This week's Accident of the Week dramatically illustrates that concept, especially when flying an approach into conditions at minimums.
According to the approach plate for the ILS 19 at ACT, the DH for the straight-in ILS 19 is 705 feet. The TDZE is 505 feet. So this is a standard 200 foot minimums approach, and one minute after clearing the pilot for the approach, that is what the tower controller advised were the prevailing weather conditions.
NTSB Identification: DFW07FA036
14 CFR Part 91: General Aviation
Accident occurred Sunday, December 10, 2006 in Waco, TX
Aircraft: Cessna 310Q, registration: N69677
Injuries: 3 Fatal.
This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed.
On December 10, 2006, about 1859 central standard time, a twin-engine Cessna 310Q airplane, N69677, was destroyed when it collided with terrain while executing an instrument approach to the Waco Regional Airport, near Waco, Texas. The commercial pilot and the two passengers were fatally injured. The airplane was registered to a private company and operated by the pilot. An instrument flight rules (IFR) flight plan was filed for the flight that originated at the Harry Anders/Natchez Adams County Airport, near Natchez, Mississippi, about 1700. Night instrument meteorological conditions prevailed for the business flight conducted under 14 Code of Federal Regulations Part 91.
Prior to departure, the pilot obtained weather information and filed an IFR flight plan with the Anniston Automated Flight Service Station (AFSS), near Anniston, Alabama.
A preliminary review of air traffic control (ATC) communications revealed that the pilot was cleared to fly direct from the Natchez Airport to the Waco Regional Airport. As the pilot approached the Waco Terminal Radar Approach Control (TRACON) area, he received vectors to intercept the localizer course for the instrument landing system (ILS) RWY 19 approach at Waco Regional Airport.
At 1848, an approach controller provided the pilot weather information obtained from another pilot who had just executed the ILS RWY 19 approach and landed without incident. She reported "breaking out" of the overcast layer at an altitude of about 800 feet, approximately one-mile north of Runway 19. The pilot acknowledged the information and responded "that sounds good [N69]677."
At 1854, an approach controller informed the pilot that his position was 7 miles north of the COFFI intersection (final approach fix) and that he was cleared for the ILS RWY 19 approach. The approach controller also instructed the pilot to turn to a heading of 220 degrees, and maintain an altitude of 2,000 feet until established on the localizer course. The pilot acknowledged the clearance and shortly after was cleared to contact the Waco Regional Airport Control Tower. The pilot contacted the control tower, and about a minute later, a tower controller cleared the pilot to land on Runway 19.
At 1856, a tower controller informed the pilot that the weather at the airport was "two-miles visibility with a 200 foot overcast ceiling and fog." The pilot acknowledged.
Approximately two minutes later, a tower controller alerted the pilot and said, "N677...low altitude alert...check altitude immediately." Shortly after, a tower controller reported seeing a "fireball" north of Runway 19.
A preliminary review of radar data revealed an IFR target approaching the Waco Regional Airport from the north. At 1854, when the target was about 7 miles north of the airport, it was at an altitude of 1,800 feet mean sea level (msl) at a ground speed of 76 knots. Approximately two minutes later, when the target crossed over the final approach fix, about 4.5-miles north of the airport, it was at an altitude of 2,100 feet msl at a ground speed of 78 knots.
At 1858, when the target was approximately 2.3 miles north of the airport, it was at an altitude of 900 feet msl and at a ground speed of 81 knots. At this point, the target momentarily ascended to 1,100 feet msl, and maintained a ground speed of 81 knots. Over the next 30 seconds, the target's altitude descended to 600 feet msl and the ground speed decelerated to 59 knots before the data ended.
A witness, who was driving on a road located north of the accident site, reported that he first observed the airplane out of the right side window of his vehicle. He reported that the "lights" of the airplane appeared "hazy," and were not as "bright" as he was used to seeing on other aircraft that flew into Waco Regional Airport. Shortly after he observed the airplane's lights, he observed an "explosion" behind a tree line that was located between him and the airplane. The witness immediately called 911 and drove to the site of the accident. He added that the Fire Department arrived within five minutes of the accident.
The witness also stated that the weather was a low overcast, fog, rain "sprinkles," and mist. He reported that the cloud layer was above the height of the trees and that the visibility was approximately .5- to 1-mile. In addition, the witness said it was "very dark outside."
Weather reported at the airport, at 1851, included winds from 140 degrees at 8 knots, temperature 50 degrees Fahrenheit, dewpoint 48 degrees Fahrenheit, and barometric pressure setting 30.15 inches of Mercury. The visibility was 2-statute miles, mist, and the ceiling was 200 feet overcast.
The airplane wreckage was examined at the site on December 11-12, 2006. All major components of the airplane were accounted for at the scene. The airplane came to rest upright in a plowed cornfield, on a heading of approximately 160 degrees, at a ground elevation of approximately 450 feet msl, about 1.5 miles north of Runway 19. A post-impact fire consumed most of the airplane. Several initial impact marks consistent with the shape and size of the airplane's wings, tip tanks and engines, were located underneath and several feet to the right of where the main wreckage came to rest. The main wreckage included both wings; tip tanks, engines, the fuselage, and the tail section.
The right engine cowling, right door, three seat frames, and a nose gear door were found forward of where the main wreckage came to rest.
The pilot held a commercial pilot certificate for airplane single-engine and multi-engine land, and instrument airplane. He also held a flight instructor certificate for airplane single-engine land and instrument airplane. In addition he held a private pilot certificate for gliders. His last second class Federal Aviation Administration (FAA) medical was issued on March 3, 2004. At the time of his last medical examination the pilot reported a total of 3,275 flight hours.
The report indicates that the crash occurred approximately 1.5 miles north of Runway 19. Here's a view of that area, as you'd see if you were flying inbound to the runway. (The white line ends at a point aproximately 1.5 miles from threshold of Runway 19.)
Unlike some airports, Waco isn't surrounded by terrain that poses a potential conflict in flying the approach. There also don't appear to be a huge amount of old-growth trees projecting hundreds of feet into the air and posing a hazard to aviators. And there also doesn't appear to be a forest of cell phone towers in the area.
And still we have an accident that, at least at first blush, appears to have been caused by flight below the DH. It remains to be seen if there was some mechanical defect that befell the flight at the last minute. It's possible that the descent below the DH could have resulted from an erroneous altimeter setting, but that's complete speculation at this point.
There's one last detail worth noting. According to this report, one of the passengers made a phone call "as the small plane he was flying in approached the Waco Regional Airport." Now, the regulations on instrument flight are explicit:
14 C.F.R. § 91.21: Portable Electronic DevicesNow, there's no question that a cell phone will NOT interfere with the operation of an altimeter. For those that need a refresher, the altimeter is a mechanical instrument that relies on static air pressure. Radio signals don't affect air pressure. So some pundits may cite this accident as an example of why the FCC and FAA should continue to ban the use of cell phones in flight. In response, to use a favorite legal term, we could say this accident is "inapposite." Let's hope people aren't fooled into believing that the person who may have made this call somehow was the caused of this mishap.
(a) Except as provided in paragraph (b) of this section, no person may operate, nor may any operator or pilot in command of an aircraft allow the operation of, any portable electronic device on any of the following U.S.-registered civil aircraft: (2) Any other aircraft while it is operated under IFR.