SAMRA/SARON Flight Operations Questions

The ICAO Standard Atmosphere defines sea-level conditions of

• 0°C and 29.92 in. Hg exactly, with a constant lapse rate assumed all the way up to 60,000 ft.
• 15°C and 30.00 in. Hg exactly, with no defined lapse rate specified at all.
• 15°C and 29.92 in. Hg (1013.25 hPa), with a lapse rate of about 2°C per 1,000 ft to the tropopause.
• 59°F and 1000 hPa exactly, with a lapse rate of 1°C per 1,000 ft assumed constant throughout the entire atmosphere.

Explanation: The ICAO Standard Atmosphere is the reference model used to calibrate altimeters and performance data: 15°C and 29.92 in. Hg (1013.25 hPa) at sea level, temperature decreasing at roughly 1.98°C per 1,000 ft up to the tropopause (about 36,090 ft), above which it is modelled as constant.

TP 690 Section 5 - Atmospheric Effects in Flight, ICAO Standard Atmosphere

Holdover time (HOT), as published in de-icing guideline tables, represents

• a single fixed time limit that stays identical regardless of precipitation type or intensity.
• an estimated range of time during which anti-icing fluid is expected to prevent ice, frost, or snow from adhering to treated surfaces, under specified weather.
• the maximum time an aircraft may legally remain on the ground awaiting departure clearance, regardless of the prevailing weather conditions at the time.
• the total time required for the anti-icing fluid itself to fully dry after being applied.

Explanation: HOT tables give a range (not a single fixed number) that depends on the fluid type/concentration and the specific weather condition (precipitation type and intensity, and outside air temperature) -- it estimates how long the anti-icing protection can be relied on before contamination may begin adhering again, which is why a pre-take-off contamination check is still required if HOT is approached or exceeded.

TP 690 Section 5 - Critical Surface Contamination, Variables that Can Influence Holdover Time

A reduced (flex, or assumed temperature) thrust takeoff is a technique in which the crew

• reduces thrust only after V1 has been reached, applying full thrust throughout the portion of the takeoff roll before V1.
• sets takeoff thrust below the engine's full-rated value, when performance margins allow, to reduce engine wear while still meeting all required takeoff performance margins for the actual conditions.
• is prohibited from using any takeoff thrust setting other than the engine's absolute full-rated maximum, regardless of runway length or obstacle margins. This consideration is particularly relevant during abnormal or non-standard operations.
• increases takeoff thrust above the engine's full-rated value whenever performance margins are unusually generous, to shorten the takeoff roll further.

Explanation: Where the runway, weight, and obstacle environment provide more performance margin than is strictly required, a reduced thrust setting (calculated using an assumed temperature higher than actual, or a flex-thrust computation) can still meet all required takeoff performance margins while reducing engine wear and extending time-on-wing -- it isn't used, or available, when actual conditions leave no such margin to spare.

TP 690 Section 5 - Flight Operations, Takeoff Performance

In addition to the landing distance calculation performed at dispatch, some operators require a separate in-flight landing distance assessment shortly before arrival. This reassessment is intended to

• verify that landing distance required, using the actual conditions expected at arrival -- weight, wind, runway condition, and configuration -- still fits within landing distance available.
• assess only fuel remaining at landing, with runway condition, wind, and configuration excluded from the in-flight assessment.
• replace the dispatch landing distance calculation entirely, making the original dispatch figure irrelevant once the in-flight assessment is completed.
• apply only to VFR flights, with IFR flights considered exempt from any in-flight landing distance reassessment requirement, despite IFR operations typically being exactly where such a policy is applied most consistently.

Explanation: Conditions at the actual time of arrival -- updated weight, current wind, reported or forecast runway surface condition, and the actual approach/landing configuration planned -- can differ from what was assumed hours earlier at dispatch, so an in-flight landing distance assessment re-checks that the landing is still within landing distance available under those more current, specific conditions, complementing rather than replacing the original dispatch calculation.

TP 690 Section 5 - Flight Operations, Landing Performance

Tail strike risk during the takeoff rotation is primarily increased by

• over-rotation -- raising the nose too quickly or to too high a pitch attitude relative to the aircraft's geometry-limited pitch attitude for the given speed and configuration.
• excessive airspeed at the moment of liftoff, since higher speed is associated with reduced pitch attitude rather than an increased tail strike risk.
• landing gear extension during the takeoff roll, a configuration change that is never performed and has no bearing on tail strike risk during rotation.
• rotating too slowly, since a tail strike is understood to result exclusively from an insufficient rotation rate rather than an excessive one, a claim not supported by how tail strikes are actually documented in service events.

Explanation: Tail strike risk during rotation is primarily increased by over-rotation -- raising the nose too quickly or to too high a pitch attitude relative to the aircraft's geometry-limited attitude for the current speed and configuration -- rather than by rotating too slowly, by a gear extension that does not occur during the takeoff roll, or by higher liftoff airspeed, which is generally associated with a lower, not higher, tail strike risk.

TC AIM RAC - Takeoff Rotation Technique

Differential braking, applying more braking force to one main gear than the other, is a technique used primarily to

• replace the need for nose wheel steering entirely on every aircraft type, making nose wheel steering an unnecessary system wherever differential braking is available.
• increase the aircraft's overall stopping distance, since differential braking is understood to reduce, rather than assist, the aircraft's ability to decelerate.
• control the aircraft's pitch attitude during the landing flare, a function unrelated to directional (yaw) control on the ground, and one that differential braking, applied at the main gear, does not itself perform.
• assist directional control on the ground, such as during a crosswind landing rollout or when other directional control means (like nose wheel steering or rudder) are insufficient.

Explanation: Differential braking -- applying more braking force to one main gear than the other -- is used primarily to assist directional control on the ground, such as during a crosswind landing rollout or when other directional control means like nose wheel steering or rudder are insufficient -- it is a directional (yaw) control technique, not primarily intended to increase stopping distance, and it complements rather than universally replaces nose wheel steering.

TC AIM RAC - Differential Braking

A reduced flap takeoff technique, as distinguished from a reduced (flex/assumed-temperature) thrust takeoff, generally involves

• reducing engine thrust below the certified takeoff thrust setting, a description that actually applies to a reduced/flex thrust takeoff rather than a reduced flap takeoff.
• increasing flap deflection beyond the normal takeoff setting in every case, the opposite of what a reduced flap setting actually means.
• eliminating the use of flaps entirely on every takeoff, regardless of aircraft type, runway length, or obstacle environment, since a reduced flap takeoff is defined as using no flap deflection at all rather than a smaller deflection than the normal takeoff setting, and is therefore expected to always shorten rather than lengthen the resulting takeoff roll.
• selecting a smaller flap deflection than the normally used takeoff setting (where performance permits), which can improve climb gradient (useful where obstacles are a limiting factor) or reduce airframe noise, at the cost of requiring a longer takeoff roll than the standard flap setting would.

Explanation: A reduced flap takeoff selects a smaller flap deflection than the normally used takeoff setting, where performance data permits it, generally trading a longer required takeoff roll for an improved climb gradient (useful when obstacle clearance rather than runway length is the limiting factor) or reduced airframe noise -- a distinct technique and trade-off from a reduced/flex thrust takeoff, which instead reduces engine thrust while using the normal flap setting.

TP 690 -- Flight Operations: Takeoff Performance

When conducting an approach and landing with one engine inoperative, operators commonly favour using less than full landing flap primarily because

• full flap is prohibited by regulation on any approach conducted with one engine inoperative, regardless of aircraft type or performance margin.
• a reduced flap setting always produces a shorter landing distance than full flap, regardless of the reduced go-around performance consideration.
• a reduced flap setting requires less thrust from the operating engine(s) to maintain the approach path, preserving a greater go-around climb performance margin should a go-around become necessary, at the cost of a somewhat higher approach and landing speed.
• flap setting has no bearing on go-around climb performance with one engine inoperative, making the choice purely a matter of pilot preference.

Explanation: With one engine inoperative, less than full flap is often selected for the approach because a reduced flap setting requires less thrust from the remaining operating engine(s) to sustain the approach path, preserving more of the aircraft's already-reduced excess thrust as a margin for climb performance should a go-around become necessary -- this comes at the cost of a somewhat higher approach and landing speed and, correspondingly, a longer landing distance required, a trade-off operators and crews weigh against the specific runway available.

TP 690 -- Flight Operations: One-Engine-Inoperative Approach