Curv Aero FAA Notice of Presumed Hazard: What It Means and What to Do Next
You filed a 7460-1 and, instead of a Determination of No Hazard, the FAA sent a letter saying your structure is presumed to be a hazard. It's not the end of the project. It's the FAA's opening position, and most sponsors resolve it. This guide explains what the notice means, why the FAA renamed it, and the realistic paths from here.
Updated November 7, 2026 · Based on 14 CFR Part 77 and FAA Order JO 7400.2
Notice of Presumed Hazard vs. Notice of Preliminary Findings
For years the FAA's letter was called a Notice of Presumed Hazard (NPH). In a 2020 change to its airspace procedures order, JO 7400.2, the FAA renamed it a Notice of Preliminary Findings (NPF), explicitly to reduce the alarm the old name caused. The FAA noted that the letter itself didn't change: it still reports the findings and says that, without a change, the structure is presumed to be a hazard.
Many people, consultants and local officials still say "NPH," so you'll see both terms. They mean the same stage of the process.
Why the FAA issues one
The FAA issues the notice when its study finds that the structure exceeds the Part 77 obstruction standards and/or would have an adverse effect on navigable airspace, air navigation, or radar and surveillance facilities, and that resolution or further study is needed. Common triggers:
- Instrument procedures: the structure would raise an approach's minimums, affect a missed approach, a departure's climb gradient, or a circling area.
- Minimum altitudes: it would raise a minimum vectoring altitude, minimum en route altitude or other published altitude.
- Imaginary surfaces near the runway: a building or crane in the approach or transitional surface. See Part 77 imaginary surfaces.
- VFR operations: it would sit in a traffic pattern or a heavily used VFR route.
- Radar and navaids: physical or electromagnetic interference, common with wind turbines and large metal buildings.
Note what's not on that list: simply penetrating an imaginary surface. Under §77.15(b), any obstruction is presumed a hazard until study concludes otherwise, but the FAA can and often does issue a no-hazard determination for structures that exceed obstruction standards without a substantial adverse effect, sometimes informally called "exceeds but okay."
Read the letter for three things
- 01
The specific effect: which procedure, altitude, surface or facility is affected, and by how much.
- 02
The no-effect height: many letters state the height at which the structure would not have the adverse effect. That number frames every option below.
- 03
Your response window: the time the letter gives you to respond before the case lapses. Put it on the calendar immediately.
Your options
Lower the structure
The fastest path. If the letter gives a no-effect height and your project can live with it, amend the height through OE/AAA. The FAA can then issue a Determination of No Hazard. For towers and turbines, even 10–20 ft can be the difference.
Move it
Shifting a few hundred feet, out of an approach surface, away from a final approach course, or behind terrain, can remove the effect. Coordinates or height changes after the study has begun generally mean a new case, so screen alternatives carefully before refiling.
Provide information or negotiate
If you think the analysis rests on wrong data (an incorrect site elevation, a misplotted coordinate, a procedure that has changed), contact the FAA specialist named in the letter with documentation, such as a certified survey. Sometimes the effect can be resolved without changing the structure, for example if an affected procedure can be adjusted with no operational penalty. The FAA decides that, not the sponsor.
Request further study
The FAA normally won't start further study unless the sponsor asks. Further study can include circularization: the FAA sends the proposal to airports, aviation users and other interested parties for public comment, then weighs their responses. It adds months, and the comments can cut either way. It makes sense when the effect is real but you believe it's operationally minor, and you can't change height or location.
Withdraw
If none of the above works, withdraw or let the case terminate rather than collect a formal Determination of Hazard, which does not expire and can follow the site.
If you get a Determination of Hazard
- A Determination of Hazard is issued when the study concludes the structure would exceed an obstruction standard and have a substantial aeronautical impact.
- Unlike a no-hazard determination, it does not expire.
- Determinations subject to discretionary review take effect 40 days after issuance. A petition for discretionary review must be filed in writing and received within 30 days of issuance; if the last day falls on a weekend or closure, it moves to the next business day.
- Other parties can also petition against a no-hazard determination within the same window, which is one reason to keep an eye on your case after issuance.
An FAA determination is about air navigation. Some local jurisdictions treat a hazard finding as grounds to deny a permit; an FAA determination doesn't itself prohibit construction, but building against one carries serious practical and legal risk.
- Petition for discretionary review
- 30 days
- Determination takes effect
- 40 days
- Determination of Hazard
- Does not expire
How to avoid the letter in the first place
- 01
Screen before you fix the site. Check notice criteria, imaginary surfaces and nearby instrument procedures while the location is still flexible.
- 02
Use accurate data. Surveyed coordinates and elevations avoid findings based on an error.
- 03
Know the controlling surface and its margin, so you can design to it rather than discover it.
- 04
File early. An NPF late in the schedule is the expensive kind.
Find the controlling surface before the FAA does
The CurvAero Part 77 Report shows the controlling airport, surface and margin at your coordinate, so you can test alternative heights and locations before filing. If you already have an NPF, we can help you work out the height or position that clears it and amend or refile the case.
Frequently asked questions
Is a Notice of Presumed Hazard a denial?
No. It's a preliminary finding meant to start a conversation. The final decision comes later as a determination.
How long do I have to respond?
The letter states the response period. If you don't contact the FAA, the case is terminated.
Will lowering the height always solve it?
Usually, when the issue is physical obstruction of a procedure or surface. Radar and electromagnetic effects may need other solutions.
Can I build while the case is open?
Building before a determination is risky: local permits often depend on it, and a hazard finding afterward can force changes.