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How A Chain Of Failures Led To This Landing Accident

Many accidents result from a series of failures or errors that compound, each one worse than the previous. This is how an experienced, ATP rated pilot ended his flight with a hard landing and prop strike...

Flying After Maintenance

On January 8th, 2016, a 2,200 hour ATP rated pilot took off from Detroit Lakes, MN for a quick 40NM repositioning flight to Fargo, ND. According to the NTSB, "The pilot reported that this was the first flight after a phase maintenance check".

The plane, a Cessna 441 Conquest II, was made in 1980 and equipped with two Honeywell turboprop engines. It was certified to fly in IFR and icing conditions, both of which were prevalent on this cold winter day.

NTSB

Malfunctions Occur Early

On departure, the pilot climbed to 4,000 ft MSL and engaged the autopilot enroute to KFAR. He stated that he heard a "thumping" in the left rudder pedal, and noted a 20-degree left bank angle on the attitude indicator. After disengaging the autopilot, he rolled wings level, and started to troubleshoot the problem. Then, the left fuel pressure low light illuminated. Thinking it was an indication problem, he switched to the left AUX pump, then back to the main pump, which extinguished the light.

During this series of anomalies, ATC cleared the flight to descend to 2,800' MSL, but the pilot requested a climb to 5,000' MSL to get out of icing conditions and "sort out the problems."

matthewpiatt

Declaring An Emergency

During the climb, the pilot noticed a discontinuity message between the headings on the Avidyne Entegra flight displays. Once at 5,000' MSL, the pilot engaged the autopilot, and the airplane made a 180-degree turn to the right. The pilot disengaged the autopilot again and turned back towards KFAR. The left "fuel pressure low" light and the left "X-FER pump fail" then light illuminated. The pilot declared an emergency, and ATC cleared the flight to descend to 2,800 ft and provided vectors for the ILS Runway 36 approach to KFAR.

Worse yet, the pilot stated that as the airplane was descending through 4,000' MSL, the left engine started to surge. The pilot reported that the engine never failed during the flight, but he thought an engine failure was imminent, according to the NTSB.

Boldmethod

After flying through the localizer for the ILS Runway 36 approach, the pilot requested the GPS RNAV to Runway 32. The airplane broke out of the clouds about 600-700' AGL at 120 knots on the approach, less than a mile from the runway. The pilot lowered the landing gear in preparation for landing. However, ice had accumulated on the airplane during the approach, and the boots had not be recently cycled.

NTSB

The Hard Landing

The pilot reported that before he started the flare, he closed the throttle, selected the last notch of flaps, and flared at 110 knots. He stated there was shaking and shuddering, but no stall warning horn, and then the "bottom fell out." The airplane landed hard, and the left propeller blades struck the runway.

NTSB

The pilot conducted a post-accident examination of the airplane, stated that there was about 1/2 to 1-inch of rime ice accumulated on the leading edge surfaces of both wings. The examination of the airplane revealed there was substantial damage to the wing spar, and damage to the left propeller blades from the propeller strike. The stall warning horn was tested on the ground, and it operated.

So What Happened?

According to the NTSB, the pilot's failure to cycle the surface deice boots during the instrument approach in icing conditions led to ice accumulation on the leading edges of the wings and empennage. This resulted in an aerodynamic stall and subsequent hard landing at higher than normal airspeed (hence the stall horn not sounding).

Multiple Failures, Lots Of Distractions

With multiple in-flight failures, it's easy to see how the pilot was distracted, forgetting to use his de-ice boots on final approach.

This accident follows the classic error chain model, with one problem compounding on the next, eventually leading to the accident landing. Overall, the pilot did a good job dealing with multiple failures on the arrival into Fargo. Had he found a way to break the chain after flying through the localizer on the first approach, the hard landing may have never happened.

You can imagine how he felt, dealing with several problems in IMC, and then flying through the localizer on his first approach attempt. At that point, or maybe even earlier, had he given himself just a little more time, he might have broken the chain. Asking for wide vectors to set up for the GPS approach could have been a strategy to buy a few more minutes to make sure the airplane was ready for landing. But at the same time, the fuel indication problem was a real issue, and he most likely felt that the engine could fail at any time, making things worse.

It's easy to understand that he probably wanted nothing more than to be on the ground as soon as possible. But at that point, confirming the airplane was ready for descent and landing was critical.

Fortunately, ice buildup didn't cause a stall earlier on final approach. The pilot dealt with a lot of problems on a short flight, and got the airplane down on the runway. While the hard landing was unfortunate, the pilot walked away unharmed.

Swayne Martin

Swayne is an editor at Boldmethod, certified flight instructor, and commercial pilot for Mokulele Airlines. He holds multi-engine and instrument ratings, and is an aviation student at the University of North Dakota. He's the author of the articles, quizzes and lists you love to read every week. You can reach Swayne at swayne@boldmethod.com, and follow his flying adventures at http://www.swaynemartin.com.

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