A bright, young, instrument rated pilot recently asked me the following question about flying VFR-on-top. He states, "I need a bit of clarity on something which seems to generate different answers from person-to-person. Suppose I am going from Seattle to San Jose in VMC the entire way. I choose to file an IFR flight plan just to remain in radar contact. Since I am in VMC, I would like to go VFR-on-top direct SJC via my handheld GPS. Can I request this from ATC, and still remain on my IFR flight plan?"
VFR-on-top is an IFR operation. The only thing that's different is that you, the pilot, operate solely in VFR conditions at a VFR cruising altitude of your choice. You can change VFR altitudes anytime you desire (subject to any ATC restrictions, of course) as long as you notify ATC of that change. You're also responsible for meeting VFR visibility and cloud clearance requirements as well as seeing and avoiding other airplanes. Because you're operating in VFR conditions, the controller won't apply IFR separation standards between you and other IFR airplanes. He or she will, however, continue to provide traffic advisories and safety alerts, and apply merging target procedures to other aircraft operating VFR-on-top. Despite operating in VFR conditions, nothing else changes in regards to operating IFR. You're still required to follow all the other IFR rules and regulations.
What does this mean to you?
It means that you can't use a handheld GPS as your primary means of IFR navigation, even if you're operating VFR-on-top. There is no handheld GPS that's approved as the sole source for IFR navigation (handheld units don't have RAIM [Receiver Autonomous Integrity Monitoring] capability nor do they have antenna installations that guarantee high quality reception, among other things).
Since we're on the topic, here are a few other things to consider when operating VFR-on-top.
Use It as Often as You Like
I encourage you to use VFR-on-top operations. It doesn't make sense to stay in solid IFR conditions if you can climb above the cloud tops or descend below the cloud bases, especially if there is an icing potential. Yes, VFR-on-top operations can be conducted above, below or even in between cloud layers as long as you can remain the appropriate distance from clouds and maintain the required minimum VFR flight visibility.
Keep in mind that VFR-on-top operations are not approved at altitude below the MEA or MOCA or below the controller's MVA (Minimum Vectoring Altitude) or MIA (Minimum Instrument Altitude).
When You Need a Hard Altitude
What do you do when you see a solid mass of clouds ahead or you simply want to return to a hard IFR altitude? Just ask the controller for a hard IFR altitude. Pick up the mic and say something like, "Center, this is 2132 Bravo, request 5,000 feet (or any appropriate IFR altitude), over." ATC will usually give you that altitude immediately or, if there's a traffic conflict, you'll be instructed to remain VFR-on-top until you can be worked into the IFR traffic flow. Under no conditions should you fly into clouds when operating VFR-on-top. In other words, if ATC can't or doesn't give you a hard IFR altitude in time, then turn so as to avoid the clouds by the appropriate distance and notify ATC immediately. Also, plan your hard altitude request advance. In this instance, airplanes that are already receiving IFR separation get priority over airplanes that are VFR-on-top.
Cleared for the Approach
A while back I remember flying VFR-on-top with a student when he received this clearance that went something like this:
2132 Bravo, you're 10 miles west of HIGRO intersection, cleared for the ILS Runway 26 right approach to Ontario. Cross HIGRO in VFR conditions on top. Contact the tower at HIGRO, over.
I looked over at my student and asked, "Well Bob, what altitude can you go down to?"
He looked back and said something like, "Well, I?m not partial to any particular altitude. What do you recommend boss?"
That wasn't exactly the answer I was looking for. Granted, this clearance can be a little difficult to interpret, so here's what it means. From our present position, we are to maintain VFR conditions on top until reaching HIGRO. In other words, we can go up or down to any VFR altitude of our choice as long as it keeps us: 1,000 feet above the cloud tops (we were in Class E airspace), above the minimum altitude shown along the approach plate's feeder route to HIGRO and at the appropriate hemispherical VFR cruising altitude (unless we were at or below 3,000 feet of the surface where VFR hemispherical cruising altitudes no longer apply). Once we're at HIGRO we'd fly the approach just like any other IFR approach for which we've been cleared.
Therefore, we held our present VFR altitude (in VFR conditions) and, upon crossing HIGRO, we descended down to the altitude shown on the feeder route. Now we we're no longer required to maintain VFR conditions. We flew the approach past HIGRO in IFR conditions.
Sometimes ATC will provide a VFR-on-top altitude restriction. For instance, the controller may say:
2132 Bravo, you're 10 miles west of HIGRO intersection, cleared for the ILS Runway 26 right approach to Ontario. Cross HIGRO in VFR conditions on top at or above 5,500 feet. Contact the tower at HIGRO, over.
In this instance we can go down to whatever VFR altitude is appropriate as long as it's at or above 5,500 feet. Upon reaching HIGRO, we'd fly the approach just like any other IFR approach for which we've been cleared (that means we can go down to the lowest altitude shown on the chart's non-radar routes and fly solid IFR if necessary).
Selecting VFR-on-top in Your Flight Plan
It's also possible that you may desire to file an IFR flight plan and select a VFR-on-top cruising altitude before departure. If so, instead of listing an IFR altitude in the altitude box of your flight plan, put the letters OTP. In lieu of a hard IFR altitude, you should receive an IFR clearance that says something similar to this: climb to and maintain VFR conditions on top. If not on top by (fix) or (altitude) then maintain (altitude).
After departure, ATC will normally tell you to report reaching VFR conditions on top. Of course, it's always wise to know the height of the cloud tops before filing for VFR conditions on top.
So, take advantage of VFR-on-top whenever possible. I've used it a lot when delays were expected enroute or when IFR traffic kept me from getting a direct route. Remember, ATC doesn't have to provide IFR separation from airplanes operating VFR-on-top. Therefore, if ATC says that there is too much traffic to give me direct to a fix or intersection I ask if going direct is possible if I do it VFR-on-top. Often, this works quite well.
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