Flight International 16Mar2020

34 | Flight International | 10-16 March 2020 flightglobal.com

737 MAX

Special report

DAVID LEARMOUNT LONDON

Clean sheet

flying philosophy

After two fatal crashes and a grounding, extensive remedial work should fix the 737 Max;

now Boeing must also rethink the basic design philosophy underpinning its future aircraft

R

ecent statements by Boeing’s new

chief executive, David Calhoun, make

it clear that the company is preparing

to change the way it designs its aircraft

for pilots.

Since the early days of commercial avia-

tion, manufacturers had inevitably provided

imperfect aircraft to the airlines, and their im-

perfect pilots had to learn to manage their

shortcomings. Travellers assumed aviation

was a relatively risky business, so the occa-

sional accident – even a fatal one – was seen

as just one of those things. Mechanical fail-

ures were common, and from time to time

failure by the pilots to cope with the mishap

was inevitable.

This has not been so for about 30 years.

Passengers have become accustomed to the

hugely improved reliability and higher safety

standards that modern engineering and smart

aircraft systems have provided.

So when – last year – the second of two

fatal crashes within five months involved

Boeing’s latest product, the 737 Max 8, it

caused considerable shock. As facts gradually

emerged from the investigations, regulators

at  national aviation authorities (NAAs) all

over the world deliberated about how to react.

Gradually, a consensus developed that a

change in the approach to airworthiness

certification is overdue.

NEW PHILOSOPHY

Calhoun has clearly thought deeply about the

implications for the future. This is what he

said about the design philosophy his comp-

any must adopt for its next all-new product:

“We might have to start with the flight-control

philosophy before we actually get to the air-

plane. We have always favoured airplanes

that required more pilot flying than maybe

our competitor did. We are all going to have to

get our heads around exactly what we want.”

Calhoun says Boeing needs a change in

company culture: “It will be built around the

level of light we shed on safety processes.

It will be built on the engineering disciplines

and what we do for pilots around the world,

not just pilots in the USA.” He explains why

this is necessary: “Things have changed a bit.

The competitive playing field is a bit differ-

ent. We have to plan for China... We are going

to start with a clean sheet of paper again.”

In summary, the regulators believe that

long-established assumptions about pilot re-

actions to failures might no longer be valid in

the modern aviation environment. The funda-

mental question that arises is this: what can

reasonably be expected of pilots when some-

thing goes wrong with the complex integrated

systems in today’s aircraft?

In both the accidents – the Lion Air and the

Ethiopian Airlines losses – there were reme-

dies the pilots could have deployed to pre-

vent the crashes. On the other hand, critical

failures of angle-of-attack (AoA) sensors in

both cases had triggered very confusing

aircraft behaviour for which the pilots had

been ill prepared by their training and by Boe-

ing’s aircraft manual. This is where the con-

sensus question arises in the case of the two

Max crashes: was it reasonable to have

assumed that, in the short time available,

given the aircraft’s low height in both cases,

they would definitely have been able to cope

with the stabiliser trim movement that

the  AoA sensor failure triggered – and kept

triggering?

Calhoun accepts that a flaw in the Max’s

flight-control system had proved disastrous,

but claims the design did not result from a

decision to put cost factors ahead of safety.

The flaws, he says, came from long-standing

assumptions about how pilots would react to

a failure. Boeing designers had assumed they

would get the measure of it within 3s, and act

in mitigation.

A great deal has changed on flightdecks in

the past 40 years. The advent of the digital

flightdeck in the early 1980s gradually – over

the subsequent four decades – brought ever-

higher levels of automation, greater systems

integration, more information for the pilots on

their electronic flight instrument systems,

more flight mode options for the flight man-

agement system/autopilot, and generally

greater complexity. In the transitional 1980s

Instrumentation has grown more complex over the past 40 years, with greater automation

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