Turning the X5 off in an Emergency

[London Lad]

Originally Posted by ABMW

snip

Fly-by-wire airplanes have been a source of contention with safety advocates and pilot associations for years. Some planes have up to 5 redundant systems that come into play when a primary system fails, then when a secondary system fails, and so on.

Guess what? There have been multiple instances of all redundant systems failing, .....snip

Can you post a link to info about just one instance where all redundant systems failed in an aircraft ?

[London Lad]

This is far more likely to be the woman hitting the accelerator instead of the gas and then panicking.

[London Lad]

Originally Posted by autoque

I was in a parking lot, seated in the back, driven by someone who's not very familiar with the vehicle and a passenger who's no better than the driver with the car. We were going at a parking-lot-cruising speed. Suddenly, a passenger pressed the engine start/stop button thinking it was an emergency blinker button... I got upset but oh well, the irony... I got something to post here... the car seems fine.

Anyway, what happened; the engine actually got turned right off and the transmission went immediately into park but the car still rolled like it was cruising in Neutral. I'm not sure if the steering was still powered or the brake was as effective, since I wasn't driving.

On a modern BMW auto box the park pawl is on a ratchet so that if park is engaged accidentally with the car moving it will not just be snapped off in the gearbox but instead only drops into place as the car comes to a halt.

I had a situation in the last X5 model where I had to emergency brake from about 70mph to avoid an accident which was taking place in front of me.

As I braked an insecure cooler box flew from the back of the car, through the gap between the front seats, and hit the auto gear selector which was smashed from drive all the way forward (breaking the interlocks) into park.

At about 60mph with the selector in park and still braking hard, I was expecting the gearbox to lock and start a skid. I was tempted to move the selector back to drive but that would have meant passing through reverse so I just kept braking to a halt on the hard shoulder. As the car came to a halt the park pawl engaged hard with a jerk.

Amazingly the only damage was the broken plastic lockout device in the gear selector!!!

[JCL]

Originally Posted by ABMW

BMWNA, Toyota, Nissan, etc., do they have redundancy systems for their drive-by-wire?

I think we all know the answer.

No, they don't. Any they didn't have redundant systems for mechanical linkages used for the past 90 years or so, when the biggest danger was friction in the linkage, or floormat interference.

However, they do have a driver. And the driver has a brake pedal. Any automobile brakes, by design, are 3-4 times as powerful as automobile engines. That isn't true on a continuous basis (brakes will overheat and fade) but you have several stopping cycles available to you before that happens.

Simple steps if the accelerator sticks:
1) Don't lean down and try to unstick it.
2) Apply the brakes
3) Steer out of traffic, ie to the side of the road
4) Then, and only then, put it in neutral
5) Turn off the vehicle

Doing (4) or (5) before (2) and (3) risks incorrect gear selection (as noted in the example above) and a further loss of power steering and brakes if you do (5) before you are safely stopped.

It all comes down to untrained drivers, going into panic mode.

Putting a safety interlock into the system to make the brakes shut down the throttle is only useful if the driver is applying the brakes. Since the brakes can overpower the accelerator anyways, it is there for product liability/lawyer issues, and not as a practical benefit in most cases.

[JCL]

Originally Posted by ABMW

Guess what? There have been multiple instances of all redundant systems failing, despite electronics that put the most advanced automobile systems to shame, and have been tested to degrees that should theoretically provide fail proof systems, but they've failed nonetheless, despite the odds, and people have perished as a result.

Planes have redundant systems because of the obvious difficulty in pulling over to the side and parking, and because they typically use automated inflight controls such as autopilot.

Let's design a redundant system for a gas pedal. What would it look like? Would it be a second gas pedal, so that you had to be telling the car to accelerate via two separate systems, simultaneously? Would it be a failsafe that allowed the car to decide that it would rather not accelerate right now, that things just don't feel right? No thanks. Would it involve the brakes being a no-go signal that caused the accelerator to go to idle? Brakes can already overpower the accelerator, so that isn't a step forward except for the lawyers.

Where is the failsafe for the drivers who are in control (or not) of these vehicles? Maybe we could have two driving positions, for two separate individuals, and the car could calculate the average of the inputs. God help us all.

[ChuckG]

I saw a mechanical linkage fail on a 60's Corvette Stingray fail once when the throttle return spring broke. It was at full throttle when it rammed into a concrete post holding up a light pole in a parking lot. Luckily he was going slow when it happened and he did not accelerate very long before hitting the post. He did hit it at about 45 MPH. He was banged up and had some facial lacerations but otherwise was OK. The Corvette was however a mess.

So the old mechanical throttle linkages were not totally trouble free either.

Chuck

[Armand]

Originally Posted by London Lad

On a modern BMW auto box the park pawl is on a ratchet so that if park is engaged accidentally with the car moving it will not just be snapped off in the gearbox but instead only drops into place as the car comes to a halt.

This feature is in deed documented in the 2010 MY manual (x5). If you pull the hand brake and hold it, the car will apply the brakes forcefully, only engaging park at 2 mph.

This is an interesting thread. I personally am not going to try any of the funky techniques such as turning off the engine or shifting gear into neutral just for the sake of experiencing it. At the first sign of trouble, I will hit the brake with both feet as hard as I can - if you like to pull the hand brake, go for it. The car will most likely slow to a manageable speed. Is it possible that it might not? Sure but I am not going to lose sleep over it. We bought one of the best cars money can buy. We have a great chance of avoiding the worst case scenario. Just watch out for the Toyotas and Lexuses out there!

An interesting point about the diesel engines... Since the maximum torque occurs at low rev, you may have a better chance of overcoming uncontrolled acceleration.

[ard]

Originally Posted by ABMW

Seems explainable. Woman trying to shift into neutral and goes into drive, etc.

It's the audi thing all over again.

The article I quoted says the stuck accelerator caused both the forward and backwards.... probably sloppy writing.

Lots of times people panic and stomp on the accelerator THINKING they are on the brake. At 14 years of age I was a passenger in a car when this happened- My dad was towing me in a dune buggy, grandfather driving the dune buggy, me in the passenger seat, no belts... as we descended a slight hill and began to gain on the wagon, grandfather was stomping the accelerator pedal!!! .. to no effect- as we gained on my dads station wagon my grandfather decided to pass the wagon. Unfortunately the 30 foot chain halted that process when he got into my father's vision out the drivers door. To this day the last thing I recall (before being catapulted into the windshield and then to the hospital) was my father's horror looking at the dune buggy next to him. I digress..

But my grandfather swore the brakes didn't work.... I was driving by then and knew better.

Back to the argument at hand- how does a mfg separate issues like this, from floor mats to stuck assemblies to software bugs????

A

[ChuckG]

Originally Posted by ard

Back to the argument at hand- how does a mfg separate issues like this, from floor mats to stuck assemblies to software bugs????

A

In one of the recent Toyota fatal incidents the floor mats had been put in the trunk because of the previous recall. I think they know that that one wasn't due to the floor mats.

Chuck

[ard]

Originally Posted by ChuckG

In one of the recent Toyota fatal incidents the floor mats had been put in the trunk because of the previous recall. I think they know that that one wasn't due to the floor mats.

Chuck

Right. We got that one figured out.

My comment was rhetorical in a sense that failure analysis of field failures/complaints extraordinarily difficult.