Piper vs Cessna carb heat

[JordanD]

Why is it that in the Cessnas carb heat is used as an anti icer and used quite frequently and in the Pipers it is only used as a deicer and not used all that much? Both use the same engine, so what is the reason for the difference?

 

[CFI A&P]

Don't recall off the top of my head, but it may be a pressure carb vs float carb issue.

 

[jeflies]

I thought it had to do with the oil sump housing all the induction parts on the piper. It's been several years but somewhere along the way that's what one of my instructors told me


Sent from my iPhone

 

[Blackhawk]

http://www.generalaviationnews.com/2010/01/11/carb-ice-suspected-in-piper-crash/

http://aircrashed.com/cause/cCHI87FA187.shtml

http://www.check-six.com/Crash_Sites/PlaneInATree-N6487J.htm

http://www.asa2fly.com/files/docs/900108NtsbRecCarbHeat.pdf

"One of the prime reasons for the persistence of accidents caused by
carburetor ice is the unpredictable nature of the phenomenon, and the
difficulty or inability of the pilot to detect it. Further, there are
documented cases of pilots who did detect carburetor ice, but too late to
avoid loss of engine power.
A typical accident of this type occurred on May 5, 1980, when a Piper
Cherokee PA-28-151, N43954, lost engine power while on final approach to the
Front Royal, Virginia Airport.4J The pilot was unable to obtain sufficient
power from the engine, and the airplane collided with power lines 1/2 mile
short of the runway. The pilot suffered a broken back, and the airplane was
destroyed. Meteorological conditions at the time of the accident were, in
part: sky clear, visibility 15 miles, temperature 80 F.
...
"Related factors included weather conditions "conducive to carburetor/induction
system icing." According to the Piper Cherokee Owners Handbook, "Carburetor
heat should not be applied unless there is an indication of carburetor icing,
since the use of carburetor heat causes a reduction of power which may be
critical in case of a go-around. Full throttle operation with heat on is likely to
cause detonation." The pilot stated that she had no indication of carburetor ice
until she attempted to increase power.
...
Accordingly, the Safety Board believes that pilots need more definitive
guidance from airplane manufacturers concerning the use of carburetor heat on
the descent and/or before-landing checklists. Descents in most carburetorequipped
general aviation airplanes can be conducted without adverse
consequences to the powerplant with full carburetor heat on when power is
reduced below the normal cruise flight engine power setting (that is, below
the green arc on the tachometer or the manifold pressure gauge).5J The use
of this procedure would preclude the formation of carburetor ice when
detection of such formation could be difficult, in lieu of more specific
guidance or procedures from manufacturers concerning designated airplane
models .
...
Therefore, the National Transportation Safety Board recommends that the
Federal Aviation Administration:
Amend, as necessary, in conjunction with the General
Aviation Manufacturers Association and the airframe
manufacturers, the descent and before-landing checklists
in the pilot’s operating handbooks and airplane flight
manuals of carburetor-equipped airplanes to require the
use of full carburetor heat when engine power is reduced
below the normal cruise power range (the green arc on
the tachometer or the manifold pressure gauge), or below
an alternate engine power setting as determined by the
manufacturer. (Class 11, Priority Action) (A-89-140)"

 

[rframe]

This past fall, I went to change the oil in my 150 on a damp cool day. Finished up and did a run-up for a leak check. Thing ran horrible, had me confused for a minute, then I looked out and saw the vapor trail coming off the propeller tips.... Shutdown and looked at the induction system and it was complete encased in thick frost from induction icing during a short run-up on the ground. Kinda cool.

 

[trafficinsight]

150's are notorious for that, they just don't make enough heat in that stressed out sewing machine under the cowl.

I believe, with no basis in anything solid, that the difference between Cessna and Piper is that the Piper has a longer induction tract inside the cowl than the Cessna does; One to two feet for the piper vs. about 3 inches for the Cessna. Both run the induction air through the oil sump after the carburetor to help vaporize the fuel.

 

[Roger Roger]

I've only had carb ice in the Milk Stool once, during an extended sit/taxi on the ground. I fly in conditions that usually fall squarely in the middle of the carb ice graph.

 

[MidlifeFlyer]

http://www.generalaviationnews.com/2010/01/11/carb-ice-suspected-in-piper-crash/
http://aircrashed.com/cause/cCHI87FA187.shtml
http://www.check-six.com/Crash_Sites/PlaneInATree-N6487J.htm
http://www.asa2fly.com/files/docs/900108NtsbRecCarbHeat.pdf
"One of the prime reasons for the persistence of accidents caused by
carburetor ice

Thanks for mentioning and referring to this. If you didn't, I would have. I became interested in the issue after I had a carb ice in IMC incident that turned into an emergency and began to research the issue a bit.
You can add this ASRS report ACN: 841103 to your list.
The FAA and the manufacturers never went along with the recommendation.

 

[Blackhawk]

Thanks for mentioning and referring to this. If you didn't, I would have. I became interested in the issue after I had a carb ice in IMC incident that turned into an emergency and began to research the issue a bit.
You can add this ASRS report ACN: 841103 to your list.
The FAA and the manufacturers never went along with the recommendation.

Yeah, I guess fear of litigation won out. At least that is all I can figure.
I know we've discussed it before- adding carb heat will not hurt anything in an approach. Not having it on could be critical. Piper, Cessna- if the airplane has a carbureted engine use carb heat.
Thanks for the ASRS report number. I am going to add it to my list of incidents/accidents for pilots. Not just the Piper factor, but full power as well.

 

[JordanD]

Yeah, I guess fear of litigation won out. At least that is all I can figure.
I know we've discussed it before- adding carb heat will not hurt anything in an approach. Not having it on could be critical. Piper, Cessna- if the airplane has a carbureted engine use carb heat.
Thanks for the ASRS report number. I am going to add it to my list of incidents/accidents for pilots. Not just the Piper factor, but full power as well.

I'd be a little worried about using it in the Piper like that, the POH says the air that's coming in when the carb heat is on is unfiltered and to avoid using it for extended periods of time.

 

[CFI A&P]

I'd be a little worried about using it in the Piper like that, the POH says the air that's coming in when the carb heat is on is unfiltered and to avoid using it for extended periods of time.

Many airplanes run with out induction filters, such as Pitts, Extra, other aerobatic airplanes, Mooney's and such. Sucking some dirt in is better than having induction icing.

 

[Blackhawk]

I'd be a little worried about using it in the Piper like that, the POH says the air that's coming in when the carb heat is on is unfiltered and to avoid using it for extended periods of time.

Did you actually read the NTSB report I mentioned?

 

[MidlifeFlyer]

I'd be a little worried about using it in the Piper like that, the POH says the air that's coming in when the carb heat is on is unfiltered and to avoid using it for extended periods of time.

That's true for carb heat regardless of the airplane - Cessna, piper, whatever. It's a bigger issue for ground ops; not very significant in the air unless you're in a dust cloud or sandstorm.

 

[MidlifeFlyer]

Yeah, I guess fear of litigation won out. At least that is all I can figure.

I don't see a fear of litigation connection here. To the extent that it plays a role, I see "damned-if-you-do-damned-if-you-don't scenarios, which would make the topic litigation-neutral.

Thanks for the ASRS report number. I am going to add it to my list of incidents/accidents for pilots. Not just the Piper factor, but full power as well.

For those who don't want to look for it, here's a pdf printout: http://midlifeflight.us/downloads/files/AsrsReport841103.pdf

 

[gotWXdagain]

I've always wondered about the necessity for carb heat in the Seminoles, the air intake takes air that has already passed over the top of the CHT and the raise in temperature associated should be enough to bring the Relative Humidity of the air down low enough for icing not to form, no?

 

[Roger Roger]

I've always wondered about the necessity for carb heat in the Seminoles, the air intake takes air that has already passed over the top of the CHT and the raise in temperature associated should be enough to bring the Relative Humidity of the air down low enough for icing not to form, no?

Nope. Still plenty easy to get carb ice there.