Aero-News has received
a copy of a recently published safety notice issued by the
Southwest Airline Pilots Association (SWAPA). In direct response to
concerns raised by SWA's tragic December MDW over-run, SWAPA has
clarified and issued the following report. ANN confirmed the
authenticity of the document with SWAPA members, who were "not
surprised" that it was being disseminated so quickly. The document
is attached below without editing, though contact names and email
addresses were redacted for privacy's sake -- Jim Campbell, ANN
E-I-C
Subject: WINTER WEATHER OPS Safety Alert 2006-01
From the Southwest Airline Pilots Association (SWAPA)
January 23, 2006
WINTER WEATHER OPS Safety Alert 2006-01
Although there is very little that can be discussed concerning
the MDW Flt. 1248 accident of Dec. 8, 2005, there are some facts
that have come to light that need to be highlighted as at least
three months of winter remain.
There is a distinct difference in how the OPC computes landing and
RTO performance for the classic fleet of Boeing 737's and the NG
-700 aircraft. The classic OPC does not utilize any reverse thrust
credit while calculating the stopping margin; this is in line with
the certification procedure for the aircraft. The NG aircraft OPC's
however use Boeing proprietary software that factors in the use of
reverse thrust for these same calculations, which in our estimation
does not give you, the operator, a realistic margin of safety when
interpreting how much stopping margin is actually available.
Obviously SWAPA is not in the position, nor do we have the
authority to dictate operational procedures for Southwest Airlines,
but in our opinion it would seem wise to review the -700 OPC data
and when the runway is short, contaminated, or braking action
reports are less than good, that you give consideration to
programming the OPC to MEL the thrust reversers and note the
difference in stopping margin. This applies to both landing
performance and RTO performance; make the landing or departure
decision accordingly.
Braking action reports
and runway friction reports very often do not correlate. The
braking action reports are subjective and not only is the MU
interpretation subjective, the MU value does not translate to any
braking action value. One can find a poor braking report followed
by a MU value that ranks as the lower end of GOOD, so be very
careful when relying upon the combination of both. All Part 25
certificated aircraft have their landing performance derived from
dry, uncontaminated runway performance data that then has various
equations applied. The formula for these equations appears to have
come from a 1961 Convair 880 test that was conducted by the
FAA.
The point in explaining this is that when your stopping margin
begins to get a little thin it would be a good time to review all
of your options as the data that you are utilizing may not actually
reflect the true stopping distance required. If in fact what we are
discovering is true, then the equations that were developed
were developed from a first generation swept wing pure
turbojet transport. The adaptation to the current NG B-737 may not
be as accurate as we have thought.
Boeing has provided us a very good aircraft to
operate and one that has a great record. As pilots, we often take
the performance values for granted; in most conditions that is a
safe and wise decision. While operating in winter weather
conditions, heavy aircraft, short runways, etc., give extra
consideration to your dispatch release, the fuel on board, the
runway condition, possible tailwind component, and how closely your
aircraft might be to its operating limit and safety margin for that
particular approach or departure.
We operate from some relatively short runways in some cities to fly
long distances and the RTO stopping margin can be a factor. ISP
comes to mind where we routinely use RWY 33L which is only 5186
feet long. A -700 in excess of 130,000 pounds will not have much in
the way of RTO stopping margin departing that runway. Using the
same example, a 125,000-pound -700 will not have much stopping
margin while landing on that runway. Consider less tanker fuel
coming in and utilizing RWY 6/24 as opposed to the often advertised
15/33. ISP in particular causes us concern as it is a high use
General Aviation airport and the ATIS and active runway are often
tailored to that spectrum of aviation as opposed to Part 25
aircraft that could have a greater safety margin by utilizing a
longer runway. Just because the 15R/33L runway is being advertised
does not mean that you have to use it.
Examine the OPC for all
runways and choose the stopping margin that gives you the better
safety cushion. This thought process applies to MDW as well.
Historically, the active runway at MDW is predicated upon ORD
landing flows. If RWY 13C is better suited for your arrival
then make the request if it makes sense. MDW ATC can provide you
with that runway if asked and given the reason why. Take this type
of thought process and apply it to any airport that you might be
operating to or from and make the decisions that you need to make
accordingly. As always, the captain is the final authority on the
safe operation of the aircraft.
Another issue that has come to light is the periodic difficulty in
actuating reverse thrust in the -700 aircraft. Through testing we
have found that the slightest forward movement of the Thrust Levers
will mechanically keep the Thrust Reverser Levers from unlocking.
It is very important that the Thrust Levers be flat against the
Idle Stop before attempting to actuate the Thrust Reversers. If you
experience any difficulty in actuating the Thrust Reversers, assure
that the Thrust Levers are physically flat against the Idle Stop
and re-attempt. If the problem persists, then make a logbook entry
and have maintenance examine the system.
-SWAPA Air Safety Committee
Jeff Hefner, Chair SWAPA Air Safety
Steve Swauger SWAPA Air Safety
John Gadzinski Go Team Operations SWAPA Air
Safety