Contents
Added Items
Gadget: K-mart altimeter bug
1/2" suction cup with straightened hook.
Lost Radar Contact
AIM says that if radar contact is lost the pilot/aircraft must resume "normal position reporting". This means using the PTAEN mnemonic for position, time, altitude, ETA to next and name of fix that follows. Estimates should be based upon time but distance is o.k. as an add-on.
On Proficiency
A proficient IFR pilot should be able to fly using partial panel to minimums in light turbulence.
Turn coordinator vs Needle
Needle/ball vs turn coordinator. The turn coordinator is not as good as the needle in showing a turn or wings level since it shows wings level before the wings are level. A pilot may make several tries before getting wings level when using the turn-coordinator. The needle 'senses' the turn
Attitude Indicator
The attitude indicator gives instantaneous indication of pitch and bank. It is the only instrument on the panel that provides a clear picture of the flight attitude of the aircraft. Most modern AIs permit full 360-degree rotation about the roll axis with pitch stops at 60 degrees. Marked to show + 50 degrees nose up/down and 20 degrees when inverted. but no specific degrees by markings. Do not have caging knobs.
The attitude indicator (called the artificial horizon in former years) has a vertical gyro as its spin axis. They do precess but it has an erection system activated by gravity that resets it back to the vertical. The AI has bank markings up to 90 degree banks. The first thirty degrees is divided into 10 degree units. Very close to the standard rate turns can be achieved by reference to the AI. Every airspeed has a degree of bank (coordinated) for a standard rate level turn; this is about 15% of airspeed; 15 degrees at 100 kts, 12 degrees at 90 knots. Use turn coordinator with ball centered to confirm angle required.
A Navy study found that during major attitude changes 85% of experienced IFR pilots focused on the AI. When the AI is set for level flight its movement can be set to position the nose for any selected climb speed. There will be a consistent correlation between power, trim, nose attitude and AI attitude. Knowing this removes the aircraft as a problem.
Instrument interpretation means to look at the instrument and make an appropriate correction for the indication. Instruments in a given flight condition are selected for pitch, bank and power. You set the aircraft attitude and power to get the trend you want. You fine tune using the instruments with numbers. Begin any maneuver using the attitude indicator (AI). Set the AI, check the trend of climb, descent, level, and turn. Now go to the numbers for making the selected flight condition precise.
Ability to scan from the Set AI to check the trend to the numbers back to the set requires prior knowledge of where you are going to move your eyes. In level flight, with a predetermined power and airspeed, the scan can be a relative easy and slow AI, HI, AI, Alt, AI. The scan must be changed and accelerated if a change of heading is required and even more speed if a descending turn is called for. The sequence of required instrument scan is not so important as keeping the eyes moving always back to the AI
Use the AI as the central instrument. It gives direct indication of pitch and bank information. It is the best single source of aircraft attitude. Flying the AI makes you safe. Make your turns with AI, check TC for accuracy, the VSI for perfection and use the HI (numbers) to measure results. Scan should include the AI in every second or third fixation. (You can't see when your eye is moving.)
The AI gives pitch attitude, bank attitude and bank angle
Attitude Indicator Errors
The erecting mechanism operates continuously but is limited to 3 degrees per minute to avoid errors due to sensed 'gravity' during banks. During prolonged banks in one direction this error can be significant. Very shallow bank turns or flying out of rudder trim for long periods can produce errors. Any maneuver that displaces straight and level will result in AI error if it lasts long enough. Coordinated and uncoordinated turns will do this. It is for this reason that holding patterns have the one-minute level flight legs after each minute of turn. This leg allows the AI to settle itself. This may be the reason the FAA prefers the 45/180 for the procedure turn insstead of the simpler 90/270.
When making a 180-degree steep turn and then rolling out your attitude indicator will show a nose up and wing down in a direction opposite the turn. The error is inherent to the erecting mechanism. The errors tend to cancel in 360 degrees. Taxiing turns are always skidding turns. It is normal for the AI to show up to five degrees of tilt during taxi turns. Any more requires investigation. AI gyrations during initial start of the engine is normal. If the bar fails to stay horizontal or tips over 5 degrees during taxi, it must be deemed unreliable.
A vacuum powered attitude indicator gives warning of failure. It will be slow to erect and may go through gyrations while erecting. It may be sluggish in flight. To see what an instrument does when it loses power--when the vacuum pump fails, for example--watch it run down after shutdown. There is no way to predict what an instrument with an internal problem will do. Don't chance flying IFR with an instrument that has failed and then recovered. Don't fly with one that is even suspected of being faulty. Being on partial panel (real failure) in IMC requires landing at the nearest suitable airport. Report failure to ATC. Airports with ASR approaches can give no-gyro approaches. On final, turns should be at half-standard rate. If controller offers no-gyro approach take it.
The AI and TC operate on vacuum and electricity respectively. The AI has a device to automatically align it to local gravity as seen in the cockpit If the information is conflicting (you know the standard rate reading of the AI for the different airspeeds) suspect one system has failed. Go immediately to the Compass as a friend you can trust.
Pitch
AI-
Airspeed and VSI (VSI shows vertical trend after a few seconds)
Altimeter (FAA primary-with the numbers)
Bank
AI
TC gives roll into turn rate, turn rate and coordination
HI (FAA primary-with the numbers)
Power
RPM
Airspeed indicator-with the numbers
AI Demonstration
Cover everything but AI (Simulates instrument failure of aircraft with (HSI) and intercept an airway or VOR radial in level flight. Fly radial using only AI.
Cover everything but AI and establish best rate pitch attitude going into successive left and right banks and then to one bar descent with left and right banks. Success depends upon power settings and changes.
Cover everything but AI and make timed turn to heading using knowledge of airspeed/angle of bank as function of turn rate. At the end of each timed turn check altimeter. Practice until you can make timed turns without changing altitude using only AI and your ability to fly aircraft.
Cover everything but AI and make timed climbs and descents using a set sequence of attitude, power and trim. Before recovery make a Check (peek) of VSI and altimeter to see how your settings are performing.
Turn Coordinator
The turn coordinator is usually an electrically driven gyroscope. It is mounted at an angle of 30 degrees with the back slanted downward. It is dampened to reduce the reaction to turbulence. It originally served to control single axis autopilot's. It senses both yaw mostly and roll rate slightly. Initially it senses roll and when the bank is established it senses yaw (rudder) input. Knowing the airspeed, the angle of bank can be inferred. The TC ball (slip-skid) indicator is smaller than that on the older needle and ball instrument. The TC will indicate the direction of a spin so you will know which rudder application is opposite. This is not true if the spin is inverted. In an inverted spin the turn coordinator will give incorrect information for recovery. A failed TC will "park" level. A very good reason not to use as a level flight indicator except in emergency.
Overhaul calibration of both TC and Needle is done by adjusting centering springs. As the springs weaken with age sensitivity to yaw increases so does gyro friction increase with age with a decrease in sensitivity. The net effect of these changes are unpredictable. Ground check of T.C. operation is that in a left turn the ball moves to the right and aircraft remains level.
Needle and Ball
The needle's gyro axis is mounted horizontally and spins up and away from the pilot. It tilts on the roll axis up to 45 degrees. It cannot move on the vertical axis. A yaw of the aircraft causes the gyro to yaw in the opposite direction. Reversing linkage gives correct direction and amount. Oscillations are prevented by a dashpot mechanism. British slang name for turn and bank indicator is, "Bat and ball."
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