Living With Mins

Personal weather minimums wont solve all your problems, but theyll keep you out of most of the trouble


The pilot-in-command is in control of the safety of the passengers and care of the airplane. His judgment is the deciding factor in whether the flight should go or not go. His decisions are based on his evaluation of the conditions existing for a safe flight. He doesnt give in to the demands or influences of the passengers.

He also knows he cant always rely on the FAA weather minimums as guidelines for the safety of his flight. FAA minimums for flight – both VFR and IFR – are the absolute minimum weather conditions to legally fly. They are not – nor were they ever intended to be – the standard every pilot can use to determine the level of safe operating procedures.

Not every pilot will make the same decision, even given identical sets of weather circumstances. Its up to each pilot to adjust the legal minimums to fit the equipment he will use and his own instrument flight skills and experience.

An IFR pilot who has let his proficiency lapse is risking everything – including the lives of his passengers and the aircraft – when he tries to fly to the published approach minimums. Likewise, the average VFR-only pilot is pushing his luck when he tries a cross-country flight with a 1,000-foot ceiling everywhere along the route.

Pilots need to set their own weather minimums, considering not only the ceilings and visibility, but also their own fitness for the navigation and aircraft control challenges ahead. They need to understand the limitations of their experience and their outs if the weather is worse than expected.

They need to think about rain, thunderstorms, winds, turbulence and darkness. There is no operations officer, flight instructor or dispatcher to turn to for advice. The weather briefer, if asked, will give the forecast conditions, but wont try to direct the flight. Its worth more than a casual thought or two.

When it comes to setting weather minimums, there are basically four categories of pilot/airplane combinations. There are VFR pilots in VFR airplanes, pilot/airplane combinations in which one is capable of IFR flight and the other is not, out-of-practice IFR pilots in IFR airplanes and proficient IFR pilots in IFR airplanes.

Of course, other differences exist, such as the pilots skill and experience and the aircrafts ability to fly in icing conditions, but these four combinations go the furthest in defining what approach the pilots should take in developing weather minimums.

Some pilots are steadfast in their opinion that the instrument rating just isnt worth it to them. Their use of airplanes is pretty much limited to flying VFR, point-to-point and not much else.

These pilots generally are aware of their own capabilities, and the limitations of their airplanes, so they operate safely most of the time. They are used to not flying sometimes when they want to. They may sit for a while, waiting for VFR weather, but theyre OK with that.

Next in line is the group in which either the pilot or the airplane isnt up to instrument flight. This includes accomplished instrument pilots flying VFR-only airplanes as well as non-rated pilots flying airplanes that, in other hands, would be capable of making a trip in instrument conditions.

Many of these pilots have had some instrument training, but for whatever reason never got the ticket. Some of these guys occasionally get perilously close to IFR conditions. As they get more skilled at scud running they occasionally tangle with the real stuff. The weather overwhelms some of them before they can get out.

After that you come to what some consider the most dangerous of all general aviation pilots. Theyre the ones who made the effort to pass the instrument checkride, but they seldom operate in actual instrument conditions.

If they use their skills at all, it is usually to climb through a cloud layer to cruise in the clear on top. The instrument approaches they make dont come close to minimums, and some even hold to 1,000-foot ceilings. They seldom remain instrument current, scrambling to find a safety pilot as the clock ticks down to an instrument proficiency check.

The trap springs on these pilots when they stumble into IFR that has gone down below the forecast. Sure they have the rating, and maybe theyre even flying under IFR when theyre suddenly faced with cutting a NDB approach to an airport they must make because of fuel.

Then there is the smallest group of instrument-rated pilots: the proficient IFR pilots. They use their rating constantly.

I once had a student who was one of these pilots. He was a businessman who wanted to get the most out of his new Piper Archer. He was an average student, but he asked lots of questions. The maneuvers he didnt do well he wanted to repeat until he was excellent.

He wanted to work in actual weather. We flew up and down the California coast, into Oregon, Arizona and New Mexico in every kind of weather. He passed his written, oral and flight with flying colors, first time out. He even had mastered the AIM holding pattern entries.

He flew on business and filed IFR on every flight he made. He remained proficient. He did stick to a set of personal limitations that we developed, but he also flew a lot of actual IFR, including 200 hours in two years.

One day he stopped by in a new A36 Bonanza he had just purchased. We went back into another 50 hours of intensive training. Hes up to about 2,500 hours now, with about 600 of it actual instrument conditions.

Can any pilot do this? Well, yes, if they have the motivation and the money. Do they? About as frequently as a Century plant blooms.

Setting Minimums
Whatever the pilots level of experience and current flying profile, every pilot-in-command needs to set his own personal weather minimums, based on the limitations of their experience. Thats a tough decision.

Every pilot is a hero – and very touchy about his status among other aviators as well as in the eyes of his passengers. Other pilots may talk of flying an approach down to the legal minimum with a wink and nod that implies they actually descended below decision height, leaving you to wonder why you scrubbed a flight because of 500-foot ceilings.

Whether flying VFR or IFR, a pilot needs to establish – in writing – the minimums from which they will not deviate. Not under pressure from friends or family or bosses. I once had an instructor who told me to make cautious and conservative decisions about flying in really bad weather. As near as I can tell, he said, Youre dead a long time.

Some of the pressure to go comes from family and passengers who dont understand why you cant fly in weather that hardly slows down the airlines. Theres a conviction in pilot circles that flying in poor weather is one sign of having the right stuff – and the worse the weather, the better.

The trouble is, if you ask a pilot what constitutes weather too lousy to fly in, youre likely to hear about low ceilings and poor visibility. But it can be more, much more.

How about adding strong winds, precipitation, turbulence, hot or cold extremes, and high altitudes without on-board oxygen. Also add smoke, haze, smog, or icing with extreme conditions of humidity and temperature.

Low Ceilings
Although most pilots view low ceilings as a primary criterion for determining whether the weather is too low to fly, remember that the ceiling is the height above the ground where the lowest cloud layer is described as broken or overcast.

That doesnt mean youll have a clear view of the airport. Haze, glare and partial obscuration can severely degrade visibility, especially when flying into the sun. Most instrument pilots have had the experience of shooting an instrument approach to an airport that was legally VFR because they simply couldnt see the airport from a few miles out in spite of the reported ceiling and visibility.

In addition, making an approach to an airport thats IFR may not be possible even if the reported ceiling is above minimums, simply because of ragged bases or scattered clouds that werent recorded during the weather observations.

For VFR pilots, the ceiling further affects decision-making because of the rules for cloud clearances. To fly legally in controlled airspace, you need to stay at least 1,000 feet under the base of the clouds. In uncontrolled airspace, the pilot is required only to stay clear of the clouds.

Lets say there are scattered clouds with bases below 1,000 feet agl and the sky is partially obscured. A VFR pilot can get a takeoff clearance from a controlled airport, but youd have to ask yourself if legal was particularly safe.

When en route, the pilot would be faced with threading through the clouds and other obstacles, such as transmission towers and terrain. It may not be possible to fly long distances under a 1,000-foot ceiling. Even if its legal, it may not be particularly safe. Weather changes during this type of a flight can range from uncomfortable to disastrous.

Marginal Visibility
Its worth remembering that visibility is often determined by a ground observer. The observer looks for prominent objects a known distance away, and the farthest one he can see defines the visibility. Automated systems use a sensor that measures how much light is lost from a pulse of known intensity.

Both systems have their advantages. A human observer can look in several directions and come up with an average visibility around the airport. The sensor is more precise, but can only see the weather at the instrument.

In flight, a pilot can only guess at what visibility lies ahead. You can look at objects on the ground, but since you dont know exactly how far away they are, you can only make a guess. Comparing a landmark youre flying over with one in the distance is easier if both are marked on the sectional, but that doesnt help if youre on top of a cloud layer. Experience helps make the guesses more accurate, but theyre still guesses.

When visibility fades, real-world hazards move in to replace it. The known is replaced with the unknown. At 100 mph, the airplane takes 2 seconds to run the 100-yard dash.

Thats why scud running and descending below minimums is so dangerous. Obstructions appear out of the murk and flash by before you can react. Sometimes youll miss em; sometimes you wont.

A more insidious danger is that the poor visibility can mask weather ahead that may be even more threatening. Embedded thunderstorms are one example, but a thunderstorm doesnt have to be embedded to be invisible – and threatening – to a pilot flying in low visibility 10 miles away.

For VFR pilots, the hazard of low visibility is that you can fly right into solid IMC before you even know it. Even if you sense some kind of weather problem up ahead, the murk on all sides sets the stage for a confused decision. If you cant see whats up ahead or on either side, its easy to get disoriented.

Clouds or smoke can mix in the haze and create a false horizon. Its easy to lose all references in a passing shower, forcing a quick switch to instrument flying.

To get an idea of how reported visibility can be misleading, consider the case of a 580-hour pilot who was seen about 1 p.m. making a careful preflight inspection of his Cherokee 140 at Chatham, Mass. He said he was going for a local flight and didnt file a flight plan. He took off in VFR conditions at about 2 p.m.

About 1.7 hours after departure, witnesses observed the airplane flying south toward the shoreline, in and out of clouds, at about 700 feet agl. When the airplane reached the shoreline it turned east, paralleled the coast, and re-entered the clouds.

The airplane was found submerged in six feet of water, one mile farther east. An examination of the wreckage revealed no pre-impact failure of the engine or the airframe.

The automated weather system at the airport was reporting IFR conditions until about noon, and by the time the pilot departed the system was reporting a 12,000-foot ceiling and 10 miles visibility. An hour after his departure, the clouds had re-formed to create a 200-foot ceiling with a half-mile visibility.

One witness said, Visibility was low in patchy fog and the plane disappeared about a quarter-mile from us.

Strong Winds
Many pilots neglect to consider the winds when making their decisions on personal minimums. This is particularly true of pilots who have gotten lazy about tracking the flight as it progresses GPS direct to its destination.

Strong headwinds can eat into fuel reserves quickly. Lets say youre flying a 120-knot airplane on a 360-nm leg and have just enough fuel aboard to make that trip with VFR reserves. Throw in an unexpected 20-knot headwind component and you run out of gas a few miles from the airport.

Pilots on instrument flight plans may face even more trouble. Unexpected vectors for traffic or missing an approach at the destination can result in a critical fuel situation.

The accident record is filled with examples of pilots running out of fuel an hour or more after they planned to be at their destination. As its logical to assume no one tries to run out of fuel, such inattentiveness can only be blamed on the pilots lack of diligence in planning the flight and monitoring its progress.

A flight log is a simple way to keep track of planned vs. actual ETAs. The more detailed you make it the earlier youll detect when the actual flight plan is diverging from the intended one.

Another problem with strong winds comes from crosswind landings. Though confident pilots are quick to point out that an airplanes demonstrated crosswind component is advisory rather than a limitation, the fact remains that many pilots have woefully inadequate crosswind technique.

Most of the trouble I see with crosswind landings seems to involve bounced landings or ballooned flares, with a failure to hold the crosswind correction.

Although the problem shows up as lousy crosswind correction, its also induced when pilots carry too much speed into the landing to compensate for gusty conditions. A time-honored rule is to add half of the gust component to your approach speed, but many pilots interpret this as carrying that speed into the flare, or they add more than that to create a fudge factor.

The sad fact is that runway loss of control is one of the primary causes of light aircraft accidents. Many of them are caused by poor speed control, which is in turn induced by strong wind conditions.

Another wind-induced flight condition is turbulence. Turbulence can be caused by gusty winds or wind blowing over ground obstructions or mountains. Rising warm air also can generate turbulence, as well as air changes in the vicinity of thunderstorms.

There are classifications for turbulence – light, moderate, severe and extreme – but dont expect pilot reports to be reliable because theyre tied up with the speed, type and weight of the aircraft and the anxiety level of the pilot.

Analyzing the kinds of conditions that might create turbulence can help you create a smart flight plan that avoids it. If you get caught in it, the best solution is to reduce speed and make smooth corrections for the up and down blasts, allowing altitude variations if necessary.

Rain and Thunderstorms
There are several flight hazards associated with rain. Some are operational, such as using carb heat and leaning the mixture, while others directly affect the safety of the flight.

Light rain and steady drizzle will reduce forward flight visibility, leading to the same kinds of problems described earlier. Precipitation can be especially troublesome during the approach to the airport, because the airplane is slower and the prop wash is reduced, making it easier for water to collect on the windshield.

There also are safety questions tied to standing water on the runway. Your preflight preparation should include familiarizing yourself with the type of runway youll be landing on, particularly if theres rain in the forecast. A shower that would quickly be a non-event on a grooved runway can create a serious hydroplaning problem on a less-sophisticated surface.

Thunderstorms are a well-recognized threat to aircraft, and certainly any VFR pilot who sees rain coming out of the bottom of a thunderstorm isnt going to try to cross through it. Likewise, any IFR pilot who sees an anvil or a boiling cumulus cloud looming ahead isnt likely to continue without a deviation.

However, there are some hidden dangers around thunderstorms that can catch unwary or unprepared pilots, notably shelf clouds. These clouds can extend far ahead of the core thunderstorm, obscuring it from the view of an approaching airplane. The pilots bounce above, below or through the clouds, oblivious to the danger that lurks within.

Personal minimums and thunderstorms dont really go well together. The mantra must be to avoid thunderstorms. How big a berth to give them, however, can depend on what youre flying and what you see out the window.

Avoiding a thunderstorm by 20 miles strikes some pilots as excessive, while others dont want to be in the same county. Both pilots are right in some circumstances, because thunderstorm intensity varies so much. The best bet is to play the thunderstorm game extremely conservatively.

Night Flight
Flying after the sun goes down gets a lot of pilots into trouble. For my money, night flight is really instrument flight, and needs to be treated with care. You can have all kinds of things happen to the airframe and engine in daytime, and the outcome will be from fair to excellent. At night you can count on poor to fair results from emergencies.

The kinds of minimums you should consider for night flights include routing yourself over areas that are as friendly as possible to mechanical failures. You might also consider the kinds of approach lighting at the destination airport, opting for more lighting if your night skills arent used much.

Whether flying IFR or VFR, consider that weather ahead is more difficult to detect, with the possible exception of embedded thunderstorms that light up the clouds.

Successfully completing a night flight, just like any other part of flying in less than ideal weather, involves setting personal minimums that allow you to complete your flight as planned as frequently as possible, while still maintaining as much of a safety margin as you can.

Striking that balance is sometimes difficult, but coping with the pressures from others, your demands on yourself and the realities of the weather are more of a test of a pilot-in-command than stick and rudder skills will ever be.

Also With This Article
Click here to view “Coping With Pressure.”

-by Ray Leis

Ray Leis is an ATP, CFII and FAA Aviation Safety Counselor.


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