Approved aircraft flight manuals are chock full of precision airport performance data, numbers obtained by some of the aviation industry's most skilled and experienced test pilots. These data have been thoroughly verified and validated by airworthiness certification authorities to assure they accurately reflect the ideal performance capabilities of the aircraft under certain conditions specified by government authorities.
Both FAR Part 25 andCS-25 state that the numbers obtained for certification purposes must not require “exceptional piloting skill or alertness.” Standard runway performance assumptions include a “smooth, dry or wet, hard-surfaced runway,” perhaps one that is grooved or porous to enhance wet surface friction; standardized relative humidity values; a regulatory 2-sec. engine failure pilot recognition delay; and flawless anti-skid braking performance, among other idealized conditions.
What's not written into the regulations, though, can have a critical impact on actual aircraft performance on any given day in your flight operations schedule. The airplanes you operate may not be brand new. Runways may undulate, causing partial loss of weight on wheels or changes in pitching moment. Surfaces may be contaminated with dust, light debris, tire residue and oil droplets, along with pools of standing water, ice, sleet or snow. Gusting winds may make precise speed and directional control considerably more challenging compared to idealized certification flight test conditions. One or more of your tires may blow, your engines may eat birds at rotation, your nose wheel steering could malfunction.
“You're being naïve if you believe you'll always operate in ideal conditions. Real world conditions show us how sterile is the certification flight environment. You have to respect the world in which you're operating. So, don't bet your life on book numbers,” says one experienced flight department manager with a fleet of 17 aircraft.
Even under highly controlled flight test certification conditions, most average line pilots cannot achieve the same results as test pilots because of the shock and awe of an unexpected emergency.
“There is fog, there is chaos in the real world when an emergency occurs. We can't just flip into an ideal test pilot mindset,” the flight department manager said. This even can occur during the controlled conditions of certification flight test. Experimental test pilots for several business aircraft manufacturers have suffered fatal accidents during certification work. “There are unforeseen things that can just reach up and smite you.”
Surprises are few and far between for test pilots. They have the luxury of knowing that the emergency condition will happen in advance. That enables them to carefully rehearse each test point written on a flight test card, so as to extract ideal performance from an aircraft. So prepared, they can fly the emergency condition profile with great precision and near perfect timing. If the test doesn't go as perfectly as planned, they can repeat the procedure until they extract the performance they want from the airplane. It's a little like the “do-overs” pilots practice in flight simulators.
“You get into simulator training syndrome,” says Robert Agostino, head of a Texas-based flight department. “If it's Tuesday, it's hydraulic failures. Wednesday, it's electrical failures. Thursday, it's engine failures during hot and high departures. Friday, it's cold weather operations.” The rote training procedures assure that pilots will be pumped up to handle engine failures during a specific training session. In the real world, crews seldom know that an engine failure or other runway emergency will occur prior to beginning takeoff roll or commencing a landing approach. Engine failure or other emergency recognition time easily may exceed the 2-sec. delay specified in aircraft certification regulations.
Faith in Factory Numbers — With Qualifiers
Plenty of corporate flight departments are comfortable operating from runways that meet minimum approved AFM requirements for takeoff, one-engine inoperative climb and landing, assuming that they're using runways longer than a specified minimum length. If they'll be using shorter runways, then they undertake a comprehensive review of a close look at runway performance
Burbank, Calif.-based Avjet, for instance, uses a 6,000-ft. minimum length as the trigger for undertaking a detailed runway analysis for its large-cabin business aircraft, explains director of operations Gregory Wilcox. “Our operational control staff uses a number of flight planning tools, including Universal Weather, ARINC and UltraNav, to assure we have safe margins.”
Part of the detailed airport analysis includes looking at actual obstacle clearance requirements for each runway. Many landing facilities have close-in obstructions that require more than the regulatory 200 ft./nm climb (3.3%) gradient for IFR departures.
Avjet, among other operators, imposes several restrictions on operating out of certain airports in mountainous terrain, including Aspen, Eagle, Telluride and Rifle, along with Sun Valley, Jackson Hole, Lake Tahoe and Tahoe-Truckee. Authorization to use such “special-use” landing facilities only is allowed during daylight conditions with VFR weather from the final approach fix to the runway and a reported visibility of at least 5 mi. Use of certain runways may be prohibited for landing and others may be off limits for takeoffs.
Many larger flight departments require more than one level of approval for operating out of such special-use airports. The validation process, including compliance with specific operating limitations for special-use airports, also gives the flight department manager the confidence to back up decisions made by flight crews to divert rather than land and delay or cancel a departure if warranted by winds, weather, runway contamination or warm temperatures, among other unfavorable conditions.
Airlines have similar procedures for challenging airports, ones with comparatively short runways, close-in obstacles, frequent hot-and-high conditions or nearby terrain hazards, says Don Gunther, former vice president of safety for Continental Airlines.
Flight crews must be specially trained and qualified for operations at certain airports, such as Tegucigalpa, Honduras' Toncontin Airport (MHTG). “It's all about how to mitigate risks for particular airplanes,” he says. “Tegucigalpa, for instance, is a special qualification airport, one that requires the crew to train to proficiency in the simulator and then fly with a [Tegucigalpa] qualified check airman aboard.”
Gunther also says that airlines use FOQA (Flight Operations Quality Assurance) data, collected from a quick-access flight data recorder or stand-alone recording device, to monitor overall crew performance. Based upon FOQA data, Continental developed an RNP procedure for Toncontin Airport that enables pilots to fly more-precise approaches and touch down at the desired point on the runway with more consistency.
Smaller Flight Departments, Shorter Runways
Large organizations, such as major corporate flight departments or certificated air carriers, frequently have a dedicated performance engineering staff that can fine tune runway requirements and assure adequate obstacle clearance margins.
Smaller flight departments seldom have such capabilities, so some are inclined to use more conservative runway performance numbers. They also operate from non-Part 139 general aviation airports that don't have the same requirements for full-time staffing, aircraft rescue and firefighting, and airport security, plus fence maintenance, wildlife threat mitigation and signage and traffic control, along with pavement condition, lighting and airport facilities monitoring as airports approved for scheduled air carrier operations.
In short, operating out of a non-Part 139 airport may entail more potential risk from imperfect pavement, intrusions by wildlife, pedestrians or vehicles on runways, and uncharted obstacles.
There is a correlation between such risk factors and the diverse causes of aborted takeoffs in business aircraft. Agostino claims that only 8-10% of all aborted takeoffs in business aircraft are caused by engine malfunctions. Twenty-nine percent, in contrast, are caused by tire failures. There also are more frequent collisions with wildlife at non-Part 139 airports and more runway incursions.
But approved aircraft flight manuals only have accelerate-stop and accelerate-go takeoff performance numbers based upon accelerating to an engine failure speed and then either continuing the takeoff on the remaining engine(s) or aborting the takeoff roll and braking to a stop on the remaining runway.
“The data assume that you'll abort for any malfunction prior to V1 (loosely defined as the takeoff decision speed),” says Agostino. There is no AFM data for stopping an aircraft or continuing the takeoff after suffering a tire failure, among other hazards that might be encountered.
Agostino also said his pilots, while well trained and highly disciplined to follow SOPs, are subject to the same “shock and awe” reaction times as other line pilots. He claims most pilots cannot react to a takeoff emergency in less than 3.5 sec., resulting in an additional 1.5-sec. delay and adding as much as 200 ft., or more, to accelerate-go or accelerate-stop distances.
For all those reasons, Agostino's pilots add 10% to the published approved AFM takeoff field length distances. That assures they'll have extra runway margins to cope with emergencies, including engine failures, blown tires and other takeoff malfunctions. He also requires his pilots to use Part 135 factored landing distances, rather than basic Part 25 landing distances, for all the same reasons.
The flight department manager with the 17 aircraft fleet uses an even more conservative 15% margin for takeoff. If the approved AFM TOFL is 5,000 ft., for instance, he requires his pilots to use runways no shorter than 5,750 ft.
“We use the 'Chain of Pain' process. We'll allow pilots to use shorter runways, but such operations must be pre-approved by several managers in our flight department. If the request gets all the way up to my desk, the flight crews really will need mission critical justification. That hasn't yet been the case.”
Mitigating Risk — Airline Approach; Business Aircraft Approach
Airline pilots long have had the advantage of practicing maneuvers at challenging airports in the simulator to achieve high proficiency. Airlines typically have data and terrain for most or all of the airports in their route structures programmed into their flight simulators because they fly to such destinations several times per week.
Historically, that's not the case for business aircraft operators. They fly to many more small airports and they may only visit those landing facilities once or twice per year. Navigation and terrain data for all airports used by business aircraft operators are not programmed into most flight simulators operated by the major Part 142 training services firms.
Business aircraft pilots can't rehearse landings and takeoffs at the myriad challenging airports to which they fly during simulator training as readily American, Copa, Delta, TACA andpilots can practice operations at Tegucigalpa in the “box.”
Airline pilots who are qualified to fly into Tegucigalpa, among other challenging airports, also are likely to make several landings and takeoffs at such facilities several times per year. The operational frequency builds both the confidence and competence of flight crews. FOQA monitoring enables airlines' operations departments to adjust training or operational procedures to fine-tune pilot performance and effectively manage risk.
Business aircraft pilots, in contrast, usually don't have access to FOQA data for the types of aircraft they operate. The first fleet-wide OEM FOQA monitoring effort was undertaken by Eclipse Aviation prior to its November 2008 bankruptcy. Several safety adverse trends were identified by the Eclipse FOQA program, but insufficient data were collected to identify problems at specific airports. Now, FOQA programs are available for several other business aircraft, including models made by, and Gulfstream.
But FOQA data are sparse for most general aviation airports. So, it's not easy for individual operators to use FOQA to identify risk trends and make corrections to technique or procedures.
However, the most conscientious business aircraft operators require their crews to debrief each mission, openly and thoroughly, so that lapses can be identified and corrections can be made. Such comprehensive post-mission critique sessions may not be comfortable for pilots with easily bruised egos, but they can be most valuable for improving airmanship and assuring compliance with SOPs. In time, debrief sessions also build crew camaraderie and boost CRM.
Debriefing sessions conducted after flights between airports that are frequently used by operators are effective tools for fine-tuning your flight operations. For airports that you don't often visit, they're still valuable tools. But crews still will lack the frequency of experience that builds proficiency and precision.
Your flight operation may not choose to add extra margins to approved AFM runway distances at all airports. But, if you're planning to operate occasionally from challenging airports, especially facilities in mountainous terrain or ones with short runways, then increasing the minimum required runway length can provide the critical buffer you need to keep out of harm's way should your aircraft run into trouble. BCA