The National Transportation Safety Board has released the following update of its investigation of the midair collision between a Piper PA-31T twin-engine Cheyenne (N360LL) and a single-engine Cessna 172 (N52241) on January 24, 2003, over northwest Denver, Colorado. Both aircraft were destroyed by impact forces and fire. Five people were killed in the crash.

Airplane Wreckage

The wreckage from both airplanes has been collected and secured at an aircraft salvage facility in Greeley, Colorado.  Today, the wreckage is being carefully laid out and examined by investigators from the NTSB with assistance from the Federal Aviation Administration (FAA), New Piper Aircraft Company, and Cessna Aircraft Company. The wreckage will be examined in an effort to document paint transfer marks, scratch marks, and structural damage, to assist in determining the collision angles between the two airplanes. This activity will continue over the next 2 days. Maintenance records for each airplane are also being secured and will be examined.

Air Traffic Control Issues

As a routine part of any investigation involving a midair collision in or near controlled airspace, the NTSB formed an Air Traffic Control (ATC) group. The group chairman is an ATC specialist from NTSB Headquarters in Washington, D.C. who arrived in Denver on Sunday. The ATC group consists of representatives from the FAA in Washington, D.C., and local representatives
from the National Air Traffic Controllers Association. Yesterday, the group visited the Denver ATC Approach Control facility in Denver, Colorado, and received an initial briefing regarding the facility. The group also viewed the radar playback, listened to recorded ATC voice communications, and downloaded recorded radar data for further analysis. The following information has been obtained thus far from the ATC group:

The pilots were not required, according to FAA regulations, to contact ATC; however, both pilots requested and received a service known as visual flight rules (VFR) flight following. As a result, one controller was providing basic radar services to both pilots which include safety alerts, traffic advisories and limited radar vectoring when requested by the pilot. The group will be interviewing ATC controllers today [Monday], and will continue to analyze the radar data and voice recordings.

Sequence of Events

The following sequence of events is according to preliminary information.

About 5:00 p.m. CST, the Cessna 172 departed from Centennial Airport enroute to Cheyenne, Wyoming. About 5:10 p.m., the Piper Cheyenne departed Jefferson County Airport enroute to Centennial Airport. At 5:17 p.m., the Piper Cheyenne pilot reported to the Denver Approach controller. When asked, the Piper Cheyenne pilot reported that his altitude was 7,800 feet.
About 90 seconds later, the Cessna 172 pilot contacted the controller. The Cessna was at 7,300 feet and requested to climb to 8,500 feet. The request was granted. 

About ten seconds later, the controller asked the Piper Cheyenne pilot his altitude. The Piper Cheyenne pilot indicated that he was flying at 7,600 feet. The controller then issued a traffic advisory to the Piper Cheyenne pilot advising that there was a Cessna at the Piper Cheyenne's twelve o'clock position and 1 mile at 7,700 feet. The collision occurred shortly
thereafter.

Weather and Lighting Environment

The reported weather conditions about the time of the accident allowed for flights to be conducted under VFR. The reported visibility was about 10-15 miles and the cloud conditions were reported as broken and scattered from 6,000 feet to 14,000 feet mean sea level. Additionally, the sun had set about 20 minutes prior to the collision. Safety Board investigators will
continue to investigate the effects that lighting may have had on the pilots' ability to see other aircraft.

FMI: www.ntsb.gov