[1][2] A QRH is kept in the cockpit and can be consulted whenever the flight crew experiences in-flight problems.
The first QRHs in the 20th century were made out of paper, but in the 21st century, many pilots have switched to so-called electronic flight bags, which have the advantage of electronic search functions, but require electricity to work.
[3] Some modern aircraft such as the Airbus A330 have computerised some of the checklists, but other checklists cannot be properly programmed, because some problems cannot be correctly identified or diagnosed by aircraft computers; thus, the Quick Reference Handbook remains an essential in-flight tool for the crew.
[2] QRH includes various checklists for dealing with abnormal and emergency situations, based on the equipment and furnishings on the airplane.
[3] When designed and used correctly to address issues such as turbine engine failures or on-board fires, a QRH can prevent aviation accidents and incidents.