Watching the NatGeo series Mayday, and in S01E06, around seven minutes in, we get this quote.
Accompanied of course by a reenactment of a pilot straining against the controls. I could’ve sworn I’ve seen a thread on here before where our resident pilots came in and said all the scenes in movies/TV showing such were pretty much BS, that controls are pretty responsive and that pulling that hard on them would probably make the plane go crazy. I only ask because the series has generally been quite accurate, so I’d find it unusual if they got something so simple so wrong. So what’s the SD?
My WAG is that it was probably true at some point in time. Have you ever driven a car that didn’t have power steering? That kind of physical effort. And maybe that’s still the case on some tiny one-man planes. But an MD-80? (For non-aviation types, like me, check out the photo on Wikipedia.) Absolutely ridiculous to think that the pilot puts manual effort into any of that. No human could do it.
That’s what I thought. A few minutes more in and it gets even more ridiculous, at one point saying the fate of the plane and everyone in it hangs on the strength of their arms, and the rest of the reenactment is them under considerable strain.
Newer aircraft, at least large, commercial aircraft, are fly-by-wire, meaning that the yoke is not directly connected to the control surfaces. The pilot moves the yoke, then the computer interprets that and translates it into the desired movement. In some systems, such as the Airbus flight that crashed into the ocean a few years back, under normal circumstances the computer won’t let the pilot make inputs that would push the plane out of its flight envelope. Even in the event of a mechanical failure, these systems would ‘feel’ the same way to the pilot, since there isn’t a physical connection from the yoke to the control surfaces.
Older aircraft that weren’t/aren’t fly-by-wire will have some sort of linkage between the yoke and the control surfaces. Cables, hydraulic systems, etc. In the event of a complete failure of all hydraulic systems, such as the case of United 232, it was very difficult for the pilots to move the yoke–even putting both of them on it didn’t do a lot of good. But that was a very unique case, since all 3 hydraulic systems had been ruptured and bled out. Under normal circumstances, again, even with a failure of 2 of the redundant systems, there was still a third to provide that assistance with the yoke.
I’m not sure about the specifics of the MD80, but there certainly are (rare) scenarios where the pilot would have to put significant force on the yoke, so it’s not completely unheard of.
The plane in question was not in normal working order. From what I gather, the stabilizer was jammed, pushing the nose of the plane down, and the pilots were fighting that to maintain level flight and keep the plane from going into a dive. From the Wikipedia page for Alaska Airlines Flight 261:
It looks like there are plenty of sources there, including the full NTSB report, if you are interested.
I skimmed some stuff before asking here but seem to have missed that. Thanks for pointing it out though, ignorance fought! Glad to know this show is as good as I’ve heard and I’m the inaccurate one
First, the cockpit is so cramped that you wouldn’t be able to get much help anyway.
Second, bringing outsiders into that environment would be a recipe for disaster, since they just don’t have the training that the crew does. As an example, if I were flying a plane, and the Pilot Not Flying said “my airplane,” I’d instinctively take my hands and feet off the controls and acknowledge “your airplane.” Civilians…not so much.
Third, with that many elbows and a-holes in the confined space, somebody is going to bump the throttles, or deploy the landing gear (likely above the safe speed to do so) or something like that.
Miss set or broken trim connections can cause major trouble in small airplanes also. Having to hold pressure in any direction for very long makes it very difficult to make good landing etc.
Indeed–they were extremely fortunate that he was deadheading on the type of plane he was qualified to instruct in. He was the one who took over the throttles so that Haynes could focus his attention on the other stuff.
Yes, except for fly by wire aircraft (B777,B787, and Airbus aircraft AFAIK), it takes considerable effort to move the elevator significantly away from the trimmed position. This is done purposefully, often artificially, to prevent the pilots from being able to break the aircraft by accidentally pulling too hard on the column. They are quite easy and light in the controls around the trimmed position though.
Jesus. I just read that. Those guys were just goddamned amazing. And to think they were almost left for dead in a crushed cockpit because rescuers assumed no one could have survived that.
Slightly off topic, but flying a fighter is a very physical activity. Manipulating the controls isn’t hard, but the g-forces involved strain the entire body.
They have tried to repeat the Sioux City incident in simulators. To the best of my knowledge nobody has yet managed to get the plane down without killing everybody on board in the process.
IIUC, airstream characteristics change when a plane begins to stall, causing elevators to vibrate and, when pilot controls the elevators mechanically, that will cause the control stick to vibrate. On modern airplanes, the control stick is made to shake artificially when, in an old airplane it would have been shaking due to the mechanics.
Are there other examples of such artifical reversions done deliberately?
You learn something new every day; I wasn’t aware that there were systems to artificially give a fly-by-wire yoke tactile feedback similar to mechanically-linked planes. Very interesting, and it makes sense. In a crisis, humans typically get tunnel vision, so that would provide instinctive feedback to the pilot, rather than a light or audible alarm (which, believe it or not, are often captured on CVRs but never acknowledged by the crew before a plane augers in.)
Going back to the Air France flight, because of the unreliable airspeed due to pitot icing, the computer took the aircraft from “normal” law to “alternate” law, but as I understand it, this was not indicated to the crew in any way other than a small text message on one of the multi-display screens. In alternate law, the plane can be flown outside of its envelope, which is different from normal law, when the software will keep it inside.
Apparently, due to poor CRM, ‘tunnel vision,’ a lack of understanding of the software’s status, and perhaps not trusting the instruments, the pilot stalled that aircraft and then fell all the way to the ocean while holding the yoke all the way back, not realizing he was stalled.
Ferret Herder, make sure to watch the news crew footage of 232 landing in Sioux City. Al Haynes and crew saved lots of lives that day. I think it would be interesting to see Sully and Haynes have a 2-hour discussion someday. I’d pay to watch it.
Usually it’s the other way around - too easy to over-control an airplane. Which reminds me of this story…
One jet trainer I’ve flown, the L-39 Albatross, has a bunjee system to help alleviate control pressures above a certain g-force level (around 5 or 6 if I remember correctly). So once you reach that point the aircraft basically helps you pull.
On my second flight I did a loop. Properly executed, I should have pulled with about 3-4 g. On the back end I pulled too hard, then the bungee assist kicked in, resulting in a rapid 6-7 g-force. Although I had experienced that before, I was unprepared for it this time and briefly blacked out. My hand dropped off the stick, causing the plane to unload. I woke up to the sight of the plane pointing straight down at the desert and the instructor in the back seat yelling at me to get the nose back up. He then realized I had gone into GLOC (g-force induced loss of conciousness) and recovered the plane.
Nobody should have to wake up from a nice nap to find their aircraft diving for the deck. Very disconcerting!
It’s not a case of old vs new aeroplanes or fly by wire vs non fly by wire. It’s decided on a case by case basis and essentially comes down to how much pre-stall buffet can be felt through the airframe and control column. Ultimately large aircraft tend not to have any pronounced pre-stall buffet, even those with mechanical controls, and so they have a stick shaker to warn of an impending stall. If the stalling characteristics themselves aren’t benign then there there will also be a stick pusher that pushes the column forwards to reduce the aircraft pitch and prevent the stall from occurring. T-tails and swept wing designs will typically need a stick pusher.
As an example of how this is dependent on each individual design, the Dash 8 100 and 200 turboprops with fully mechanical controls except the hydraulic rudder have a stick shaker but no pusher. The Dash 8 300, whose only significant difference from the smaller models is a stretched fuselage, has a stick pusher as well. The Dash 8 400, which has more significant design changes from the other three, also has a pusher.
Other artificial feel devices include g weights and Q-feel. G weights help prevent inadvertently over stressing the aircraft by increasing the force required to move the control column when the g loading of the aircraft is already high. Q-feel helps prevent over stressing by increasing the control forces required as the speed increases. These types of devices may be required even on purely mechanical aircraft because some control designs use methods that make the control surfaces incredibly powerful.
An example is the use of servo tabs which are small tabs attached to the primary control surface, e.g, the elevators. The control column only moves the servo tab while the elevator itself just floats to an aerodynamic neutral position. By moving the servo tab, the elevator is made to move up or down as required. The large elevator surface has enough power to control the aircraft but the pilot only needs to move the relatively small servo tab.
