Posts Tagged ‘Category II’

Exemption 3585

Tuesday, February 26th, 2013

If the airlines didn’t fly every time the weather was less than ideal, they’d never fly. As a result, technology and rules are in place to maximize efficiency and opportunity while minimizing risks. One example lies in getting airplanes off the gate when the weather at the destination is forecast to be below minimums.

Like everyone else, the standard IFR 1-2-3 rule applies: If the weather at the destination from one hour before to one hour after the ETA is forecast to be less than 2,000 feet and three miles, an alternate is required. This is no big deal, obviously, and many of us have left with the weather forecast to be right at the minimums for the approach.

However, sometimes the forecast calls for a possibility of weather that is going to be temporarily below the landing minimums. In FAA weather lingo, we call this “conditional phrases,” and they consist of BCMG, PROB, and TEMPO. For example, the main body of the forecast may have the visibility at one-half mile, but a TEMPO phrase may show a possible drop to on-quarter mile at the ETA.

When this happens, the airlines that have been granted approval to do so can use what is called Exemption 3585. Under the terms of the exemption, the flight will be required to have not one, but two alternates. Further, the method used to determine the alternates is changed as well.

Remember, the airlines do not use the 600-2 and 800-2 rules that GA use for determining the suitability of an alternate; the rules for determining a Part 121 alternate are beyond the scope of this post, but suffice it to say, it’s possible that an airport could be an alternate as long as the forecast is calling for weather of at least 400 feet and one mile.

Under Exemption 3585, the forecast (again, we can use conditional phrases) at the ETA for the first alternate must call for a forecast of no worse than one-half the visibility and ceiling required for the approach. In our example of a 400 and one, the weather at the first alternate can’t be forecast to be less than 200 and one-half.

Looking ahead to the second alternate, the FAA has a pretty simple criteria: This one must be essentially a sure thing. The forecast for the second alternate can also utilize conditional phrases. However, this time, the forecast must call for weather—even with conditional phrases—that equal the ceiling and visibility that can be used for the approach. No reductions are allowed. In essence, if the conditional phrases must have such good weather, it stands to reason that the main body is going to be for nearly VFR conditions.

There is one other option: Category 2 approaches. CAT II approaches can be flown with a runway visibility range (RVR)  reading of 1,200 feet—that is, one-quarter mile of visibility. Such approaches are a pretty hair-raising experience. However, CAT II approaches are a significant investment because of the maintenance requirements for the airplanes, and if the airline does not have a great deal of diversions in a calendar year caused by low visibility, CAT II isn’t worth the cost. Exemption 3585 does the trick.

This is a fairly simple explanation, and the variety of possibilities can get complex and tricky, but Exemption 3585—sort of a poor man’s CAT II that was originally put together for People Express—is an indispensible tool, and if you should ever be hired by a regional, you will spend a lot of time in training dissecting Exemption 3585.

The sad thing is that while you while you will spend hours learning 3585, you will rarely use it. In 16 years of airline flying, I have taken full advantage of 3585 fewer than a dozen times. Category II on the other hand….—Chip Wright

Truly rare events

Friday, April 6th, 2012

For more than 20 years I’ve been flying airplanes, 15 of them for an airline. As a student and a flight instructor, one skill I practiced repeatedly was the missed approach (or go-around for VFR flying). It’s a critical task to be able to do in any possible landing configuration in any airplane. If you want proof, try doing one in a heavy Cessna 150 with 40 degrees of flaps on a hot day. It’s a challenge, to say the least, and it requires a fair amount of finesse to do well. As an instructor, I probably did no fewer than five go-arounds or missed approaches on a given day. Any that were done for real were almost always done because the preceding traffic was still on the runway.

In airline flying, however, they are exceedingly rare. Controllers handle the spacing, and even when there is a snafu, the missed approach is almost always done in visual meteorological conditions, and it almost always starts from an altitude of 500 feet or above.

What is even more rare, though, is to do one because of weather. I can recall doing fewer than 10 for wind shear or a microburst that beat me to the airport. And I have only done two—two—because we could not see the runway. The first one was an ILS in low ceilings but with good visibility beneath in Charleston, West Virginia. In fact, we saw the runway on the go-around. We came back around and landed on the second try.

The most recently was in January 2012. I was flying the right seat with a simulator instructor in the left. Both of us were slightly out of our element. The weather everywhere that day had been lousy, and we’d already done three ILS approaches to minimums, including our previous leg into Cincinnati that morning. The weather was down to a ceiling of 100 feet and a reported visibility on Runway 18L of a half-mile with the runway visual range hovering at 2,400 feet. The previous aircraft got in, but the crew reported that it was awfully close. We quickly reviewed the missed approach procedure again and went over the calls.

Since I was the nonflying pilot on this leg, it was up to me to make the altitude calls, and it would be up to me to call for the missed approach if the captain did not see the approach lights or the runway. One thing that experience teaches you is that the color of the clouds changes fairly dramatically when you near the base and will break out. These clouds stayed battleship gray. Further, we were flying into the sun, which did not help. The radar altimeter told us when we were crossing the Ohio River. The river and its deep valley have a stark impact on the local weather, and today was no exception. There was no sign of the runway at 500 feet above the minimum descent altitude. No sign of it either at 200 feet or at 100 feet. At the MDA/decision height, I called missed approach. We never once saw the ground.

Normally, an airline crew going missed is all thumbs because of the lack of practice. This one, though, was right out of the book. We had to deal with a flurry of activity in the ensuing minutes as we planned our next course of action. The flight behind us also went missed, and the controllers immediately turned the airport around, which opened the Category II approach to Runway 36R; the RVR was down to 1,600 feet, and the ceiling was holding steady. Our immediate concern was whether or not we had the fuel to do another approach and still safely divert. A call to our dispatcher confirmed that several airports within close range had VFR weather. His fuel computations matched ours, so we decided to try it again.

They only procedure that is on par for me as an unseen runway is a Category II ILS. This was only my fourth one, and it was my first from the right seat (we fly the CAT II as a captain’s-only maneuver). Being two miles from the top of the river valley made all the difference. We got the lights in sight just before reaching our DH, and in the blink of an eye, we had the runway in sight.

There is a lot of satisfaction in executing a difficult maneuver correctly, and a go-around can certainly qualify, especially with tail-mounted engines and wings with no slats. But the training and practice pay off, and that is critical when you are starting the maneuver so close to the ground that you might actually bounce. I haven’t done that yet, so I can’t help but wonder what it’s like…—Chip Wright