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Factors To Consider When Transitioning From Props To Jets, Part 3
A Cessna Citation Sovereign is parked on the ramp.
Air carrier pilots are now required to conduct a formal Landing Performance Assessment. This is usually conducted during the low workload cruise phase using the latest information possible to consider any changes that may have occurred after the preflight planning was accomplished. Failure to accurately predict the effects of the runway surface condition have been a consistent weak point in business jet approach and landing accidents.
This process requires a thoughtful evaluation of the runway’s surface condition. The Jeppesen “10-9” page contains not only the landing distances available and runway widths, but also the composition of the runway surface.
An astute flight crew will consider the effects of predicted precipitation on the runway’s surface. Wet runways have much lower friction levels than a dry runway, and contamination (water, slush, snow, or ice) reduces friction to low levels. While the runways at major airports serving scheduled airlines typically have runways with porous filled concrete, grooves and crowning that assist with the drainage of heavy precipitation, these features are not common at most general aviation airports.
If landing distance data based on the Runway Condition Code/braking action is not available in the aircraft flight manual (AFM), the FAA’s Landing Distance Factors may be used with the AFM dry runway, unfactored (meaning they don’t contain the Part 135 “landing within 60%” computations) landing distance to determine the landing distance required. These factors incorporate a 15% safety margin. For example, a turbojet with no reverse thrust landing on a runway with compacted snow with a reported braking action of good-to-medium should multiply the landing distance by 2.8.
An astute flight crew will also consider the effects on the landing distance in case of Minimum Equipment List items (such as inoperative thrust reversers) or airspeed additives due to icing or wind gusts. Wise flight crews will further consider the availability of electronic or visual approach aids, visual illusions caused by unusual runway slope, nearby terrain or falling precipitation as well as the onset of darkness.
Popular business aviation airports surrounded by challenging terrain have abnormal approaches that strain the conventional definition of “stabilized approach,” with missed approach procedures that are complicated. Additionally, the topography often induces localized weather that can rapidly change, thus there is the likelihood that runway conditions may have changed markedly from the last report you received.
Wise pilots have learned to apply the Boy Scout motto, “Be Prepared.”
No More ‘Greased Landings’
While “greasing a landing” is a goal of distinction in light propeller airplanes, greased landings in jets can result in several undesirable consequences. The manufacturer’s landing distance is based on crossing the threshold at 50 ft., precisely at Vref, then reducing the throttles to idle.
Unlike the landing techniques often used in propeller aircraft, jets achieve the minimum landing distance with firm touchdowns and no delay in lowering the nosewheel. The AFM landing distances are achieved by using maximum braking immediately after touchdown.vThe temptation to “grease the landing” also leads to a long touchdown, lengthening the landing and roll out distances.
The accident and incident history in business jet operations repeats the consistent pattern of inaccurate management of the airspeed and glide path on final approach. A fast approach and/or excess height at the threshold is assured to result in a longer landing distance. Be especially wary of any tailwind component on landing due to the significant increase in landing distance. Tailwinds combined with compromised braking conditions is an unacceptable risk.
Crosswinds create a two-fold negative effect on landing distances. Crosswinds complicate aircraft control, often requiring crossed controls at touchdown (aileron down into the wind with opposite rudder to maintain runway alignment). Even a slight increase in the crosswind from 5 kts. to 10 kts. will quadruple the side aerodynamic force on an aircraft. Not only does the de-crabbing at touchdown consume additional runway distance, but the steering to maintain the centerline lessens the tire’s braking force.
The landing method learned for crosswind landings in propeller aircraft, especially the wing-low method, is incompatible in swept wing aircraft in general, and especially in jets with short landing gear that place wings or under-wing engines closer to the runway. For example, the Citation X incurs a maximum bank limitation of 2 deg. with 14 deg. of nose-up pitch during landing to prevent wingtip strikes with the runway.
Higher Degree Of Skill Needed
Simulator courses don’t cover the unique atmospheric and physiological challenges of high-altitude operations, yet these everpresent conditions create significant threats to flight safety. Mountain waves, jet streams, high-altitude convective turbulence, wake turbulence, decompression, lightning and hail, aeroelasticity, cosmic radiation, volcanic ash, unreliable airspeed indications, UV radiation, high altitude ice crystal icing, and stratospheric turbulence are merely a sample of the vast array of topics that require extra skills and knowledge.
Recently, the FAA’s Air Carrier Training Aviation Rulemaking Committee (ARC) found that even some advanced programs “lack content important to preparing pilots for transport category aircraft operations.” The ARC advocates expanding existing Part 61 and Part 141 training requirements to include additional topics and skills relevant to professional flight operations in a structured training program.
The eventual result should be a pilot with a higher degree of advanced aviation knowledge and skill. The ARC’s recommendations apply equally well to anyone in business and general aviation stepping up to a jet.
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