N828KT

On June 18, 2002, about 1330 Alaska daylight time, a passenger in a Piper PA-31-350 twin-engine airplane, N828KT, became incapacitated during a sightseeing flight over Denali National Park, about 50 miles north-northwest of Talkeetna, Alaska. The airplane was being operated by K2 Aviation, Talkeetna, Alaska, under Title 14, CFR Part 135, as a sightseeing flight in visual flight conditions at 21,000 feet, when the incident occurred. The airline transport certificated pilot and the seven other passengers were not injured. An IFR flight plan was filed, and company VFR flight following procedures were in effect. The flight originated at the Talkeetna Airport about 1300.

During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), on August 1, 2002, an airworthiness inspector with the Federal Aviation Administration (FAA), Anchorage Flight Standards District Office (FSDO), reported that he received a telephone call from the son of a passenger on the flight. The son related that he and his mother were on the sightseeing flight over the Mt. McKinley area. About 30 minutes after departure, while the airplane was flying at 21,000 feet, the mother of the caller became unresponsive. All passengers were utilizing supplemental oxygen delivered from the airplane's oxygen system. The pilot was informed of the situation, and he immediately returned to Talkeetna. The female passenger was met by emergency medical personnel, and was transported to a hospital in Palmer, Alaska.

During a telephone conversation with the NTSB IIC on August 19, 2002, the son of the passenger indicated that the passengers received a briefing from the pilot. The oxygen system was explained, including the need for all passengers to plug their oxygen mask into the airplane oxygen port, and to verify oxygen was flowing into each oxygen mask by the confirmation of a visible green band contained in the oxygen mask tubing. After takeoff, the flight proceeded over numerous glaciers. The pilot then had everyone put on their oxygen mask. Shortly after putting on her mask, the passenger was observed by her son to take some type of medication pill from her purse. The son inquired if the passenger was feeling O.K., and she responded, "yes." The son checked his mother's oxygen mask and it appeared to fit around her nose. The flight proceeded toward the summit of Mt. McKinley. The passenger later recalled seeing climbers on the mountain. She was initially taking pictures, but handed her camera to her son, saying she wanted to lay back and relax. The son inquired whether his mother was feeling sick, but she responded with a thumbs-up gesture and said she was O.K. She laid her head back in the seat and closed her eyes. The son again checked her oxygen mask. About five minutes later, the passenger was unresponsive to her son's questions. He estimated that his mother's incapacitation was about 30 minutes after takeoff, and about 10 minutes after beginning the use of oxygen.

The son of the passenger reported that the pilot was informed of the incapacitation and he began a descent toward Talkeetna. The son said he held his mother's head to maintain an open airway, and noticed that her breathing was labored. Her oxygen mask had visible fogging during her breathing cycles. During the flight to Talkeetna, the passenger remained seated in an upright position and unconscious. At one point, the son yelled his mother's name, which elicited a fluttering of her eyelids. Nine minutes later, the flight landed at Talkeetna. The passenger was transported to a hospital in Palmer, Alaska. During the ambulance ride while lying down, the son reported that his mother became more verbally responsive by answering obliquely to some questions, and ignoring others. She exhibited twitching of her right hand.

After admission to the hospital in Palmer, the passenger was placed on a ventilator for a period of time, and according to her son, his mother initially had a diagnosis of cerebral and pulmonary edema. On June 30, 2002, the passenger was transported to a hospital in Springfield, Illinois, then to a rehabilitation hospital, also in Springfield, and ultimately discharged for in-home rehabilitation on August 18, 2002. The son of the passenger reported that his mother has a diagnosis of an anoxic brain injury, and that she sustained cognitive deficits and physical limitations.

During a telephone conversation with the NTSB IIC, on August 21, 2002, the pilot indicated that the McKinley sightseeing flight usually lasts one hour and 15 minutes. An initial climb is made to about 8,000 feet msl. About 35 to 45 minutes later, a climb is made to 11,000 feet msl where everyone plugs in their oxygen mask to the airplane system, and everyone puts on their mask. The pilot said he verifies oxygen flow by observing a green flow indicator in each passenger's oxygen mask tubing and then climbs the airplane to 21,000 feet for a view of the summit of Mt. McKinley. He banks the airplane left and right so the passengers can get photographs. He then descends toward Talkeetna. The pilot said he was using a Scott brand oxygen mask with a bag reservoir and microphone, at a flow rate of 2.0 liters per minute. The passengers were using a disposable oxygen mask without a reservoir bag, at a flow rate of 1.5 liters per minute.

In the Pilot/Operator Accident/Incident Report (NTSB form 6120.1) submitted by the pilot, the pilot indicated he was informed of the passenger's incapacitation by the passenger's son about 60 minutes into the flight. The son also told the pilot that his mother had taken some type of pill medication. The medication was not identified. The pilot made radio contact with Talkeetna and emergency medical personnel met the flight on the ground. The pilot reported that the passenger was a large, elderly female, who according to her son, had a pre-existing respiratory and heart condition, and had undergone recent heart surgery.

Airplane Information

The incident airplane is non-pressurized, and has a service ceiling of 24,000 feet. The airplane's oxygen system, manufactured by Scott Aviation, consists of a high-pressure oxygen cylinder that supplies oxygen to an oxygen port at each seat. A continuous flow of supplemental oxygen is delivered to an oxygen mask when the airplane's oxygen system is turned on, and a fitting is inserted into an oxygen port. Each oxygen mask is attached at the end of plastic tubing running from a metal fitting to the mask. The flow rate of each mask is determined by the size of an orifice contained in the fitting. Flow of oxygen is visually determined when the fitting is plugged into an oxygen port, and a green band in an in-line flow indicator, becomes visible to the user.

According to the pilot's operating handbook for the incident airplane, the oxygen mask equipment is a Scott Aviation partial rebreather mask equipped with a reservoir bag. The bag acts as a reservoir where oxygen from the airplane's oxygen system mixes with partial exhalations from the passenger. The flow rate of Scott oxygen masks are identified by a stripe on the oxygen fitting. The operating handbook specifies that passenger's oxygen masks be identified with a gold stripe (1.5 liters per minute) or a red stripe (2.0 liters per minute). The pilot's oxygen mask, a partial rebreather oxygen mask equipped with a reservoir bag and a radio microphone, utilizes a flow rate of 2.0 liters per minute.

The FAA inspector indicated that following the call from the passenger's son, he inspected the oxygen system on the incident airplane. He did not discover any deficiencies with the oxygen system hardware. The inspector noted that at each passenger seat position, the operator was not utilizing the Scott oxygen mask with a reservoir bag, but was utilizing a disposable hospital type, Hudson RCI model 1041 medium concentration oxygen mask without a reservoir bag, with a flow rate of 1.5 liters per minute.

Aircraft Certification Information

Certification standards for the use of oxygen are published by the FAA in Title 14, CFR Part 23.1441 through 23.1449.

Paragraph (a)(3) of Federal Aviation Regulation Sec. 23.1443, states, in part: "(3) The minimum mass flow of supplemental oxygen supplied for each user must be at a rate not less than that shown in the following figure for each altitude up to and including the maximum operating altitude of the airplane." A review of the chart, with graph lines added by the NTSB IIC as a visual aid, revealed that at 21,000 feet, the minimum mass flow is about 1.8 liters per minute. A copy of the FAA's chart, with added graph lines, is included in the public docket of this report.

The FAA has a published Technical Standard Order (TSO) C64a, that prescribes the minimum performance standards for continuous flow, passenger oxygen masks. TSO-64a states, in part, that masks must meet the standards set forth in the Society of Automotive Engineers, Inc., (SAE), Aerospace Standard (AS) 8025. In addition, SAE Aerospace Standards for "Continuous Flow Aviation Oxygen Masks for Non-Transport Category Aircraft" are contained in AS 1224. AS 1224, Revision B, includes a description of four types of masks:

a. Open port dilution rebreathing mask - incorporates a rebreather bag into which exhaled gases are mixed with oxygen flowing into the bag. Valving is not present between the mask facepiece and the rebreathing bag.

b. Valved or restrictive phase dilution rebreathing mask - (1) utilizes a rebreather bag into which a constant flow of oxygen is introduced. A check valve or a restrictive sponge between the mask and ambient air, is provided so that ambient air will not be admitted before the rebreather bag has been depleted, or (2) utilizes a rebreathing bag but incorporates a restrictive sponge or other means which admits dilution air when subjected to a significant decrease in...