When performing the preflight inspection before an instrument flight, there are a few things we need to be concerned with over a VFR flight.

For instrument flight, VOR receiver accuracy must have been checked within 30 days and found to be within limits. The pilot must log this VOR accuracy test in the aircraft logbook or other record. The VOR check log entry must include the date and place the check was accomplished, the bearing error, if any, and the entry must include the signature of the person who performed the check.

The altimeter, transponder, altitude encoder, and static system must have been checked within the last 24 calendar months.

ELT batteries must be replaced when 50% of their useful life has expired, or after 1 hour of cumulative use. If rechargeable batteries are used, then the batteries must be recharged or replaced after 50% of the useful life of the charge. The battery expiration date is usually written on the outside of the ELT.

Traditional, electrically powered flight instruments should be checked during the preflight inspection. For most aircraft, this involves turning on the master switch and observing the turn coordinator's red flag disappear. Also, listen for any irregular noise from the instrument, which may not be apparent after engine start.

As usual, make sure to check the compass chamber is full of liquid. Make sure it appears to be turning freely and that there are no bubbles in the fluid. With the master switch on and radios on, make sure the compass correctly indicates a known magnetic heading.

IFR Equipment Requirements

The following equipment is required for IFR flight:

1. All equipment required for VFR day and night flight.

2. Two way radio and navigational equipment appropriate to the ground facilities to be used.

3. Gyroscopic rate of turn indicator.

4. Slip-skid indicator.

5. Gyroscopic attitude indicator.

6. Gyroscopic heading indicator.

7. Sensitive altimeter.

8. Clock with sweep second hand or digital display.

9. Generator of adequate capacity.

10. Mode C transponder with encoding altimeter for flight above 10,000 feet MSL in controlled airspace.

11. DME when at or above FL 240 and using VORs for navigation.

Should the DME fail at or above FL240, the PIC shall report to its failure to ATC immediately and then may continue at or above FL240 to the next airport of intended landing.