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> be hooked up to any of the redundant power buses. There are multiple busses, but you almost always have an option to tie the two busses together, so one ge

> be hooked up to any of the redundant power buses. There are multiple busses, but you almost always have an option to tie the two busses together, so one generator can drive both sets of loads. You can also add a battery through an inverter to carry loads. You can also turn on the APU and use it's output to drive loads. They may have had a more severe failure.

phire 2y ago
Tying buses together is a manual operation. All indications are that the pilots didn't have enough time to get that far in the checklist. It's also not that important to restore AC power. The standby bus automatically brings the standby instruments online in the event of a failure, and not that hard to restore the majority of instruments by connecting the main DC bus to batteries. The battery has enough power for 30min of flying, or a full hour if you have the dual-battery option. > They may have had a more severe failure. While we only have evidence of bird strikes on one engine, the actions of the pilots seem to suggest that they lost both engines. They were rushing to get back to a runway.
- zmgsabst 2y ago
  The struck engine was still spinning — you can see the visual distortion from its thrust reverser being deployed while on the runway.
f1shy 2y ago
You do not have time to start the APU. Moving any switch is a procedure with a checklist, at that hight, once you lost both engines… they had no chance.
- timewizard 2y ago
  It's just a button press. US Airways 1549 had the captain starting the APU within seconds after their birdstrike. Your biggest concern after starting is likely exhaust temperature.
  - f1shy 2y ago
    Exactly! And he was called out because he did that without following the stablished procedures! Also is not instant, will take a minute or two. The APU is a turbine that takes time to start. Maybe they did turn in on, but 2 minutes too late. We don’t know. He was a super pilot, who had extreme good understanding of all systems in the plane, and many ours on that plane. You cannot expect that (and do both want that!) from an average pilot. It seems right now that this very accident may have been caused by not following the procedures.
    - phire 2y ago
      Or they started the APU, but never got around to connecting its generator to the main bus. That's a second button press, after confirming it has successfully started.
    - nctk21 2y ago
      If by "called out" you imply criticised, then that is not correct. Instead, the NTSB final accident report (https://www.ntsb.gov/investigations/accidentreports/reports/aar1003.pdf https://www.ntsb.gov/investigations/accidentreports/reports/..., p. section 2.3.1) praises the specific quick action: "Although the flight crew was only able to complete about one-third of the Engine Dual Failure checklist, immediately after the bird strike, the captain did accomplish one critical item that the flight crew did not reach in the checklist: starting the APU. Starting the APU early in the accident sequence proved to be critical because it improved the outcome of the ditching by ensuring that electrical power was available to the airplane. Further, if the captain had not started the APU, the airplane would not have remained in normal law mode. This critical step would not have been completed if the flight crew had simply followed the order of the items in the checklist. The NTSB concludes that, despite being unable to complete the Engine Dual Failure checklist, the captain started the APU, which improved the outcome of the ditching by ensuring that a primary source of electrical power was available to the airplane and that the airplane remained in normal law and maintained the flight envelope protections, one of which protects against a stall." The final report also gave a new safety recommendation (A-10-66, p. 124) to develop more appropriate (shorter) checklist for dual-engine failure specifically for low-altitude incidents.
- gorm 2y ago
  Wasn't the main issue here that the airport authority had put an obstacle in an area that was supposed to be an obstacle-free zone?

phire 2y ago

Tying buses together is a manual operation. All indications are that the pilots didn't have enough time to get that far in the checklist. It's also not that important to restore AC power. The standby bus automatically brings the standby instruments online in the event of a failure, and not that hard to restore the majority of instruments by connecting the main DC bus to batteries. The battery has enough power for 30min of flying, or a full hour if you have the dual-battery option. > They may have had a more severe failure. While we only have evidence of bird strikes on one engine, the actions of the pilots seem to suggest that they lost both engines. They were rushing to get back to a runway.

zmgsabst 2y ago
The struck engine was still spinning — you can see the visual distortion from its thrust reverser being deployed while on the runway.

f1shy 2y ago

You do not have time to start the APU. Moving any switch is a procedure with a checklist, at that hight, once you lost both engines… they had no chance.

timewizard 2y ago
It's just a button press. US Airways 1549 had the captain starting the APU within seconds after their birdstrike. Your biggest concern after starting is likely exhaust temperature.
- f1shy 2y ago
  Exactly! And he was called out because he did that without following the stablished procedures! Also is not instant, will take a minute or two. The APU is a turbine that takes time to start. Maybe they did turn in on, but 2 minutes too late. We don’t know. He was a super pilot, who had extreme good understanding of all systems in the plane, and many ours on that plane. You cannot expect that (and do both want that!) from an average pilot. It seems right now that this very accident may have been caused by not following the procedures.
  - phire 2y ago
    Or they started the APU, but never got around to connecting its generator to the main bus. That's a second button press, after confirming it has successfully started.
  - nctk21 2y ago
    If by "called out" you imply criticised, then that is not correct. Instead, the NTSB final accident report (https://www.ntsb.gov/investigations/accidentreports/reports/aar1003.pdf https://www.ntsb.gov/investigations/accidentreports/reports/..., p. section 2.3.1) praises the specific quick action: "Although the flight crew was only able to complete about one-third of the Engine Dual Failure checklist, immediately after the bird strike, the captain did accomplish one critical item that the flight crew did not reach in the checklist: starting the APU. Starting the APU early in the accident sequence proved to be critical because it improved the outcome of the ditching by ensuring that electrical power was available to the airplane. Further, if the captain had not started the APU, the airplane would not have remained in normal law mode. This critical step would not have been completed if the flight crew had simply followed the order of the items in the checklist. The NTSB concludes that, despite being unable to complete the Engine Dual Failure checklist, the captain started the APU, which improved the outcome of the ditching by ensuring that a primary source of electrical power was available to the airplane and that the airplane remained in normal law and maintained the flight envelope protections, one of which protects against a stall." The final report also gave a new safety recommendation (A-10-66, p. 124) to develop more appropriate (shorter) checklist for dual-engine failure specifically for low-altitude incidents.
gorm 2y ago
Wasn't the main issue here that the airport authority had put an obstacle in an area that was supposed to be an obstacle-free zone?