letters may

also be published on flightglobal.com and

must be no longer than 250 words.

FLIGHT

INTERNATIONAL

Crying out for

safe evacuation

In defence of the

aircraft engineer

In his letter, (Flight International,

3-9 November), J McDermott

expresses surprise that Boeing

had “designed a part that can be

fitted the wrong way around”.

It is true that such parts could

be made to fit one way only. I

can think of a few more actua-

tors, such as one in the air con-

ditioning packs of the Boeing

767, that can be, and have been,

fitted the wrong way around.

However, while designing

maintenance error out is feasible

in many cases, where it is not,

manufacturers and regulators

opt for other defences – such as

the need to adhere to mainte-

nance data with regards to

tooling, equipment, independ-

ent inspections and staged

recording of tasks.

Further defences such as

comprehensive shift handovers

and occurrence reporting are

other steps in breaking the

causal chain. All the foregoing

are stipulated in a European

Aviation Safety Agency ap-

proved Part 145 Maintenance

Organisation Exposition.

In the case of the 767 actuator

mentioned above, a decal placed

next to it stresses the need to en-

sure it is fitted the right way

around, with a drawing.

As an aircraft maintenance en-

gineer myself, I can guarantee that

the maintenance engineers in-

volved in the replacement of the

Virgin 747’s landing gear actuator

had every intention of ensuring

that the task was completed safe-

ly, but were probably victims of

one of the many ‘double binds’

afflicting maintenance: in this

case, lack of proper tooling (the

hoist) and – that double-edged

sword– resourcefulness.

Christian Hollyer

Milford Haven, Pembrokeshire, UK

In the aftermath of the British

Airways Boeing 777 incident

that occurred on 8 September at

McCarran airport, Las Vegas,

there has been much talk of

measures such as ‘central

locking’ for overhead bins to

avoid passengers slowing the

process by grabbing their bags.

This locking system might not

comply with current regulations.

The evacuation is generally trig-

gered by an announcement from

the captain, followed by the

sounding of the alarm.

Typically, this announcement

should be: “This is the captain.

Evacuate, evacuate.” But the ad-

dition of a lawful order from the

commander, such as: “Leave

your bags behind”, might greatly

mitigate the risk of the aisles

being – perhaps fatally – jammed

with bag-wielding passengers.

It might just work.

Terry Buckland

Cuckfield, Sussex, UK

Easy operation

In his letter (Flight Internation-

al, 27 October-3 November)

David Hayfield says unmanned

air vehicles need experienced

flyers because they “are so

difficult to fly”. This is not

always true.

In my experience, some UAVs

are usually better operated by

people who are not pilots. I refer

to co-axial, open-rotor machines

such as the Beijing Seagull and

the MLA Sprite.

Operating from a small area,

the rotors are spun up and the

built-in-test-equipment checked

for all systems operating. The

flight operator then demands a

height to which the UAV will

climb vertically to hover unless,

after lift-off, the operator com-

mands a flight speed and direc-

tion into which the aircraft will

cruise. The payload operator

directs the camera and other

sensing or mission devices.

To land, the operator returns

the UAV to a position at a height

above ground of, say, 30m and

commands “land”. The aircraft

then automatically descends

vertically at a rate of descent

proportionate to its height above

ground.

On demonstrations to cus-

tomers in various parts of the

world, we would often say:

“You can now take over” –

much to their surprise.

“Pilots” however, got bored

with the ease of operation and

wanted to show off , but couldn’t.

Reg Austin

Via email

Maintenance error led to incident

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