What a Regulator Actually Accepts as Evidence

The clause you are looking for is probably not there

Airport operators ask us a version of the same question every week. Where does it say that this measurement method is accepted. They expect a paragraph number, a line in an annex that names an instrument. They go looking, find nothing, and conclude that the method must therefore be unacceptable.

That conclusion is wrong. So is the opposite one. In most states the rules do not name instruments at all. They set out what the equipment on the airfield has to do, and they require the aerodrome to demonstrate that it does it. How you demonstrate it is a separate question with a separate answer, and that answer is largely yours to propose and your authority’s to accept or refuse.

This post describes how that process actually works. It does not tell you what your authority will decide. We cannot know that, and neither can anyone selling you a service.

A standard is not a means of compliance

Two different things both get called compliance, and confusing them causes most of the trouble.

The standard is the requirement itself. ICAO Annex 14 says what a visual aid has to achieve: the angles, the beam characteristics, the colours, the physical placement. The SARPs framework makes these binding on contracting states, subject to filed differences, and states then write them into national law.

The means of compliance is how you show the requirement is met. That is a different document, usually a softer one. In Europe it is the Acceptable Means of Compliance and Guidance Material attached to the aerodrome rules. In the United States it is largely the FAA advisory circular system, which by its own definition provides methods and practices acceptable to the Administrator rather than creating a requirement.

The gap between the two layers is deliberate. A standard that named a specific instrument would freeze the technology of the year it was written. So the standard describes the outcome, and the means of compliance describes one accepted way of reaching it, while leaving the door open to others.

Most of what a regulator inspects sits in the bottom row. The authority is not usually checking your instrument against a list of approved instruments. It is checking whether you did what your own manual says you do.

Who decides, and why the answer moves across borders

ICAO does not certify your inspection method. It sets standards for states. Your national regulatory authority is the body that grants and keeps your aerodrome certificate, and it decides what satisfies it.

That means the answer genuinely differs by state, and sometimes by inspector. A method routinely used at one European aerodrome can be an open question one border away. There is no international register of accepted inspection methods to appeal to. Under the European rules there is at least a formal route: an aerodrome operator that wants to use an alternative means of compliance describes it to the competent authority in full before implementing it, including the relevant manual revisions and an assessment showing the implementing rules are still met. The authority evaluates the description, may inspect, and then decides. Elsewhere the route is less codified but the logic is similar. You propose, they assess, you implement.

Anyone who tells you their data is accepted everywhere is describing a market that does not exist.

What a defensible record contains

Strip away the format questions and a compliance report has one job. It has to let a person who was not there reconstruct what was measured, when, by whom, with what, and against which criterion. Three properties carry that weight: traceable, repeatable, dated.

Repeatability is the property people underrate. A single number is an assertion. The same procedure, run again by someone else, producing the same result within a stated uncertainty, is evidence. That is why a documented and reproducible flight path matters more to an auditor than the resolution of the sensor. It is also why we keep the mission plan alongside the results for the systems we measure, including the PAPI , where the re-check after an adjustment has to reproduce the original geometry to mean anything.

Retention is the part to be careful about. Periods vary by state and by record type, and quoting the wrong one is a real risk. One verified example: in the United States, 14 CFR Part 139 requires a certificate holder to prepare and maintain a record of each inspection under the self-inspection rule for at least 12 consecutive calendar months. That figure belongs to that rule in that country. Do not carry it across a border. Your aerodrome manual and your national rules govern what you keep and for how long.

The aerodrome manual is where a method becomes yours

This is the step most operators skip.

A new measurement method does not become acceptable because a vendor demonstrates it. It becomes acceptable when it is written into the documents the authority already oversees. The aerodrome manual states how the aerodrome inspects its facilities. If your manual says a task is performed one way and your evidence was produced another way, the mismatch is a finding, regardless of how good the data is.

The safety management system carries the other half. Changing an inspection method is a change to how a safety-relevant task is performed, and management of change is a standing element of the SMS framework under ICAO Annex 19. The expected artefacts are ordinary: a description of the change, an assessment of what could go wrong, the mitigations, and evidence that the new arrangement performs as intended. That assessment is usually the strongest part of a proposal to an authority, because it is written in the language the authority already uses.

Together these are your compliance documentation . Not the report from any one survey, but the manual, the procedure, the change assessment, the training records and the retained data behind them.

How acceptance actually happens

In practice it looks like this, and the order matters.

1. Read what your own manual currently says about the task. That is the baseline you are changing.
2. Take the proposed method to your authority before the survey, as a described procedure with its assessment attached, not as a finished dataset.
3. Agree the format, the criteria applied, the retention and the signature chain in advance.
4. Revise the manual and the SMS procedure to match what was agreed.
5. Fly the survey, and produce the record the agreed procedure calls for.
6. Keep the raw data, not only the report, so a later compliance audit can reach behind the summary.

Steps 2 and 3 are the whole thing. Everything downstream is execution.

The failure mode

Here is how technically excellent work gets rejected.

An operator commissions a survey. The measurement is careful, the positioning is good, the report is detailed. It arrives at the authority as a surprise, in an unfamiliar format, produced by a method the aerodrome manual does not mention, against tolerances nobody agreed in advance. The inspector has no basis to accept it. Not because the numbers are wrong, but because there is no procedure the numbers demonstrate conformity with.

The data was never the problem. The agreement around the data was missing, and it cannot be added retroactively without redoing the work.

The inverse also holds, and it is worth saying plainly. Paperwork agreed in advance does not rescue a bad measurement. Both halves have to be there.

What we can and cannot say

We build our reports to be traceable, dated, repeatable and formatted for submission, and we hand over the underlying evidence rather than only the summary. Our own view of what a report has to contain is on the compliance page , and the standard side of the picture is in what ICAO Annex 14 requires of your PAPI .

What we will not tell you is that your authority accepts drone-derived data, or that any regulator has approved us. No compliance certification of that kind exists to point at, and the aerodrome certificate is yours, not ours. What we can do is give you a method described well enough to put in front of your authority, and a record that holds up when someone comes back to it two years later and asks how you knew.

Start that conversation with your authority before the survey. It is a short conversation early and an expensive one late.