PPRuNe Forums - View Single Post - Limiting Factors For Takeoff
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Old 28th May 2010, 05:19
  #72 (permalink)  
john_tullamarine
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V2 min is based on 1.1VMCA or 1.23 VS whichever is higher right?

Variation exists depending on the particular Standard but the general rule applies that the minimum takeoff speed (either V2 or VTOSS) is the greater of a Vmca and Vs factor.


JT when you mentioned that one could find out whether VMCA/G limited by checking the 'the speed no longer varies with weight (Vs limiting)'.
Are you talking about the Perf tables where you get the ASSUM temp?or the tables in the FCOM where you get the speeds for the actual weight(balanced field)?

You're looking for a table which gives V1/VR/V2 against RTOW. At the lower weights, for most aircraft, Vmca or Vmcg will become limiting rather than Vs. You see this change when the speed no longer gets lower with reducing weight.

I am getting lost, could you please use a more basic english?

Any time we talk too much jargon and you don't understand, the fault is with us, not you. Just ask and we will try again and rephrase the discussion.

it's not simply deterministic, and can be quite a convoluted story in reality

MFS' meaning here is that it is not just a matter of looking up a table to get the answer. For the RTOW calculation one has to run a series of calculations to check a range of limitations with the most limiting (ie lowest RTOW answer) becoming the final RTOW for the conditions. That process, depending on the aircraft, the runway, and how much effort one wants to put into optimising the result (getting the highest RTOW) can get quite involved and complicated (convoluted)
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