How to disable VSC?

Jayman, nice writeup on aircraft control as it pertains to airliners. I was thinking more in terms of high performance aircraft, where the lack of inherent stability prevents manual control regardless of the skill of the pilot. I know you know this, but for the sake of completeness, on these high performance aircraft the designers have sacrificed stability to gain performance, which is fine as long as the flight control system is fast enough to compensate. These planes also have multiple control modes, but they go more like this: 1) Complete fly-by-wire computer augmented control; 2) Backup fly-by-wire with limited computer augemented control; and 3) Oh shit, I'm punching out.

Most of the old WWI fighter aircraft lacked dynamic stability. You had to fly them constantly or they would roll over, dive, pitch up, or some leathal combination of the above. I understand they are exhausting to fly. At least in the case of the WWI aircraft they were slow enough to allow a skilled pilot to compensate for the lack of stabilty.

Tom

 

Um .... whoops

:redface:

Guess I missed that part. Right you are, a completely different set of design rules apply to military fly-by-wire aircraft

For example, full time three axis corrective control is *mandatory* or you will probably lose control. A similar Direct Law does exist, but realistically the pilot is yanking the Panic Handle once he enters that mode

The various protective measures applied to civillian airliners are to improve flying safety. Many of the aural warning systems trace back to tragedies, and an attempt to prevent them.

For example: the radar altimeter to warn the flight crew if the angle of approach, speed, flap and gear configuration, are all wrong for landing. The wailer goes off, and they typically hear "too low terrain pull up pull up." Or if they happen to hit a microburst, they'll hear "sink rate sink rate"

Radar altimeters are really limited though. They generally are not powerful enough to work much above 1,500-2,000 AGL. Their coverage angle is typically under 10 degrees. So if you happen to fly into mountain terrain, by the time you receive a pull up aural command, you're seconds from CFIT

Modern EGPWS make use of GPS, very detailed geospatial data, the radar altimeter, to offer a great safety edge. When you consider how often pilots get "lost" flying into unfamiliar airports, especially at night, this is very important. You receive the "caution terrain" aural announcement long before you're SOL

Older jet aircraft - especially T-tal configuration - made use of stick shakers and stick pushers to minimise stall risk. The takeoff configuration was compared to the known stall speed of the type (Clean, flaps, flaps + slats, gear up, gear down, etc).

Approaching the stall region, the stick shaker will make the control yoke vibrate, sometimes violently, with a wailer going off. If the aircraft ventured into actual stall conditions, the stick pusher was a hydraulic ram that would force the column forward

A serious limitation with stick pushers was that it was difficult to keep the aircraft at the *edge* of stall. Say you suddenly become aware that you're about to perform a CFIT, say in mountain terrain. You hit the TOGA button, yank the column all the way back, and the shaker goes off

At a certain point, the pusher rams the column forward again. There was usually a 5-15 sec delay before a relief valve dumped pressure, so you could yank the column back. A constant oscillation of yank, push, yank, push, etc. Shaker goes off again, pusher rams column forward again, and kaboom you experience CFIT

The Airbus and Boeing Alpha Floor protection is much smarter. It will keep the aircraft at the very edge of stall, but still let you apply the maximum possible climb rate. More than likely, if you're already deeply into a CFIT situation, you're still going to impact terrain, but at least you have a slightly better chance

Even engine control is light years beyond the strictly mechanical control. Back in the day, a Flight Engineer was needed just to keep the EPR correct on the engines. With FADEC, you let the computer worry about that

Say you lose an engine on takeoff, at rotation. With modern FAC and FADEC, the rudder trim automatically compensates, but you still have to give the pedal a healthy push. There are design rules for 2 minute, 5 minute, 15 minute, and constant full power.

FADEC will allow the maximum possible power from the remaining engine(s) with no danger of cooking the remaining engine(s). As the various power rules timeout, say at 2 minutes, the engine automatically retards to the next lower available power rating. This is great, as crashes in the past were caused by incorrect power settings, sometimes causing a stall, sometimes causing the remaining engine to grenade

Another important safety advancement was simple Human Factors Engineering. Say you have an older two engine airliner, maybe a 737 or a DC-9. You happen to lose an engine on takeoff, say at rotation. The aircraft is perfectly flyable under such a situation, unless you get confused and panic

Say the starboard engine fails. The pilot in command is busy flying the airplane. You get the engine fire wailer. In a mad rush, still busy with trying to establish a positive rate of climb, somebody pops the fire bottle for the port engine, the *wrong* engine.

The good engine flames out, you stall, and crash. This has happened a few times, in the past. The relatively simple fix? If an engine fire is detected, a red light illuminates on the "correct" fire handle.

The newest Boeings, and the fly by wire Airbus, go one step further. When you pull the correct fire handle to arm the fire bottles, the engine is automatically isolated. That is, the electrical, hydraulic, fuel, and air bleed are automatically isolated from the aircraft, so in a mad rush you won't dump the electrical on the wrong engine

Mostly it's Human Factors Engineering, with some good common-sense engineering applied (Never assume nothing will fail, plan for graceful failure). I really enjoyed my contracts with Honeywell, the only thing I didn't like was the most important safety advancements came about due to loss of life

As an extreme example, the F-117 and B2 are completely uncontrollable without full time Flight Augmentation

Note: don't assume I actually have flown a fly-by-wire airliner, at least outside of a simulator. Again, it was a very rewarding point in my career when I could do work like that.

I only wish the flying public demanded better safety systems. The government hates angry petition letters from the general public. I really wish the flying public would demand the FAA replace the ancient air traffic control system with something not older than I am

Seriously, folks, a lot of that wonderful radar used by ATC was made during the peak of the Cold War. A lot of it runs on vacuum tubes. That's fine for a science fiction set, not for handling the traffic volume we now have to deal with

 

It's amazing how much old equipment is in daily use. The public assumes we get nothing but the newest and the best, but that's not the case.

I remember at least one crash where the flight crew thought the stick shaker was mach buffet and pulled back, instead of pushing forward. If I recall correctly, there was an unfortunate pitot static problem which screwed up the airspeed display. The displayed airspeed was climbing while the actual airspeed declined. The plane was stalling while the airspeed showed nearly mach 1, creating an unfortunate opportunity for the stick shaker to feel like mach buffet. Sometimes the simplest things get you.

I remember another crash in Florida where an airliner was having trouble with its nose gear. They couldn't get a lock light, and were screwing around trying to see if it was a failed indicator or really a bad lock. During all of the circling, someone leaned on the stick which disabled the autopilot. The aircraft was fairly well trimmed, and started into a very slow descent. It crashed into the Everglades while they were still fooling around with the gear.

Tom

 

Well, Qb, I pretty much agree with your statement:

"Most of us are willing to put up with a few quirks since we understand that the Prius is a new and revolutionary car. As enthusiasts we learn to adapt, but you can't expect ordinary drivers to do so."

The thing is that quirks are quirks. They are inconvenient. These "quirks" I am talking about aren't merely inconvenient, they can cost lives. And even my enthusiasm and racing experience wouldn't have saved me. It was dumb luck that a) the other driver was paying attention and slammed his/her brakes (at Moanalua Road near Haukapila Road; see below) and b) there was no oncoming car in the other instance (at Moanalua Road and Moanalua Loop; see below).

LOL, jay! Damn, those casings must scratch the hell out of the roof! I hope they have some sort of protective layer down! And all the casings that roll into the car... when you get back in, you could clip and crack yer skull open. They really oughtta have some 20,000 casing catcher or something so you can fire away for... like... 10 seconds without hurting your paint or littering the car's floor with virtual big pin bearings. Lol.

Nownow, I don't believe it was ABS that did it to me, but rather the VSC when I "whipped" a high banked hard right that transitioned to hard left with a camber shift.



You can Google Earth this spot if you like. Search "Moanalua Road & Moanalua Loop, Honolulu." This is the turn I keep talking about where the Prius LAUNCHED me into the oncoming lane as I transitioned to the left turn. Granted, I was having a little fun with this turn, as I have MANY times for over 20 years in every car I've ever owned, and some that weren't mine. I've NEVER come out there or even crossed the center line. The violence with which the Prius overreacted immediately wiped the smile off my face and made me realize that this system WILL kill someone. And hopefully it's only one person before Toyota acts.

This Google Earth image is pretty good, but obviously, to get the true feel, you just have to drive this turn.

Coincidentally, since I'm including Google Earth images now, my other gripe about the driveway is super close to this turn.



Now, this image ain't so great but it shows the parking lot I was pulling out of (ahead in image) and onto the road going downhill (to the left in image but to the right from driving POV). The parking lot exit road is almost or completely horizontal from left to right but goes downhill to Moanalua Road. So, you've got a downhill to uphill transition at the exit/road point and then are turning left to go downhill on Moanalua Road. A tricky transition that will rock all cars side to side. But it will cause the Prius to kill power for AT LEAST a second while creeping/coasting onto Moanalua Road; a major feeder road to the second largest shopping mall in Hawaii.

You can Google Earth it by searching "Haukapila Road & Moanalua Road, Honolulu," zooming in a bit, and then using the Google Earth ruler to measure 105 meters northwest of the intersection of Haukapila Road and Moanalua Road, finding the driveway next to the L-shaped building with a good-sized parking lot. That's my intersection...

I really hope someone from Toyota reads this...

 

Was that the flight where somebody had TAPED OFF the pitot ports? Something to do with a paint job? Gee-zus cah-rist, doesn't anybody have responsibility anymore?? Like, clean up after your work is done??

It's easy to put yourself in that situation, and say "could, would have, should have." The fact is, when you're in that situation, with weird things happening, the Master Caution wailing at you, it's pretty easy to make a mistake

That's why I now believe in Human Factors engineering a *lot* more than I used to. Something that now seems intuitive, like have a red light turn on for the correct fire handle, was learned due to lives lost.

The incident with the taped/plugged pitot port is scary. To be sure, a 767 pitot port is a long way off the ground, you'd need a manlift to inspect it. The obvious stuff, like flappy red "REMOVE BEFORE FLIGHT" tapes, are courtesy of Tomestone Engineering

Have you ever forgotten to remove a gust lock on a small plane? That still happens too, folks sometimes die as a result

The Air Transat A330 that ran out of fuel over the Atlantic, Human Factors engineering almost caught up to us again. A replacement engine had been fitted a couple of days earlier. The parts kit was wrong, the fuel pipe was too close to a bracket

During normal flight ops, the vibration chaffed a hole in the fuel pipe, so all that Jet-A gushed into the nacelle around the turbofan. Their first indication of trouble?

An EICAS caution, about stone cold oil temp and high oil pressure

That didn't make any sense, so the flight crew naturally thought it was a "computer glitch." In hindsight, all that ice cold jet fuel gushing all over the engine would make the oil temp go cold, which would result in high oil pressure. Jet fuel is prety safe, if that had been gasoline KABOOM

They received another EICAS caution, about fuel imbalance. So what is the normal thing to do? Manually open a crossfeed valve and switch on an extra boost pump. All this time, the indicated fuel quantity levels were rapidly falling

Again, this made no sense to the flight crew. It just *had* to be a computer glitch, right? Until one of the engines flamed out due to fuel exhaustion, then they realized they were in deep s***. When the other engine flamed out a few minutes later, they realized they were in *very* deep s***

The APU wouldn't start as there wasn't a drop of fuel left to run it. So no backup power, no bleed air to pressurize the cabin. The Ram Air Turbine deployed, which provides very limited electrical and hydraulic power. I wonder how folks in the passenger cabin felt as the cabin altitude rose to flight altitude? Probably dizziness and nosebleeds?

That flight ended incredibly well: they landed at a military airfield in the Azores, causing damage to the undercarriage. Once the original problem was fixed, the plane refueled, the tires and wheels all replaced, the plane was flown out with no issues

As a result of that incident, Airbus had to change the EICAS to now specifically warn about fuel leaks, before attempting to crossfeed. However, one *should* suspect a fuel leak if there is a massive wing-to-wing imbalance. Right?

If the crew have ignored the fuel imbalance, the engine with the improperly installed fuel line would have run out of fuel sooner, the wing tanks would have gone dry. That engine would have flamed out, and they would have still had the other engine, fairly healthy fuel, and more time to deal with the problem

Under ETOPS, they would have diverted to their nearest airport. The handling would have been flaky due to having the weight imbalance, but they probably would have landed normally, seen all the fuel stains on the dead engine, and said "holy s***." Instead of screaming "holy s***!" when the last engine flamed out

Again, Human Factors caught up to us.

Up until fairly recently, autoflight systems allowed *partial* disengagement without aural warnings. Example, you push slightly forward on the yoke, the autoflight system senses this and disengages pitch control: roll and yaw is still in, along with throttle control, but you are now manually controlling pitch. What could possibly go wrong?

One of the more famous examples was that Aeroflot A310 that crashed in Siberia. The pilot let his 15 year old son at the controls - don't ask, it's too weird to even imagine. As a result, the autoflight *partially* disengaged.

The partial disengagement meant that the aircraft veered off course, which the autoflight tried to "correct" with only two axis of movement. This is completely off the envelope, the aircraft climbed until it stalled, then entered a non-recoverable dive

In hindsight, a Master Caution wailer once the kid touched the controls, would have been appropriate. Yes, that crash resulted in major software changes to current and future autoflight system protection

As a prank, I was in a 320 simulator when somebody programmed multiple failures: engine out on rotation, yaw damper fail, flap disagree, yes I crashed

 

I don't think BlackWater worries about that too much

As far as TC and VDC behavior, one thing I noticed when I testdrove the 2008 Prius: it's light years better than my 2004.

Yes, official Toyota folks do monitor this website. They are well aware of quirks, and outright problems. The TC is one area they obviously improved on

 

Jayman, I believe that crash was the one with the taped off static port.

As for control locks, most of the planes I've flown had a big red flag that stuck out over the starter just to keep you honest. I appreciate that sort of thing, as it only takes one little oversight to get you killed. I did come close to killing myself one time when I forgot to take carburetor heat off after a touch and go. It almost turned into a touch and crash into the building at the end of the runway. I wasn't getting much power out of the engine, and the rate of climb was barely adequate to get me over the roof of the building. After my orifices unpuckered, I looked down and there was the carb heat lever sitting there pulled out, plain as day. All of my training taught me to push it in with the throttle, but somehow I missed it. I didn't make that mistake again.

Multiple failures in a simulator. Oh yea, I've been there. It usually came right after "Chaff, Flares" and went something like "Warning: Engine fire left, engine fire right, hydraulic failure..."

Tom

 

Sucked to be that crew, that day. I can only hope they didn't suffer. Not sure what sort of aural advisory would have helped in that situation. There are already "command disagree" aural warnings about speed limits not reached, or exceeded

I find it interesting the stall warning, coupled into different data paths than simple static, functioned correctly. However, the aural "stall stall" did not. Just the shaker, which as you correctly stated, was confused with overspeed buffet

"There but for the grace of god go I"

Yes, in hindsight, a pretty obvious oversight. In that exact moment, however, you're sitting there saying "what the frack is going on here?"

Most modern airliners can automatically select continuous ignition, and then switch them out under unusual power demands. For example, say you try to land and get a nasty gust that pushes off center, your flare is buggered, the best thing to do is a goaround

So you either ram the throttles forward, automatically putting the engines into TOGA thrust, or hit the TOGA button, to do the same thing. The systems are smart enough to reconfigure packs and let you concentrate on just flying. I guess it would be nice for a single engine airplane to have the same features

General Aviation is expensive enough. If we try to build some airliner safety features into a single engine airplane, eg Piper Meridian, it's easy to exceed two million dollars. A wonderful plane, if I ever got back into flying, I'd seriously consider one. But +$2 mil?

Awww, that ain't fair

 

Ok, we're WAY off topic now, but you got my curiosity

The crash happened Feb 6, 1996. The aircraft was a B757 operated by a Turkish charter company, for Alas Nacionales of the Dominican Republic. Apparently, only the Captain static port was taped off, the remaining pitot ports were open and normal

The first indication of trouble was at the V1 callout, the Captain reported his airspeed was barber-poled and inop. The F/O's airspeed indictor, the standby, and the inertial guidance airspeed calculator all agreed with each other

For some reason, the Captain became fixated on his airspeed indicator. He thought the *other* airspeed indicators had failed, especially when his suddenly came to life to indicate a completely improbable airspeed

The stick shaker received input data from other systems, which were functioning correctly. The autoflight received information from the Captain pitot, and was barber-poled and inop.

Note: the 757 POH has clear instructions on what to do if an airspeed disagree or airspeed failure is noted. Nobody on the flight deck bothered to follow the flowchart.

What became apparent was that the Captain became entirely fixated on what could be causing the airspeed disagreement. Then everybody became fixated on why the autoflight was not working, or why they were receiving contradictory (Overspeed and stall) warnings

Time from V1 to crash? Five minutes

A lot can happen in five minutes. could have would have should have, you know. But like the Air Transat unintentional glider to the Azores, a failure to follow the POH this time resulted in the loss of aircraft and crew

One common theme I see popping up, is the flight crew apparent disbelief of what they are seeing on the screen. Instead of working around the problem, they become fixated on what caused the problem.

Who cares what caused the problem? That's the job of the line and maintenance crew to figure out. Just fly the damn thing

There is training that is supposed to be in place to prevent this sort of fixation. I think at a basic level, if one considers Human Factors, the same disbelief and suspicion of crappy home computers, is extended to millions of dollars worth of RTOS that is tested far beyond the average PC

So whether dealing with opening crossfeeds to dump all your fuel overboard from a broken fuel line, staring at the one indicator that is inop, or inadvertantly selecting "f/s" instead of "FPA" and dropping at 3,300 fps, there is something very badly broken when it comes to flight crew training

Back to original topic: no, do not disable the TC or VSC. Very bad

 

I have seen this happen. The zombie gaze, staring at the problem in disbelief. I see it with engineers too, when they can't believe that their code doesn't work: "But it should work..." Well, somethings not working, so at least try to isolate the problem. Do something; don't just stare at it in disbelief.

I remember one time being in an unusual attitude (aircraft, not my head) with the nose very high. I was on instruments, and the nose was so high that the attitude gyro card had dropped to its lower limit. The card was so low in the display that the white background behind the card was revealed at the top of the display. I sat there and looked at it in disbelief. It felt like a long time, but it wasn't, because my airspeed was dropping like a stone. The white background above the black card made me think I was inverted. For a brief moment I considered rolling the aircraft to bring it around, but the dropping airspeed didn't make sense. With that display, if I was inverted my nose would be low and the airspeed should increase, not decrease. I had to be nose high. I dropped the nose and the airspeed climbed. When the attitude card came off the stop, I could see what happened and it finally made sense. The whole episode couldn't have lasted more than a few seconds, but it seemed like an eternity.

Thanks for the blow by blow on that crash. What a Mongolian goat f***. That one falls into the category of the old saying that you can't idiot proof things because idiots are so clever.

Tom