Originally Posted by
PEI_3721
There should not be any structural problem up to the limiting sideslip angle (possibly defined by physical rudder limit / airspeed schedule). As with other structural limits there is a margin of safety, ....
I wouldn't be prepared to bet on that, especially if the manoeuvre is being enacted in response to a sudden depressurization and/or a need to initiate a quick emergency descent. Something already went badly wrong with your aircraft; are you that confident that the same event - whatever it was - didn't disrupt the nice tidy conditions assumed for the structural design calcs? Never mind that there is always the issue that for certification there is always the option - certainly for considering handling limits - to define various aircraft responses as "deterrent" - and high lateral accel may be one of those. So the OEM and authority may have satisfied themslves that "no one in their right mind" will do exactly what is now being attempted.
Even Va I'd take with a pinch of salt - yes, there are margins in the structural calcs in terms of UL/LL factors - but those are also there to account for things like an imperfectly flown manoeuvre compared to the 'perfect' design case, or errors in the calcs, or repairs to the structure, or fatigue weakening the structure, or .... Just because there's a margin in a cert requirement, certainly does not mean it's all going to be there to rely on for any given event.
You'd have to have a bloody good reason to be aggressively sideslipping a swept wing transport.
Originally Posted by
Pugilistic Animus
The most important concern regarding sideslip is fuel tank unporting and engine upsets[at extreme sideslip autoignition may help,...but the air entering,... may be so low energy that it wont matter,...of course as you said it depends on the spsecific AFM limits,...
as far as aerodynamic issues these are most related to instrument indications [if uncorrected] etc...not strength
but attaining the practical slip limit on a jet to me seems...
I'd agree with that last sentence, but not the bit in bold. Sideslip is turned into an effective increase in angle of attack on the leeward wing, in terms of margin to the stall. Sideslipping a swept wing aircraft to its limits is not something you should be doing lightly. There could be some extremely nasty aerodynamic characteristics waiting to bite you.
And with respect to control reversal - you don't even need
repeat oscillations. The Part 25 manoevres don't even apply a single full throw reversal. If you stamp on a pedal, wait until full sideslip, then stamp to come back - as opposed to just centering the pedals, which is the cert manoeuvre - well, the fin and rudder
might stay attached. But no-one's promising you that.