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IFR Aircraft Loses Separation With 1,500 Foot Tall Antenna

When you're on an IFR flight plan, it's a natural assumption that ATC is a big part of the safety of your flight. Controllers make mistakes too, and this flight is an example of a situation where a simple misunderstanding lead to a separation issue.

Corey Komarec

Report: IFR Aircraft Given A VFR Clearance Near 1,500 Foot Tall Antenna

We all know there are terrain, obstacle, and traffic clearance requirements for aircraft flying under IFR. Things like restricted areas, obstacle protection, and airspace entry requirements are a lot more simple under IFR for pilots, because in most cases, ATC will ensure that you're clear of terrain and obstacles for your filed flight plan. That said, controllers make mistakes too. Here's why it's important to be aware of your surroundings when flying under IFR.

We found the following NASA ASRS report published from January 2020. Many of the reports we've published in the past were written by flight crew members. In this case, the report comes directly from an ATC TRACON controller...

Aircraft X departed PHL on an IFR flight plan for a nearby satellite airport. The aircraft was given runway heading and 3,000 feet by the Tower. When the pilot checked in, he asked to maintain VFR on course. At that point, I falsely assumed the aircraft was a VFR departure and began handling him as such. I cleared the aircraft out of the Bravo "at or below 2,500 feet," and verified they were familiar with an antenna north of the airport.

The pilot leveled at 2,000 feet and flew through the 2,500 feet MVA associated with the antenna [which reaches 1,547' MSL]. When the aircraft got close to the destination airport, they asked to cancel IFR. The issue didn't even immediately register until I heard it later on the playback.

I should check every departure strip more closely. The aircraft's data tag was properly displaying as IFR - I believe that seeing the weight category displayed, and not looking at it closely, made me assume the aircraft was VFR (just because there was some character in the lower right of the tag).


Minimum Vectoring Altitude (MVA)

An MVA is the lowest altitude that ATC can vector you around a particular section of airspace. Approach and Center controllers can divide their scopes into small sections of airspace, separating obstacles and terrain from areas with lower vectoring altitudes. When radar coverage is available from an approach or center facility, MVAs are a great way to get as low as possible if you're flying into a VFR-only airport. But unfortunately, MVAs aren't published on your IFR charts.


Cross-Check Your VFR Sectional

In this case, there's no real way the pilot could've known that they were flying 500' below the MVA for that area. If the pilot was flying with an enroute IFR chart and not on a published airway, the only indication for the minimum off-route obstruction clearance altitude (OROCA) was 4,700 feet for that huge quadrant of the IFR chart.

Realistically, being cleared enroute at 2,000 feet MSL in an urban area should've triggered this pilot's thought process. If you're flying IFR this low to the ground, even while under the control of ATC, it's not a bad idea to occasionally cross-check your VFR sectional for terrain and obstructions around you.

Have you ever caught a clearance mistake under IFR? Tell us about your experiences in the comments below.

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