Rolling 'G'

[fdr]

Originally Posted by PEI_3721

zzuf, yes missing, misinterpreting - most probable.

The quest was for a practical answer - if rolling 'g' is not limited by the AFM, then do crew have to be concerned by a combined pull / roll during an upset recovery.

My conclusion is no, and that in some circumstances the control input is difficult.
Furthermore, with the surprise in such situations then the likelihood of the crew recalling an obscure limit, if it exists, is remote.

§ 25.303 Factor of safety.

Unless otherwise specified, a factor of safety of 1.5 must be applied to the prescribed limit load which are considered external loads on the structure. When a loading condition is prescribed in terms of ultimate loads, a factor of safety need not be applied unless otherwise specified.

§ 25.349 Rolling conditions.

The airplane must be designed for loads resulting from the rolling conditions specified in paragraphs (a) and (b) of this section. Unbalanced aerodynamic moments about the center of gravity must be reacted in a rational or conservative manner, considering the principal masses furnishing the reacting inertia forces.

(a) Maneuvering. The following conditions, speeds, and aileron deflections (except as the deflections may be limited by pilot effort) must be considered in combination with an airplane load factor of zero and of two-thirds of the positive maneuvering factor used in design. In determining the required aileron deflections, the torsional flexibility of the wing must be considered in accordance with § 25.301(b):

(1) Conditions corresponding to steady rolling velocities must be investigated. In addition, conditions corresponding to maximum angular acceleration must be investigated for airplanes with engines or other weight concentrations outboard of the fuselage. For the angular acceleration conditions, zero rolling velocity may be assumed in the absence of a rational time history investigation of the maneuver.

(2) At VA, a sudden deflection of the aileron to the stop is assumed.

(3) At VC, the aileron deflection must be that required to produce a rate of roll not less than that obtained in paragraph (a)(2) of this section.

(4) At VD, the aileron deflection must be that required to produce a rate of roll not less than one-third of that in paragraph (a)(2) of this section.

(b) Unsymmetrical gusts. The airplane is assumed to be subjected to unsymmetrical vertical gusts in level flight. The resulting limit loads must be determined from either the wing maximum airload derived directly from § 25.341(a), or the wing maximum airload derived indirectly from the vertical load factor calculated from § 25.341(a). It must be assumed that 100 percent of the wing air load acts on one side of the airplane and 80 percent of the wing air load acts on the other side.

'

V-speeds defined in 14 CFR part 1

VA design maneuvering speed

VB design speed for maximum gust intensity

VC design cruising speed

VD design diving speed

VDF/MDF demonstrated flight diving speed

VEF speed at which the critical engine is assumed to fail during takeoff

VF design flap speed

VFC/MFC maximum speed for stability characteristics

VFE maximum flap extended speed

VFTO final takeoff speed

VH maximum speed in level flight with maximum continuous power

VLE maximum landing gear extended speed

VLO maximum landing gear operating speed

VLOF lift-off speed

VMC minimum control airspeed with the critical engine inoperative

VMO/MMO maximum operating limit speed

VMU minimum unstick speed

VNE never-exceed speed

VNO maximum structural cruising speed

VR rotation speed

VREF reference landing speed

VS stalling speed or minimum steady flight speed at which the airplane is controllable

VS0 stalling speed or minimum steady flight speed in the landing configuration

VS1 stalling speed or minimum steady flight speed obtained in a specific configuration

VSR reference stall speed

VSR0 reference stall speed in the landing configuration

VSR1 reference stall speed in a specific configuration

VSW speed at which onset of natural or artificial stall warning occurs

VTOSS takeoff safety speed for Category A aircraft

VX speed for best angle of climb

VY speed for best rate of climb

maximum speed in the takeoff at which the pilot must take the first action (e.g., apply brakes, reduce thrust, deploy speed brakes)
to stop the airplane within the accelerate-stop distance. V1 also

V1 minimum speed in the takeoff, following a failure of the critical engine at VEF, at which the pilot can continue the takeoff and achieve the required height above the takeoff surface within the takeoff distance.

V2 takeoff safety speed

V2min minimum takeoff safety speed

The highest load case does not occur in the rolling g manoeuvre, the greatest loads occur if a limit control input is reversed with a suitable lag to the aircraft response, particularly in the rudder control, and to a lesser extent for ailerons, and elevator. A rapid reversal of ailerons will achieve a high torsion and associated bending load, and that is not covered as a criteria in certification. The rudder is the most problematic control inn that regard, as shown by AA587, For Airbus electrojets the controls are relatively good at achieving a linear response which is nice. For older Boinkies, the speed brake has a marked effect on roll response, and you can move from good to badness by putting in the control and then pulling the brake. The Max added FBW for parts of the spoilers, which is good. The Airbus authority is derived from a lookup table of commanded rate and a deflection command, this being subject to the position of the T.E. flap. If that gets out of sorts, the plane is most entertaining, refer HDA323 and the USAir GA at NY with a jammed T.E. flap.

One event on a XXXX brand had the rocket scientists achieving a 150KCAS overspeed and at about that time, the aircraft data showed a clear case of aileron reversal, but not for long... shortly thereafter the wings fell off and it all ended in tears. Sad.

When you invert a Part 25 aircraft, it is imperative to get the aircraft blue side up, its far prettier that way, as long as you are inverted, alpha stability will be driving your pointy end ever more downward, at around 10 degrees a second, give or take. Your plane just don't got the elevator authority to do the upside down canopy to canopy bird pinkies that Maverick and Goose did, your stab trim is agin ya, and the elevator AND authority is just not going to get good marks on an Aresti score card. The dart is trimmed normally around 1g, which will be around 2.3-2.5 AOA on most planes, and that means upside down, unfettered by human intervention you are going to be pitching to about 2g hence the world getting big in the window promptly. Roll rate other than the bus, is going to be a function of AOA, and at least the plain is helping in that case, the AOA it is trying to achieve is what you had shiny side up, so unless you are pulling ailerons will be effective. Applying rudder is "heroic" and unless that is all that is left, not all that helpful. Once you are over on your back, you will see a lot of the planet, and the recovery will be raucous. The overspeed isn't what hurts, it's the g. Your roll rate you can see in your sim, it is not bad but it isn't a Pitts, Acro, A4 or MIR3, and it aint no T38/F5. Rolling upright takes a finite time and your nose will be dropping until the lift vector is skyward. For your UPRT cases, the sims aren't bad, well, most nowadays aren't, but they are also not perfect in the way outside the envelope case. Low speed is pretty good, and if approved under ICAOs UPRT simulator QTG requirements they are pretty good, but only to a point. A B767 or 737 etc is a dart, and given enough direction it will behave like all darts. The FAFO point on that is using the wrong controls for yaw and roll, and getting slow. These planes are really really good, but we seem to get them out of sorts if we try hard enough. In overspeed, once you are past MMO +0.06 or thereabouts, congratulations, you are a test pilot, and if you survive, feel free to share your data with the OEMs. (there are various aircraft that data hads been gained beyond those speeds, but mostly they came from the FDR, or by really good AAI followup, such as the Air Chine B747SP 6-flags ride on the way to SFO way back when. Getting thrust off ASAP is critical, more or less no matter what the cause, as you are going to get steep, really fast, do the math.

Fly safe, and treat your planes with kindness, as others have flown it before you... and hopefully others will afterwards.

IMHO, E&OE... boring is good.

[Three Wire]

Thanks JT, knowledge made simple for a simple pilot. I managed over 12000 hours total on all the B777 models to date before I retired. Never saw that video but had heard about it. The wing seemed to break about the position of the engine pylon.

[markkal]

I stand corrected despite my findings in flight, indeed low wing will experience higher G loads with respects to fuselage loads and in sequence outer high wing.
Check site below has comprehensive and detailed information about all upsets.
On a climbing turn low inside wing will stall first therefore has higher angle of attcak and feels more G's.
On a descending turn its the opposite the outside higher wing has higher angle of attack and stalls first why this happens I would like someone to explain

All information is available, on www.flighlab.net Courtesy: Bill Crawford

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