Trenčín Airport: PAPI Re-aimed and Re-checked After the Festivals

The airport and why the PAPI came out

Trenčín Airport sits in the Váh valley in western Slovakia, with a single runway, 04/22, and a PAPI at each end. Each PAPI is a row of four units on adjustable legs, set at four angles, so a pilot on the correct slope sees two red and two white.

In summer the airfield is a festival ground. Several events take over the site, and the PAPI units were taken down for the season and put back once the last one was over. A unit that is unbolted, moved and set up again has lost its aiming. Its legs are adjusted again, and its angle depends on how carefully that was done and on the ground it now stands on.

One of the reinstalled units on the day of the first check. The angle the approach sees is set by the four legs and the base under them.

The aerodrome wanted to know, before relying on the PAPI again, whether each unit showed the angle it was meant to. It asked TarmacView to measure both systems.

What the first check found

TarmacView flew both PAPIs on the evening of 11 September 2026. The drone, a DJI Matrice 4T with RTK positioning, climbed through a vertical profile in front of each wing bar after dark, several times per runway end, and the transition angle of every unit was computed from the frames where its light changed from red to white. Each unit’s position had been surveyed, so every angle is geometry measured from the approach, not an impression.

One wing bar of four units. On both runway ends, two of the four read outside tolerance.

The result was clear and repeatable across flights. On runway 04, two of the four units sat outside the tolerance of their setting angle. On runway 22, two more did, and the glide path the pilot sees was off with them. The report rated both PAPIs as restricted, with the approach path indication unreliable until the units were corrected. It named each unit, the direction of its error and its size, and recommended checking those units with a clinometer at the box. It went to the aerodrome on 14 September 2026.

Re-aiming and the re-check

With the units named, the aerodrome called in TechniServ, its lighting contractor. The crew did not have to re-aim all eight boxes and hope. It went to the four that were off, knowing which way each one needed to move.

TechniServ worked at the units during the day on 28 September 2026, and TarmacView came back the same day. Once the adjustment was done, the drone flew the same profiles as on the first visit, from dusk into full darkness, across four sessions and seventeen runs over the two runway ends.

The re-check after dark. The controller flies the planned profile in front of the wing bar while the runway and approach lights stay on.

Every one of the eight units came back within tolerance of its setting angle, on both runway ends. The glide path measured within tolerance on both, and the widths of the sectors below, on and above the slope were within tolerance too. The revalidation protocol, issued on 30 September 2026, carried no further recommendations on the angles.

Timeline

What the aerodrome has now

Two dated protocols that tell one story. The first shows which units the reinstallation left out of tolerance and by how much. The second shows the same units, measured the same way, back within it. Between them sits the contractor’s adjustment, so anyone opening the maintenance file later can see what was found, what was changed and what it measured afterwards. That is the kind of record the EU maintenance rule, ADR.OPS.C.015, asks for after corrective maintenance, and it is the form a flight inspection or an authority review can start from.

It also has a baseline. The next time the units come down for the summer, the re-check gives a measured state of every unit to compare the reinstallation with.

What we would do differently

Measure before the units come out. The aerodrome’s previous protocol had all eight units within tolerance, which points at the reinstallation as the cause. Without a measurement taken just before the festivals, that stays likely rather than proven. A short check before dismantling costs one evening and makes the after-check a direct comparison.

Have the contractor on site the first night. The first visit only measured, and the fix needed a second visit 17 days later. The angles are computed on a field laptop on site, so a technician standing at the wing bar could have re-aimed the named units that night and the drone could have flown the profile again before everyone went home. The trade-off is booking two crews for an evening when nobody yet knows whether anything is wrong.

Plan the check into the festival calendar. The reinstallation date is known months ahead. Booking the measurement for the first evening after it keeps the gap between putting the units back and knowing they are right as short as it can be.

Related

The steps this engagement followed are the ones on PAPI out of tolerance : confirm which unit is off, re-aim it, re-check it. The PAPI inspection service page sets out everything measured per unit. If the units come out because of works on the runway itself, the lighting checks after works cover the rest of the runway lighting too. For how a drone measurement and the flight inspection aircraft divide the work, see drone survey versus flight inspection .