You caught the error. For those who didn't here is an explanation. Notice
how the error effects perception.
Here is the text clip:
...heat generated by the system made the
hard drives hot enough to fail. Aboard
an airplane, the hard drives would
probably get 10-20 degrees Celsius (50 to
68 degrees Fahrenheit) hotter than in a
laboratory, he said.
The reference here is to temperature rise, not absolute temperature. No doubt
the author didn't know the difference and when he added the conversion in
parentheses used a conversion table instead of a conversion factor. It should
read (18 to 36 degrees Fahrenheit). The significance is 36 degrees F (rise) is
within the manufactures limits but 68 degrees F (rise) is probably not.
Putting it in terms that are a little easier to understand using the
manufacture's data sheet to calculate maximum ambient temperature for the
quoted rises, the cabin temp must be maintained at 63 F as the author wrote
it. The correct maximum is 95F. I think the author has significantly
distorted the perspective unless you never pay attention to temperature in
Fahrenheit degrees.
Fred Townsend
"Price, Ed" wrote:
Ed Price
[email protected]
Electromagnetic Compatibility Lab
Cubic Defense Systems
San Diego, CA USA
858-505-2780 (Voice)
858-505-1583 (Fax)
Military & Avionics EMC Is Our Specialty
Shake-Bake-Shock - Metrology - Reliability Analysis
>-----Original Message-----
>From: Fred Townsend [ mailto:[email protected]]
>Sent: Wednesday, February 19, 2003 12:42 AM
>To: Ken Javor
>Cc: Gary McInturff; EMC-PSTC (E-mail)
>Subject: Re: Swissair 111 - long winded even by my standards but an
>interesting article
>
>
>
>Scary! I squirmed in my seat as I read the article. You see I did the
>electrical design part of a similar system. Our system had a
>critical design
>flaw. It was a mechanical error so I was not responsible for
>the error but it
>could have crashed the airplane. Luckily we did not use a
>contractor for
>certification. We submitted straight to the FAA. The FAA
>spotted the problem
>and it was soon fixed. It makes me wonder what would have
>happened if we used a
>contractor to certify.
>
>In another vein, did anyone else pick up the error in the
>article? It related to
>the disk drive. It probably was the reporter's error. I see
>errors of this
>kind so frequently when you have a journalist or English major
>writing about
>scientific issues. They are not equipped to do the job.
>
>Fred Townsend
Do you mean:
"Aboard an airplane, the hard drives would probably get 10-20 degrees
Celsius (50 to 68 degrees Fahrenheit) hotter than in a laboratory, he said."
I just assumed that it was the reporter having a problem with arithmetic. I
was more interested in the comment that the heat rise "observed in the
laboratory" would probably have been even hotter in a real installation. So
why didn't they get a typical seat, stick it in an altitude chamber, and
find out what the heat rise really was?
I'm not very familiar with the certification process for adding a gadget to
an aircraft. But, it seems to me that the aircraft modifiers, like SBA, are
supposed to use only accepted or certified parts in the modification. It
seems like there's a gap, from the time that the manufacturer's first FAA
consultant bailed out of the job, and the time when SBA started installing
the systems onto aircraft. I didn't see anywhere in the story that the
entertainment systems were ever "certified" or whatever they call it, to be
used by anyone.
Ed
Ed Price
[email protected]
Electromagnetic Compatibility Lab
Cubic Defense Systems
San Diego, CA USA
858-505-2780 (Voice)
858-505-1583 (Fax)
Military & Avionics EMC Is Our Specialty
Shake-Bake-Shock - Metrology - Reliability Analysis
