Here is the US regulation that covers the amount of Flight Attendents required….
§ 121.391 Flight attendants
(a) Each certificate holder shall provide at least the following flight attendants on each passenger-carrying airplane used:
(1) For airplanes having a maximum payload capacity of more than 7,500 pounds and having a seating capacity of more than 9 but less than 51 passengers—one flight attendant.
(2) For airplanes having a maximum payload capacity of 7,500 pounds or less and having a seating capacity of more than 19 but less than 51 passengers—one flight attendant.
(3) For airplanes having a seating capacity of more than 50 but less than 101 passengers—two flight attendants.
(4) For airplanes having a seating capacity of more than 100 passengers—two flight attendants plus one additional flight attendant for each unit (or part of a unit) of 50 passenger seats above a seating capacity of 100 passengers.
(b) If, in conducting the emergency evacuation demonstration required under §121.291 (a) or (b), the certificate holder used more flight attendants than is required under paragraph (a) of this section for the maximum seating capacity of the airplane used in the demonstration, he may not, thereafter, take off that airplane—
(1) In its maximum seating capacity configuration with fewer flight attendants than the number used during the emergency evacuation demonstration; or
(2) In any reduced seating capacity configuration with fewer flight attendants than the number required by paragraph (a) of this section for that seating capacity plus the number of flight attendants used during the emergency evacuation demonstration that were in excess of those required under paragraph (a) of this section.
(c) The number of flight attendants approved under paragraphs (a) and (b) of this section are set forth in the certificate holder’s operations specifications.
(d) During takeoff and landing, flight attendants required by this section shall be located as near as practicable to required floor level exists and shall be uniformly distributed throughout the airplane in order to provide the most effective egress of passengers in event of an emergency evacuation. During taxi, flight attendants required by this section must remain at their duty stations with safety belts and shoulder harnesses fastened except to perform duties related to the safety of the airplane and its occupants.
The rules in Canada are different and I would love it if one of our colleagues from there could clarify: Is it one FA for every 40 PASSENGERS (not seats), and is there an exception for 50-seat aircraft? (One FA on a 50-seater…) Also, using the 747 example from above, if there were only 80 passengers on a 450-seat aircraft, could you utilize only 2 Flight Attendants? (Since your rules go by the PAX not the SEATS)
Good questions! I know you and I discussed this on the other board, but I wanted to add it here as well to see if the information generated any other opinions or comments…
The Canadian regulation requires, in part, that there be one flight attendant for every 40 passengers or portion thereof on board the aircraft.
Of course, no rule would be complete without exceptions. The aircraft must be staffed in accordance with the air carrier emergency procedures and when there is more than one deck, there must be a sufficient number of flight attendants to meet both the 1:40 rule and the emergency procedures.
CAR 705.104 ~ Flight Attendant Requirements (http://www.tc.gc.ca/aviation/regserv/carac/CARS/cars/705e.htm#705_104)
As for the 50 seat exception, yes we also have one of those. Where the aeroplane has met the emergency evacuation demonstration requirements of section 525.803 of the Airworthiness Manual or equivalent, using no more than one flight attendant for the compliance test and has been approved by Transport Canada Civil Aviation, Aircraft Certification, it may be operated with one flight attendant provided:
(a) the aeroplane is configured for 50 or less passenger seats;
(b) the aeroplane has been type certificated to FAR 25, Amendment 25-51 or later;
(c) subject to subsection (3), the passenger address system or the crew member interphone system at the approved flight attendant take-off and landing station referred to in paragraph (e) is serviceable;
(d) emergency and normal procedures in the flight attendant manual clearly reflect the differences when one flight attendant is carried and when more than one flight attendant is carried; and
(e) the flight attendant is assigned to occupy the approved flight attendant take-off and landing station located near a floor level exit.
Currently, only the DHC-8-300, ATR 42-300 and the CL 600-2B19 (CRJ) meet these requirements.
Standard 725.104 ~ Flight Attendant Requirements (http://www.tc.gc.ca/aviation/regserv/carac/CARS/cars/725e.htm#725_104)
As for the minimum staffing on board the aircraft, like in your B747 example, our requirements for flight attendant stations requires a minimum number of flight attendants on board the aircraft based on the number of floor level exits. Basically, no two opposite and no two adjacent floor level exits shall be unassigned.
CAR 705.41 ~ Flight Attendant Stations (http://www.tc.gc.ca/aviation/regserv/carac/CARS/cars/705e.htm#705_41)
Standard 725.41 ~ Flight Attendant Stations (http://www.tc.gc.ca/aviation/regserv/carac/CARS/cars/725e.htm#725_41)
On the B747-400, that would result in a minimum of 7 flight attendants required where there was only 1 passenger on board. Why 7? One would be required on the upper deck, one at doors 1, 2, 4 and 5 and two at door 3, as per the certification requirements of the aircraft type.