Part 135, yes. Part 91, no.
I take back the word required and insert the following from AC 91-78
6. REMOVAL OF PAPER FROM THE COCKPIT FOR OPERATIONS UNDER PART 91.
a.
[FONT=Times New Roman,Times New Roman][FONT=Times New Roman,Times New Roman]EFBs/ECDs can be used during all phases of flight operations in lieu of paper reference material when the information displayed meets the following criteria:
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(1)
[FONT=Times New Roman,Times New Roman][FONT=Times New Roman,Times New Roman]The components or systems onboard the aircraft which display precomposed or interactive information are the functional equivalent of the paper reference material.
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(2)
[FONT=Times New Roman,Times New Roman][FONT=Times New Roman,Times New Roman]The interactive or precomposed information being used for navigation or performance planning is current, up-to-date, and valid.
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NOTE: Supporting reference material such as legends, glossaries, abbreviations, and other information is available to the pilot but is not required in the cockpit during operation.
b.
[FONT=Times New Roman,Times New Roman][FONT=Times New Roman,Times New Roman]The in-flight use of an EFB/ECD in lieu of paper reference material is the decision of the aircraft operator and the pilot in command. Any Type A or Type B EFB application, as defined in AC 120-76A may be substituted for the paper equivalent. It requires no formal operational approval as long as the guidelines of this AC are followed.
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c.
[FONT=Times New Roman,Times New Roman][FONT=Times New Roman,Times New Roman]It is suggested that a secondary or back up source of aeronautical information necessary for the flight be available to the pilot in the aircraft. The secondary or backup information may be either traditional paper-based material or displayed electronically.
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