AINsight: Preventing Runway Excursions a Complex Task

 - January 27, 2023, 10:00 AM
Aircraft surrounded by investigators after safely stopped in Engineered Material Arresting System following runway overrun
Runway excursions account for one-third of business aircraft accidents and, barring mechanical issues, are preventable. (Photo: Runway Safety)

Runway excursions are a persistent problem in aviation. The NBAA Safety Committee has included runway excursions on its annual list of top safety focus areas since 2015. Canada’s Transportation Safety Board (TSB) has included runway excursions on its annual safety watchlist for more than a decade.

Runway excursions are a towering concern and the most common type of business aviation accident,” NBAA said. According to data compiled by AIN, nearly one-third of all business aviation accidents involve an aircraft overrunning or veering off a runway during takeoff or landing. These accidents cost business aviation operators $900 million per year in injuries and damages.

At this point, runway excursions are a well-known risk and preventable. Volumes of guidance material provide flight crews with best practices to ensure there is sufficient landing distance available and provide information on flying a safe approach under the most adverse conditions. 

The fact that business aviation aircraft continue to overrun runways at an alarming rate is perplexing. In the most recent cases, a Bombardier Learjet 45 crew flew an unstable approach to a wet runway and the pilots of an Embraer Phenom 300 attempted to land on a runway that may have been too short for the conditions.

On November 29, the Learjet 45 was substantially damaged when it overran the 6,022-foot runway at Batesville Regional Airport (KBVX) in Arkansas. According to the preliminary NTSB accident report, the two pilots were injured and the six passengers walked away from the wreckage. 

ATC transcripts and ADS-B data indicate the aircraft was cleared for the RNAV (GPS) Runway 8 approach, and the flight crew canceled IFR upon visually acquiring the runway. The airplane then crossed the final approach fix at 265 knots groundspeed and the runway threshold at 190 knots groundspeed.

The aircraft touched down approximately 2,000 feet past the threshold of Runway 8, which was wet due to earlier precipitation, and began “intermittent braking” about 3,021 feet from the end of the runway. Tire marks were consistent with continuous anti-skid braking application about 2,069 feet from the runway end until the aircraft departed the paved surface traveling at 100 knots. The aircraft then continued through a ditch and came to rest against the airport perimeter fence. 

One month later, on December 27, an Embraer Phenom 300 skidded off the end of Runway 25 at the Hawthorne Airport (KHHR) in California. The aircraft came to rest with its left wing penetrating the airport’s perimeter fence over a busy motorway. There were no injuries to the seven occupants of the aircraft. The landing distance available on Runway 25 was 4,193 feet. 

On the night of the accident, the non-grooved runway was wet due to rain showers. The latest revision of the Phenom 300 pilot operating handbook (POH) included flight operations bulletins with “operational landing distances” and a discussion about landing on wet, non-grooved runways. 

Charts available (“Runway Condition Code 5/Good Braking”) in this POH would suggest that the landing distance required at the time of the accident (14,500-pound landing weight and Vref+5) would provide little to no margin to the runway distance available under those conditions.

The FAA recommends, at a minimum, an additional 15 percent safety margin to be added to the landing distance required. 

Preflight Planning

Regulators require pilots, during preflight planning, to ensure that there will be adequate runway available for landing at the destination. In the U.S., this is covered under FAR 91.1037, 135.385, and 121.195. 

In general, for “dispatch purposes,” if operating a large transport-category turbine aircraft, the required landing distance can be no greater than 60 percent of the available runway (80 percent for certain Part 91 operators). If that runway is wet or slippery, add another 15 percent to the landing distance. These distances are calculated using the expected runway condition at arrival.

Certified landing distances, defined by regulation as the basis for dispatch, is the horizontal distance necessary to land and come to a complete stop from a point 50 feet above the landing surface. It must be determined for each weight, altitude, and temperature.

These “unfactored” landing distances are demonstrated during certification flight tests. During these tests, the aircraft will cross the runway threshold at 50 feet, at Vref, and on a three-degree path, and then touch down with minimal flare and maximum braking after main gear touchdown. 

Factored” landing distance is the unfactored landing distance times a “factor.” FAA and ANAC certification requirements specify 1.67 as the factor. EASA uses a factor that is variable. 

Wet landing distances are obtained through a mathematical calculation using a factor of 1.15 (15 percent); there are no flight tests. So factored wet landing distances are determined by multiplying the factored dry landing distance by 1.15.

Each manufacturer will also determine a contaminated runway landing distance for each contaminate type (standing water, slush, compacted snow, dry snow, wet snow, etc.) and depth. This information is provided to the operator in several ways either through performance software or in a chart in the POH or QRH.

As an example, Embraer publishes a contaminated runway number that is the most restrictive (greatest distance) of the different contaminate types analyzed. 

Landing Distance at Time of Arrival

Before landing, it is recommended—required for some operators—that pilots assess the landing distance at time of arrival (LDTA); this guidance is independent of the preflight landing distance planning requirements. 

In the U.S., FAA Safety Alert for Operators (SAFO) 19001 provides guidance to operators on landing performance assessments at time of arrival. According to this alert, it is applicable to all aircraft operators under Parts 91, 121, 125, and 135.

FAA SAFO 19001 was published to assist operators in developing methods to ensure sufficient landing distance exists to safely make a full-stop landing. This document provides information and guidelines created from government and industry groups after a Boeing 737-700 runway overrun accident at Chicago Midway Airport in 2005. 

EASA operators of large aircraft, both commercial and private, are required to assess LDTA prior to each landing per CAT.OP.MPA.303 and NCC.OP.225.

LDTA is a concept that is intended to provide a more accurate assessment of actual landing distance at time of arrival considering factors such as runway contaminants, winds, speed additives, and touchdown points. This is a more realistic assessment of landing performance using actual conditions versus preflight planning.

It is recommended that the flight crew determine LTDA at a point in time close enough to the destination airport to obtain the most current meteorological and runway surface conditions. Depending on the pilot workload, these assessments could be made shortly after top of descent but before commencement of the approach. 

In addition to LDTA, SAFO 19001 provides amplified discussions on pilot braking action reports (Pireps), runway condition codes (RYWCC), and the runway condition description matrix (RCAM).  

RCAM is a useful document since it provides a direct correlation between runway condition descriptions, RWYCCs, and pilot braking action reports. Often RCAM will include crosswind limitations that become more restrictive as the braking action decreases.

RWYCC are used during the LDTA assessment to locate the appropriate landing distance chart. RWYCC range from 6 (the best) to 0 (nil braking)—there typically is a landing distance chart for each value. Once the LDTA is determined, it is important to multiply that value by 1.15 to get the required 15 percent safety margin.

Pilot Controlled

According to FAA Advisory Circular 91-79A “Mitigating the Risks of Runway Overrun Upon Landing,” several factors cause landing overrun excursions. All of these are cumulative and are under the direct control of the pilot: 

Unstable Approach. Safe landings begin long before the touchdown. Adherence to stabilized approach criteria is a must. If the approach becomes destabilized, go around. Operators should have a “no fault go-around policy.”

Threshold crossing height (TCH). Most aircraft are certified with a TCH of 50 feet. For every 10 feet above the TCH, landing distance is increased by 200 feet.

Extended flare or long landing. Braking on the ground is far more effective than attempting to bleed off energy in the flare. Most landing distances provided by commercial products are predicated on touching down by a specific point on the runway; landing beyond this point invalidates any calculated landing distances.

High touchdown speed. A 10 percent increase in airspeed at touchdown increases the landing distance by 20 percent. A tailwind has a similar effect—for each 10 knots of tailwind, landing distance is increased by 21 percent.

Delay in deploying deceleration devices. Thrust reversers, ground spoilers, and brakes help decelerate the aircraft during the landing roll. Any delay in deploying these devices will affect landing distance. A two-second delay in deploying thrust reversers can add 200 feet to the landing distance. Less than maximum braking will generally add another 20 percent to the total.

To demonstrate the cumulative effects of each factor, Embraer in a recent “Landing Performance and Operational Best Practices” webinar used a Phenom 300 in an example. In this case, the aircraft crossed the runway threshold at 50 feet, at Vref+5, with a five-knot tailwind, and a delayed flare of three seconds. All of this added up to a 36 percent increase—an extra 1,075 feet—in landing distance.

The opinions expressed in this column are those of the author and not necessarily endorsed by AIN Media Group.