maybe Toyota wasn't totally to blame?

[Joe Williams]

There were good reasons, I'm sure, for designing aircraft with fly-by-wire controls. As a pilot, however, I'm not terribly comfortable with flight controls which don't have some element of backup in case the FBW system fails. For years I resisted flying helicopters whose flight control systems couldn't be muscled by hand if the hydraulics failed. I finally gave in (to get that second engine) and never had a problem, but I could never shake that nightmare of control lockup and nothing to do but bend the cyclic out of shape while heading uncontrollably for the ground.

The F-16 has three separate control systems, but having a manual system would do them no good. The airplane is far too unstable to control without help from the computer. The pilot's only option if he loses all computer assistance is to punch out. As you noted, in aircraft with hydraulic control systems, once the hydraulics are out, the pilot is riding a lawn dart. In fact, the A10 is the only modern fighter I know of with a manual (or physical) back up control system.

The much less sophisticated Skyhawks, Tigers, Cherokees, etc., that I've flown have only a manual control system. Cables and pulleys, or pushrods in the case of one of them. I'm wondering if folks who don't trust the drive by wire systems think the planes I know how to fly have a more trustworthy control system?

FWIW, the scenario of a control failure is the one thing that truly scares me about flying. Take off with a control lock in place, and it will be a short flight!!! You'd be amazed how many times I check "free and correct" before I even get to my run up spot LOL.

 

[ATOMonkey]

There were good reasons, I'm sure, for designing aircraft with fly-by-wire controls. As a pilot, however, I'm not terribly comfortable with flight controls which don't have some element of backup in case the FBW system fails. For years I resisted flying helicopters whose flight control systems couldn't be muscled by hand if the hydraulics failed. I finally gave in (to get that second engine) and never had a problem, but I could never shake that nightmare of control lockup and nothing to do but bend the cyclic out of shape while heading uncontrollably for the ground.

The FADEC equiped engines we manufacture are quadruple redundant. There are two computers, and 2 sets of sensors, and they all talk to each other.

I'm sure the airframers do the same thing.

 

[Joe Williams]

snip

If that's the case, aim for something soft.

That's the tack my Mom took when she had the brakes fail on her car. Drove the side of her car into a concrete barrier and let the friction stop her. A little tough on the car, but better than a panicked ride in an out of control car until she ran into someone else!!!!

 

[ATOMonkey]

How do you autorotate a bird that has no direct connection to the cyclic?

 

[XMil]

A Diesel engine is a totally different animal as well. There is no throttle on a Diesel engine.



They are. They also cost millions of dollars and get more maintenance in a single month than a car likely gets in its entire lifetime.

They also have redundant systems for things like this, which would be hard to justify, economically, on a car.

There most assuredly is a throttle on a diesel engine.

I believe you are incorrect in your description of the diesel engine. Once ignition is achieved, the combustion cycle continues as long as fuel is introduced into the cylinders. A gasoline engine needs electricity to induce combustion in the cylinders and removing the spark, fuel, or oxygen from the system will cause it to shut down. With the diesel, you have to either shut off the fuel or shut off the O2. Our military diesels had what was essentially a "throttle cut-off" to shut them down.

You are correct.

 

[ATOMonkey]

There most assuredly is a throttle on a diesel engine.

On some more modern engines we experimented with a throttle valve in order to force more EGR through the engine, but traditionally and even on most modern engines, there is no throttle valve.

If you're talking about an accelerator connected to either a PPS or a fuel pump valve, then I guess you can call that a throttle if you want.

 

[ocsdor]

I sure hope they never use these types of systems for airplanes. Can you imagine how ineffective and dangerous airplanes like the F-16 would be if they used fly by wire controls?

Joke from the early 80's:

How can you get your very own F-16? Buy some land in Utah.

{Utah is home to Hill AFB}

A movie was made about F-16 fly-by-wire systems and the dangers imposed by wire chafing.

Afterburn Afterburn (1992) (TV)

Based on a true story, one woman takes on the U.S. military and General Dynamics; maker of the F-16, thought to be the very best tactical fighter in the world. Air Force Captain Theodore T. Harduvel was one of the best F-16 pilots the U.S. had to offer. After much digging, Janet Harduvel discovers a joint military and General Dynamic cover-up. She proves to be unwavering in her search for the truth to clear his name.

 

[downzero]

Yes, that's all mostly true, but drive by wire is not an inherrently dangerous way to operate an engine. Also, pedal sensors have been around since the '80s. So, the reliability is fairly well documented.

Also, mechanical throttles have been known to stick open on carbs and throttle bodies alike if they build up with gunk or if the mechanism is over extended and binds. It happens.

It probably isn't the cause here, but tin whiskers are a pretty neat phenomenon that actually took down a telecomm satellite. It's good reading anyway.

I think most of the toyota things are user error, but I wouldn't rule out electronic error.

At any rate, shutting the engine off is still good idea, unless the computer bypasses that as well. If that's the case, aim for something soft.

It looks like we're in perfect agreement then. And yes, you're right, carbs do get gummed up and stuck open. It's a tradeoff either way. I think mechanical is safer. I might be wrong. I know that steering is still mechanical on (i think) every vehicle.

I believe you are incorrect in your description of the diesel engine. Once ignition is achieved, the combustion cycle continues as long as fuel is introduced into the cylinders. A gasoline engine needs electricity to induce combustion in the cylinders and removing the spark, fuel, or oxygen from the system will cause it to shut down. With the diesel, you have to either shut off the fuel or shut off the O2. Our military diesels had what was essentially a "throttle cut-off" to shut them down.

Yes, but under normal operating conditions, there is no "throttle." So changing to drive by wire doesn't really reduce safety either way.

There most assuredly is a throttle on a diesel engine.

Come and find the one on my truck, then.

 

[XMil]

If its the right truck, I can connect what the manufacturers test tool and let you watch the % Throttle parameter change.

We are arguing semantics though, it does not have an "intake air throttle".

 

[ATOMonkey]

It looks like we're in perfect agreement then. And yes, you're right, carbs do get gummed up and stuck open. It's a tradeoff either way. I think mechanical is safer. I might be wrong. I know that steering is still mechanical on (i think) every vehicle.

They are going towards electric steering. Ford and Toyota both use electric assist steering rather than traditional hydraulic assist steering now.

Hybrid vehicles use electric braking in conjunction with the traditional hydraulic brakes.

An all electric vehicle will pretty much be all electric everything. They may still use mechanical linkage for steering, but it will be additional cost and weight.

I was at a car show about 7 years ago where GM debued their "skateboard" platform, which was basically a flat chassis with fuel cell driven electic motors. Without the body bolted to it, it looked like a skateboard.

Anywho, the steering wheel wasn't mechanically connected to anything and could be switch from right hand steer to left hand steer, just by moving the wheel from one side of the vehicle to the other. It also had twist grips on the wheel for acceleration and braking.

Basically it was just like driving in a video game. I thought it was a hell of an idea.

 

[Blackhawk2001]

FWIW, the scenario of a control failure is the one thing that truly scares me about flying. Take off with a control lock in place, and it will be a short flight!!! You'd be amazed how many times I check "free and correct" before I even get to my run up spot LOL.

No I wouldn't!!!

 

[Blackhawk2001]

How do you autorotate a bird that has no direct connection to the cyclic?

You don't. When I went through the Blackhawk transition, we did a hydraulics-failure scenario in the simulator. IF it happens while you are in level flight, with good engine manipulation and a LOT of luck, you can make a survivable landing to a flat open area (I managed it - in the simulator). Once the doubly-redundant hydraulic system fails, however, you aren't moving the flight controls from where they were when the systems failed. We practiced hydraulics failures in Hueys and Jet Rangers (I've had an actual hydraulic failure in a Jet Ranger); you can hover these aircraft without hydraulics. Once the rotor system gets large enough (or rigid enough) that you _have_ to have hydraulics to control it, you'd better not lose them or you will officially have a bad day.

 

[Blackhawk2001]

The FADEC equiped engines we manufacture are quadruple redundant. There are two computers, and 2 sets of sensors, and they all talk to each other.

I'm sure the airframers do the same thing.

The A and L model Blackhawks have manual control linkages all the way to the swashplate and rotor blades, however, if the hydraulics aren't working, you aren't moving the controls - the mechanical forces are too great. I think the new M model Blackhawks may have FBW links in the system, but they are highly computerized anyway. Unlike an F-16, if the FWB system fails in a helicopter, you aren't ejecting, and the vibration levels are such that, at some point, the wiring is going to fail and give improper signals to the computer; then where will you be?

And then there is the problem of EMP...

 

[ATOMonkey]

A two engine craft makes me feel a little better since it's pretty rare that you'd lose both, and with them all hyd pressure.

So, the blackhawk rotor is too big to move without hyd assist? That sucks...

We had an investigation several rears ago where a GG turbine wheel let loose and took out the mating engine in a chopper over the pacific. The compressor coupling broke, and that lead to a severe OS on the GG turbine. Lost everyone on board. Probably because they couldn't auto-rotate it down. The containment rings are supposed to keep you from losing both engines at once, so it was a bad bad day for everyone involved.

 

[ATOMonkey]

The A and L model Blackhawks have manual control linkages all the way to the swashplate and rotor blades, however, if the hydraulics aren't working, you aren't moving the controls - the mechanical forces are too great. I think the new M model Blackhawks may have FBW links in the system, but they are highly computerized anyway. Unlike an F-16, if the FWB system fails in a helicopter, you aren't ejecting, and the vibration levels are such that, at some point, the wiring is going to fail and give improper signals to the computer; then where will you be?

And then there is the problem of EMP...

We have a FADEC on the Series IV model 250 and haven't encountered any chaffing issues with the wiring. They go through a lot of trouble to make sure those wire are VERY well protected. We have had sensor failures, but when that happens the other computer takes over, or the computers can actually share one sensor. It's a very robust design. When both sensors fail, it guess what the sensor is supposed to be reading, based off of other sensor readings.

There are similar vibe levels in turbo-props and we haven't seen a wire issue with them either.

If both FADEC computers drop dead for whatever reason (lightnting strike, EMP, etc) I believe the engine will continue to run, but there probably won't be any restarting it, and in the case of our AE engines, the compressor variable vanes lock in one position, so the engine doesn't run at full power.

All the fuel pumps are still gear driven, so as long as the turbines are spinning, you still get fuel in combustion cans, and as long as they stay hot, it'll continue to fly.

 

[Hotdoger]

No, because you're at the mercy of the pump either way, whether it's an electric servo that demands more fuel or a cable. If the pump malfunctions, it's not going to matter either way. Whether it's drive by wire or entirely mechanical, there's no throttle to slam closed and choke the engine of air, regardless of the method by which the pump operates.

A gasoline engine isn't the same. If you take your foot off the accelerator and the throttle slams closed, the concept of a runaway vehicle is a done deal. I'm pretty sure that whatever throttle position input is there or no matter what the injectors are doing, it's just going to smoke black, sputter, and die. With the throttle closed, there's not going to be any acceleration. This is more true than ever with fuel injected vehicles, because the throttle literally closes on most of them, relying on a bypass to achieve idle. There's just no practical way that such an engine can run away IF the mechanical cable and springs allow the throttle to slam closed.

Plenty of mechanical pump diesels still out there that when the throttle spring breaks the throttle goes full open.

 

[Blackhawk2001]

We have a FADEC on the Series IV model 250 and haven't encountered any chaffing issues with the wiring. They go through a lot of trouble to make sure those wire are VERY well protected. We have had sensor failures, but when that happens the other computer takes over, or the computers can actually share one sensor. It's a very robust design. When both sensors fail, it guess what the sensor is supposed to be reading, based off of other sensor readings.

There are similar vibe levels in turbo-props and we haven't seen a wire issue with them either.

If both FADEC computers drop dead for whatever reason (lightnting strike, EMP, etc) I believe the engine will continue to run, but there probably won't be any restarting it, and in the case of our AE engines, the compressor variable vanes lock in one position, so the engine doesn't run at full power.

All the fuel pumps are still gear driven, so as long as the turbines are spinning, you still get fuel in combustion cans, and as long as they stay hot, it'll continue to fly.

Yep, the GE engines on the Blackhawk are set to go to max if the computers fail, and the crew can live with that; they can be manually controlled through the Power Control Levers. If a computer is controlling your flight control inputs and it/they fail for any reason - bad, bad day.

When I was flying commercial helicopters in the 80s, there was a series of problems with C-30 series engines blowing their compressors and shrapneling the other engine on Sikorsky 76As. I know a few were lost in the Gulf of Mexico at that time. As long as engine turbine wheels depart the engine sideways, they'll likely miss the transmission, but if the transmission(s) fails at altitude - bad, bad day.

 

[Blackhawk2001]

Back to the drive-by-wire relevance to this thread. Aircraft crews tend to know their aircraft systems, their capabilities and their failure points, and know the recommended procedures for responding to those failures, if and when they occur. They do this because they usually can't just pull over and park the thing if something goes wrong. We have a different attitude about our cars because we believe that if something goes wrong, we can just pull over. How many of us have found that not to be the case? It may be that automobile manufacturers are going to have to emphasize some relevant emergency procedures for potential catastrophic or unusual failures in their vehicles - if the lawyers and trial lawyers will let them.

 

[ATOMonkey]

Plenty of mechanical pump diesels still out there that when the throttle spring breaks the throttle goes full open.

If you fail a compressor seal, the engine will consume the 7 or 8 gallons in the pan no matter what input you give to the silly thing.

We've blown up engines (overspeed), twisted drive shafts, and all manner of things getting runaway trucks to stop that are running on engine oil.

 

[ATOMonkey]

Yep, the GE engines on the Blackhawk are set to go to max if the computers fail, and the crew can live with that; they can be manually controlled through the Power Control Levers. If a computer is controlling your flight control inputs and it/they fail for any reason - bad, bad day.

When I was flying commercial helicopters in the 80s, there was a series of problems with C-30 series engines blowing their compressors and shrapneling the other engine on Sikorsky 76As. I know a few were lost in the Gulf of Mexico at that time. As long as engine turbine wheels depart the engine sideways, they'll likely miss the transmission, but if the transmission(s) fails at altitude - bad, bad day.

A lot of people (other than pilots) like the fly by wire, because it's much easier to maintain and trouble shoot than a cable or hydro setup.

Basically, there is no maintenance, other than making sure the servo motors are clean.

No leaks, no cable tension, it's a beautiful thing.

We have the most problems with the guys who ferry people and stuff to oil rigs in the gulf.

They run their equipment overloaded, and on the stops way past the time limit for rated power, and then wonder why they eat up turbines.

We actually had a guy autorotate a bird down WITH an underslung load after he killed the engine. That was pretty impressive.