Hunting Vies for Calibration Contract

Australia, like the UK and other areas of the world, has three categories of instrument landing systems (ILS). A Category 1 system directs an aircraft to apoint not less than 200 feet above the runway with appropriate visibility limits. A Category 2 system can conduct an aircraft down to not less than 100 feet above the runway with lower visibility limits. Category 3 systems are the most sophisticated and can guide an aircraft ‘blind’ to near zero visibilities and lower heights, even to touchdown. As yet, Australia has no Category 3 systems operating at any of its airports though Canberra does possess an MLS.

The ILS system which guides an aircraft to a safe landing transmits two beams into the sky from a runway location. The first beam is called a localiser and its job is to guide the aircraft by showing its position in relation to the runway centreline. The beam tells the pilot whether the aircraft is left or right or online with the runway centre. The second beam or glidescope gives the pilot the aircraft’s height above the runway and guides the aircraft to the point 200 feet above the end of the runway or on to the runway itself.

Naturally, those systems and other navigation aids are required by law to be checked periodically to ensure that they are transmitted in the correct direction and at the correct strength.

It is this process, known as flight checks or flight calibration, that Hunting developed its Navcal system to perform. Generally, the Navcal system has done the job at a lower cost that its competitor systems.

In fact, the Hunting system has received UKCAA approval to calibrate Categories 1, 2 and 3 Instrument Landing Systems. Previously, the UK CAA had done all airfield calibration itself. Hunting now has flight calibration contracts with more than half the UK airports using ILS, and has recently undertaken flight calibrations in the Netherlands and the Republic of Ireland. The company is also vigorously pursuing other overseas markets, not the least of which is Australia.

The Development of the Navcal System

The Navcal System started life as a result of a fresh approach to the calibration of ground based navigation aids by a sister company in Hunting’s Defence Division, Hunting Communication Technology. The system was passed on to Hunting Aviation Services whose management could foresee the potential for the Navcal system. Research showed that demand outstripped supply for the service currently being offered solely by the CAA in the UK and the chance to expand was taken up.

Without the UK Authority’s approval the project was a nonstarter and no service could be offered in the UK. The idea of a private contractor competing with the licensing Authority itself was a novel concept and one which at the time caused considerable surprise in certain circles. However, encouragement was received which resulted in Hunting funding further development work to refine the system.

Hunting’s prime objective was to design a low cost system to take advantage of the decreasing costs of Global Positioning Systems (GPS) or satellite navigation. In keeping with this low cost philosophy, it was also decided to adopt an optical ground tracking system. During the ILS calibration process the calibration aircraft is visually ‘tracked’ towards the runway. The optical ground tracking system utilises recent developments in Charged Coupled Device (CCD) camera technology.

Unlike some semi automatic systems currently available, the Navcal system was designed from the outset to be used as a tool by the navaid inspector flying in the aircraft, thus allowing immediate analysis of ground navigational faults. This was deemed to be essential for landing aids set in remote locations where infrequent calibration visits and the lack of sophisticated facilities would require on the spot analysis and adjustment.

So How Does the Navcal System Work?

The system is operated by a ground operator who, stationed at the end of the runway, views a light source on the approaching calibration aircraft through an electric theodolite coupled to the CCD video camera. The camera’s computer calculates the angle of the approaching aircraft which is then transmitted by UHF datalink. The same computer system also controls the ground based GPS receiver to store, at very short intervals, positional data which is used in postflight processing of data generated in the aircraft.

The aircraft, crewed by two pilots and a navaid inspector, is equipped with a number of radio sensors, a computer, and a chart recorder to log the output of these sensors. The onboard computer is used to collect the output of the sensors and to record the positional data from the aircraft’s GPS receiver. The aircraft’s UHF receiver collects data from the chart recorder via the onboard computer. Both the ground and air computers are synchronised by use of the GPS satellite atomic clocks. As all information collected by the computer is time marked and coordinated to the same time base, postflight information can be later fed into the chart recorder to produce duplicate charts. This information can also be fed into a colour plotter to identify specific problems encountered during a calibration.

Because the Navcal system is reduced in size and weight, it can be fitted into a PA-31 Piper Navajo Chieftain or similar type of aircraft. And the modular system permits quick installation and easy removal when not required, allowing the aircraft to be used for other purposes.

Has the Customer Benefited?

The introduction of competition in the UK flight calibration market has resulted in a lowering of prices to the airfield operator by some 40 to 50%. This has been an important and welcome reduction in price, especially to regional airports where the cost of flight calibration is often one of the biggest budgetary line items. This significant cost reduction is the usual result when a commercial approach is adopted and has been confirmed by the considerable market research undertaken by Hunting.

Naturally, Hunting is keen to offer its services and the ensuing reductions to other areas of the world.