if it had similar valving to the 747 rudder that required a fleet wide retro fit why didn’t they focus on the valve early on when the 737 rudder started acting up?
I have no idea what the 747 rudder issue was, so I have no way to respond.
Given the vastly different sizes of aircraft, there’s a good chance the parts and possibly even suppliers of the rudder system are entirely different. There’s no particular reason to think the same problem would arise in that case.
Any issue on one aircraft where the parts are believed to be used on another - even by other OEMs - gets mandated for correction by airworthiness directives (AD) as well. You see this a lot with smaller standalone components like chemical oxygen generators or life vests; it’s the particular units that are called for rework or replacement and any further installation of the unit on any aircraft renders it not airworthy. Inadvertently reinstalling an AD part can result in new ADs being issued.
Part of my job is actually to check whether new ADs issued for other OEMs can or do affect my customers. If a customer asks my firm to install a given part number of something, we run verifications to make sure the installation isn’t subject to an AD. If the valve on a 737 were the same as on a 747 and the 747 valve had mandated corrective action, the action absolutely would have extended to the 737 line.
I understand that part-for-part would get attention but this is along the order of part design-for-part design.
It would be something an engineer would likely be aware of. Generally someone in a particular line of work will be exposed to a grapevine of information.
It does get more complicated at that level, for sure, but any good approval and design organization should catch this and there are multiple opportunities to do so in a system design. We know not all organizations are good at this, of course.
If a company like AirframesOEM ordered valves from ABC Valve Corp for their 7Y7 program, then that part had in service issues that required rectification, if ABC is contracted for valves for 7X7 program later, ABC should know and avoid providing parts with the same design flaw. AirframesOEM should have the integration expertise to understand how that flaw comes about, and to plan and require that not only ABC not permit it to happen, but also to ensure they don’t reintroduce the issue through their own use of the parts.
All the system safety assessments are also opportunities to catch this stuff, as are oversight from regulatory agencies. It’s incredibly complex but knowledgeable people are generally involved the whole way.
I absolutely have been asked “part X failed on plane Z, does my aircraft have X?” In some cases it takes research, in others it’s an easy answer of “different part, different supplier, different mechanics (e.g. electric vs hydraulic actuation).”
In an accident/incident investigation, an entire team of OEM people get gathered together to assess what they know as information comes up, while their in-house investigator communicates with the investigation agency (e.g. NTSB).
While I hate to call it routine, it’s definitely part of the whole structure of assuring continued airworthiness.
OK that’s what I’d expect. As I understand it the part worked fine but under certain conditions of hot hydraulic oil hitting one cylinder it would lock up causing problems for the other cylinder.
There was a Northwest 747 fllying from Alaska where part of the rudder get stuck full left. “Went apeshit” to use LSLGuy’s technical term. Fortunately, the 747 has a two-piece rudder. The remaining rudder gave the crew enough control to return to Anchorage and land safely.
I think the problem turned out to be an end cap on a hydraulic cylinder in the rudder mechanism. The internal pressure caused the cap to split along the threads. Either the threads were cut wrong, or the cap was made of the wrong alloy; something like that.
Which I think was different from the issue that caused the 737 rudder problems.
Sorry, I don’t get it. Is it referencing a recent incident, or is the Cherokee known to be chronically underpowered?
If that’s an accurate description of the 747 problem (and I’m not doubting you), then yes, the 737 issue was totally different.
Yes. Pretty much all lightplanes can barely get off the ground with much of a load on a hot day. The comic is massive hyperbole, but the idea fits for pretty much any of the basic trainer lightplanes.
Yeah, airplanes area a balancing act. You can choose some combination of speed, payload, range, or economy. I’m not a Piper pilot, but I’ve heard that the Cherokee 140 originally had a 140 hp engine (hence the name – although I’ve seen Cherokee 140s with 160 hp engines). I’ve read that the rear seats were taken out and flown as two-seat trainers because removing the seats saved weight. But as for the compromise, I’ll use Cessnas because that’s what I’ve flown. [NB: With over half a century of production, numbers will vary.]
A Cessna 150 or 152 two-seater has a 100 hp or 115 hp engine, making them very economical; but with full tanks (26 gallons) you only have about 320 pounds for people and baggage; and it only cruises at about 100 smph. Since it can’t go far or carry much, it makes a good trainer – if you and your instructor weigh less than 320 pounds together. So you get economy, but that’s it. A Cessna 182 Skylane is bigger and more powerful. It has a maximum speed of about 170 smph, which is pretty fast for a single-engine light plane, and you can carry four adults and full tanks for around 1,000 miles. But they’re more expensive to buy, and more expensive to operate. So you get speed, range, and payload, but you’re going to pay for it. A Cessna 172 Skyhawk is in the middle. It’s reasonably fast (about 140 smph max.), it’s relatively inexpensive ( 
) to buy and operate, and you can even fill the tanks and the seats, if one or two of the passengers are small, over hundreds of miles.
But I’m rambling.
Anyone know where I can find an 80-pound instructor?
Anyone know where I can get a -10 pound instructor?
Some sort of highly localized antigravity gadget might be useful in that situation.
Nostalgia warning: Airline Menus From the Past Show What We’re Missing Out On | Dusty Old Thing
Not at all; thank you and @LSLGuy for the answers.
Yeah, similar issue here. But I guess you can have a decently long lesson on half full tanks, which saves roughly 100lb.
here you go … you did NOT mention “competent” …
I’m NOT going to reinflate him. Just saying.
Take the Aeronca Champ I learned in from Stan Robertson (father of GA in Connecticut, Robertson Field). Me at ~200 lbs in front with Stan @140 in back (tandem seating), we’d would line up on the runway; I’d firewall the throttle (it was actually on the cockpit wall on my left but “firewalling” is meme); the prop would flail enough breeze past the plane; the mighty 65 hp Continental roaring unmuffled; and I’d nudge the stick forward to get the tail wheel off the ground and streamline us for more speed. At some point, the plane would feel lighter and back again on the stick - liftoff - to about 15 feet - stick forward again to level out for the next increment of speed (how fast you say?) Pay no attention to the airspeed indicator wildly vacillating. Feeling light again it was time to clamor up into the sky. I’d make a gradual left then right to allow the high-speed Cessna 150s to pass. Stan had an arrangement to fly a shorter inside pattern with the two of us aboard. In fact, I’d land in the grass between the runway and taxiway while learning.
Fast forward to hour nine and time to solo. What a difference the missing Stan in back made! Throttle up and immediately push forward on the stick then back and climb out. I’d be at pattern altitude by the time I’d reach the end of the runway. With a stiff breeze, I’d cut the throttle on the downwind leg just even with the end of the runway. Stan said to never trust the engine so I had to make a beeline toward the end - no long base or final leg. Also no flaps on the plane. To kill airspeed and altitude, it was cross controls (cattywampus) to get back and aligned to land. Just about full stall with the tail wheel kissing the ground first was ideal. Roll a few dozen feet and cut across the grass to the taxiway - rinse and repeat for the rest of the hour. Good times, mostly with the door off (Stan would do aerial photography for the newspapers…).
A trip down memory lane 1969ish.
If you do you’ll put a big smile on his face.
Anyone up for a visit to Wasilla, Alaska?