India First week of monsoon
I landed in BOM a couple of days ago and the runway seemed to be a bit grippier than I remember - has it been resurfaced? Anyway, I can confirm there was a lot of water about, three aircraft went around due w/s.
I think the proviso rarely applies, as from my experience, the worse the braking action, the more variability there is. Water/slush/snow/ice is rarely evenly distributed and you’ve likely got areas of rubber deposits around the TDZ at either end.
Autobrakes generally go for a fixed deceleration rate on anything but MAX, where they function like the ABS on a car with your foot hard on the brake: they extract the maximum stopping performance available at that instant. Consider a runway where the braking action of 50% of the surface (not necessarily in one bit) is worse than reported and 50% is better - using MAX will get more stopping in the good bits and the same in the bad bits, so a net win over an AB setting that technically should give the same result but may surprise you on the day.
Downsides of using MAX AB? Err, maybe a little bit more brake wear? Downsides of going off the end...
I think the proviso rarely applies, as from my experience, the worse the braking action, the more variability there is. Water/slush/snow/ice is rarely evenly distributed and you’ve likely got areas of rubber deposits around the TDZ at either end.
Autobrakes generally go for a fixed deceleration rate on anything but MAX, where they function like the ABS on a car with your foot hard on the brake: they extract the maximum stopping performance available at that instant. Consider a runway where the braking action of 50% of the surface (not necessarily in one bit) is worse than reported and 50% is better - using MAX will get more stopping in the good bits and the same in the bad bits, so a net win over an AB setting that technically should give the same result but may surprise you on the day.
Downsides of using MAX AB? Err, maybe a little bit more brake wear? Downsides of going off the end...
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Really guys, you don’t know that different aircraft have different systems that work in different ways?
The NG has AB 1-2-3-Max for landing, RTO for takeoff.
Max can be used whenever it’s needed. Did that recently on a 1600 m runway and 63 T for landing. It uses a fixed retardation so more reverse give less brakes.
RTO is the full monty.
Landing runway 14 in BOM on a wet runway and 60+ tons LW you’ll be stupid not to use max.
The NG has AB 1-2-3-Max for landing, RTO for takeoff.
Max can be used whenever it’s needed. Did that recently on a 1600 m runway and 63 T for landing. It uses a fixed retardation so more reverse give less brakes.
RTO is the full monty.
Landing runway 14 in BOM on a wet runway and 60+ tons LW you’ll be stupid not to use max.
It was fitted to our DC 10 as a mod. Crews were informed by a memo from the fleet TP, with recommendation to use light or medium but not full, until experience was gained and a feedback form had to be completed each time.
Next scene - pre landing in HKG dry RW and quite light - FE says Autobrake? Capt on check says Oh - er Better use light - Check Pilot says Try Full - FE says I have to fill a form and it says Reason for use - Check Pilot says Put Inquisitiveness.
The landing - Touch down followed by the most brutal retardation I have ever experienced before or since - talk about being thrown against the harness - IAS falls like a stone - Check Pilot shouts Disconnect - Captain on check shouts How? I (probably the only one who had read the memo) say, Brakes. Captain brakes and the ship feels as though released from a bow. We are now at about 30 knots and have to use Fwd thrust to reach the first exit...
Taxy in with red faces, left side anyway and hot brakes - Capt makes an announcement about a new bit of kit - not working properly, sorry etc.
All good useful experience for the first officer.
Next scene - pre landing in HKG dry RW and quite light - FE says Autobrake? Capt on check says Oh - er Better use light - Check Pilot says Try Full - FE says I have to fill a form and it says Reason for use - Check Pilot says Put Inquisitiveness.
The landing - Touch down followed by the most brutal retardation I have ever experienced before or since - talk about being thrown against the harness - IAS falls like a stone - Check Pilot shouts Disconnect - Captain on check shouts How? I (probably the only one who had read the memo) say, Brakes. Captain brakes and the ship feels as though released from a bow. We are now at about 30 knots and have to use Fwd thrust to reach the first exit...
Taxy in with red faces, left side anyway and hot brakes - Capt makes an announcement about a new bit of kit - not working properly, sorry etc.
All good useful experience for the first officer.
Last edited by bill fly; 6th Jul 2019 at 05:35.
