1.0. 
2.0. 
sheet 1. 
Introduction 
By definition, close-range photogrammetry is confined to 
Objects within the range of a few centimeters and about 300 
meters. The work described in this paper lies within this 
definition and uses High Energy X-rays. 
The system used at Rolls Royce is based upon an 8 Mega- 
volt Radiographic Electron Linear Accelerator manufactured 
by Radiation Dynamics Limited, of Swindon, England, (Fig. 1). 
This equipment is transported in a custom built Linear 
Accelerator Control and Transport Vehicle (LCIV) and shuttles 
between specially prepared gas turbine engine test sites at 
Bristol, Staverton, Coventry, and Nottingham. The gas turbine 
engines to be radiographed are supplied to these sites by the 
Rolls Royce Bristol and Derby Engine Groups, Helicopter Engine 
Group at Leavesden and the Industrial and Marine Gas Turbine 
Division at Ansty. 
The accelerator is mounted within the engine test cell on 
a simple structure capable of four degrees of freedom, which 
is transported from site to site within the LCIV. 
High Energy X-rays are emitted from the accelerator, pass 
through the engine on test and are imaged on either film (stored 
image), or on a real time X-ray Television System. The infor- 
mation so obtained is then transferred to the Photogrammetry 
Laboratory for subsequent analysis and evaluation. 
Problem. 
For years, the development and testing of aero gas turbines 
has been hampered by the inability of development and test 
engineers to perceive and readily measure the positional changes 
of static and moving metal components within the engines, due to 
the opaque nature of the engine casing walls. 
Historically, the measurement of these clearances, particu- 
larly at the tips of compressors or turbines, has been carried 
out using abradable probes and, more recently, by electronic 
proximity probes, 
The difficulty with all these types of instrumentation is 
the requirement for special engine allocation and modification, 
i.e. special engine builds. They are often difficult or costly 
to install. 
with the introduction of high strength materials and the 
thinning of engine structures and, as the performance require- 
ments have become more demanding, small component movements 
during engine handling have become more important. This is 
particularly true in areas where the airflow has the greatest 
work potential such as the tip and root seals of the high 
pressure turbine and the tip and root seals of the final com- 
pressor stages.