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Very
Efficient Large Aircraft |
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Fifth Framework Programme
Sustainable development, global change &
ecosystems |
VELA
is an ambitious project to create appropriate innovative transport
aircraft concepts and associated development tools for Very Efficient
Large Aircraft. The fire and evacuation modelling aspects of this
collaborative EU project is lead by FSEG of the Centre for Numerical
Modelling and Process Analysis, University of Greenwich. The project
runs from 2002 - 2005.
The partners
for the project are:
Airbus,
FSEG University of
Greenwich,
ONERA,
INTA,
DLR,
NLR,
CIRA,
VZLU,
TU,
Bristol University,
PEDECE, IBK, SENER
Modern jet-aircraft are accepted as a part of the
transport system throughout the world. They have a high level of
commercial success and operate under state-of-the-art safety standards
and environmental regulations, but it will be impossible for this
type of aircraft to meet the requirements for ecologically-acceptable
air transport in the next 30 to 50 years. Only new unconventional civil
transport aircraft configurations promise a considerable progress in
productivity as well as meeting future economic demands and challenging
ecological constraints. Studies carried out on wing/body lifting
configurations during the last decades have shown a huge potential for
these unconventional configurations. Advantages of these types of
aircraft include reduced fuel consumption, increased passenger numbers,
aerodynamic and
structural weight efficiency. Project VELA explored Blended Wing Body
(BWB) configurations for their suitablility as mass passenger
transportation systems.

The VELA (critical technology project
– CTP) configurations are among the most promising to cope with future
demand on air-traffic in the new millennium under strong economic and
even more challenging ecological constraints.
The VELA will not result
in a final configuration for a future aircraft. It will provide a first
step in a long-term work plan and it will be followed by further
research work. |
FSEG Project Objectives |
When considering a BWB
passenger aircraft design there are many challenging questions that need
to be addressed concerning the aerodynamics, structures and flight
mechanics of such an aircraft. However, in all of these areas industry
has the luxury of past experience through military aircraft design to
initiate and guide design efforts. Two vital areas in which the
industry has no prior experience concerns passenger egress safety and
the associated possible fire development resulting from a post crash
fire.
BWB
designs being considered by project VELA are capable of carrying in
excess of 700 passengers involving a single deck but with more than two
longitudinal aisles. Questions concerning seating arrangement, nature
and design of recreational space, the number, location and type of
exits, nature of longitudinal cabin partitions, nature of cross aisles
linking each cabin section, the number of cabin crew required and the
nature of the cabin crew emergency procedures are just some of the
issues that need to be addressed. These issues have been addressed by
FSEG in Work Package 5.
Ultimately, the practical limits on passenger capacity and aircraft
design are not based on technological constraints concerned with
aircraft aerodynamics but on the ability to evacuate the entire
complement of passengers within agreed safety limits. These proposed
safety limits must be seen to provide an equivalent level of safety to
today’s standards for conventional aircraft. These issues have been
addressed in VELA work package 5 through subtasks T5.1 (Adapting an
aircraft evacuation model to accommodate BWB configurations), T5.2
(Assessing BWB cabin concepts for safe egress and short turn around
times) and T5.4 (Development
of flying wing evacuation certification requirements).
The key factor driving aircraft evacuation is fire spread and the
resulting development of non-survivable conditions within the cabin.
The traditional
prescriptive approach to aircraft fire safety regulation is based on
engineering judgement derived from operating experience and a limited
amount of full-scale and laboratory scale test fire testing. Full-scale
fire testing is important for obtaining extensive information relative
to the characteristics of aircraft fires, especially with respect to
occupant survival. However, realistic full-scale fire tests are time
consuming and financially costly. The evacuation requirement for
conventional aircraft stipulates that you must be able to evacuate the
complete aircraft in 90 seconds through half the normally available
exits. The 90 second requirement provides an estimate of the
Available Safe Egress Time (ASET), which is derived from
full-scale fire tests.
A basic question that needs to be asked is whether 90
seconds is an appropriate ASET for BWB designs? If not, what is an
acceptable ASET for flying wing designs?
To
address these challenging key issues FSEG will:
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Modify their airEXODUS aircraft evacuation model to
accommodate the unique features of BWB aircraft
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Undertake a series of evacuation analyses of the
proposed VELA BWB designs and suggest alternative cabin layouts
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Undertake CFD based fire analysis of the BWB cabin
layout to estimate fire spread and smoke filling times for a
representative fire scenario and provide a first estimate of the
flashover time based on a simple flashover criterion
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Blended Wing Body configuration

VELA 1, 1 Class configuration

VELA2, 3 Class configuration

Mesh used to model the fire propagation

VELA 1, 1 Class, Status 1, Visibility at 1.68m height at 120sec

BWB model airplane for testing aerodynamics and flight
characteristics |
Evacuation Scenarios |
Two BWB
configurations were proposed by the VELA partnership. These were
identified as consisted of VELA 1 and VELA 2. These two aircraft
consisted of fundamentally different aircraft configurations and hence
internal cabins. For each of these aircraft configurations two cabin
layouts were considered, a single class layout and a three class
layout. Each aircraft consisted of 25 Type-A exits. In the evacuation
scenarios, half the exits on one side of the aircraft were made
available. |
airEXODUS Model
Development |
•The
nature of the VELA geometries pose new questions relating to PAX
visibility and navigation as well as crew procedures and overall
evacuation performance
•In
order for airEXODUS to model these geometries new capabilities
and features had to be implemented. These included:
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SMARTFIRE
Model Development |
The fire simulations
were undertaken using the FSEG SMARTFIRE software. A number of
modifications to the code were required to accommodate the requirements
of this project. These included modifications to:
In addition, a burn
through model was developed to represent the failure of the cabin
partitions. |
Fire Scenarios |
The scenarios investigated were based around the VELA 1
configuration which was exposed to an external kerosene fuelled
post-crash fire. The fire gained access to the cabin via a single
rupture immediately opposite the external fuel fire. The size of the
rupture was the equivalent of a Type-A exit. Scenarios involving half
the available exits being open and all available exits closed were
examined. Cabin material properties were provided by Airbus. |
VELA 1 and
VELA 2 Configurations |
The VELA configurations:

VELA 1, 1 Class configuration. Click image for VR animation

VELA 2, 3 Class configuration. |
Evacuation Analysis
and Results |
More than 12 different models were run and analysed for
VELA 1 and VELA 2. All aircraft have 25 crew members, one at each exit
and five within the middle area of the aircraft. Only the left hand side
exits are functioning and each PAX initially attempts to evacuate via
the nearest exit. Within the model, the simulated crew members attempt
to redirect the PAX from their current exit to an alternative exit in an
attempt to minimise the overall evacuation time of the aircraft.
Model |
Number of PAX |
Average Sim. Time |
VELA1, 1 Class |
1068 + 25 Crew |
126
sec |
VELA 1, 3 Class |
750 + 25 Crew |
109
sec |
VELA 2, 1 Class |
1004 + 25 Crew |
100
sec |
VELA 2, 3 Class |
750 + 25 Crew |
90
sec |
It should be noted
that the quoted evacuation times are out of aircraft times and not
on-ground times.
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Fire Analysis and Results |
The computational mesh used in these
simulations consisted of over 900,000 cells. The mesh was an
unstructured mesh in order to capture the shape of the aircraft nose.
The computational mesh also captured the passenger seats and overhead
locker configurations.

View of mesh used for fire simulations

Three dimensional layout of VELA cabin fire geometry constructed within
SMARTFIRE
.A key finding of this work is that for the
fire scenarios considered, flashover did not occur within 480 seconds
(after ignition of the external fire). Thus, unlike conventional
aircraft, flashover is not the factor driving the available safe egress
time (ASET) as this is predicted to occur after 480 seconds – long after
passengers would have evacuated the cabin. However, the ASET will be
affected by the development of the heat, toxic environment and smoke
produced by the fire. The atmospheric conditions within the cabin may
have a significant detrimental impact on the evacuation capabilities of
the passengers. Furthermore, in the immediate area of the rapture,
conditions become quite severe after only 60 seconds thus it is
essential that an evacuation strategy be developed to rapidly evacuate
passengers in the vicinity of any rupture associated with an external
fire.

VELA 1, 1 Class, Status 1, Visibility distance at 1.68m
for Scenario 1 at 120sec

VELA 1,1 Class,
Predicted temperature contours at the cross aisle connecting the exit 5R
at 120 seconds

VELA 1, 1 Class, predicted spread of fire, red dots depict solid surface
which is on fire.
Click image to view the animation.

VELA 1, 1 Class, predicted temperature evolution at 1.64 m above the
floor.
Click image to view the animation.
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Follow up project |
FSEG is carrying out further
examination of the fire and evacuation performance of BWB configurations
which is continuing in the EU Framework 6 project NACRE. |
Project Partners
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Further Information |
Prof. Ed Galea
Fire Safety Engineering Group
University of Greenwich
Greenwich Maritime Campus
Old Royal Naval College
Queen Mary Building
Greenwich SE10 9LS
UK
Tel: +44 (020) 8331 8730
Fax: +44(020) 8331 8925
e-mail:
E.R.Galea@gre.ac.uk
The VELA project is funded by the European
Commission's 5th Framework Programme |

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