Originally Posted by
lelebebbel
The way I'm reading that, the carb heat knob was indeed unlocked, but found in the full down (off) position. So it can't be determined with 100% certainty where exactly it was when the aircraft was flying, as it moves up and down in response to the collective. For example, if the pilot raised the collective to max pitch before impact, that would also lower the carburetor heat knob to off, (almost) regardless of where it was before. Of course I can't second guess the conclusion that carb ice was the most likely cause here.
What is a little surprising to me is that there is, after 40+ years, still no bulletproof solution to this carb ice problem that affects especially the R22. How is it possible that the carb air temperature gauge STILL doesnt accurately show what the temperature is inside the critical area of the carb, as it does on the R44. The procedure, paraphrased is still "go by the gauge, but depending on power just add carb heat anyway, because this critical gauge doesn't read correctly at half the time, and if it all goes wrong you got about a second to get the pole down or you are dead. Good luck". Carb ice is far more common than loss of engine oil pressure for example, and it will shut your engine down at least as fast but with fewer warning signs. There's a red light for the oil pressure and a redundant gauge. How is there not also a big yellow warning light that turns on when the cat gauge is in the yellow arc. Or an automatic electric - or engine oil based heater in addition to the mechanical. All this stuff exists and has been in use in other carburetor engines for half a century. And that's before you consider fuel injection.
Hmm, I could of sworn it said the assist was locked, but oh well, my bad.
Anyway, I've never heard that the guage isn't accurate, only that below 18" MAP you need to ignore it and pull full heat, because of where the probe is, it won't detect the temp drop due to that venturi effect thing.
Still,..the problem with carb heat assist, is that you have to remember to set it in a hover. If you set it on the ground, then the assist will lower it back into the yellow when you pick up. Its one reason I prefer the Beta.
,...and you can't just have it full all the time, because you'll foul out the plugs.
In all the years flying 22's (primarily in carb icing conditions) I've never had an issue with ice. That's why I'm still going with this accident being due to pilot distraction as to the underlying cause.