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Author: CoopCoop Date: May 1, 2008 02:40
INteresting and unusual observation at Adelaide airport a couple weeks
ago:
I fly Rex every week at present, so I am often in the Adelaide
terminal watching other departures while awaiting my flight.
Observed an S340 commence startup, but something was wrong- the heat
haze was emerging from the rear of the turbine, but the prop wasn't
moving.
Most of you will know that when the S340's turbines start up, the prop
begins rotating slowly at first, and then steadily accellerates. But
this one wasn't moving at all.
Then, in an instant, it went from completely stationary to its usual
rotational speed (in the feathered position).
I've never seen this before- in about 18 months of flying on these
machines. It was the starboard engine, so that ruled out the
possibility that they had left the little restraint rope on the prop
(not a likely event, but I was searching for explanations).
I am aware that this turbine has a free-rotating prop (ie the turbine
that drives the prop is not connected to the shaft that is driven when
the engine starts) so, in theory, it is possible to restrain the prop
while the engine starts (although I wouldn't like to try it). ...
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Author: RMKRMK Date: May 1, 2008 16:10
"Coop" chariotnose.netwheel.au> wrote in message
news:eh3j1459jg7s4lc5u5rujoiab6u5h5lps7@4ax.com...> INteresting and unusual observation at Adelaide airport a couple weeks
> ago:
> I fly Rex every week at present, so I am often in the Adelaide
> terminal watching other departures while awaiting my flight.
> Observed an S340 commence startup, but something was wrong- the heat
> haze was emerging from the rear of the turbine, but the prop wasn't
> moving.
> Most of you will know that when the S340's turbines start up, the prop
> begins rotating slowly at first, and then steadily accellerates. But
> this one wasn't moving at all.
> Then, in an instant, it went from completely stationary to its usual
> rotational speed (in the feathered position).
> I've never seen this before- in about 18 months of flying on these
> machines. It was the starboard engine, so that ruled out the
> possibility that they had left the little restraint rope on the prop
> (not a likely event, but I was searching for explanations).
> I am aware that this turbine has a free-rotating prop (ie the turbine
> that drives the prop is not connected to the shaft that is driven when ...
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Author: RTRT Date: May 1, 2008 23:41
>
> If they have no APU, it could be fitted with a prop brake. That allows
> the engine
> to be used as an APU without the prop turning.
>
> The early model ATR42's had no APU, with a prop brake fitted.
As distinct from the BAe 146 which has nothing BUT APUs :-)
I guess that is lateral thinking, since the engine is going to be doing the
job of a/c and general power supply most of the time anyway, so saves
duplication of accessories.
But it sure gives a new meaning to the term "live prop"!
AFAIK the earliest versions used 2,000 shp engines - that's a bloody lot of
grunt if the prop brake lets go (though I suppose they would be idling when
used as an APU )
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Author: CoopCoop Date: May 2, 2008 05:17
On Fri, 2 May 2008 09:10:06 +1000, "RMK" bigpond.com> wrote:
>
>"Coop" chariotnose.netwheel.au> wrote in message
>news:eh3j1459jg7s4lc5u5rujoiab6u5h5lps7@4ax.com...>> INteresting and unusual observation at Adelaide airport a couple weeks
>> ago:
>> I fly...
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Author: SnapperSnapper Date: May 7, 2008 14:11
Coop wrote...
> I am aware that this turbine has a free-rotating prop (ie the turbine
> that drives the prop is not connected to the shaft that is driven when
> the engine starts) so, in theory, it is possible to restrain the prop
> while the engine starts (although I wouldn't like to try it).
The power turbine, as you pointed out, is driven by exhaust gas flow from
the main turbines in the same way that the fan section (N3?) on a turbo
fan jet engine is driven.
The prop brake is an interesting concept. I s'pose it makes sense, to
allow you to run an engine for on board power without risking eviscerating
wandering LAMEs and FOs doing their walkround...
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