Learn why simulator ATC gives unsafe ILS descent clearances, how to check the chart, intercept from below and decide when to ignore ATC.
Simulator ATC gives unsafe ILS descent clearances because its controller often uses simplified descent logic, incomplete terrain constraints, or navigation data that does not match the aircraft’s approach. Do not dive to obey it: remain within the published approach profile, intercept the glideslope from below, and go around if the approach becomes unstable.
Why does built-in ATC get ILS descent profiles wrong?
Built-in ATC gets ILS profiles wrong when its descent model is less detailed or uses different data from the approach loaded in the aircraft. Across general flight simulators, the controller may be managing traffic and runway flow without fully understanding every altitude restriction on the selected procedure.
- Simplified descent calculations: ATC may calculate altitude from distance to the runway rather than the arrival, intermediate segment and glideslope-intercept restrictions.
- Mismatched navigation data: The simulator, aircraft FMS and chart may use different procedure revisions. Runway renumbering, amended fixes or a changed intercept altitude can then produce contradictory instructions.
- Incorrect approach transition: ATC may vector towards the final approach course while the FMS still contains a different transition or an arrival constraint that no longer applies.
- Weak terrain awareness: Some simulated controllers approximate vectoring altitudes and do not reproduce the real controller’s minimum vectoring altitude system accurately.
- Poor energy management: ATC may issue a clearance that is technically reachable only with excessive speedbrake, a steep descent or an unstable intercept.
If the questionable clearance arrives well before the approach rather than during ILS interception, our explanation of why simulated ATC starts descents too early covers that separate top-of-descent problem.
Should I obey an unsafe ATC descent clearance?
Do not follow an offline simulator ATC clearance that would breach an applicable charted minimum, compromise terrain clearance or force an unstable ILS intercept. An ATC acknowledgement penalty is less important than preserving a safe approach profile.
| Situation | Best response |
|---|---|
| The clearance remains above all applicable minimums and permits capture from below | Descend at a normal rate and level at the cleared altitude. |
| ATC assigns an altitude below a published segment minimum before the relevant fix | Level at the safe altitude, check the procedure and ignore or query the instruction. |
| You are already above the glideslope while inbound | Do not chase it with a steep descent. Request another vector or go around and reposition. |
| The aircraft is fast, high or not configured near the stabilisation gate | Go around rather than trying to salvage the approach. |
With human online ATC, read back the conflict and say that you are unable to comply instead of silently deviating. For other controller errors, use the same priorities described in our guidance on handling unsafe simulator instructions.
How do I recover from a bad ILS descent clearance?
Recover by stopping the descent, rebuilding a valid intercept and going around if there is insufficient distance to stabilise the aircraft.
- Confirm the selected approach. Check the runway, ILS frequency, inbound course, navigation source and approach transition. Identify the aircraft’s position rather than assuming ATC has placed it correctly.
- Check the applicable minimum altitude. Use the altitude for the segment you are actually flying, including step-down fixes and the published glideslope-intercept point. Our guide to choosing the correct ILS intercept altitude explains which chart figure matters.
- Level off instead of diving. A descent clearance gives an altitude to maintain; it does not demand an excessive rate. If a normal descent cannot achieve it safely, accept that the intercept must be abandoned.
- Rebuild the intercept from below. Establish a modest localiser intercept angle and level at an altitude where the glideslope will descend towards the aircraft. Do not use vertical speed mode to chase a glideslope that has already passed below you; the glideslope capture explanation covers why interception from above is unreliable.
- Arm approach mode only after verifying the indications. Confirm that the localiser and glideslope belong to the intended runway and that the aircraft-specific autopilot is in the correct navigation mode.
- Apply a stabilisation limit. Use the aircraft or operator’s published criteria. A common conservative benchmark is to be on path, correctly configured, at a controlled speed and sink rate by 1,000 feet above the runway in instrument conditions; otherwise, go around.
Can a lower-than-published intercept altitude be legitimate?
A lower-than-expected vectoring altitude can be legitimate when terrain is protected, local procedures allow it and the aircraft can still intercept the localiser and glideslope from below. That does not make every lower altitude generated by built-in ATC trustworthy.
The charted glideslope-intercept altitude is not the same as minimum sector altitude, and neither should be applied outside its intended purpose. Published segment minimums depend on position and fixes, while real controllers may use minimum vectoring altitudes that are not printed on the approach chart. When offline ATC conflicts with the known procedure and cannot explain its vector, the published profile is the safer reference.
Does “cleared ILS approach” mean descend and land?
No. An approach clearance authorises the instrument approach, while landing clearance is separate.
A clearance such as descend and maintain 3,000 until established, cleared ILS runway 27 approach means maintain the assigned restriction until established, then follow the published procedure as applicable. It does not authorise an immediate dive towards the glideslope, and it does not remove intermediate altitude restrictions before their associated fixes.