What is the purpose of VFR-on-top?

Question

VFR-on-top is an IFR clearance in the US that a pilot can request to allow an IFR flight to use VFR altitudes provided that it can remain in VMC. Requesting and receiving a VFR-on-top clearance doesn't cancel the IFR flight plan.

When is this clearance useful? It allows the pilot a greater choice of cruising altitudes, but why would a pilot prefer to use VFR-on-top rather than request a different IFR altitude? VFR-on-top adds at least one task to the pilot's workload - maintaining VFR cloud clearance - without reducing the IFR workload.

Answer 1

The VFR on top clearance is often given with a block of altitudes. Such as this from the reference document "Maintain VFR-on-top at or between six thousand and one zero thousand.” With this clearance the pilot can fly any altitude they want within this block of altitudes without having to contact ATC for further clearance. This flexibility can be useful with the conditions are such that the clouds come and go as you fly along. So if you are cruising along at 6500 and encounter a cloud and need to climb to 8500 to maintain clearance you just do it. No need to contact ATC and wait for them to ensure they can clear you higher while the clouds keeps getting bigger and bigger in the windshield.

Even if there are not cloud issues, the ability to change altitudes may be useful in seeking an altitude with more favorable winds.

Answer 2

Being in VMC has several benefits over hard IMC, especially if you don't have an autopilot, so being on top has advantages. :

• Manual flying with visual reference to the horizon is much easier and less strain than manually flying using instruments for attitude control
• Being out of cloud enables a pilot to see and avoid traffic
• Flying in cloud can be bumpy, VFR on top is often much smoother
• Icing is a hazard when flying in cloud, being on top of them means you won't ice up

VFR on top works well when you have a stratus layer that has an even top, not so well when you have clouds at differing levels, so it's not always a viable option.

Answer 3

In a training environment, VFR-on-top is fantastic. You can use your IFR clearance to punch through a cloud layer to clear skies on top, practice maneuvers (or what have you), and then shoot an approach back down. VFR-on-top can turn a bad weather day into a training day, and anytime you can do that (and get real-world actual instrument experience on top of it) is a good day.

Answer 4

An unaddressed benefit of going VFR-on-top is the ability to file a flight plan beyond navaid limitations. ATC can issue the clearance, and not worry about distance criteria.

An example would be a flight requesting KBFF..KFSD at FL090. Before GNSS and ADSB, I'd give you three choices for such a route:

1. KBFF.V169.RAP.V26.PIR..FSD..KFSD. (Adds 75 miles to the flight)
2. A climb to FL130 for radar coverage. (Aircraft may not be capable, long term)
3. An explanation that you could go direct if you requested VFR-on-top.

Without explaining ALL of the options, I would not say anything about VFR-on-top, because I cannot solicit it. If the options are explained, it is not considered solicitation.

Also, some issues in the above answers need to be addressed.

"The VFR on top clearance is often given with a block of altitudes. Such as this from the reference document "Maintain VFR-on-top at or between six thousand and one zero thousand.” With this clearance the pilot can fly any altitude they want within this block of altitudes without having to contact ATC for further clearance."

This excerpt is from the instructions for holding separation, and should not be used in a clearance with enroute flight. That's because the pilot is responsible for separation from other aircraft. The ability to climb/descend to any appropriate VFR cruising altitude is inherent in the VFR-on-top clearance.

Lastly, as fjch1997 pointed out, being cleared VFR on top doesn't automatically allow you to deviate from your route.

"When an aircraft has been cleared to maintain “VFR‐on‐top,” the pilot is responsible to fly at an appropriate VFR altitude, comply with VFR visibility and distance from cloud criteria, and to be vigilant so as to see and avoid other aircraft. The pilot is also responsible to comply with instrument flight rules applicable to the flight (e.g., adherence to ATC clearances)."

Answer 5

A couple of other benefits of VFR-ON-TOP are:

1. In coastal areas (e.g., busy west/east coastal airports) it is common during certain times of the year for a low overcast or fog to exist with tops only 1000 to 3000 feet. If you need to get out of the area you will often need to get line with 15 other IFR departures in front of you. If you request a VFR-ON-TOP clearance and advise ATC it's your intention to cancel IFR once you are on top you can often get a clearance far more quickly. (Just make certain you keep your word and cancel IFR when reaching VFR). This is especially useful for small cargo operators that operate daily on a schedule out of the same airport .

2. Some air carrier commuter type operators fly to/from smaller airports to busy major terminals and (if authorized to operate VFR-ON-TOP) can often fly direct routes since (while VFR-ON-TOP) ATC does not have to provide standard IFR separation.