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Look Out Below!

When VFR aircraft share airspace with IFR aircraft, the pilots must have three miles visibility so they might avoid mid-air collisions -- but can both IFR and VFR pilots legally occupy the same airspace with less than three miles visibility?When VFR aircraft share airspace with IFR aircraft, the pilots must have three miles visibility so they might avoid mid-air collisions -- but can both IFR and VFR pilots legally occupy the same airspace with less than three miles visibility? Yes... and it's more common than you think!

DISPELLING THE MYTHS
I flew IFR for many years thinking that if I was cleared for an instrument approach, that I was also guaranteed clearance from other aircraft. I also thought that the airspace rules would protect me. After all, if I were flying IFR in the clouds I was doing so in an airspace area that would keep VFR pilots out of the way, right? Right... most of the time. When I am flying IFR in the clouds, the controllers are providing my separation, and VFR pilots should not be in that same airspace. But there is a hole in this coverage. The problem exists at the bottom of almost every non-precision approach.

Figure 1
Look at Figure 1. Yazoo County is an uncontrolled airport with a Magenta Shaded ring around it. This means that Class G airspace is present at the Yazoo airport and that Glass G extends from the surface to 700 feet above the surface. In this case 700 AGL is equal to 804 feet MSL (104 foot airport elevation + 700 feet above ground = 804 MSL). This means that, during daytime hours, a VFR pilot can fly around in the vicinity of the Yazoo airport with only 1-mile visibility so long as he remains clear of the clouds -- at any distance -- as long as the altimeter never reads above 804.

Figure 2
WHERE IFR AND VFR MEET
Now look at Figure 2. This is the Profile View and Landing Minimums section of the VOR/DME Runway 17 instrument approach into Yazoo County airport. To fly this approach, an IFR pilot would cross the CLOWR intersection at 1,800 feet and start a descent down to 1,100 feet MSL. When the pilot passes the 30 DME fix, the descent can continue down to 700 feet MSL which is this approach's Minimum Descent Altitude (MDA).

Problem: What if the cloud bases on this approach were 750 feet MSL? There is a real and present danger of mid-air a collision between IFR and VFR aircraft -- both of which are flying legally. If the IFR pilot descends to 700 MSL while on the approach, they will be descending into Class G airspace, which begins at 804 MSL. The IFR pilot will be leaving the security and safety of controlled Class E airspace behind. Meanwhile, a VFR pilot flying below 804 can legally fly with only one-mile visibility just under the clouds -- as long as they are 'clear of clouds.'

Figure 3
Figure 3 combines the features of both the VFR and the IFR charts to illustrate what is really happening. Note: Yazoo County airport is not a special case...

The MDA for most non-precision instrument approaches is in Class G airspace, so look out below.

BOTTOM LINE, IFR Pilots: When you begin your final descent to MDA and into Class G airspace, switch away from Air Traffic Control and over to the airport's advisory frequency as soon as possible. This will give you the best chance of hearing VFR pilots who might be below the clouds and in the traffic pattern. You should always know the MSL altitude when you pass the boundary between Class E and G airspace. If you pass through that boundary while still in the clouds -- watch out when you break out.

BOTTOM LINE, VFR Pilots: Even though you are not flying IFR (yet) you should know where the instrument arrivals to your airport come from. Make every effort to avoid the instrument approach path -- regardless of weather conditions. Of course, you cannot avoid the entire approach path because it goes to the same runway you are going to, but before you turn on your final approach to land, you should look to the left, to the right, and up.

Play nice. We're all in this game together.

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About This Author:
Paul A. Craig is a Gold Seal Multiengine and Instrument Flight Instructor. He currently holds a total of 11 Flight Certificates including his ATP. Craig is a previous winner of the North Carolina and Tennessee Flight Instructor of the Year award, the NCVT Outstanding Teacher award and has served as the regional representative of the National Air and Space Museum. Craig is an FAA Aviation Safety Counselor and the author of eight books, including Pilot In Command, The Killing Zone: How and Why Pilots Die, and Controlling Pilot Error: Situational Awareness (all from McGraw Hill).
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