FAA changes landing distance rules for commercial operators

 - September 14, 2006, 5:43 AM

After a Southwest Airlines Boeing 737-700 ran off a snowy runway while landing at Chicago Midway Airport on December 8 last year, the FAA launched an internal audit of factors related to that accident. One result of that audit is a new FAA policy that imposes mandatory 15-percent landing distance safety margins on Part 91K (fractional), 125, 121 and 135 jet operators. The rule was published in the Federal Register on June 7.

The new requirement is simple: no operator to which the policy applies is allowed to land on any runway without 15 percent more runway available than the actual landing distance. If weather conditions change en route, pilots will have to recalculate the actual landing distance needed, based on runway conditions and use of available equipment such as thrust reversers and spoilers, add 15 percent to that and determine if the destination runway is long enough. If not, they will have to find a suitable runway.

While the NTSB had not posted anything more than a brief preliminary report on the Southwest accident on its Web site, it did address the issue in a safety recommendation dated January 27. The flight crew’s calculation of runway needed to land, using the airline’s operational performance computer, showed that using the WET-FAIR runway braking condition parameter yielded a margin of 560 feet. In other words, if the condition of the runway actually matched the WET-FAIR parameter, then the pilots should have been able to come to a complete stop with 560 feet of runway remaining.

“During post-accident interviews,” the NTSB recommendation letter stated, “the flight crewmembers told Safety Board investigators that they considered 560 feet to be an acceptable safety margin and, therefore, decided to execute the landing.”

The NTSB didn’t take issue with the remaining runway length but criticized the FAA for allowing Southwest Airlines to consider thrust-reverser credit when determining landing distance in that model 737.

“The Safety Board is concerned that the landing distance safety margin is significantly reduced on a contaminated runway when the reverse thrust credit is allowed in landing stopping distance calculations. As a result, a single event, the delayed deployment of the thrust reversers [the NTSB said the flight crew waited 18 seconds after touchdown to deploy the reversers], can lead to an unsafe condition, as it did in this accident. The Safety Board concludes that the safety margin must be restored to those airplanes for which the reverse thrust credit is currently allowed in landing performance calculations.”

Most business jet operators don’t recognize thrust reverser credit when landing on contaminated runways, but the FAA’s new policy accepts that a variety of factors and equipment can be considered when calculating landing distance. Once that distance is calculated, the policy also requires adding the 15-percent safety margin, which probably would not have been obtainable in the Southwest Airlines case at Midway. (The runway used, 31C, is 6,522 feet long. Subtract 560 feet [the landing distance for the WET-FAIR wet-fair parameter] and that leaves 5,962 feet or a 9-percent margin. Add 15 percent–894 feet–and the total runway length with the new margin is 6,856. Would 334 extra feet have made a difference in this accident?)

The FAA requirements in the new policy are as follows: No later than Sept. 1, 2006, jet operators will be required to have procedures in place to ensure that a full-stop landing, with at least a 15-percent safety margin beyond the actual landing distance, can be made on the runway to be used, in the conditions existing at the time of arrival, and with the deceleration means and airplane configuration that will be used.

“This assessment must take into account the meteorological conditions affecting landing performance (airport pressure altitude, wind velocity, wind direction and so on), surface condition of the runway to be used for landing, the approach speed, airplane weight and configuration and planned use of airplane ground deceleration devices. Turbojet operators will be required to ensure that flight crews comply with the operator’s approved procedures. In other words, absent an emergency, after the flight crew makes this assessment using the air carrier’s FAA-approved procedures, if at least the 15-percent safety margin is not available, the pilot may not land the aircraft.”

The formal requirement for this new policy will come in OpSpec/MSpec C082, which will be available July 20. Operators must have procedures in place for complying with the new OpSpec/ MSpec by September 1, and the FAA expects all affected operators will be in compliance by October 1.

Both the National Air Transportation Association (NATA) and NBAA labeled the FAA’s release of the safety margin policy a quasi-rulemaking effort, noting that it was not subject to ordinary public comment and rule-drafting procedures.

“This proposal,” NBAA stated, “exceeds current regulations in place concerning landing procedures, and NBAA believes that, like all new proposals, this one should be subject to the time-tested federal rulemaking process for aviation regulations.”

NBAA also believes the policy is too narrowly focused. “By its nature, the proposal suggests that only one factor– runway landing distance–matters in aircraft landings. In fact, a whole host of factors are involved, including pilot judgment, aircraft weight and other aspects of landing.” Although NBAA didn’t comment on the Southwest accident, some of the “host of factors” presumably could include proper use of thrust reversers and correct application of contaminated runway braking information, an issue the NTSB also raised.

“The FAA’s notice establishes a new regulatory requirement,” NATA explained, “bypassing the required rulemaking process, and is therefore unacceptable. The notice itself states that this is a new requirement, yet the FAA does not adequately explain why formal rulemaking was not conducted.”

NATA is more concerned about the FAA’s cavalier use of OpSpecs/MSpecs to impose new operational requirements. “The FAA attempts to sell this notice as ‘clarification’ of Parts 135.77, 125.351, 91.3 and 91.1009, which place responsibility for the safe operation of the flight jointly with the operator, pilot-in-command and dispatcher. The association submits that funneling new requirements through by claiming ‘clarification’ of these broadly worded regulations is an abusive interpretation of the regulations. The regulations cited by the FAA are general regulations intended to ensure that in all activities the aircraft is operated in a safe manner. They were not created to be used as an excuse for the FAA to impose specific requirements at any time, so that the agency can avoid the rigors of formal rulemaking.”

The FAR Part 91K and 135 regulation permitting operators of large transport-category airplanes to fly into airports where landing weight allows a full stop landing within 80 percent of available runway length shouldn’t be a factor in the safety-margin policy. If an airplane needs the full 80 percent of the available runway length, this still works out to be less than the amount required by the 15-percent margin policy.

For example, on Chicago Midway’s 6,522-foot-long Runway 31C, the 80-percent rule requires a full stop before reaching 5,217 feet. If 5,217 feet is the actual landing distance, adding 15 percent to that brings the required runway length to 6,000 feet, significantly less than the runway’s total length.

To view the new policy, see http://a257.g.akamaitech.net/7/257/2422/01jan20061800/edocket.access.gpo...