Another perspective - not PAYD but PAYF
17.21 Civilian Flight Observer's Allowance
An allowance for each hour in the air is to be paid to officers who are required to fly in an aircraft for the purpose of carrying out a particular task connected with the testing or trials of experimental, new, modified and repaired aircraft or equipment.
To receive the allowance an officer must be designated a Civilian Flight
Observer by the Head of Establishment or an officer not below Band C1 level or equivalent acting with his or her authority.
Positioning flights for the purpose of conducting tests from another airfield or site do not qualify for the allowance unless tests are carried out during such flights.
Prior approval of the Head of Establishment or the officer acting on his behalf is required for each flight or series of flights. The allowance will not be paid unless the flight clearly involves the performance of duties under difficult and exacting conditions, entailing a measure of increased personal responsibility.
Claims are to be submitted monthly to the paying officer on PPA Form 1941. The Certificate on the form is to be signed by an officer superior in rank to the claimant. The flying times for the month are to be aggregated and fractions of an hour paid as a full hour, e.g.. 12 flights with an aggregate flying time of eight hours and ten minutes count as nine hours.
The allowance may also be paid to members of the Photographer specialism
designated Civilian Flight Observers when engaged on flying duties involving
special features and extra personal responsibilities.