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By: Frances Fiorino
06/25/2006 08:50:11 PM
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.
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.
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
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
| || The following are definitions of runway conditions
used by the OPC:|
More than 75% of the runway surface is dry
or has insufficient moisture to
than 25% of the runway is covered with sufficient moisture to appear
but there are no significant areas of standing water. Treated
grooved, etc.) should not be considered as having standing
action is reported as GOOD.
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
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.
runway conditions cover distances for braking actions only.
More than 25% of the runway surface is covered with the following:
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
• 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
• 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
.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
20 18 16 14 GOOD
14 12 10 FAIR
10 8 7 POOR
7 6 4 NIL
Friction Reports—Military RCR
Runway Condition Reading (RCR) values may be
encountered at military
alternates or on CAM charters.