When something has to move, not real far, not real fast, but must STAY when not being moved, a screw is a favorite device.
When you park your camper-trailer, the leg on the tongue has a jacking screw so you can level the camper for better cooking and sleeping.
To raise a house and hold it there, use a jack-screw.
Race-cars need to trim their wheel springs for height, also side-side and front-back for track force balance. Look in the rear window of a NASCAR 'stocker' and you can see the jack-screws.
Hydraulic cylinders are an alternate device. They can be made to move faster. They get awkward if you need HIGH force in small weight. And they don't "hold" well. The valves leak. A JCB/backhoe parked arm-up, the arm will drop in days. And the hoses burst, allowing sudden falls.
When aircraft got too big to man-handle the large control surfaces, some kind of boost was needed. Spruce Goose advanced this art, though I don't know if it was cylinders or screws. Jack-screws are an obvious choice for "trims" which are set rarely and must hold huge force. I believe aircraft flaps (extra wing area slid out for low speed) are routinely jack-screwed, it makes a neat simple and mostly reliable action. I'd bet that elevators etc are also jack-screwed.
A further after-the-crash feature of jackscrews is that they tend to hold their last setting even after great violence. Sometimes it is found that the screw was in the right position but the end-link had not been fastened properly so the flap was not where it was supposed to be; this suggests talking to the last few mechanics who worked in this area.
I always heard that about Helicopters - definitely appropriate. That and the "jesus bolt" -- or jesus nut to some.... Jesus nut - Wikipedia
If you have ever flown in helicopters regularly, as I once did, you know everything there is to know about the Jesus Nut.
traderbam - With the exception of very rudimentary radar data, that article is 100% conjecture. Please read it again with a more critical eye, and you will see language use that shows it to all be guesswork, assumptions, hypothesizing, simulation, theory, presumption, and speculation -- with no factual data at all.
DF96 - Lol!! Being that a helicopter is "1000 moving parts loosely organized around an oil leak," I think that is precisely where that term is from!!
DF96 - Lol!! Being that a helicopter is "1000 moving parts loosely organized around an oil leak," I think that is precisely where that term is from!!
Last edited:
I often grab a window seat around the trailing edge of the wing. This lets me watch the jackscrews in action, which lower and raise the flaps for high-lift, high-drag, low speed flight. (Takeoff and landing). They're right there in the wing, undisguised, visible as plain as day. When you see them in action you'll suddenly notice the relatively loud and extremely distinctive noise the screw-motor makes when twisting the jackscrew. See it and hear it just a couple of times, and the sound becomes embedded in your memory forever after. Now even when you're way up front, in an aisle seat in First Class, swilling down Roederer champagne, and you hear that sound you'll immediately know the flaps are being lowered or raised.
Yes, I do that too.. apart from the first class bit!
Different planes have different sounds too - airbus screws have a distinct sound!
I forgot which model of the Dash 8 is worst, but on a flight a long time ago there was an announcement that the loud sound of the landing gear extending was perfectly normal and not to be scared - it was LOUD.
Damned right!
I worked in Oregon once... The last leg of the flight was a small 6? 10? seater plane, nothing blocking off the cockpit. The guy that usually flew it - chewed an unlit cigar, cowboy hat, ex military pilot... flew by using the stall waring indicator as a guide... I was always happy to get off...
I worked in Oregon once... The last leg of the flight was a small 6? 10? seater plane, nothing blocking off the cockpit. The guy that usually flew it - chewed an unlit cigar, cowboy hat, ex military pilot... flew by using the stall waring indicator as a guide... I was always happy to get off...
As there are very few direct flights out of Victoria to our general travel destinations, so our short jitney shuttle from YYJ to YVR is usually a DH3 or 4 (the latter a Cadillac compared to the sardine can that is the DH3. It’s a short hop, for which both types are quite acceptable, but they do rattle and squeak rather more than the Boeing 737-800 (73H) or Airbus 320 /321 that is the usual equipment for the 2nd/3rd legs of flight to OGG or BDA.
As the DeHavilands are much smaller planes, you’re less insulated from some of the mechanical noises while loading - we like to joke that “that’s just the last few turns of them winding up the rubber bands”
Hopefully, the investigations into the Ethiopian crash, and perhaps a closer second look at the Lion Air disaster will get closer to the truth of what happened. With a total of something like 350 active service units now grounded, and a substantial number on order or in production that will not leave the parking lot until the solutions are found and independently certified, this has gotta be costing Boeing more than just the $26B in market devaluation over the past few days. Should they be paying for extra flight insurance for those brave guinea pigs booking their flights after “ hey, it was a software glitch, and we’ve found the fix”?
There is at least one online travel reservation company who’ve announced their intention to upgrade their software to allow you to exclude the models of planes you’d like to avoid.
As the DeHavilands are much smaller planes, you’re less insulated from some of the mechanical noises while loading - we like to joke that “that’s just the last few turns of them winding up the rubber bands”
Hopefully, the investigations into the Ethiopian crash, and perhaps a closer second look at the Lion Air disaster will get closer to the truth of what happened. With a total of something like 350 active service units now grounded, and a substantial number on order or in production that will not leave the parking lot until the solutions are found and independently certified, this has gotta be costing Boeing more than just the $26B in market devaluation over the past few days. Should they be paying for extra flight insurance for those brave guinea pigs booking their flights after “ hey, it was a software glitch, and we’ve found the fix”?
There is at least one online travel reservation company who’ve announced their intention to upgrade their software to allow you to exclude the models of planes you’d like to avoid.
For the record, I want it noted that I have no field of expertise, and I have only the most basic conceptual understanding of roofing and related structures.
I still think that Boeing will have to work very hard to rebuild the customers trust. If they had been just a little bit more open about this case, and not witheld information to such an extent, everything would have gone a bit more smoothly.
I don't have tv, and sports involving any form of ball or equivalent useage object, repeatedly fail to trigger any interest on my part. Can I still do couch comments? I went to sit in the couch for writing this, only so maybe I could have some relation to your slighly sarcastic but still friendly observation.
I saw an article in the LA Times this morning that seems like a good overview of what the design flaws may be and the long history of the 737.
How a 50-year-old design came back to haunt Boeing with its troubled 737 Max jet - Los Angeles Times
What do the experts make of this?
How a 50-year-old design came back to haunt Boeing with its troubled 737 Max jet - Los Angeles Times
What do the experts make of this?
- Status
- Not open for further replies.