IFR Planning: Tactics vs Strategy

If you get the big picture first then fill in the details, you wont find many days unflyable


A friend of ours likes to say that flight training is supposed to be difficult and unpleasant, otherwise everyone could learn to fly. We have to wonder if his grim humor forms more of the underpinning of the flight training edifice than were willing to admit.

Perhaps thats one way to explain the illogical way pilots learn the basics of flight planning generally and IFR planning specifically. The IFR written still contains a series of impenetrable questions that require pin point use of a whiz wheel to calculate time en route and fuel burns to a resolution of a couple of minutes – this despite the fact that no one does that in the real world and probably hasnt since the 1950s. (Okay, so youre the exception; send us one of your flightlogs and prove us wrong.)

The fine-point detail nature of IFR training tends to obscure the fact that flying instruments in weather requires both strategic and tactical planning. In some circumstances it can be done safely with very little planning other than a cursory check of weather and notams. The survival skill is knowing when you can launch with minimal planning and when your planning will ultimately confirm that the flight cant be done safely at all.

Quite a little cottage industry has sprung up in the form of sophisticated computer programs that serve to automate the IFR planning task. Whether these are a boon or bust depends on your point of view.

On the plus side, with very little upfront effort required by the user, they gather all the information youll need for an IFR flight – and then some. Theyll instantly calculate time en route and fuel burns, and most will do altitude optimization – an important feature if you fly a turbocharged airplane and want a quick hack on whether its worth it to go high into a headwind. (It usually is, but not always.)

The negative side of flight planning programs stems directly from what theyre good at: gathering every little speck of information pertinent to a flight and printing it out for your consideration. This requires some patience to sort through and you may occasionally ask yourself if youre better off simply cherry-picking the critical data you need directly from an online service and ignoring the rest. After all, on a marginal VFR day, do you really need the weather at 23 stations along a 500-mile route? Probably not.

The subtle danger of flight planning programs accrues on any trip that will be flown to the extreme limits of the airplanes fuel endurance. A computer-calculated range/endurance profile tends to have a degree of assumed accuracy that a back-of-the-envelope WAG doesnt, thus you may tend to believe the computer without a second guess until its too late.

Computer flight planning suffers from the same shortcomings that computers in general do: Bad data in means bad data out. Two areas to watch are winds aloft forecasts that arent accurate – a common occurrence – and fuel assumptions that are overly optimistic. In other words, either the computer has faulty information on actual fuel burn or the aircraft was short-fueled, or both. There are, evidently, many ways to run out of gas and those are just two examples. If you always land with fat fuel margins, this may not be a worry for you.

In any case, strategic planning can be streamlined by asking these questions: Are the weather hazards reasonable? Do I have enough gas for the basic trip and contingencies? Have I guarded against the blind-side notam? Obviously, in the current climate, that last item has taken on new importance.

Killer Weather
Some pilots get irritated with an FSS briefer who, on a clear-blue-and-22 day gives the departure and arrival weather, winds aloft and notams and calls that a standard briefing. But it makes perfect sense if your planning is based on finding and avoiding hazards. If theres a high parked on your route and no weather for 1,000 miles, why not cut your losses, shorten the briefing and move on?

On a day when the ceilings are forecast to be and actually are 500 feet, theres ice and a headwind, you obviously need more data, probably to include the weather at most of the stations en route, pireps on actual icing and tops and enough distant weather to identify a potential bolt hole.

Even if you decide to depart into the face of definite pireps on icing, a last-minute-before-departure phone call to approach or center – the numbers are in the Airport/Facility Directory and can also be provided by FSS – to solicit fresh pireps might tip the decision one way or another. Maybe the tops have lowered or perhaps a Bonanza driver just landed with damp shorts after encountering a boatload of ice.

Thunderstorms, forecast or actual, represent a different kind of planning problem. If theyre isolated general thunderstorms, they may not be especially disruptive of IFR routing, especially in the Midwest where theyre used to that sort of thing.

A line of severe storms, while not automatically unflyable, presents a different problem. Airplanes tend to bunch up around any openings along either side of advancing lines, which may very well put you into a routing or vector-for-separation scenario that wont be comfortable.

If youre IFR, ATC is under no obligation to keep you clear of clouds, let alone bumps and rain. The strategic planning consideration is this: If you dont have radar or sferics aboard, youll have to accept what ATC doles out. If you dont like it, youll have to cancel IFR and negotiate the weather VFR clear of clouds.

Speaking of which, for strategic planning in thunderstorm weather, one workable strategy is to forget IFR and fly VFR, weather permitting. That allows you to navigate around storms at will, without being intimidated into flying a vector youd rather not.

Given the widespread availability of good ground-based weather radar, you could take off right toward an advancing squall line a couple of hundred miles distant, get within sight of it and then land and tie down. When it passes, which it will before your engine cools, you can resume the trip.

Low Vis, Alternates
Low visibility and ceilings represent a different kind of planning problem, especially if theyre widespread. On the east coast, particularly when a winter warm front rolls in over a cold snowpack and reduces visibilities to the RVR ranges for hundreds of miles, the problem is twofold. Will the visibility be good enough to actually approach and land and can you find a legal alternate? On the west coast, its marine layers that sock things in along the shore, leaving the valleys and deserts in the clear.

Although its common to be weathered out of an airport with only a non-precision approach or even a high-mins Cat I ILS, rare is the day when you wont find the runway at an airport with a Cat II/III ILS.

You dont have to be Cat II rated, either. The simple fact is that the lighting on a full-up Cat II runway is almost always bright enough to make seeing and landing on the runway both plausible and safe.

You still need to follow Cat I mins, of course, which are a half-mile of visibility at a 200-foot DA/DH. RVR is not controlling for Part 91 operations; flight visibility is. But the legality is less important than the safety and, for planning, the thing to consider in weather this low is whether theres a doable Cat II runway within comfortable fuel range. In widespread conditions of less than a mile of visibility, it makes little sense to put much faith in a non-precision approach or even a Cat I ILS.

Alternate planning gets sticky in weather like this. I once flew an IFR trip from Reading, Pa., to Baltimore, a distance of 79 miles. The closest legal alternate was Savannah, Ga., 552 miles away. Because all of the forecasts included the probability of sky obscured with 300-foot ceilings and a mile, I filed what the airlines call a paper alternate.

Although I had more than enough gas to go there, I had no intention of actually doing it. I merely wanted to cross all the legal Ts.

On a day that requires a distant paper alternate, you may very well ask yourself if the trip is worth flying. Depending on your risk tolerance for low-vis flying, the answer may be no. Theres no question that widespread fog does add a measure of risk to an IFR flight. On the other hand, if your destination is doable or a nearby airport is, you can turn a no/go into a go.

Another thing the airlines do which GA pilots might emulate is the use of a departure alternate, a nearby airport to duck into if something comes adrift right after takeoff from an airport thats below landing minimums. The airlines have specific requirements for departure alternates but since they arent required under Part 91, you can set your own.

My home airport, Waterbury-Oxford, Connecticut, is on a hill and frequently well below landing minimums. As long as nearby Bridgeport is at or above its ILS minimums – it almost always is because its elevation is 700 feet lower – I have few reservations about departing in 1/8-mile visibility.

The usual cautions apply about departing in visibility that low. Its not for everyone. A more conservative approach is use Part 135 departure mins or the minimums for the approach into the airport youre departing, if it has an approach.

Route Strategies
After a slow start, computer flight planners are getting better at actually having the ATC preferred routes stored in the database. The DUAT services have these available online, too. In those parts of the country where they apply – mainly the northeast, parts of California and around Class B terminals – you may as well ask for and file them because thats probably what youre going to get.

ATC preferred routing usually works on departure-destination pairs and are generated by center host computers. They are usually unvarying but ATC will occasionally assign a non-standard pref route or a secondary choice to relieve weather or traffic congestion.

You can try swimming upstream and filing other than the preferred route, but it will have to be coordinated directly with the ATC facilities in charge. Sometimes that works, sometimes it doesnt. Just remember that anything out of the ordinary may cause a delay at the clearance delivery stage or a reroute farther down the line.

Preferential routing is sometimes altitude or type sensitive, especially in the northeast. This means if you file a low altitude, the host computer might assume youre flying a piston single. If you file a higher altitude along the same route, the host may assume youre a twin or a turboprop and change the routing entirely. Some of these fine points are covered in the A/FD and some arent.

If routing is absolutely critical to avoid weather or an undesirable overwater leg, call the ATC facility directly by telephone before departing. If you explain the reason, theyll work out a deal for you.

Some pilots with intimate familiarity with ATC preferential routes defeat the system by filing subterfuge routes; two separate route segments, one to an airport along the desired route. Upon arriving at the subterfuge airport, announce that youre continuing on to your final destination and need to pick up the clearance.

If this sounds underhanded, it is, a little. But it beats getting pushed 30 miles offshore by a pref routing system that forces you where you dont want to go. If the very idea gives you moral heartburn, try something else.

In most parts of the country, it also works to file direct from departure to destination, saving the hassle of filing an airways route that you may not fly. Remember, however, that in order to fly off-airways routes between fixes, you have to remain in radar contact, which generally will mean filing altitudes that are at or above the local MEAs.

To make things easier for the departure controller, file a fix such as a VOR or an airways intersection thats on your desired course 20 or 30 miles from the departure airport. Center host computers know the fixes in their own databases but they may not have the identifier for a small municipal field 600 miles away. Providing the facility with a local recognizable fix will get you pointed in the right direction.

On DUAT-filed flight plans, the computer places lat/long pairs at points where the routing crosses center boundaries. Center controllers/computers are comfortable with lat/longs, approach controllers arent. So if your flight will remain in approach airspace but will span more than one facility, file a pref route or fixes such as VORs or intersections the computer will recognize.

Tactical Planning
Once the strategic planning is complete and youve decided to go, tactical or in-flight planning comes into play. Weather is often the issue here.

If the briefing revealed hazards such as ice, thunderstorms or low visibility, you may have to seek frequent updates and pireps from Flight Watch. When possible, these are best done after the top of the hour, since thats when FSS gets the latest weather.

Monitoring ATIS/AWOS/ASOS outlets en route is another way to sample changing trends. Is the weather what you expected? Better or worse?

Weather tactical planning will become easier when airborne datalink is available, but until it is, were stuck with the FSS radio link. Dont be afraid, by the way, to ask ATC to solicit pireps if none are available. In icing, youll want to keep constant tabs on cloud tops and you may have to ask for that.

Instrument departures from towered airports or terminals are usually straightforward, but check for published departure procedures. At outlying airports, youll be on your own to either fly the published departure or devise your own. Either way, make sure you know the score before takeoff.

While youre at it, ask the locals if there are any tricks in obtaining a clearance, such as an unpublished RCO frequency or one of those Unicom dial-up gadgets. These are popping up at more airports.

The essence of good tactical planning is staying ahead of developments. For example, if youre flying in low IMC and your destination has only a high-mins non-precision approach, youll want to fly somewhere else if you cant get into your primary destination.

Long before you need it, figure out what airport that will be and let ATC know about it, so the controller can plan for it. Theres nothing wrong with attempting a no-chance approach, as long as you have the gas to get to an alternate where you stand a good chance of getting in.

Getting ahead of the approach is critical in keeping a clear head with regard to planning. Pull the squelch so you can hear the ATIS/AWOS further out and brief up the approach well before you have to set it up and fly it. If another approach would suit you better, ask the controller for it as soon as you can so youll both have time to set up for it. Similarly, if vectors are available but you want the full approach for tactical reasons, ask ATC ahead of time.

If ice is a problem and you know the tops, the full approach can be an advantage, since you can delay descent to the last minute.

At an outlying airport with no tower, how will you cancel? Is there a ground RCO or some other means? Again, if you dont know, ask ATC well ahead of needing the information.

In general, tactical planning is nothing more than looking ahead 15 or 30 minutes and thinking through the possibilities so you dont have to make a snap judgment in the heat of battle. The less of that on an IFR flight, the better.

Also With This Article
Click here to view “Notams Loom Larger Than Ever.”
Click here to view “Route Planning by Computer.”

-by Paul Bertorelli

Paul Bertorelli is a CFII/ATP and editor of The Aviation Consumer.


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