777X Flies!

[PHXPhlyer]

https://www.cnbc.com/2020/01/25/boeings ... light.html

Interesting stuff about folding wing-tips

https://www.federalregister.gov/documen ... g-wingtips

PP

[boing]

Why do I get this bad feeling that folding wingtips are an uncomfortable parallel to forward mounted engines.


.

[llondel]

It's only a problem if they fold in flight, I assume. I guess that is sort of parallel to the engine thing in that if MCAS worked perfectly in flight then Boeing wouldn't be in the mess it now finds itself.

It would be interesting to know the performance of the airframe if one or both tips did something unplanned (fall off or fold). I would assume that it would still be possible to generate enough lift from what was left of the wings and flaps.

[Boac]

It didn't crash!!

One down,......

[Boac]

I wonder why is not being called the 777MAX?

[ribrash]

In normal use the wing tips will only fold up below 50 kts.

[Boac]

Hmm! There's scope for a sensor cock-up................

[ian16th]

In normal use the wing tips will only fold up below 50 kts.

How many speed sensors are monitored to control this function?

[ribrash]

In normal use the wing tips will only fold up below 50 kts.

How many speed sensors are monitored to control this function?

I don't know Ian.It was mentioned as it was getting ready for its first take off.I watched it land and as it reached the end of the runway the wings folded up.

[PHXPhlyer]

Special Conditions: The Boeing Company Model 777-8 and 777-9 Airplanes; Folding Wingtips

The term “latch” refers to the mechanism that allows the wingtip to carry flight loads in the down (flight-deployed) position. The term “lock” refers to the mechanism that prevents disconnection of the latch when the wing tip is down.

1. More than one means must be available to alert the flightcrew that the wingtips are not properly positioned and secured prior to takeoff. Each of these means must be unique in their wingtip-monitoring function. When meeting this condition, the applicant must add a function to the takeoff warning system, as required by § 25.703(a)(1) and (2), to warn of an unlocked or improperly positioned wingtip, including indication to the flightcrew when a wingtip is in the folded position during taxi.

2. In addition to a takeoff warning in accordance with § 25.703, a means must be provided to prevent airplane takeoff if a wingtip is not properly positioned and secured for flight.

3. The applicant must consider the effects of folding-wingtip freeplay when evaluating compliance to the design load requirements of 14 CFR part 25, subpart C, and the aeroelastic stability (including flutter, divergence, control reversal, and any undue loss of stability and control as a result of structural deformation) requirements of § 25.629. Thus, the effects of normal wear, and other long-term durability conditions (such as corrosion) of the folding-wingtip operating mechanism on freeplay, and its impact on loads and aeroelastic stability, must be considered. Where freeplay limitations are required to ensure aeroelastic stability, acceptable freeplay limits and freeplay check procedures must be established. If lubrication is required to control excessive wear, lubrication intervals must be established. These procedures and limitations must be documented in accordance with § 25.1529. The freeplay-check and mechanism-lubrication intervals, if required, must be documented as a certification maintenance requirement (CMR). Guidance for CMRs can be found in Advisory Circular 25-19A, “Certification Maintenance Requirements.” The effects of freeplay on wing-joint torsional and bending stiffness, as well as wing frequencies, must be evaluated when showing compliance to loads and aeroelastic stability requirements. Also, the effects of freeplay on fatigue and damage tolerance must be considered when showing compliance with § 25.571.

4. The folding wingtips and their operating mechanism must be designed for 65 knot, horizontal, ground-gust conditions in any direction as specified in § 25.415(a). Relevant design conditions must be defined using combinations of steady wind and taxi speeds determined by rational analysis utilizing airport wind data. The folding wingtip is not a control surface as specified in § 25.415(b). Therefore, in lieu of the equation provided in § 25.415(b), the hinge moment may be calculated from rational wind-tunnel data. The 1.25 factor specified in § 25.415(d) need not be applied to the portion of the system that is isolated in flight and is not critical for safe flight and landing. The folding-wingtip system must be designed for the conditions specified in § 25.415(e), (f), and (g). Runway roughness, as specified in § 25.491, must be evaluated separately up to the maximum relevant airplane ground speeds. All of the above conditions must be applied to the folding wingtips in the extended (flight-Start Printed Page 23212deployed), folded, and transient positions.

5. The airplane must demonstrate acceptable handling qualities during rollout in a crosswind environment, as wingtips transition from the flight-deployed to folded position, as well as during the unlikely event of asymmetric wingtip folding.

6. The wingtip-fold operating mechanism must have stops that positively limit the range of motion of the wingtips. Each stop must be designed to the requirements of § 25.675.

7. The wingtip hinge structure must be designed for inertia loads acting parallel to the hinge line. In the absence of more rational data, the inertia loads may be assumed to be equal to KW as referenced in § 25.393. Hinge design must meet the requirements of § 25.657.

8. In lieu of § 25.1385(b): The forward position lights must be installed such that they consist of a red and a green light spaced laterally as far apart as practicable, and installed forward on the airplane, so that, with the airplane in the normal flying position and with the wingtips in the folded position for ground operations, the red light is on the left side and the green light is on the right side at approximately the level of the wingtips in the takeoff configuration. Each light must be approved and must meet the requirements of § 25.1385(a) and (d). The lights must not impair the vision of the flightcrew when the wingtips are in the folded and transient positions.

9. The applicant must include design features that ensure the wingtips are properly secured during ground operations, to protect ground personnel from bodily injury as well as to prevent damage to the airframe, ground structure, and ground support equipment.

10. The wingtips must have means to safeguard against unlocking from the extended, flight-deployed position in flight, as a result of failures, including the failure of any single structural element. All sources of airplane power that could initiate unlocking of the wingtips must be automatically isolated from the wingtip-fold operating system (including the latching and locking system) prior to flight, and it must not be possible to restore power to the system during flight. The wingtip latching and locking mechanisms must be designed so that, under all airplane flight-load conditions, no force or torque can unlatch or unlock the mechanisms. The latching system must include a means to secure the latches in the latched position, independent of the locking system. It must not be possible to position the lock in the locked position if the latches and the latching mechanisms are not in the latched position, and it must not be possible to unlatch the latches with the locks in the locked position.

PP

[Boac]

"Hello - No 1 airspeed sensor here". "I heard you call 'V1' but I have a reading of 45kts, so I'm folding the tips, out"

[llondel]

I would have said a safer approach would be to also require weight on the landing gear.

[PHXPhlyer]

Read #10 in post 10.

PP

[Boac]

PP - since when was V1 'flight'?

[PHXPhlyer]

I don't believe I said that.

PP

[Rwy in Sight]

Shouldn't there be a default on the extended position?

[ian16th]

Shouldn't there be a default on the extended position?

Not if the a/c is at the gate.

[Boac]

So what did you mean,PP?

[Rwy in Sight]

Shouldn't there be a default on the extended position?

Not if the a/c is at the gate.

I was thinking in terms of the default position to be on extended position ]. I am not sure how to put that in engineering term.

BOAC I guess it has to do that after V1 flying is practically assured and thus wing-tips extended.

[Boac]

"thus wing-tips extended." - unless folded?