Last week class was cancelled due to snow. One of general aviation’s greatest nemesis – weather. Which makes day two (the week prior) that much more valuable. Instruments. Specifically the gyros and compass.
Regulation: *It is your responsibility as pilot in command to make sure that an altimeter systems check has been made within the preceding 24 calendar months. You must also make sure that the required equipment for IFR flight is functioning properly. “Calendar Month?” You have the entire month to perform the check.
*What equipment is required for Day/Night IFR Flight?
Day VFR + Night VFR + Day IFR = Required Instruments for Night IFR
Day VFR: Goose a Cat
Night VFR: Flaps
Day IFR: Grab Card (Then add the Flaps for night)
(Day VFR + Flaps)
Fuses (or circuit breakers)
Landing light (if for hire)
Sufficient electrical power
Day IFR + Day VFR +
Generator/alternator of adequate capacity
Radios (communication and navigation as required for planned flight)
Accurate altimeter (adjustable for barometric pressure)
Ball (slip/skid indicator)
Clock (sweep second hand or digital display)
*The FAA will want to know that you know Gyros work because of rigidity in space and that the airplane actually rotates around the gyro. What they don’t tell you is that the gyro really does only work for about 500 hours. I learned this fact from my instructor – retired Boeing engineer, I am a believer, as was he when he was in solid IFR flight and lost his gyro. Experience is the best teacher.
What happens then? How do we fly? First… we default back to lesson one and believe our instruments. But what instruments? We lost our gyro! We don’t have an attitude indicator. This is the making of an aviation thriller.
This is the time that you appreciate your due diligence in learning how to navigate with a compass and the turn indicator, because they will save your life. A thorough understanding will not only help you to pass your instrument test but will save your life one day.
A few things to note when everything is working: The attitude indicator is a self-erecting mechanism, and is the only instrument that shows immediate pitch and bank. Now precision errors. Next time you fly your plane note that when you roll out of a bank, the miniature airplane will show the aircraft in a turn opposite direction.
*Errors in both pitch and bank indication are usually at a maximums as the aircraft rolls out of a 180 degree turn. Other errors occur during acceleration and deceleration. Rolling out of a step 180-degree turn to the right the miniature plane will show a slight climb and turn to the left. It’s a good idea to know these parameters for your test. If you fly a 360 degree turn, no errors. Each 180 degree turn wipes the errors of the other out.
But to save your life, we need to know what happens when we’re in the clouds and lose our attitude indicator. Fly the compass? Fly the turn indicator? Hmmm. They both work.
The compass has problems of its own. At the equator the magnetic field parallels the earth. But aircraft flown in the northern hemisphere need to have balance, so they have weights in the compass on the south side. Just the opposite in the southern hemisphere. *Northerly turning error in a magnetic compass is caused by magnetic dip. *Magnetic variation varies for different headings of the same aircraft.
Just like the plane turning around the gyro, the plane turns around the compass. Another memory gouge:
ANDS = Accelerate North. Decelerate South.
AND we do have acceleration errors. But not while on a north or south heading because the compass is balanced. What happens is that when you roll out you will need to either roll out early or lag the rollout, depending upon your heading.
UNOS = Undershoot North. Overshoot South.
Wow… could be confusing if you lost your attitude indicator. We do have something else to help us. The turn indicator. *A standard-rate turn is 3 degrees per second. It takes 60 seconds to turn 180 degrees. A half-standard-rate turn is 1? degrees per second. It takes 4 minutes to turn 360 degrees.
Experience is the best teacher
Having never had to experience this type of navigating under actual conditions, I default to my instructor. He has. He also knows all this precision error stuff like the back of his hand. What did he do when he lost his attitude indicator? He timed his turns.
ATC told him, “You’re cleared to fly a heading of 040, standard-rate turns not required.” He thought, “Why would I not use standard rate?” He timed his turn and had to make minimal adjustments, but it worked great. If the expert prefers this method, I think that might be my choice too.
The turn indicator is your friend. Wait! What is the difference with a turn-and-slip indicator? *The miniature aircraft of the turn coordinate directly displays rate of roll and rate of turn information; the turn-and-slip indicator only gives the rate of turn. Both instruments indirectly indicate the bank attitude; the needle displacement increases as angle of bank increases.
Vertical speed and level flight-I use this primary and altimeter the back up. Yes, each Boeing type-rating I earned, I used the IVSI (instantaneous vertical speed indicator). Think about this… you have to go somewhere, before you get somewhere. The altimeter tells you where you are and the vertical speed indicator tells you you’re moving, which direction and how fast. When you’re on altitude, fly the needle on the vertical speed indicator. Keep if from moving, your altitude won’t change.
Learn your instruments. Know what to do when you don’t have them. Know what you need to be legal. You can pass your test with ease. But the real test is going to be in the plane. Focus your training on what if this was a real life scenario.
[ * ] Note: Every stared and italic statement is an actual FAA Instrument test question. Learn a couple each day, and you’ll be on your way to success.
Happy Flying and Enjoy the Journey!
Please note: The regulations and minimum equipment list information provided are based on FAA regulations and do not necessarily apply outside the USA.
Shortt URL for this post: