Who are the 'Calibrators' of Aerial Work Aviation?

Aerial Flight Inspection plays a big part in keeping the aviation world safe, and on course - for example, ensuring ILS approach and other types of navigation aids are reliable and safe. What's the inside track on this sector of aviation? Patrick Ryan explores...

Patrick Ryan  |  27th August 2021
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    Patrick Ryan
    Patrick Ryan

    Patrick Ryan brings over 30 years of experience as a Senior Consultant helping government and business...

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    Flight Calibration Services Aircraft

    How do you know if the ILS approach you are using, or other types of navigation aids, are reliable and precise? The answer is aerial “Flight Inspection.” In this month’s issue of GA Buyer Europe, Patrick Ryan flies you down the glideslope of what this unique Aerial Work sector does and how they keep the aviation world safe and on course.

    If you didn't know, most of the world and the International Civil Aviation Organization (ICAO) member nations are required to ensure their aerospace navigation aids and Instrument Flight Rule (IFR) procedures are accurate and reliable 24/7.

    So, with that, the Flight Inspection sector of Aerial Work aviation is the one and only airborne community that ensures that open skies are truly navigationally safe from takeoff to landing, for every General Aviation (GA), Air Transport, and Aerial Work flight.

    Even with COVID-19 and the slowdown of passenger travel, the demand for flight inspection services has not diminished. In some ways COVID-19 has allowed the Flight Inspection community to pick up the pace of inspecting high traffic airspace, which was challenging to do in standard times — that is, inspecting major international airports’ (e.g., Heathrow and JFK’s) navaids and departure/arrival procedures.

    So, what is this sector of Aerial Work aviation, and how do they get the job done?

    Metaphorically Flight Inspection is like the 5-Ts. In the instrument flying world, many students obtaining their IFR rating are taught the 5 Ts for precisely flying certain types of instrument approaches or entering a holding pattern. The 5 Ts are TIME, TURN, THROTTLE, TWIST, TALK. As with this time-tested instrument approach procedure or technique, the Flight Inspection aviation sector is no different in ensuring every aircraft in the world navigates safely and precisely.

    Time - History

    Starting with time or ‘Hacking your watch,’ the need for Flight Inspection is almost as old as aviation itself. The first Flight Inspection efforts were started in the 1920s by individuals flying surplus World War I aircraft, or Airmail Pilots inspecting a progressively expanding navigation system centered on airway light beacons to provide navigational guidance.

    The arrival of radio navigation technology in the 1930s and 1940s brought an increased importance to flight inspection of these structures. Aerial flight inspection was the only means to evaluate radio transmitters from

    where they were used, i.e., in the air. Expanding on this, with the development of the Instrument Landing Systems (ILS) and Very High-Frequency Omni-directional Range (VOR) stations, flight inspection became an essential or even a critical element to verify the accuracy of navigation infrastructure.

    Fast-forwarding to today, Global Positioning System (GPS) satellites have become the first choice for air navigation and conducting instrument procedures for many flight crews. This change has required the Flight Inspection sector to add to its growing and leading- edge technology inspection service menu.

    Turn - What is Flight Inspection?

    The bottom-line answer is that it is more than inspecting. The Flight Inspection sector inspects, calibrates, and validates many aspects of the navigational aids and airway procedures currently operational worldwide. Thus, Flight Inspection operations consist of ‘measuring’ aeronautical facilities and systems and ‘assessing’ aeronautical procedures and the flying environment.

    Flight Inspection measures the performance of communication, navigation, and surveillance infrastructure of the global airspace system. Moreover, flight inspection assesses all flight procedures such as routes, approaches, and departures. Plus, validation of electronic signals transmitted from ground navigation systems to ensure the reliability and capability of navigational aids without any obstacles. (As a side-note, flight inspection is different from ‘Flight Test’, which analyses aerodynamic and structural safety).

    To accomplish this task, Flight Inspection aircraft and crews fly pre-planned low-altitude profiles. Such profiles could include grids, orbits, DME arcs, tracks, instrument approaches, and low (e.g., down to 50’ AGL) passes along the entire length of the runway (often in the opposite direction of the expected traffic flow). In some cases, they are taxiing around an airport to look for required and readable runway and taxiway signage — from a pilot’s cockpit perspective.

    At controlled airports, these flights typically receive special handling by ATC. However, at non-tower airports, the safe completion of navigation aids inspections depends on pilot awareness and cooperation when “flight inspection or check” is announced over the radio.

    Throttle – Types of Flight Inspections

    When it comes to what the Flight Inspection sector does explicitly, they are involved in several individual tasks that supports everything from the preplanning of new navigation aids to inspecting shipboard Tactical Air Navigation Systems (TACAN). Specifically, the Flight Inspection sector has four distinct types of missions; and these cover more than 17 different navigation systems and procedures that must be overseen.

    General Types of Flight Inspections

    The general types of inspections range from Site Evaluation to Special Inspections. These specific types of flight inspections or missions are:

    Site Evaluation – This type of flight inspection aims to locate appropriate sites for installing new air navigation aids. This evaluation ensures radio frequencies from the planned radio transmitter are transmittable in all directions without distortion by the natural geography and topography of the surrounding area.

    Commissioning – Commissioning missions are flight inspections conducted to analyse and assess the performance of a newly installed air navigation aid system and to establish that the system will support its operational requirements.

    Validation – Following Commissioning is flight validation. Flight validation missions are involved with factors other than the performance of the navigation aid or system that may affect the suitability of the procedure for publication.

    Periodic – A periodic inspection is a regularly scheduled flight inspection to determine that a system meets standards and supports its operational requirements. The periodicity of these inspections can range from around 1,000 down to only 200 days, depending on the type of system or Standard Instrument Approach Procedure (SIAP).

    Special – Special flight inspections are undertaken explicitly for a specific objective or unusual circumstance, such as to assist the inspection of defence forces’ navigation systems when navigation systems have changed, or supporting an aircraft accident investigation.

    Specific Types of Air Navigation Systems & Procedures to Inspection

    The specific types of air navigation systems and flight procedures the Flight Inspection community routinely conducts can vary from inspecting the conditions of runway surfaces to space-based navigation and communication services. However, the standard type of navigation systems and procedures inspected routinely around the world are:

    • Instrument Landing System (ILS) and ILS Markers (Category I, II, and III)
    • VHF Omnidirectional Radio Range (VOR) Beacons and Distance Measuring Equipment (DME) 
    • Non-Directional Beacon (NDB) and VHF Communications & VHF Direction Finding (VDF)
    • Visual Approach Slope Indicator (VASI) and Precision Approach Path Indicator (PAPI)
    • GPS Non-Precision Approach (NPA), and Area Navigation (RNAV, RNP) based on GNSS or DME/DME
    • Surveillance Radar Element (SRE) and Precision Approach Radar (PAR)
    • Precision Runway Monitor System (PRM)
    • Instrument Flight Procedures validation (SID, STAR, SIAP)

    Twist - Aircraft & Systems

    When it comes to aircraft and systems, the Flight Inspection sector utilises a narrow mix of ‘off the shelf’ fixed-wing multi-engine aircraft which are integrated with specialised sensor systems specifically designed for this unique task.


    Regarding fixed-wing multi-engine aircraft, most Flight Inspection organisations will utilise turboprop and small to medium-size business jets. These aircraft types provide better platforms for adding additional electronic systems and antennas (e.g., extra surface space to minimise interference between antennas), and can be adapted to the various configurations required for flight inspection, as well as having the reach and endurance to meet demanding flight profiles and schedules.

    When it comes to turboprop and business jets used in Flight Inspection, the following are some of the common platforms utilised in this Aerial Work sector:

    • Beechcraft/Textron, King Air 200 & 300
    • Cessna, Citation 1-V, XLS+
    • Bombardier Aerospace, CRJ200
    • Hawker Beechcraft, Hawker 800
    • Bombardier Aerospace, Learjet 60 
    • Vulcanair A-Viator

    However, on the other end of the spectrum, helicopters (e.g., AgustaWestland AW109SP Da Vinci, Bell 429, etc.) are utilised in small numbers for certain inspection operations, e.g., validation of Helicopter Flight Procedures and inspection of supporting navigation aids.


    On the systems side of what the Flight Inspection sector utilises, the backbone (outside of additional antennas integrated interference-free across the aircraft’s fuselage) that makes it mission capable is the Flight Inspection System (FIS). In General, a FIS is a self-contained system with a navigation-grade inertial navigation system (INS), a barometric altimeter, a radar altimeter, GPS, and a TeleVision Positioning System (TVPS).

    However, the FIS today goes beyond the basics and provides these specific standard capabilities, and more: 

    • Signal receivers for Flight Inspection and Flight Validation with RF Capture capabilities and RF Interference detection
    • Integration with cockpits from leading navigation systems (e.g., Garmin, Honeywell, etc.) for Flight Guidance & Flight Validation
    • Multi-Mission Map systems mixed with mission information
    • Real-Time study replays and recalculation of data 
    • Tablet data interface via Wi-Fi for onboard multi-users, i.e., for additional Inspectors
    • Real-Time automatic report generation, i.e., high-quality color printouts of flight data and reports
    • Data Link capability
    • Multi-constellation, multi-frequency GNSS position reference systems with the capability of utilising satellite-based correction data services with global centimeter-level accuracy
    • High-performance computers and real-time data acquisition system for accurate timing and calculation of all data

    Talk – Flight Inspectors

    On the human side of flight inspection and validation operations, it consists of a team of dedicated Aerial Work government agencies, companies, and aircrew members. The unique profile of these operators and inspectors are:

    Agencies & Companies

    In this Aerial Work sector, the primary Flight Inspection operators are both government agencies and commercial firms. Regardless of For-Profit or Non-Profit, Flight Inspection organisations or units generally operate the same way with respect to flight operations, training, and certification.

    In recent years and in many countries, the regulatory and service functions of a single national aviation flight inspection entity have been split, and the service function privatised to varying degrees. For example, throughout Europe, the flight inspection function is often conducted by private corporations regulated by the civil aviation authorities. Flight Inspection aircraft and aircrew routinely operate and may even compete for flight inspection work in such airspace.

    Here is a sample of some of the Flight Inspection government agencies and commercial service providers providing inspection services today and not only in their national airspace but around the world at any given time: 


    • Nav Canada
    • US Federal Aviation Administration (FAA)
    • France Service Technique de la Navigation Aérienne – Technical Support (STNA), Service de la Formation Aéronautique – Flight Management (SFA)
    • South African Civil Aviation Authority (SACAA) 
    • And more....

    Commercial Service Providers

    • FCS Flight Calibration Services GmbH – Germany • Radiola Limited – U.K./New Zealand
    • Aerodata AG - Germany
    • ENAV S.p.A. - Italy
    • Grup Airmed - Spain


    In the cockpit, a typical Flight Inspection aircrew profile consists of highly rated Pilot(s) and an Airborne Sensor Operator or Flight Inspection System Operator.

    In the front seat, the experience level of a Flight Inspection or Check Pilot averages between 8,000 and 10,000 Hrs. The minimum requirements for hire include 1,500 Hrs total time, a valid commercial pilot, an Airline Transport Pilot (ATP) certificate with multi-engine rating, and instrument ratings. In some cases, 500 Hr multi- engine time and a type rating in a particular aircraft are required also.

    In the back seat, the skill level of the Airborne Sensor Operator or Flight Inspection System Operator consists of advanced knowledge of navigational and avionic systems, along with the rules and regulations associated with air navigation and flight operations. Additionally, they have a solid understanding of sensor technology and its applications.

    Whether you’re in the front seat or the back, many crew members are required to complete a Flight Inspection course before having the authority to conduct such operations. These courses consist of learning the technical and operational requirements of conducting a check.


    As you can see, the dedicated operators and aircrew members of the Flight Inspection sector ensure the instrument approach procedure of TIME, TURN, THROTTLE, TWIST, TALK is safe and precise.

    Also, the term ‘Flight Inspection’ for this Aerial Work sector is more than that. It consists of checking, calibrating, and validating tangible (e.g., runway signs) to intangibles (e.g., radio signals) of legacy and future air navigation technology, systems, and procedures.

    It goes without saying that the Flight Inspection sector of Aerial Work aviation is a critical element of the aerospace world and the world in general. Devoid of accurate airways, navigation aids, and flight procedures, the aviation community would be stuck in fair-weather ‘Dead-Reckoning’ mode.

    Read More About: Aerial Surveillance

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