C85 and Marvel carb Ice

[astjp2]

If it was certified as compliant, then it is good, or the person returning to service needs to comply prior to returning to service.

[PA1195]

There are reports from PA-12/18 pilots on Supercub.org using Sutton STC'd replacement mufflers and carb temp probes that the indicated temp rise fails to comply with CAR 3's temp rise:

http://www.supercub.org/forum/showthread.php?53758-Exhaust-Advice

What does that have to do with Taylorcraft and different engines/exhaust, and especially those without a carb temp indicator? I'm open to suggestions but for me I currently want to see a positive drop in rpm with carb heat applied on the ground and in the air. How much of a drop? Again not sure but something like a drop during a mag check might be a starting point to work towards while flying with power not at idle. Which is a good reason to apply carb heat before reducing power - always.

Comments?

Gary

[PA1195]

The F-19 with O-200 engine is a "Flight Manual" aircraft certified under CAR 3. Earlier Taylorcrafts were certified under older CAR 4.

For the F-19 carb heat is checked on runup before flight like all carb engines. The Manual says with carb heat on the drop should be 50-125 @ 1700 rpm.

So there's some guidance. How much that applies to other Taylorcraft engines and exhaust systems should be verified.

Gary

[astjp2]

It passed or it would not have ever been stc’d so just because someone has a gauge on the dash, does not mean it is accurate, calibrated or even meets the testing requirements, or even installed without modifying it

[PA1195]

It passed or it would not have ever been stc’d so just because someone has a gauge on the dash, does not mean it is accurate, calibrated or even meets the testing requirements, or even installed without modifying it

Perhaps. Dawley reportedly made the muffler and another entity STC'd the application. If you read more you'll note the apparent lack of effect on engine rpm when carb heat was used. That was the common complaint - lack of engine response. Later others reported carb temp rise.

The heat source is external to the muffler shroud and taken off the 2:1 Y on one inlet. Bellanca used a similar "Delano style" muffler but chose to pull carb heat off part of the internal area under the shroud. My experience with that application was that it worked well.

So again trust but verify any rpm drop and response to carb heat. STC's are done by humans and we all know how reliable we are.

Gary

[astjp2]

I have also seen pilots pull on carb heat and induce carb ice...Tim

[LostnSpace]

It's in the CAR's and depends under which the plane was certified...

For CAR Part 04 planes pre-WWII: 4.6291 says an adequate means shall be provided for preventing the formation of ice in the engine carburetors. I haven't discovered a specific temp rise but ???

Post WWII CAR 3 planes 3.606 (a)...for sea level engines with a venturi carb +90F rise at +30F air temp w/o visible moisture @ 75% of max continuous power. It's a bit clearer here for those planes that apply.

Now the question. Does changing design of exhaust or intake affect that temp rise? How about EGT adjustments? Do STC's or Field Approvals for engine accessory changes consider the requirements? How do we deal with CAR's for the run of Taylorcrafts and the requirements have changed?

Gary

I'll agree with guys that it's important, but when i put the C-90 in the T, and put in the paperwork it would have a Luscombe exhaust, it sailed through and nothing was said about carb heat, I'll watch it close however

[PA1195]

I'll agree with guys that it's important, but when i put the C-90 in the T, and put in the paperwork it would have a Luscombe exhaust, it sailed through and nothing was said about carb heat, I'll watch it close however

See Post #14 for a suggested improvement in carb heat...and why it might be needed. You might also contact CAP and determine what basis they used for DER approval of the carb heat rise (for example which CAR they follow and comply with for your model Taylorcraft): http://dc65stc.blogspot.com/2010/09/...onversion.html

Gary

[astjp2]

They probably used the philosophy of one approved part is eligible to be used on another aircraft, ie it worked on the Luscombe, it will work on the Taylorcraft. Similar installation...

[M Towsley]

Applying the carb heat effectively enrichens the fuel mixture.

I said this one and got taken to task my Tom. Does it???

[Robert Lees]

It does.

[3Dreaming]

I said this one and got taken to task my Tom. Does it???

Marty, if you are talking about me, I don't remember the conversation or the context.

[LostnSpace]

See Post #14 for a suggested improvement in carb heat...and why it might be needed. You might also contact CAP and determine what basis they used for DER approval of the carb heat rise (for example which CAR they follow and comply with for your model Taylorcraft): http://dc65stc.blogspot.com/2010/09/...onversion.html

Gary

Thank you Gary, yes, I ran across that before I started to install the exhaust, so i printed it and have kept it by the bench to get them exactly like what it shows, thank you

[M Towsley]

Marty, if you are talking about me, I don't remember the conversation or the context.

Not that big of a deal, Tom, it was on here years ago. Just wanting to figure out which answer may be correct.

[Scott]

Have a look at your EB6 flight computer, specifically the window for density altitude. Pick an altitude and typical ambient temperature, now increase the temperature at your chosen altitude by 50 degrees and read the density altitude.

Carb heat effectively increases density altitude by several thousand feet i.e. lowers the air density. Less air by weight for the same amount of fuel....engine runs rich.