Perhaps because of its various attractions, night flying presents its own set of challenges. Let the sun go down, and all kinds of aviation-related mischief can ensue. The basic problem, of course, is humans are not well-adapted to seeing and doing complex things in low-visibility conditions. So, we have to compensate.
Because of the human eye’s limitations, the FAA and other authorities include several recommendations designed to minimize their impact. For example, and according to the American Optometric Association, “At night, if runway lights viewed from an approaching aircraft are displaced laterally, the pilot may have the impression that the runway is closer than it really is, because it appears wider. This false perception may result in an early flare and a tendency to land short. Also, the intensity of runway lights may appear to vary, depending on their color and the adaptation states of the eyes. These differences in the brightness of runway lights may lead to false perceptions regarding altitude.”
While we don’t know if the pilot in this month’s accident experienced any of these problems, the flight’s outcome strongly argues that he did, and that we should learn some lessons.
Background
On October 16, 2011, at 2010 Eastern time, a Cirrus Design Corp. SR22 was substantially damaged when it impacted a hazard beacon tower during approach to the Danbury (Conn.) Municipal Airport (DXR). The solo private pilot was fatally injured. Night visual conditions prevailed; an IFR flight plan was in effect. The flight originated from Easton, Md., at about 1845.
At 1944, the airplane was at 5000 feet msl; at 2000, the pilot was provided the current altimeter setting and cleared direct to DXR. Three minutes later, the pilot advised ATC he had DXR in sight and was cleared for a visual approach. After switching to the control tower, the pilot was instructed to report a midfield right downwind for Runway 26. At 2007, ATC cleared the flight to land, which the pilot acknowledged. No further communication was received from the accident airplane.
At 2009, the airplane turned onto a base leg for runway 26. A minute later, while on final approach, the airplane struck an approximately 100-foot-tall hazard beacon tower. The airplane subsequently impacted trees and came to rest inverted against a residence.
A witness, who was walking his dog at the time, subsequently confirmed that the beacon lights were operating when the airplane struck the tower. The runway was equipped with medium intensity runway lights and runway end identifier lights, but not a visual approach slope indicator.
Investigation
Radar data revealed the airplane flew a 45-degree entry to the right downwind leg of the traffic pattern at 2008. The hazard beacon tower was located in a residential area, about ¾ mile from the runway threshold. The top of the tower was 750 feet msl, or 292 feet above the airport elevation of 458 feet msl. The purpose of the hazard beacon was to alert pilots of the higher terrain hazard prior to the runway: a residential neighborhood was located on a hill along the approach to the runway.
An approximately 400-foot-long debris path extended on a 260-degree magnetic course, from the hazard beacon tower to the main wreckage. All major aircraft components were located, except for one propeller blade. The fuel selector was positioned to the right main fuel tank. The flap actuator jackshaft was found in the full-flap-extension position. Elevator and rudder cable control continuity was confirmed from the flight controls to their respective bellcrank at the rear of the airplane. Aileron control cable continuity was confirmed from the center console pulley to the left and right wing pulleys, respectively.
Fuel was recovered from the engine driven fuel pump. It was clear and consistent in odor and color with 100LL avgas. When the propeller hub was rotated by hand, camshaft and crankshaft continuity was confirmed. Thumb compression was attained on all cylinders. The magnetos were removed from the engine and produced spark to all top leads when rotated by hand.
The airplane’s remote data module (RDM) was retained and forwarded to NTSB labs for data recovery. A GPS plot was generated from the RDM data and revealed the airplane turned on to the final approach leg at 2010:15, at a GPS altitude of 1211 feet. At 2010:40, the data indicated the airplane was at a GPS altitude of 747 feet, and groundspeed of 75 knots, when it struck the tower. Additionally, review of the engine and control parameters contained in the RDM data did not reveal any pre-impact mechanical malfunctions with the airplane.
Weather observed at DXR, at 2022, included wind from 200 degrees at eight knots, visibility 10 miles, scattered clouds at 9000 feet and an overcast ceiling at 11,000 feet. Review of information obtained from Lockheed Martin and direct user access terminal service (DUATS) providers revealed the pilot did not obtain a weather briefing for the accident flight. However, he did file an IFR flight plan with DUATS.
The accident airplane’s avionics system was equipped with a terrain awareness and warning system (TAWS) B and synthetic vision system (SVS) software option, which were enabled. The version of software installed on the accident airplane did not record TAWS B or SVS warnings, however, and the obstacle database used by both TAWS B and SVS did not include towers less than 200 feet agl. The TAWS B would have, by design, provided a routine aural alert when the airplane descended below 500 feet in an airport environment. Additionally, the terrain database used by SVS was of sufficient resolution to depict the hill at the base of the tower on the primary flight display.
Probable Cause
The NTSB determined the probable cause(s) of this accident to include: “The pilot did not maintain clearance from a lighted tower during final approach in night visual conditions.” That’s about as short and sweet as NTSB probable-cause findings get, but doesn’t tell the full story. For some details on the kinds of tricks night flying can play, see the sidebar on the opposite page.
It’s easy to sit back and say, “I wouldn’t do that; I’d stay high until the runway was made and my night vision is good enough to perceive the relative position—and purpose for—the beacon the accident pilot hit.” But many pilots no longer with us have said much the same thing at one time or another.
