Instrument flying why the t scan

Automation is now expected to maintain the settings with precision. The disconnect happens here. T-scan enabled the pilot, who was manually flying the aeroplane, to concentrate primarily on the major performance indicator — the attitude indicator or artificial horizon and scan out and back to the secondary instruments, such as the speed and altitude. Humans generally do not like change especially human factors in the workplace. If they are set in their ways, there will be resistance.

Primarily, the resistance is to accepting anything new especially if it involves the use of cognitive skills. The aircraft back in the days had the cockpit crowded with instruments. NASA did research on displays that could process the raw aircraft system and flight data into an integrated, easily understood picture of the aircraft flight situation, culminating in a series of demonstration flights to demonstrate a full glass cockpit system.

Acceptance of electronic flight displays is reflected in the total. It begins with the introduction of the Boeing in The standardised practice used around the globe was T-scan. Transition to the EFIS aircraft was full of challenges of the new concepts of instruments and the automation philosophy. In the process, neither was a new scan pattern developed nor was it taught during training. The objective of the scan in a radial pattern is to maximise the focus at the center.

The order of the scan is not too important as long as the sequence is kept in a T formation. In the Heading Indicator Scan picture it can be seen that the first instrument chosen in this case is the heading indicator. The focus shifts from the attitude indicator to the heading indicator to interpret directional information. Once the information is determined focus shifts back to the attitude indicator to verify attitude information.

Once the attitude indication is verified, the next instrument altimeter in this case is scanned for altitude information. Once this information is interpreted and verified the focus shifts back to the attitude indicator to verify the attitude information.

Finally the last instrument in the T; the airspeed indicator is scanned for airspeed information. The airspeed indicator not only provides the airspeed but it also provides very reliable pitch information nose down airspeed is increasing, nose up airspeed is decreasing.

Once the airspeed is interpreted and understood the focus goes back on the attitude indicator. The T instrument scan is repeated throughout instrument flight as the primary instrument scan. You can fine-tune your flying by using the turn coordinator and the vertical speed indicator. Basic attitude instrument flying follows two paths, 1 primary and supporting instruments, and 2 attitude plus power equals performance.

Regardless of the method you still must develop a set of performance numbers for each configuration of the airplane. The fewer numbers you have the better. For complex aircraft get the number s in the flap operating range. Use configuration to get down. Make a chart of performance and configuration for climbs, cruise, descents, and approach. You want to know what your instruments are telling you. Knowing this, you need to make the instruments indicate the performance you are after.

The scan, or cross-check is probably best learned from a specialist. Some, like me, learned in a Link Trainer as my own teacher. What works for me is probably not desirable for you. Go to a simulator facility and take lessons specifically in cross-check skills. Even with the training you will put your own touch into how you scan. Scan, done properly is the major fatigue factor of flying. You must move beyond looking, into seeing, and finally into understanding.

Having a scan is not enough. Most any pilot can move his eyes in an ordered sequence as required for a particular manoeuvre. Doing the correct scan at the correct time at the correct speed is where the fatigue factor comes into play.

A slow cross-check that suffices for level flight must shift gears when making a turn, shift still further when making a turning descent, and even further when making a timed turning descent to specific heading.

The competent basic instrument pilot must know the specific scan and speed required for every given situation. Steady state flight has a scan for level, descent, and climb. Turns add a new dimension and a new scan Different kinds of turns have still different cross-check requirements. You need to know and use the scan and cross-check required. A cross-check that lacks the proper speed, sequence, stop, and interpretation is going to break down.

Fixing the results of an improper cross-check is much more difficult than getting it right and keeping it in the first place. If you know the cross-check sequence you are going to be aware of the hazard of fixation. You are far more likely to fixate on a movement. If the movement is not where it is supposed to be fixation is even more likely. As you detect, by quick glances, the movement of instruments you should note that some movements are in the proper direction and proper amount.

Your scan sequence is seeking out the distinctions between what should be and what is. As a basic instrument pilot you can improve your scan, cross-check, and seeing skill and speed. To make the improvement you must deliberately push you speed. You should avoid going back to a single instrument twice in a row.

Never, is a dirty word in flying but it this instance it applies. If you know the information required for a given manoeuvre you can keep your cross-check moving through the instruments that have and give that information.

Knowing where to look lets you see change as it happens. Seeing something happen must conform to your mental picture of what is supposed to happen. Easy to say, not so easy to do at first.

The PAC technique classifies the attitude indicator and tachometer as control instruments. The PAC is used in the takeoff as applied power, rotate to Vy attitude and configure. The climb is made first with power adjustment, pitch attitude and configuration. Cruise begins with power setting, attitude set and configure cowl flaps. Descent sets power, pitch, and possible configuration change. Holding sets power, attitude and configuration.

The non-precision and precision approaches begin with power, attitude, configuration as required for descent and tracking. The go-around begins with power, attitude, configuration, which way, how far and communications.

Flying Problems Instrument flying problems usually are from faulty scan. Instrument interpretation, fixation, selection and control reactions individually or in combination cause a flight problem.

Fixation on an instrument, the AI, is an acceptable procedure when redirecting the airplane, reacting to vertigo and flying in turbulence.

The most important element of a standardized scan is knowing when to look for what. Scanning fatigue occurs when we are moving our eyes without purpose. Try moving your eyes side to side a few times. Also note that while your eyes are moving you cannot see anything. You will see without fatigue when your eyes are stopped and have been moved for a purpose.

General Solutions Trick to break habit of rushing from one instrument to the next is to say aloud the indication and its significance Process keeps scan slow enough to understand what is being seen and what you want to see.

Problem: Chasing the VSI or using the slope needle for pitch changes is an early cause of vertical S's on the glide slope. Solution: Pitch changes are made on the AI.

Problem: S-turns while tracking a needle. Student is probably trying to fly plane 'level' by reference to HI. Problem: Small variations of altitude. Solution: Use pitch AI to correct. Above ' use both AI and power for correcting. Be prepared to tell the instructor where you are looking during the scan and what is making you react as you do. Because of cockpit limitations the instructor can only guess as probable causes. Getting a Scan You are moving your eyes across each instrument for information.

Move the eyes too fast and you will lower your ability to make interpretations correctly. A slow scan can cause fixation. Initially, don't try for accuracy. Visualize putting the airplane where you want it by watching the attitude indicator. He knows when to do something and how much of it to do.

The Practical Test Standards PTS give the objectives and skill level requirements but don't tell how easy or difficult the acquisition may be. Most IFR students have 60 hours or instrument time before taking their checkride. Decide what you want. Decide where to look for the performance you seek.

Greatest area of misinterpretation is in making compass turns without the aid of the clock. A normal scan is clockwise beginning with the AI. For a rate turn the initial scan begins counterclockwise from the AI.

No one instrument gives all the information. Each instrument must be scanned to obtain confirmation of information either sought or required. Climb to Level 1. If unacceptable redo 1. Climb and Descent-Scan When climbing and descending at constant power, airspeed is primary pitch. To maintain airspeed during descent, lower nose on AI only and immediately reduce power to predetermined setting to hold airspeed. Trading airspeed for altitude or altitude for airspeed may be preferable.

If both airspeed and altitude are high or low you must adjust both pitch and power. Where manifold pressure is used for power the descent causes an increase. Power must be regularly reduced to maintain airspeed. A rule of thumb for establishing a 3 degree slope descent is to multiply your ground speed by 5 and add Not exact but good enough. A climb is not as sensitive to pitch as to power and airspeed.

Once speed and power are set, pitch is locked by use of trim. Levelling off is more difficult. Lower nose to AI horizon while avoiding any roll input. Major trim adjustment. Check VSI. Check AI. Listen for acceleration to speed desired. Altitude check. Set power. Minor trim adjustments. AI check. Scan Instruction for Cockpit Operations Go from heading to attitude indicator to altimeter. Always include AI as a scan segment between every part of writing, changing frequencies or any cockpit operation.

Raise pitch and add power. Anytime airspeed is constant any change in pitch requires an opposite hand movement to change power. Practice the vertical S in which each cycle decreases by ' Detecting Instrument Failure Instrument failure is not always accompanied with a warning flag.

As a part of your pre-approach briefing you should cross-check all informational sources to assure proper operation of primary information sources. Failure to make a verbal approach briefing makes such a cross-check essentially impossible. Bank is compared with the AI vacuum , TC electric. When in doubt let go of the controls and sort things out. Compass is used to check AI and TC for wings level or direction of turn.