Dark Horizon

Night VFR over a remote area can mean little or no natural horizon to help maintain aircraft control.

0

My most recent night flight involved a relatively short hop across the Florida peninsula. It was one of those humid, heavy summer nights when remnants of the days thunderstorms were still about, forcing FLIB and airliner alike to seek alternate routes and taxing controllers who just wanted a calm evening.

Still, I had a few things going for me: Training, currency, experience and the occasional cluster of ground lights denoting a small town. I filed IFR at 8000 feet for this short hop, because I didnt want to try doing it at a level low enough to stay VFR-legal (there are way too many cellphone towers out there these days), and climbing high enough to get above the buildups wasnt practical. It was yet another case where having the instrument rating to spend maybe 90 seconds punching in and out of billowing clouds during a 45-minute flight meant all the operational difference in the world.

This was one of those nights where the natural horizon wasnt all that apparent, due to the moist, summer haze over south Florida extending up to my altitude, plus the number and size of the buildups. Although I could see each buildup, and navigate around or through them, the natural horizon wasnt consistently visible.

It would have been a tough night to fly VFR, though it certainly could have been done, mostly by committing to deviate early and often, and remaining well clear of buildups to ensure a visible horizon.

Of course, this wasnt the first time my instrument rating came in handy at night, and it wont be the last. As were about to learn, trying to fly VFR at night in some areas at some times is a very low-risk operation while, in other areas and at other times, its impossible.

Background

On October 26, 2007, at about 2006 Mountain time, a Piper PA-28R-200 experienced an in-flight breakup while in an uncontrolled descent over mountainous terrain about 21 miles southeast of Cedar City, Utah. The airplane was destroyed during the breakup and post-impact ground fire. The 200-plus-hour non-instrument-rated private pilot, who co-owned the airplane, and his passenger were killed. Dark nighttime visual conditions prevailed. The flight originated from Bountiful, Utah, about 1815.

Earlier, at 1842, the airplane was at 9500 feet when it departed Salt Lake City airspace and flight following services were terminated. There were no further communications with the airplane. Recorded radar data for the area revealed the southbound airplane had climbed to 12,600 feet by 1958:06 but descended to 11,100 feet by 2005:04. The airplane then commenced a clockwise turn while continuing to descend. The airplane was last recorded on radar while on a northwesterly track at 2005:34, and seconds earlier had descended through 10,800 feet.

No person reported observing the accident airplane descend or impact the mountainous terrain. No homes, lights or roadways exist in the accident sites vicinity.

Investigation

The airplanes fuselage, wings, empennage and other non-structural components were found scattered over an estimated 950-foot-long by 350-foot-wide oval-shaped area, and within a radius of 550 feet of the main wreckage. The long axis of the wreckage distribution path was oriented on a magnetic track of about 030 degrees. The main wreckage was located about one-third mile from the last recorded radar position. Examination revealed the airplane experienced an in-flight breakup.

In addition to the widespread wreckage, evidence leading the NTSB to conclude an in-flight breakup occurred include finding both outboard wings separated from the inboard wing section approximately at the wing spars production splice. Additionally, both wing spars showed evidence of failing in a downward direction. Similarly, both upper and lower surfaces of the stabilator spars left and right sides were bent downward. The spar itself was twisted in a leading-edge-downward direction, and the entire span of the stabilator was bowed in the same direction. Unless subject to heat-related distortion in the after-impact fire, all spar fracture surfaces exhibited characteristics consistent with bending overload or compressive buckling signatures.

Conditions in the vicinity did not include reports or forecasts of convective activity. No evidence was found of conditions precluding VFR flight. However, a layer of smoke generated by California forest fires over the preceding days had drifted over Utah and may have impaired horizontal flight visibility. According to the NTSB, a Civil Air Patrol pilot who searched for the missing aircraft opined the flight visibility in the accident site area would have been very bad at night.

Probable Cause

The National Transportation Safety Board determined the probable cause of this accident to include: “The pilots failure to maintain aircraft control while in cruise flight due to spatial disorientation. Contributing to the accident were the dark conditions.” Theres not much to add here: The pilot lost control of the aircraft while in cruise flight, probably because the natural horizon wasnt visible and hed had inadequate training and/or experience in flying the airplane solely by reference to flight instruments. Its a too-familiar story.

Some obvious lessons can be drawn from this accident, including admonitions for pilots to refrain from night VFR over remote areas (maybe thats why Canada requires a separate rating for night VFR). Another admonition is for pilots to obtain the instrument rating as soon as they can after earning the private certificate if they intend to use a personal airplane as transportation. A better understanding of spatial disorientation, including how and when pilots are most susceptible-wouldnt hurt a thing, either.

Theres nothing fundamentally wrong, risky or unsafe about nighttime VFR presuming cooperative weather. Near populated areas, ground lighting not only illuminates your checkpoints, it helps you keep the dirty side down. Away from the madding crowds, it gets more complicated, but still isnt impossible. Use published data-low altitude en route charts are great for this-to choose a cruising altitude and electronic tools to ensure accurate navigation.

Most important, though, is what happens when inadvertently flying into a cloud, when uneven terrain presents a false horizon or when your view of the natural horizon is blocked. This is when transitioning to instruments can be critical-even for performing the proverbial 180-degree turn-and you need the training and experience to master it.

LEAVE A REPLY

Please enter your comment!
Please enter your name here