Why is the Airbus A320 permitted to carry 180 passengers, instead of the maximum 179 allowed?

Question

The EASA regulations give the following requirement for number of emergency exits:

If then the Airbus A320 is certified to carry 180 passengers, it seems to me that it falls just outside the minimum bracket of 2x Type I exits and 2x Type III exits and it should then have a pair of additional Type III exits to be able to accommodate 180 passengers.

However, various sources give the emergency exits as (link):

This configuration, in my opinion only allows 179 passengers, not 180.

Is there some clause I am missing?

Answer 1

See Page 9 of TCDS A.064 ANNEX - Airbus A318, A319, A320, A321 - Special Conditions

TCDS A.064 ANNEX - Airbus A318, A319, A320, A321 - Special Conditions

EQUIVALENT SAFETY FINDING         E-2107: Passenger Extension to 180
APPLICABILITY:                    A320
REQUIREMENTS:                     JAR 25.807
ADVISORY MATERIAL:                N/A

Statement of Issue:

An application was made on September 30, 1992 to JAA for certification of maximum number of passengers of 180.

Paragraph 25.807(c)(1) of JAR specifies for passenger seating configuration, the number and types of Emergency Exits for each side of the fuselage. The maximum seating capacity allowable under JAR 25.807(c)(1) for A320 exit configuration is 179 (2 Type I and 2 Type III).

However, the exits size for front and rear doors on the A320 is such (32x73 inches) that they are oversized Type I and therefore can be considered as a non standard exit arrangement.

The same exit size is being used on a derivative of the A320, for which Latin Square Tests have been conducted in order to establish an appropriate rating for that kind of exits. These tests have shown that, when associated with the performance of the slide installed at these exits, a rating of 55 passengers is appropriate.

It should also be noted that the full scale emergency evacuation demonstration of the A320 with 179 passengers has demonstrated compliance with JAR 25.803(c) with sufficient margin to justify 180 passengers.

Under those conditions, a maximum capacity of 180 passengers is requested for the A320.

JAA Conclusion: Based upon the demonstrated higher rating for the floor level exits and the adequate margins for 179 passengers shown in the 90 seconds demonstration, and used as a basis to show compliance to JAR 25.803(c), the JAA accept 180 passengers as the maximum capacity for the A320 on the basis of an Equivalent Safety Finding.

Answer 2

The table you posted is no more valid as per CS-25 Amendment 12 (PDF).

Now each Type I allows for 45 passengers and each Type III allows for 35.

Type and number required.

The maximum number of passenger seats permitted depends on the type and number of exits installed on each side of the fuselage. Except as further restricted in sub paragraphs(g)(1) through (g)(9) of this paragraph, the maximum number of passenger seats permitted for each exit of a specific type installed on each side of the fuselage is as follows:

TypeA  110
TypeB   75 
TypeC   55 
TypeI   45 
TypeII  40 
TypeIII 35 
TypeIV   9

The subparagraphs that apply to the A320:

(6) For a passenger seating configuration of more than 110 seats, the emergency exits on each side of the fuselage must include at least two Type I or larger exits.

(7) The combined maximum number of passenger seats permitted for all Type III exits is 70, and the combined maximum number of passenger seats permitted for two TypeIII exits on each side of the fuselage that are separated by fewer than three passenger seat rows is 65.