Aviation Safety Advisory A18W0129-D1-A1

Cessna 206 emergency exit – Blocked double cargo door with flaps extended

Place du Centre
200 Promenade du Portage, 4th Floor
Gatineau QC  K1A 1K8

18 February 2019

Aviation Safety Advisory A18W0129-D1-A1
Related occurrence: A18W0129

Letter addressed to Civil Aviation, Transport Canada

Subject: Aviation safety advisory A18W0129-D1-A1 – Cessna 206 emergency exit – Blocked double cargo door with flaps extended

The following safety advisory is to bring to your attention a significant safety issue involving Cessna 206 series aircraft that are fitted with double cargo doors.

On 16 August 2018, a Simpson Air float-equipped Cessna U206G aircraft (registration C-FNEQ) was conducting a sightseeing flight from Fort Simpson Airport (CYFS), Northwest Territories, to Virginia Falls, Northwest Territories, and Little Doctor Lake, Northwest Territories, with 1 pilot and 4 passengers on board. While landing at Little Doctor Lake, control of the aircraft was lost during the initial landing phase and the right wing contacted the surface of the lake. The aircraft subsequently nosed over and came to rest inverted and partially submerged. The pilot and 1 passenger were able to escape the submerged fuselage and climb up onto the floats; they were rescued by a nearby boater within 15 minutes. The 3 remaining occupants were unable to exit the aircraft and drowned; they were found inside the cabin with their seatbelts undone. All doors were found in the closed and locked position. The wing flaps were in the 20° down position, which blocked the forward portion of the rear cargo door. The investigation into this accident (A18W0129) is ongoing.

All occupants had been wearing lap belts; shoulder harnesses were available to the pilot and front-seat passenger but it is unknown if they were used on this flight. The impact forces were well within the range of human survivability and none of the occupants received immobilizing injuries. The pilot and surviving passenger exited through the window of the front left-side door. The pilot subsequently dove to assist the remaining passengers, but was unable to open the doors from outside the aircraft because they were locked from the inside. The investigation was unable to determine what egress action, if any, was taken by the passengers who were unable to exit the aircraft.

C-FNEQ and all variants of the Cessna 206 are certified based on Part 3 of the U.S. Civil Air Regulations except for the 206H, which is certified based on U.S. Federal Aviation Regulation (FAR) 23.  Section 3.387 of the Civil Air Regulations and section 23.807 of the FARs identify that emergency exits must be clear and unobstructed, easy to use, and simple and obvious to operate (Appendix A).

Cessna U206, TU206, and 206H incorporate recessed lever-type exterior door handles and a conventional L-shaped interior door handle on the front pilot's door. A C-shaped handle is used on the forward half of the double cargo door. To open all doors from the inside, the door handle must be lifted from the forward or LOCKED position (normal for flight), rotating up through the middle or CLOSE position, to the aft or OPEN position and then pushing outward on the door. To open the rear half of the double cargo door it is necessary to manipulate the handle found on the front edge of the door. Rotating the handle forward and down releases the catches at the top and bottom of the door.

Operation of the double cargo door is further complicated when the flaps are deployed (Figure 1). In that configuration, the forward half of the door can only be opened approximately 8 cm before coming into contact with the flap. The procedure to open the door with the flaps down is listed on a placard above the double cargo door (Figure 2).

Figure 1. Right side of C-FNEQ showing the flap position relative to the rear double cargo door. The rear half of the cargo door and the pilot door opened during aircraft recovery.
Right side of C-FNEQ showing the flap position relative to the rear double cargo door

A post-accident examination determined that the cabin door handles were placarded as required (Figure 2). The doors and door frames were not damaged or distorted during the accident sequence. All doors and latches functioned normally.

Figure 2. Placard located above the handle on the double cargo door on the occurrence aircraft.
Placard located above the handle on the double cargo door on the occurrence aircraft

Prior to this occurrence, since 1989, 5 accidents have occurred in the United States and Canada in which extended flaps blocked the rear double door. Those accidents resulted in 8 fatalities (Appendix B).

On 22 March 1991, Cessna produced Service Bulletin SEB91-4,Footnote 1 which called for the incorporation of a spring assembly that would automatically retract the handle on the rear half of the cargo door to facilitate getting the rear half of the door past the front half of the cargo door. The Service Bulletin also called for the installation of luminescent placards to indicate the location of the door handle and provide instructions on how to operate it. On 16 October 1997, Transport Canada (TC) issued Service Difficulty Alert AL-97-04,Footnote 2 which strongly recommended that owners and operators incorporate Service Bulletin SEB91-4 if they had not already done so. Although incorporating the service bulletin simplifies the procedure to open the double cargo door, it does not eliminate the jamming of the forward half of the cargo door against the flaps. Service Bulletin SEB91-4 had not been incorporated on the occurrence aircraft, nor was it mandatory under the Canadian Aviation Regulations.

In 1998, the Cessna Aircraft Company began producing the Cessna 206 after a 12-year hiatus. The new Cessna 206H model was essentially the same airframe as the U206G, which had been produced up until 1986. The difference between the two models lay mainly in the power plant and the avionics. In addition, Service Bulletin SEB91- 4 was incorporated into the new door design along with a number of other modifications to the cargo door handle size, location and placarding.

Shortly after production resumed, Cessna submitted an application for a Canadian type certificate. The previous Cessna 206 had been accepted based on the U.S. Federal Aviation Administration (FAA)'s type certificate. However, by 1998, TC's policy had changed and it no longer accepted applications for Canadian type certificates simply based on FAA type certificates. During the certification process, TC determined that the new Cessna 206H did not meet the requirements of section 23.807 of the FARs, and TC engineering determined that the rear double cargo door could not be considered an emergency exit because it was not readily accessible and the opening was not simple and obvious. However, TC did certify the aircraft with a limit of 5 occupants.

Between 1999 and 2003, TC, the FAA, and Cessna worked together in an effort to come up with a design change that could be applied to the 206H and could also be used to retrofit the previous 206 fleet. However, the matter was dropped as no acceptable solution was found. This left the Cessna 206H with a 5-occupant limit and the Cessna U206G and previous Cessna 206 aircraft with a 6-occupant limit.

By 2005, TC determined that some form of action was warranted to address the discrepancy in the number of certified seats in the various models of Cessna 206 aircraft—if only for floatplane operations—given the similarity of the double cargo door design. An Airworthiness Directive (AD) was proposed to limit all models of Cessna 206 aircraft on floats to 5 passengers. After consultation with industry, a decision was made in June 2006 to put the AD on hold until the results of the study undertaken on egress from submerged floatplanes were available. The results of the study were available by August 2006.  Ultimately, TC decided to leave the 5-occupant limit on the 206H model. No further action was taken in regards to earlier Cessna 206 series aircraft or to modifying the double cargo door. Results of the studies indicated there were no suitable design changes that could feasibly be applied to the entire Cessna 206 fleet. By May 2008, the file was put on hold due to other priorities and the absence of a clear way forward.

There are currently 190 Cessna U206 aircraft, 50 Cessna TU206 aircraft, and 11 Cessna 206H aircraft being operated in Canada, in both private and commercial service.

The defences that are currently in place to facilitate occupant escape from submerged Cessna 206 series aircraft, or other time-critical egress situations (e.g., post-impact fire), include the use of available restraint systems to reduce impact injuries and pre-flight safety briefings to better prepare occupants for emergency egress.

As shown in this occurrence, without functional exits, the time required to exit the aircraft may increase, which in turn increases the risk of death in time-critical situations, such as when the aircraft is submerged or there is a post-impact fire.

The risks resulting from delayed egress from the aircraft remain high, and more defences are needed to mitigate this hazard. TC may wish to reassess the suitability of the rear double cargo door as an emergency exit, as described in certification requirements for all Cessna 206 series aircraft.

The TSB would appreciate being advised of any action that is taken in this regard. Upon completion of investigation (A18W0129), the Board will release its investigation report into this occurrence.

Original signed by

Natacha Van Themsche
Director of Investigations – Air

Cc.

  • Federal Aviation Administration
  • National Transportation Safety Board
  • Textron Aviation Inc.

Appendix A – Excerpts from U.S. Civil Air Regulations and U.S. Federal Aviation Regulations

Section 3.387 of the U.S. Civil Air Regulations states the following:

Exits. (a)  Closed cabins on airplanes carrying more than 5 persons shall be provided with emergency exits consisting of movable windows or panels or of additional external doors which provide a clear and unobstructed opening, the minimum dimensions of which shall be such that a 19-by-26-inch ellipse may be completely inscribed therein. The exits shall be readily accessible, shall not require exceptional agility of a person using them, and shall be distributed so as to facilitate egress without crowding in all probable attitudes resulting from a crash. The method of opening shall be simple and obvious, and the exits shall be so arranged and marked as to be readily located and operated even in darkness […].

Section 23.807 (Amendment 23-10) of the U.S. Federal Aviation Regulations states the following:

[…]

  1. Type and operation. Emergency exits must be movable windows, panels, or external doors […], that provide a clear and unobstructed opening large enough to admit a 19-by-26-inch ellipse. […] In addition, each emergency exit must--
    1. Be readily accessible, requiring no exceptional agility to be used in emergencies;
    2. Have a method of opening that is simple and obvious;
    3. Be arranged and marked for easy location and operation, even in darkness; […]

Appendix B – Previous occurrences

On 29 July 1989, at Keefer Lake, Ontario, a passenger of a Cessna TU206G, who had originally been seated in the right front seat, was found drowned at the rear of the aircraft after the aircraft became inverted during a landing accident. (TSB aviation occurrence A89O0369)

On 20 July 1996, at Rivière des Prairies, Quebec, a Cessna U206F capsized on takeoff. The pilot and 3 passengers drowned in the rear of the aircraft as the pilot tried to open the rear cargo doors. (TSB Aviation Investigation Report A96Q0114)

On 01 June 1997, at Carroll Lake, Ontario, a Cessna TU206G capsized on landing after touching down with the wheels extended on the amphibious floats. Two passengers were unable to exit the aircraft and drowned. (TSB aviation occurrence A97C0090)

On 28 June 2003, at Lac Lemoine, Quebec, Cessna U206F flipped over during landing. Contrary to instructions provided by the pilot, the passenger made his way to the rear of the aircraft, was unable to exit the aircraft, and drowned. (TSB aviation occurrence A03Q0083)

On 10 July 2012, at Beluga Lake, Homer, Alaska, United States, a Cessna U206G capsized on landing. The accident was sufficiently violent that the airframe was deformed to the point that the pilot's door was jammed. The pilot and 3 of the 4 passengers managed to bend the forward half of the cargo door enough to squeeze through a small space. The remaining passenger drowned, but autopsy showed that blunt force trauma injuries rendered the passenger incapable of using the exit. (U.S. National Transportation Safety Board [NTSB] Identification: ANC12FA073)

Background information

This safety communication no.: A18W0129-D1-A1

Occurrence No.

A18W0129

Contact

Gerrit Vermeer, Regional Senior Investigator - Operations, Western Regional Office, Edmonton

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