The approach and landing phase are the times when carburetor icing is MOST likely to occur.
Once a carburetor has ice, it may take a period of time for full application of carburetor heat to clear any ice. Furthermore it is possible to have enough ice accumulation that application of full throttle and carburetor heat would be insufficient to melt carburetor ice, and little or no additional power would be available at go-around.
So in short, not applying carburetor heat puts you at unacceptable risk of loss of power in the event of a go-around, and potentially even in the event of the need for additional power to compensate for wind shear on approach and for glide path adjustments.
Having examined the risks of no-carb-heat on approach, we should look at the secondary consequences. The operation is contrary to the POH, and the POH is the manufacturer's best guidance for the safe operation of the plane. The practice of asking yourself, "What would the accident review board have to say about this?" is a healthy tool for evaluating decisions. To deviate from the POH, and from conventional wisdom and practice in a critical phase, where there is little recovery time, presents an unreasonable risk on your flights, and is scarcely defensible. Without an articulable and compelling argument as to why EVERY time you make an approach and landing, the carburetor heat should be off, you are hard pressed to justify a deviation from the manufacturer's guidance.
Ok let's go to an extreme, and say that you are landing in high winds at a desert strip with blowing sand across the runway. In a situation like that, and experienced private pilot might elect to turn off carb heat just prior to landing to prevent unfiltered air with sand from being ingested into the engine. On the other hand, if the wind is blowing that hard, the possibility of a missed approach and go-around is even higher.
There are circumstances when carb heat may be left off on an approach. If the aircraft is equipped with a carb temp gauge, and the carb temp has been verified to be above 32F, then it is commonly considered acceptable to avoid carb heat. Some planes equipped like that will also have a warning alert to announce temperatures which are conducive to carburetor icing. That alert is often coupled with an ice detector sensor in the carburetor. Likely your 152 has neither a carburetor temperature gauge, nor a carburetor ice annunciator.
Let's also talk training risks, since you are a student pilot. Your operations for some time will be as a single pilot, and your procedures should be designed to minimize risk. One way to accomplish that is to simplify your procedures so that they can be accomplished by rote. Having the same procedure each time, without the need to collect data and make evaluations, helps simplify your piloting chores. You are not flying complex aircraft with complex pilot chores, and you do not have the benefit of a second crewmember to make observations and read you checklists.
Most CFIs, DPEs (pilot examiners) and FAA Operations Inspectors, will expect that you follow the POH and the manufacturer's checklist and procedures. In the case of the 152, that will be to turn on carburetor heat prior to the reduction of power (in the pattern). On balked approach, the procedure is to apply full throttle, and at most altitudes, verify mixture rich, and then remove carb heat. If the removal of carb heat causes a reduction in power (or RPMS) then carb heat is to be reapplied.
There may be other aircraft with different procedures, but you are not flying them. You are flying a 152, and it would be best practice and a defensible position to fly in accordance with the manufacturer's published procedures.
If you were taking your private pilot check ride with me, and you failed to apply carburetor heat in a C152 lacking a carburetor temperature gauge and/or ice sensor, you would not pass the check ride.
Finally, let me just add a story...on a crisp fall day, without exceptional humidity, a student/instructor were flying in the pattern doing touch and gos. The airport was surrounded on all sides by quarry, with a road leading to the flight school. That road also had the power lines to operate the stone handling and crushing quarry equipment. The plane was a new C152, the first year that they were available. It was later found that the cable had slipped in coupler on the valve for carb heat. You know where this is going. The student was mis-aligned on her approach, and when she applied full throttle for a balked approach, insufficient power was available to establish a climb. The instructor took over, and had to weave the wings between 13.2kV three-phase power lines on each side of the road, to land the plane on the road to the flight school.
Why adopt practices which will unnecessarily test your exceptional flying skills?
