http://www.aviationnow.com/avnow/news/channel_bca_story.jsp?id=news/land0806.xml The FAA's New Landing Assessment Rule
By Patrick Veillette, Ph.D.
07/25/2006 02:12:04 PM
On June 7, the FAA posted an announcement in the Federal Register that all FAR Part 121, 135 and 91(K) operators will be issued a new Operations Specification (Ops Spec) or Management Specification (MSpec) requiring completion of a new en route landing distance assessment for all their turbojet aircraft. This calculation must take into consideration current runway conditions and allow a full-stop landing with at least a 15-percent safety margin beyond the actual landing distance, on the runway to be used, in the conditions existing at the time of arrival, and with the deceleration means and airplane conditions to be used. The calculation must occur as close to the time of arrival as practicable. (Currently, regulations only mandate such calculations occur prior to departure of the aircraft.)
And the feds are not waiting long for a response. The FAA wants operators to file their proposed procedures for compliance with their respective principal operation inspectors by Sept. 1.
The announcement caught a lot of operators by surprise. I conducted an informal poll of 12 turbojet operations during my last tour on the road in mid-June. They ranged in size from one to five jets on their Part 135 certificates. All 12 seemed caught off guard with several of them asking me to forward them a copy of the announcement. A couple of them were ready to throw in the towel, expressing frustration with ever-increasing federal regulation. After they actually read and discussed the directives in the announcement, I heard complaints such as "I don't have a large staff to put together this information," and "I don't know where to find some of the information I need for this."
The National Air Transportation Association is taking a dim view of the proposal, pointing out that it establishes new regulations, but does so after bypassing the required rulemaking process, and failing to "solicit comments from the affected industry and public to the notice."
What led the FAA to make such a sweeping announcement? The dramatic pictures of a Southwest Boeing 737 sitting in a roadway off the end of the runway at Chicago's Midway airport last winter spurred the FAA to evaluate the adequacy of regulations and guidance information in areas that might come under scrutiny during the investigation of the overrun accident that claimed the life of a little boy riding in a car struck by the Boeing.
The problem of aircraft running off the ends of slippery runways in the United States should have been corrected a long time ago. An FAA analysis of accident and incident data for 1978 to 1993 uncovered 769 instances of aircraft overruns and excursions where ice, snow and slush were contributing factors. These included aircraft used in scheduled airline service as well as air taxi and general aviation.
According to Transport Canada's Transportation Development Center, the risk of a jet aircraft overrunning the end of the runway on landing when the runway is slippery is approximately 13 times greater than when the runway is dry. The risk of overruns on landing for aircraft without reverse thrust are approximately four to seven times greater than for aircraft with reverse thrust.
As noted in earlier articles, overruns are particularly problematic among the business jet community, and runway contamination was often a prime contributing factor. A Flight Safety Foundation study of business jet safety from 1991 to 2003 found that roughly 70 percent of the 59 landing overrun accidents and all 176 reported landing overrun incidents involved contaminated runways. By the way, rarely were the pilots given an adequate description of the braking action to be expected in the majority of these events.
The lack of adequate information to pilots regarding runway conditions was identified in an NTSB special investigation that was initiated in 1982, just days after Air Florida Flight 90 hit the 14th Street Bridge adjacent to Washington National Airport on a snowy day in January. When a jet slams into a crowded commuter bridge within eyeshot of FAA headquarters, maximum attention from regulators and investigators is inevitable. The question of aircraft performance from a slush-covered runway was definitely on the minds of the investigators as they pulled the 737's wreckage from the ice-covered Potomac River.
Ironically, 10 days later, a World Airways DC-10 touched down in Boston on a runway hard-packed with snow and glaze ice. Despite the flight crew's best effort to slow the jet, it slid off the end of the runway going 49 knots. Two people died in the mishap. When the NTSB's special investigation was done, it confirmed the need for (1) reliable, objective means to measure runway friction during all weather conditions, (2) reliable methods of transmitting that information to pilots and (3) methods of correlating measured runway friction to airplane performance. A generation has passed since that report, yet those same deficiencies persist.
The FAA's post-Midway internal review found that approximately half the operators' manuals lacked policies for assessing whether sufficient landing distance exists at the time of the arrival, even when runway or aircraft conditions were different from those planned at the time the flight was released.
Additionally, it found that not all operators who perform landing distance assessments at the time of arrival have procedures that account for various runway surface conditions or reports of reduced braking action. Many operators who do perform landing distance assessments at the time of arrival do not apply a safety margin to the expected actual (unfactored) landing distance. Some operators have developed their own contaminated runway landing data and in some cases, these data are less conservative than the airplane manufacturer's data for the same conditions.
While these findings support action, the FAA's proposal has many weak points.
One problem is that the landing distances determined under 14 CFR Part 25, section 25.125 and published in FAA-approved AFMs are considerably shorter than the landing distances achieved in normal operations since the former are determined using flight test methods and analysis criteria not representative of everyday practices. For example, test pilots often use high touchdown sink rates (as high as eight feet per second) and approach angles of -3.5 degrees to minimize the airborne portion of the landing distance. There is only enough flare to keep the touchdown sink rate structurally tolerable. How aggressive have they been? The flight crew of a DC-9/MD-80 doing landing performance tests at Edwards Air Force Base back in May 1980 came down so hard the empennage broke off.
The time taken to activate deceleration devices is markedly different between the flight test setting and out in the operational world. Test pilots initiate maximum braking as soon as possible after landing. In daily operation pilots try to be smoother and easier on the hardware. Many major air carriers prefer the use of thrust reversers during the high-speed portion of the landing rollout to reduce the wear and tear on the brakes, and allow for a "quick turn" on the ground. Such everyday practices result in significant differences with AFM data.
Further, flight tests are typically conducted in ideal atmospheric conditions, allowing the test pilot to easily establish a stabilized approach without having to compensate for the turbulence created by afternoon thermals or gusty winds, so common in line flying. Out in the real world, flight path deviations do occur, and as professional pilots we try to smoothly correct back to the flight path without giving our passengers a roller coaster ride. If a sudden wind gust or thermal balloons the aircraft 100 feet over the threshold instead of the usual 50, landing distance will be affected. According to data derived for the Flight Safety Foundation's "Approach and Landing Accident Reduction" task force report, such a gust would result in a 1,000-foot increase in landing distance.
How often have you touched down, looked at the wind sock in the touchdown zone area and realized it was indicating different winds than those reported on the ATIS? It isn't uncommon. You can bet the flight test crews had accurate touchdown zone wind reports in the computations of the landing distance. It is considered good operating practice to add half the gust factor to the final approach speeds as a safety margin. Thus a 10-knot wind gust can translate into a 20-percent increase in the landing distance. Do any of your AFMs contain an "easy to find" adjustment to your landing distance performance/requirement with an added gust factor? Probably not.
Line pilots also have to deal with crosswinds, which also have a negative impact on braking effectiveness in line operations (see "Crosswinds and Contaminated Runways," B&CA, January, page 28). I've combed through several business jet AFMs but haven't been able to easily find any landing distance performance adjustment figures for crosswind landings. Usually about the only crosswind information that is readily available in an AFM is the crosswind limitation. However, there is an additional consideration when landing in a crosswind and that is the amount of reverse thrust that can be used on airplanes with tail-mounted engines due to rudder blanking effects.
Does your AFM contain landing performance data in case you have residual ice on the wings after activating the deicing boots? Is there a speed adjustment and a landing distance adjustment? And by the way, does the AFM specify whether you were to carry that extra speed into the flare and to touchdown? This is yet another area in which the AFM landing performance numbers and guidance are frequently inadequate.
And if you regularly rely on thrust reversers for landing, be aware that the FAA has stated it "has not found thrust reversers reliable enough to allow landing distances to be based on their use. This policy provides some additional safety margin for airplanes with reversers that are operable and used in combination with (not in lieu of) maximum braking from wheel brakes and spoilers. If the FAA were to allow the use of reverse thrust as a condition for using, for example, an 85-percent factor for calculating landing distances, the result would be to assign an arbitrary performance capability to reverse thrust, which may or may not be met by different airplane/engine/reverse thrust combinations. Also, it would be inconsistent with the treatment of reverse thrust by the FAA for airplane type certification purposes, which has not allowed landing distances to be based on the use of reverse thrust."
The June 7 announcement said the FAA considers a 15-percent margin between the expected actual (unfactored) landing distance and the landing distance available at the time of arrival as the minimum acceptable safety margin for normal operations. The agency defines "actual landing distance" as "the landing distance for the reported meteorological and runway surface conditions, airplane weight, airplane configuration and ground deceleration devices to be used for the landing. It represents the best performance the airplane is capable of for the conditions."
It's interesting that the FAA is using 15 percent as the minimum acceptable safety margin in this proposed change. It had a very different value in mind as a safety margin when it adopted the rules governing fractional aircraft operations.
In its preamble to Subpart K of Part 91 operations, the FAA said that the landing safety margins required of Parts 121 and 135 -- the so-called "60-percent rule" -- provided "realistic landing distances for use in the operating environment" and should be applied to the fractionals as well.
The precedent and logic of the 60-percent rule are solid, so it's a mystery why the FAA would abandon it now for something less.
Furthermore, Sections 121.195(d), 135.385(d) and 91.1037(e) require an additional 15 percent be added to the required landing distance when the runway is wet or slippery, unless a shorter distance can be shown using operational landing techniques on wet runways.
Under the current regulations, can an aircraft be released to an airport that doesn't meet the safety margin requirement? Savvy readers of this section of the FARs know the answer is yes. Sections 121.195(e) and 135.385(e) allow an airplane to depart even when it is unable to comply with the safety margin if an alternate airport is specified that does meet the safety margin. Herein the FAA provision implies that a landing distance assessment is accomplished before landing to determine if it is safe to land. These are the current legal requirements for dispatch; however, they alone do not assure that the airplane can land safely within the distance available for the conditions that exist at the time of arrival, particularly if the runway or meteorological conditions, airplane configuration, airplane weight or use of airplane ground deceleration devices are different than those used in the preflight calculation.
I asked Charles Lloyd for his perspective on this. With a master's degree in mechanical engineering, 20 years of flight and sales experience with two major business aircraft manufacturers, and now a Cessna 560XL fractional captain, and having probably flown with hundreds, possibly thousands of pilots, he has unique insight. First, he is adamant that "pilots fly the aircraft by the certification numbers [and] adding 15 percent will not fix the problem." He points out that while some pilots recognize the importance of being precisely on speed (Vref), on glidepath (50 feet over the threshold) and aiming for the touchdown zone, in order to achieve the Part 25 landing performance numbers, they often don't realize they must go to flight idle over the threshold as well, because that's what's done in the Part 25 testing. Illustrating the point, he recalled a fellow pilot landing a King Air at 4,400-foot-long Hilton Head Airport "not coming to idle until touchdown when we were passing the 3,000-foot marker still five feet in the air. This person got religion fast and finally understood why a turbine needs to be at flight idle over the threshold."
Lloyd's experience points to the need for a well-developed training program to dispel commonly held pilot myths and misconceptions. The FAA agrees and has directed operators to use flight training programs that include procedures for ensuring optimal stopping performance on contaminated runways. According to the FAA's recent announcement, "All flight crewmembers must be made aware of these procedures for the make/model/series of airplanes." The procedures are to be incorporated into training curriculum, and all flight crewmembers must have hands-on training and demonstrate proficiency in the procedures during their next flight training event.
So, if there's a jet on your air carrier certificate, you have a lot to do in a relatively short timeline if the schedule in the notice holds. That's a problem, obviously.
The greater concern, however, is making flight operations safer. And to accomplish that in calculating landing distances pilots must have accurate timely runway condition information, and it must be in a form that can be easily used. Currently, when I receive a Mu-Meter friction reading, I have no ability to translate that directly into the amount of landing distance I actually need. None of the charts available for my use have any correlation between the Mu-Meter and runway needed. Braking action reports? I make no apology for skepticism since that vital part of the landing distance assessment/equation is woefully lacking with no improvements likely in the near future.
Pilots must have readily accessible and easy-to-use charts in the cockpit that will enable them to take the present runway surface conditions, environmental conditions and the aircraft's braking configuration, and determine if the runway is long enough for a safe landing.
At this time, there are few, if any, charts or methods that make this easy to do. I've watched countless colleagues struggle with chart interpolation or sweat out doing weight-and-balance calculations during recurrent training. Let's be realistic, there are a lot of pilots who are uncomfortable making relatively simple math calculations in a benign classroom environment. Trying to load them up with additional mental workload in the terminal area environment is asking for more human error. As one colleague put it, "Keep It Simple Stupid!" It's hard to disagree with that admonition.
OpSpec/MSpec C082, "Landing Performance Assessments After Departure" for all turbojet operators should have been available from the FAA July 20. It's sure to be a closely read document. Procedures must be in place by Sept. 1 and operators must be in compliance by Oct.1, 2006. B&CA
DEADLINES . . . MARK YOUR CALENDAR
The FAA issues mandatory OpSpec/MSpec C082, "Landing Performance Assessments After Departure."
Sept. 1, 2006: Operators will be required to submit their proposed procedures for compliance with this notice and OpSpec/MSpec C082 to their principal operations inspectors no later than this date.
Oct. 1, 2006: If not currently in compliance, a turbojet operator shall be brought into compliance with this notice and the requirements of OpSpec/MSpec C082 no later than this date.
Reprinted from the August 2006 issue of Business & Commercial Aviation magazine.
