Sudden From Sweden, joined Jul 2001, 4169 posts, RR: 5 Posted (13 years 7 months 2 weeks 6 days 7 hours ago) and read 4902 times:
My question about this system goes back to when I worked at GOT airport.
It was winter and the ramp was very slippery. We were standing waiting for our KLM flight (737-400), and when they came on to the ramp, and was about to make a right turn on to the gate, the A/C just kept on going straight. What you might call a "overshoot".
The A/C came to a stop, and the pilot just stepped on it and made a 180 and blocked at the gate.
The pilot was taxiing way to fast for the conditions that occurred on the ramp.
my question is basically if this system also works as a ABS system on newer A/C's? To prevent skidding like the above mentioned incident.
Also, what speed is required for the Anti Skid system to get activated?
OPNLguy From , joined Dec 1969, posts, RR:
Reply 3, posted (13 years 7 months 2 weeks 6 days 1 hour ago) and read 4834 times:
>>>Ok, my question is basically if this system also works as a ABS system on newer A/C's? To prevent skidding like the above mentioned incident.
Anti-skid systems have been around on aircraft for years, and automotive ABS are the more recent offshoot.
The main task of the anti-skid system isn't prevent slow speed ramp skids like you the situation you decsribed. The purpose of the anti-skid system is to greatly increasing braking effectiveness, primarily on landing, but also on takeoff should it be aborteed...
Cdfmxtech From United States of America, joined Jul 2000, 1341 posts, RR: 25
Reply 4, posted (13 years 7 months 2 weeks 6 days ago) and read 4824 times:
First of all, are you sure he skidded??
I don't think the B737-3/4/500 have a minimum skid control speed. That doesn't mean that the aircraft will never be able to stop. As long as there is no skid condition, then things will be OK. Also, the B737-3/4/5s have antikid control switches as it CAN be selected OFF. When we taxi the 37s, our checklist has us turn off antiskid. I think with the aircraft being so light during a mx taxi, it would skid easily if brakes not applied correctly.
I have to research some other things about the classic, but I couldn't find a minimum speed anywhere. The NGs, B757 and 67 are approx 8 knots. BTW, there is no ON OFF siwtch for those aircraft.
B747skipper From , joined Dec 1969, posts, RR:
Reply 5, posted (13 years 7 months 2 weeks 5 days 22 hours ago) and read 4793 times:
In the old "Classic" 747s, the antiskid switch stays "ON" at all times, including taxi speed... it is deactivated automatically at low speeds... some "nervous" pilots (or old habits they took with previous airplanes they flew) sometimes like to "disarm" the antiskid for taxi...
It is NOT on the Boeing's check lists and SOP... but... OK...
Airplay From , joined Dec 1969, posts, RR:
Reply 6, posted (13 years 7 months 2 weeks 5 days 1 hour ago) and read 4725 times:
About a month ago while I was waiting in Toronto for a flight, I witnessed a towing incident with an A340.
The tug was pulling the airplane too fast, and when he tried to make a turn, the airplane didn't agree. The tug jacknifed and ended up under the airplane aft of the nose gear. I have pictures if anyone is interested.
What we learn from this, is that a large airplane has alot of momentum and if the nose wheel loses traction or the tug doesn't have a similar amount of momentum, the airplane will continue on it's trajectory no matter which way the nose wheel is turned.
B747skipper From , joined Dec 1969, posts, RR:
Reply 9, posted (13 years 7 months 2 weeks 2 days 22 hours ago) and read 4603 times:
Dear Cdfmxtech -
Well when we write facts here - we (all) should be a little more specific, as many quote us with statements that are construed "erroneous"...
When a say "Boeing" check list, I mean the check lists from Boeing's own QRH, which are generally used by foreign airlines - in the USA, each airline have a tendency to make "their own" check lists (because they know the airplane better than Mr. Boeing himself)...
I remember the check lists (Boeing's or airline specific) from the 707 and 727, and yes indeed, the "anti-skid" switch was OFF for taxi... see their check lists... But on the 747 classic, the anti-skid switch gathers dust, it is left ON and CAPPED at all times, and not part of the Boeing QRH before taxi or takeoff check lists... my airline recognized that they are not 747 experts, and they trust Boeing's own designed standard procedures, as is, out of the Boeing book...
Those of our technicians and ground engineers who are "taxi qualified" are required to use the very same QRH used by flight crews, when they position the aircraft around the airport...
I personally dont like pilots to "make their own procedures" - even if they mean to "improve" safety... i.e. ex-737 pilots have a habit to prefer the anti-skid OFF for taxi operations in the 747... As it is not on the check list, WHAT IF they forget it for takeoff, since it is NOT on the check list... Let us stick to our SOPs, as defined by our operations, for the sake of safety...