Part 107 Weather and Performance Questions: Density Altitude, Load Factor, Stability and Thunderstorms

Two small ACS areas share this material. "Effects of weather on performance" (UA.III.B) lists eleven factors, from density altitude to lightning, and "Loading and Performance" (UA.IV.A) covers weight, balance and performance data. Under PSI's 2025 specifications, Weather is 5% of the test and Loading and Performance 2%, so together they come to about 4 of 60 questions. They're worth a short, focused session rather than a week: most items turn on one cause-and-effect fact.

This guide follows the FAA's 2026 Aviation Weather Handbook (FAA-H-8083-28B) and the Remote Pilot Study Guide (FAA-G-8082-22, 2016). Where the two differ on a detail, the handbook is the newer source, and the difference is noted.

Density altitude and drone performance

The handbook defines density altitude as pressure altitude corrected for temperature deviations from the standard atmosphere. The practical meaning is simpler: higher density altitude means thinner air, and thinner air means worse performance.

The handbook says temperature is the most important factor, and that moisture contributes but its effect is generally negligible. The 2016 Study Guide says humidity "does contribute." Both agree on the direction: more humidity, higher density altitude.

For any aircraft, the handbook lists three effects of high density altitude: less power, less thrust and less lift. AC 107-2A applies that to drones: high elevations, high temperatures and high humidity "may require a reduction in weight before flight is attempted." The standard atmosphere behind all of this is 29.92 inches of mercury and 15 °C (59 °F) at sea level.

To compute density altitude, the handbook's method is to set an altimeter to 29.92 to read pressure altitude, read the outside air temperature, and use a flight computer. The testing supplement includes a Density Altitude Chart (Figure 8) that does the same job on paper.

Load factor in turns, with worked examples

The Study Guide defines load factor as the ratio between lift and weight, measured in Gs. A load factor of 3 means the structure carries three times the aircraft's weight. The Study Guide explains it with banked turns, so the examples below use fixed-wing drones.

The testing supplement's Load Factor Chart (Figure 2) gives these values for a level, coordinated turn:

To find the load, multiply the aircraft's weight by the load factor. Worked examples by Passy, rounded to one decimal:

• A 7-pound fixed-wing drone in a 30° bank: 7 × 1.154 = 8.1 pounds of load.
• A 12-pound fixed-wing drone in a 45° bank: 12 × 1.414 = 17.0 pounds.
• A 9.5-pound fixed-wing drone in a 60° bank: 9.5 × 2.000 = 19.0 pounds.

Two consequences from the Study Guide:

• Load factor climbs steeply past about 45 to 50 degrees of bank. At 60 degrees it's 2, at 80 degrees it's 5.76 in the Study Guide's text (5.747 on the supplement chart), and a constant-altitude turn at 90 degrees is impossible.
• Stall speed rises with the square root of the load factor. In the Study Guide's example, an aircraft that stalls at 50 knots unaccelerated can stall at 100 knots at a load factor of 4, because the square root of 4 is 2.

For the Loading and Performance area itself, the 17 Loading and Performance questions planned for Part 107 prep are sized to that area's small share of the test.

Weight, balance and center of gravity

AC 107-2A and the Study Guide make the same points about loading a small drone:

• Follow the manufacturer's weight and balance limits. A maximum takeoff weight doesn't mean the aircraft can always lift it. High density altitude may require less weight.
• The center of gravity moves when loads move. If a payload shifts or is released, the CG shifts. If it falls outside the limits, relocate or remove weight before flight.
• Excess weight hurts nearly everything. The Study Guide's list includes a longer takeoff run, a reduced rate and angle of climb, reduced maneuverability and a higher stalling speed.
• Two rules frame it. Under 107.3, the 55-pound limit includes everything on board or attached. Under 107.49(e), the remote pilot must make sure anything attached or carried is secure and doesn't harm the aircraft's flight characteristics or controllability.

Stable and unstable air

The Study Guide contrasts the two air masses this way:

Related facts the Study Guide gives: cool, dry air is very stable. Warm, moist air is the most unstable. A temperature inversion, where temperature rises with altitude, makes a shallow, stable layer that can trap haze, smoke and fog. When temperature and dewpoint are close together, fog, low clouds and precipitation become likely. Contrasts like these suit short daily sessions, and a daily goal with a streak is planned for full Part 107 prep.

Wind, terrain and surface heating

AC 107-2A's points for remote pilots:

• Obstructions break up the wind. Buildings, trees and terrain create gusts that change quickly in speed and direction. The turbulence grows with the obstacle's size and the wind speed.
• The leeward side is the dangerous side. Wind flows smoothly up the windward side of a mountain, but down the leeward side it follows the terrain and becomes turbulent, with downdrafts that can be severe in valleys and canyons.
• Uneven surface heating creates convective currents. Plowed ground, rock and sand heat the air above them more than water and vegetation do, producing bumpy, turbulent air.

Thunderstorms, microbursts and icing

The handbook says thunderstorm cells need three ingredients: sufficient water vapor, unstable air, and a lifting mechanism such as a front, upslope flow or converging winds. Each cell goes through three stages:

The 2016 Study Guide marks the start of the mature stage a little earlier, when precipitation begins to fall from the cloud base, and says all thunderstorm hazards reach their greatest intensity during the mature stage. The handbook puts a typical cell's whole life cycle at about 30 minutes. Hail, tornadoes and lightning are on the ACS list too, and the Study Guide ties all three to thunderstorms, which can produce large hailstones, damaging lightning and tornadoes. The Study Guide also says a small drone that enters a thunderstorm could meet updrafts and downdrafts exceeding 3,000 feet per minute.

Microbursts are the most severe type of wind shear. The handbook describes a typical microburst as less than 2.5 miles across (the 2016 Study Guide said 1 to 2 miles), about 1,000 feet deep, and lasting about 5 to 15 minutes, with downdrafts of up to 6,000 feet per minute. The Study Guide describes the sequence a small drone may meet: first a performance-increasing headwind, then a downdraft, then a sharply increasing tailwind.

Structural icing needs two things, per the Study Guide: visible moisture, such as rain or cloud droplets, and a temperature of 0 °C or colder where it strikes the aircraft. Frost on a drone before flight is a hazard too: it disrupts airflow, reduces lift and increases drag, so the Study Guide says to remove it completely.

Ceiling and visibility close the list. They connect directly to the Part 107 limits of 3 statute miles of visibility and 500 feet below clouds, which the Part 107 METAR and TAF guide shows how to check.

Weather and performance practice items written by Passy

These are original practice items, not FAA test items. Decide first, then read the reasoning.

1. Which day gives a drone the best climb performance at the same field: 32 °C and humid, or 5 °C and dry? The cold, dry day. Lower temperature and lower humidity mean denser air and a lower density altitude.

2. A 15-pound fixed-wing drone makes a level, coordinated 60-degree banked turn. What load does the airframe carry? 30 pounds: 15 × 2.000.

3. Cumulus clouds, showers and bumpy air are reported near a job site. What kind of air mass is that? Unstable air.

4. A drone with a heavy camera will fly from a high mountain lake on a hot afternoon. What should the remote pilot expect? Reduced performance from high density altitude. AC 107-2A says such conditions may require reducing weight before flight.

If one of these fooled you, use the miss: nine Loading and Performance flashcards are planned for full Part 107 prep, and the free Part 107 practice questions work today. To place this short topic in your schedule, see the Part 107 study plan guide, which gives it a fixed share of study time, and keep the Part 107 numbers guide open for the figures.