Get The Drift On Excursions

Get The Drift On Excursions

  • July
  • 25
  • 2023
  • Advanced Aircrew Academy

A video of a snowplow accidentally ripping the nose gear off a Falcon 900 at Aspen (ASE) while attempting to tow it back onto a taxiway splashed around social media in April. The original runway excursion didn't cause damage, but the arduous task of getting the aircraft back onto the pavement caused more damage than the original mistake.

Although runway excursions continue to be the most frequent incident in business aviation, most don't meet the definition of an accident, so the NTSB doesn't investigate nor track the numbers. You can imagine that taxiway excursions are the most underreported incidents, but you can bet the insurance companies are keeping track and everyone gets to pay for them.

Numerous aircraft and airport signage / lighting systems are damaged each year by simply dragging a wheel off paved airport surfaces or beyond taxi line markings. Often unaware that a light or sign was hit, pilots leave the scene without reporting it and end up paying more than the price. According to §153.024, "Persons causing damage to runway and taxiway lights as a result of negligent operation of an aircraft or willful acts will be liable for replacement cost of the light(s) and/or fixture(s) and may be charged with a misdemeanor." Is your loss of situational awareness as you flip a switch a willful act?

According to Kim Skipper, aviation underwriting manager at Avemco, "Fortunately, bodily injury is rare in ground accidents but the continued escalation in the cost of property and equipment damage is harmful to the health of (general) aviation. And, of course, far and away, our biggest cause of claims during ground operations: excursion from the taxiway and resulting collision with taxiway sign/lights due to distraction/inattention. Contrary to what you would expect, the taxi mishap rate increases to 13% for pilots with more than 2,500 hours total time. Why? Most likely complacency. Experienced pilots may try to run checklists while they are taxiing, causing a division of attention that leads to a collision or taxiway excursion."

Lack of situational awareness, poor visibility, and ice/snow cover (including visual cues) are all contributing factors, but here's an angle you might not have thought of—airport and taxiway design. There are efforts to reduce this as a factor, but as with any change in aviation, it comes with caveats.

In 2017, the FAA issued an Advisory Circular (150/5300-13A/B) that updated the standards for Taxiway Fillet Design. Among the 322 pages are recommendations for taxiway operations and expanding the aprons to ease sharp turns. The construction of new rapid-exit taxiways is helping to increase average flight handling capacity from 32 movements per hour/runway to 44, but too often, pilots turn rapid exit taxiways into excessive speed taxiways.

You may not be aware, but those 30-degree exits off runways have a 60-knot limit, depending on the runway and aircraft type (most international airports), and a 35-knot limit for all other airports with high-speed exit taxiways. Unless you’re attempting a Tokyo Drift, don't attempt those speeds with a contaminated runway or taxiway or you'll join the growing number of costly excursions club. If you end up off the taxiway and were beyond 30 knots when you entered, that is considered a willful act, even though you didn't know there was a speed limit. Now you do.

Sharps angles are usually avoided in the aviation industry, but most airport designs still require ninety-degree turns on taxiways. The logical solution would be to soften the angles, but those have drawbacks too. The advantage of right-angle taxiways is they can be used for exiting runways from landings in either direction. The drawback is the need to stop before making the turn, but if you stop, you also need higher and differential engine thrust and, often, locked wheel turns, which reduces tire life.

Pilots do not have an optimal view of approaching aircraft while waiting at the end of the runway at a ninety-degree angle, but if the hold short was angled, it would then require a more than ninety-degree turn onto the runway, so you can see the conundrum. The solution is more movement area and bigger design/construction budgets, but in the meantime, here are some discussion topics for your next pilot safety meeting:

  • Do you brief which exit and which side of the runway you’re planning after landing?
  • Is the Pilot Monitoring verifying ground speeds before the high-speed exit taxiways?
  • If you have a 20-knot direct headwind on a contaminated runway, the wind is helpful, but as soon as you turn off the runway, that crosswind becomes a safety factor on icy surfaces. It's more pronounced on ninety-degree changes.
  • Did you know that high speed exit taxiways only allow you to taxi in one direction after using it? Most are not designed for a reverse turn, even if your FBO is behind you.
  • Did you know high-speed exit taxiways are not runway entrances or crossings?
  • All high-speed exit taxiways have a 30-degree angle with the runway, and the radius of the turn off the runway is always 1500 ft.
  • High-speed taxiways WITH a reverse turn require a 150-degree turn from the runway, but they have a nose gear steering angle of no more than 50 degrees if you follow the markings properly.
  • High-speed exits always lead to a parallel taxiway and never into a runway.
  • Is the Pilot Monitoring advising when the aircraft is off taxi lines?

Advanced Aircrew Academy has more than 100 topics of eLearning for your entire flight department, including Runway Excursions. For more information about training and customization for your Part 91 and/or 135 flight department, or 843-557-1266.