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RESTRICTED    T.O. No. 02-35GC-1

c. During some conditions of flight such as in icing conditions or low altitude flight, it may be desirable to operate the engine at part throttle while using the turbo-supercharger. Under those conditions extreme caution must be exercised if the throttle is opened farther, in order that excessive manifold pressures will not be obtained.

d. The carburetor air temperature should be maintained between 15 degrees C and 35 degrees C (59 degrees F and 95 degrees F). Where the above temperatures cannot be maintained with the intercooler heat control in the "Hot" position, advantage may be taken of the heat of compression of the turbo-supercharger. To obtain the maximum carburetor air heat from the supercharger move the supercharger control toward the "On" position and the throttle toward the "Closed" position to maintain desired manifold pressure. Under these conditions extreme caution should be exercised if the throttle is opened farther in order that excessive manifold pressure will not be obtained.

11. Fuel and Oil

a. The grade of fuel to be used in the operation of these engines is specified in section III. Refer to T.O. No. 06-5-1 for general information on the use and disposition of fuels

b. General information on lubricants for these engines may be found in T.O. No. 06-10-1.

12. Detonation

a. General. Refer to T.O. No. 02-1-7 for general information and instructions pertaining to detonation in aircraft engines. 

b. Indications of Detonation

(1) Engine roughness does not necessarily indicate that detonation is present but when unusual roughness is encountered it may be due to detonation.

(2) An increase in cylinder temperature due to detonation, if apparent, would first be noticed on the cylinder head thermocouples. Cylinder temperatures, however, cannot be relied on for a definite and complete indication of detonation. 

(3) An erratic reading of the fuel/air ration meter may indicate detonation and should be investigated. If, as the mixture is leaned out, the indicating needle does not show a leaner mixture, or backs up on the scale towards the rich side, detonating has probably been encountered.

(4) If exhaust stacks are visible, detonation may be indicated by intermittent puffs of dense black smoke, often accompanied with sparks or glowing carbon, in contrast to the indications of a rich mixture which is generally indicated by dull red flames with steady black smoke.

c. Causes and Prevention

(1) Use of fuel of too-low octane rating. See the proper grade of fuel is used.

(2) A too low fuel/air ratio. Do not operate at mixtures that are too lean.

(3) Operating engine above permissible limitations. Observe specific instructions in section III.

d. Stopping Detonation Immediately if Present. 

(1) Reduce the manifold pressure.

(2) Enrich the mixture.

(3) Reduce the carburetor air preheating to the minimum temperature at which icing of the carburetor may be prevented.

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