As you know, there are certain checks above and beyond your normal VFR checks that you have to do for IFR flying. You want to be sure that your instruments are operating correctly because you will no longer be able to see out the window when flying and will be relying on them completely to control the plane.
Pitot Heat check for IFR
For your IFR instrument check you will be checking things a little closer during your preflight. How many times have you checked your Pitot heat during a VFR inspection? When flying IFR you should be sure it heats up because if you end up in icing conditions (unintentionally of course), then the pitot tube opening could get covered in ice making the airspeed indicator useless. What’s even worse is if the pitot tube and drain both get blocked. This would cause your airspeed indicator to act like an altimeter. This means that if you were to climb slightly, your airspeed would show higher. As your airspeed shows higher (faster), you would pull up slightly to slow the plane down. As you pull up, it climbs more, showing a higher speed, causing you to repeat until you get totally confused and pull it into a stall and lose control. You need pitot heat to keep the ice off the pitot tube.
Turn Coordinator / Rate of Turn check for IFR
When you turn on the master switch, listen closely because on many planes you can hear the electric gyro to the turn coordinator start to make a whining noise as it starts to spin. As you taxi, you want to be sure that your turn coordinator is moving properly too. This is your only back-up instrument for flying straight if you lose your vacuum instruments. Without it, you will not be able to tell if you are turning. You could roll upside down and not realize it until it’s too late. It’s also good for timed turns.
Compass check for IFR
Your compass should be moving freely and filled with liquid too because it will be the only thing available to tell you what heading you are flying if you lose your vacuum.
Vertical Speed (not required for IFR)
Your vertical speed should read zero on the ground but sometimes it doesn’t. If it is off, just make a mental note of where it is and make that your zero point. You can do this because it’s not even required for IFR.
Altimeter check for IFR
When setting the altimeter to the proper pressure, it should read within 75′ of field elevation or it cannot be used for IFR. Can you imagine flying in the clouds, coming in for a landing and thinking you were 75′ higher than you actually were? There will be some error but this is the cut-off.
Gyro instrument check for IFR
Your IFR instrument check also includes your vacuum gauge. Without vacuum, you have no Gyro instruments. This means that you lose your heading indicator and your artificial horizon (attitude indicator). During idle, your vacuum may not have enough suction to spin the gyros fast enough to operate the instruments properly and may even cause a low vacuum light to show up. Just bump the power up a little or double check during run-up to be sure everything is working ok. As you taxi, your heading indicator should show turns. Your main instrument for IFR flying will be your attitude indicator (artificial horizon), so what do you do if you start the plane and it looks like the image above and is not upright and erect? The answer is to give it 5 minutes. It can take 2-3 minutes for the gyros to spin up fast enough to correct the attitude indicator but it can take as long as 5 minutes per the Instrument Flying Handbook. If it hasn’t corrected itself in 5 minutes, it should be considered unreliable for IFR flight.
Electric System check for IFR
Your electric system should be charging properly so be sure to check it, because if you lose your electric you have no way to navigate except to fly a compass heading toward the nearest VFR conditions.
Clock check for IFR
In IFR flying, you need to have a clock to be able to keep track of every second, so be sure it’s working.
VOR check for IFR
Your VOR’s have to be checked, but since you can’t really check them on the ground unless you happen to be based at an airport with a ground based VOR checkpoint, you have to check the VOR’S once every 30 days and make a log of the check. I’m not going into the specifics because they can be found in the regulations but in order to file IFR, the check must be done.
Additional IFR Checks
Lastly, you want to be sure that all your pressures and temperatures are within limits and no warning lights are on. If you have carburetor heat or alternate air, make sure they are working in case you get induction icing. You should also check both your radios to be sure that you can hear them and that the frequencies are set properly. If you have a GPS, make sure the database is current.
If you have any questions that I did not answer, then please feel free to post a comment or send me an email!
Take Care
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