[MR2] MR2 news from Top Gear

[William Brandt]

Wow - lots of interesting discussions going on. First aircraft have redundant systems - Boeing is the best with most planes having 3 hydraulic systems. Plus they must be tested ad nauseum for the FAA before certification. 

I remember 20 years ago, working for Cessna in Wichita, going to the company cafeteria and going by the test hanger - they had a Citation 3 wing (a medium size exec jet) on some jigs with hydraulic presses constantly flexing the wing back and forth to simulate 1000s of hours of flight time. 

Even then some of this fly-by-wire stuff is a bit too much - Airbus seems to have a problem between their software and the rudder giving too much angle in certain situations - causing the tail to fall off ;-) Mercedes has a cruise control system that automatically slows the car when it detects too small a space up front. And the computer will automatically tension seat belts when it detects the driver "slamming" on the brakes. 

And Lexus has their auto parking system. 

I view all this is fine until it goes bad and then big $$$ to diagnose and fix. Then it is just more crap going out. Like the little motors inside the LS430 vents that move the vents back and forth to move the air. Fine until the motors go bad and you have to tear the dash up. 

When you have a car that is 100 times as complex electronically do you think you will get the same trouble-free longetivity? 

Mercedes electronic brakes - well, they did have a brake system that was computer controlled - with hydraulics - even changing the pads and pushing the pistons back was a special procedure - offered on the latest SL and the last E Class - but I have heard that they dropped it. They had a problem first with the initial software. Have a friend with an E Class who loves it but as to why they have dropped it I cannot say. At least they have no plans on offering it in more models. That is what I heard. 

Bill

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MR2 news from Top Gear
To: bob-schultz at comcast.net
Cc: mr2 at mr2.com
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Airplanes though, to be certified by the FAA, must have redundant systems
built in.  I'm not a flight controls guy, and don't know if their backup
system is mechanical or electronic; but it has to be there, and isolated
from the primary system.  Besides that, airplanes cost $100,000,000.

Ah, here we go.....

loss of all flight control computers could immediately render the aircraft
uncontrollable. For this reason, most fly-by-wire systems incorporate either
redundant computers (triplex, quadruplex etc), some kind of mechanical or
hydraulic backup or a combination of both. A "mixed" control system such as
the latter is not desirable and modern FBW aircraft normally avoid it by
having more independent FBW channels, thereby reducing the possibility of
overall failure to minuscule levels that are acceptable to the independent
regulatory and safety authority responsible for aircraft design, testing and
certification before operational service.

On Sun, Jan 24, 2010 at 12:49 PM, <bob-schultz at comcast.net> wrote:

>  I hear what you say and honestly I kind of agree with you.
> My LS430 has radar cruise but when the Yaw Sensor gets out of sync
> (something like a $600 part) the cruise dies so the drive back from Yosemite
> was a problem.  I think resetting the Yaw Sensor fixed the problem but I
> digress.
>
> Anyway, I have a friend who is a pilot and he told me that airplanes have
> been fly by wire for years and although they probably have had some teething
> problems way back then, they don't fall out of he sky that often.
>
> Bob
>