altitude test

							ALTITUDE TEST FACILITY Smiths Aerospace Components - Burnley Limited

DEVELOPMENT AND QUALIFICATION TESTING OF GAS TURBINE ENGINES AND ASSOCIATED EQUIPMENT AT SIMULATED ALTITUDE CONDITIONS

DAVID ROYDS BA (HONS) SENIOR PROJECT ENGINEER ALTITUDE TEST FACILITY

INTRODUCTION The complexity of modern gas turbine engines has, to a large extent, been brought about by the quest for greater thrust from lighter, more fuel efficient and environmentally friendly aircraft propulsion systems. During the development stages of such systems, it is essential to test and evaluate their performance at predetermined operating conditions of altitude pressure, temperature, climate etc. In the early years of aero gas turbine development, the normal method of testing engines at altitude conditions required the use of aircraft which had been modified to act as flying test beds. However, after witnessing tests carried out in a German test plant in Munich in the late 1940’s, Engineers from Joseph Lucas Ltd. began work on the design of a High Altitude Test Facility to be built at a site in Burnley, England. By March 1953 the plant was fully operational and today, after almost fifty years of continual development and constant modernisation, the Altitude Test Facility is operated on a fully independant commercial basis by Smiths Aerospace Components - Burnley Limited. This Paper gives a brief description of the Facility in it’s present form and also describes several of the commonest types of test which are carried out within it.

January 2004

ALTITUDE TEST FACILITY Smiths Aerospace Components - Burnley Limited
TEST PLANT OPERATION, TEST CELLS & CAPACITY

COLD AIR PLANT
The most fundemental requirement of any test is the delivery of air to the test item at the required conditions of pressure, temperature, air mass flow etc. In particular, the air must be supplied to the test cell with a dew point which is low enough to obviate the formation of ice. This is achieved by delivering the air via the Cold Air Plant (CAP). Figure 1 shows an overall perspective view of the Altitude Test Facility (ATF) , whilst Figure 2 is a schematic diagram showing the main components of the Facility. The values of pressure and temperature shown in Figure 2 are typical of those which would be found during a test carried out at 50000 ft and 210K. The air is drawn into the CAP via an air inlet filter bank (1) by the Reavell seven stage centrifugal compressor (2) which is fitted with inter and after coolers. On exiting the compressor, the air is at a pressure of 550 kPa abs. at a temperature of approximately 300K. The Air Mass Flow (AMF) is continuous at around 3.0 kg/s , thus allowing the 932 kW motor which drives the compressor to run at a constant speed of 9800 rpm.

2

From the compressor, the air then passes through a refrigeration drier (3) and one of two pairs of absorption driers (4) , thus reducing the moisture content of the air, which is now at a pressure of 480 kPa abs. and a temperature of 280K. Each pair of driers is capable of approximately 8 hours of continuous running before requiring reactivation, at which time the previously reactivated pair can be brought on line. After the drying stage, the air passes through the primary and secondary expansion turbines, both of which are single stage axial turbines driving centrifugal brake impellers. The primary turbine (5) is normally operated at a choked condition and when it is running at the maximum speed of 25000 rpm the temperature of the air is reduced to 220K. The secondary turbine (6) has a maximum speed of 14000 rpm which further reduces the air temperature to the minimum achievable value of 200K. The actual temperature at outlet from the turbines is determined by the positions of the turbine by-pass control valves. The AMF which is delivered to the test cells is controlled by the position of a 500mm by-pass valve (7) which allows any unwanted air to be diverted directly into the plant exhaust system. The final temperature at which the air enters the test cell in use can then be precisely set by means of the 180 kW heater (8). The air can be directed to either of the two test cells by simply blanking off the entry and exit ducting in the unrequired cell. It is normal practice to build test rigs in the dormant cell whilst testing is carried out in the other.

TURBOCHARGERS PRIMARY TURBINE FILTER & REAVELL COMPRESSOR FRIDGE DRIER 1&2 3 4 5 ABSORPTION DRIERS BY-PASS SECONDARY TURBINE 6 EXTRA AIR SUPPLY ALTITUDE CONTROL VALVES DERWENT 11 MAIN GAS COOLER 13 NENE 14 15 INTER COOLER 16

18

DRIERS 17

7 500mm BY-PASS VALVE 8 HEATER 9 & 10 TEST CELLS

PRESS (kPa abs)

BY PASS 550 480

100 0

100 12 900 12

37

100 30

TEMP (K)

525 470 290 300 275 280 220 0 260 320 200 210 320 470

290

290

Fig 2

Typical ATF Operating Conditions for a Test at 50000 ft and 210K

3

ENGINE TEST CELL
The Engine Test Cell (ETC) (9) is a large vacuum chamber, 12m long and 4m in diameter, with a removable door 2.6m in diameter to allow easy access for the installation of engines and test equipment. A combined hoist and runway system, with a maximum capacity of 5 tonnes, is used to install the test item into the cell, where it is transferred to a large hydraulic platform (1.2m × 5m) and locked into the required position. A small air lock in the side of the ETC is used to gain access to the chamber once the main door has been fitted and sealed. Fig 3 shows a cross section of the ETC.

FULL CELL DIAMETER APPROXIMATELY 4m.

OVERHEAD RUNWAY ALONG THE FULL LENGTH OF THE TEST CELL. (TWO MOBILE HOISTS, EACH OF CAPACITY TWO TONNES)

ACCESS DIAMETER WITH THE MAIN DOOR REMOVED IS APPROXIMATELY 2.6m

NB. APPROXIMATE SCALE 25:1
APPROX. 1m THE RAILWAY AND CARRIAGES USED FOR THE INSTALLATION OF TEST RIGS HAVE A MAXIMUM CAPACITY OF 5 TONNES.

APPROX. 0.75m

CARRIAGES OF VARIOUS LENGTHS ARE AVAILABLE ALLOWING TEST RIGS TO BE WHEELED INTO POSITION OVER THE HYDRAULIC PLATFORM. REMOVAL OF THE CARRIAGE WHEELS THEN ALLOWS THE REQUIRED TEST HEIGHT TO BE SET. APPROXIMATELY 1.6m

Fig 3

CROSS SECTION OF THE ENGINE TEST CELL

COMBUSTION TEST CELL
The Combustion Test Cell (CTC) (10) is an open test cell measuring 8.2m × 3.7m × 6.1m high. The equipment under test in the CTC is normally coupled directly into the approach and exhaust ducting, although a small portable test chamber is available which enables small engines to be tested in this cell. The portable chamber measures 1.5m in diameter and is 2.4m long.

4

EXHAUST EXTRACTION, ALTITUDE CONTROL & ATF CAPACITY
Exhaust Extraction After leaving the test cells, the exhaust gases mix with any by-passed air before entering the Main Gas Cooler (11) where the mixture is cooled to approximately 320K by passing it over tubes supplied with water from the main plant cooling system, which is in turn cooled by means of Cooling Towers (12) situated on the roof of the ATF. The air/gas mixture then passes through the altitude control section (13) , which consists of three butterfly valves with diameters of 760mm , 305mm & 150mm installed in parallel in the plant exhaust ducting. The manner in which these valves allow the pressure in the test cells to be reduced to the required level will be explained momentarily, following a description of the two plant extraction blowers. After passing through the altitude control valves, the exhaust gases arrive at the first extraction blower (14) , which is a compressor from a Rolls Royce Nene Turbo-jet Engine. The Nene is driven by a 933 kW electric motor and has the capacity to flow a maximum of 3.75 kg/s at a compression ratio of 3.3 : 1. When the gas mixture exits the Nene exhauster, the temperature has been increased to approximately 470K by the action of the compression cycle and this must be reduced to a value similar to that achieved at outlet from the main gas cooler. This reduction to around 320K is made possible by means of an Intercooler (15) positioned between the Nene and the second extraction blower. The second extraction blower (16) is a compressor from a Rolls Royce Derwent Turbo-jet engine which is driven by a 1120 kW electric motor. The Derwent is capable of passing 5.5 kg/s at a compression ratio of 2.5 : 1. It can be seen from the above figures that the two exhausters acting in series have a combined compression ratio of (2.5 × 3.3) = 8.25 : 1 which, taking Standard atmospheric pressure to be 101.35 kPa abs. gives them the capacity to exhaust at atmospheric pressure from a minimum altitude pressure of 101.35 ÷8.25 = 12.28 kPa abs. which is equivalent to an altitude of approximately 50000 ft. Altitude Control As indicated previously, the altitude pressure in the test cell is set by adjustment of the three altitude control valves which are located just upstream of the plant exhausters. To understand why the restriction which these valves produce should reduce the upstream pressure in this way, it must be remembered that the primary turbine in the CAP is operated at a choked condition. As a consequence, the total air mass flow upstream of the altitude control valves is constant and, since the basic relationship for sub-sonic flow across a restriction is given by ....

5

M = Ae Kgρ∆P

where:

M = Air Mass Flow Ae = Effective area of the restriction K = Constant dependant upon the units used g = Acceleration due to gravity ρ = Density of the air ∆P = Pressure drop across the restriction

..... then it can be seen that a decrease in the effective area (Ae) leads to an increase in the pressure drop across the restriction (∆P). Hence, because the inlet pressure to the plant exhausters is held constant, the resulting change in the ∆P can only be accommodated by a lower pressure upstream of the control valves. ATF Capacity In practice it is not always necessary to operate both exhausters. Since the Derwent exhausts to the atmosphere at a theoretical standard pressure of 101.35 kPa abs. and it has a compression ratio of 2.5 : 1 , then it has an inlet pressure requirement of (101.35 ÷ 2.5) ie. 40.5 kPa abs. which equates to an altitude of approximately 23000 ft. Hence, any tests requiring an altitude pressure which is greater than 41 kPa abs. can be carried out using the Derwent exhauster alone, with the Nene being by-passed. When the required pressure is below 41 kPa abs. however, the Nene exhauster must also be used as described previously. Although the maximum AMF which can be delivered by the CAP is approximately 3.0 kg/s (depending upon the prevailing amospheric conditions), this figure does not represent the maximum AMF that can be achieved. As previously stated, the Nene exhauster has a maximum capacity of 3.75 kg/s , whilst the Derwent requires a flow of 5.5 kg/s at all times. Normally, when both exhausters are running, the Derwent draws any extra air that it requires directly from the atmosphere via a bleed line on the Intercooler. However, when the test altitude is low enough to require only the Derwent exhauster, up to 2.5 kg/s of extra air can be induced into the system upstream of the test cells, directly from the atmosphere, thus increasing the maximum AMF to around 5.5 kg/s. Extra air supplied by this method cannot be dried or cooled, but the Plant has the capacity to induce up to 1.4 kg/s of extra air into the system via a bank of driers (17) and turbochargers (18), before it merges with the supply from the CAP at a point just downstream of the secondary turbine. The turbochargers have the capability to reduce the temperature of this extra air to approximately 235K.

6

Even when both exhausters are running, the 3.75 kg/s capacity of the Nene exhauster means that it is still possible to induce up to 0.75 kg/s of extra air through the test cells. It should be noted however, that the ability to induce extra air into the system in this way decreases with increasing altitude. In effect, it is posible to maintain a maximum flow of 3.75 kg/s at any pressure in the range 41 kPa abs. to 18 kPa abs. (23000 ft to 40000 ft). At pressures below 18 kPa abs. down to the plant minimum of 12 kPa abs. (40000 ft to 50000 ft), the maximum AMF gradually reduces to the 3.0 kg/s delivered by the CAP. Whilst the ability to induce extra air into the system in this manner is advantageous in terms of AMF capability, there are certain disadvantages. Firstly, if tests are being carried out at very low temperatures, problems with humidity may be encountered and it is often necessary to monitor the dew point of the air supply carefully when extra air is being drawn into the system. Secondly, at temperatures below 235K, the addition of extra air to the CAP supply may have the effect of increasing the temperature of the total AMF. To compensate for this, the temperature of the air delivered from the CAP must be reduced, thus increasing the minimum air inlet temperature which can be acheived. Whilst neither of these phenomena normally cause any problems, it is as well to bear their limiting effects in mind when preparing a test schedule.

FUEL SUPPLY SYSTEMS
A comprehensive network of pumps, heaters, coolers and by-pass lines can be used to supply a wide variety of fuels to the test cells from any one or more of four header tanks located in a blast proof fuel room. Fuel flow measurement is carried out using Coriolis metering systems.

INSTRUMENTATION
Located between the two test cells and directly below the Main Control Room is the Test Instrumentation room.This room contains the temperature controlled transducer cabinet and National Instuments Data Logging System which allows measurements and signals to be transmitted to the Main Control Room. A wide range of thermocouples, orifice plates, nozzles, resistance thermometers, Pitot tubes etc. are available for use on test installations.

DATA LOGGING
Data logging is carried out using a National Instruments based Modular Acquisition System with Lab View software. Fast transients, such as exhaust temperature measurements, are logged using a high speed NI-PXI system with 64 channels and 16 bit resolution. The acquisition rate for each channel is up to 300 kHz , but for most purposes the system is set to sample data from each channel at 10 kHz to provide a cleaner signal.

7

A further 50 channels are currently available for the measurement of steady state readings such as air inlet temperatures and pressures, but the modular design of the Data Logging System means that this figure can be readily expanded if required.The signal input bandwidth is 3 Hz and the low speed measurements are made using an Ethernet configuration which is completely seperate to the high speed NI-PXI system. The scanning rate for steady state readings is 10 kHz per channel General The test data is stored in the ‘Comma Seperated Variable’ format (CSV) as this is the most readily accepted format for information transfer. Access to the test results may be obtained via a Client Computer on the local ATF Data Logging Network and this Station is available for the Customer’s use during testing. Access to the Internet and an email facility with file compression software allow data to be transferred electronically by the Customer if required. The test data is normally written to CD for long term storage.

VIDEO SYSTEMS
The ETC is equipped with a dedicated video camera/recorder with remotely operated pan, tilt & zoom controls. Three TV monitors and video recorders allow observations and recordings to be made from any of several other camera mounting positions available in both of the test cells.

ENVIRONMENTAL & SAFETY CONSIDERATIONS
Environmental Considerations To comply with the latest environmental requirements, an Afterburner has recently been installed on the roof of the ATF through which the exhaust gases are passed in order to remove all traces of unburnt fuel. Safety Considerations Because of the inherent risk of a fire during testing, banks of CO2 bottles are located at strategic points within the test cells, fuel supply chamber and the main plant. Any area which is affected by fire can flooded with CO2 gas, thus starving the fire of oxygen. In addition, any fuel in the header tanks, which are located in the fuel chamber, is automatically dumped to a holding tank situated outside the test facility.

8

CONTROL ROOMS
Located in the centre of the main plant is the Facility Control Room from where the Cold Air Plant, altitude valves, 180 kW heater etc. are operated. Instructions as to the requirements for a test are relayed to the Plant Engineers from the Test Engineers in the Main Test Control Room via an intercom system. Figure 4 shows the Main Test Control Room.

Fig 4

The Main Test Control Room

9

ATF TEST PROCEDURES
IGNITION TESTING
Normally carried out in the Combustion Test Cell (CTC), Ignition & light-round tests on aero engine combustors provide useful information on the performance of combustion system designs at altitude conditions, particularly during the development stages. Such evaluations are made by carrying out tests which allow a performance graph of Fuel/Air Ratio (FAR) versus Air Mass Flow (AMF) to be drawn up for any given altitude pressure and air inlet temperature conditions. Figure 5 shows a typical graph resulting from tests to determine the location of a 10 second ignition boundary and the weak extinction boundaries for a combustion system. Note the use of the terms Heel, Toe and Sole which have evolved because of the characteristic shape of these boundaries.

0.0500

Fig 5

Typical Ignition & Stability Test Results

0.0450

0.0400

IGNITION BOUNDARY
0.0350

FUEL / AIR RATIO

0.0300

HEEL
0.0250

SOLE
0.0200

TOE
0.0150

0.0100

STABILITY BOUNDARY
0.0050

1.00

2.00

3.00

4.00

5.00

AIR MASS FLOW (kg/s)

Ignition & Stability tests would usually be performed at several different altitude pressures in order to gain an understanding of the behaviour of the test article throughout it’s likely operating envelope.

STABILITY TESTING
Combustion stability tests are often carried out at the same time as Ignition & light-round tests. Two different types of combustor extinction are normally investigated - Weak/Rich Extinctions and Velocity ‘Blow off’ Extinctions.

10

Rich or Weak extinction tests must begin from a test point at which stable combustion can be acheived. The fuel flow to the unit is then gradually reduced (Weak extinction) or increased (Rich extinction), whilst the AMF and altitude pressure are held constant, until combustion ceases. The FAR at which extinction occurs is then calculated. Velocity ‘Blow off’ Tests must also begin from a stable test point, but in this case the air mass flow to the unit is gradually increased, whilst the fuel flow and altitude pressure are held constant until combustion ceases. The FAR at which extinction occurs is then calculated. As with ignition and light-round tests, the results are plotted on a graph of FAR versus AMF for each given combination of altitude pressure and air inlet temperature.

EFFICIENCY TESTING
By placing a restrictor plate af known effective area in the exhaust section of a combustor it is possible to obtain data from which combustion efficiency can be calculated. Several pairs of upstream total and downstream static pressure measurements are made in order to determine the conditions on either side of the restriction and from these the efficiency of the combustion can be determined.

ENGINE STARTING TESTS
The most fundamental type of test which is carried out on a full engine system in the ATF is an assessment of it’s starting capability. Such tests are performed in the Engine Test Cell (ETC) and a typical installation is shown in Figure 6.

ENGINE AIR INLET LINE OMITTED FOR CLARITY

ROTARY VALVE

WATER WATER SUPPLY HOLDING LINE TANK

WATER RETURN LINE

FUEL PUMPS

FUEL TANK CAMERA

ENCLOSED ENGINE CAMERA

AIT FUEL TANK, COOLING LINES AND ENGINE SUPPLY LINE EXHAUST CAMERA EXHAUST GUIDE

BUTTERFLY VALVE CAMERA AIR SUPPLY VIA REGULATOR PRESSURE RELIEF VALVE DYNAMOMETER WATER RETURN LINE DYNAMOMETER TORQUEMETER

TO PLANT EXHAUST

FUEL COOLING COIL IN THE BY-PASS LINE SLIP JOINT TEST ENGINE IN INSULATING ENCLOSURE

BY-PASS LINE

FLYWHEEL

ENGINE AIR INLET LINE

SIDE ACCESS DOOR

TEST PLATFORM AND ENGINE STAND HYDRAULIC PLATFORM

FROM COLD AIR PLANT

BELLOWS

WATER SUPPLY TANK

DYNAMOMETER WATER SUPPLY LINE

Fig 6

A Typical Engine Installation

11

Two important points should be noted regarding this installation. Firstly, although the entire test chamber is evacuated to simulate the pressure conditions found at any given altitude, the incorporation of the rotary and butterfly valves into the pipework allows the pressure at inlet to the engine to be varied. By means of these two valves therefore, it is possible to create a ram pressure at inlet to the engine and more closely simulate the conditions which the engine would meet in flight. Secondly, the fuel supply to the engine is from an auxilliary fuel tank which is located inside the test cell. This fuel tank is pressurised relative to the cell static pressure, using nitrogen as the pressurising medium, and is replenished from header tanks between tests. Engine starting tests are often carried out following a prolonged cold or hot soak of the engine and fuel at a predetermined temperature. The exact nature of the conditions at which a test is to be performed is a matter for the particular customer and the various Aviation Authorities to decide. Control of the engine during the tests is normally left to the customer and in many cases the customer will also supply and operate their own data acquisition systems. However, the ATF is fully equipped to carry out any data logging requirements for a customer, if they so desire.

PERFORMANCE TESTS
The ability of an engine to start and/or restart at the conditions of pressure and temperature associated with a given altitude within it’s flight envelope is obviously of great importance. However, since the function of an engine is to deliver sufficient power to carry out the required tasks under all possible extremes within that flight envelope, it is essential that it’s capacity to produce and maintain that power be proved. In order to carry out performance tests designed to measure an engine’s ability to operate adequately, the ATF is equipped to provide controlled loads on an engine, by such means as a Froude water brake or electrically, via a resistance load bank. Figure 7 shows a typical load cycle for an engine performance test.
30

ELECTRICAL LOAD (Kw)

25

Fig 7

A Typical Load Cycle for an Engine Test

20

15

10

5

20

40

60

80

100

120

140

160

180

200

220

240

260

280

300

320

340

360

TIME (s)

12

ICING TESTS
It is not enough that an engine should be able to start, restart and perform adequately at the conditions of temperature and pressure found within it’s proposed flight domain. It is also of vital importance that the engine and it’s systems be able to demonstrate a satisfactory ability to cope with all the possible environmental factors which might be encountered within it’s operational range. Of particular interest is the ability to withstand the formation of ice. The minimum acceptable requirements are laid down in the Federal Aviation Regulations (FAR) and the Joint Airworthiness Requirements (JAR). Figures 8 & 9 are copies of graphs taken from FAR 25 Appendix C, which show the minimum performance requirements for intermittant and continuous maximum icing conditions. In the ATF, icing tests are carried out by incorporating a specially designed Water Spray Mast System into the approach ducting. The Spray Mast is equipped with seven spray nozzles which allow the required droplet size to be acheived by injecting a controlled amount of water through a central hypodermic tube in each nozzle, whilst at the same time passing atomising blast air through an annular gap surrounding the central tube. For any given water flow, it can be shown that the mean size of the supercooled water droplets which are created, is dependent on the pressure of the atomising blast air. As Figures 8 & 9 show, the size of the

Fig 8
( g/m 3 )

INTERMITTENT MAXIMUM (CUMULIFORM CLOUDS) ATMOSPHERIC ICING CONDITIONS LIQUID WATER CONTENT v MEAN EFF. DROPLET DIA.
3.0 1) ALTITUDE RANGE 1.22 to 6.71 km 2) HORIZONTAL EXTENT STANDARD DISTANCE OF 4.82 km

LIQUID WATER CONTENT

2.5

2.0 POSSIBLE EXTENT OF LIMITS AIR TEMP. 0 0C -10 0 C -20 0 C -30 0 C -40 0 C 15 20 25 30 35 40 45 50

1.5 1.0

0.5

0

MEAN EFFECTIVE DROPLET DIAMETER (um)

water droplets used during an icing test is of particular importance. The amount of water flowing to each of the nozzles is individually controlled, allowing precise regulation of the spatial distribution of the water droplets to be achieved. All seven, or just a selected few of the nozzles may be used, depending upon the total water flow requirements of the test and on the distribution pattern specified.

13

Prior to the start of an icing test programme, the Spray Mast system must be calibrated to produce the correct droplet sizes and distribution patterns required for each set of test conditions.

Fig 9
( g/m 3 )

CONTINUOUS MAXIMUM (STRATIFORM CLOUDS) ATMOSPHERIC ICING CONDITIONS LIQUID WATER CONTENT v MEAN EFF. DROPLET DIA.

LIQUID WATER CONTENT

0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0C -10 0 C -20 0 C -30 0 C 15 20 25 30 35 40 AIR TEMPERATURE 1) ALTITUDE RANGE SL to 6.71 km 2) MAXIMUM VERTICAL EXTENT 2.0 km 3) HORIZONTAL EXTENT STANDARD DISTANCE OF 32.2 km

MEAN EFFECTIVE DROPLET DIAMETER (um)

The number of nozzles to be used and the total water flow requirements for each test are determined from the liquid water content, the air mass flow and the distribution pattern prescribed. The approach ducting, including the Spray Mast, is built up in exactly the same configuration as is to be used during the actual testing, but a wire mesh is placed in the same plane which the test article will occupy during the real test. Just upstream of the this plane, a Malvern Laser Droplet measurement system is installed in order to determine the size of the droplets produced. The procedure used to carry out the calibration is as follows: 1) 2) 3) 4) The correct air inlet temperature, air mass flow and cell static pressure conditions are set. The nozzles to be used are selected and the water flow requirements are set. A nominal blast air pressure is applied to the nozzles and the resulting droplet size is measured. The blast air pressure is adjusted, either up or down, and the new droplet size is measured.

14

5) 6)

The process is repeated until the required droplet size is obtained. The wire mesh is cleared of ice and water droplets of the correct diameter are sprayed onto it for a period long enough to allow the distribution to be observed and photographed.

This procedure is repeated for each set of test conditions at which icing tests are to be carried out. After each calibration run, the settings used to obtain the required droplet size are noted so as to be able to recreate the same results during the actual test. The droplet sizing equipment is then removed from the test cell and the test article is installed.

Fig 10

Close up View of the Spray Mast showing the seven Atomising Spray Nozzles

15

It is important that the humidity of the air supply is kept at a level between 90% and 100% at all times during calibration and testing. Too low a value of humidity will impede the formation of ice, whilst too high a value can result in an excess of ice being deposited. In order to acheive this, the humidity is constantly sampled and, if required, steam is injected into the air supply at a point just upstream of the Spray Mast. The length of time taken to complete an icing test is calculated to satisfy the requirements laid down by the FAR and JAR, but a typical test would last for around thirty minutes. It is normal practice in the ATF to install video cameras in the test cell to enable the build up of ice to be observed and recorded during the test. A remotely triggered 35mm camera can also be used to keep a record of the formation of ice at predetermined intervals if required. ALTITUDE TESTING OF ANCILLIARY EQUIPMENT The ATF can also be used to test any equipment which may have to operate at altitude conditions. Typicle examples are fuelling probes, anti icing systems and particle seperators, but a wide variety of aviation systems can and have been tested. In the 1980’s the ATF was used to evaluate the performance of the burners which were used to power the hot air balloons in which Richard Branson and Per Lindstrand made their Atlantic and Pacific ocean crossings. Further information is available on request from: Mr John Riley AltitudeTest Facility Manager Smiths Aerospace Components - Burnley Limited 1 Bentley Wood Way Network 65 Business Park Hapton Burnley Lancashire England BB11 5TG Tel: +44 [0] 1282 429310 Fax: +44 [0] 1282 429310 eMail: john.riley@smiths-burnley.com www.smiths-aerospace.com