PERF APPR: REFERENCES, MINIMA AND APPROACH SPEED
Enter current pressure, temperature and wind on PERF APPR and check landing configuration and approach-speed information. TRANS ALT is the transition-altitude field; the descent transition level comes from the relevant arrival information. On descent through that level, set the current QNH on both sides and crosscheck the references. [66, PDF pp. 199-209] [21, PDF pp. 149-158] [66, PDF pp. 205-207] [23, PDF pp. 1087,1089]
Set the charted minima with the correct barometric or radio reference for the approach. Identify the point at which the required visual reference governs continuation and brief the missed-approach response. Resolve the setting and its meaning during preparation rather than first assessing an unfamiliar value near the decision point. [21, PDF pp. 149-158]
Crosscheck VAPP against the current configuration and calculation. A runway, wind or aircraft-condition change requires review of the affected entries and landing performance. The consistency check extends from the result on the tablet to the entered data, selected guidance and aircraft actually approaching Heathrow. [21, PDF pp. 149-158]
IN PRACTICE: Give PERF APPR useful information
Before you begin: The correct Heathrow runway and approach are in the flight plan, and current weather/landing-performance information is available.
1. Enter the pressure and temperature
Action. Open PERF APPR and enter the current destination QNH and temperature. Read each accepted value back and compare with the arrival information.
Check. The approach prediction uses the current pressure and temperature for the selected destination. [66, PDF pp. 205-207] [23, PDF pp. 1082-1084]
2. Use the wind reference the runway uses
Action. Enter the landing wind from the current tower/ATIS information, checking its reference. If starting from a METAR/TAF true-referenced wind, convert it to the runway reference before entry.
Check. The headwind component behind the approach-speed computation is not distorted by an unnoticed true/magnetic mismatch. [21, PDF pp. 149-158] [66, PDF pp. 205-207]
3. Keep TRANS ALT and transition level separate
Action. Check the PERF APPR TRANS ALT field against the destination transition altitude. Obtain the descent transition level from the applicable arrival information; it is not a separate TRANS ALT entry.
Check. The MCDU field and the later altimeter change each have their correct role. [66, PDF pp. 205-207] [23, PDF pp. 1087,1089]
4. Set the charted minima in the correct field
Action. Enter the charted minimum using its barometric-altitude or radio-height reference, as appropriate to the selected approach. Read the value and the reference back together.
Check. The approach minimum corresponds to the actual charted decision reference. A height has not been entered as though it were a pressure altitude. [66, PDF pp. 205-207] [21, PDF pp. 159-162]
5. Make configuration and VAPP agree
Action. Select the planned landing configuration, compare the resulting VAPP with the performance/briefing, and check the mass and wind information behind it. Revisit the result after a material runway, loading or weather change.
Check. The displayed approach speed belongs to the intended landing configuration and current aircraft/weather case. [21, PDF pp. 149-158] [66, PDF pp. 205-207]
6. Apply the local pressure reference at the right point
Action. When descending through the applicable transition level under an altitude clearance, set the current QNH on both sides and crosscheck the altimeters.
Check. The aircraft continues the arrival using the correct local altitude reference. Entering QNH on PERF APPR has not been mistaken for setting the altimeters. [23, PDF pp. 1087,1089]
Complete when: PERF APPR is complete, the minimum and wind references are understood, and both altimeters will be changed at the applicable transition point.