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There is a similar example for the 777X though. The new folding wingtips to fit into the existing gate sizes seems like a potential new failure mode like moving

by gfree 7y ago

There is a similar example for the 777X though. The new folding wingtips to fit into the existing gate sizes seems like a potential new failure mode like moving the 737Max engines forward. No evidence it won’t work fine but it feels like a hack.

matt123456789 7y ago
That’s closer to the type of iterative change one might expect from a new model of the same type. As long as they’re structurally sound, the folding wingtips present more of a maintenance risk than a safety risk.
donarb 7y ago
Here's a link to the FAA certification for the folding wingtips. It's pretty comprehensive. https://www.federalregister.gov/documents/2018/05/18/2018-10576/special-conditions-the-boeing-company-model-777-8-and-777-9-airplanes-folding-wingtips https://www.federalregister.gov/documents/2018/05/18/2018-10... Boeing was required to prove the load-bearing of the hinges on the wings and what types of alerts that the crews receive should a wingtip fail to lock prior to takeoff. More than one means must be available to alert the flight crew that the wingtips are not properly positioned and secured prior to takeoff. If the wingtip is not locked prior to takeoff, the plane is prevented from taking off. They even required that the electric circuit that unlocks the wingtips be automatically isolated from the circuit that folds and locks the wingtips and that that circuit cannot be re-powered during flight.
- dx034 7y ago
  Did they show simulations about what would happen if they fold during flight? Is it just rougher flight with less lift or would they severely impact the pilot's ability to steer the plane?
trhway 7y ago
why don't Boeing leave wingtips vertical like on A350 or 737? A feet of vertical winglet replaces 3 feet of horizonal wingtip. So with 3 feet high winglets Boeing cold have just avoided the need for folding.
- zz0rr 7y ago
  vertical winglets are ways to get more lift:drag out of a wing that's constrained by some width limit (airport gate spacing) or an existing wing design that you don't want to redo. they don't generate lift. for a clean sheet design you can do better with a "scimitar" wingtip that actually provides some lift and might weigh the same as a winglet. see 787. also the navy p8 which has the most efficient wing of any existing 737, and doesn't have vertical winglets (because it doesn't typically park at a gate they could go wider with these little triangular extensions)

by gfree 7y ago

matt123456789 7y ago

That’s closer to the type of iterative change one might expect from a new model of the same type. As long as they’re structurally sound, the folding wingtips present more of a maintenance risk than a safety risk.

donarb 7y ago

Here's a link to the FAA certification for the folding wingtips. It's pretty comprehensive. https://www.federalregister.gov/documents/2018/05/18/2018-10576/special-conditions-the-boeing-company-model-777-8-and-777-9-airplanes-folding-wingtips https://www.federalregister.gov/documents/2018/05/18/2018-10... Boeing was required to prove the load-bearing of the hinges on the wings and what types of alerts that the crews receive should a wingtip fail to lock prior to takeoff. More than one means must be available to alert the flight crew that the wingtips are not properly positioned and secured prior to takeoff. If the wingtip is not locked prior to takeoff, the plane is prevented from taking off. They even required that the electric circuit that unlocks the wingtips be automatically isolated from the circuit that folds and locks the wingtips and that that circuit cannot be re-powered during flight.

dx034 7y ago
Did they show simulations about what would happen if they fold during flight? Is it just rougher flight with less lift or would they severely impact the pilot's ability to steer the plane?

trhway 7y ago

why don't Boeing leave wingtips vertical like on A350 or 737? A feet of vertical winglet replaces 3 feet of horizonal wingtip. So with 3 feet high winglets Boeing cold have just avoided the need for folding.

zz0rr 7y ago
vertical winglets are ways to get more lift:drag out of a wing that's constrained by some width limit (airport gate spacing) or an existing wing design that you don't want to redo. they don't generate lift. for a clean sheet design you can do better with a "scimitar" wingtip that actually provides some lift and might weigh the same as a winglet. see 787. also the navy p8 which has the most efficient wing of any existing 737, and doesn't have vertical winglets (because it doesn't typically park at a gate they could go wider with these little triangular extensions)