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Scud Running - Risk or Reward

©Ed Wischmeyer
Originally published in Inflight USA
Reprinted by the FAA

In the last two months, we’ve lost two planeloads of friends and neighbors to scud running. Two too many. Two planes with experienced, responsible pilots… we thought. What are the risks and rewards of scud running?

“Scud running” means deliberate flight under low clouds (“scud”), attempting to maintain visual meteorological conditions. There are risks: flight into unseen obstructions; loss of aircraft control in visual conditions; deliberate forced landings in unacceptable terrain; getting lost; inadvertent flight into instrument meteorological conditions, leading to either a loss of control accident or controlled IFR flight into terrain; fewer options in case of emergency. Are the risks worth it?

I think back to a flight I made as a student pilot from Boston to New Jersey through the New York TCA, with my instructor’s knowledge and blessing. The whole east coast was reporting 2000 feet overcast and ten miles visibility. Ten miles visibility in those parts was pretty normal, nothing to get excited about, sort of like twenty miles visibility here, and 2000 feet was within the acceptable range. The clouds were stable, the winds benign, there was no forecast of changing conditions, and I had successfully flown an ILS to minimums before solo, indicating an ability to handle some weather situations.

Contrast that to the two tragic accidents around here. Strong winds, winter storms, and terrain to excite atmospheric instability. What separates a safe student pilot flight from two tragedies that took experienced pilots? The altitude you fly at? the terrain you fly over? the weather you fly through? Let’s look at the risks.

The first risk is flying into unseen obstructions, such as towers or power lines. The way you minimize this risk is by having altitude above obstructions, and that precludes flight below hilltop level because hills and canyons are always infested with powerlines. Around the bay area, when the weather lowers, the passes seem to stay open longest, but… are you really familiar with what the Sunol pass looks like at 500 feet AGL? Is that really an option? As an exercise, go flying with a buddy on an IFR practice flight, and find out how hard it is to determine your position based on patches of ground through the clouds, even over “familiar” terrain. Do you know, really know, the terrain where you might go scud running? Do you know every hill, tower, and power line? I don’t. Would you fly as low in good weather as you would scud running?

Point two has to do with loss of aircraft control in visual conditions. How can this be? Turbulence, updrafts, and downdrafts. Sure, those of us who learned to fly east of California laugh at the relatively benign weather and lack of thunderstorms, but the winter storms here, coupled with orographic (terrain) effects can lead to a wild ride. If you are flying low over a hill or through a pass, you can get the tar beat out of you in turbulence, not be high enough to see an escape route, if there is one, or you could get caught in a downdraft beyond the performance capabilities of your aircraft. Some years ago, the story goes, a plane was suspected of crashing in the Altamont. Unable to locate that plane, one searcher decided to show his team where another plane had crashed previously. On the way to that first crash, they found the second crash. Does this indicate that local conditions were, repeatedly, beyond the capabilities of
general aviation aircraft and pilots?

In making your go/no go decision, consider the effects of stress on your decision making skills and on your flying skills. An attitude of “dying to get home” could lead to just that. Moreover, if you do get in a tight spot, chances are that your flying skills will be lessened because you will be spending at least some brain cycles fighting stress and fear. Add in turbulence and poor visibility and your stress level will climb into the flight levels. Lastly, most maneuvers, such as slow flight and steep turns, are taught and practiced in smooth air. Next time you are in moderate turbulence at a safe altitude with no passengers, try some slow flight and precision maneuvers. Now imagine doing that in turbulence at low altitude when you are stressed.

How do you minimize these risks? Don’t scud run through a pass. Don’t scud run over hilly or mountainous terrain. Don’t scud run if you aren’t skilled enough and rested enough to get absolutely all of the performance out of your airplane. Don’t scud run in wind or storm, or conditions of unstable air. Unstable air, as a quick refresher, is air that if lifted from its present altitude will continue to rise. Conversely, if that air is lowered in altitude, it will sink. Updrafts leading to cumulus clouds are an example of unstable air. The thunderstorms that always form southeast of Reid Hillview airport are an example of unstable air, and they always form in that one spot because the hills provide the initial lifting to start the vertical motion of unstable air.

Another risk of scud running is getting lost. Getting lost can lead to an unplanned landing due to fuel exhaustion, and the increased stress of flying around lost at low altitude in bad weather can decrease your ability to handle any other situations that might occur, such as carburetor icing, a mechanical malfunction, or any situation that requires above average skill or coordination. You avoid the risk of getting lost by flying in weather conditions that permit higher altitudes or by flying in areas that you know extremely well.

Whenever you fly, you should always have options in your back pocket to handle unforeseen circumstances. If you are scud running, and the weather closes in, you may not be able to maintain visual meteorological conditions. In other words, you may end up in the clouds. We all know that flying in clouds when you can’t handle it can lead to loss of control of the aircraft, with the aircraft emerging from the bottom of the cloud at high speed in one or more pieces. Even if you can handle IFR flight, if you are scud running in the mountains, you could fly the plane into a mountain under complete control, as may have happened to at least one of those two planes. Always leave yourself at least one out.

If you do contemplate scud running, for whatever reason, don’t scud run in deteriorating or unstable weather. For example, scud running as temperatures drop and water vapor condenses into ridge obscuration or fog could be terminal. Be aware of solar heating, and the effects of sunset and high clouds on solar radiation received at low altitudes. On one glider flight, I watched as high clouds cut off sunlight, clearing the way for a quick appearance of lower level clouds and snow.

You minimize the risk of deteriorating weather with a weather briefing and with knowledge of any local micrometeorology. Last summer, I had a tryout flight for a non-profit organization which flies medical emergencies in Belize, Central America. We had a long discussion on the risks and responsibilities of flying for that organization in that country, and one of the key points is that experience in a given area will be a determining factor as to what weather conditions are acceptable. Two pilots of identical capabilities, one with a year in Belize, one with no time in Belize, will have different weather minima for VFR flight. One knows the risks, one does not. No matter how good I was, until I had local experience, there would be circumstances that I would have to avoid because I didn’t know the risks… and part of my job would be to decline flights that my more experienced predecessors had made safely.

The last risks are the lack of options in case of mechanical failure because, at low altitude, you have much less time to handle a problem before you have to devote full attention to the actual touchdown of the aircraft. If you have carb ice and it takes twenty seconds to regain engine power, will that be enough? If you run a tank dry, will the engine restart in time? or will you be too stressed to handle the problem immediately? Would you fly VFR on a clear day at the altitude that you scud run?

There are risks, and there are foolish risks. Here is my list of foolish risks in scud running:
• Scud running when you are not capable of controlled flight on instruments in adverse conditions (because if you get caught, your only option is to make a forced landing wherever you may be, no matter how unsuitable the terrain. You may have to do this forced landing without ground reference, as it is easy to suddenly find yourself in clouds.);
• Scud running over irregular terrain, such as hills, mountains, or in canyons (because it is easy to get lost, easy to fly up a blind canyon, because localized weather could be much worse in those areas, and because climbing into the clouds is not a safe option);
• Scud running over unfamiliar terrain (because you don’t know the obstacles, the escape routes, the local weather, and because low level VFR pilotage is difficult and rarely taught);
• Scud running in storms, winds, unstable air masses, or in cooling (because you are playing Russian roulette with the weather deteriorating);
• Scud running in an unfamiliar airplane (not make and model, but individual airplane).

Here are the risks:
• Lack of time to handle any sort of problem or emergency;
• Getting lost;
• Having to instantaneously fly IFR and get an IFR clearance.
• Lack of time to see and avoid some other bozo slogging his way through the same pass you are;
• General degradation in decision making and flying skills due to increased stress and fear.

Here are conditions that help mitigate risk:
• Being instrument equipped and current, and being willing and able to declare an emergency and fly IFR all the way to a landing or to VFR conditions;
• Making sure that you always have enough room for a 180° turn in VFR conditions;
• Being relaxed and unstressed before you fly;
• Knowing your route well enough that you don’t need a chart;
• Having a weather briefing, with a forecast of stable conditions.
Note that having all five of these factors in your favor does not make the flight safe, nor does it necessarily reduce the risk to an acceptable level.

The old saying is that 90% of those killed in instrument conditions are buried on VFR days. I don’t have and don’t want enough experience to draw a “statistically significant” conclusion, but… I don’t ever want to go to another funeral of a friend killed scud running. Your friends don’t, either.

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