FLIGHT SAFETY Technology and the Human Factor



FLIGHT SAFETY Technology and the Human Factor
Technology and the Human Factor
A pilot’s perspective
Prof. dr ir J.A. Mulder
Delft University of Technology
How safe is it?
The common causes of accidents
The Flight Deck: past, present and future….
Automation and Situation Awareness
Review of a famous accident
Lessons learnt
How safe will it be?
Dependent Failures
Independent Events
P (A & B) = P (A) · P (B)
Dependent Events
P (A & B) > P (A) · P (B)
P (A & B) = P (A) · P (B/A)
The pilots of an Air France Airbus A330 that
crashed into the Atlantic Ocean two years ago
apparently became distracted with faulty
airspeed indicators and failed to properly deal
with other vital systems, including adjusting
engine thrust, according to people familiar with
preliminary findings from the plane's recorders.
The Wall Street Journal (2011 May 24, Pasztor,
•The aircraft slowed to a stall shortly after the
autopilot disconnected. The pilots faced a
series of automation failures and disconnects
related to the plane's airspeed sensors.
•Within 4 min 28 sec 16 ACARS fault messages
were sent to home base on faults resulting
from these unreliable airspeed sensors (display
indications, auto thrust, TCAS, …..).
•Loss of Situation Awareness.
More examples of common cause accidents
LY1862, 1992
OO-DLL, 2003
UA232, 1989
JA8119, 1985
El Al LY 1862, 1992: Pylon failure
DHL OO-DLL: Hit by missile
Japan Airlines JA8119: Lost vertical tail
United Airlines UA232: Engine desintegration
Cockpit Douglas DC-3, first modern transport aircraft
Flight deck Lockheed Constellation, 4 man crew
Flight Engineer
Flight deck Boeing 737-300, FMC
Flight deck Boeing 767-300, FMC, EFIS
Rasmussen’s ‘Skills, Rules, Knowledge’
framework, from pilot to supervisor
• Skill based behavior
• Rule based behavior
• Knowledge based
• Manual control, effort,
training, the pilot as ‘ace’
• Handling the auto pilot,
procedures, check lists
• Feed Flight Management
System (FMC) with
information, direct the
flight through the the
coupled FMC
Invest in pilot skills!
Advanced flight simulators!
So, we have to do better!
Better Safety & Performance by:
• Technical advances in
– Aerodynamics, structural design & materials, systems
– Engines
– Avionics (Fly by Wire, ‘Glass cockpit’, triple redundant
auto flight systems with autoland, Flight Management
System (FMS), TCAS, GPWS)
• Human Factors
Crew Resource Management (CRM)
Situation awareness
Training, checking
Flight deck (r)evolution
Ironies of automation
Aircraft are open systems
Aircraft are open systems
But … automation will proceed
Crew Resource Management (CRM)
• 80% of non-technical accidents due CRM failure:
‘individual pilots do not crash airplanes, crews do’
• Good leadership:
– be a strong leader, but not autocratic
– delegation of responsibilities
– communicate, support, joint decision making
• Pilot training in CRM
– missions in flight simulator
– videotaped sessions, debriefing
Human-Machine Interface (1)
Intuitive 3D perspective display
Human-Machine Interface (2)
low situation awareness
Display of commands, do
what you are told….
5 NM
IF (tCPA< look-ahead) AND (|CPA|< 5 NM) THEN
conflict = TRUE
conflict = FALSE
Human-Machine Interface (3)
optimal situation awareness
Ecological display, see
what you should do!
Last resort: ‘Care-free’ handling and navigation!
On October 4th 1992 a Boeing 747-200F
freighter aircraft, Flight LY 1862, departing
from Schiphol, crashed into an apartment
building in the Bijlmer neighborhood of
Amsterdam killing 43 people.
Flight LY 1862 failures
Structural failure pylon eng # 3 due to fatique
Destruction of wing pylon eng # 4
Wing leading edge damaged
Loss of hydraulic systems 3 and 4
Loss of electrical systems
Partial and complete loss of control surfaces
Reduced thrust, increased aerodynamic drag
Asymmetrical thrust, aerodynamic asymmetry
Asymmetrical mass distribution
Route to disaster
Flight 1862, Amsterdam, October 4th, 1992
Failure mode analysis
El Al Flight 1862 Failure Mode Configuration
Aircraft Systems
Hydraulic systems 3 and 4 off
Engine 1 and 2 thrust asymmetry
Lower rudder lag
Mass Properties
Engine no. 3 and 4 weight loss, 4,014 kg each
Pylon no. 3 and 4 weight loss, ± 1,000 kg each
Lateral center of gravity displacement
Total weight loss: 10,0028 kg
Lift loss due to wing damage (∆Lwing)
Rolling moment due to wing damage (∆Lwing)
Drag due to wing damage (∆Dwing)
Yawing moment due to wing damage (∆Nwing)
Pitching moment due to wing damage (∆Mwing)
Right inboard aileron and spoiler 10 and 11
aerodynamic efficiency loss
Control surface lost
50% Hinge moment loss / half trim rate
Control surface available
Flight 1862 damaged aircraft flight mechanics
W*sin( φ)
∆Lwing + Lδr
NT + ∆Nwing
Nβ + Nδr
What was learnt?
• Extreme example of common cause
• Situation awareness was poor on aircraft
status, lateral navigation and vertical
navigation (kinetic and potential energy
• Unaware of reduced safe flight envelope
• Workload (manual control) prevented ‘high
level’ decision making
Defenses against Common Cause
•Improved design, materials, maintenance, systems
•Automation to reduce crew workload
•Focus on ways to improve situation awareness
•Crew resource Management & training
•Advanced measures which will exploit (remaining)
physical options for survival in case of….
Advanced Flight Control: YES!
• All transport aircraft will be ‘Fly by Wire’
• Much redundancy in sensors, systems, control
effectors, aerodynamics, computers (infinite capacity)
• Controllers work with nonlinear aircraft dynamic
models (NDI)
• On-line model identification, sensor integrity checks,
use all information to estimate state
• Adaptation, reconfiguration, control allocation, keep
aircraft in computed adapted safe flight envelope
• Care free maneuvering, navigation
How safe will it be?
• Automation (and systems)!
• Need still Human Pilot, open system
• Support the pilot through improved Situation
• The unthinkable is bound to happen
sometime. Not 100% but close, very close.