|
 By: Frances Fiorino 06/25/2006 08:50:11 PM MAKING LANDINGS SAFER A proposed FAA policy revision--spurred by a fatal Southwest Airlines accident last winter--would require turbojet operators to establish methods of ensuring safer landings on contaminated runways. On July 20, the FAA plans to issue a policy change dubbed "OpSpecs/MSpec Co82 Landing Performance Assessments." Under it, all turbojet operators are by Sept. 1 to submit to their principal operations inspectors proposed procedures that would assure a full-stop landing--with at least a 15% safety margin beyond the actual landing distance--could be made on the runway in the meteorological conditions at the time of arrival. Deceleration means and airplane configuration to be used must also be factored in. The procedures are to be in place by Oct. 1. It means flight crews must make a specific calculation not before each landing, but only when they learn en route that conditions at a destination airport have deteriorated. In other words, the revised policy dictates that a pilot may not land an aircraft if a 15% safety margin is not available in the assessment, emergencies excepted, according to the FAA. The policy affects all turbojet operators, Parts 91, 121, 125 and 135, who hold operations or management specifications or Part 125 letter of deviation authority. Foreign operators are excluded. Southwest's runway overrun accident that spurred the changes occurred Dec. 8, 2005, at 7:14 p.m. CST. Flight 1248 was en route from Baltimore-Washington International to Chicago Midway, operating in instrument meteorological conditions. On landing on Midway's snow-covered Runway 31C, the Boeing 737-700 (N471WN) with 103 people on board, continued rolling through a jet blast deflector, an airport perimeter fence and onto a roadway. It came to a stop there after hitting two cars and killing a six-year-old child in one of them. The accident injured another 12 people on the ground and four on board the aircraft. The NTSB's June 20-21 hearing aimed at digging deeper for factual information about the accident--including runway friction measurement and methods used to relay those estimates to the flight crew, and aircraft landing performance on contaminated runways. Investigators continue to examine the braking system's effectiveness and the activation of thrust reversers. The captain, who was flying the aircraft during landing, told the safety board the reversers were difficult to unstow. The flight data recorder readout indicates the first officer activated them, but not until 18 sec. after touchdown and 14 sec. before the collision with the jet blast deflector (AW&ST Dec. 19/26, 2005, p. 11). According to the NTSB documents, a pilot who flew the same aircraft prior to Flight 1248 said the brakes and reversers operated normally. The cockpit voice recorder transcript indicates the tower advised the Flight 1248 crew Runway 31C conditions were "fair the first half," and "poor at the second half." By FAA definition, "fair/medium" conditions indicate "noticeably degraded braking conditions" and crews are to plan for long stopping distances. "Poor" indicates "very degraded" braking conditions with a potential for hydroplaning, and crews should plan for "significantly longer stopping distances." The crew used an onboard laptop performance computer to calculate landing performance, based on factors such as wind speed and direction, aircraft gross weight at touchdown and reported braking action, according to the NTSB. The laptop, using "credit" for use of thrust reversers, calculated what remaining runway would be available after stopping under "wet-poor" and "wet-fair" conditions--and came up with 30-ft. and 560-ft. margins, respectively. In January, the NTSB urged the FAA to prohibit airlines from using thrust reverser credit when determining stopping distances. If credit had not been included, the Flight 1248 laptop computer would have indicated a safe landing was not possible, according to the NTSB. Following the accident, the FAA initiated an internal audit to assess the adequacy of current regulations and guidance information. The agency discovered about 50% of operators do not have policies in place to assess sufficient landing distances at time of arrival--even when runway conditions changed or had deteriorated from those forecast at departure. In addition, the FAA found that not all operators have procedures that account for runway surface conditions or reduced braking conditions. Thus the review led to the FAA's revised policy. Meanwhile, the NTSB continues its probe, and acting Chairman Mark V. Rosenker says he hopes the final Flight 1248 report will be completed by year-end or early next year. from this link |
DRY
More than 75% of the runway surface is dry or has insufficient moisture to
appear reflective.
WET-GOOD
More than 25% of the runway is covered with sufficient moisture to appear
reflective, but there are no significant areas of standing water. Treated
runways (i.e., grooved, etc.) should not be considered as having standing
water. Braking action is reported as GOOD.
WET-FAIR
More than 25% of the runway surface is covered with sufficient moisture to
appear reflective, but there are no significant areas of standing water. Treated runways (i.e., grooved, etc.) should not be considered as having standing water. Braking action is reported as FAIR.
WET-POOR
More than 25% of the runway surface is covered with sufficient moisture to
appear reflective, but there are no significant areas of standing water. Treated runways (i.e. grooved, etc.) should not be considered as having standing water. Braking action is reported as POOR.
Note: “WET” runway conditions cover distances for braking actions only.
THIN CLUTTER
More than 25% of the runway surface is covered with the following:
• 0.125 inch to 0.25 inch standing water or slush
• 0.125 inch up to and including 0.50 inch wet snow
• 0.75 inch up to and including 2 inches dry (loose) snow
0.50 IN CLUTTER
More than 25% of the runway surface is covered with the following:
• Greater than 0.25 inch up to and including 0.50 inch standing water or slush
• Greater than 0.50 inch up to and including 1.00 inch wet snow
• Greater than 2 inches up to and including 4 inches dry (loose) snow
MU Meter Scale—International Scale
The Tapley Meter, Bowmonk Meter, Saab Friction Tester, Runway Friction Tester, and the Skiddometer all have scales similar to the MU Meter and the numeric values may be used interchangeably.
.80 .70 .65 .60 NORMAL
.65 .60 .50 .40 GOOD
.50 .40 .35 .30 FAIR
.35 .30 .25 .20 POOR
.25 .20 .10 NIL
James Brake Decelerometer—DCM
DCM readings in the United States are calibrated in terms of deceleration
measured in feet per second squared. Maximum deceleration on the scale is 32 feet per second squared, the equivalent of one G.
26 24 22 21 EXCELLENT
21 20 18 16 14 GOOD
14 12 10 FAIR
10 8 7 POOR
7 6 4 NIL
Runway Friction Reports—Military RCR
Runway Condition Reading (RCR) values may be encountered at military
alternates or on CAM charters.
25_19 GOOD
18_13 FAIR/GOOD
12_6 POOR
5_2 NIL
| |||||||||
