[ARC5] FCC General exam, now carb heat

[Sheldon Daitch]

Frank,

Yes, carb heat does have an impact on engine RPM and engine power output, if applied and
there is no change of the mixture control,  but that doesn't seem to be the intent of the 
question, as posed by Wayne's comments, per "What effect does carburetor heat have 
on the engine fuel-air mixture?"

One would not normally use carb heat unless there is a possibility of carburetor icing,
and low engine RPM, hence the need for application of full carb heat if there is an indication
of reduced engine performance or when operating at low engine RPM situations, below the
green arc on the tach.

By the same token, one of our check list procedures, if I remember correctly, at the Clark
Air Base Aero Club many years back, because of the high temperatures and high humidity
conditions most of the year, prior to take off, we did a ground adjustment of the fuel
mixture on the C-152 aircraft, reducing the fuel mixture slightly for an engine RPM
increase noted on the tach.  This was to increase the power for better takeoff performance,
especially on the short club runway at Clark.

73

Sheldon



-----Original Message-----
From: arc5-bounces at mailman.qth.net [mailto:arc5-bounces at mailman.qth.net] On Behalf Of Francesco Ledda
Sent: Wednesday, November 27, 2013 1:14 AM
To: 'Robert Eleazer'; arc5 at mailman.qth.net
Subject: Re: [ARC5] FCC General exam

It does have applicability! Carb heat has a clear impact on RPM and engine output power.  Max engine efficiency is at EGT peak.

This is fully covered on all pilot training material; it is fundamental to deal with possible carb ice.

Frank
KF5RXV

-----Original Message-----
From: arc5-bounces at mailman.qth.net [mailto:arc5-bounces at mailman.qth.net] On Behalf Of Robert Eleazer
Sent: Tuesday, November 26, 2013 2:24 PM
To: arc5 at mailman.qth.net
Subject: Re: [ARC5] FCC General exam

I have a real problem with pointless questions on Govt exams.

For example on a Private Pilot written exam, they asked : "What effect does carburetor heat have on the engine fuel-air mixture?"

As an engineer, I knew that heating the intake air enriches the engine mixture ratio because the air is thus less dense.  But I never saw that taught in any ground course and the fact seemed to have no applicability to light aircraft operations.  In other words, I figured most people would not know what I know, and answered 'No effect."  The correct answer was indeed that it enriches the air fuel mixture.

Trivia questions have no place on license exams!  That "highest layer"
question seems to fit that concept to me. 

Wayne
   
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