Re: Pulling a Stop to Runway Overruns
Since this point appears to be being overlooked, I'll make it again.
Typical nosegear reactions statically are of the order of 5-10% of aircraft weight; the other 90-95% being borne by mainwheels.
To achieve even a 10% improvement in braking decel - assuming that there is NO aerodynamic download, which is an optimistic assumption for this method - requires a tail download of approx 5% weight and a corresponding nosewheel unload of similar magnitude. That is perilously close to completely balancing the static force on the nosegear, which would mean totally uncompressing the nose oleo, and loss of all NWS effectiveness plus increasing AoA and so reducing downforce on the mains.
For those who doubt that this can happen: one of our test aircraft was offsite conducting Xwind tests in very windy conditions - 30kts plus with gusts to 40kts. While the aircraft was parked into wind, the crew noticed that the effect of nose-up stab trim was such that they almost unloaded the oleos on the nose. AT FORTY KNOTS. At eighty knots - the kind of speeds this technique is being advocated for - the effect would be 4 times as powerful. I'm as certain as I can be that you WILL lift the nose under those conditions.
The idea that significant amounts of nose-up elevator or stab don't risk raising the nose is not well founded. After all, that's how you achieve rotation, no?
I don't believe my OEM is "scared of a new technique". We are scared of someone trying this out with pax in the back and either departing the side of the runway due to loss of NWS/directional control, or raising the nose and actually losing braking effectiveness. I've seen our aircraft at low speeds (typical of landing rollouts) with the nose in the air and have no desirte to see that repeated by line pilots.