B737 Classic Runway Analysis max weights versus QRH speeds for light weights.
We know that individual runway analysis charts list performance limit weights for a variety of flap settings, bleed configurations, airport temperatures and headwind and tailwind components. Worst case is probably based on 50 degrees C and say 10 knots tailwind (depending on chart design).
Occasionally the weight of the aircraft may be light and significantly less than the any of the weights listed on the analysis. Typically a ferry flight or some other event where the weight is well below average.
For the B737 Classics this is covered (or does this depend on personal interpretation?) by a QRH preamble at Chapter P1 Section 16 page P1.16.1 under the sub-heading Takeoff Speeds, that states: " The speeds presented in the Takeoff table, as well as FMC computed takeoff speeds, can be used for all performance conditions provided adjustments are made to V1 for clearway, stopway, brake deactivation, improved climb, contaminated runway situations, brake energy limits with unbalanced V1.
These speeds may be used for weights less than or equal to the performance limited weights.
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My example: Lowest weight to be located on a runway analysis chart is (say) 52,000 kgs which is found at the 10 knot tailwind 50C temperature position on the runway analysis chart for flap 5. However, let us assume the actual aircraft weight is 42 tonnes or 10 tonnes less than the worst case performance limiting weight described above of 52 tonnes.
Am I correct in saying that in this case I can use the QRH speeds for the actual weight of 42 tonnes - based on the advice provided in the QRH? After all, V speeds are based on actual weight - not a fictitious weight for convenience.
If not, why not?