Subject: FUSELAGE DOORS AND 

HATCHES 

Date: 4/25/05 

Initiated By: ANM-115 

AC No: 25.783-1A 

Change: 

1. PURPOSE. This advisory circular (AC) describes an acceptable means for showing 

compliance with the requirements of § 25.783, “Fuselage doors,” and other applicable sections 

of Title 14, Code of Federal Regulations (CFR), part 25. Part 25 contains the airworthiness 

standards applicable to transport category airplanes. The means of compliance described in this 

document provides guidance to supplement the engineering and operational judgment that must 

form the basis of any compliance findings about the structural and functional safety standards for 

fuselage doors and their operating systems. 

2. APPLICABILITY. 

a. The guidance provided in this document is directed to airplane manufacturers, 

modifiers, foreign regulatory authorities, and Federal Aviation Administration transport airplane 

type certification engineers and their designees. 

b. Like all advisory circular material, this AC is not, in itself, mandatory, and does not 

constitute a regulation. It describes an acceptable means, but not the only means, for showing 

compliance with the requirements for transport category airplanes. The FAA will consider other 

methods of demonstrating compliance that an applicant may elect to present. While these 

guidelines are not mandatory, they are derived from extensive FAA and industry experience in 

determining compliance with the relevant regulations. On the other hand, if we become aware of 

circumstances that convince us that following this AC would not result in compliance with the 

applicable regulations, we will not be bound by the terms of this AC, and we may require 

additional substantiation or design changes as a basis for finding compliance. 

c. This material does not change, create any additional, authorize changes in, or permit 

deviations from, regulatory requirements. 

3. CANCELLATION. Advisory Circular 25.783-1, “Fuselage Doors, Hatches, and Exits,” 

dated 12/10/86, is canceled, but remains applicable for airplanes with older certification bases. 
AC 25.783-1A 4/25/05 

2 

4. RELATED DOCUMENTS. 

 a. Title 14, Code of Federal Regulations (14 CFR), part 25: 

Section Title

25.571 Damage-tolerance and fatigue evaluation of structure 

25.607 Fasteners 

25.703 Takeoff warning system 

25.783 Fuselage doors 

25.809 Emergency exit arrangement 

25.813 Emergency exit access 

 b. FAA Advisory Circulars (AC): 

AC No. Title Date

20-71 Dual Locking Devices on Fasteners 12/8/70 

25-17 Transport airplane Cabin Interiors 

Crashworthiness Handbook 

7/15/91 

5. DEFINITIONS. Inconsistent or inaccurate use of terms may lead to installing doors and 

hatches that do not fully meet the safety objectives of the regulations. To ensure that such 

installations fully comply with the regulations, the following definitions should be used when 

showing compliance with § 25.783. 

 a. Door includes all doors, hatches, openable windows, access panels, covers, etc., on the 

exterior of the fuselage that do not require the use of tools to open or close. This also includes 

each door or hatch through a pressure bulkhead, including any bulkhead that is specifically 

designed to function as a secondary bulkhead under the prescribed failure conditions of part 25. 

 b. Initial opening movement refers to that door movement, caused by operation of a 

handle or other door control mechanism, which is required to place the door in a position that is 

free of structure that would interfere with continued opening of the door. 

 c. Inward means having a directional component of movement that is in opposition to the 

mean (pressure) plane of the body cutout. 

 d. Closed means the door has been placed within the doorframe in such a position that the 

latches can be operated to the “latched” condition. Fully closed means the door is placed within 

the doorframe in the position it will occupy when the latches are in the latched condition. 
4/25/05 AC 25.783-1A 

3

 e. Latches are movable mechanical elements that, when engaged, prevent the door from 

opening. 

 f. Latched means the latches are fully engaged with their structural counterparts and held 

in position by the latch operating mechanism. 

 g. Latching system means the latch operating mechanism and the latches. 

 h. Locks are mechanical elements, in addition to the latch operating mechanism, that 

monitor the latch positions and, when engaged, prevent latches from becoming disengaged. 

i. Locked means the locks are fully engaged. 

j. Locking system means the lock operating mechanism and the locks. 

 k. Stops are fixed structural elements on the door and doorframe that, when in contact with 

each other, limit the directions in which the door is free to move. 

 l. Exit is a door designed to allow egress from the airplane. (Note that most exits are 

required to be emergency exits.) 

 m. Emergency exit is an exit designated for use in an emergency evacuation. 

 n. Flight refers to that period of time from the start of takeoff roll until the airplane comes 

to rest after landing. 

 o. Door operator’s station is the location(s) where the door closing, latching, and locking 

operations are performed. 

 p. Inadvertent action by persons means an act committed, whether deliberate or not, that 

has unintended consequences. 

6. BACKGROUND. 

 a. There is a history of incidents and accidents in which doors, fitted in pressurized 

airplanes, have opened inadvertently during pressurized and unpressurized flight. Some of these 

inadvertent openings have resulted in fatal accidents. After one fatal accident that occurred in 

1974, the FAA and industry representatives formed a design review team to examine the existing 

regulatory requirements for doors to determine if those regulations were adequate to ensure 

safety. The team’s review and eventual recommendations led to the FAA issuing Amendment 

25-54 to part 25 in 1980, which significantly improved the safety standards for doors installed on 

transport category airplanes. Included as part of Amendment 25-54 was § 25.783, “Doors,” 

which provides the airworthiness standards for doors installed on transport category airplanes. 
AC 25.783-1A 4/25/05 

4 

 b. Although there have been minor revisions to § 25.783 since Amendment 25-54, the 

safety standards for doors had remained essentially the same until we adopted Amendment 25-

114. Despite the improved standards established by Amendment 25-54, there have continued to 

be safety problems, especially for cargo doors. Cargo doors are often operated by people having 

little formal instruction in their operation. Sometimes the operator is required to carry out 

several actions in sequence to complete the door opening and closing operations. Failure to 

complete all actions in sequence during closure can have serious results. Service history shows 

that several incidents of doors opening during flight have been caused by the failure of the 

operator to complete the door closing, latching, and locking sequence. Other incidents have 

been attributable to incorrect adjustment of the door mechanism, or to failure of a vital part. 

 c. Experience also has shown that, in some cases, the flight deck indication system has not 

been reliable. In other instances, the door indication system performed correctly, but the 

flightcrew, for unknown reasons, was not alerted to the unsafe condition. A reliable indication 

of door status on the flight deck is particularly important on airplanes used in operations where 

the flightcrew does not have an independent means readily available to verify that the doors are 

properly secured. 

 d. On some airplanes, large cargo doors form part of the basic fuselage structure, so that, 

unless the door is properly closed, latched, and locked, the basic airframe structure is unable to 

carry the design aerodynamic and inertial loads. Large cargo doors also have the potential for 

creating control problems when an open door acts as an aerodynamic surface. In such cases, 

failure to secure the door properly could have catastrophic results, even when the airplane is 

unpressurized. 

 e. After two accidents occurred in 1989 due to the failure of cargo doors on transport 

category airplanes, the Air Transport Association (ATA) of America initiated another study of 

the door design and operational issues. The ATA finished its study in 1991 and made 

recommendations to the FAA for improving the design standards of doors. The FAA considered 

those recommendations, as well as other recommendations from the National Transportation 

Safety Board, in developing the improved standards for doors adopted by Amendment 25-114 on 

May 3, 2004 (69 FR 24496). 

7. CURRENT REQUIREMENTS - GENERAL. 

 a. Service history has shown that, to prevent doors from becoming a hazard by opening 

during flight, it is necessary to provide multiple layers of protection against failures, 

malfunctions, and human error. Section 25.783 addresses these multiple layers of protection by 

requiring: 

• a latching system 

• a locking system 
4/25/05 AC 25.783-1A 

5

• indication systems 

• a pressure prevention means 

 b. These features provide a high degree of tolerance to failures, malfunctions, and human 

error. Section 25.783 requires the latching system to be designed so that it is inherently or 

specifically restrained from being back-driven from the latches. Even so, the latches are 

designed to eliminate, as much as possible, all forces from the latch side that would tend to 

unlatch the latches. In addition to these features that prevent the latches from inadvertently 

opening, a separate locking system is required for doors that could be a hazard if they become 

unlatched. Despite these safety features, it could still be possible for the door operator to make 

errors in closing the door, or for mechanical failures to occur during or after closing. Therefore, 

an indicating system is required that will signal to the flightcrew if the door is not fully closed, 

latched, and locked. However, since it is still possible for the indication to be missed or 

unheeded, a separate system is required that prevents pressurization of the airplane to an unsafe 

level if the door is not fully closed, latched, and locked. 

 c. A discussion of acceptable compliance criteria is provided in paragraphs 8 through 15 of 

this AC. To make this AC easier to use, the applicable rule text and section reference is 

provided, followed by the compliance discussion. 

8. GENERAL DESIGN CONSIDERATIONS (§ 25.783(a)). 

 a. Each door must have means to safeguard against opening in flight as a result of 

mechanical failure, or failure of any single structural element. [§ 25.783(a)(1)]

 (1) The applicant should consider failures when safeguarding the door against opening 

due to mechanical failure or the failure of a single structural element. 

 (2) Such failures include those caused by: 

• wear 

• excessive backlash 

• excessive friction 

• jamming 

• incorrect assembly 

• incorrect adjustment 

• parts becoming loose, disconnected, or unfastened 

• parts breaking, fracturing, bending, or flexing beyond the extent intended. 
AC 25.783-1A 4/25/05 

6 

 b. Each door that could be a hazard if it unlatches must be designed so that unlatching 

during pressurized and unpressurized flight from the fully closed, latched, and locked 

condition is extremely improbable. This must be shown by safety analysis. [§ 25.783(a)(2)] 

 (1) All doors should incorporate features in the latching mechanism that provide a 

positive means to prevent the door from opening as a result of such things as: 

• vibrations 

• structural loads and deflections 

• positive and negative pressure loads, positive and negative “g” loads 

• aerodynamic loads 

 (2) The means should be effective throughout the approved operating envelope of the 

airplane, including the unpressurized portions of flight. 

 (3) The applicant may conduct the safety assessment required by this regulation by 

qualitative or quantitative analysis, or a combination, as appropriate to the design. In evaluating 

a failure condition that results in total failure or inadvertent opening of the door, the applicant 

should consider all contributing events, including: 

• failure of the door and door supporting structure 

• flexibility in structures and linkages 

• failure of the operating system 

• erroneous signals from the door indication systems 

• likely errors in operating and maintaining the door 

 c. Each element of each door operating system must be designed or, where impracticable, 

[distinctly] and permanently marked, to minimize the probability of incorrect assembly and 

adjustment that could result in a malfunction. [(§ 25.783(a)(3)].

 (1) Experience has shown that the level of protection against mechanical failure can be 

significantly improved by careful attention to detail design. Therefore, the applicant should take 

the following points into account: 

 (a) To minimize the risk of incorrect assembly and adjustment, parts should be 

designed to prevent incorrect assembly if, as a result of such incorrect assembly, door 

functioning would be adversely affected. “Adverse effects” could be such things as preventing 

or impeding the opening of the door during an emergency, or reducing the capability of the door 

to remain closed. If such designs are impracticable and marking is used instead, the marking 

should remain clearly identifiable during service. In this respect, markings could be made using 

material such as permanent ink, provided it is resistant to typical solvents, lubricants, and other 

materials used in normal maintenance operations. 
4/25/05 AC 25.783-1A 

7

 (b) To minimize the risk of the door operating mechanism being incorrectly 

adjusted in service, adjustment points that are intended for “in-service” use only should be 

clearly identified and limited to a minimum number consistent with adequate adjustment 

capability. Any points provided solely to facilitate adjustment at the initial build and not 

intended for subsequent use should be made non-adjustable after initial build, or should be 

highlighted in the maintenance manual as a part of the door mechanism that is not intended to be 

adjusted. 

 d. All sources of power that could initiate unlocking or unlatching of any door must be 

automatically isolated from the latching and locking systems prior to flight and it must not be 

possible to restore power to the door during flight. [§ 25.783(a)(4)].

 (1) For doors that use electrical, hydraulic, or pneumatic power to initiate unlocking or 

unlatching, those power sources must be automatically isolated from the latching and locking 

systems before flight. Additionally, it should not be possible to restore power to them during 

flight. 

 (2) It is particularly important for doors with powered latches or locks to have all power 

removed that could power these systems or that could energize control circuits to these systems 

in the event of electrical short circuits. This does not include power to the door indicating 

system, auxiliary securing devices (if installed), or other systems not related to door operation. 

Power to those systems should not be sufficient to cause unlocking or unlatching unless each 

failure condition that could result in energizing the latching and locking systems is extremely 

improbable. 

 e. Each removable bolt, screw, nut, pin, or other removable fastener must meet the 

locking requirements of § 25.607 [“Fasteners”]. (Note: Refer to FAA Advisory Circular 20-71, 

“Dual Locking Devices on Fasteners,” dated 12/8/70, for guidance on complying with § 25.607.) 

[§ 25.783(a)(5)] 

 f. Certain doors, as specified by § 25.807(h), must also meet the applicable requirements 

of §§ 25.809 through 25.812 for emergency exits. [§ 25.783(a)(6)]

9. OPENING BY PERSONS (§ 25.783(b). 

 a. There must be a means to safeguard each door against opening during flight due to 

inadvertent action by persons. 

 (1) The door should have inherent design features that achieve this objective. It is not 

considered acceptable to rely solely on cabin pressure to prevent inadvertent opening of doors 

during flight, because there have been instances where doors have opened during unpressurized 

flight, such as during landing. 
AC 25.783-1A 4/25/05 

8 

 (2) All doors should therefore incorporate features to prevent the door from being 

opened inadvertently by people on board the airplane, such as orienting the handle so that 

deliberate action is required to operate it. 

 b. In addition, design precautions must be taken to minimize the possibility for a person 

to open a door intentionally during flight. If these precautions include the use of auxiliary 

devices, those devices and their controlling systems must be designed so that--

• no single failure will prevent more than one exit from being opened 

[§ 25.783(b)(1)]; and 

• failures that would prevent opening of the exit after landing are improbable 

[§ 25.783(b)(2)].

 (1) The intentional opening of a door by people on board while the airplane is in flight 

should be considered. This rule is intended to protect the airplane and passengers, but not 

necessarily the person who intentionally tries to open the door. Suitable design precautions 

should therefore be taken; however, the precautions should not compromise the ability to open 

an emergency exit in an emergency evacuation. In this context, single failures include hardware 

failures as well as maintenance and logical (e.g., software) errors. Note that certain maintenance 

or logical errors may have the potential to affect more than one door. 

 (2) The applicant should consider the following precautions: 

 (a) Doors in pressurized compartments. It should not normally be possible to open 

the door when the compartment differential pressure is above 2 psi. The ability to open the door 

will depend on the door operating mechanism and the handle design, location, and operating 

force. Operating forces in excess of 300 pounds should be considered sufficient to prevent the 

door from being opened. During approach, takeoff, and landing, when compartment differential 

pressure is lower, intentional opening may be possible; however, these phases are brief and all 

passengers are expected to be seated with seat belts fastened. 

 (b) Doors that cannot meet the guidance of paragraph 9b(2)(a) of this AC, and 

Doors in non-pressurized airplanes. The use of auxiliary devices (for example, a speed-activated 

or barometrically-activated means) to safeguard the door from opening should be considered. 

The need for such auxiliary devices should depend upon the consequences to the airplane and 

other occupants if the door is opened in flight. 

 (c) Auxiliary devices installed on emergency exits. The failure of an auxiliary 

device should normally result in an unsecured position of the device. Failures of the device that 

would prevent opening of the exit after landing should be improbable. 

 (3) The opening of exits on the ground should also be considered in the design, relative 

to the effects of differential pressure. While it is desirable and required to be able to open exits 

under normal residual differential pressure, opening of the exit with significant differential 

pressure can be a hazard to the person opening the exit. Clearly, emergency conditions may 
4/25/05 AC 25.783-1A 

9

dictate that the exit be opened regardless of the differential pressure. Devices that restrict 

opening of the door, or affect the pressurization system, can have failure modes that create other 

safety concerns. However, the manufacturer should consider this issue in the design of the door 

and provide warnings where necessary, if it is possible to open a door under differential pressure 

that may be hazardous to the exit operator. Ideally, the door would be openable with the highest 

differential pressure that is safe for the operator, but no higher than that. 

10. PRESSURIZATION PREVENTION MEANS (§ 25.783(c)). 

 a. There must be a provision to prevent pressurization of the airplane to an unsafe level if 

any door subject to pressurization is not fully closed, latched, and locked. The provision must 

be designed to function after any single failure, or after any combination of failures not 

shown to be extremely improbable. [§ 25.783(c)(1)]

 (1) The provisions for preventing pressurization must monitor the closed, latched, and 

locked condition of the door. If more than one lock system is used, each lock system must be 

monitored. Examples of such provisions are vent panels and pressurization inhibiting circuits. 

Pressurization to an unsafe level is considered to be prevented when the compartment 

differential pressure is kept below 1/2 psi. These systems are not intended to function to 

depressurize the airplane once the fully closed, latched, and locked condition is established and 

pressurization is initiated. 

 (2) If a vent panel is used, it should be designed so that, in normal operation or with a 

single failure in the operating linkage, the vent panel cannot be closed until the door is latched 

and locked. The vent panel linkage should monitor the position of each door lock. 

 (3) If automatic control of the cabin pressurization system is used as a means to prevent 

pressurization, the control system should monitor each lock. Because inadvertent 

depressurization at altitude can be hazardous to the occupants, this control system should be 

considered in showing compliance with the applicable pressurization system reliability 

requirements. Normally, such systems should be automatically disconnected from the airplane’s 

pressurization system after the airplane is airborne, provided no prior unsafe condition was 

detected. 

 (4) It should not be possible to override the pressurization prevention system unless a 

procedure is defined in the Master Minimum Equipment List (MMEL) that confirms a fully 

closed, latched, and locked condition. In order to prevent the override procedure from becoming 

routine, the override condition should not be achievable by actions solely on the flight deck, and 

should be automatically reset at each door operational cycle. 

 b. Doors that meet the conditions described in paragraph [25.783] (h) are not required to 

have a dedicated pressurization prevention means if, from every possible position of the door, 

it will remain open to the extent that it prevents pressurization or safely close and latch as 

pressurization takes place. This must also be shown with each single failure and malfunction, 

except that [§ 25.783(c)(2)]-- 
AC 25.783-1A 4/25/05 

10 

• with failures or malfunctions in the latching mechanism, it need not latch after 

closing [§ 25.783(c)(2)(i)]; and

• with jamming as a result of mechanical failure or blocking debris, the door need 

not close and latch if it can be shown that the pressurization loads on the jammed 

door or mechanism would not result in an unsafe condition [§ 25.783(c)(2)(ii)].

 (1) As specified in § 25.783(d)(7), each door for which unlatching would not result in a 

hazard is not required to have a locking mechanism. Those doors also may not be required to 

have a dedicated pressurization prevention means. 

 (2) However, this should be determined by demonstrating that an unsafe level of 

pressurization cannot be achieved for each position that the door may take during closure, 

including those positions that may result from single failures or jams. 

 (a) Excluding jamming and excluding failures and malfunctions in the latching 

system, for every possible position of the door, it must either remain open to the extent that it 

prevents pressurization, or safely close and latch as pressurization takes place. 

 (b) With single failures of the latching system or malfunctions in the latching 

system the door may not necessarily be capable of latching, but it should either remain open to 

the extent that it prevents pressurization, or safely move to the closed position as pressurization 

takes place. 

 (c) With jamming as a result of mechanical failure in the latching system or 

blocking debris, the pressurization loads on the jammed door or mechanism may not result in 

damage to the door or airframe that could be detrimental to safe flight (both the immediate flight 

or future flights). In this regard, consideration should be given to jams or non-frangible debris 

that could hold the door open just enough to still allow pressurization, and then break loose in 

flight after full pressurization is reached. 

11. LATCHING AND LOCKING (§ 25.783(d)). 

 a. There must be a provision to latch each door. [§ 25.783(d)(1)]

 (1) The definitions of latches and locks are revised as of Amendment 25-114, 

particularly with regard to mechanical and structural elements of doors with an initial inward 

movement. In this regard, fixed stops are not considered latches. The movable elements that 

hold the door in position relative to the fixed stops are considered latches. These movable 

elements prevent the door from opening and will support some loads in certain flight conditions, 

particularly when the airplane is unpressurized. 
4/25/05 AC 25.783-1A 

11

 (2) For all doors, § 25.783(d)(2) requires that the latching system employ a securing 

means other than the locking system. The separate locking system may not be necessary for 

certain doors with an initial inward movement (see § 25.783(d)(4)). 

 b. The latches and their operating mechanism must be designed so that, under all 

airplane flight and ground loading conditions, with the door latched, there is no force or 

torque tending to unlatch the latches. In addition, the latching system must include a means 

to secure the latches in the latched position. This means must be independent of the locking 

system. [§ 25.783(d)(2)]

 (1) The latches of doors for which the initial opening movement is outward are 

typically subject to vibrations, structural loads and deflections, positive and negative pressure 

loads, positive and negative “g” loads, aerodynamic loads, etc. The latches of doors for which 

the initial opening movement is inward typically share some of these same types of loads with 

fixed stops. 

 (2) The design of the latch should be such that, with the latch disconnected from its 

operating mechanism, the net reaction forces on the latch should not tend to unlatch it during 

both pressurized and unpressurized flight throughout the approved flight envelope. The effects 

of possible friction in resisting the forces on the latch should be ignored when considering 

reaction forces tending to unlatch the door. The effects of distortion of the latch and 

corresponding structural attachments should be considered in this determination. Any latch 

element for which “g” loads could result in an unlatching force should be designed to minimize 

such forces. 

 (3) Even though the principal back-driving forces should be eliminated by design, it is 

recognized that there may still be ratcheting forces that could progressively move the latches to 

the unlatched position. Therefore, each latch should be positively secured in the latched position 

by its operating mechanism, which should be effective throughout the approved flight envelope. 

The location of the operating system securing means will depend on the rigidity of the system 

and the tendency for any forces (such as ratcheting) at one latch to unlatch other latches. 

 (4) Overcenter features in the latching mechanism are considered to be an acceptable 

securing means, provided that an effective retaining feature that functions automatically to 

prevent back-driving is incorporated. If the design of the latch is such that it could be subject to 

ratcheting loads that might tend to unlatch it, the securing means should be adequate to resist 

such loads. 

 (5) In those designs that use the latch to operate an electrical switch, any back-driving 

effect of the switch on the latch is permissible, provided the extent of any possible movement of 

the switch-- 

• is insufficient to unlatch it, and 
AC 25.783-1A 4/25/05 

12 

• will not result in the latch being subjected to any other force or torque tending 

to unlatch it. 

 (6) The latch securing means must be independent of the locking means. However, the 

latching and locking functions may be fulfilled by a single operating means, provided that it is 

not possible to back-drive the locks via the latch mechanism when the door is locked. 

 c. Each door subject to pressurization, and for which the initial opening movement is 

not inward, must [§ 25.783(d)(3)]--

• have an individual lock for each latch [§ 25.783(d)(3)(i)];

• have the lock located as close as practicable to the latch [§ 25.783(d)(3)(ii)]; and

• be designed so that, during pressurized flight, no single failure in the locking 

system would prevent the locks from restraining the latches necessary to secure 

the door [§ 25.783(d)(3)(iii)].

 (1) To safeguard doors subject to pressurization and for which the initial opening 

movement is not inward, each latch must have an individual lock. The lock should directly lock 

the latch. In this regard, the lock should be located directly at the latch to ensure that, in the 

event of a single failure in the latch operating mechanism, the lock would continue to restrain the 

latch in the latched position. Even in those cases where the lock cannot be located directly at the 

latch, the same objective should be achieved. In some cases, a pair of integrally-connected 

latches may be treated as a single latch with respect to the requirement for a lock, provided that: 

 (a) the lock reliably monitors the position of at least one of the load-carrying 

elements of the latch; and 

 (b) with any one latch element missing, the airplane can meet the full 

requirements of part 25 as they apply to the unfailed airplane; and 

 (c) with the pair disengaged, the airplane can achieve safe flight and landing, and 

meet the damage tolerance requirements of § 25.571 (“Damage-tolerance and fatigue evaluation 

of structure”). 

 (2) In some designs, more latches are provided than necessary to meet the minimum 

design requirements. The single failure requirement for the locking system is intended to ensure 

that the number and combination of latches necessary to secure the door will remain restrained 

by the locking mechanism. Only those latches needed to meet the minimum design requirements 

need to remain restrained after the single failure. 

 (3) In meeting this requirement, the indirect locking provided through the latch system 

by the locks at other latches may be considered. In this case, the locking system and the latching 

system between the locked latch and the unlocked latch should be designed to withstand the 

maximum design loads discussed in paragraph 11f of this AC, as appropriate to pressurized 

flight. 
4/25/05 AC 25.783-1A 

13

 d. Each door for which the initial opening movement is inward, and unlatching of the 

door could result in a hazard, must have a locking means to prevent the latches from 

becoming disengaged. The locking means must ensure sufficient latching to prevent opening 

of the door even with a single failure of the latching mechanism. [§ 25.783(d)(4)]

 (1) On these doors, the locking means should monitor the latch securing means, but 

need not directly monitor and lock each latch. Additionally, the locking means could be located 

such that all latches are locked by locking the latching mechanism. 

 (2) With any single failure in the latching mechanism, the means must still lock a 

sufficient number of latches to ensure that the door remains safely latched. 

 e. It must not be possible to position the lock in the locked position if the latch and the 

latching mechanism are not in the latched position. [§ 25.783(d)(5)]

 (1) The lock should be an effective monitor of the position of the latch such that, if any 

latch is unlatched, the complete locking system cannot be moved to the locked position. 

 (2) Although an overcenter feature may be an adequate means of securing the latching 

mechanism, it is not considered to be the locking means for the latches. 

 f. It must not be possible to unlatch the latches with the locks in the locked position. 

Locks must be designed to withstand the limit loads resulting from [§ 25.783(d)(6)]-- 

• the maximum operator effort when the latches are operated manually 

[§ 25.783(d)(6)(i)]; 

• the powered latch actuators, if installed [§ 25.783(d)(6)(ii)]; and 

• the relative motion between the latch and the structural counterpart 

[§ 25.783(d)(6)(iii)].

 (1) Although the locks are not the primary means of keeping the latches engaged, they 

must have sufficient strength to withstand any loads likely to be imposed during all approved 

modes of door operation. 

 (2) The operating handle loads on manually-operated doors should be based on a 

rational human factors evaluation. However, handle forces in excess of 300 pounds need not be 

considered. 

 (3) The loads imposed by the normal powered latch actuators are generally predictable; 

however, loads imposed by alternate drive systems are not. For this reason, the locks should 

have sufficient strength to react to the stall forces of the latch drive system. 

 (4) Load-limiting devices should be installed in any alternative drive system for the 

latches in order to protect the latches and the locks from overload conditions. 
AC 25.783-1A 4/25/05 

14 

 (5) If the design of the latch is such that it could be subject to ratcheting loads that 

might tend to unlatch it, the locks should be adequate to resist such loads with the latch operating 

system disconnected from the latch. 

 g. Each door for which unlatching would not result in a hazard is not required to have a 

locking mechanism. [§ 25.783(d)(7)] (See paragraph 15 of this AC for a description of doors 

for which unlatching is considered not to result in a safety hazard.) 

12. WARNING, CAUTION, AND ADVISORY INDICATIONS (§ 25.783(e)). 

 a. There must be a positive means to indicate at each door operator’s station that all 

required operations to close, latch, and lock the door(s) have been completed. [§ 25.783(e)(1)]

 (1) To minimize the probability of incomplete door operations, it should be possible to 

perform all operations for each door at one station. If there is more than one operator’s station 

for a single door, appropriate indications should be provided at each station. 

 (2) The positive means to indicate at the door operator’s station that all required 

operations have been completed are such things as final handle positions or indicating lights. 

 b. There must be a positive means clearly visible from each operator station for any door 

that could be a hazard if unlatched to indicate if the door is not fully closed, latched, and 

locked. [§ 25.783(e)(2)]

 (1) A single indication that directly monitors the door in the closed, latched, and 

locked conditions should be provided, unless the door operator has a visual indication that the 

door is fully closed, latched, and locked. This indication should be obvious to the door operator. 

 (2) For example, a vent door or indicator light that monitors the door locks and is 

located at the door operator’s station may be sufficient. 

 (3) For doors that are remotely operated, the design of the door itself may need to 

address this requirement. For example, the position of the door may be difficult to ascertain 

from the operator’ station such that it is not obvious whether the door is in the closed position, or 

just close to it. In this case, it will likely be necessary to provide a feature either that prevents 

closing of the door if the latches are in the latched position, or prevents the latches from being 

moved unless the door is in the closed position. For doors that are manually operated, or where 

the position of the door is obviously not closed (e.g., held open by the latches in their latched 

position), such provisions would not be necessary to satisfy the requirement. For example, a 

passenger door with “shoot bolts” that extend to prevent the door from being closed any 

significant amount would typically not need such features to satisfy the requirement. 

 c. There must be a visual means on the flight deck to signal the pilots if any door is not 

fully closed, latched, and locked. The means must be designed such that any failure or 
4/25/05 AC 25.783-1A 

15

combination of failures that would result in an erroneous closed, latched, and locked 

indication is improbable for [§ 25.783(e)(3)]--

• each door that is subject to pressurization and for which the initial opening 

movement is not inward [§ 25.783(e)(3)(i)]; or

• each door that could be a hazard if unlatched [§ 25.783(e)(3)(ii)].

 (1) The visual means may be a simple amber light or it may need to be a red warning 

light tied to the master warning system, depending on the criticality of the door. 

 (2) The door closed, latched, and locked functions must be monitored, but only one 

indicator is needed to signal that the door is in the closed, latched, and locked condition. 

 (3) Indications should be reliable to ensure that they remain credible. The probability 

of erroneous closed, latched, and locked indication must be no greater than 10-5 for-- 

• each door subject to pressurization and for which the initial opening movement 

is not inward; and 

• each door that could be a hazard if unlatched. 

 d. There must be an aural warning to the pilots prior to or during the initial portion of 

takeoff roll if any door is not fully closed, latched, and locked, and its opening would prevent a 

safe takeoff and return to landing. [§ 25.783(e)(4)]

 (1) Where an unlatched door could open and prevent a safe takeoff and return to 

landing, a more conspicuous aural warning is needed in addition to the visual indication. This 

system should function in a manner similar to the takeoff configuration warning systems 

required by § 25.703 (“Takeoff warning system”). The visual display for these doors may be 

either a red light or a display on the master warning system. 

 (2) Examples of doors requiring these aural warnings include-- 

• doors for which the structural integrity of the fuselage would be compromised 

if the door is not fully closed, latched, and locked; or 

• doors that, if open, would prevent rotation or interfere with controllability to an 

unacceptable level. 
AC 25.783-1A 4/25/05 

16 

13. VISUAL INSPECTION PROVISION (§ 25.783(f)). 

 a. Each door for which unlatching of the door could be a hazard must have a provision 

for direct visual inspection to determine, without ambiguity, if the door is fully closed, latched, 

and locked. The provision must be permanent and discernible under operational lighting 

conditions, or by means of a flashlight or equivalent light source. 

 (1) A provision is necessary for direct visual inspection of the closed position of the 

door and the status of each of the latches and locks. This is because dispatch of an airplane may 

be permitted in some circumstances when a flight deck or other remote indication of an unsafe 

door remains after all door closing, latching, and locking operations have been completed. In 

this case, because the visual indication is used to determine whether to permit flight with a 

remote indication of an unsafe door, the visual indication should have a higher level of integrity 

than, and be independent of, the remote indication. 

 (2) The provisions should: 

 (a) Allow direct viewing of the position of the locks to show, without ambiguity, 

whether or not each latch is latched and each lock is in the locked position. For doors that do not 

have a lock for each latch, direct viewing of the position of the latches, and potentially the 

restraining mechanism, may be necessary for determining that all the latches are latched. 

Indirect viewing, such as by optical devices or indicator flags, may be acceptable, provided that 

there is no failure mode that could allow a false latched or locked indication. 

 (b) Preclude false indication of the status of the latches and locks as a result of 

changes in the viewing angle. The status should be obvious without the need for any deductive 

processes by the person making the assessment. 

 (c) Be of a robust design so that, following correct rigging, no unscheduled 

adjustment is required. Furthermore, the design should be resistant to unauthorized adjustment. 

 (d) Preclude mis-assembly that could result in a false latched and locked 

indication. 

 (3) If markings are used to assist the identification of the status of the latches and 

locks, such markings must include permanent physical features to ensure that the markings will 

remain accurately positioned. 

 (4) Although the visual means should be unambiguous in itself, placards and 

instructions may be necessary to interpret the status of the latches and locks. 

 (5) If optical devices or windows are used to view the latches and locks, it should be 

demonstrated that they provide a clear view and are not subject to fogging, being obstructed 

from dislodged material, or giving a false indication of the position of each latch and lock. Such 
4/25/05 AC 25.783-1A 

17

optical devices and window materials should be resistant to scratching, crazing, and any other 

damage from all materials and fluids commonly used in the operation and cleaning of airplanes. 

14. CERTAIN MAINTENANCE DOORS, REMOVABLE EMERGENCY EXITS, AND 

ACCESS PANELS (§ 25.783(g)). 

 a. Some doors not normally opened except for maintenance purposes or emergency 

evacuation and some access panels need not comply with certain paragraphs of this section as 

follows: 

• Access panels that are not subject to cabin pressurization and would not be a 

hazard if open during flight need not comply with paragraphs [25.783](a) through 

[25.783](f), but must have a means to prevent inadvertent opening during flight. 

[§ 25.783(g)(1)]

• Inward-opening removable emergency exits that are not normally removed, except 

for maintenance purposes or emergency evacuation, and flight deck-openable 

windows need not comply with paragraphs [25.783](c) and [25.783](f). 

[§ 25.783(g)(2)]

• Maintenance doors that meet the conditions of paragraph [25.783](h), and for 

which a placard is provided limiting use to maintenance access, need not comply 

with paragraphs [25.783](c) and [25.783](f). [§ 25.783(g)(3)]

 b. Panels (doors) permitting access to auxiliary power units (APU) would typically satisfy 

more than one of the criteria noted above. For example, they are located in non-pressurized 

portions of the fuselage, require a maintenance action to operate and would not be a hazard to the 

airplane if left open. The typical APU access would also provide obvious indication that it was 

not closed. Therefore, in the vast majority of cases, APU access panels or doors would only 

have to provide means to prevent inadvertent opening during flight. Nonetheless, such access 

panels or doors would be covered by other provisions in the rule if they were not able to satisfy 

the conditions noted above. 

15. DOORS THAT ARE NOT A HAZARD (§ 25.783(h)). 

 a. Section 25.783(h) describes those attributes that are essential before a door in the 

unlatched condition can be considered not to be a hazard during flight. Section 25.783 in general 

also recognizes four categories of doors: 

• Doors whose initial opening is not inward, and are presumed to be hazardous if they 

become unlatched. 

• Doors whose initial opening is inward, and could be a hazard if they become 

unlatched. 

• Doors whose initial opening is inward, and would not be a hazard if they become 

unlatched. 
AC 25.783-1A 4/25/05 

18 

• Small access panels outside pressurized compartments whose opening is of little or 

no consequence to safety. 

 b. The requirements for doors “that are not a hazard” are self-explanatory and are restated 

as follows: 

For the purposes of [§25.783(h)], a door is considered not to be a hazard in the 

unlatched condition during flight, provided it can be shown to meet all of the 

following conditions: 

 

 (1) Doors in pressurized compartments would remain in the fully closed 

position if not restrained by the latches when subject to a [differential] 

pressure greater than 1/2 psi. Opening by persons, either inadvertently or 

intentionally, need not be considered in making this determination. 

[§ 25.783(h)(1)]

 (2) The door would remain inside the airplane or remain attached to the 

airplane if it opens either in pressurized or unpressurized portions of the 

flight. This determination must include the consideration of inadvertent and 

intentional opening by persons during either pressurized or unpressurized 

portions of the flight. [§ 25.783(h)(2)]. 

 (3) The disengagement of the latches during flight would not allow 

depressurization of the cabin to an unsafe level. This safety assessment must 

include the physiological effects on the occupant. [§ 25.783(h)(3)]

 (4) The open door during flight would not create aerodynamic interference 

that could preclude safe flight and landing. [§ 25.783(h)(4)]

 (5) The airplane would meet the structural design requirements with the 

door open. This assessment must include the aeroelastic stability requirements 

of § 25.629, as well as the strength requirements of this subpart. 

[§ 25.783(h)(5)].

 (6) The unlatching or opening of the door must not preclude safe flight and 

landing as a result of interaction with other systems or structures. 

[§ 25.783(h)(6)]

16. STRUCTURAL REQUIREMENTS. 

 a. The door structure, including its mechanical features (such as hinges, stops, and latches) 

that can be subjected to airframe loading conditions, must be designed either to the damagetolerance requirements of § 25.571 (Amendment 25-45 or later), or to the earlier fail-safe 

requirements, depending on the certification basis of the airplane. Since applicants may elect to 
4/25/05 AC 25.783-1A 

19

voluntarily comply with Amendment 25-114, the earlier certification bases are relevant with 

regard to § 25.571. 

 b. In assessing the extent of damage under §§ 25.571 and 25.783, the applicant should give 

consideration to single element failures in the primary door structure, such as: 

• frames 

• stringers 

• intercostals 

• latches 

• hinges 

• stops 

• stop supports 

 c. The skin panels on doors that must comply with § 25.571, Amendment 25-45 or later, 

should be designed to be damage-tolerant, with a high probability of detecting any crack before 

the crack causes door failure or cabin depressurization. The obvious partial failure criteria or the 

damage-tolerance criteria may be used for the design of skin panels on doors with an earlier 

certification basis. 

 /s/ 

Ali Bahrami 

Manager, Transport Airplane Directorate 

Aircraft Certification Service