Operations Training Division,
Santa Cruz (East)
MUMBAI- 400 029
September 29, 2005
To:
ALLFLIGHTCREW
Recently, one of our B747-400 aircraft was involved in a runway overrun incident after landing during a heavy shower on runway 14 at Mumbai. There was no damage to the aircraft and no injuries to
the passengers or crew. However, to highlight the problems faced during landing in adverse weather compounded with wet / slippery runway conditions this circular is being issued
The information will subsequently be incorporated in the Operations Manual/SOP.
BrakingAction is reported as "Good", "Medium" or "Poor" after analyzing the readings of friction measuring devices such as DBV(Diagonal Brake Vehicle), ASFT(Airport Surface Friction Tester).
The British Mu meter and the "Griptester" trailer, etc. To increase friction, runway treatment is carried out. It is simply removal of rubber deposits by chemical or water blast techniques, or mechanical scrubbing.
Anywater on a runway creates a potential slippery situation and should be treated with caution.
Cross-wind/ tailwind components add to the threat.
When runway is wet or contaminated, calculate the landing distance required including the factored distances for components unserviceable, ego Thrust reversers, spoilers, etc. If landing distance required is marginal, compared with landing distance available, then consider diversion.
Determination of Landing Distance
For Boeing aeroplanes:
Tables are provided in the QRHfor DRYRunway and Slippery Runway with Braking action as Good, Medium and Poor. When the Runway is wet, the slippery runway table with "good" braking action is to be entered. However, if the braking action is reported as Medium then the 'Medium' table is used. In case of runway contaminated with water with no reports of braking action use Braking action "Medium". However, if the reported braking action is "poor" consider diversion except when there is no option. If diversion is not possible, then the "poor" table must be referred to.
For Airbus aeroplanes:
Acutallanding distances are given in the QRH for Dry, wet, 6.3 mm water, 12.7 mm water, 6.3 mm slush, 12.7 mm slush, compacted snow, and ice.
2
Landing Geometry:
The tables in the QRHgive the actual landing distance from the threshold assuming approximately 1000 feet of air distance, which is included in the tabulated distance. It is being emphasized that this caters to only 4 secs of flare to touchdown from the 30 feet point. However, the average flare
time ranges from 6 secs to 8 secs and therefore, it would be prudent to add another 1000 feet to the distance extracted from the table to give a more realistic landing distance. The landing distance is the distance from the landing threshold and not from "beyond glide
slope". It is emphasized that this is the actual distance covered by the aircraft from the threshold including the
air (float) distance and does not include the Regulatory (FAA) 60%additional margin. When reported braking action is medium or braking action in the pilots' judgement is medium or
when the R/W is soaked with water, use Auto brakes as stated below :-
'Max' (B747-200/300)
'Max Auto' (B747-400
&: B777)
'Medium' (A-310)
In all cases monitor the deceleration rate. If it is observed to be less than the required rate of deceleration, then use maximum manual braking (i.e. full brake pedal deflection) which gives the highest deceleration ra,te.
Further emphasis should be placed upon the following :-
• Select appropriate auto-brake as per SOP.
• Approach on glide path at the correct approach speed.
• Avoid extended flare and ensure a firm touch down.
• Use maximum reverse thrust as soon as possible.
• Confirm extension of ground spoilers.
• Do not delay lowering nose-wheel onto the runway. This increases weight on wheels and activates aircraft systems associated with nose gear squat switches! proximity detectors.
• Monitor auto-brakes or apply pedal brakes with continuous steady pressure. Do not pump brakes or apply then release and reapply. The Anti-skid will regulate the braking most effectively if continuous pressure is maintained.
• For directional control use rudder pedals and differential braking. Do not use nose wheel steering tiller.
• At taxi speed use nose wheel steering with care.
Finally, it is being emphasized that at any point during final approach it is felt that adequate landing distance may not be available due to changed circumstances or weather, there should be no hesitation in executing a missed approach. Abrief write-up on Runway conditions and Hydroplaning is enclosed for information.
( CAPT.S.C. BAPTISTA )
GENERAL MANAGER-OPS (TRG)