What are spoilers used for on a plane, and when are they used?

There are two category uses of aircraft spoilers, Flight Spoilers and Ground Lift Dumping. It’s easy to figure out which one is used for in flight and which one is for on the ground.

Spoilers

Flight spoilers are merely designed to increase drag and reduce (or dump) lift. All modern airliners are designed to have the least amount of drag from the airframe to increase fuel efficiency and range. Modern jetliners typically have 2 to 8 spoiler panels per wing depending on the size of the jetliner.

Spoilers in flight have several uses to assist the pilot in controlling his/her airplane. When a pilot wants to slow down and/or descend quickly, that low drag design can be a hindrance to doing so. Flight Spoilers (Speed Brakes) give the pilot the ability to increase drag thereby allowing the pilot slow down and/or descend at a faster rate. In flight, the aircraft typically uses one or two spoiler panels per wing.

Another important use of Flight spoilers is roll control and controlling adverse yaw. Spoilers in combination with ailerons help the pilot smoothly control turns to make them more stable and comfortable.

Spoilers on the ground have one specific use, Lift Dumping for Landing roll and aborted takeoffs. The efficient design of an aircraft wing creates lift at all times the aircraft is moving through the air. The faster the plane moves forward, the greater the lift created. This lift, even when the airplane is not airborne, reduces the weight on the wheels. Again, the more lift being created, the less weight on the wheels during landing or takeoff.

This reduced amount of weight on wheels lowers the braking action or effectiveness of the wheel brakes and significantly increases the required length of runway to stop a heavy jet, (up to 200% more runway). Aircraft designers have designed Ground Spoilers for use when landing and aborting takeoff to dramatically reduce landing distance and directional control.

Thomas Zerbarini

GIF’s from: Spoilers: How 1 Control Helps You Descend, Stop And Roll

Do commercial pilots sometimes forget or not notice if autothrottle is on/off when it should be in the opposite state?

Thinking about Asiana flight 214, and anecdotal evidence of near misses on approach (stall) when autothrottle was believed to be active but was actually off, is it common to misunderstand the state of autothrottle, and is it easy to miss?

Answer by Thomas Zerbarini:

As you can see from your question in reference to the Asiana accident; yes it is possible for pilots to miss something. Although quite rare and unlikely it can happen. With improper training, distractions, complacency or other contributing factors errors are possible. That is why we train and re-train so much. It's why we have multiple pilots, checklists, flows, scans and many other mechanisms to establish checks-and-balances for safety.

Aviation Week did a good article summarizing the NTSB findings which included the main probable cause and the many contributing factors that caused the accident.

NTSB Calls For Special Review Of Boeing 777 Speed Control

With these findings in mind, we can emphasis how important it is for pilots to be diligent and monitor the aircrafts performance and flight path at all times even when the auto-pilot is engaged. Now, professional pilots know this and it is engrained in us. Yet, complacency can be insidious which makes monitoring each other in the cockpit is so important.

Here is an image of a Boeing 777 Cockpit:

At the very top on the glare shield panel in the center is the Mode Control Panel MCP (auto-pilot panel). It looks like this:

On the MCP you'll notice on the left side the A/T (auto-throttle) switch light. This switch light is green when the auto-throttles are engaged. If you read the Aviation Week article I provided above you'll notice that the A/T system was engaged, so the green switch light would be green (on) and if the pilot did a quick scan would see that they were on. Due to the design of the system though, the A/T's were in FLCH "hold mode" and the low speed automatic response was inhibited. Thereby allowing the aircraft speed to deteriorate to a dangerously low speed. The fact that the pilot(s) did not recognize the dangerous low speed nor respond quickly enough is what the NTSB has highlighted as the primary blame for the accident.

Here is a great interactive (click on switches) website that describes the functions of the various controls on the MCP panel:

777 Mode Control Panel ( MCP )

Thomas Zerbarini

Do commercial pilots sometimes forget or not notice if autothrottle is on/off when it should be in the opposite state?

Are airline pilots basically just good monitors?

Answer by Thomas Zerbarini:

Pilots need to be good monitors/managers of systems; yet, they need to be good aviators too.

The issue that comes to mind when this question is asked revolves around automation and flight automation and aircraft control philosophy.

The two major manfacturers of commercial aircraft (Boeing and Airbus) have completely different philosophy's when it comes to automation:

“Boeing flight decks are designed to provide automation to assist, but not replace, the flight crew member responsible for safe operation of the airplane.” — Boeing

“All aircraft have physical limits that they must not exceed... These limits define the flight envelope, not to be exceeded during normal operation.” —Airbus

Basically, Boeing allows a pilot full flight control authority to meet any need the pilot deems necessary to handle any emergency. Airbus places hard limits and will not allow the pilot to exceed any hard envelope.

Here's an article for a good overview of the philosophy differences between the two manufactures: 

http://www.aerospaceamerica.org/...

I personally agree with the Boeing philosophy and find that there seems to be issues lately with too much automation. When humans rely on too much automation, there is the possibility for complacency. When automation does something unexpected or misunderstood by the pilots; and, when the other pilot does something unexpected or unknown by the other pilot (AF 447, no side stick feedback.) 

Automation Has Made Airline Travel Safer. But Are Pilots Too Dependent on It? 

Or the new Airbus A350 that embarrassingly self aborted on a media flight from JFK to Dubai. 

Qatar Airways flight comes to a halt in aborted JFK takeoff 

And of course the Boeing 777 crash in San Fransisco where the pilots relied on automation to control their speed and did not realize the auto-throttles were off.

http://www.ntsb.gov/news/events/...

Here is a more complete bullet list of each manufacturers philosophy. I included McDonald Douglas from the 80's even though it is now merged with Boeing.

Airbus' Philosophy on Automation

• Automation must not reduce overall aircraft reliability; it should enhance aircraft and systems safety, efficiency and economy.
• Automation must not lead the aircraft out of the safe flight envelope to its full extent, should this be necessary due to extraordinary circumstances.
• Automation should allow the operator to use the safe flight envelope to its full extent, should this be necessary due to extraordinary circumstances.
• Within the normal flight envelope, the automation must not work against operator inputs, except when absolutely necessary for safety.

Boeing's Flight Deck Automation Philosophy

• The pilot is the final authority for the operation of the airplane.
• Both crew members are ultimately responsible for the safe conduct of the flight.
• Flight crew tasks, in order of priority, are: safety, passenger comfort, and efficiency.
• Design for crew operations based on pilot's past training and operational experience.
• Design systems to be error tolerant.
• The hierarchy of design alternatives is: simplicity, redundancy, and automation.
• Apply automation as a tool to aid, not replace, the pilot.
• Address fundamental human strengths, limitations, and individual differences-for both normal and non-normal operations.
• Use new technologies and functional capabilities only when:
• They result in clear and distinct operational or efficiency advantages, and
• There is no adverse effect to the human-machine interface.

McDonnell-Douglas

• Uses technology to assist the pilot naturally, while giving the pilot the final authority to override the computer and use skill and experience.

Thomas Zerebarini

Are airline pilots basically just good monitors?

What do all of the controls in an eurofighter typhoon cockpit do?

Answer by Thomas Zerbarini:

I love answering these questions. Most of what you'll find is centered around flying the airplane and monitoring systems. The rest will be defensive and offensive instrumentation and/or special operations and recording devices for reconnaissance.

Check out this fantastic website that lists all the items in the cockpit with pictures and explanations:

Functionality EF-2000

Thomas Zerbarini

What do all of the controls in an eurofighter typhoon cockpit do?

What is the most maneuverable aircraft in the world?

Answer by Thomas Zerbarini:

When we talk about maneuverability in an aircraft you have to consider that an aircraft is more maneuverable the more its aerodynamics are "unstable." The aircraft I would say was the most maneuverable would be the experimental Grumman X-29 flown by NASA:

This unusual looking aircraft that appeared to seem it was flying backwards was so unstable that it required a triple redundant Fly-by-wire (Fly by Wire: Fact versus Science Fiction) flight control system to provide "artificial" stability and keep the aircraft from spinning out of control. The cockpit was simple yet the aircraft was ahead of its time.

The aircrafts instability was inherent in turning the wing backwards. The aircraft wanted to pitch, roll and dutch roll violently if not actively controlled by the triple redundant fly-by-wire systems with an analog back-up.

I'm certain that the variable exhaust nozzles, being used in our most advanced fighters today, if placed on an forward swept design like the X-29 would have dazzled NASA and the Pentagon on the extreme maneuverability of such a concept.

You'll have to consider that todays designs are larger demand multi-role tactical fighters that are bigger, use stealth technology an

d would have a tendency to be more lumbering in a dogfight than say the F-16 or a design like the X-29.

In an effort to save money, congress tends to like the multi-role fighter platform. Such a platform depends more on technology, missiles and radar to defeat a foe and the aircraft tend to be larger and more lumbering.
This idea has happened in the past with other aircraft like the F-4 Phantom. A huge powerful aircraft that was too big to effectively dogfight with lighter more maneuverable fighter jets. We may again see another aircraft surface that is light and nimble to truly replace the F-16.

Thomas Zerbarini

What is the most maneuverable aircraft in the world?

Why is the framework in the cockpits of Russian aircraft painted blue?

Answer by Thomas Zerbarini:

The Russians did a lot of research in the 1950's on this and found that the turquoise color would assist crews in staying alert and calm, especially during high stress situations. You'll also find that McDonnell Douglas also used this color in their cockpits on the DC-7:

DC-9:

Thomas Zerbarini

Why is the framework in the cockpits of Russian aircraft painted blue?