Flying in Special VFR conditions can be a little dicey and may be a little pricey.
A Piper 28-160 departed the airport under special VFR conditions. The weather did not improve as he expected, so he began a turn back to the airport for landing. His right wing clipped a tree on a hill during the turn and he crash landed straight ahead in a field. The pilot was alone and received minor injuries.
A Cessna C-172 obtained a Special VFR clearance into a northern airport. The weather continued to deteriorate and the pilot was unable to locate the airport. He climbed above the fog and cloud and flew back in the direction he came from. He was able to become visual with ground again and located a highway to land on. He did not have enough fuel to continue to the nearest alternate airport some distance away.
Special VFR can be used to get into or out of (day time only) an airport when the weather at an airport is below VFR, but the weather is VFR or expected to be VFR outside the control zone. To get a Special VFR clearance the flight visibility must be greater than 1 mile for an airplane or greater than a half mile for a helicopter. The aircraft must be operated clear of cloud and with visual reference to the ground at all times.
The request for special VFR must be made through a control tower, an FSS or a CARS who coordinate with ATC to ensure that there is no expected IFR traffic inbound to the airport or outbound from the airport during the time the Special VFR aircraft is expected to operate within the control zone.
The aircraft must be radio equipped. The pilot must request the Special VFR clearance, it cannot be offered to us. At night, Special VFR can only be approved for arrival at an airport.
For departure, problems arise as we assume that the weather will improve shortly after take-off either because it looked better when we drove in to the airport, we have anecdotal evidence that it is or was better a ways out, or the weather is better at the destination so we feel it has to improve.
The weather condition that has lowered the visibility below VFR is usually mist or fog. Mist or fog is seldom consistent for any distance. It may actually be worse 2 or 3 miles away from the airport. It may get worse before it gets better. Mist or fog can thicken as well lighten up over time.
The longer it has been since we received the report that the weather was better outside the control zone, the less we should be sure it still is. Fog also has a tendency to move and it may move in the direction we wish to go.
Many airports have their own little micro climates and may fog in while we are enroute and Special VFR may be necessary to enter the control zone and land. The airport weather report we get will be from a certified weather observer or an AWOS. The weather observer may be able to give some supporting observations such as “the visibility is better to the east” which may help. In either case the weather observer or the AWOS cannot see 3 miles. And weather that is between what they see and where we are may be significantly worse.
Special VFR is only given to one aircraft at a time to avoid mid-air collisions, which is why is cannot be approved when there is an inbound or outbound IFR aircraft.
There are other hazards with flying around in visibilities of little better than one mile. One of these is obstacles. Towers, wires and gently rising terrain are difficult to spot in poor visibility.
Another is white out. Many aircraft have flow into the ground because the pilots could not judge their height above the ground. Yet another is rain illusion. Due to the refraction of light through a wet windscreen, we appear to be higher than what we are.
We tend to judge level attitude with our peripheral vision, so when we are flying close to terrain without any other reference, we tend to roll in the direction of down sloping terrain. This tendency could get us lost or confused or it could cause us to fly into something.
Under IFR conditions we would concentrate on our instruments; not a good idea VFR low level. When we realize that we are turning when we don’t want to be, we tend to jerk the controls to regain a level attitude. This could upset our inner ear fluid balance and give us the illusion that we are now flying with a wing down in the opposite direction.
If we rolled into a banked attitude at a roll rate of less than 3 degrees per second the banked attitude may give us the illusion that we are in a level attitude. Even a gentle roll back to a real level attitude may leave us feeling that we are in a banked attitude in the other direction. This is called ‘the leans’. IFR pilots fight this by concentrating on their instruments; not a luxury we can afford.
A prolonged gentle turn in one direction may also leave us feeling that we are again in wings level flight attitude. We may then feel the need to increase our bank angle to turn. This could end in a spiral dive.
Without a horizon, any tendency to rapidly increase the power may give us the illusion that the aircraft is pitching up. A correction could put us into the trees or ground. A rapid decrease in thrust might give the illusion of pitching down. A correction may put us in IFR conditions.
A rapid head movement, particularly a movement against the direction of turn can move the fluid in the inner ear producing a severe sensation of rolling or pitching up or down (another type of Coriolis Effect). A quick glance at a map or reaching for something that has fallen on the floor can result in this effect.
Fatigue can increase the possibility of any of these illusions occurring. Hunger increases fatigue. Fuel yourself and get adequate rest before flying in such conditions. Be wary of the possibilities before requesting Special VFR and be spring loaded to the ‘turn around’ position so that a decision is made quickly if you don’t like what you see. We all tend to push the weather a little with occasional catastrophic results. It is always to better to arrive late in this world than early into the next.
Dale Nielsen is an ex-Armed Forces pilot and aerial photography pilot. He lives in Abbotsford, B.C., and currently flies medevacs from Victoria in a Lear 25. Nielsen is also the author of seven flight training manuals published by Canuck West Holdings.
Got an aviation safety story to tell? Dale Nielsen would like to hear from pilots who have educational aviation experiences to relate. Excerpts from these stories will be used in upcoming safety articles. Dale can be contacted via e-mail: firstname.lastname@example.org