Wx Watch: Common-Sense Separation

Does compliance with the federal aviation regulations VFR cloud separation rules guarantee safe flying? If you stick to the letter of the law, the answer is an emphatic "no way!"

In dynamic weather conditions, especially when terrain and/or obstacles are factors, strict adherence to the words in FAR 91.155 ("Basic VFR Weather Minimums") can put you in deep, deep trouble. And for instrument-rated pilots, the same can be said of FAR Part 91.175 — where the rules for taking off and landing under instrument flight rules (IFR) are published.

There are at least three general decision-making elements — altitude, experience, and the weather — involved in the act of intelligently flying near clouds when operating under VFR (visual flight rules). One is your altitude. If you're cruising at 10,500 feet msl, have at least five statute miles' visibility, and are staying at least 1,000 feet below, or 1,000 feet above, and are keeping a one-statute-mile horizontal distance from the clouds, you often have a decent chance of avoiding terrain, traffic, and weather.

But what about approaching to land at an airport in Class G (uncontrolled) airspace? In this situation, you are free to legally fly a traffic pattern at an altitude 500 feet below the lowest cloud layer. Let's say that layer is at 1,000 feet agl. And let's say it's daytime and the visibility is a mere one statute mile. Under FAR 91.155, you're legal to fly. Legal, but you'd be hard-pressed to see any nearby towers or terrain. So the risk factor ratchets up significantly. Especially if you are unfamiliar with the airport and its surroundings.

There's another aspect of flying this kind of barely legal pattern that can pose additional risk. Airplanes flying on IFR flight plans may be flying instrument approaches to the same airport. They're legal, too, and they're likely to be descending, in cloud, to and through the airport's traffic pattern altitude to land. Will they see you in time to take evasive action? Will you see them? Maybe, maybe not. A call over the airport's common traffic advisory frequency can go a long way toward informing arriving and departing airplanes of their relative positions. But these calls, although always a very, very good idea, are not mandatory.

Pilot experience

Flying in or near clouds can be a terrifying experience if a pilot is inexperienced. Experience level is another decision-making element. It's one thing to be a high-time instrument pilot with lots of actual instrument time. It's quite another to be a 100-hour VFR-only pilot who is trying to pick his or her way amongst clouds. Here's where experience, and gradual immersion, can pay huge safety dividends.

I've always been an advocate for flight instructors taking primary students on flights in marginal VFR weather — both in the traffic pattern and away from it. This way, the student can see what a 1,000-foot ceiling and three-statute-mile visibility (the VFR weather minimums at airports with controlled airspace designated to the surface) looks like. The same goes for flights at altitude, flying in three-mile visibilities and trying to keep the prescribed distance from clouds. The student quickly learns that three miles isn't much visibility at all.

The same learning strategies can be used with those seeking the instrument rating, and those working on preserving their instrument currency. What better way to stay sharp on the gauges than to fly in the soup, and on approaches shot "in anger" in actual IMC?

Gradual immersion

Sure, a newly minted private pilot can legally fly in one- or three-mile-visibility conditions, and yes, a rookie instrument pilot is legal to shoot approaches to standard instrument landing system minimums (200-foot ceilings, with one-half-mile visibilities). But we all know that this is asking for trouble. It's much wiser to gradually build up our experience in weather flying by gradually exposing ourselves to deteriorating weather. This is where simulators and flight-training devices can be invaluable — but nothing beats the real thing.

VFR pilots should start out their careers flying in near-perfect conditions, on mostly clear days with light winds. This means flying when large high-pressure systems dominate. Once comfortable, it's time to see what flying is like beneath, above, and around scattered (i.e., three-eighths to one-half of the sky covered) cloud layers at the 4,000-foot level, and in unlimited visibility (meaning six-plus statute miles, the official definition of "unlimited" visibility). That's enough to allow easy climbs and descents past these sorts of cloud layers — which usually are associated with high pressure and generally benign weather.

The next step is to take on flights in 3,000-foot scattered, then broken (five-eighths to seven-eighths sky coverage) layers — all the time with unlimited visibilities above and below the cloud deck. Then you can work on down the ladder, flying around 2,000-foot scattered and broken conditions with visibilities dropping to perhaps five or four miles — always taking care to maintain a legal distance from clouds.

Finally — and this should definitely be done with an instrument instructor — it's time to take off, fly, and land in 1,000-and-three conditions. It will probably be an experience that will keep you from ever flying in these conditions again — and that would be a wise choice! However, you'll have earned some valuable weather-flying logbook entries, and be much less prone to panic should you ever find yourself unexpectedly confronting these conditions when flying solo.

Instrument pilots should follow a similar program of gradual immersion. Start out with flying in and out of airports with 2,000-foot ceilings and three-statute-mile visibilities. These are the weather minimums for naming an alternate airport on IFR flight plans, according to FAR 91.167(b). If your destination airport is forecasting 2,000-and-three conditions for at least one hour before to one hour after your estimated time of arrival, then you must select an alternate airport as a destination — in case the weather at your original destination drops below published minimums.

Next, try flying approaches in 1,000-foot ceilings and three-mile visibilities. Then work down to a 500-foot overcast in two-mile visibilities. For these, it's best to have an instructor along, as workloads on approach become higher, and their correct execution more critical.

The next step down is to become proficient flying approaches in 800-and-two, then 600-and-two, conditions. These are the alternate airport minimums for airports with nonprecision and precision approaches, respectively. In other words, if your original destination drops below minimums and you have to fly a missed approach, then at the time that you had filed, your alternate must be forecasting the above minimums at your estimated time of arrival.

What happens if, at the time you arrive at the alternate airport, the weather goes below those magic 800-and-two or 600-and-two marks? Then your approach's standard, published minimums become the new minimums, which brings us to the next level of familiarity.

Finally, become proficient in approaches to 200-foot ceilings and one-half-mile visibilities. And yes, these also should be carried out with an instructor's vigilant eye — and the pilot under the hood or other view-limiting device. Of course, practicing 200-and-one-half approaches in actual conditions is best. This is usually best done in the early morning hours after a frontal passage has soaked the ground with heavy rainfall. Fly your approaches and land, or fly your missed approaches if you don't see the runway environment at decision height. Either way, you have some degree of confidence that as the sun rises, the ceiling and visibilities will often improve.

The weather

The final element is the weather itself. The assumption here has been that your practice flying would be in real-world situations. That's the best way to build discipline, impose enough pressure that's conducive to learning (based on the pilot's proficiency and experience level), and make a confident weather pilot.

What I'm not condoning is flying in any adverse weather for which the pilot or the airplane is not adequately prepared. This obviously means staying well clear of any convective weather, icing conditions, and other dangerous conditions. Understanding and coping with adverse weather is a topic unto itself, and one that provides the monthly fodder for "Wx Watch."

This installment, however, deals with training, and becoming comfortable in the weather conditions for which you are rated. For that you don't need an airplane rocked by turbulence, coated with ice, or subjected to downbursts and wind shear. That — if you're unlucky — can come later, after you've built upon the foundations we've just discussed.

E-mail the author at [email protected].

Take the AOPA Air Safety Foundation online course Weather Wise: Ceilings and Visibilities to learn more about practical weather flying.

Wx Briefs

Frosted

Get ready for a frosted airplane when its skin temperature drops below freezing, and the dew point also is below freezing. That's when deposition takes place — a process where a gas turns directly into a solid — and water vapor in the air turns directly into frost. Depositional frost is a fuzzy, whitish layer of ice crystals that can ruin lift. That's why all traces of frost must be removed before takeoff. Frost also can form on cold-soaked airplanes that fly into warm and moist air, or when they pass through air that is supersaturated with water vapor.

Frozen dew is a type of frost that happens when dewdrops are subjected to subfreezing temperatures. Frozen dew is common after raindrops from a fall or winter cold frontal passage are subjected to the subfreezing temperatures in the advancing cold air. How to best anticipate frost? Check the local ASOS or AWOS broadcast for temperature and dew-point information before you turn in for the night.

Beechjet 400 dual flameout recommendations

Prompted by a June 14, 2006, incident in which a Beechjet 400A experienced a dual engine flameout while cruising at 38,000 feet near Norfolk, Virginia, the NTSB issued a recommendation to the FAA that four actions be taken to prevent future flameouts to the Beechjets' Pratt & Whitney JT15D-5 turbofan engines. There have been three other cases of Beechjet dual flameouts. In April 2000 a Beechjet cruising at 41,000 feet over Brazil had one engine flame out, followed two seconds later by the second engine. One engine was restarted during the descent while passing through 26,000 feet. The other engine did not restart, and the crew diverted for an uneventful landing. In July 2004 a Beechjet 400A operated by Flight Options lost both engines while descending from 41,000 to 33,000 feet over the Gulf of Mexico. Again, one engine was restarted, and a safe landing was made at Sarasota, Florida. In November 2005 another Flight Options Beechjet 400A had a dual flameout, while descending out of 38,000 feet in visual conditions. The engines could not be restarted, and a dead-stick landing was made at Jacksonville, Florida.

Investigators suspect that ice formations can occur within the engines at high altitudes if enough moisture is in the air. Even with extremely low outside air temperatures, the NTSB pointed out, the heat generated by engine components can cause ice crystals to melt while passing through the fan section, then refreeze on the JT15D's inner compressor stator to the point where engine flameout would occur. The NTSB noted that all of the flameouts occurred at high altitude, near convective activity, and that in the Sarasota, Jacksonville, and Norfolk events, the flameouts happened after a power reduction.

The NTSB recommends that the FAA require:

• Beechjet 400 pilots to activate engine ignition and anti-ice systems at high altitude when in or near visible moisture, near thunderstorms, and before any power reduction if not in or near convective activity.
• Raytheon to incorporate the information about anti-ice operations and ice formation contained in Raytheon Safety Communique No. 269 (issued after the Jacksonville incident) into the Beechjet 400 airplane flight manual, and those of other airplanes using JT15D engines.
• Manufacturers and other industry personnel to undertake research to develop an ice detector that would alert pilots to internal engine icing, and require that it be installed on all new production turbofans, as well as retrofitted to existing turbofan engines. — TAH