The questions stands.
DRT with regards to Vmcg/a is no more protected than AST. Contrary, with DRT for many installations a pilot by his own mishandling can find himself outside the certified territory, a case for calling the AST more protected.
But that is available knowledge. As well as the fact that DRT with lower rating and Vmcg/a could yield a higher PTOM compared for AST with the same EPR/N1.
On a wet runway, both are allowed to depart. The DRT configuration might provide for better TOW.
On a contaminated (frost covered): The surface deposit is the same, the drag effect and calculated friction is the same. Even the delivered thrust might be the same. In that case the AST could be less enabling (higher V1 and less stopping distance remaining) and firewalling the levers poses no risk as opposed to DRT. Yet, it is the AST which becomes illegal.
I could see a commercial / statistical risk / exposure balance in there, similar to wet screen height and TOR calculations. Okay.
But is there a technical element that is more risky with AST compared to DRT? Carrying less weight and being protected to full rated thrust is less risky, right?
Sure, a lower Vmcg/a gets you airborne while reducing TOM would not move that goalpost. Possibly unable to depart due to MNM V1 and lack of braking real estate thereafter - an inherent limitation of AST.
But in a case where the numbers do add up, what's better with DRT to warrant the additional legality? Wrong vector on the question, actually. What's more sinister about AST for it to be unacceptable?
Last edited by FlightDetent; 28th Nov 2022 at 21:42.