Plane & Pilot
Tuesday, January 1, 2008

VMC Vs. VFR


What’s technically legal isn’t necessarily safe


vmc cs vfrIn basic flight training, student pilots memorize the cloud clearance and visibility criteria for operation under visual flight rules and instrument flight rules (VFR and IFR). Flight schools and instructors drill into students the cloud clearance and visibility requirements for VFR operations in various categories of airspace, all the while neglecting to mention that none of this has much to do with the ability to keep an airplane upright during periods of restricted visibility and/or lack of terrain definition." />

Perhaps the most significant difficulty in these situations is for the pilot to recognize that he or she is entering IMC, even though the visibility and ceilings meet the basic VFR requirements. Operating visually in PVFR conditions can rapidly result in a loss of control, unless the pilot quickly recognizes the deteriorating conditions and performs a 180-degree turn to exit those conditions, or successfully and quickly transitions to flight by instruments.

So, what can we do to better prepare ourselves for a possible foray into PVFR? The answers to this question are simple, but the actions implied by these answers are more difficult to accomplish than they may seem at first blush.

vmc vs vfr
When acquiring your preflight weather briefing, you should investigate weather patterns in areas you frequent (be more conservative in less-familiar destinations). Additionally, pay attention to the landscape and potential obstacles you could encounter on your next flight.
First, pilots should view visibility forecasts with a skeptical eye. I don’t mean to suggest that forecasts are always flawed. I’m thankful that I’m not a forecaster, since accurate forecasting, particularly over large parts of the country, is a daunting task. There’s no doubt in my mind that forecasters do the best they can, but the forecasts they generate are frequently in error. So, when acquiring your preflight weather briefing, dig a bit deeper than just the basics. Try to discover trends. Find out what direction the weather is moving, and look at observed weather conditions “upstream” from your route of flight. Consider whether the observed weather is better or worse than the previous forecast suggested it should be. Learn about the weather patterns in areas you frequent, and be more conservative in areas you’re unfamiliar with.

Next, look at charts of the area. Are there portions of your route that may offer poor visual references? Crossings of large lakes or the extensive prairie country in the Midwest in winter can create a PVFR scenario in low ceilings or restricted visibility.

Talk to the locals. I’ve found that most pilots are happy to provide visitors with advice on flying safely in their part of the country. Warren Thompson in Kotzebue was responsible for my introduction to PVFR in that part of the world. Thompson worked for many years at the Kotzebue Flight Service Station, and in his free time, he flew for an air-taxi operator. Thompson not only briefed the forecasts to pilots in the area, but also flew the weather himself. Unfortunately, the consolidation of Flight Service Stations has nearly eliminated this kind of local knowledge among FSS briefers.

Be conservative. This is easy to say while you’re at home, perusing the weather via the Internet or talking to a briefer. Spend three days camping in the rain at a small airport a few hundred miles from home and that conservatism gets harder to maintain.




0 Comments

Add Comment