Last week my student and I went over the required instruments for an IFR flight and discussed the preflight instrument check. I thought it might be a good review for those of you who follow my blog and are thinking of doing an IFR flight. Of course, even if you are a doing a VFR flight, I think it's still a great idea to make sure all your instruments are working properly. I check my instrument in the same order each time to make sure I don't miss one...
Airspeed Indicator: Should indicate zero unless you are pointed into the wind and it is a pretty intense wind (in which case, maybe you should be flying?).
*Attitude Indicator: Make sure the horizon bar on the attitude indicator tilts no more than 5 degrees during taxi turns. I took this photo before the engine was on, thus the gyro is not spinning. If you saw the instrument show this during a taxi, it would not be legal for instrument flight.
Altimeter: Must indicate within 75' of the airport elevation when set to the correct airport altimeter setting. I fly out of KBFI, which sits at 21'; this instrument shows within 75' of that, so it would be legal for an instrument flight.
VSI (Vertical Speed Indicator): Make sure it shows zero... if it doesn't- no big deal! It's not a required instrument, so make a mental note of where "zero" is, and use that as your reference. Looks like 50 feet climbing is my zero reference for this little guy.
*Heading Indicator: Align the heading indicator with the magnetic compass and make sure before you takeoff that it doesn't precess more than 15 degrees in 3 minutes.
Turn Coordinator: The wings should show a turn in the direction of the turn on the taxi, the inclinometer should be full of fluid, and the ball should swing to the outside of the turn (since we don't bank on the ground, the ball is essentially showing a skid).
Magnetic Compass: Make sure the compass is full of fluid and swings freely during the taxi to known headings. I forgot to take a picture of this instrument, so google it if you're not sure what it is.
*The heading indicator and attitude indicator are vacuum driven instruments- give the the gyros 5 minutes to spin up before checking those instruments.
That's it! Once you get used to it, checking your instrument will take you a matter of seconds. Set them before you taxi, check them during the taxi, and then one last time during the runup check. I don't know about you, but if something isn't working properly, I would much rather know about it on the ground as opposed to in the air.