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Probable Cause #31: Test Pilot

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This article originally appeared in IFR Refresher, Mar. 2006.

Probable Cause

Sometimes as the day grows longer we may become impatient to get home. If we are in an automobile and forget to close a door or discover a fault related to maintenance that was just completed, we can pull over and fix the problem or return to the shop that did the maintenance.

The pilot of a 1980 Cessna Citation I/SP that had just come out of maintenance discovered some kind of problem with his airplane immediately after becoming airborne. Unfortunately, he didn't have the option of stopping alongside the road. Instead, he crashed into a building while trying to return to the airport. While the problem that forced the pilot to return to the airport was never discovered, the accident shows that flying should never be rushed, especially when the weather is bad and the airplane has just come out of an intensive inspection.

Dinner Is Waiting

Cessna Citation I/SP

The story begins in Key West, Fla., on an April morning in 2001. The pilot and his wife had flown from Key West to Southwest Florida International Airport (KRSW) in Fort Myers, Fla., where the pilot took a commercial flight to Green Bay, Wisc. There, the 54-year-old pilot was to pick up a Citation that had just come out of the shop for an inspection and some repairs and fly it back to Fort Myers that evening in time for a late supper with his wife. (The Citation I/SP can be certified for single-pilot operations).

The receptionist at the repair station where the pilot was to pick up the Citation estimated that the pilot arrived sometime between 4:00 and 4:10 p.m. local time. She said he immediately went to the back rooms where the vending machines and flight planning room was located. He came back to the lobby in a few minutes with a soft drink and snack. Noticing the pilot's hands were full and ever so courteous, the receptionist opened the door to the hangar for him. "That's your dinner?" She asked. The pilot replied, "No. My dinner's in Fort Myers." The receptionist estimated that the pilot's total time in the lobby area was two to five minutes.

A line worker for the FBO said the pilot was scheduled to arrive to pick up the airplane at 4 p.m. but was running late, apparently because his commercial flight did not arrive on time. One reason for the delay could have been the weather at Green Bay's Austin Straubel International Airport (KGRB), with low ceilings and poor visibility caused by snow and fog. The line worker said he saw the pilot inside the hangar talking to the mechanic who had supervised the inspection and repair of the aircraft while performing a walk-around inspection of the airplane.

The airplane was already hooked up to a tug and was ready to be pulled out of the hangar. When the pilot finished walking around the airplane he climbed in and the line worker tugged the airplane out of the hangar. He said it was snowing at the time with "big, wet flakes." He estimated that pulling the airplane out of the hangar and unhooking his tractor took two minutes. Then, he said, it was less than five minutes from the time he unhooked the tow bar until the airplane was taxiing.

Turning Back

Green Bay's (Wisc.) Austin Straubel International Airport (KGRB)

FAA tower records show that the pilot called for his clearance at 4:15 p.m. -- probably while the airplane was being towed out of the hangar -- and called for his taxi clearance at 4:23 p.m. He taxied to Runway 18 and at 4:26 p.m. the tower cleared the Citation for takeoff with instructions to proceed on course.

Less than two minutes after issuing the takeoff clearance, and with the Citation just airborne, the tower controller told the Citation pilot to contact departure control. But instead of acknowledging the hand-off, the pilot said, "We have a little problem here. We're going to have to come back."

The tower controller replied, "Roger, and what approach would you like?" The pilot responded, "We'd like to keep the vis."

Not sure what the pilot meant, the controller asked, "Like the contact approach? [Is] that what you're saying?" There was no response and repeated attempts to contact the airplane were unsuccessful.

The Citation crashed into a building at a dairy processor just southeast of the runway, destroying the building and damaging another. The pilot, who was the only one onboard the aircraft, was instantly killed, while seven workers on the ground were injured, including three with serious burns.

Several witnesses on the ground told the NTSB investigator that they saw the plane approaching the dairy processor from the south, low to the ground and in an increasingly steeper left bank. According to their accounts, the wings were nearly perpendicular to the ground when the Citation slammed into the building. The witnesses reported a loud explosion followed immediately by flames and heavy black smoke.

The aircraft was privately owned and operated by another individual. (The NTSB report does not explain the relationship between the aircraft's owner and the accident pilot.) The owner told investigators that he had delivered the airplane to Green Bay from Springfield, Ill., about a month earlier so that Phases 1 through 4 inspections and some maintenance could be performed.

A mechanic told investigators that they corrected several discrepancies that had been identified to them by the aircraft owner. One involved the autopilot, which would porpoise the airplane when it was placed in altitude hold mode. The autopilot pitch drive, vertical gyro and autopilot computer were removed and sent to an avionics shop in Lincoln, Neb., where they discovered that the vertical gyro rotor was failing. The vertical gyro is an integral component of the attitude director indicator (ADI), an advanced attitude indicator that displays command signals from a flight-director computer. The gyro was repaired and recalibrated before being sent back to Green Bay. There, the repair shop reinstalled the parts in the airplane and checked the autopilot system twice, each check showing that the autopilot functioned normally.

The pilot held an Airline Transport Pilot certificate for multiengine land airplanes, as well as a Cessna 500 type rating. He also held commercial privileges for single-engine land and sea airplanes. His logbook revealed that he had 4,547 total flying hours, 3,567 hours as pilot in command, and 244 hours in the Citation 501. He took a Cessna 550 simulator checkride in April 2000 and had completed Cessna 650 recurrency training in February of 2001.

The weather at the time of the accident was far from perfect. At 3:56 p.m., KGRB reported ceilings of 600 feet broken, 1,200 feet overcast with 3/4-mile visibility in light snow and mist. The temperature was 34░F, dew point 32░F and the winds were from 160 degrees at five kts.

At 4:38 p.m. -- nine minutes after the accident -- the weather was reported as a broken ceiling at 200 feet, 800 feet overcast and 1/2-mile visibility in snow and fog. The temperature was now 32░F, as was the dew point. The winds were from 120 degrees at three kts.

Mystery Problem

Cessna Citation Panel

So, what was the "little problem" the pilot reported he had?

The NTSB was never able to determine that because the impact and the fire that followed destroyed much of the airplane. The pilot's instrument panel was found fragmented, charred and melted and investigators found little useful information from its components. The co-pilot's attitude indicator was examined by NTSB personnel in Chicago, and while the instrument was badly damaged, scoring marks on the inside of the case and the front of the gyro indicate that it was operating at the time of the accident.

The engines were sent to their manufacturer for examination and no faults were found. The main cabin door was broken, fragmented and charred, but the handle was found in the closed and locked position.

Lacking any physical cues that could have contributed to the accident, the NTSB determined its cause was the pilot's failure to maintain control of the aircraft while maneuvering after takeoff, and his inadequate preflight planning and preparation. Other factors included the pilot's diverted attention while maneuvering after takeoff and his attempt to fly the aircraft under VFR in IMC conditions. The NTSB stated that visual lookout was not possible due to the low ceiling, snow and fog. It's a determination that does not address the problem that began the accident sequence. This is through no fault of the NTSB; from the condition of the aircraft remains and without a flight data or cockpit voice recorder, there was little accident investigators could use to determine the source of this "little problem."

As is the case in many general aviation accidents where hard evidence is lacking, we are left to speculate about what might have happened that so distracted the pilot that he lost control of the aircraft. First, let's look at the time line.

The aircraft was cleared for takeoff at 4:26:52 p.m. At 4:28:17 p.m. the controller instructed the pilot to switch over to the departure control frequency. Four seconds later the pilot stated that he had a problem and wanted to come back. The crash occurred at 4:29 p.m. or slightly more than two minutes from the time it was cleared onto the runway. Whatever occurred was likely to be a problem that existed before takeoff and may have escaped notice during a ground check.

The first thing that comes to mind is the ADI that had just been repaired. The mechanic who installed the unit stated that he checked the system twice and that it functioned properly, but that was on the ground when the airplane was stationary. It's possible that this masked another problem that would only become evident when the airplane was in flight.

Immediately after takeoff in a turbine aircraft is a busy period for a pilot. The gear is coming up, the flaps are coming up, the aircraft's speed is increasing rapidly and the power is being pulled back to keep the speed below 200 or 250 kts and to make the initial level-off, in this case 3,000 feet, which comes up quickly. This is a critical time, especially when conditions are IMC, and anything not directly related to flying the aircraft becomes a distraction.

Assuming an ADI failure, problems could manifest themselves in different ways. Perhaps the whole ADI, including the attitude indicator, failed. Or maybe the command bars were displaying wrong or contradictory information, either as a result of a mechanical failure or because of an error in setting up the flight-guidance controller. This can be difficult to determine in an already task-saturated environment.

There are two other things to consider relative to the ADI. If that instrument had failed, wouldn't the pilot have declared an emergency rather than telling the controller that he had a "little problem?" Or was this the blasÚ reaction that often comes with experience? Still, his decision to attempt to return to the airport visually when the weather was clearly not suitable for it indicates that there was something more than a little problem. Unfortunately, we'll never know what the real issue was.

Summary

So, where does that leave us in our quest to insure that this type of accident does not happen again? First, you cannot practice partial-panel flying enough, even if you have a second panel in the aircraft. That is a vital skill, even in this day of EFIS. Of course, most EFIS-equipped aircraft have standard instruments for backup, but like partial-panel flying, those spare instruments are not what the pilot is used to using. Their location and configuration may require constant practice to insure a satisfactory scan rate.

The Citation accident is classic in that it points out the need to always fly the aircraft first, no matter what else is going on around you. The emergency, no matter what it is, will require your attention, but if you don't fly the airplane, especially when you are close to the ground, there is little need to deal with it.

Since we don't know what occurred on the Citation that day, we don't know how much the pilot's hurry to get home contributed to it. If the failure of the ADI was imminent, would he have noticed it before takeoff? Perhaps he did check it and found it to be functioning properly. Perhaps in his walk-around he did check all the external features that could have caused a problem right after takeoff.

However, another thing to take out of this accident is that you should never be pressured into flying an airplane right after maintenance is completed without a thorough preflight. Allow yourself plenty of time to do it right. Try to get to the shop early in the day instead of late in the day, with time built-in so that any defects that are discovered can be taken care of before you fly.

If the maintenance was invasive, fly the aircraft in VFR conditions first to make sure all of its equipment is operating properly. Any equipment failure is much easier to handle when you can fly the aircraft visually and when the airport is nearby.


More accident analyses are available in AVweb's Probable Cause Index. And for monthly articles about IFR flying including accident reports like this one, subscribe to AVweb's sister publication, IFR Refresher.

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