Figure: Accident airplane's descent profile, from NTSB AAR 06/01, figure 6.
In 1995, following a nearly catastrophic short landing off a VOR approach, American Airlines had to remind its pilots that "despite its name a non-precision approach must be executed with exacting precision." More about this: "Mishap / American Airlines 1572. We had been computing our own Visual Descent Points (VDPs) in the Air Force for over ten years at that point, but after the 1995 crash more and more operators adopted the VDP technique. More about this: Flight Lessons / Visual Descent Point (VDP).
Nearly ten years after the American Airlines crash and twenty years after the VDP technique became publicized, this commuter operator killed nearly everyone onboard when the pilots displayed less than exacting precision and fell into a very easy trap set by all "non-precision" approaches in low visibility conditions. It is difficult to judge one's distance to the runway and without the requisite precision we are tempted to descend early. This crew impacted the earth 1.2 nautical miles short of the runway.
This aircraft was technology poor, but they had what they needed to compute a visual descent point and the techniques to do so were well known at the time. The crew's joking banter prior to the instrument approach may appear harmless, but it sets
the wrong tone for the serious work ahead of them. Finally, the first officer missed several opportunities to call for a go around when he lost sight of the runway below the minimum descent altitude. One of the ironies of this mishap is that 28 minutes before their deaths, both pilots were talking about hating pilots who "take themselves too serious." In the end, they didn't take what they were doing seriously enough; a more serious application of call outs would have saved them. See "CVR extract," below.
There is absolutely no need to "dive and drive" on these non-precision approaches and even if you are flying an aircraft with the bare minimum in avionics, you can and should fly a continuous descent final approach. More about this: Normal Procedures & Techniques / Continuous Descent Final Approach.
What follows are quotes from the relevant regulatory documents, listed below, as well as my comments in blue.
- Date: October 19, 2004
- Time: 19:37
- Type: British Aerospace 3201 Jetstream 32EP
- Operator: Corporate Airlines
- Registration: N875JX
- Fatalities: 2 of 2 crew, 13 of 15 passengers
- Aircraft Fate: Destroyed
- Phase: Approach
- Airports: (Departure) Saint Louis-Lambert International Airport, MO (STL / KSTL), United States; (Destination) Kirksville Regional Airport, MO (IRK / KIRK>, United States
Figure: KIRK LOC DME Rwy 36, from NTSB AAR 06/01, figure 4.
[NTSB AAR 06/01, page viii.] On October 19, 2004, about 1937 central daylight time, Corporate Airlines (doing business as American Connection) flight 5966, a BAE Systems BAE-J3201, N875JX, struck trees on final approach and crashed short of runway 36 at the Kirksville Regional Airport (IRK), Kirksville, Missouri. The flight was operating under the provisions of 14 Code of Federal Regulations Part 121 as a scheduled passenger flight from Lambert-St. Louis International Airport, in St. Louis, Missouri, to IRK. The captain, first officer, and 11 of the 13 passengers were fatally injured, and 2 passengers received serious injuries. The airplane was destroyed by impact and a postimpact fire. Night instrument meteorological conditions (IMC) prevailed at the time of the accident, and the flight operated on an instrument flight rules flight plan.
We'll take up with the accident report as the aircraft begins their approach to take specific notice of the demeanor of the pilots as they begin an instrument approach into fairly marginal conditions. The less than professional nature of the captain's chatter sets the tone that later ends with both pilots failing to fly the procedure correctly. The type of procedure is often called a "non-precision approach" because it lacks precise vertical guidance. It does, however, demand precision flying. More about this: Normal Procedures / Continuous Descent Final Approach.
[NTSB AAR 06/01, page 3.]
- As the airplane began to descend into the top of the clouds, the CVR recorded the captain stating, "...we're going into the crap. Look, ooh, it's so eerie and creepy...get a suffocating feeling when I see that." The first officer made a barking sound followed by a groan, and, about 1925:13, the captain continued, stating, "I'm drowning...," then he remarked, "MSA is thirty one hundred." The first officer responded, "correcto mundo." About 25 seconds later, CVR recorded a yawn on the first officer's channel, then he stated, "they have a VASI [visual approach slope indicator] on the left hand side," and the captain responded, "yeah. Wish we had an ILS on the front side." The first officer said, "yeah, that'd be nice."
- When the airplane was about 10 minutes from its destination, the ARTCC controller advised the pilots to turn 10° to the right to intercept the localizer for runway 36 at IRK. The pilots complied, turning to a heading of 310.° About 2 minutes later, the captain asked, "how's...Kirksville looking weather wise? Getting any worse?" The pilots again listened to the IRK ASOS weather information, which indicated a wind from 030° at 6 knots, visibility 3 miles in mist, ceiling overcast at 300 feet agl, temperature and dew point 9° C, and an altimeter setting of 29.95 inches Hg. The captain stated, "temp [and] dew point's right where you don't want it," and the first officer responded, "yeah...still three hundred."
- The pilots performed the approach checklist as the airplane descended and leveled off at 3,100 feet msl. About 1930:35, the ARTCC controller told the pilots they were 11 miles south of the final approach fix (FAF) for the localizer DME approach to runway 36 at IRK. He advised them to turn right to a heading of 330° and maintain an altitude of 3,000 feet msl until they were established on the localizer, then cleared them for the localizer DME approach to runway 36 at IRK. The pilots complied and the first officer advised the captain that the localizer course was "alive." The captain stated, "Let's go flaps ten and we'll configure early...give ourselves as much time as we can." The first officer agreed and selected and verified 10° of flaps as the airplane intercepted the final approach course.
- Less than 1 minute later, the captain confirmed with the first officer that they could descend to 2,500 feet msl at that point in the approach, then asked the first officer to extend the landing gear, select 20° of flaps, and perform the before landing checklist. About 1932:48, the first officer stated, "gear down...flaps selected indicating twenty" and continued the before landing checklist. About 1933:40, the ARTCC controller approved a frequency change (to the IRK common traffic advisory frequency [CTAF]) and advised the pilots to report after they landed. The first officer acknowledged the instructions and, at the captain's request, keyed the microphone to activate the pilot-controlled runway lights at IRK.
- According to FDR, CVR, and radar data, the airplane was at 2,500 feet msl when it crossed the FAF at 19:35:36, and the first officer advised the captain that they could descend to 1,320 feet msl, the MDA for the approach. The captain acknowledged, stating, "thirteen twenty, here we go." Radar and calculated FDR data indicated that the airplane then began to descend about 1,200 feet per minute (fpm) while tracking the localizer. About 1936:23, as the airplane descended through about 1,600 feet msl, the first officer stated, "five hundred, four hundred to go." About 17 seconds later (at 1936:30.6), as the airplane descended through about 1,450 feet msl (about 500 feet agl), the CVR recorded the airplane's ground proximity warning system's (GPWS) mechanical announcement, "five hundred."
While 3.41° makes for a steeper than normal glide path, it would not have required more than 700 fpm to descend precisely from the final approach fix to the runway. Under "dive and drive" techniques, however, most pilots are predisposed to descend more quickly to maximize their chances of seeing the runway. This technique works, except pilots must display a great deal of skill and discipline to level the aircraft at the MDA and keep it there until the runway is in sight and the airplane is on a normal glide path.
- At 1936:33.9, as the airplane descended through about 1,380 feet msl, the first officer stated "thirteen twenty." The captain thanked him and about 3 seconds later (as the airplane reached the MDA), stated, "I can see ground there." As he finished speaking, the GPWS annunciated, "minimums, minimums," indicating that the airplane had reached 1,320 feet msl. Calculated FDR data indicated that the airplane continued to descend at a rate of about 1,200 fpm. At 1936:40.5, the captain asked, "what do you think?," and the first officer responded, "I can't see [expletive]." About 2 seconds later, as the airplane continued to descend, the captain stated, "yeah, oh there it is. Approach lights in sight." Almost immediately, the GPWS annunciated "two hundred" feet agl and the first officer stated, "...in sight...continue." The airplane was descending through about 1,160 feet msl (160 feet below the MDA) at this time.
The correct call after the captain asked "what do you think?" while below the MDA without the runway in sight is "Go around."
- As the pilots continued the approach, still descending about 1,200 fpm, the first officer asked the captain if he wanted the flaps extended to 35.° At 1936:52.2, the captain responded, "no," and the GPWS began to announce, "sink rate."20 One second later, the first officer exclaimed, "trees," and the captain stated, "no, stop." The first sounds of impact with the trees were recorded at 1936:55.2, and numerous sounds of impact were recorded before the CVR stopped recording at 1936:57.5.
Some pilots bristle at the idea of standardized call outs and hate flying with pilots who fly "by the book." One of the ironies of this mishap is it could have been prevented by a more disciplined approach to call outs. Here is an extract of the Cockpit Voice Recorder that sums up this pilot team's attitude. HOT-1 is the captain, HOT-2 is the first officer.
- 1909:30 HOT-1 gotta have fun.
- 1909:31 HOT-2 that's truth man. gotta have the fun.
- 1909:35 HOT-1 too many of these # take themselves way too serious, in this job. I hate it, I've flown with them and it sucks. a month of # agony.
- 1909:47 HOT-1 all you wanna do is strangle the ## when you get on the ground.
- 1909:50 HOT-2 oh'.,.. @ [sound of laughter]
- 1909:52 HOT-1 oh *, yeah, oh well, he was one but I didn't, I didn't have to fly with him that much 'cause....
- 1909:56 HOT-2 I know.
- 1909:57 HOT-1 it was kinda a fluke. but uh, some of the guys that aren't here any more you wanted to just # kick 'em in the #. lighten the # up #.
[NTSB AAR 06/01, page viii.]
- The National Transportation Safety Board determines that the probable cause of the accident was the pilots' failure to follow established procedures and properly conduct a non-precision instrument approach at night in IMC, including their descent below the MDA before required visual cues were available (which continued un-moderated until the airplane struck the trees) and their failure to adhere to the established division of duties between the flying and non-flying (monitoring) pilot.
- Contributing to the accident were the pilots' failure to make standard callouts and the current Federal Aviation Regulations that allow pilots to descend below the MDA into a region in which safe obstacle clearance is not assured based upon seeing only the airport approach lights. The pilots' failure to establish and maintain a professional demeanor during the flight and their fatigue likely contributed to their degraded performance. "
NTSB Aircraft Accident Report, AAR-06/01, Collision with Trees and Crash Short of the Runway, Corporate Airlines Flight 5966, BAE Systems BAE-J3201, N875JX, Kirksville, Missouri, October 19, 2004