Free FAA Commercial Pilot Practice Test

Slant range error in DME is greatest —

• A. when the aircraft is more than 50 NM from the station.
• B. only when the DME is not receiving a valid signal.
• C. at high altitude and close horizontal distance to the station. ✓
• D. at low altitude and long distance from the station.

DME measures the hypotenuse, not ground distance. Directly over a station at 6,000 feet AGL the DME reads about 1 NM even though ground distance is zero. The error becomes negligible when horizontal distance exceeds about three times the altitude in thousands of feet.

Reference: AIM 1-1-7

An emergency locator transmitter's batteries must be replaced or recharged after the transmitter has been in use for more than —

• A. 1 cumulative hour, or when 50 percent of their useful life has expired. ✓
• B. 30 cumulative minutes, or annually.
• C. 1 cumulative hour, or every 12 calendar months.
• D. 2 cumulative hours, or when 25 percent of their useful life has expired.

One cumulative hour of use, or 50 percent of useful life (or useful life of charge). The ELT itself must be inspected every 12 calendar months, and a fixed-wing aircraft may be operated up to 90 days with the ELT removed for repair, with a placard and a logbook entry.

Reference: 14 CFR 91.207

An airplane cruising at 8,000 feet with an indicated airspeed of 140 knots will have a true airspeed that is —

• A. lower than 140 knots.
• B. equal to 140 knots.
• C. higher only if the temperature is below standard.
• D. higher than 140 knots, because air density decreases with altitude. ✓

True airspeed rises roughly 2 percent per 1,000 feet above indicated, so about 16 percent at 8,000 feet — near 162 knots here. Warmer-than-standard temperatures increase it further.

Reference: PHAK ch.11

The primary advantage of WAAS over basic GPS is that it —

• A. improves accuracy and integrity enough to support vertically guided approaches such as LPV. ✓
• B. provides two-way communication with ATC.
• C. increases the number of satellites in the constellation.
• D. eliminates the need for a current navigation database.

WAAS corrects for ionospheric delay and satellite clock and ephemeris errors using ground reference stations, then broadcasts the corrections via geostationary satellites. That accuracy and integrity is what makes LPV minimums — often as low as 200 feet — possible.

Reference: AIM 1-1-18

During agricultural aircraft operations under part 137, the operator must —

• A. operate only under an air carrier certificate.
• B. hold an agricultural aircraft operator certificate and take precautions for persons and property on the surface. ✓
• C. remain above 500 feet AGL at all times.
• D. file a flight plan for each dispensing flight.

Part 137 has its own operator certificate. It permits the low-altitude flying that dispensing requires — an explicit exception to the 91.119 minimum safe altitudes — while imposing duties toward people and property below.

Reference: 14 CFR part 137; 14 CFR 91.119