Story ID: 
AINsight: The Dangers of a High-energy Approach
By: Stuart “Kipp” Lau
Caption: Two aircraft overshot runways but were saved by an engineered materials arresting system
Word Count: 1473
Earlier this month, on September 3, two aircraft at two different airports overshot runways only to be saved by an engineered materials arresting system (EMAS). One incident occurred in Illinois, while the other took place in Florida; there were no serious injuries.
The following day, the FAA celebrated EMAS as an important technology that “enhances aviation safety by preventing potentially catastrophic runway overruns.” A far better strategy is to keep the aircraft on the runway.
FAA Administrator Bryan Bedford said these “incidents in Chicago and Boca Raton clearly demonstrate the lifesaving value of EMAS technology. These two systems did exactly what they’re designed to do—stop aircraft safely when they go off the runway. This technology is making a real difference in preventing serious accidents.”
EMAS is a bed of lightweight, crushable material installed at the end of a runway to slow down aircraft that overshoot, undershoot, or veer off the runway. Currently, 122 EMAS are installed at 70 airports in the U.S., according to the FAA.
Agreed, EMAS is an amazing invention. Other than luck, EMAS is the last line of defense during a runway excursion that, if installed, prevents almost certain damage or destruction when an aircraft departs a runway.
September Saves
In the first incident, a Gulfstream G150 overran Runway 34 at Chicago Executive Airport (KPWK) and stopped beyond the end of the runway, penetrating an airport perimeter fence. At the time of the event, according to ATC, there was light rain falling, and the runway surface was 100% wet. Reports from ATC suggest that the aircraft touched down about halfway down the 5,000-foot-long runway but failed to stop before reaching the end of the runway.
According to records, the recent G150 runway excursion was the third EMAS “save” at KPWK. EMAS was installed at the airport in 2014 at the ends of Runway 34 and Runway 16.
In 2016, a Dassault Falcon 20 overran Runway 16 during an early morning landing attempt. Five years later, a Dassault Falcon 900EX, attempting to land in gusty winds and snow, departed the end of Runway 16 and came to a stop on the EMAS bed.
Another KPWK runway excursion occurred, in 2020, when a Bombardier Learjet 60—on a visual approach to Runway 34—landed on the much shorter (LDA 3725 feet) Runway 30. Runway 30 does not have EMAS installed, and the aircraft impacted the airport perimeter fence.
The second runway excursion incident this month occurred at the Boca Raton airport (KBCT), where a Bombardier Challenger 300 overran Runway 05 (5,580 feet landing distance beyond the threshold) and came to a stop in the EMAS bed near a busy roadway. Reports indicate that the aircraft entered EMAS at a groundspeed of 50 knots, as recorded by ADS-B.
Swiss Cheese, Meet Velveeta 
James Reason’s Swiss Cheese model of accident causation is often used in risk analysis and risk assessments. This model has layers of Swiss cheese lined up, each with various holes—with different placement and sizes—representing the defenses that are used to prevent an accident. 
In theory, when the holes align, weaknesses and lapses are exposed in each defense that ultimately contribute to an accident. Traditionally, each slice of cheese represents human, technical, environmental, or organizational domains. 
In the context of a runway excursion, the slices of cheese may represent a pilot’s physical (fatigue) or psychological state (decision making, time pressure), aircraft system status (brakes, ground spoilers), runway condition assessments, landing distance calculations, airspeed computations, or other safeguards such as policies and procedures. A lapse or weakness in these factors results in a runway excursion.
EMAS is a defense that accounts for (and sometimes masks) these mistakes or failures. In essence, EMAS is a solid block of Velveeta—that delicious gooey “pasteurized prepared cheese product”—sitting at the end of the runway that will potentially save your life.
[Note: There are many accident causation models, but none emphasize a point by crafting (not Kraft) a cheesy blog.] 
Final Approach Speed
According to the Flight Safety Foundation (FSF), its Approach and Landing Accident Reduction (ALAR) toolkit states, “Assuring that a safe landing can be conducted requires achieving a balanced distribution of safety margins between: (1) the computed final approach speed (also called the target threshold speed); and (2) the resulting landing distance.”
The FSF ALAR Task Force found that these high-energy approaches were a factor in 30% of the 76 approach and landing accidents and incidents analyzed. Another FSF study found that 30% of 329 worldwide approach and landing accidents were related to “fast approaches and/or touchdowns.” 
Final approach speed is the airspeed that is maintained down to 50 feet above the runway threshold if the calculated aircraft performance is to be achieved.
Vref is defined as 1.3 times the stalling speed in the stated landing configuration and at the prevailing aircraft weight. Final approach speed (Vapp) is defined as Vref + corrections.
Final approach speed computation is typically based on gross weight, wind, certified landing flap configuration, aircraft system status (abnormal configurations), icing conditions, and the use of automation (autothrottles or autoland). 
Final approach speed provides the best compromise between handling qualities (stall margin and controllability) and landing distance. It’s important to note that airspeed corrections to final approach speed are not cumulative, and only the highest airspeed correction is typically added to Vref.
Common Approved Final Approach Speed Additives
Wind corrections provide additional stall margin for airspeed excursions caused by turbulence or wind shear and gusts. Manufacturers use different methods to determine wind corrections.
These corrections are usually a combination of one-half or one-third the steady wind state plus the entire gust value up to a maximum value of 20 knots. These methods vary by aircraft manufacturer; use only the method recommended in the aircraft AOM/FCOM (or POH).
Typically, there are no wind corrections for crosswind or tailwind conditions (other than limitations such as maximum demonstrated crosswinds or tailwind limitations). 
Flap configuration adjustments are based on certified landing flap settings. Aircraft with multiple certified landing flap configurations will use the full flap Vref plus a correction for a reduced flap setting (such as Vref plus XX knots) or a specific Vref for each approved flap setting (Vref F.30 vs. Vref F.20).
Abnormal configuration corrections account for single or multiple system malfunctions. These corrections are used to ensure a safe stall margin and controllability. Typically, a lookup table is included in the aircraft quick reference handbook (QRH) that lists airspeed and landing field length adjustments (Example: A slat malfunction may add 30 knots to Vref, and the landing field length would be increased by 40%.)
Some aircraft manufacturers include final approach speed adjustments for the use of automation such as autothrottles or autoland capabilities. A common example is an additional 5-knot adjustment to the final approach speed (Vref + 5 knots) to maintain the target final approach speed when using autothrottles.
Ice accretion (severe) in-flight may require an airspeed correction due to the possibility of ice forming on unheated surfaces of the aircraft and on the wing surfaces above and below the fuel tanks. 
Wind shear should be avoided by either delaying the approach or diverting to an alternate airport. However, if an approach is conducted in wind shear conditions, an airspeed correction (usually 15 to 20 knots) and a reduced flap landing (if certified) is recommended. 
Advice To Keep the Aircraft on the Runway
Following the early September EMAS saves, there were several online discussions related to final approach speeds. Some provided sound guidance based on the FAA Airplane Flying Handbook or manufacturer’s AOM/FCOM procedures, while others were wrong based on personal technique or aviation lore.
In one example, several pilots of a large business jet model—with “global” capabilities—suggested adding an additional 10 to 15 knots to Vref to improve controllability during landings. Another group of pilots promoted adding extra speed as “money in the bank” or “10 additional knots for Momma.”
According to the FSF data presented, excessive energy is a factor in nearly one-third of all approach and landing accidents. Excessive airspeed during approach may cause the actual landing distance to exceed the available runway.
Let’s be clear: the only acceptable method to adjust the final approach speed is the guidance contained in the approved aircraft operating manual. Each approved adjustment to the final approach speed has a corresponding landing distance (performance) value. Additional airspeed corrections arbitrarily added by the flight crew negate the approved aircraft landing performance figures.
The opinions expressed in this column are those of the author and are not necessarily endorsed by AIN Media Group.