The Visitor
November 8th 05, 08:53 PM
Were they the wide cord butcher props? Perhaps they spin slower?
Mine are electrically heated but only the inboard third or so. (seneca)
Peter wrote:
> The other day I was talking to a commercial pilot of a big twin
> passenger turboprop. He has been iced up a few times and recently was
> down to 200fpm climbing flat out through FL150; looking out of the
> window he saw a bit of ice on the wings but enough on the prop for it
> to be visible while the prop was rotating.
>
> He has rubber boots, and the props are electrically heated.
>
> Now, I know a bit about mach heating and I can work out the
> temperature rise over SAT (i.e. the TAT) using the Jepp CR-5 circular
> slide rule. At 200kt IAS at FL150 his airframe temperature should be
> SAT+9C. At 300kt TAS the TAT should be SAT+12C which nearly puts him
> out of the stratiform cloud icing range of 0C to -15C or so.
>
> So he can get ice on the airframe especially in slow flight, and
> especially if there are local mach numbers where the airflow slows
> down.
>
> What puzzles me is the prop. Assuming a SOP of max revs if icing is
> likely, much of the prop is going at between mach 0.5 and mach 0.8,
> with a temp rise of 15C to 30C, so even on a slow piston aircraft only
> the innermost part should ever ice up.
>
> Is this true?
>
> I haven't been able to test this myself because I have a TKS de-iced
> prop (TB20) and always have the deicing on if in IMC below 0C. I've
> had up to 1cm of ice on the wings but never noticed any performance
> drop so presumably the prop was doing OK.
>
> Peter.
> --
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> E-mail replies to but remove the X and the Y.
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Mine are electrically heated but only the inboard third or so. (seneca)
Peter wrote:
> The other day I was talking to a commercial pilot of a big twin
> passenger turboprop. He has been iced up a few times and recently was
> down to 200fpm climbing flat out through FL150; looking out of the
> window he saw a bit of ice on the wings but enough on the prop for it
> to be visible while the prop was rotating.
>
> He has rubber boots, and the props are electrically heated.
>
> Now, I know a bit about mach heating and I can work out the
> temperature rise over SAT (i.e. the TAT) using the Jepp CR-5 circular
> slide rule. At 200kt IAS at FL150 his airframe temperature should be
> SAT+9C. At 300kt TAS the TAT should be SAT+12C which nearly puts him
> out of the stratiform cloud icing range of 0C to -15C or so.
>
> So he can get ice on the airframe especially in slow flight, and
> especially if there are local mach numbers where the airflow slows
> down.
>
> What puzzles me is the prop. Assuming a SOP of max revs if icing is
> likely, much of the prop is going at between mach 0.5 and mach 0.8,
> with a temp rise of 15C to 30C, so even on a slow piston aircraft only
> the innermost part should ever ice up.
>
> Is this true?
>
> I haven't been able to test this myself because I have a TKS de-iced
> prop (TB20) and always have the deicing on if in IMC below 0C. I've
> had up to 1cm of ice on the wings but never noticed any performance
> drop so presumably the prop was doing OK.
>
> Peter.
> --
> Return address is invalid to help stop junk mail.
> E-mail replies to but remove the X and the Y.
> Please do NOT copy usenet posts to email - it is NOT necessary.