Originally Posted by OVERTALK
But many newer design rear-engined smaller jets such as the CRJ seem to have similarly mounted engines....so perhaps someone can comment on whether the CRJ has a similar caution written into the Pilots' Notes.
Actually, I can, because your assumption that the manufacturer I work for is based south of the "49th Parallel" is misplaced. So while I don't know what McDD (why does it censor the 6 letter version?) may have recommended in the past for their product line, Bombardier (in the form of Canadair, specifically) does have such a recommendation.
At present the FAA is very very circumspect in defining techniques and configurations for establishing "book" distances - so I'd see that view as being unnecessarily alarmist.
If we were allowed to take credit for all available braking devices, rather than having to leave one 'in reserve' as it were, I can assure you that simple commercial pressure would REQUIRE us to do so, or lose performance and hence sales to our competitors. So if there were a reliable technique for increasing braking performance that we could take credit for, there would be very power motivation to use it.
I'm not sure that ALPA or IFALPA would agree with your continued portrayal of professional pilots as having to conform to your depiction of their abilities, skills and challenges necessarily being limited (and conforming) to a lowest common denominator.
I recall being at a light aircraft design conference in the UK where one of the keynote speakers - who was I believe from the 'pilot side of the fence' was urging us, as designers, to design aircraft that even an idiot couldn't kill themselves in. I'm not the only person thinking in terms of lowest common denominators.
Not sure that this is a productive piece of imagery. It's one reason why my first inclination was to first use the analogy of the second-class lever (with the nose as fulcrum). Using that logic the backstick just lowers the tail and loads up the main-gear, with the nose-gear acting as a pivot-point.
No, no, a million times NO. The nose gear is NOT rpt NOT a fixed pivot. It will extend or compress the nose oleo in response to load, as indeed will the mains. Any increased download on the tail MUST both increase mainwheel download (compressing the main oleos more) and decrease nosewheel load (necessarily extending the nose oleo). EITHER of these two effects will cause the pitch attitude to increase; both together certainly will.
The question remains whether the amount that the nose rises is either
(a) a risk of actually raising the wheel out of ground contact - something to be avoided at almost any cost, and a DEFINITE risk on our types. Any aircraft where that is a concern shouldn't be using this advocated technique.
(b) a small increase in pitch attitude and hence AoA and a MILD unloading of the nose. The former will act to increase wing lift and counter the downloading you're seeking to add; the latter may have directional control implications.
On those types not subject to the "pitch up" risk the technique MAY help; and it may not. It's by no means certain to. But until demonstrated by the OEMs and endorsed by appropriate handling advice, you are essentially assuming that you know better than our test pilots did when they developed the advice we provide. I'd really rather people didn't try that, certainly in our product line.
Oh, and ...
John Farley has endorsed the ability of backstick to "load up" the main-gear for more effective braking on mush - so perhaps we can leave this nicety to be thrashed out by the aerodynamicists (who will see it as the resultant of couples (nosedown pitching moment and taildown pitching moment).
That
aerodynamicist would, in fact, be me, I'm afraid. At least for my company (in company with my colleagues, of course; no one works alone these days). So I'm quite familiar with the nature of on-ground modelling for aerodynamic behaviour; I think I've been doing it, off and on, for about 16 years now.