electronic throttle

Icing on a JET?????????
Don't think so.

 

Absolutely. Determined to be cause of BA 777 landing short at Heathrow.

 

Clare - I followed the rest of your explanation, but, as a circuit
designer, I had trouble following that part. That would have to be two
potentiometers ganged on one shaft? You're not saying that one
potentiometer provides two signals, right? I'm picturing a TPS pot.
with ground on one end, Vref on the other, and the wiper signal. I
don't see getting two signals from the one pot, inverse or otherwise.
What did I miss?

 

Actually, after some thought, I can see how it might be done with a
single pot: Pot wiper gets tied to ground, and you run constant current
into each end terminal. The voltages read at the two end terminals will
be inverse of each other (as wiper is moved in one direction, voltage of
one end terminal goes from 0 to R x I, voltage of the other end goes in
the opposite direction).

Not saying that the designers would have realized that it could be done
like that, but that's the only way I could think of using a single pot.

 

Cause was assessed to ice in the fuel, not a computer/software glitch.

 

This does seem to be the published cause but I have some doubts. I
could have sworn that I did come across a s/w issue as well but...

There are a number of reasons why I do so but that isn't appropriate here.

 

And there are people who sell tin foil hats for people like you.

 

OK - I looked it up. Technically this was fuel jelling - common with
diesel fuel in arctic conditions. In the case of the Rolls turbines,
it was a design fault in the fuel pre-heater unit which resulted in a
mandatory replacement with a redesigned heat exchanger.

Different than the carb icing on a prop plane.

 

Just raise the ground so the 5 volt reference is , say, 6 volts
above ground, and the "ground" is 1 volt above ground and measure the
voltage between the wiper and ground and between the wiper and
"ref" At idle the wiper to "ground" will be one volt, and between the
wiper and "ref" will be 5 volts.
At half throttle you will have roughly 3 volts from either wiper to
ref, or wiper to ground, and at WOT you will have 0 volts wiper to
ref, and 6 volts wiper to ground.

Can also be done without raising the "ground", but then a zero volt is
possible at idle as a legitimate signal.
With a raised ground, a open anywhere in the ref circuit would give
you a 0 volt reading which is not a legitimate signal, so would
trigger an error without having to compare any other voltages..
Without the raised ground, idle position voltage is undiscernable from
a fault voltage untill the pedal is depressed, so a closed throttle
sensor is required to verify that the throttle is, in fact, closed.

So there you have it.
Simple, isn't it?? (once you get your head around it)

 

That works too.

 

It was ice in the fuel blocking the pre-heater, not fuel jelling. Get
it straight.

 

Nothing I love more than seeing someone with egg on their face...

Ford Escape was a precursor... and now, anything with active park assist...
Please don't make me dig through the option lists... Taurus would be another
and likely MKZ, Edge... maybe Flex...

Electric power steering is the future coming to life... from an NVH
standpoint as well as other considerations...

FWIW, I can't comment for other marques... Vehicles are far too complex
these days for anyone to call himself an "all make" technician.

BTW... I'm sorry I didn't make you scroll to the bottom of a whole bunch of
drivel you already read just to read my reply...

Everyone wants to "bottom post" but they all want to butt in front of me in
line at the bank...

 

Actually, in the modern automobile, the gas pedal tells the PCM that you
want to go faster...

A lot of you folks are gong to be disappointed in the near future...

The headlight switch tells the BCM that you want to turn on some lights...
the turn signal switch tells the BCM that you wnat to turn on some flashing
lights...

This is gonna be cool...

 

that's it.

 

All three had the "air bypass" valve too.

I do not know what you mean with "ISC system".

BTW, I have known some discreet electronic components that have failed due
to being used too near the maximun demand for too long, would you not
consider that to be 'wearing out' ??

Best wishes

David



--- news://freenews.netfront.net/ - complaints: ---

 

"I looked it up".

Could one or both of you provide a URL for us to follow?

Gelling -- not "jelling"... -- or ice formation... would like to read
up, as I was under the impression from the brief reports I heard on the
general news that it was diesel gelling, but that might just have been my
dodgy memory...

DAS

To reply directly replace 'nospam' with 'schmetterling'
--

 

But my way violates the unacceptable ground on an analog input that you
pointed out. Your method is better.

BUT - you wouldn't even have to raise the ref and its ground. Kind of
combine our two methods: Tie the wiper to the ref. voltage (gets rid of
the ground issue), and put a constant current source (sinking) on both
ends. Scale your constant current and size your pot. such that when the
wiper is pegged to one end (and reading 5 volts), the voltage on the
other end is, say, 1 volt. That could be done with a nominal 8 mA
current source and 500 ohm pot, as an example. The two ends would range
between 1 and 5 volts (nominal), and be inverse of each other. One
check the ECM could do is verify that the two voltages at any moment in
time add up to 6 volts.

 

http://www.independent.co.uk/news/uk/home-news/ice-probable-cause-of-boeing-777-crash-1893650.html

 

Wasn't the same cause suspected in the recent Airbus plane crash in the
Atlantic, just off the South American coast?

 

No.