B-17 Pilots Manual.pdf

complete set of apparatus for determining the heightof the airplane above the ground. It is operative overan altitude range of 0 to 20,000 feet, 3.Qdit will worksatisfactorily up to 30,000 feet, before. the indicationsbecome erroneous. Operation of the set does not dependupon barometric pressure. It indicates altitudeof the aircraft above the terrain below the airplane,and has no reference to sea level. If the aircraft isflying over broken country, more than one peak willappear on the indicator, the highest one representingthe object closest to the airplane.(1) Place the power switch in the "ON" position.This energizes all parts of the set except the automaticvolume control which is controlled by a separateswitch. A pilot lamp at the lower center of the controlpanel ~hould light, indicating that the power is on.(2) As the tubes reach their operating conditions,the circle traces, and indicating lobes appear on thescreen of the indicator. During the first few minutesof operations the indications will be unsteady.KEY TO FIGURE65I. SEAT FOR AUXILIARY CREW2. FREOUENCY METER3. TRANSMITTER TUNINGUNITS~. STARTER CRANK EXTENSION5. HAND CRANKS6. CRANK EXTENSION FORBOMB DOORS AND FLAPS7. DOOR TO BALL TURRETCOMPARTMENTFigure 65 - Transmitter Tuning Units0KEY TO FIGURE 64I. LIAISONTRANSMITTER2. ANTENNA CHANGE-OVER SWITCH3. TRAILING ANTENNA REEL CONTROLFigure 64 - Radio Compartment - Left Side(3) Turn the "CIRCLE SIZE" control knob untilthe two circle traces on the indicator screen are adjustedto the required diameter for readings. Theproper size occurs when each circle is just visible asa luminous green ring on the gray background, justbeyond the outer circumference of its dark calibratedscale ring.(4) Turn the "RECEIVER GAIN" control to adjustthe lobe readings for clearest legibility on theindicator screen. Maximum receiver sensitivity maybe used at the higher altitudes and less than maximumsensitivity may be required at the lower altitudes.The receiver gain control must be adjusted in conjunctionwith the automatic volume control switch formaximum lobe legibility on the altimeter scale inaccordance with the following paragraphs.67