Thursday, May 29, 2008
The Desire To Go Lower
Making sense of low IFR approaches
Essentially, CAT I includes any nonprecision instrument approach procedure having minimums not less than 200 feet height above touchdown (HAT) and a RVR not less than 1,800 feet. This means that CAT I includes all precision straight-in, nonprecision straight-in and nonprecision circling approaches. Precision circling appears to be missing from this list. An ILS that ends with a circle-to-land maneuver, however, uses a nonprecision minimum descent altitude that’s higher than the ILS decision altitude. Accordingly, other approaches—such as LOC, LOC BCRS, LDA, SDF, VOR, NDB, GPS and RNAV (and LP/LPV)—are each considered to be CAT I.
Most Part 91 operators are limited to CAT I approaches and their respective minimums. If you want to go lower than 200 feet HAT and 1,800 feet RVR, you’ll need a CAT II or CAT III authorization from the FAA. The CAT II authorization is spelled out in FAR 91.193: “The Administrator may issue a Certificate of Authorization authorizing deviations from the requirements of sections 91.189, 91.191 and 91.205(f) for the operation of small aircraft…if the Administrator finds that the proposed operation can be safely conducted under the terms of the certificate.” Basically, this authorizes a single-pilot operation and throws out the requirement for a CAT II manual, relaxing some of the CAT II equipment requirements.
Getting a CAT II authorization, however, isn’t easy. It’s demanding and requires a great deal of training and concentration. Pilots must complete an FAA checkride with the FSDO, proving that they can safely operate the aircraft to the lower minimums. This requires an intimate knowledge of the ILS system, including the approach lighting systems, runway markings, centerline lights, touchdown zone lights and a slew of other details (dimensions, distances, colors, etc.) that most instrument pilots take for granted. Essentially, the FAA can throw the instrument PTS at pilots, who must be ATP-like flawless.
After a pilot earns Form 7711, the Certificate of Authorization, he or she can’t fly just any IFR-certified airplane to CAT II minimums; the pilot is only authorized to fly to those minimums in the airplane in which the pilot was qualified—down to the N-number. Authorization is valid for a two-year period. Additionally, the straight-in landing runway must also be approved for CAT II operations. A pilot can’t just choose any instrument approach and fly it down to CAT II minimums.
What are the benefits of getting a CAT II authorization? In the end, it would seem that CAT II authorization doesn’t extend the CAT I ILS minimums much, considering that the lowest CAT II authorization is a 100-foot decision altitude and a 1,200-foot RVR (CAT III is even lower). While this appears like a small step, it’s actually a giant leap, given that many VLIFR events rarely happen below these CAT II minimums. In other words, if you’re authorized to the lowest CAT II minimums, you’ll rarely get shut out of an airport with a CAT II authorized approach.
In many low IFR operations, a missed approach becomes an important review item before executing the approach. The lower authorization just might be enough to get you on the ground without the need to execute that missed and divert to an alternate airport. Even with full fuel tanks, an unforecast widespread IFR event can stretch those fuel reserves. Ultimately, the authorization gives you more flexibility when Mother Nature is showing her bad side.
A CAT II authorization isn’t a pilot rating, but an authorization that adds another dimension to your instrument piloting. A training regiment to prepare for a PTS on a topic like this will provide you with a better appreciation for the challenges of a VLIFR event. It will hone your instrument hand-flying and keep you on your toes, since most CAT II ILS approaches occur at busy airports. Finally, it may give you just enough wisdom to break that important link in the accident chain, thus avoiding a tragic accident.
|Weather Forecast Gone Bad|
|While not likely a direct factor in the accident, the 1200 UTC scheduled NWS terminal aerodrome forecast (TAF) for Portland wasn’t anywhere near what Mother Nature had in mind that morning. Technically, with a departure at 1430 UTC, the pilot wasn’t even required to file an alternate, given a forecast of greater than six statute miles visibility and an overcast cloud deck at 2,500 feet from 1300 UTC through 1700 UTC. Moreover, the forecast beyond 1700 UTC was a meager scattered layer at 3,000 feet with good visibility below. Assuming the pilot received a preflight briefing, he departed Klamath Falls, Ore., at 1430 UTC, thinking the weather was going to be VFR when he arrived at Portland. |
Seven minutes after his departure, at 1437 UTC, the NWS forecaster issued an amendment to the Portland TAF. This amendment wasn’t a strong signal that bad things were about to happen. The prevailing conditions beginning at 1500 UTC were scattered clouds at 100 feet and scattered clouds at 4,000 feet, along with two statute miles visibility. Additionally, between 1500 UTC and 1700 UTC, the forecaster felt the need to add a TEMPO group, bringing down the ceiling to 100 feet with one statute mile of visibility.
Assuming he was monitoring the weather while en route, this forecast might have gotten the pilot’s attention. But he’s already in the air and likely only an hour away by this point. With a strong indication that the weather is trending better with time, what does it hurt to “look and see” at least once or maybe twice?
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Labels: Accident Statistics, Flight Hazards, Flying Skills, IFR Flight, Learning Center, Pilot Skills, Safety