ILS — Instrument Landing System

ILS — Instrument Landing System

The instrument landing system (ILS) is a ground-based system that guides aircraft to safe landings during periods of low visibility or poor weather. It guides the pilot down an imaginary ramp at a shallow 3-degree angle that leads to the touchdown zone of the runway surface.

ILS works by broadcasting a narrow beam of encoded radio energy that's picked up by a special radio receiver in the aircraft. A cockpit display then shows the pilot his position and displacement relative to the guidance beam (left, right, above, below). The pilot follows this beam toward the runway until "breaking out" of the clouds to complete the landing visually. Bright lights help provide visual guidance to touchdown.

Transponders

Transponders

The Federal Aviation Administration (FAA) uses radar to monitor the position and flow of aircraft in flight. When the radar beam sweeps across an aircraft, some of that radio energy is reflected back to the radar installation. But the reflection is often relatively weak and contains no altitude information.

To help improve the "visibility" of aircraft as radar targets, aircraft are equipped with little boxes called transponders. The transponder detects the radar sweep, and in response, generates its own very powerful return pulse. This 200-watt pulse makes the aircraft much easier to see on radar.

Aircraft operating near major cities, at high altitudes, and in some types of airspace, are required to use altitude encoding transponders. The transponder is connected to a little electronic device on board the aircraft that measures the aircraft's altitude. The transponder encodes the altitude data into the return pulse that it broadcasts to air traffic control. ATC uses the altitude data to help separate different aircraft from each other. Other airplanes with traffic alert and collision avoidance systems (TCAS) can see and use the altitude data. These transponders must be checked for accuracy every 24 months.

When air traffic controllers want to distinguish one airplane from another, they will temporarily assign the pilot a unique four-digit transponder code (some codes are reserved for special purposes).

Once the pilot has set the transponder to the specified code (called "squawking" i.e., squawk 4367), ATC's radar display will then isolate the target aircraft from all the rest. This allows the controller to assign the aircraft's registration number (it's N-number) or flight number to the individual blip on the radar screen.

The information assigned to the radar blip is called a data block. The data block follows the airplane through the ATC system as it's handed from one controller to the next throughout its flight.

GPS — WAAS

GPS — WAAS

The Wide Area Augmentation System (WAAS) is a special system that supplements the space-based satellite signals of the primary GPS constellation. WAAS improves the accuracy of GPS for specially equipped aircraft to a few feet, versus tens of feet, allowing the use of GPS for precision approaches all the way down to a runway's surface. WAAS corrects for GPS signal errors caused by ionospheric disturbances, timing errors, and satellite orbit errors. It also provides integrity information regarding the health of each GPS satellite.

GPS — Global Positioning System

GPS — Global Positioning System

GPS is the future of all aerial navigation in the United States. This widely acclaimed space-based navigational technology was developed and is now operated by the U.S. Air Force. In the future, it will replace virtually all of the old land-based navigational technologies, giving pilots a more accurate, reliable, trustworthy, and lower-cost navigation system while saving taxpayers millions of dollars in annual costs. It's now used by millions of people in various walks of life.

Today, many VFR pilots use handheld GPS navigational units with color or black and white moving map displays. These handheld GPS receivers cost anywhere from $500 to $1,800 and can guide pilots safely through their flights in visual flight rules (VFR) conditions. An updated "Nav Database" with information about airports and airspace can be loaded into these units every 28 days, although most handheld units are only updated by their owners once each year.

Pilots wishing to use GPS to navigate in instrument (IFR) conditions like rain, snow, heavy haze, or low clouds, must use special IFR GPS receivers that are approved by the Federal Aviation Administration and are capable of recalling FAA-designed instrument flight procedures.

These IFR-approved GPS units must be permanently installed in the aircraft and must be capable of self-monitoring their own health or integrity, as well as the integrity of the GPS satellite signals.

The use of GPS for IFR flights requires that a current "Nav Database" of information about airports, airspace, and instrument procedures be loaded into these units every 28 days.

ASOS AND AWOS

ASOS AND AWOS
Technology has brought an enormous increase in the amount of information—especially weather information—at a pilot's fingertips. During the preflight briefing, you can study conditions at multiple reporting points, thanks to automated surface observation systems (ASOSs) and automated weather observation systems (AWOSs) at many airports. And those same systems are there to help you plan your arrival at many destinations. Include monitoring the station's report on your list of arrival duties before you contact the tower or request an airport advisory at nontowered airports.

"Each ASOS is equipped to transmit weather via voice or computer through telephone or on VHF radio frequencies," Use the Safety Advisor to learn the different service levels of the various ASOS installations—and consider the circumstances under which the information provided is susceptible to inaccuracy or error. You'll also see an explanation of the differences between ASOS and AWOS installations. ASOS is more sophisticated, uses more computer processing, and has better quality control. Note that if a component of an ASOS's weather reporting capabilities is not operating, a code to that effect will appear in its published METAR. For instance, the code TSNO indicates that thunderstorm information is not available—definitely worth knowing during your preflight briefing.

Want to start watching weather trends at a possible destination, or just curious about what's happening at your home airport? Visit this FAA's ASOS Web page to check conditions.

With ASOS information so easily obtainable in a preflight weather briefing by telephone or computer, and from the air by radio, there's no reason not to acquire the most timely reports, then update as you near your destination [see your VFR aeronautical chart, AOPA's Airport Directory, or the Airport/Facility Directory for the correct frequency].

SHARING YOUR AIRSPACE

You have learned the correct method for safely entering the traffic pattern at nontowered airports, and you've studied right-of-way rules that keep different categories of aircraft safely separate. (See the May 2, 2003, "Training Tips" on right-of-way rules.) Now you're ready to put these concepts to the test as you endeavor to operate safely in the presence of other airport users.

After you check airport publications for your destinations' radio frequencies, runway lengths and bearings, and facilities, be sure to look up what other kinds of air traffic might be present. "To airplane pilots, the ways of helicopters, gliders, and balloons seem mysterious. Knowing how they come and go helps you to coordinate your departures and arrivals with theirs. Being familiar with their operation is comforting when you scan for traffic because you know where to look for them.

Towplanes and gliders may use only the runway that is closest to the glider operation's base; you may need to use another because of reported surface winds. Large airplanes may use only the longer runways and fly a higher traffic pattern. Parachute jumping could be under way; what frequency is used to advise local aircraft about "jumpers away"? Helicopter pilots are responsible for avoiding the flow of fixed-wing aircraft, but keep an eye out for them in the pattern and while taxiing. Instrument approaches flown for practice by pilots training for the instrument rating could be in progress. These aircraft train with different arrival routes than aircraft making routine arrivals under visual flight rules. Ask your instructor to describe instrument training that could be in progress and what to listen for on the common traffic advisory frequency (CTAF). If there is a floatplane base on an adjacent body of water such as a river or lake, visualize its traffic pattern. Does the seaplane base use the same CTAF as the airport?

Experience will make these other kinds of aviation activity more familiar. Meanwhile, do your research and ask questions to fill in the gaps.

FLAPS: WHEN AND WHY

Most student pilots train in aircraft equipped with flaps. In the traffic pattern, the flaps are typically deployed gradually, starting abeam the runway numbers and ending with full deployment on final approach. Many students ask: Why not deploy the flaps all at once?

"Large flap deflections at one single point in the landing pattern produce large lift changes that require significant pitch and power changes in order to maintain airspeed and descent angle. Consequently, the deflection of flaps at certain points in the landing pattern has definite advantages. Incremental deflection of flaps on downwind, base leg, and final approach allow smaller adjustment of pitch and power compared to extension of full flaps all at one time," explains Chapter 8 of the Airplane Flying Handbook.

"When teaching landings in a Cessna or Piper training aircraft, I have the student use one notch of flaps and trim when abeam the numbers. From here, the remaining flaps are used to adjust the aircraft's descent to the touchdown point. If the pattern is a normal-sized pattern (the turn from base to final will be slightly more than a quarter-mile from the runway), and the headwinds on final are light, the second notch of flaps will be applied when they are needed to keep from landing long. This typically occurs just before turning from base to final. The third and last notch of flaps is applied when the landing is assured."

But don't let that comfortable routine make you complacent. Unusual winds, extending your downwind leg for spacing, or getting instructions from the tower to "make short approach" may call for other techniques (and don't forget to perform some no-flap landings).

During dual sessions of airwork, it will help if you spend some time practicing holding heading and altitude at approach airspeeds while changing flap configurations—full flaps, no flaps, and everything in between—to learn the aircraft's responses and the power-pitch inputs required. With some practice, you'll be ready for whatever kind of landing is called for next!

WHAT'S THE CEILING?

WHAT'S THE CEILING?
When it comes time for you to fly solo, your instructor will note limiting weather conditions for your flights in your logbook. One limit likely will be the lowest ceiling under which you are permitted to solo. Another may be a minimum visibility value. [See the Jan. 27, 2006, Training Tip "Solo Limitations."]

Not all cloud cover represents a ceiling. It depends on how much of the sky is visible. The definitions used to describe sky cover carry inferences as to whether a ceiling exists. "A ceiling, for aviation purposes, is the lowest layer of clouds reported as being broken or overcast, or the vertical visibility into an obscuration like fog or haze. Clouds are reported as broken when five-eighths to seven-eighths of the sky is covered with clouds. Overcast means the entire sky is covered with clouds," explains chapter 10, page 17 of the Pilot's Handbook of Aeronautical Knowledge.

You'll find current sky conditions in aviation routine weather reports (METARs) and many automated observations. Sky cover reported as less than broken (few clouds, or scattered layers) does not constitute a ceiling. See the table of contractions on chapter 11, page 6 of the handbook for sky cover, represented in eighths (octas) of the sky from horizon to horizon, for each description.

Why octas? "Students frequently ask why sky cover and obscurations are reported in octas rather than tenths. The four cardinal points of the compass (N, E, W, S) and the four intercardinal points (NE, NW, SE, SW) divide the compass into eight sectors. Cloud cover and obscurations are easy to evaluate if you observe the conditions that exist in each of the eight sectors and base your report on how many sectors that condition occupies. Sky cover is also an element in pilot reports (pireps).

On nonflying days, practice estimating sky cover and comparing your conclusions with aviation weather reports. Also check out the AOPA Air Safety Foundation's online course "Weather Wise: Ceilings and Visibility" to further sharpen your skills.

HEAVY AIRCRAFT

A sample question from the private pilot knowledge test question bank asks: "When departing behind a heavy aircraft, the pilot should avoid wake turbulence by maneuvering the aircraft

A) below and downwind from the heavy aircraft.

B) above and upwind from the heavy aircraft.

C) below and upwind from the heavy aircraft.

When clearing you for takeoff or landing, the tower controller may add to your clearance the phrase "Caution wake turbulence" from the preceding arrival or departure. Although it may seem obvious to the pilot of a single-engine trainer that the preceding aircraft is heavy, the use of the term has special significance, as explained in Chapter 7 of the Aeronautical Information Manual (AIM): "For purposes of Wake Turbulence Separation Minima, ATC classifies aircraft as Heavy, Large, and Small as follows: Heavy—Aircraft capable of takeoff weights of more than 255,000 pounds whether or not they are operating at this weight during a particular phase of flight. Large—Aircraft of more than 41,000 pounds maximum certificated takeoff weight, up to 255,000 pounds. Small—Aircraft of 41,000 pounds or less maximum certificated takeoff weight."

Considering those definitions, the AIM describes aircraft separation requirements: "Because of the possible effects of wake turbulence, controllers are required to apply no less than specified minimum separation for aircraft operating behind a heavy jet and, in certain instances, behind large nonheavy aircraft (i.e., B757 aircraft)," as Elizabeth A. Tennyson explains in the AOPA Flight Training May 2001 column "Aviation Speak: Heavy."

If you find yourself facing wake turbulence on departure, you may choose to ask the tower to approve an early turn (upwind of the wake's probable drift track) when altitude permits after takeoff. Make this request when you contact the tower for your takeoff clearance. Don't wait until you are airborne, when traffic concerns or frequency congestion can delay approval.

Stay alert to hearing the word heavy on the ATC frequency!

"Pilot or Operator?"

"Pilot or Operator?"

It's my latest obsession. Pilots using GPS and using it wrong. I've been on a mission for the last few newsletters to try to give reasons on how to use GPS correctly and not let it become your only form of navigation. So here's my latest installment and it's one that I think drives the point home.

When you think about using a GPS in a car that same logic doesn't carry through to an airplane. For example, if you set the address wrong you'll just go to the wrong place and probably nothing else will happen. Maybe the database isn't 100 percent correct and you take a turn to a dead end. Again, probably nothing bad will happen. You set where you want to go in the GPS and you "allow" it to take you there. You can eliminate all sense of direction if you want and just follow the voice commands from the GPS. You are an operator of the GPS and really you don't need to know anything else about how it works or the errors it may have or really much of anything else. If the GPS makes a mistake, or you do, the consequences aren't that bad. It's a time penalty and that's about it. So you can truly just be an operator of the GPS and get by just fine.

GPS in aircraft are different than GPS in your car. The consequences of making an error using the GPS are higher and because the GPS is not just going to an address, gas station or following a single road etc. there are many more choices of flight plan routes to consider. The car only has a few choices, we have many more.

Terrain, what to do if the engine fails over this area or that, weather, choice of airports for fuel stops etc. are all extra things to consider when we use an airplane GPS that don't exist when we use the car GPS. It's important to be a pilot first and a GPS Operator second. We must use our judgement when selecting routes, airports etc. without just letting the GPS do it for us. Why? Because in an airplane you don't want to be just an operator because the consequences are too high. When we allow the GPS to tell us where we are and where we are going we become operators and we are no longer pilots.

So how do we fix this? Well to start we challenge ourselves to know where we are first then let the GPS confirm that we are in fact there. We ALWAYS use a different form of navigation other than GPS to back up data that the GPS is giving to us. We begin thinking that the sky is one big canvas that we can navigate in any way we choose and not as a series of IFR airways and intersection to intersection flight planned GPS routes or VP this or that. When we begin using the GPS as a pilot first we allow ourselves to consider all possibilities and not just the pink line. IFR Flying is a slightly different story as there may only be GPS data available.

So in summary, learn to tell the GPS where you are, then affirm the GPS is where you know it to be. A last thought is that GPS can be a powerful tool to help you navigate to a nearest airport in case of trouble or to take a more direct route.

Use the GPS as an aid in navigation and it will be yet another powerful tool for you to select to use as a pilot, not one you MUST use. This simple approach will help take you from an Operator to a Pilot.