Re: 1G or two 512's

Neil Harrington wrote:
> "SleeperMan" <SleeperMan@xxxxxxxxxx> wrote in message
> news:ew4gf.1277$h6.523690@xxxxxxxxxxxxxxxx
>> Neil Harrington wrote:
>>> "SleeperMan" <SleeperMan@xxxxxxxxxx> wrote in message
>>> news:AY4ff.1250$h6.494948@xxxxxxxxxxxxxxxx
>>>> phk wrote:
>>>>> It's like having 2 engines on an airplane - you have a spare if
>>>>> one goes bad, but you double the probability of one going bad :-)
>>>>
>>>> hm...not quite. You'll find out that planes with 2 engines can't
>>>> actually fly with only one, and ones with 3 engines can't fly with
>>>> only 2 of them...
>>>
>>> That could be called the Lindbergh Principle.
>>>
>>> Charles A. Lindbergh went with a single engine when his best-known
>>> competitors were using trimotors in their transatlantic attempts.
>>> His reasoning was just as both of you are saying: three engines
>>> would not protect against engine failure but would in fact *triple*
>>> the probability of such failure, and if one engine went out, at
>>> least in the early stages of the flight when the plane was carrying
>>> a huge fuel load, the two remaining engines wouldn't be able to
>>> keep it from going into the drink.
>>> Neil
>>
>> ok, i agree with huge weight and fuel. But, triple the
>> probability...i'd say rahter contrary, but only if you plan the
>> plane so it can fly with only one engine. See... with one engine
>> and, say probability of dying is once on 100 flights, that means
>> lost plane every 100 flights. With 2 engines, and same probability
>> (which means dying engine once in 1000 flights),
>
> I'm afraid your math is wrong there regarding probability.
>
> Say for the sake of argument you have an aircraft engine which is
> *guaranteed* to fail once every 100 flights. This is just taking your
> 1% probability and making it a certainty, for the sake of the
> example; other than that it's saying the same thing.
>
> Now you have two engines, *each* of which is guaranteed to fail once
> in every 100 flights. So when that plane makes 100 flights it will
> have two engine failures, one with each engine. You really have
> doubled the probability of engine failure for any given flight.
>
> You have, however, reduced the probability that *all* engines will
> fail on any given flight to 1 in 10,000 whereas with a single-engine
> aircraft the probability for engine failure on any given flight would
> be 1 in 100. So that's the twin-engine advantage.
>
>
>> that means one plane flying with only 1 engine every 100 flights,
>> since probability of dying both at the same time is veeeery low. Of
>> course, since weight is way bigger, plane can't get nearly so far as
>> one engine type, but at least it won't fall down (let's assume it
>> doesn't go via ocean)
>
> Yes, if it can fly on one engine that changes the situation entirely.
> The competitors for the Orteig New York to Paris prize in 1927
> started off with airplanes so heavily loaded with fuel that they
> could barely get off the ground with full power and a very long
> takeoff roll. Commander Byrd's Fokker trimotor in fact crashed on its
> first takeoff attempt, leaving the way open for Lindbergh to win the
> prize in his single-engine Ryan the following month. (Byrd's plane
> was repaired and later did make the transatlantic crossing, though it
> didn't make it to Paris so he wouldn't have won the prize anyway.)
>
> Neil
>
> Neil

OK, at the end i guess we concluded the same...that more than one engine is
probably installed because one wouldn't be enough for specific plane weight,
or maybe one would be too huge...


.

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