Most-missed Part 107 test questions (from 5,724 real answers)

What the data says

• Airspace Classification and Operating Requirements is the most-missed area: 40% of learner-question pairs had at least one wrong answer, versus 18% in Regulations. 17 of the 25 most-missed questions come from this area, most of them about reading a sectional chart.
• Weather punches above its weight: it is only 5% of the test, but our learners miss it 26% of the time, second only to airspace.
• The single most-missed question (10 of 11 learners got it wrong at least once): “A Victor airway (V-route) depicted on a sectional chart is associated with which class of airspace?” The answer is Class E. See why.

Miss rate by ACS area

The 25 most-missed questions

1. #1Airspace Classification and Operating RequirementsUA.II.A.K1d

   91% missed it: 10 of 11 learners got it wrong at least once (20 answers in total)

   A Victor airway (V-route) depicted on a sectional chart is associated with which class of airspace?

   • AClass G
   • BClass B
   • Class ECorrect
   • DClass A

   Why it traps people

   Drone pilots fly low, so they assume anything on the chart near them is uncontrolled. Victor airways are federal airways, and federal airways are Class E: from 1,200 ft AGL up to (not including) 18,000 ft MSL. Below that floor you are usually in Class G.

   The answer, explained

   Victor airways are federal airways that lie within Class E airspace, typically extending from 1,200 feet AGL up to but not including 18,000 feet MSL. They are depicted as blue lines on sectional charts connecting VORs. Drone operations along Victor airways at low altitudes may still be in Class G.

   Source: AIM 3-2-6 (Class E airspace, federal airways) · Question written by Rotate Pilot

2. #2Airspace Classification and Operating RequirementsUA.II.A.K3

   91% missed it: 10 of 11 learners got it wrong at least once (18 answers in total)

   What does 'IR' stand for in the context of a Military Training Route designation?

   • AIntermediate Route
   • BInfrared Route
   • Instrument RouteCorrect
   • DInitial Routes

   Why it traps people

   "Infrared" sounds military, so it gets picked. On a Military Training Route, IR means the route is flown under instrument flight rules and VR under visual flight rules. Four-digit route numbers stay at or below 1,500 ft AGL; three-digit numbers have at least one segment above it.

   The answer, explained

   IR stands for Instrument Route, meaning the military training route is flown under IFR (Instrument Flight Rules). VR designates Visual Routes flown under VFR. Both types can have segments at various altitudes, and the number of digits indicates whether they go below 1,500 feet AGL.

   Source: AIM 3-5-2 (Military Training Routes) · Question written by Rotate Pilot

3. #3Airspace Classification and Operating RequirementsUA.II.A.K1e

   91% missed it: 10 of 11 learners got it wrong at least once (20 answers in total)

   An airport on a sectional chart shows a magenta airport symbol with no airspace lines around it. What class of airspace are you in at 300 feet AGL?

   • AClass D
   • Class GCorrect
   • CClass C
   • DClass E

   Why it traps people

   Magenta reads as "controlled". On a sectional, a magenta airport symbol only means the airport has no control tower (towered airports are blue). With no dashed magenta line and no magenta vignette, controlled airspace does not start low, so at 300 ft AGL you are in Class G and need no authorization.

   The answer, explained

   A magenta airport symbol indicates a non-towered airport. If there are no dashed magenta lines (Class E surface), no magenta vignette (Class E at 700 AGL), and no other airspace depictions, you are in Class G airspace at 300 feet AGL. No ATC authorization is needed.

   Source: FAA Aeronautical Chart User's Guide; 14 CFR 107.41 · Question written by Rotate Pilot

4. #4RegulationsUA.I.C.K3

   90% missed it: 9 of 10 learners got it wrong at least once (11 answers in total)

   Under what section of 14 CFR is Part 107 remote pilot certification addressed?

   • A14 CFR 107 Subpart A
   • B14 CFR Part 61
   • 14 CFR 107 Subpart CCorrect
   • D14 CFR 107 Subpart B

   Why it traps people

   Part 61 is the certification rule for manned pilots, so it feels right. Remote pilot certification lives inside Part 107 itself: Subpart A is general (applicability, definitions), Subpart B is operating rules, Subpart C is certification (107.53 to 107.79), Subpart D is operations over people.

   The answer, explained

   Remote pilot certification requirements are found in 14 CFR 107 Subpart C (Remote Pilot Certification). This covers eligibility (107.61), knowledge test requirements (107.63), recurrent training (107.65), and knowledge and training requirements (107.74).

   Source: 14 CFR part 107, subpart C · Question written by Rotate Pilot

5. #5Airspace Classification and Operating RequirementsUA.II.A.K3

   83% missed it: 10 of 12 learners got it wrong at least once (15 answers in total)

   National Security Areas (NSAs) on a sectional chart require what from drone pilots?

   • ANo special considerations or avoidance procedures are ever required near NSAs
   • BMandatory avoidance is always required at all times regardless of any NOTAM, since pilots have no discretion in this matter.
   • CATC authorization is required only during daytime flight operations nearby
   • Voluntary avoidance is requested; the FAA may make compliance mandatory via NOTAMCorrect

   Why it traps people

   "Always mandatory" sounds like the safe answer. National Security Areas only request voluntary avoidance; flight there becomes prohibited only when the FAA issues a temporary restriction under 14 CFR 99.7, published by NOTAM. Read every option to the end: the absolute wording is the trap.

   The answer, explained

   National Security Areas request voluntary avoidance of flight. However, the FAA may issue a NOTAM or regulation making compliance mandatory during heightened security periods. NSAs are depicted on sectional charts and drone pilots should plan to avoid them.

   Source: AIM 3-5-7 (National Security Areas); 14 CFR 99.7 · Question written by Rotate Pilot

6. #6Airspace Classification and Operating RequirementsUA.II.A.K2

   82% missed it: 9 of 11 learners got it wrong at least once (16 answers in total)

   What is a Controlled Firing Area (CFA)?

   • AAn area where ATC actively controls all air traffic due to ongoing firing activity
   • BAn area shown on sectional charts where military weapons firing normally occurs
   • An area not charted where activities are suspended when spotters detect approaching aircraftCorrect
   • DAn area where all drone flight operations are directly controlled by the military

   Why it traps people

   People lump CFAs together with restricted and warning areas, which are charted. A Controlled Firing Area is never charted, because the activity stops whenever a spotter, radar or ground lookout sees an aircraft approaching.

   The answer, explained

   Controlled Firing Areas are unique because they are NOT depicted on sectional charts. Activities within CFAs (such as weapons firing) are suspended when a spotter or radar detects an approaching aircraft. Because the activity ceases, there is no need to chart them.

   Source: AIM 3-4-8 (Controlled Firing Areas) · Question written by Rotate Pilot

7. #7Airspace Classification and Operating RequirementsUA.II.A.K1d

   80% missed it: 8 of 10 learners got it wrong at least once (21 answers in total)

   A magenta vignette (shading) fading outward on a sectional chart indicates Class E airspace begins at what altitude?

   • 700 feet AGLCorrect
   • B500 feet AGL
   • C1,200 feet AGL
   • D1,500 feet AGL

   Why it traps people

   1,200 ft AGL is the number most people remember for Class E, so it wins. A magenta vignette marks Class E starting at 700 ft AGL around an airport with instrument approaches; the blue vignette is the 1,200 ft AGL version.

   The answer, explained

   A magenta vignette fading outward from a circle indicates Class E airspace begins at 700 feet AGL. This is commonly found around airports with instrument approaches but without an operating control tower. The vignette helps pilots identify where controlled airspace starts at a lower altitude.

   Source: FAA Aeronautical Chart User's Guide; AIM 3-2-6 · Question written by Rotate Pilot

8. #8Airspace Classification and Operating RequirementsUA.II.A.K1a

   80% missed it: 8 of 10 learners got it wrong at least once (19 answers in total)

   On a sectional chart, what does a thick blue line forming an irregular polygon around a city represent?

   • AA radar service area
   • BThe Mode C veil
   • Class B airspaceCorrect
   • DA city boundary line

   Why it traps people

   The Mode C veil and Class C get mixed in. On a sectional, solid blue lines are Class B, solid magenta lines are Class C, dashed blue is Class D, and the Mode C veil is a thin magenta circle 30 NM out.

   The answer, explained

   Thick solid blue lines forming irregular shapes represent Class B airspace boundaries on a sectional chart. These often form the characteristic 'upside-down wedding cake' shape around major metropolitan airports. Each segment has floor and ceiling altitudes noted.

   Source: FAA Aeronautical Chart User's Guide; AIM 3-2-3 · Question written by Rotate Pilot

9. #9Airspace Classification and Operating RequirementsUA.II.A.K1c

   75% missed it: 9 of 12 learners got it wrong at least once (13 answers in total)

   You're planning a drone flight 0.5 NM from a Class D airport. The tower is currently closed for the night. Do you need authorization?

   • ANo, a closed tower always converts the airspace to uncontrolled Class G immediately
   • It depends on whether the airspace reverts to Class E surface or Class GCorrect
   • CYou need authorization only if your flight occurs above 400 feet AGL
   • DYes, Class D airspace stays active even when the tower is closed for the night

   Why it traps people

   Both absolute answers feel confident and both are wrong. When the tower closes, the Class D surface area reverts to Class E or Class G depending on the airport; the Chart Supplement says which. If it becomes Class E to the surface you still need authorization under 107.41.

   The answer, explained

   When a tower closes, Class D airspace typically reverts to either Class E surface (requiring authorization) or Class G (no authorization needed). Check the Chart Supplement for the specific airport to determine what airspace class applies when the tower is closed.

   Source: 14 CFR 107.41; AIM 3-2-5; Chart Supplement · Question written by Rotate Pilot

10. #10Airspace Classification and Operating RequirementsUA.II.A.K1b

    73% missed it: 8 of 11 learners got it wrong at least once (22 answers in total)

    What is the outer area of Class C airspace, and does it require ATC authorization for drone flights?

    • A 20 NM ring where participation is voluntary for manned aircraft; drone pilots should exercise cautionCorrect
    • BA 5 NM ring around the airport that is classified as uncontrolled Class G airspace
    • There is no outer area for Class C airspace; it only exists for Class B airspaceMost-picked wrong answer (2 of 4 recorded wrong picks)
    • DA 20 NM ring requiring mandatory two-way radio contact with air traffic control before entering

    Why it traps people

    The outer area is not drawn on the chart, so many decide it does not exist. Class C has a 5 NM core, a 10 NM shelf and, normally, a 20 NM outer area where radio contact is encouraged but not required. For a drone, what matters is the airspace class underneath.

    The answer, explained

    The outer area of Class C extends to approximately 20 NM and is not depicted on charts. For manned aircraft, two-way radio communication is encouraged but not required. For drone pilots, the outer area is typically Class E or G airspace, so LAANC/ATC authorization depends on the underlying airspace classification.

    Source: AIM 3-2-4 (Class C airspace) · Question written by Rotate Pilot

11. #11Airspace Classification and Operating RequirementsUA.II.A.K1a

    69% missed it: 9 of 13 learners got it wrong at least once (16 answers in total)

    What is the Mode C veil?

    • AA requirement for all small unmanned aircraft to carry Mode C transponders when flying above 400 feet AGL
    • BA 10 NM ring around Class C airports requiring transponders for manned aircraft below 10,000 feet MSL
    • CA cloud layer that affects radar coverage and requires manned pilots to file an instrument flight plan
    • A 30 NM ring around Class B airports requiring transponders for manned aircraft; drone pilots should be aware of heavy trafficCorrect

    Why it traps people

    The 10 NM option borrows the Class C shelf. The Mode C veil is 30 NM around the primary Class B airport, from the surface to 10,000 ft MSL, where manned aircraft need a transponder. Your drone does not: Part 107 actually prohibits transponders and ADS-B Out unless authorized.

    The answer, explained

    The Mode C veil extends 30 NM from the primary Class B airport and requires manned aircraft to have Mode C transponders. While drones don't need transponders, drone pilots should be aware that this area has heavy manned aircraft traffic. The veil is shown on charts as a thin magenta circle.

    Source: 14 CFR 91.215(b)(2); 14 CFR 107.52 and 107.53 · Question written by Rotate Pilot

12. #12Airspace Classification and Operating RequirementsUA.II.A.K3

    69% missed it: 9 of 13 learners got it wrong at least once (17 answers in total)

    Where is the Washington DC Flight Restricted Zone (FRZ)?

    • Within a 15 NM radius of DCACorrect
    • BWithin a 15-30 NM ring around DCA
    • CWithin a 30 NM radius of DCA
    • DWithin a 60 NM radius of DCA

    Why it traps people

    30 NM is the other DC number: the Special Flight Rules Area. The Flight Restricted Zone is the inner ring, about 15 NM around Reagan National (DCA), where drone flights are prohibited without specific FAA and security authorization.

    The answer, explained

    The Washington DC FRZ extends approximately 15 NM from Reagan National Airport (DCA). All aircraft operations, including drones, are prohibited in the FRZ without specific authorization. The broader Special Flight Rules Area (SFRA) extends to 30 NM.

    Source: 14 CFR part 93, subpart V (Washington, DC SFRA) · Question written by Rotate Pilot

13. #13Airspace Classification and Operating RequirementsUA.II.A.K1b

    67% missed it: 10 of 15 learners got it wrong at least once (28 answers in total)

    What is the typical vertical extent of Class C airspace?

    • Surface to 4,000 feet AGLCorrect
    • BSurface to 10,000 feet MSL
    • CSurface to 2,500 feet AGL
    • DSurface to 1,200 feet AGL

    Why it traps people

    10,000 ft MSL is the usual Class B ceiling and 2,500 ft is Class D, so the numbers blur. Class C normally goes from the surface to 4,000 ft above the airport elevation (charted in MSL).

    The answer, explained

    Class C airspace typically extends from the surface to 4,000 feet AGL. It consists of a 5 NM inner circle from surface to 4,000 feet AGL and a 10 NM outer shelf from 1,200 feet AGL to 4,000 feet AGL. Exact dimensions are charted on the sectional.

    Source: AIM 3-2-4 (Class C airspace) · Question written by Rotate Pilot

14. #14WeatherUA.III.B.K1i

    70% missed it: 7 of 10 learners got it wrong at least once (16 answers in total)

    What type of fog is most likely to form on a clear, calm night with high humidity?

    • Radiation fogCorrect
    • BUpslope fog
    • CAdvection fog
    • DGround fog

    Why it traps people

    Clear, calm and humid is the textbook recipe for radiation fog: the ground cools overnight and chills the air above it to its dew point. Advection fog needs wind to move moist air over a cold surface; upslope fog needs wind blowing up terrain. Very shallow radiation fog is called ground fog, but the process the question asks for is radiation.

    The answer, explained

    Radiation fog forms on clear, calm nights when the ground radiates heat and cools the adjacent air to its dewpoint. High humidity (small temperature-dewpoint spread) makes formation more likely. Radiation fog is typically a few hundred feet thick and dissipates after sunrise as the ground warms.

    Source: FAA-H-8083-28 Aviation Weather Handbook (fog) · Question written by Rotate Pilot

15. #15Airspace Classification and Operating RequirementsUA.II.B.K4a

    70% missed it: 7 of 10 learners got it wrong at least once (14 answers in total)

    What does the acronym 'CFIT' stand for and how does it apply to drones?

    • Controlled Flight Into Terrain — when an airworthy aircraft is flown into the ground or an obstacle under the pilot's controlCorrect
    • BController Failure In Terrain — a hardware malfunction that causes the aircraft to lose all control inputs during flight
    • CCommunication Failure In Transit — a temporary loss of the control link between the pilot and aircraft during flight
    • DCertified Flight Instructor Training — a mandatory course required before operating any unmanned aircraft commercially

    Why it traps people

    The distractors are invented acronyms built to sound technical. CFIT is Controlled Flight Into Terrain: a perfectly working aircraft flown into the ground, water or an obstacle because the pilot lost track of where it was. For drones that is usually a tree, a wire or a building at the edge of visual range.

    The answer, explained

    Controlled Flight Into Terrain (CFIT) occurs when an operational aircraft is inadvertently flown into terrain, water, or an obstacle. For drones, this can happen due to altitude errors, flying too close to terrain, loss of situational awareness, or GPS altitude inaccuracies. Proper altitude awareness and obstacle avoidance are critical.

    Source: FAA-H-8083-2 Risk Management Handbook · Question written by Rotate Pilot

16. #16Loading and PerformanceUA.IV.A.K2

    64% missed it: 7 of 11 learners got it wrong at least once (14 answers in total)

    A drone has 4 motors, each producing a maximum of 10 lbs of thrust. The drone with payload weighs 25 lbs. What is the thrust-to-weight ratio?

    • 1.6:1Correct
    • B0.625:1
    • C4:1
    • D2.5:1

    Why it traps people

    Dividing the wrong way gives 0.625:1. Thrust-to-weight is total thrust over weight: 4 x 10 lb = 40 lb, and 40 / 25 = 1.6:1. This one is our own practice question (the FAA does not test this exact ratio), but the skill, reading what a load does to performance, is in the loading and performance area.

    The answer, explained

    Total thrust = 4 motors x 10 lbs = 40 lbs. Thrust-to-weight ratio = 40/25 = 1.6:1. This means the drone can produce 1.6 times its own weight in thrust. While flyable, this is below the recommended 2:1 ratio, meaning the drone will have limited maneuverability and wind resistance, and may struggle in high density altitude.

    Source: ACS UA.IV.A (Loading and Performance) · Question written by Rotate Pilot

17. #17Airspace Classification and Operating RequirementsUA.II.A.K2

    60% missed it: 6 of 10 learners got it wrong at least once (17 answers in total)

    On a sectional chart, how are Prohibited areas depicted?

    • AMagenta hatched lines with a 'P' designation
    • BRed hatched lines with an 'R' designation
    • CBlue hatched lines with a 'P' and an airport symbol
    • Blue hatched lines with a 'P' designationCorrect

    Why it traps people

    Magenta hatching is for Military Operations Areas, so it gets confused. Prohibited, restricted and warning areas are all drawn with blue hatched borders; the letter (P, R, W) and number tell them apart, as in P-56 over Washington, DC.

    The answer, explained

    Prohibited areas are depicted on sectional charts with blue hatched lines and are labeled with a 'P' followed by a number (e.g., P-56). The details of the prohibition, including altitude limits, are found in the chart margin or Chart Supplement.

    Source: FAA Aeronautical Chart User's Guide; AIM 3-4-2 · Question written by Rotate Pilot

18. #18RegulationsUA.I.E.K3

    60% missed it: 6 of 10 learners got it wrong at least once (11 answers in total)

    Under Part 107, is it legal to fly a drone directly over a person not participating in the operation?

    • ANo, flying over non-participants is prohibited under all circumstances
    • Only with drones meeting Category 1, 2, 3, or 4 requirements under Subpart DCorrect
    • COnly if the remote pilot obtains written consent from each individual
    • DYes, any drone may fly over people regardless of weight or category

    Why it traps people

    "Prohibited under all circumstances" was the rule before April 2021, and older study material still says it. Today Subpart D allows flight over people with a drone that meets Category 1, 2, 3 or 4 (each with its own limits), and 107.39 also allows it over people under a covered structure or inside a stationary vehicle.

    The answer, explained

    Per 14 CFR 107 Subpart D (Operations Over People), flying over non-participating persons requires the small UAS to meet one of four categories based on weight, kinetic energy, or airworthiness. Each category has specific requirements to minimize risk of injury.

    Source: 14 CFR 107.39; 14 CFR part 107, subpart D · Question written by Rotate Pilot

19. #19Airspace Classification and Operating RequirementsUA.II.A.K1d

    55% missed it: 6 of 11 learners got it wrong at least once (21 answers in total)

    A dashed magenta line on a sectional chart surrounding an airport indicates what?

    • AProhibited area boundary near restricted airspace
    • Class E airspace extending to the surfaceCorrect
    • CClass D airspace boundary near a towered airport
    • DClass C airspace outer shelf area

    Why it traps people

    Dashed lines make people think of Class D, which is dashed BLUE. A dashed MAGENTA line is Class E that starts at the surface. It is still controlled airspace, so you need an authorization (LAANC or DroneZone) to fly there.

    The answer, explained

    A dashed magenta line on a sectional chart indicates Class E airspace that extends to the surface. This is typically found around non-towered airports with instrument approaches. Drone operators need LAANC or ATC authorization to fly in this surface-level Class E airspace.

    Source: FAA Aeronautical Chart User's Guide; 14 CFR 107.41 · Question written by Rotate Pilot

20. #20Airspace Classification and Operating RequirementsUA.II.B.K2

    55% missed it: 6 of 11 learners got it wrong at least once (16 answers in total)

    Under LAANC, what is a 'UASFM grid'?

    • AA national grid system used for tracking all currently active drone flights
    • A pre-approved altitude grid near airports showing maximum allowed drone altitudesCorrect
    • CA grid showing designated drone registration zones near controlled airports
    • DA grid system required for reporting all drone accidents and incidents

    Why it traps people

    "Grid" sounds like tracking or registration. A UAS Facility Map divides the area around an airport into cells, each with the maximum altitude LAANC can approve automatically. A 0 ft cell means no automatic approval: you request it further through DroneZone.

    The answer, explained

    The UAS Facility Map (UASFM) grid divides the area around airports into cells with pre-approved maximum altitudes for drone operations. LAANC uses these grids to automatically approve requests at or below the published ceiling. Some cells may show 0 feet, meaning no operations are approved.

    Source: FAA UAS Facility Maps; 14 CFR 107.41 · Question written by Rotate Pilot

21. #21Airspace Classification and Operating RequirementsUA.II.A.K1b

    55% missed it: 6 of 11 learners got it wrong at least once (14 answers in total)

    What is the standard radius of the inner circle of Class C airspace?

    • A3 NM
    • 5 NMCorrect
    • C10 NM
    • D15 NM

    Why it traps people

    Class C has three rings and each has a famous number: 5 NM (the core, surface to 4,000 ft above the airport), 10 NM (the shelf, from 1,200 ft) and 20 NM (the outer area). The question asks for the inner circle: 5 NM.

    The answer, explained

    The inner circle (surface area) of Class C airspace typically extends 5 nautical miles from the primary airport. This inner area extends from the surface to usually 4,000 feet AGL. The outer shelf extends from 1,200 feet AGL to the ceiling at 10 NM.

    Source: AIM 3-2-4 (Class C airspace) · Question written by Rotate Pilot

22. #22WeatherUA.III.B.K1i

    50% missed it: 6 of 12 learners got it wrong at least once (14 answers in total)

    What is advection fog?

    • AFog formed over bodies of unusually warm water surfaces
    • BFog formed by air rising and cooling along a mountain slope
    • CFog formed by ground radiation cooling on clear, calm nights
    • Fog formed when warm, moist air moves over a cooler surfaceCorrect

    Why it traps people

    Advection and radiation fog both need air cooled to its dew point, so the descriptions blur. Advection means the air moves: warm, moist air blown over a colder surface, typical of coasts, and it can form with wind and at any hour. Radiation fog needs calm, clear nights.

    The answer, explained

    Advection fog forms when warm, moist air moves horizontally over a cooler surface, cooling the air to its dewpoint. It is common along coastlines where warm ocean air moves over cold land or cold ocean currents. Unlike radiation fog, advection fog can form at any time and in windy conditions.

    Source: FAA-H-8083-28 Aviation Weather Handbook (fog) · Question written by Rotate Pilot

23. #23RegulationsUA.I.B.K21b

    50% missed it: 6 of 12 learners got it wrong at least once (19 answers in total)

    You are hired to inspect a 500-foot tall communications tower. What is the maximum altitude you can fly your drone?

    • A400 feet AGL
    • B500 feet AGL
    • C1,000 feet AGL
    • 900 feet AGLCorrect

    Why it traps people

    People stop at the 400 ft rule or at the tower's height. 107.51(b) lets you fly higher than 400 ft AGL if you stay within a 400 ft radius of a structure and no more than 400 ft above its uppermost limit: 500 + 400 = 900 ft AGL.

    The answer, explained

    Per 14 CFR 107.51(b), you may fly up to 400 feet above a structure as long as you remain within a 400-foot radius of it. A 500-foot tower plus 400 feet equals 900 feet AGL maximum altitude. You must remain within 400 feet laterally of the structure.

    Source: 14 CFR 107.51(b) · Question written by Rotate Pilot

24. #24WeatherUA.III.B.K1c

    50% missed it: 6 of 12 learners got it wrong at least once (15 answers in total)

    What is standard atmospheric pressure at sea level?

    • A31.00 inches of mercury (1050 hPa/mb)
    • B30.50 inches of mercury (1033 hPa/mb), common in winter
    • C28.92 inches of mercury (979 hPa/mb)
    • 29.92 inches of mercury (1013.2 hPa/mb)Correct

    Why it traps people

    The distractors use real-looking pressures (a strong winter high, a deep low). Standard sea-level pressure is 29.92 inHg, 1013.2 hPa, at 15 °C. It is also the altimeter setting everyone uses at and above 18,000 ft MSL.

    The answer, explained

    Standard atmospheric pressure at sea level is 29.92 inches of mercury (inHg), which equals 1013.2 hectopascals (hPa) or millibars (mb). This is the baseline used for altitude calculations and is the default altimeter setting for flight above 18,000 feet MSL (Class A airspace).

    Source: FAA-H-8083-25 Pilot's Handbook of Aeronautical Knowledge (standard atmosphere); 14 CFR 91.121 · Question written by Rotate Pilot

25. #25WeatherUA.III.B.K1b

    50% missed it: 6 of 12 learners got it wrong at least once (16 answers in total)

    You're flying a drone in an area where the surface wind is calm but at 300 feet AGL you encounter strong winds. What phenomenon might explain this?

    • AA high pressure system directly overhead
    • BYour drone's GPS-based windspeed estimate is malfunctioning
    • A low-level wind shear or decoupled boundary layerCorrect
    • DThis situation cannot physically occur in the atmosphere

    Why it traps people

    Calm on the ground feels like proof that it is calm everywhere, so "cannot occur" or "GPS error" get picked. A temperature inversion can decouple the surface air from the wind above it, and the wind can change sharply within a few hundred feet. Climb slowly and watch the drone's attitude and battery.

    The answer, explained

    A decoupled boundary layer or low-level wind shear can cause dramatically different wind conditions between the surface and just a few hundred feet up. Temperature inversions often create this effect by decoupling the surface layer from winds aloft. Drone pilots should ascend slowly to check for wind shear.

    Source: FAA-H-8083-28 Aviation Weather Handbook (wind shear, inversions) · Question written by Rotate Pilot

Frequently asked questions