Aside from the cold why do carbureted airplane engines freeze up at high
altitude? I thought at high altitude there was very little moisture?

>Given the right weather conditions (cool and humid) the previous engine in
>my `79 CJ-5 would occasionally ice up the throttle butterfly. It was
>always a little exciting when it would happen, because I'd only notice
>when I was trying to take _off_ speed and the gas pedal would stay where
>it was. I'd have to give it more throttle to get it unstuck.
>


-Bill (remove "botizer" to reply via email)

 

Wblane did pass the time by typing:
> Aside from the cold why do carbureted airplane engines freeze up at high
> altitude? I thought at high altitude there was very little moisture?

Depends on the definition of "high" but for private(unpressurized) there
is a lot of humidity from sea level up to 8-9000ft. The pressurized craft
that fly up higher are usually turbofan or jet and aren't susceptible to ice
like a piston aircraft. (the control surfaces just get too cold and ice upon
decent causing loss of control) Which by the way is fixed somewhat by
having the fuel actually warmed in the wings as part of the heat management
system.

Keep in mind the cooling effect is from the venturi in the carb and the
addition of liquid fuel that takes heat to vaporize. The fuel is injected
just before the venturi opens up, then the charge gets room to expand.
Expanding gas cools and if it's cold enough it will start to cool the whole
carb until the whole shooting match is at freezing, then bad ---- happens.

... Yea, I hung around aircraft for a few years, but learned most from
the private pilots at work..

--
DougW

 

Wblane did pass the time by typing:
> Aside from the cold why do carbureted airplane engines freeze up at high
> altitude? I thought at high altitude there was very little moisture?

Depends on the definition of "high" but for private(unpressurized) there
is a lot of humidity from sea level up to 8-9000ft. The pressurized craft
that fly up higher are usually turbofan or jet and aren't susceptible to ice
like a piston aircraft. (the control surfaces just get too cold and ice upon
decent causing loss of control) Which by the way is fixed somewhat by
having the fuel actually warmed in the wings as part of the heat management
system.

Keep in mind the cooling effect is from the venturi in the carb and the
addition of liquid fuel that takes heat to vaporize. The fuel is injected
just before the venturi opens up, then the charge gets room to expand.
Expanding gas cools and if it's cold enough it will start to cool the whole
carb until the whole shooting match is at freezing, then bad ---- happens.

... Yea, I hung around aircraft for a few years, but learned most from
the private pilots at work..

--
DougW

 

Wblane did pass the time by typing:
> Aside from the cold why do carbureted airplane engines freeze up at high
> altitude? I thought at high altitude there was very little moisture?

Depends on the definition of "high" but for private(unpressurized) there
is a lot of humidity from sea level up to 8-9000ft. The pressurized craft
that fly up higher are usually turbofan or jet and aren't susceptible to ice
like a piston aircraft. (the control surfaces just get too cold and ice upon
decent causing loss of control) Which by the way is fixed somewhat by
having the fuel actually warmed in the wings as part of the heat management
system.

Keep in mind the cooling effect is from the venturi in the carb and the
addition of liquid fuel that takes heat to vaporize. The fuel is injected
just before the venturi opens up, then the charge gets room to expand.
Expanding gas cools and if it's cold enough it will start to cool the whole
carb until the whole shooting match is at freezing, then bad ---- happens.

... Yea, I hung around aircraft for a few years, but learned most from
the private pilots at work..

--
DougW

 

Yup, the venturi area needed to atomize fuel into gases creates low
pressure that further cools the carburetor throttle butterflies.
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/

DougW wrote:
>
> Depends on the definition of "high" but for private(unpressurized) there
> is a lot of humidity from sea level up to 8-9000ft. The pressurized craft
> that fly up higher are usually turbofan or jet and aren't susceptible to ice
> like a piston aircraft. (the control surfaces just get too cold and ice upon
> decent causing loss of control) Which by the way is fixed somewhat by
> having the fuel actually warmed in the wings as part of the heat management
> system.
>
> Keep in mind the cooling effect is from the venturi in the carb and the
> addition of liquid fuel that takes heat to vaporize. The fuel is injected
> just before the venturi opens up, then the charge gets room to expand.
> Expanding gas cools and if it's cold enough it will start to cool the whole
> carb until the whole shooting match is at freezing, then bad ---- happens.
>
> .. Yea, I hung around aircraft for a few years, but learned most from
> the private pilots at work..
>
> --
> DougW

 

Yup, the venturi area needed to atomize fuel into gases creates low
pressure that further cools the carburetor throttle butterflies.
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/

DougW wrote:
>
> Depends on the definition of "high" but for private(unpressurized) there
> is a lot of humidity from sea level up to 8-9000ft. The pressurized craft
> that fly up higher are usually turbofan or jet and aren't susceptible to ice
> like a piston aircraft. (the control surfaces just get too cold and ice upon
> decent causing loss of control) Which by the way is fixed somewhat by
> having the fuel actually warmed in the wings as part of the heat management
> system.
>
> Keep in mind the cooling effect is from the venturi in the carb and the
> addition of liquid fuel that takes heat to vaporize. The fuel is injected
> just before the venturi opens up, then the charge gets room to expand.
> Expanding gas cools and if it's cold enough it will start to cool the whole
> carb until the whole shooting match is at freezing, then bad ---- happens.
>
> .. Yea, I hung around aircraft for a few years, but learned most from
> the private pilots at work..
>
> --
> DougW

 

Yup, the venturi area needed to atomize fuel into gases creates low
pressure that further cools the carburetor throttle butterflies.
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/

DougW wrote:
>
> Depends on the definition of "high" but for private(unpressurized) there
> is a lot of humidity from sea level up to 8-9000ft. The pressurized craft
> that fly up higher are usually turbofan or jet and aren't susceptible to ice
> like a piston aircraft. (the control surfaces just get too cold and ice upon
> decent causing loss of control) Which by the way is fixed somewhat by
> having the fuel actually warmed in the wings as part of the heat management
> system.
>
> Keep in mind the cooling effect is from the venturi in the carb and the
> addition of liquid fuel that takes heat to vaporize. The fuel is injected
> just before the venturi opens up, then the charge gets room to expand.
> Expanding gas cools and if it's cold enough it will start to cool the whole
> carb until the whole shooting match is at freezing, then bad ---- happens.
>
> .. Yea, I hung around aircraft for a few years, but learned most from
> the private pilots at work..
>
> --
> DougW

 

Geez! you still don't see that compressed gases especially in
liquid form will freeze then release? Maybe, a grownup will let you open
their barbecue bottle, enough for you to prove the high school
experiment. Wear gloves and eye protection.
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/

Ted Azito wrote:
>
> Hardly the fault of propane then,was it? (Shades of Monty Python's
> stunned parrot....)
>
> Yes, it happens, more often a linkage problem than anything else. But
> this was about propane specific throttle freezeups.

 

Geez! you still don't see that compressed gases especially in
liquid form will freeze then release? Maybe, a grownup will let you open
their barbecue bottle, enough for you to prove the high school
experiment. Wear gloves and eye protection.
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/

Ted Azito wrote:
>
> Hardly the fault of propane then,was it? (Shades of Monty Python's
> stunned parrot....)
>
> Yes, it happens, more often a linkage problem than anything else. But
> this was about propane specific throttle freezeups.

 

Geez! you still don't see that compressed gases especially in
liquid form will freeze then release? Maybe, a grownup will let you open
their barbecue bottle, enough for you to prove the high school
experiment. Wear gloves and eye protection.
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/

Ted Azito wrote:
>
> Hardly the fault of propane then,was it? (Shades of Monty Python's
> stunned parrot....)
>
> Yes, it happens, more often a linkage problem than anything else. But
> this was about propane specific throttle freezeups.