Flight Training - August 2012 - 52

CAREER PILOT»

TECH TALK

Do you have the power?
» By Jared Dirkmaat

STOP!

AIRPLANES ARE PRETTY good at going fast. Even a Cessna 172 can fly at 110 knots, which may not sound like much, but when was the last time you drove your car at 120 mph? Scale that speed up to larger aircraft, and now you’re cruising in the 400- to 500-knot range. That speed means you can get from point A to point B quickly, but what does it mean when it’s time to stop? In the same way that aircraft are designed for speed with aerodynamic designs and high-performance engines, they’re also designed for stopping power. Utilizing a combination of thrust reversers, ground spoilers, and anti-skid braking systems, large and heavy aircraft can be slowed to a stop in much shorter distances than without the combined technology. Thrust reversers work by redirecting the exhaust gases from the aft of the engine by channeling them forward. This creates an equal-and-opposite reaction from the force directed forward, and decelerates the aircraft. Generally these systems incorporate hydraulic actuation with electrical operation; by utilizing multiple systems to operate and actuate the reversers an inadvertent deployment can be avoided. Some aircraft are designed to be capable of in-flight deployment of the reversers; however, most aircraft today require the aircraft to be on the ground. Ground spoilers often are combined with a flight spoiler system that can be used during all phases of flight. Some aircraft even utilize the flight spoiler system

to assist in roll control during low speed flight. Most aircraft are equipped with technology that knows when the aircraft is on the ground and the wheel speed of the main landing gear. While on the ground and above a specified wheel speed, the ground spoilers will automatically deploy if they’re properly armed. This spoils the airflow over the wing, creating drag and also applying downforce to the main landing gear, improving braking effectiveness. The final element to creating all of this stopping power are the brakes. Hydraulic actuation of the brakes reduces pedal forces required by the pilot to create a desired amount of braking. This is accomplished through the assistance of a Brake Control Unit which receives inputs from the brake pedals through a position transducer that interprets the braking commands. These commands are then carried out by applying or relieving the required hydraulic pressure for either differential brake. Anti-skid is accomplished by monitoring of wheel speed and hydraulic pressure sensors by the Brake Control Unit. Should the wheel speed on one main wheel differ from the other, hydraulic pressure is automatically relieved. This helps prevent un-commanded asymmetrical braking, but it also prevents skids by not allowing the wheel to lock up. Combine these technologies and the aircraft becomes capable of shorter, safer, more effective deceleration when it most counts: landings and rejected takeoffs.

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Flight Training - August 2012

Table of Contents for the Digital Edition of Flight Training - August 2012

Flight Training - August 2012
Contents
President’s Perspective
Right Seat
Letters
Something to See
How It Works
After the Checkride
Tech Tip
News
Final Exam
AOPA Action News
Since You Asked
Success Story News
Member Products
Training Products
ASI News
Flying Carpet
FOLLOW THE MAGENTA LINE
TIME TO CHILL
GETTING WET
TECHNIQUE
Weather
Accident Report
Flight Lesson
Perfect Storm for Pilot Shortage
Career Advisor
Tech Talk
Flight Instructors in the Hot Seat
Good Times for CFIs
Crossed Up
Advertiser Index
Debrief
Flight Training - August 2012 - Flight Training - August 2012
Flight Training - August 2012 - Cover2
Flight Training - August 2012 - Contents
Flight Training - August 2012 - 2
Flight Training - August 2012 - 3
Flight Training - August 2012 - President’s Perspective
Flight Training - August 2012 - 5
Flight Training - August 2012 - Right Seat
Flight Training - August 2012 - 7
Flight Training - August 2012 - Letters
Flight Training - August 2012 - 9
Flight Training - August 2012 - Something to See
Flight Training - August 2012 - 11
Flight Training - August 2012 - How It Works
Flight Training - August 2012 - After the Checkride
Flight Training - August 2012 - Tech Tip
Flight Training - August 2012 - News
Flight Training - August 2012 - Final Exam
Flight Training - August 2012 - AOPA Action News
Flight Training - August 2012 - Since You Asked
Flight Training - August 2012 - 19
Flight Training - August 2012 - Success Story News
Flight Training - August 2012 - Member Products
Flight Training - August 2012 - Training Products
Flight Training - August 2012 - ASI News
Flight Training - August 2012 - Flying Carpet
Flight Training - August 2012 - 25
Flight Training - August 2012 - 26
Flight Training - August 2012 - 27
Flight Training - August 2012 - FOLLOW THE MAGENTA LINE
Flight Training - August 2012 - 29
Flight Training - August 2012 - 30
Flight Training - August 2012 - 31
Flight Training - August 2012 - 32
Flight Training - August 2012 - 33
Flight Training - August 2012 - TIME TO CHILL
Flight Training - August 2012 - 35
Flight Training - August 2012 - 36
Flight Training - August 2012 - 37
Flight Training - August 2012 - GETTING WET
Flight Training - August 2012 - 39
Flight Training - August 2012 - 40
Flight Training - August 2012 - 41
Flight Training - August 2012 - TECHNIQUE
Flight Training - August 2012 - 43
Flight Training - August 2012 - Weather
Flight Training - August 2012 - 45
Flight Training - August 2012 - 46
Flight Training - August 2012 - Accident Report
Flight Training - August 2012 - Flight Lesson
Flight Training - August 2012 - Perfect Storm for Pilot Shortage
Flight Training - August 2012 - Career Advisor
Flight Training - August 2012 - 51
Flight Training - August 2012 - Tech Talk
Flight Training - August 2012 - Flight Instructors in the Hot Seat
Flight Training - August 2012 - Good Times for CFIs
Flight Training - August 2012 - Crossed Up
Flight Training - August 2012 - 56
Flight Training - August 2012 - Advertiser Index
Flight Training - August 2012 - 58
Flight Training - August 2012 - 59
Flight Training - August 2012 - 60
Flight Training - August 2012 - 61
Flight Training - August 2012 - 62
Flight Training - August 2012 - 63
Flight Training - August 2012 - 64
Flight Training - August 2012 - 65
Flight Training - August 2012 - 66
Flight Training - August 2012 - 67
Flight Training - August 2012 - 68
Flight Training - August 2012 - 69
Flight Training - August 2012 - 70
Flight Training - August 2012 - 71
Flight Training - August 2012 - Debrief
Flight Training - August 2012 - Cover3
Flight Training - August 2012 - Cover4
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