Risk Factors Of Using Unpaved Runways, Part 3

Rocks and other hard objects are more problematic for aircraft with higher takeoff and landing speeds as high-velocity projectiles can abrade brake lines, puncture flaps, or interfere with flight controls. I learned that lesson while providing logistical support to Central Alaska communities with unpaved runways.  

During takeoff from one of these unpaved runways, I tried to pull back on the yoke of a Short Brothers C-23 Sherpa, but the yoke was stuck solid. It wouldn’t budge. I followed quickly with a heftier pull on the yoke, but to no avail. By now the end of the runway was getting closer by the micro-second. I slammed the power levers rearward, stomped on the anti-skid brakes, and pulled on the reserve power levers.  

“Braking effectiveness” on an unpaved runway isn’t quite an oxymoron but it felt that way. Fortunately, we had the deceleration force supplied by two large turboprop propellers. We narrowly avoided going off the end of the unpaved runway, which at this location would have resulted in rolling down a steep hill into the Yukon River.  

The post-incident response team discovered that a rock kicked up by the main gear had become lodged between the elevator and the horizontal stabilizer, preventing any movement of the elevator. The incident review team concluded that the accelerate-stop performance determined during flight testing simply did not replicate the wide variety of variables that existed on this unpaved airstrip.  

Decades of simulator training for takeoff aborts didn’t fully prepare me for this incident. I had never encountered locked-up flight controls. This occurred past our V1 speed, so I was already in the “go” mode. All of the high-speed aborts performed in the simulator had been close to V1 on a runway that allowed for sufficient deceleration and directional control. That was not the surface condition experienced during this incident. Every irregularity in the surface of that unpaved runway caused a corresponding jolt in the motion of the aircraft. It was difficult trying to keep directional control in addition to getting maximum deceleration.  

This was not the only damage that impacted our flight operations during the deployment to Alaska. High-speed debris had damaged important aircraft components on the bottom of the aircraft to include lights and antennas. The damage to the antennas had negatively affected the aircraft’s communications and navigation systems. That was problematic when attempting to fly IFR in the notoriously challenging weather and terrain in Alaska.  

The maintenance supervisor was aghast at the amount of damage to the underside of the aircraft when we brought it back to its home base after a series of logistical support flights. The aircraft was out of service for a long time due to these extensive repairs.

No Place For Malfunctions
If your aircraft develops a noise that you don’t like at remote locations, you aren’t able to stride over to the local mechanic’s hangar and ask him to take a look. If you need an extra quart of oil, you can’t simply ask the lineman to bring you an extra quart. Or suppose you accidentally forget to turn off the master switch and the battery gets run down? Where are you going to recharge a dead battery in these destinations? This isn’t the place for a mechanical malfunction.

Repairing damage on a turbine aircraft isn’t as simple as pulling out gorilla tape to mask up puncture in the flap. The repair will require expert servicing from technicians with knowledge of the aircraft’s maintenance manual. Spare parts will be needed to be shipped to the remote location. Aircraft jack stands may be needed. This can require an extraordinary effort, meaning time and expense.  

For example, a Sherpa experienced substantial damage to an engine mounting while taxiing on the unpaved airstrip at Rampart, Alaska. The damage required grounding the aircraft until it could be properly repaired. The replacement parts were heavy and could only be shipped to this location via barge.  

First the spare parts had to be transported into Fairbanks, then placed on a barge that flowed down the Tanana River to its junction with the Yukon River, then upriver to the remote airstrip. The aircraft was out of service for months waiting for the replacement parts.  

Furthermore, this location had no hangar, so the aircraft was exposed to the elements, which included wildlife that could seriously damage the twin-engine turboprop. The C-23 had to be guarded 24/7 by deputized firefighters armed with lethal weapons because of grizzly bears.  

The important point to be learned from this example is the additional consideration for the logistical support necessary if an aircraft needs maintenance at a remote location. Extensive down time and expense will be incurred. This should be taken into account as part of the cost versus benefit when operating in these unpaved locations.

Risk Assessment Checklist

The Flight Safety Foundation’s Approach and Landing Accident Reduction Toolkit has a risk assessment checklist to help pilots using a normal (i.e., paved) runway surface. Needless to say, the lack of Visual Approach Slope Indicator lights and lack of weather and landing surface information at an unpaved airstrip are among the many hazards that increase the number of risk factors. Before considering an adventure into this environment an operator should check their insurance policy as most policies consider unpaved runways to be excessive risk.

The Smiley Creek Recommended Standard Operating Procedures pamphlet contains the following advice: “Do not attempt operations at Smiley Creek without having a solid fundamental background in mountain flying. The Idaho Division of Aeronautics strongly recommends that visiting pilots obtain an airport checkout before landing at Smiley Creek Airport.” This advice is universally reiterated by the respected backcountry operators and specialized flight schools in the region.

The state of Idaho further recommends that pilots venturing into these challenging environments possess rock-solid skills in slow flight, airspeed control, intimate knowledge of aircraft performance and well-prescribed personal limitations. That especially includes the proper attitude—one that is safe, conservative and professional.

Risk Factors Of Using Unpaved Runways, Part 1: https://aviationweek.com/business-aviation/safety-ops-regulation/risk-f…

Risk Factors Of Using Unpaved Runways, Part 2: https://aviationweek.com/business-aviation/safety-ops-regulation/risk-f…