Rear Fuselage Performance
Introduction
The nature of the airflow over the rear fuselage and empennage (the horizontal and vertical tail surfaces) of a civil aircraft is fundamental to the effective operation of the tail control surfaces and has a significant affect on overall aerodynamic efficiency. Good design of the rear fuselage and empennage can have considerable benefits in reducing fuel consumption which makes the aircraft more environmentally friendly and less expensive to operate.
The Role of Wind Tunnels
The airflow over the rear fuselage and empennage is strongly coupled with the airflow coming off the wing. This interaction combined with the complex geometry of the rear fuselage and tail assembly makes the airflow challenging to predict using numerical methods.
Subtle changes in design made during the aircraft development process can have unexpected consequences in the airflow which may not always be detected in computer simulations.
Wind tunnels can provide the large quantities of high-fidelity data with the speed and reliability needed to give the highest levels of confidence in the design of the rear fuselage and empennage before flight test.
When testing rear fuselage performance, models are supported via the wings with a twin sting arrangement instead of via the fuselage with a central single sting. This is because a central single sting would upset the airflow over the rear fuselage and empennage. The absence of the central sting also permits a more representative fuselage shape to be modelled. Because the focus of the test is on the performance of the rear of the aircraft, the influence of the support booms on the airflow over the wings can be tolerated.
A typical test may involve the design and manufacture of the
empennage, rear fuselage or the complete aircraft model followed by
a wind tunnel test. The aerodynamic loads on the rear fuselage can
be measured by creating a small gap between the rear fuselage and
the rest of the model and connecting the two parts with a main
model balance which measures the loads. This capability allows very
small changes in performance due to subtle changes in model
configuration to be measured which may not be
possible measuring the overall load for the complete
aircraft model.
World Class Capability
ARA offers a one-stop service for customers starting with the design and manufacture of model components and balances followed by gauging and calibration of balances and finishing with a test program in our Transonic Wind Tunnel. We have a world leading capability in the manufacture of all model components, support mechanisms and balances completed to the very highest standards.
We offer manufacture of models and balances which are compatible with other wind tunnel facilities and our twin sting support systems are specifically designed for aircraft with high mounted engines at the rear. These support systems are also ideal for blended wing bodies and flying wings.
Uniquely, our support systems can move in yaw as well as pitch
which enables both lateral and longitudinal stability and control
to be investigated during a test. In addition, the horizontal
separation of the support booms can be adjusted to our customer’s
specification.
A Wealth of Experience
ARA has over 30 years experience of twin sting testing having been a pioneer of the technique on private jet aircraft with twin mounted engines.
Excellent Value and Productivity
Our highly experienced test teams deliver excellent test program management combined with rapid model reconfiguration to a superb standard to provide our customers with an efficient and productive service which provides excellent value.
Data Acquisition and Processing
Customers who test with us can take advantage of our proven and flexible data acquisition and processing capability. We offer seamless integration of customer supplied code and programs into our in-house data processing suite. We provide full visibility and traceability of our data processing steps giving our customers the highest level of confidence in the data we deliver.
Real-time processing and display of data allows our customers to make quick decisions based on a reliable data set and adapt their test program as required. This enables a more efficient use of tunnel time creating better value for our customers.
Fully corrected and validated data is transferred to customers
within minutes of completion of each test run. This allows our
customers to analyse their data from the beginning of a test
program.
Assured Security of Model and Data
When testing with us, the security of the model and data is assured; we tailor our security measures to suit our customers’ needs. Upon prior request, our highly experienced IT support team can set up Virtual Private Networks (VPN) to permit remote monitoring of test data by customer teams from within and outside the UK.
Flexibility
We operate a flexible service throughout the year to suit the requirements of our customers; we have considerable experience in delivering test programs with 24-hour running.
Technical Information
Model Attitude:
Incidence range: -10˚ to +20˚
Sideslip range: ±8˚
Model Loads:
Test to CL MAX and beyond into post-stall regime
Test into positive and negative buffet onset
Flow Investigation:
Use oilflow visualisation to investigate surface flow phenomena such as separation bubbles and trailing edge separations
Use high speed pressure transducers to measure unsteady pressures to investigate regions of separated flow
Data Acquisition:
Up to 220 channels measured at up to 10 data points per second
Up to 19 balanced components in addition to the main balance can be installed on the parent aircraft
Measurement of up to 500 steady-state pressures in the rear fuselage and empennage and up to1000 steady-state pressures in total recorded at up to 10 data points per second
