Gopal From United States of America, joined Jun 1999, 115 posts, RR: 0 Posted (16 years 8 months 4 days 14 hours ago) and read 824 times:
Do aircraft have conventional brakes on their tires in addition to flaps on the wings that are extended during landing to increase drag? How is it possible to reverse a jet engine within seconds that is generating enough power to propel the plane at around 150 miles an hour duirng landing? Does not damage the engines. Also does the nose wheel of large airliners have a steering mechanism attached to them? I would appreciate any information on the above topics.
jkgo From , joined Dec 1969, posts, RR:
Reply 1, posted (16 years 8 months 4 days 13 hours ago) and read 824 times:
1) Aircraft have brakes on their tires. Most modern airliners have autobrakes. The pilots select the braking strength they want, depending on the runway length and surface conditions, then arm the system before landing. After touchdown, the brakes automatically come on and are cancelled only when the pilots take over manually. In airliners, pilots try not to use these too much at high speeds as they tend to overheat very quickly. So they use...
2) Thrust reversers. Almost all airliners have them nowadays. Most reversers can be deployed only upon touchdown. In most engines, huge clamshell doors pop out and back to cover the tailpipe. The engine is then revved up to 75% or thereabouts. The doors deflect the jetblast forwards. It takes a few seconds to deploy the reversers. Around 50 to 70 kts (depending on the aircraft's limitations), the engines are brought back to idle to prevent the reversers from blowing foreign objects into the front of the engine. When manufacturers come up with the aircraft's landing and aborted takeoff distances, reversers are not factored in. It's perfectly alright not to use reversers after landing. In fact, some airports do not allow their use for noise abatement considerations. Still, reversers can minimize brake and tire wear and provide that extra margin of safety. On wet runways, it can be the only means of deceleration available to a flight crew.
3) Airliners have nosewheel steering. This is operated by a wheel or tiller located along the cockpit sidewall. Some aircraft have a limited amount of steering available through the rudder pedals to help out on the takeoff roll or make minor adjustments during the long taxi out to the active. Nosewheel steering is automatically deactivated (but not on all planes) after reaching a certain speed--typically 60 kts.