There's a big difference between being assigned "fly runway heading" and flying a runway track, or the extended runway centerline, on departure.

How would you handle the following scenario? We asked ATC what they wanted pilots to do. Here's what they said...

Two Pilots Take Off From Parallel Runways On A Strong Crosswind Day...

Two VFR aircraft are cleared for takeoff from the Grand Forks Airport (KGFK) on parallel Runways 35L and 35R. Both are assigned "fly runway heading" by the control tower. The aircraft departing 35L maintains the runway heading on departure of 356 degrees. The aircraft departing runway 35R maintains the runway track, or runway centerline throughout their climb. There's a strong crosswind from the West at 35 knots. Do you see a problem?

With a strong westerly crosswind, the aircraft departing Runway 35L maintaining "runway heading" is pushed by the crosswind, drifting closer and closer to the parallel departure from 35R. The aircraft departing Runway 35R is crabbed significantly into the wind to maintain runway track (centerline). The Air Traffic Control Tower notices the problem and issues a breakout instruction to the aircraft departing runway 35R as both planes drift close to each other.

While this scenario is simply an example, events like this happen frequently. It's an easy mistake to make, so we'll clarify what you need to know.

A Controller Instructs You To "Fly Runway Heading"

FAA JO Order 7110.65W, the ATC Procedures and Phraseology "Rule Book," defines what it means to "fly runway heading"...

This is the verbatim definition for all aircraft, IFR or VFR, being issued a "fly/maintain runway heading" clearance on departure.

But in reality, the intentions of controllers issuing this instruction for VFR aircraft may differ, which we'll get into below...

Does Anything Change Under IFR?

Simply put, no. According to the FAA's Instrument Procedures Handbook (1-42), "runway heading is the magnetic direction that corresponds with the runway centerline extended (charted on the airport diagram), not the numbers painted on the runway. Pilots cleared to 'fly or maintain runway heading' are expected to fly or maintain the published heading that corresponds with the extended centerline of the departure runway (until otherwise instructed by ATC), and are not to apply drift correction [for wind]."

Why? In the event of parallel departures, this prevents a loss of separation caused by only one aircraft applying a wind drift, as in the example above. If each aircraft flies a heading instead of a track, it eliminates the separation issues caused by strong winds. Also, if you're in IMC, there's no way to visually verify that you're flying runway centerline.

Have You Ever Heard "Say Winds Aloft?"

This is one reason why ATC occasionally asks pilots for information about wind speed and direction. It helps them plan out wind drift and properly assign vectors based on anticipated ground tracks.

On an ATC radar scope, especially one without many traffic targets, it can be hard for controllers to predict how wind will affect your track. That's another reason why you might get vector adjustments from ATC on departure or arrival.

VFR Departures From NON-TOWERED Airports

Here's where things start to get confusing. If you're departing from a non-towered airport, you're expected to track the runway centerline under VFR. In fact, one of the "common errors" that the FAA lists for VFR departures is "inadequate drift correction after lift-off." Here's what the FAA's Airplane Flying Handbook (5-6) says...

This is where the confusion stems from. In the Airplane Flying Handbook, the FAA is likely referencing non-towered VFR traffic patterns, where it's important to fly runway centerline in order to maintain your own separation from downwind/upwind traffic.

VFR Departures From TOWERED Airports

You now know the definition of "fly runway heading." According to the ATC Procedures and Phraseology book, you should fly the heading and NOT crab for wind drift when assigned this clearance. But in reality, a controller may expect you to maintain runway centerline even when issuing this instruction. Just like pilots, controllers aren't perfect and this phraseology creates just as much confusion for them as it does for us. This was evident through conversations we had with control towers across the country, where we heard different opinions from various tower controllers.

This is most evident at airports like Grand Forks (KGFK), Denver Centennial (KAPA), and Rocky Mountain Metro (KBJC), all airports with close parallel runways and hundreds of daily VFR traffic pattern operations.

Some controllers expressed it's their primary objective to have all VFR departures maintain runway centerline to reduce the risk of traffic conflicts from parallel runways, upwind, or downwind VFR traffic.

According to the definition of "runway heading" from FAA JO Order 7110.65W, it's incorrect phraseology to instruct "fly runway heading" and expect and aircraft to maintain centerline by accounting for wind drift.

To eliminate confusion, you may hear any of the following (non-standard) phrases from ATC:

• "Maintain runway centerline."
• "Fly straight out."
• "Track runway heading."

How Should You Fly Your Departure?

Under IFR, always fly the heading assigned by ATC or on a departure procedure. When departing VFR at a non-towered airport, you should always track runway centerline to avoid conflicting with other VFR traffic in the pattern.

And at towered airports under VFR, you should clarify the instructions issued by the tower if you're confused about their expectations. This is especially important if you're departing from an airport with close parallel runways on windy days. Controllers would rather you take a second to clarify confusion, rather than making an assumption and creating a traffic conflict.

What's your opinion? Have you ever run into similar confusion? Tell us in the comments below.