Flight Performance & Planning

01 · Scope and categories

The SACAA CPL(A) outline separates performance classification, certification, flight stages, charts, mass and balance, and flight planning. It names Parts 91 and 135, and CAP 696/697/698. [1]

Keep three layers apart: the certified aircraft limit, an operating rule for its class, and a chart result for today's conditions. Class A, B and C rules are not interchangeable. A type's AFM/POH, approved performance data and the question's named regulation control the answer.

Trap: A study-manual factor does not apply to every aircraft or current operation. The CAP books are legacy exam datasets.

Quiz theory: what is being limited?

• Structural limit is in the aircraft's approved data; it is not a promise that this mass can depart on a hot, high or short runway. Performance-limited mass may be lower because of take-off, climb, obstacle or landing constraints. The allowable mass is the lowest applicable limit. Q343, Q347, Q375, Q377 and Q513.
• Class A, B and C performance schemes use different assumptions and margins. In an exam, identify the class and cited CAP figure before using a factor. This sheet's SEP worked factors belong to the named CAP 698 case only. [1] [4]
• Separate certification definitions (e.g. V1, V2), operational planning (fuel and payload), and aircraft-specific chart readings. Never promote an answer highlighted in a questionnaire into an aircraft limitation.

02 · Atmosphere and airspeed

Use the chart or flight computer for density altitude and TAS. High altitude, high temperature and low pressure increase density altitude. This usually hurts take-off and climb. IAS is indicated speed; CAS corrects instrument and position error; TAS is speed through air; GS is speed over ground. [1] [7]

Trap: The 30 ft/hPa and 2°C/1,000 ft figures are approximations. Never replace the assigned chart with them.

Quiz theory: ISA, pressure, density and aerodynamic speeds

• ISA supplies a standard sea-level pressure and temperature and a standard temperature lapse rate. Actual air can differ. Pressure altitude is the altitude corresponding to standard pressure (1013.25 hPa), not an adjustment for the actual temperature. Density altitude combines pressure and temperature effects on density. Q106, Q123, Q490, Q507, Q510, Q556 and Q559. [7]
• On a high-density-altitude day, at the same indicated speed the aircraft normally has a higher TAS and groundspeed at lift-off, needs more runway, and has less engine/propeller and climb performance. Lower pressure altitude generally improves take-off/climb if other conditions stay fixed. Q9 and Q70. [7]
• With increased aircraft mass or load factor, required lift and stalling speed increase. For unchanged density, configuration and maximum lift coefficient, VS₂/VS₁ = √(W₂/W₁) and VS in a coordinated level turn = VS(1g) × √n, with n = 1/cos(bank angle). In a turn, induced drag rises too. Q166, Q176, Q502 and Q554. [11]
• With more flap, maximum lift coefficient normally rises and stall speed falls, but added drag can hurt climb. Configuration matters when comparing any two V-speeds; don't infer a universal fixed speed shift from a flap change. Q113, Q164, Q188 and Q204. [7]

03 · V-speeds

V1 is the take-off decision speed. VMCG is minimum control speed on the ground. VMCA is minimum control speed in air. VR is rotation speed. VLOF is lift-off speed. V2 is take-off safety speed. VMU is minimum unstick speed. VMBE is brake-energy-limited speed. [5]

CS-25 VREF in a non-icing landing is at least the greatest applicable minimum, including 1.23 × VSR0 and VMCL. VSR0 is the reference stall speed in landing configuration. Use the applicable certification basis and AFM. [5]

Other speed cues: VX best angle; VY best rate; VA manoeuvring; VFE flap-extended limit; VLO gear-operating limit; VLE gear-extended limit; VNO maximum structural cruise; VNE never exceed; VMO maximum operating. [1] [7]

Trap: Do not turn every V2MIN or VREF case into one memorised multiplier. VSR and VS0 are different definitions. V1 is not VEF.

Quiz theory: decision, control and speed schedules

• VEF is the assumed critical-engine failure speed; V1 includes recognition/decision delay in certification calculations. The model imposes VEF ≥ VMCG and V1 ≥ VEF; VR ≥ V1. The exact relationship to VLOF and V2 depends on the aircraft certification model and acceleration. Q14–22, Q90–104 and Q109. [5]
• Below V1 for a recognized engine failure, the conventional take-off calculation assumes reject; at or above V1 it assumes continued take-off. These are exam-model assumptions, not blanket real-flight instructions for every malfunction. With more stopway or clearway, selected V1 may change because stop/go constraints change. Q5–10, Q122, Q125–137. [5]
• VMCG concerns maintaining ground directional control after critical engine failure with aerodynamic controls; VMCA is airborne directional control, not proof of a positive climb. The critical engine is the one whose loss most adversely affects control/performance. Critical-engine failure conditions and asymmetric thrust matter. Q107, Q180, Q187 and Q227. [12]
• V2 is safety speed following engine failure during take-off; VREF is landing reference speed. Gust additives to approach speed must follow aircraft instructions, and additional speed lengthens landing distance. Tyre rotational limit tracks ground speed at lift-off, not just indicated V1. Q140, Q144, Q145, Q189. [5] [12]
• VMD is minimum-drag speed, associated with best L/D and best still-air glide angle; VMP is minimum-power speed in the usual propeller-aircraft power curve. On the slow side of the power curve, slower flight needs more power to hold height. Q161, Q167, Q175 and Q208. [11]

Source-key warning: the source-marked answers to quiz Q201 and Q207 disagree on how VX changes with altitude. Do not memorize both; use the aircraft-specific performance chart and distinguish IAS, CAS and TAS. Several source marks were not independently checked.

04 · Declared distances

A clearway supports take-off climb, not ground roll or stopping. A stopway supports a rejected take-off, not climb or landing. Compare each required distance with its matching available distance. [6]

Displaced threshold (Q478): It reduces only LDA for an approach to that threshold. It leaves the reciprocal direction's declared distances unaffected. Check any additional published restrictions for the runway. [6]

Trap: Do not subtract a threshold displacement from both directions, or assume TODA/ASDA equal runway length when a clearway/stopway is declared.

Quiz theory: runway surfaces and what counts

• Stopway adds ASDA only; clearway adds TODA only; TORA concerns the take-off run and LDA the landing ground run in the specified direction. The figures need not equal the physical paved runway length. Q8, Q48–55, Q122 and Q500. [6]
• Displaced threshold: for the approach to that threshold, the displaced portion is not available as landing distance, though it may remain available to take off or to land in the opposite direction if published data permits. Read direction-specific declared distances rather than apply a displacement to every direction. Q478. [6]
• Wet, slush or contaminated runways are not simply "dry with a multiplier." Classification thresholds and performance penalties depend on the named regulation, aircraft data, contaminant depth and braking assumptions. Q105 and Q210 are source-marked quiz items, not universal wet-runway policy. [4]

05 · Take-off and landing

Take-off ground roll ends at lift-off. Take-off distance includes the airborne segment to its stated screen height. Accelerate-stop covers acceleration, failure recognition and stopping. Accelerate-go covers continued take-off after the specified failure. A balanced field makes the limiting accelerate-go and accelerate-stop distances equal, under the assigned method. [4] [5]

These factors are CAP 698 SEP exercise rules, not generic Class A/B/C rules. Check the section, runway surface, wind and wet-runway corrections before comparing. Wind allowance is not necessarily 100% of forecast headwind. [4]

Trap: A 50 ft screen-height landing distance is not the same as ground roll. Do not apply ×1.43 to a result already factored.

Quiz theory: stop/go, segments, runway effects

• Balanced field has two exam usages. For a balanced-field take-off calculation, selected V1 makes accelerate-stop and accelerate-go required distances meet under the stated assumptions. In some runway-declaration questions, a balanced runway/field instead means ASDA = TODA (equal available distances); this is the usage in the source-marked quiz Q505. Read whether the question is comparing required performance or available declared distances. Neither equality says required distance must equal available distance. Q7, Q46, Q95, Q136 and Q505. [5] [6]
• A higher chosen V1 generally increases accelerate-stop required and decreases the remaining acceleration after failure for accelerate-go; runway length, slope, surface, brakes and failure speed affect the balance. A downhill take-off may aid acceleration yet harm stopping; do not assign a universal V1 adjustment without approved data. Q1 and Q10. [5]
• Runway-limited mass: work the assigned chart for pressure altitude, OAT, mass, wind, surface, slope and flap; compare the computed required distance to its matching TORA/TODA/ASDA/LDA. For maximum mass, enter backward from available distance if the chart instructs. Different flaps trade shorter ground roll for climb drag; high/hot/obstacles may favour different settings. Q163, Q210–220 and Q508. [4]
• Engine-out take-off path: identify the screen height, gear retraction, first/second/final segments, all-engine versus one-engine-inoperative, gross versus net gradient, and any regulatory deductions on the chart. The second segment begins with gear retracted in the transport-category model. Avoid memorizing Q223–224's precise numbers without the applicable certification version. [5]
• Landing: approach speed, height at threshold, touchdown and braking all contribute; excess approach speed, tailwind, downhill slope, poor braking or inoperative anti-skid may raise required distance. Determine whether a chart gives ground roll, unfactored distance or factored landing requirement before applying any additional margin. Q213, Q275–281, Q305–309 and Q454. [4]

06 · Mass, moment and CG

For removed load, subtract its mass and moment before division. An index is a scaled moment; use the chart's divisor. Keep datum, station, arm and moment separate. Check CG inside the mass-dependent envelope. Forward CG raises stability/control effort and may hurt rotation; aft CG reduces stability. [2] [8]

Check MZFM, MTOM, MLM and max ramp mass. Floor loading = load ÷ contact area (kg/m²). Fuel mass = volume × density at the stated temperature. [1] [2]

Trap: Burnt fuel changes both mass and CG. Useful load/payload definitions can depend on the named chart; do not confuse traffic load with fuel.

Quiz theory: weight definitions and the limiting load

• BEM/BEW (basic empty) is not the same as DOM/DOW (dry operating), which includes the applicable crew and operating items but excludes traffic load and usable fuel. Traffic load is passenger, baggage and cargo according to the named manual. Thus traffic load = ZFM − DOM; usable take-off fuel = TOM − ZFM. Q342, Q348, Q373–379 and Q476. [2]
• Use landing mass = TOM − trip fuel. The payload limit is the least of MZFM − DOM, MTOM − DOM − take-off fuel, and MLM + trip fuel − DOM − take-off fuel, plus applicable performance, compartment and floor limits. Recheck whether fuel figures include taxi or unusable fuel. Q343, Q350, Q371–378 and Q572–577. [2]
• Moving load keeps total mass fixed; its CG shift equals moved mass × distance moved / total mass. Adding load increases total mass: shift = added mass × (load arm − original CG) / (original mass + added mass). Removing mass changes the denominator to original mass − removed mass. Q357–369, Q519, Q568, Q579–586. [8]
• Datum, station, arm and index: datum is an arbitrary published reference; a station gives location from it; arm is signed distance; moment is weight/mass × arm. A loading index is scaled moment as defined by the particular chart, never a universal unit. CG lies at total moment / total mass; recalculate after each load and fuel burn. Q11–13, Q311–326, Q472–474, Q491–497. [8]
• MAC: the leading edge of mean aerodynamic chord is LEMAC. CG station = LEMAC station + (%MAC/100 × MAC length). Formula works backward for %MAC. Beware negative arms and mixed in/cm/m units. Q380–388, Q483 and Q567. [8]
• Floor and running load: floor pressure = supported load / contact area (kg/m² or N/m²); running load = load / occupied longitudinal length (kg/m). For N from kg use W = mg with the g stated in the question. Check limits for each compartment, pallet and attachment as well as total mass. A smaller contact face means greater pressure. Q319, Q330, Q336, Q389–394 and Q578. [2]
• CG behaviour: forward CG generally needs more tail downforce/elevator, can raise stall speed and impair rotation; aft CG reduces stability and can hurt recovery. An aircraft can be under MTOM yet outside its CG envelope. Secure cargo against movement; a published maximum compartment load cannot simply be exceeded by 10%. Q11–12, Q339, Q472, Q506, Q550 and Q558. [8]

07 · Climb and descent

Use chart integration when ROC varies with height. Time, fuel and still-air distance to climb between two altitudes equal the upper chart cumulative values minus the lower values, when that chart uses cumulative values. Correct for wind to get ground distance. Descent follows the same time-distance logic. [3] [4]

Climb performance: excess power drives ROC; excess thrust drives climb gradient. VX maximises altitude per ground distance in still air; VY maximises altitude per time. An engine failure and high density altitude reduce climb margin. [7]

Trap: For obstacle clearance, use the question's required net/gross gradient and wind/ground-distance convention. An indicated climb angle is not a time-based ROC.

Quiz theory: performance forces, ceilings, glides

• For a small, steady climb angle, air-relative climb gradient ≈ 100 × (thrust − drag)/weight (%). ROC = excess power / weight, using consistent power units. Best angle maximizes altitude per air distance, best rate altitude per time. To convert chart air gradient to ground gradient, use ground distance and actual wind. Q111–112, Q147, Q174 and Q196. [7]
• VX (best angle) is for obstacle clearance over short horizontal distance; VY (best rate) is for time to altitude. Typically VX < VY, but trends with altitude, configuration, propulsion and IAS/TAS convention differ. Gear/flaps normally add drag and hurt climb; more mass and hot/high air reduce available climb. Q156, Q159, Q170–172 and Q190–209. [7]
• Service ceiling uses a stated low positive ROC; absolute ceiling is where maximum ROC reaches zero. For engine failure above the sustainable engine-out altitude, drift-down is a controlled descent toward an engine-out altitude while meeting route-clearance requirements. Q121 and Q185. [7] [12]
• For an unpowered glide at best L/D, more weight generally increases the airspeed and sink rate but not the still-air glide angle, if configuration and aerodynamic efficiency stay the same. Headwind shortens ground range; tailwind lengthens it. Q169, Q191, Q193 and Q205. [7]
• Obstacle check: available altitude at obstacle = screen height + distance from reference point × ground gradient (consistent units). Then subtract obstacle elevation relative to that same reference. Q398 and Q402. Do not treat 50 ft as zero. [4]

08 · Cruise, range and descent

For the same airspeed, tailwind increases ground range and headwind reduces it. Endurance is time aloft; range is distance. Select the exact chart's power, altitude, OAT, mass and engine configuration. Subtract climb/descent from cruise when the question calls for a whole trip. [3]

Trap: Do not mix US gallons, imperial gallons, litres and kilograms. Cruise chart fuel may already include a stated allowance.

Quiz theory: range, endurance, power and optimum altitude

• For a propeller aircraft under the simplified constant-efficiency/fuel-flow model, still-air maximum range is near maximum L/D; maximum endurance near minimum power required. A headwind shifts optimum ground-range cruise faster than still-air optimum; a tailwind generally shifts it slower. Wind does not by itself change the airspeed for maximum airborne endurance. Q173, Q183–184, Q193, Q197 and Q203. [7]
• Induced drag dominates low speed, parasite drag rises at high speed. Behind the power curve (reverse command), slowing down demands more power to maintain level flight. At high weight, best L/D speed rises roughly with √weight if other assumptions stay fixed. Q114, Q161, Q167–169, Q175 and Q208. [11]
• Critical altitude of a boosted piston engine is the highest standard-condition altitude at which the stated manifold pressure/power can still be maintained. Flat-rated jet thrust is capped below a specified temperature and falls above the rating break; actual engine charts decide. Q162 and Q411. [7]
• Optimum altitude depends on mass, temperature, wind, climb cost and chart constraints, not altitude alone. Review altitude restrictions and buffet/stall margins for high-altitude cruise. Q202 and Q502. [3]

09 · Fuel planning

Separate required reserves from extra fuel. Use the regulation and type of flight named in the question. The syllabus names taxi, trip, contingency, alternate, final reserve, additional and extra fuel. It does not supply one universal reserve figure. [1]

Trap: Do not spend final reserve in a PNR calculation. Check whether an assigned CAP 697 chart already includes taxi, run-up or reserve fuel.

Quiz theory: usable fuel versus mass

• Block is fuel before taxi; take-off fuel is block less taxi; landing fuel is take-off fuel less trip. Reserve is part of landing fuel unless flight-plan definitions say otherwise. Unusable fuel cannot be treated as available endurance; check whether BEM already includes it. Q76, Q82, Q240–241, Q321 and Q464. [2] [3]
• For volume-to-mass problems, specify whether gallons are US or imperial. 1 US gallon ≈ 3.785 L; 1 imperial gallon ≈ 4.546 L. Density kg/L × volume L = kg. Quiz examples mix lb/USG, kg/L and gallons. Q359, Q396–397, Q410 and Q566. [2]
• A chart can contain a default taxi/run-up, climb allowance or reserve. Read its notes and avoid charging those again. Invert the mass equations to find maximum traffic load only after subtracting required fuel and checking both take-off and landing limits. Q253–266 and Q342–354. [3]

10 · Wind triangle

Wind direction states where wind comes from. Let θ be the angle between track and wind-from direction. Use signed crosswind for left/right. All speeds use kt. [9]

The last expression assumes a feasible crab angle. If crosswind exceeds TAS, that track cannot be held. Convert magnetic/true references before comparing wind and course. [9]

Trap: GS ≈ TAS − headwind ignores the small loss due to crabbing. Use the CX-3/E6B or full triangle when precision matters.

Quiz theory: headings, runway and timing

• Wind is reported from a direction, track is where the aircraft travels. Headwind/tailwind and crosswind components come from the difference between wind-from and runway/track direction after both are put in the same true/magnetic reference. For an exact wind triangle solve heading correction first, then GS. [9]
• On a climb or descent chart showing air nautical miles (NAM), convert to ground nautical miles with segment time: GNM = NAM + (tailwind kt × time h), or subtract headwind × time. If using GS = TAS ± along-track wind as an approximation, check crosswind effects. Q228–234 and Q421–424. [3]
• A headwind cuts ground distance during a given climb and increases ground distance when reversing course on the return leg; it does not change the altitude gained for a given aircraft climb time. Tailwinds can increase glide ground distance, but not the still-air glide ratio. Q195 and Q205. [7]

11 · PET / CP and PNR / PSR

PET or CP is the location where time to continue to the selected destination equals time to return to the selected departure/alternate. PNR or PSR is the furthest point permitting a return with the permitted fuel. Set separate outbound and return groundspeeds. [1]

Hours × knots gives nautical miles. For unequal outbound and return fuel flows, solve fuel directly: outbound burn rate × (x/GSout) + return burn rate × (x/GSreturn) = fuel available after reserves. [10]

Trap: PET depends on distance and speeds, not endurance. PNR depends on available endurance/fuel; it may fall before or after PET.

Quiz theory: compare equal times versus remaining fuel

• PET changes if an out/return groundspeed changes, even with the same total distance. PNR depends on safe endurance after protected reserve. In both formulas, outbound and return GS are named for their direction; a headwind outward is normally a tailwind on the exact reverse track, provided wind is constant. Q71–75, Q480 and Q523–533. [10]
• Clock time at PET = start clock time + PET outbound distance / GSout, converting decimal hours to minutes. The user's FP.pdf includes clock-time questions Q524, Q529 and Q531. Use 24-hour arithmetic and account for midnight. [10]
• Checkpoint from a waypoint: compute PET/PNR from the route's named origin, then subtract distance already traveled from that origin when asked distance from WP3. This is a distance-origin issue, not a new PET equation. Q71. [10]
• In a direct outbound-and-return PNR problem with equal fuel flow, total safe endurance E = x/GSout + x/GSreturn. Solving gives the displayed PNR formula. With unequal outbound and return burn, use the fuel equation rather than average a fuel flow; leave required reserve protected. [10]