Good demonstration dude. However, 00:53, there's no hydraulic pump in the APU. The hydraulic lines are for the accumulators and empennage flight controls, etc.
I still can't believe that there isn't any proper redundancy built into the elevator trim in most aircraft... At least something that puts the elevator in a centered position if the jackscrew were to fail.
You would think that after Alaska 256, Boeing, Airbus, and the FAA would have the airlines install something to keep the horizontal stabilizer straight so they can get the plane safely on the ground and get the jack screw replaced. Hundreds on lives on one plane depend on the jackscrew to work.
@@tails4674 I know! But a single point of failure in the design failing had everything to do with the plane crashing! Sure, maintenance was the cause in this case, but with any form of redundancy in the design it wouldn't have been catastrophic.
@@ObsidianParis its an acme thread for a jack screw stupid strong like a buttress thread. Ball screws have a certain radius and are much more accurate but cant handle the loads generated in flight. Unless boeing pulled a rabbit outa their ass.
@@8710ify I beg to differ. Either a jack screw or a ball screw a lack of lubrication will make both fail. I have the drawings for the dc-9. My friend gave them to me when he retired as a maintenance tech for air Canada. There is an extra page added in the book for the Jack screw. It's literally stapled in. New jack screw procedure.
No. Mechanic in hell hole uses inter phone to converse with mechanic in cockpit to operate operate trim motor when inspecting and adjusting stabilizer.
Thanks. Not sure of the designing reason for the cable. It connects the horizontal stabilizer to the stabilizer position module which in turn give a signal to the array of electronics than govern the movement of the stabilizer.
BigIronTV these cables are the only backup pitch control during the electrical blackout or control channel failure. In the event FBW fails, the cables directly command stabilizer trim.
why not? its easy to maintain and insoect, and it well proven and the fault tree are very well ressearched and evaluated. many times thebkeep it simple principle is the way to go.
Jackscrew sure is big, very sad Alaska26 crashed due to lack of inspection.
Stowaway passengers must LOVE the "hell hole", presuming adequate oxygen supply and electric undies.
Good demonstration dude. However,
00:53, there's no hydraulic pump in the APU. The hydraulic lines are for the accumulators and empennage flight controls, etc.
Nice tour. Learned about the "Jackscrew" and it's utilization. Thanks.
I still can't believe that there isn't any proper redundancy built into the elevator trim in most aircraft... At least something that puts the elevator in a centered position if the jackscrew were to fail.
You would think that after Alaska 256, Boeing, Airbus, and the FAA would have the airlines install something to keep the horizontal stabilizer straight so they can get the plane safely on the ground and get the jack screw replaced.
Hundreds on lives on one plane depend on the jackscrew to work.
I was thinking the same thing. Remember Alaska air?
The Alaska Flight 256 had nothing to do with the Pitch Trim System design itself. It was purely a fault of Alaska Airlines maintenance.
@@tails4674 I know! But a single point of failure in the design failing had everything to do with the plane crashing! Sure, maintenance was the cause in this case, but with any form of redundancy in the design it wouldn't have been catastrophic.
Awesome video.
Perfect system knowledge.
Thank you!
Im not seeing a whole lot of grease on that jack screw.
On the other hand, the special shape of its threading makes me think it's probably actuated by a ball-driven nut…
@@ObsidianParis its an acme thread for a jack screw stupid strong like a buttress thread. Ball screws have a certain radius and are much more accurate but cant handle the loads generated in flight. Unless boeing pulled a rabbit outa their ass.
@@rapturekevin It's a ballscrew. As stated in the 777 manuals and various airworthiness directives over the years.
@@8710ify I beg to differ. Either a jack screw or a ball screw a lack of lubrication will make both fail. I have the drawings for the dc-9. My friend gave them to me when he retired as a maintenance tech for air Canada. There is an extra page added in the book for the Jack screw. It's literally stapled in. New jack screw procedure.
Q: Do drug smugglers commonly conspire with ground crew and/or mechanical crew to transport contraband?
as a mechanic i heard some stories
Really cool video, thanks for posting.
All part fail eventually no proper lubrication.
You might have wanted to use a flashlight so you could see a little better
I work with this kind of screws and I dont see rest of lubrication. Its this mechanism some kind of lubrication ???
Fascinating!!! Thanks!
how much would be the linear speed of that jack screw
Jack screw : Very heavy and very strong but some time fail !
Can that screwjack be activated from inside the 'hellhole'. Just to check smooth operation and limit switch settings maybe..
No. Mechanic in hell hole uses inter phone to converse with mechanic in cockpit to operate operate trim motor when inspecting and adjusting stabilizer.
This is really cool. Why have mechanical cables feeding back trough the bulkhead where do they lead?
Thanks. Not sure of the designing reason for the cable. It connects the horizontal stabilizer to the stabilizer position module which in turn give a signal to the array of electronics than govern the movement of the stabilizer.
BigIronTV these cables are the only backup pitch control during the electrical blackout or control channel failure. In the event FBW fails, the cables directly command stabilizer trim.
Hi.may i ask you explain one more time with more detail,
Screw-threads of any size can collect debris over time and are liable to jam: should the thing decide to lock-up during a flight, it's goodbye.
nice explanation.
Thanks
Bets video about rudder trim!
Hey, thank you for the video, next time take your FLASHLIGHT with you ;) the video was a bit dark sometimes.
Awesome
Bro is just stuck inside the 777 ☠️
Cables still? Why would a modern aircraft use steal cables?
as backup for the fly-by-wire system
Steel cables
With steel cables you are always mechanically connected with the flight controls and so you have always control of the aircraft.
Because it works?
Stuart sugden shut up Stuart
Jack screw looks like it is lacking lube
Hyd lines from APU??? REALLY??? 😂😂😂
The hydraulics are pressurised from the APU so why should that be weird?
Are you sure about that? To my knowledge the APU provides air and electricity. The electricity is then used to power the electrical hydraulic pumps.
Yeah, thought I heard wrongly, hydraulic pumps from APU???
Extremely shocking old fashion tech. Just the idea to have wires for sensoring...
why not? its easy to maintain and insoect, and it well proven and the fault tree are very well ressearched and evaluated. many times thebkeep it simple principle is the way to go.
@@johndoe1909 It a possible and unnecessary source of error compared to direct linkage.