Plan the departure and the arrival

How does a gradient become a required rate?

Gradient relates height to horizontal distance; rate also depends on groundspeed.

Convert geometry into time

A climb gradient ofg percent means g units of height per 100 horizontal units. One NM is 6,076.12 ft, so the required climb gradient inft/NM is g/100 ×6,076.12. Multiply by GS/60 to obtainft/min. A stronger tailwind raises the rate needed for the same ground-referenced gradient.

A published departure gradient and an aircraft climb capability must use compatible definitions. Gross, net, all-engines and engine-out data are not interchangeable. Use the aircraft and operational performance method appropriate to the procedure and contingency.

Respect chart constraints

Read SID routing, altitude and speed restrictions, navigation requirements and any climb-gradient notes together. A restriction that says at or above differs from at or below; a window requires both. A route loaded from the database still needs comparison with the current chart and clearance.

For arrival, a descent-path estimate helps identify when to begin descent, but it does not authorise descent below a clearance or published restriction. Track miles, wind and speed changes can make an initially comfortable profile unachievable later.

Test the limiting segment

If a route needs 5% gradient at 150 kt GS, required rate is about 760 ft/min. Checking a rate at 100 kt instead would understate the demand. Conversely, an aircraft can have a positive climb rate while failing a required gradient. Ask how far it travels horizontally for every foot gained.

The laboratory isolates gradient and GS so the relationship is visible. It omits acceleration, configuration changes and obstacle-accounting details. Use it to understand a published requirement, then use approved performance data for an operational decision, including the relevant engine-failure and other applicable contingencies.

The same gradient can be flown at different rates because the available time per ground mile changes with groundspeed.

Why does alternate fuel start with a missed approach?

A diversion plan must connect the destination decision to a safe alternate landing.

Read the complete approach chart

Identify the procedure, navigation requirement, initial and intermediate segments, final approach, minima, missed-approach routing and relevant notes. A runway with an approach is not automatically usable: serviceability, aircraft capability, crew qualification, weather and runway conditions all affect suitability.

Approach minima and planning minima serve different purposes. Planning can require margins above the operating minimum to reduce the probability that an alternate will be unusable when needed. Do not apply a classroom margin universally; use the applicable current operational scheme and chart data.

Build a connected diversion profile

A destination-alternate fuel calculation generally needs to represent the missed approach, climb, cruise or other en-route segment, descent, approach and landing according to the applicable planning method. Starting the calculation at the destination threshold and assuming the aircraft instantly appears at cruise level omits real fuel-consuming phases.

Include expected routing and restrictions at the alternate. A nearby aerodrome may require a long instrument path or have an unfavourable wind. The best alternate is the suitable option under the governing requirements, rather than simply the nearest runway symbol.

Keep an unavailable approach out of the plan

If a NOTAM removes the only usable approach or a navigation outage invalidates it, reassess suitability and fuel before departure or as conditions change. The presence of the procedure in an FMS database does not override its current operational status.

In the exercise, missed approach and climb consume 300 kg, en-route diversion 400 kg and arrival 150 kg. Alternate fuel is 850 kg for that stated profile. This is a synthetic sum, not a generic aircraft allowance. Final reserve is protected separately under the stated fuel plan; do not silently include or omit it twice.

Can you explain and apply the mechanism?

Four original questions. Work from the stated facts, then compare your reasoning with the explanation.