Page 32 - Volume 20 Number 7

Twin Proficiency:
by Thomas P. Turner
WI hen to Cancel IFR
n last month’s column, I described a very-near
collision I witnessed on the runway of a non-towered airport. The pilot of a turboprop twin, obtaining his IFR release on an 1,100-overcast day, apparently not monitoring, and certainly not transmitting on, the CTAF (Common Traffic Advisory Frequency), pulled out in front of a Cessna Citation that was on short final. The Citation pilot executed a go-around, side-stepping left to avoid the climbing Piaggio Avanti, then flew a left- hand pattern to return and land uneventfully. Although most of the blame for the near-collision – if indeed blame is affixed – goes to the pilot of the Avanti for not determining the way was clear before taxiing onto the runway, the Citation pilot may have made some mistakes too.
Let’s look at this event – realizing that this is very speculative – from the cockpit of the Citation. The pilot (or crew; we’ll use the singular) flew the Runway 18 instrument approach (ILS or RNAV/GPS, it doesn’t matter) and broke out of the 1,100-foot ceiling a few miles from the airport. Wichita/Colonel James Jabara Airport (figure 1), where this event took place, has a 1,420-foot field elevation. This means the cloud bases (verified by several pilot reports, including mine when my student and I departed shortly afterward) were at about 2,500 feet MSL. On the ILS glideslope/LPV glidepath, this put the Citation about 1/3 of the way from the Final Approach Fix (FAF) to the Missed Approach Point (MAP) ... roughly three and a half miles from the airport when it broke out. Notably, the first I heard from the Citation on CTAF was when its pilot reported “four miles out,” and I saw the jet’s landing lights shortly afterward.
Now, take a look at the airspace the Citation was in at the time. Figure 1 is a segment of the Sectional chart. Jabara (KAAO) is depicted by the upper-left magenta airport symbol. What type of airspace was the Citation in at approximately 1,100 AGL, roughly three miles from the airport?
The Citation was in Class E airspace. Class E airspace can begin at the surface, at 700 AGL, at 1,200 AGL, at 14,500 MSL, or at any different altitude where charted. Now look at Figure 2, highlighting the depictions of airspace around other airports in the area. See Augusta (3AU) and El Dorado (KEQA), and contrast them with
30 • TWIN & TURBINE
Figure 1
Jabara (KAAO). The arrows point at key features of these airspace depictions. What is the major difference?
The red dashed ring around Jabara Airport signifies that Class E airspace extends all the way to the ground – the surface area. KEQA and 3AU are more typical non-towered airports, with the base of Class E airspace at 700 feet AGL. In Class E airspace under 10,000 feet MSL, pilots operating under Visual Flight Rules (VFR) must maintain at least three miles’ flight visibility (visibility was greater than 10 miles on the day of the near collision). They must also remain at least 500 feet below, 1,000 feet above and 2,000 feet laterally from clouds (figure 3).
The Citation pilot had obviously cancelled IFR, or Air Traffic Control would not have given the Piaggio pilot his IFR release to take off. Hence, the Citation pilot was flying under Visual Flight Rules, and was required to maintain VFR minimums. Yet, 500 feet below the cloud base would have been about 600 feet AGL, or 2,000 feet MSL. The Citation pilot appears to have canceled IFR as soon as he broke out of the clouds, but well before he could legally operate under VFR.
It’s very likely the controller asked the Citation pilot to cancel IFR as soon as possible so the Piaggio could be released, in time for a G36 Bonanza behind the Citation on the approach to be cleared, and for my student and me to be released on our own departure clearance after that.
JULY 2016