Task VI.C
Diversion
To determine the applicant exhibits satisfactory knowledge, risk management, and skills associated with diversion.
References: AIM; FAA-H-8083-2, FAA-H-8083-3, FAA-H-8083-25; VFR Navigation Charts
Quick Review
Conversational Q&A — quiz yourself before the oral.
The tolerances (CA.VI.C.S1–S6):
- Select a suitable destination and route
- Estimate heading, groundspeed, arrival time, and fuel required to the divert-to destination
- Maintain altitude ±100 feet and heading ±10°
- Update and interpret weather in flight
- Use displays of digital weather and aeronautical information to maintain situational awareness
- Promptly divert toward the destination
Read S6 next to S2 and the priority is obvious: turn first, compute second. The ±100/±10° applies while you are doing the arithmetic.
PHAK 16-35 is explicit: "in an emergency, divert promptly toward your alternate destination. Attempting to complete all plotting, measuring, and computations involved before diverting to the alternate destination may only aggravate an actual emergency."
The sequence is: turn toward the airport, note the time, then work the numbers while established on the new heading. PHAK adds that if time permits you should try to start the diversion over a prominent ground feature — it gives you a clean origin for the dead reckoning that follows.
PHAK 16-34 lists the general causes: unpredicted weather conditions, a system malfunction, or poor preflight planning. In practice, name them concretely:
- Weather ahead or at the destination below what you can legally or safely accept — the classic VFR into IMC setup PHAK names as the risk to mitigate "through a pre-planned or in-flight diversion around hazardous weather"
- Fuel trending toward the 91.151 reserve given your measured groundspeed
- An engine, electrical, or vacuum indication that is not resolving
- A passenger or crew medical issue
- Destination runway, lighting, or airport closure — a NOTAM you were not given
- Daylight: arriving after dark without night currency or a lit runway
Professional framing: the diversion is a decision you make while you still have options, not one the airplane makes for you.
Nearest suitable is not nearest. Work the list:
- Runway length, width, surface, and alignment with the wind for your actual weight and density altitude
- Weather at the field and the trend, plus terrain and airspace between you and it
- Fuel and services if the diversion is fuel-driven — a closed FBO does not solve a fuel problem
- Approach and lighting if daylight or ceiling is marginal
- Navigation: PHAK 16-34 notes "it is typically easier to navigate to an alternate airport that has a VOR or NDB facility on the field"
- Getting your passengers onward — a commercial consideration the private ride never asked about
PHAK 16-34 also expects this to be partly pre-work: "before any cross-country flight, check the charts for airports or suitable landing areas along or near the route of flight. Also, check for navigational aids that can be used during a diversion."
PHAK says plotting a course in flight "is rarely practical," and because an alternate is usually not far off your original course, "actual plotting is seldom necessary." The approved shortcuts: measure with a straightedge against the compass rose printed around a VOR, or use a radial from a nearby VOR or an airway that closely parallels the course to your alternate.
One trap the handbook flags: the magnetic heading associated with a VOR radial or a printed airway is outbound from the station — to find the course to the station you may need the reciprocal.
The sequence is time → wind → heading and groundspeed → ETA → fuel required, then compare fuel required against fuel on board with the 30-minute day / 45-minute night reserve still intact (91.151).
PHAK 16-35: "Once established on course, note the time, and then use the winds aloft nearest to your diversion point to calculate a heading and GS. Once a GS has been calculated, determine a new arrival time and fuel consumption." And the standing rule: "Give priority to flying the aircraft while dividing attention between navigation and planning."
PHAK 16-35: "when determining an altitude to use while diverting, consider cloud heights, winds, terrain, and radio reception."
Add the commercial reading: an altitude that keeps you legal for VFR cloud clearance in the airspace you are entering, gives terrain and glide options, gets you the best groundspeed for the fuel you have, and keeps you inside radar and VOR line-of-sight coverage so ATC can help. Climbing also buys reception range — the same logic as lost procedures (PHAK 16-34).
Sources, best first:
- ATIS/AWOS/ASOS at the candidate field
- Flight Service on a published frequency
- ATC for what they are seeing and hearing from other aircraft
- Datalink weather on the EFB or panel display
Interpretation discipline the examiner is listening for: datalink radar is not real time — treat the mosaic as a strategic picture with an age stamp, not a tactical avoidance tool, and never use it to thread between cells. Compare the METAR trend against the TAF you briefed and against what you can see out the window. If the observed weather is worse than what was forecast, the whole forecast is suspect, not just that one field.
- ATC — say the words. A request for vectors to the nearest suitable airport, a frequency for the field, or a radar position is free and immediate (PHAK 14-26).
- Automation — direct-to on the GPS gives you course, distance, groundspeed, and ETE in one keystroke; cross-check it against the sectional and your DR before you commit.
- EFB — nearest-airport function, Chart Supplement, and airport diagram, with the currency caveats from Task VI.B.
- The airplane — fuel totalizer and gauges, and the clock.
- Your passengers, if you have a competent one, for spotting traffic and reading numbers.
The failure mode the examiner is watching for is a pilot heads-down in a tablet, silent, at 400 feet off altitude.
No clearance to break on a plain VFR flight — you may divert at will, though if you are on flight following you tell ATC.
VFR flight plan active: 91.153(b) requires that on canceling or completing the flight you notify an FAA Flight Service Station or ATC facility — close it, or search and rescue is launched for you. Amending the route or destination en route is not a regulatory requirement, but the AIM asks you to keep FSS informed so the SAR clock stays accurate.
Constrained by clearance or instruction — a Class B or C clearance, an assigned heading or altitude under radar service: you request the deviation and get an amended instruction.
Emergency: 91.3(b) lets the PIC deviate from any rule of part 91 to the extent required to meet that emergency; expect to be asked to explain what you did as soon as workload permits.
Deep Dive
The in-flight arithmetic, done in under a minute
The examiner will pick the moment — usually just after they have given you a distraction — point at a field, and say "divert." What follows is the whole task.
- Nautical miles per minute: groundspeed ÷ 60. At 120 kt that is 2 NM per minute, so 38 NM is about 19 minutes; at 90 kt it is 1.5 NM per minute. Use it to sanity-check whatever the GPS or the whiz wheel tells you.
- Latitude ticks are a ruler: one minute of latitude equals one nautical mile, so you can measure without a plotter.
- Fuel in minutes, not gallons. Convert gallons on board to minutes at your cruise burn and compare against time to the field plus reserve — it is the comparison that actually matters, and it removes a conversion step under stress.
- Round conservatively. Round distance up, groundspeed down, burn up. PHAK 16-34 endorses "all possible shortcuts and rule-of-thumb computations" in the cockpit; the professional version rounds in the direction that cannot hurt you.
The diversion is a high-workload, head-down, off-plan segment through airspace you did not brief — which is exactly the profile of a midair or an airspace bust.
- Aviate, navigate, communicate, then compute. Set the heading and altitude, trim, then pick up the pencil.
- Look outside between every step. Eyes in for a few seconds, eyes out for the rest.
- Get flight following if you do not already have it, so someone else is watching the target (PHAK 14-26).
- Brief the airspace on the new track before you cross it — a diversion frequently steers you into a Class C shelf or under a Class B floor that was not on the planned route.
- Terrain: the direct line is not always the safe line; sector minimums and MEFs on the sectional still apply, and the diversion altitude is a decision, not a leftover.
It does not change the decision — it changes the pressure on it, and naming that pressure is the professional-pilot answer the examiner wants.
The commercial certificate is where external pressure first becomes real: a schedule, a fee, a passenger's opinion, an operator's expectation. The mitigations are structural, not heroic — brief the passengers before departure that weather may require a change, set personal minimums and diversion trigger points on the ground where nobody is watching the clock, and set a bingo fuel number before takeoff so the diversion decision is arithmetic rather than judgment when it arrives.
If the diversion is made, sell it as the plan working, not the plan failing.
Official ACS elementsreference
Knowledge2 elements
The applicant demonstrates understanding of:
CA.VI.C.K1Selecting an alternate destination.CA.VI.C.K2Situations that require deviations from flight plan or air traffic control (ATC) instructions.
Risk Management5 elements
The applicant is able to identify, assess, and mitigate risk associated with:
CA.VI.C.R1Collision hazards.CA.VI.C.R2Distractions, task prioritization, loss of situational awareness, or disorientation.CA.VI.C.R3Circumstances that would make diversion prudent.CA.VI.C.R4Selecting an appropriate airport or seaplane base.CA.VI.C.R5Using available resources (e.g., automation, ATC, and flight deck planning aids).
Skills6 elements
The applicant exhibits the skill to:
CA.VI.C.S1Select a suitable destination and route for diversion.CA.VI.C.S2Make a reasonable estimate of heading, groundspeed, arrival time, and fuel required to the “divert to” destination.CA.VI.C.S3Maintain the appropriate altitude, ±100 feet and heading, ±10°.CA.VI.C.S4Update/interpret weather in flight.CA.VI.C.S5Use displays of digital weather and aeronautical information, as applicable to maintain situational awareness.CA.VI.C.S6Promptly divert toward the destination.