KVUO’s New IFR Approach and Circling Risk
The new instrument approach for KVUO is available, but before you go blasting off into the soup to give it a try for the first time, it might be a good idea to spend a little time on the ground looking it over. And if you have access to a simulator, try a few scenarios to see how the approach works and what risks you might face.
Although the previous LDA approach was also a circling approach, it did have the benefit of nearly lining you up with Runway 8, and if you could see the runway environment in time to descend, it didn’t require much turning to line up on final.
The new RNAV (GPS)-B approach, however, requires turning because it brings you to the KVUO runway at almost a perpendicular angle. Once you see the airport, you have to decide if you’re going to turn right or left, depending on which runway you plan to use for landing.
The added risk with this approach is that the minimums give you very little room for seeing the airport and for maneuvering to line up with the runway.
The missed approach point, NUTOE, is right on the airport, so by the time you get there, you have no room to turn and must fly the missed approach.
So it’s important first of all to descend to the minimum descent altitude, 720 feet for Category A airplanes (90 knots or below) or 740 feet for Category B (91 to 120 knots) after crossing ACDEP at 1,200 feet (or above, but not below).
Here’s where it gets challenging.
Let’s say the weather is close to minimums, 800 feet and 1 mile visibility. That is statute miles, by the way. If you are right on the ball and see the runway at 1 mile and start your turn right away, can you turn 90 degrees (let’s use Runway 8) to the right, then quickly make a 180-degree turn to the left while keeping a visual lock on the runway, all while descending as needed to avoid overshooting or landing long?
I made some rough calculations to see if it’s possible to start a turn at 1 mile from NUTOE and stay within a mile of NUTOE without too steep a bank. Using NUTOE to measure the mile leaves a little wiggle room on the distance, but in any case you must be able to see the airport and the runway during the circling maneuver, so you can’t get too far away if visibility is actually just 1 mile.
Remember that radius of turn is smaller at slower speeds. It turns out that flying the maneuver at 80 knots allows use of a standard rate turn, which is safer. Many airplanes can be flown at 80 knots with some flaps and still have plenty of margin above the stall.
At 100 knots and with a standard rate turn, the radius is larger. The problem here is that by the time you start the 180-degree left turn (base and final), you will likely overshoot final.
I did the calculations with a 30-degree bank, which is usually the limit for traffic pattern flight, and that does help with lowering the turn radius and giving you more room to do the 180-degree turn. But do you feel safe flying below 700 feet agl in 1-mile visibility in a 30-degree bank while you’re looking outside to keep your eyes on the runway?
The KVUO approach procedure isn’t the only one like this; Brackett Field in Southern California has a similar VOR or GPS approach with a perpendicular arrival and minimums of 700 and 1. But the missed approach point is about half a mile from the runway, so there’s a little more room to work with. And the airport has ILS and LOC approaches to one of its runways, so there are less risky alternatives.
This discussion isn’t meant to criticize the FAA for giving KVUO pilots a riskier approach procedure but to encourage pilots to consider the risks inherent to this approach.
A simple way to mitigate the risks would be to set personal minimums, for example, a minimum of a 1,000-foot ceiling and 2 miles visibility, although that still might be marginal. Some professionals recommend a minimum ceiling 500 feet above minimums and 3 miles visibility.
As mentioned, some practice might be helpful. Grab a qualified safety pilot and try the approach out on a nice day and see how challenging it is to turn and descend at the 2-mile- and 1-mile-from-NUTOE marks. Try it in a simulator with various weather settings, from right at minimums to slightly higher ceilings and visibilities.
Knowing what to expect when you have to fly the real approach will go a long way towards setting you up for success.