5 ms·

If we're going to do failure modes effects analysis, we'd need to know what the mechanism is in order to enumerate the possible failure modes (along with their

If we're going to do failure modes effects analysis, we'd need to know what the mechanism is in order to enumerate the possible failure modes (along with their likelihoods). For example, if the wing tips are actuated by a worm drive, then there is no "and the locking mechanism...just disappears;" The drive would be the locking mechanism. There are probably also suitable bistable mechanisms that lock in the open and closed positions, requiring actuation to unlock them. > What happens? In the large, I'm sure the teams of engineers at Boeing have it covered.

theoh 8y ago
The conventional locking mechanism that I've seen documented is like the lock on a bank vault: several pins, aligned with the hinge, which slide parallel to it, locking inboard and outboard sections in place. This locking mechanism means that the number of pins and their dimensions can be scaled to handle arbitrary loads, and there's no single point of failure.
- VectorLock 8y ago
  Thats what it looks like just looking at the video. Some kind of pins that slide in when the hinge is fully down. So one in a billion confluence of errors makes the pins disengage in the middle of a flight. What happens?
  - theoh 8y ago
    Well, the lift on the wingtip is going to make it fold up. In the worst case, I guess it might break off, but it's a very small part of the wing, and it presumably doesn't contain fuel tanks. Chances of it damaging the inboard section have to be quite small and I wouldn't be surprised if the hinge is designed to cope with the forces involved. For comparison, see these stories of aircraft flying safely with a much larger wing area unintentionally folded: https://theaviationist.com/2014/02/19/us-navy-fighters-folded-wings/ https://theaviationist.com/2014/02/19/us-navy-fighters-folde...
    - NickNameNick 8y ago
      It might not even fold up. The wingtip probably incorporates some amount of wash-out (reduced or even negative angle of attack, as compared with the wing root) There might not be much or any upward force on it. Depending on how the actuators work, they may be strong enough to hold the wingtip in place without the locking mechanism.
      - rlpb 8y ago
        If there's little or no upward force on it, they might as well not have the wingtips since they wouldn't be generating lift! (devices such as winglets excepted; I don't think that applies here)
        AceyMan 8y ago
        > [...] except for devices such as winglets You answered your own question and didn't know it. If the additional width added here has no net lift benefit but served as winglets do to reduce induced drag from the 'mixing boundary' but even more effectively – since the outward moving airmass doesn't have to accelerate (read: change direction) when it hits the base of the winglet, but instead gets to continue smoothly migrating to the tip – I can absolutely see how that would pay off in efficiency gains. Wings can be designed to have nearly arbitrary amounts of lift: reducing drag for a given amount of lift is the secret sauce, which could very well be what this design achieves. (me: FAA Licensed Dispatcher)
        theothermkn 8y ago
        Licensed to dispatch planes or not, everything you've said about fluid dynamics is wrong. You first seem to have confused "winglets" with "vortex generators." I think. The only winglike thing that messes with the viscous boundary layer is a VG. Second, winglets have nothing to do with a "mixing boundary;" They do what they do, even in completely inviscid flow, where there is no boundary layer. Third, whether an air mass has to "accelerate" has nothing to do with efficiency. For example, air is adiabatically compressed as it meets the stagnation point on a wing, or en masse as it enters a subsonic diffuser (jet intake). The former is a consequence of fluid flow in general, and the latter is by design. Both are completely isentropic and lead to no total pressure losses in the flow. Finally, it's meaningless to say that wings "can be designed to have...arbitrary amounts of lift," and plainly incorrect to say that drag is the "secret sauce." (Aeroelastic flutter? Wing mass? Control moments? Moment coefficients?) Reducing induced drag is done in exactly two ways. You either increase the span or put a winglet on so you can effectively increase the span while still being able to park the plane. Nobody thinks they can do brain surgery, but everybody is a fluid dynamicist.
VectorLock 8y ago
I'm sure they've covered it but I'm curious as to what exactly happens.

theoh 8y ago

The conventional locking mechanism that I've seen documented is like the lock on a bank vault: several pins, aligned with the hinge, which slide parallel to it, locking inboard and outboard sections in place. This locking mechanism means that the number of pins and their dimensions can be scaled to handle arbitrary loads, and there's no single point of failure.

VectorLock 8y ago
Thats what it looks like just looking at the video. Some kind of pins that slide in when the hinge is fully down. So one in a billion confluence of errors makes the pins disengage in the middle of a flight. What happens?
- theoh 8y ago
  Well, the lift on the wingtip is going to make it fold up. In the worst case, I guess it might break off, but it's a very small part of the wing, and it presumably doesn't contain fuel tanks. Chances of it damaging the inboard section have to be quite small and I wouldn't be surprised if the hinge is designed to cope with the forces involved. For comparison, see these stories of aircraft flying safely with a much larger wing area unintentionally folded: https://theaviationist.com/2014/02/19/us-navy-fighters-folded-wings/ https://theaviationist.com/2014/02/19/us-navy-fighters-folde...
  - NickNameNick 8y ago
    It might not even fold up. The wingtip probably incorporates some amount of wash-out (reduced or even negative angle of attack, as compared with the wing root) There might not be much or any upward force on it. Depending on how the actuators work, they may be strong enough to hold the wingtip in place without the locking mechanism.
    - rlpb 8y ago
      If there's little or no upward force on it, they might as well not have the wingtips since they wouldn't be generating lift! (devices such as winglets excepted; I don't think that applies here)
      - AceyMan 8y ago
        > [...] except for devices such as winglets You answered your own question and didn't know it. If the additional width added here has no net lift benefit but served as winglets do to reduce induced drag from the 'mixing boundary' but even more effectively – since the outward moving airmass doesn't have to accelerate (read: change direction) when it hits the base of the winglet, but instead gets to continue smoothly migrating to the tip – I can absolutely see how that would pay off in efficiency gains. Wings can be designed to have nearly arbitrary amounts of lift: reducing drag for a given amount of lift is the secret sauce, which could very well be what this design achieves. (me: FAA Licensed Dispatcher)
        theothermkn 8y ago
        Licensed to dispatch planes or not, everything you've said about fluid dynamics is wrong. You first seem to have confused "winglets" with "vortex generators." I think. The only winglike thing that messes with the viscous boundary layer is a VG. Second, winglets have nothing to do with a "mixing boundary;" They do what they do, even in completely inviscid flow, where there is no boundary layer. Third, whether an air mass has to "accelerate" has nothing to do with efficiency. For example, air is adiabatically compressed as it meets the stagnation point on a wing, or en masse as it enters a subsonic diffuser (jet intake). The former is a consequence of fluid flow in general, and the latter is by design. Both are completely isentropic and lead to no total pressure losses in the flow. Finally, it's meaningless to say that wings "can be designed to have...arbitrary amounts of lift," and plainly incorrect to say that drag is the "secret sauce." (Aeroelastic flutter? Wing mass? Control moments? Moment coefficients?) Reducing induced drag is done in exactly two ways. You either increase the span or put a winglet on so you can effectively increase the span while still being able to park the plane. Nobody thinks they can do brain surgery, but everybody is a fluid dynamicist.

VectorLock 8y ago

I'm sure they've covered it but I'm curious as to what exactly happens.