News & Exhibitions
09/11/09 Critical Alignment Measurements Save Lives
FIGHTER AIRCRAFT ALIGNMENT - HARMONIZATION
The Problem:
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The effectiveness of the navigational system of fighter aircraft depends on the accurate alignment of all systems to the aircraft's longitudinal fuselage datum (LFD). This is termed harmonization and is normally maintained using the Taylor Hobson Micro Alignment Telescope. Checks need to be made after a front windscreen change or removal of the nose cone, or following any disturbance to the pilots display unit, platform navigational system or radar mainframe. |
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The Solution:
To allow ground crew to check the harmonization, telescopes and collimators (to provide a line of sight) are mounted in a sighting frame and alignment checking jig. This job is made much easier with the use of CCTV or CCD systems to replace the 'human eye' or provide digital output.
During aircraft construction, the gun pod mounting points are accurately aligned to the longitudinal fuselage datum (LFD) and this then provides the datum. An alignment jig incorporating a Telescope is bolted to the gun pods and an aircraft sighting board incorporating collimators is attached to the front of the aircraft. The inclination of the checking jig and aircraft roll is checked using a clinometer.
The first stage of the harmonization sequence is to align the Longitudinal Fuselage Datum jig (LFD) with the Aircraft Target Board (ATB), to provide an accurate datum. Once this is achieved, the target board is then used to align the Internal Navigational Unit (INU) and Pilots Display Unit (PDU).
Aligning Aircraft Target Board (ATB):
Micro Alignment Telescopes (focused to infinity) are mounted in the Longitudinal Fuselage Datum sighting frame and sighted onto a collimator mounted in the corresponding bracket of the Aircraft Target Board. The frame assembly is then adjusted in elevation and azimuth until the telescope crosslines are centred to the collimator graticules. Any movement after this setting is monitored and error corrected.
Checking Alignment of Internal Navigational Unit (INU):
A telescope is located in the INU sighting jig and aligned to the corresponding collimator on the ATB. Any necessary re-alignment as required is corrected by re-shimming.
Similar procedures are adopted to align the PDU and FLIR.
Harmonization of smaller systems such as handheld antitank weapons have a similar problem of parallelism setting. Here the sighting aid, tracer rifle and missile itself must all be parallel to each other and can be set using autocollimation.
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PERISCOPE ALIGNMENT
The Problem:
Periscopes are the eyes of a submarine. A periscope which is operating in misaligned bearings needs more power in the motors to overcome this resistance. The resultant power surge results in a higher noise level being generated which can be easily detected by enemy search craft.
The periscope is approximately 10 metres in length, approximately 25 centimetres in diameter and is raised, lowered and rotated by hydraulic motors.
The periscope is mounted in a series of bearings located in the submarine fin and pressure hull structure. Alignment of these bearings is critical and any misalignment can result in distortion of the periscope and possible damage to the bearings themselves.
Premature hydraulic motor failure can also occur, due to the extra power demands.
The Solution:
All alignment checks are made with reference to a line central to the bore of the lower bearing, which is located in the submarines pressure hull.
A Micro Alignment Telescope was mounted in an adjustable support plate situated at the top of the submarine fin.
A target mounted in a spider fixture (adjustable target holder) is fitted into the lower bearing bore. A second target is mounted in a second target fixture.
The Micro Alignment Telescope is then focused onto both targets. The other targets are then adjusted to be on this reference line.
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TUBE ALIGNMENT
The Problem:
To provide an easy to operate method of checking the straightness and diameter of torpedo tubes to
within an accuracy of 0.05mm (0.002in). This method also eliminates the use of long, cumbersome plug gauges and the need to dry dock the vessel whilst the checks are carried out.
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The Solution:
The measuring system uses a trolly with central glass target, which is towed along the entire length of the tube. The target is viewed through the micro alignment telescope, vertical and horizontal displacements at preselected points measured and recorded. Simultaneously the tube diameter is measured by means of displacement transducers incorporated in the arms of the measuring head.
Recorded data is used to prepare a graph of the tubes interior profile for comparison with a template which specifies the profile necessary for a torpedo to pass cleanly through the tube.
A CCD camera, with software attached to a laptop, greatly speeds up and simplifies the measurement.
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Alignment and Level Product Range
Taylor Hobson's alignment and level range of measuring instruments consist of optical, mechanical and electronic measuring devices from Micro-alignment telescopes, electronic levels to auto-collimators. These systems are capable of measurement of geometric parameters such as straightness, angle, squareness, flatness and are used in a wide range of applications in a variety of industries from machine tools and aerospace to calibration laboratories.
Autocollimators
Taylor Hobson's autocollimator range come with a number of options, the instruments can be either digital or visual with manual or software data collection. Parameters such as angle, straightness, squareness and paralllelism can be measured with micron or sub second precision allowing alignment and measurement of features such as precision guideways or alternatively angle of indexing tables or spindle squareness.
Electronic Levels and Clinometers
Ranging from high precision bubble levels to precision electronic levels the Talor Hobson electronic levels and clinometers are suitable for a wide variety of appllcations. These devices can measure to sub second accuracy with measurement ranges from 360 degrees and level measurement to 0.1 seconds, enabling measurement of flatness, angle, straightness and more.
Micro-Alignment Telescopes
A popular range of instruments used in industries such as marine, aerospace and many more the micro-alignment telescope provides precision alignment to micron accuracies. These systems are robust, reliable and portable and are suited to measurement in workshop as well as laboratory environments. A full range of accessories ensure versatility to a wide range of applications.
