Non-calibration elements of flight inpection
Thank you for your replies and forbearance reading my poorly previewed and print-dense posts.
Is it adequate that a flight inspection aircraft is not required to be capable of flying the system, even in good weather?
In order to operate an airport in bad weather an airport operator needs to provide an adequate instrument landing system. This safety critical system has an ICAO safety objective which must be met across the ground installation, the aircraft and the pilot. The airport operator can not offer his equipment for use without a certificate. A certificate can only be issued by an approved organisation.There are recognised anomalies and factors which influence the radiated signal and its effect on the aircraft using the facility.
From CAP 670 ATC Safety Services Requirements. This certificate is issued on the strength of a prearranged flight check at 6 month intervals under ‘calibration’ conditions of weather and traffic. The purpose of this check is to confirm the accuracy of the radiated signal in space meets engineering standards. Reasonable because the base signal radiation pattern has to be correct or the resultant signal in space can not be.
Can this check reasonably be interpreted as meeting the complete industry expectations of safety of performance, to meet the ICAO Safety Objective, under all acceptable non-calibration conditions; be that airport owner and operator, or the users within the airline industry?
I guess it must be, as CAP 670 permits this inspection by an aircraft which is not required to be capable of using the ILS to Catll or Catlll standards even in good visibility - let alone have an autopilot.
CAP 670 (My italics, bold and underline.)
Annex 1 - Instrument Landing System
5 Aircraft
5.1 Manual flight control using only the mandatory navigation instruments is not considered sufficiently accurate for inspection of the following types of ILS:
• Category III systems.
• Category II systems.
• Category I systems, which the operator wishes to use for autoland in good visibility.
5.2 For inspection ofthe above systems the aircraft shall be fitted with equipment which will providerepeatable following of the required path (1549). Systems considered suitable to this purpose include telemetry of the ground based tracking system’s output to a separate instrument in the aircraft, OR anautopilot. If an autopilot is used the CAA shall be satisfied that it is capable of safe operation down to 50 feet above the threshold elevation (1550).
I have no concerns about the measurement of transmitted signal accuracy (other than post-accident) but not sure how matters such aircraft stability and attitude at the threshold, acceptability of bends and control motion noise etc. are determined. All are cited as factors in the chain between transmitter and an acceptable installation. Maybe this is met by some other agency and some other way but if so where does it fit into meeting the safety objective?
I believe there used to be random checks with inspection aircraft just fitting unannounced into the traffic system and sampling the facility. This concept seems to have gone - probably for commercial reasons - but it would offer a measure of reasurance.
How are the requirements of a post accident or incident to be met as specified – let alone with the added disruption possibly caused by the accident itself - and how and by what standard is the ILS deemed safe for operational use? One fatal accident in 10,000,000 landings is the required safety objective.
I am just SLF and curious. Reassure me please.