Peter wrote:
the most recent FAA word on “known icing”?
Yes Bell-AOPA is the last FAA legal interpretation, I am not aware of anything new?
Maybe worth looking at the definition in the AIM 7.1.20 that 2006 Letter refer to?
https://www.faa.gov/air_traffic/publications/atpubs/aim_html/chap7_section_1.html
The previous Letter was in in June 2006: “known icing conditions exist when visible moisture or high relative humidity combines with temperatures near or below freezing.” 
the FAA backtracked after pressure from AOPA & Manufacturers
https://www.govinfo.gov/content/pkg/FR-2007-04-03/pdf/07-1620.pdf
This does not mean the FAA has a light sentence, they do prosecute every single pilot who fly in actual icing conditions (observed or recently reported) that exceeds his aircraft limitation (assuming he is not dead) or cause large ATC disruption due to icing or crash & land covered with ice, this applies to FIKI & non-FIKI, the only distinction is an operational one, in FIKI you can fly in actual ice, non-FIKI you have to exit…
No. I posted on another thread a much more recent report on aircraft icing commissioned by the DGAC but with FAA being one of the contributors. It is in English and is a very comprehensive if not slightly scary study. It is however, long.
Is this local copy the most recent FAA word on “known icing”?
Totally off topic. No connection at all
RobertL18C wrote:
I close carb heat on short final, but the Lycoming 320 doesn’t make much ice; but a carb heat check on a damp cool day usually produces a slight RPM rise on the power check
I had the impression carb heat on Lyco 320 is bolted to the engine crankcase,
- When you are already in cruise with CHT with T&P hot like Mexico, there are not much carb ice anyway
- When on ground on first flight on the day, the crankcase is cold and you do expect to see that RPM drop
These lovely rock solid US engines will have some CHT & EGT feed back to carburetor via “conduction & radiation” without any need to introduce hot air “convection”, in the other hand they were designed in Pennsylvania and heavily flown in hot Texas/Florida/California where carb icing is not a big worry (if the air is moist it’s usually CB/TS), so their manual may not reflect the exact carb heat risks on low CHT in moist weather (99% of UK GA flying is 3kft, 10C, 70%-100% humidity, mostly circuit on full rich mixture with CHT in 2xx)
Lyco 320 is not immune to carb icing, it happens and one probable accident cause:
https://assets.publishing.service.gov.uk/media/54ae3f4740f0b6245d000007/Piper_PA-28-161_Cadet_G-BXJJ_01-15.pdf
In the other hand Gipsy Major, WV, Conti engines you may find in Chippies, Tiger Moths, Jodels will have cylinders & carburetors sitting in different planets, these engine have consistently delivered when it comes to carb icing say in UK, Canada, France that people would advise to keep it ON all the time and hope for the best (not the best strategy if carb ice forms deep inside the induction)
A bit off topic tough but anyone flying in IMC conditions would probably move from carburated engine to injected engine with alternate air (small step in the path to FIKI), unless they are flying TMG under cloud-base or keep it light IMC
RobertL18C wrote:
Going from low power to full power with carb heat applied, could on some engines, result in a rich cut (too much fuel in the mixture), or potentially detonation as the engine power increases with too lean a mixture.
I get that there might be less air (Hot air, less dense etc) and a rich cut, Ive always been taught to apply power “smoothly”… but how do you get the case of too little fuel? (ie the detonation case)
Or am I being dense… ( 
)
Carb heat switches air intake to warmer air which has the effect of making the air less dense. Going from low power to full power with carb heat applied, could on some engines, result in a rich cut (too much fuel in the mixture), or potentially detonation as the engine power increases with too lean a mixture.
Training schools seem to teach going full power (C152 or PA28), carb heat closed from memory, and tail wheel conversion appears to introduce closing carb heat to cold on short final. I close carb heat on short final, but the Lycoming 320 doesn’t make much ice; but a carb heat check on a damp cool day usually produces a slight RPM rise on the power check, so there are conditions where ice is in the carburettor.
As @Peter pointed out, this is far removed from FIKi thread.
Airborne_Again wrote:
Some POH warn that this may cause detonation
Does the POH explain ho that might happen?
gallois wrote:
power first before carb heat to cold on a go round.
Some POH warn that this may cause detonation.
I was taught to apply carb heat when configuring the aircraft downwind and then power first before carb heat to cold on a go round.
Also to apply carb heat in humid conditions whenever one is on reduced power, such as descending to circuit height.
