The Insidious Killer

A recurring theme from the NTSB and others over the years has been that pilots should never hesitate to declare an emergency, seek all available help and take positive corrective action. The Safety Board, in a departure from its habit of not including analysis and comments in most general aviation accident reports, included a commentary about declaring emergencies as part of its recently released report on the September 4, 2014, accident involving a Socata TBM 700 (marketed as a TBM 900). While thoughts from the NTSB about declaring emergencies surely will be useful for many pilots, my hunch is that the pilot of the accident airplane normally would have been quite competent to decide for himself when declaring an emergency was appropriate. Problem is, given what was going on, his ability for adequate decision-making was compromised.

The airplane was flown by Larry Glazer, a real estate developer who had served as chairman of the TBM Owners and Pilots Association. He had written on aviation safety for his fellow TBM pilots and knew his stuff when it came to TBM airplanes. As a pilot, Glazer was no slouch. He was serious about flying a serious airplane, had owned two other TBM 700 airplanes, had undergone formal intensive training, had a glass cockpit simulator on his personal computer and took care of himself with regular exercise and good eating habits.

The airplane was a Daher-Socata TBM 900 that had been manufactured in 2014. It was registered to the accident pilot on April 8, 2014, about a month after it had received a standard airworthiness certificate. The pressurized airplane was powered by a Pratt and Whitney PT6A-66D turboprop engine. The NTSB didn't provide specific performance numbers for the accident airplane, but these models can weigh in at around 7,400 pounds, fly as high as FL310, produce jet-like speeds above 300 knots and cover 1,600 or 1,700 nautical miles at reduced speeds and fuel flows. 

The airplane was based at the Greater Rochester International Airport (KROC), Rochester, New York. Glazer and his wife would be using it for a personal flight to the Naples Municipal Airport (KAPF), Naples, Florida. The Safety Board did not provide details of weather briefings received by the pilot for the flight, but he did file an IFR flight plan.

On the morning of the accident, personnel from an FBO at KROC towed the airplane from its hangar space to the ramp. When the pilot arrived, he chatted briefly with two FBO employees while waiting for his wife to arrive. They said he was relaxed, and when his wife arrived, they loaded their baggage and got on board.

The pilot, age 68, held a commercial certificate for single-engine land and instruments. His third-class medical was current but required that he wear glasses for distant vision and have glasses for near vision. He had a total time of about 7,100 hours.

His wife also was 68. She held a private pilot certificate for single-engine land airplanes. Her last third-class medical was in July of 1992. Back then she reported 410 flight hours. Her logbooks could not be found after the accident.

An FBO employee pulled the chocks and, after engine start, directed the pilot out of the ramp area.   

Takeoff time was about 8:26 a.m., and ATC cleared the flight to climb to 9,000 feet. A few minutes later, the flight was cleared to FL280.

Everything was routine until about 9:12 a.m. While operating in Cleveland Center's airspace at FL280, the controller radioed the pilot for a handoff to the next sector. There was no response from the aircraft. The controllers kept trying, and four minutes and 30 seconds after the first attempt, the pilot responded with "Cleveland, TBM nine hundred kilo november." The controller replied, "!Cleveland Center, how do you read?" The pilot answered, "Loud and clear, ah, something happened, I don't know what happened to you but we're back." The controller then issued the new frequency to the pilot, who promptly switched and checked in with, "Cleveland Center, zero kilo november is level at two eight thousand." The controller then advised the pilot to contact Washington Center on a new frequency. The pilot did not acknowledge, but his wife did. Then, she came up on Washington Center, reporting level at FL280.

At about 9:19, the controller radioed that the flight was "!cleared direct to Pulaski, that's papa sierra kilo, then direct Taylor, rest of route unchanged." The pilot then responded, "Okay, see---sierra kilo then, ah, direct ah, for nine hundred kilo november." The controller replied, "And november zero kilo november, just want to verify, proceed direct Pulaski now, that's papa sierra kilo, then direct Taylor, tango alpha yankee, rest of the route unchanged."

At about 9:21, the controller issued a frequency change and the wife acknowledged and came up on the new Washington Center frequency. Later, the flight was handed off to Atlanta Center and, at 10:04:17, the pilot radioed, "Nine hundred kilo november, we need to descend, ah, down to about one eight zero, we, ah, have an indication that's not correct in the plane."

After getting another controller to stop an airliner at FL240 for separation, the Socata was cleared to descend to FL250. At 10:04:37, the pilot confirmed the clearance to FL250 but said, "We need to get lower, nine hundred kilo november."

The controller explained "Working on that, you have that traffic twelve o'clock and  fifteen miles northbound, flight level two four zero?" There was no reply. The controller then radioed, "Are you declaring an emergency sir?" 

At 10:04:50, the pilot radioed, "Ah, not yet, but we'll let you know."  The controller then said, "And, ah, to help get you down, november zero kilo november, turn, ah, thirty degrees left, help get you down." The pilot acknowledged. At 10:06:35, the controller cleared the flight down to FL200, but there was no response. He repeated the new clearance and, at 10:06:47, the pilot responded with the airplane's call sign.
At 10:07:17, the controller cleared the flight direct to the Taylor VOR. There was no acknowledgement and no apparent change in course or altitude, and the controller repeated the clearance. At 10:07:36, the pilot confirmed, "Direct Taylor, nine hundred kilo november."

At 10:08:10, the controller again told the pilot, "!You got descent to flight level two zero zero." The pilot acknowledged, "Two zero zero, kilo november."

At 10:08:40, the controller radioed, "November zero kilo november, descend and maintain flight level two zero zero, and you are cleared direct taylor." The pilot replied, "Direct kilo november nine hundred kilo november."

The controller apparently was growing concerned at the pilot's failure to descend, and radioed at 10:09:50, "November zero kilo november, I don't know if you're, ah, understanding me, but descend and maintain flight level two zero zero, flight level two zero zero, for november niner zero zero kilo november."

There was no response and, at 10:10:11, the controller radioed, "TMB, TBM zero kilo november, descend and maintain flight level two zero zero, how do you read?"  Again, there was no response. The airplane continued on its course and held its altitude. The controller asked other aircraft to try to raise the pilot. There were numerous transmissions in the blind trying to get the pilot to respond and telling him to descend. But there was no response.

At about 10:37, two Air National Guard F-16 fighter jets were scrambled from the McEntire Joint National Guard Base near Eastover, South Carolina. ATC vectored them to intercept the Socata about 40 miles south of the base.

One of the F-16 pilots later told investigators that the airplane was at FL250 at an indicated airspeed of 175 knots and on a heading of 165 degrees. The pilot could see that the rear window shades were down and the anti-collision lights were operating normally.

The F-16 pilot could see the male occupying the left seat. He was wearing a yellow golf shirt, and his head was pointing straight back with the boom mic on his headset pointing straight up. The F-16 pilot maneuvered the jet and could see Glazer's hands were resting in his lap and not moving. His wife, in the right seat, could be seen wearing a black baseball cap. She was slumped down in her seat with her head against the right side of the airplane. Her boom mic was visible and her hands were in her lap.

About an hour and 20 minutes after the intercept, the left seat pilot's head slumped forward. His chest could be seen rising and falling, which it was believed was consistent with the breath pattern of someone who is unconscious.   

The second F-16 pilot reported there were no signs that the pilot was holding any equipment, such as a GPS receiver or an oxygen mask. It did appear that he had a folded chart or approach plate under his right hand. This pilot also said that from what he could see, there were no flashing lights inside and "the instrument panel appeared to be working normally." The airplane remained straight and level, even flying through a thunderstorm build-up about five miles in diameter without an in-flight upset.

The F-16s tracked the Socata for about 400 miles, then disengaged after two F-15s from Homestead Air Reserve Base, Homestead, Florida, arrived in the area. They were about 70 miles east of Daytona Beach, Florida, at the time. The Socata remained straight and level, speed and heading unchanged. The F-15 pilots said they did not see any signs of smoke or fluids coming from the engine. They stayed with the Socata until reaching Cuban airspace.

The airplane continued flying until about 2:09 p.m. when radar data showed it entering a high speed descent from FL250. The last radar target was recorded at 10,000 feet about 20 nautical miles north of Port Antonio, Jamaica. With the engine dead from fuel starvation, the airplane crashed into the Caribbean Sea.

The U.S. Coast Guard and Jamaican Defense Authority sent aircraft and ships to the area, where they found an oil slick and small pieces of debris. An underwater vehicle was used to locate the wreckage, which was brought up about four months later.

In examining various aircraft systems, investigators analyzed data recorded in the memory of the airplane's global air system controller (GASC). It showed that there had been problems with the cabin pressurization system. A thermostatic switch designed to prevent overheating had shut down, cutting off engine bleed air to the cabin pressurization system. Without engine bleed air being fed in, the cabin altitude would have equalized with the outside pressure at 28,000 feet in about four minutes. Warnings on the crew alerting system (CAS) and elsewhere would have alerted the pilot to a problem, and investigators believed the pilot's request for a descent to FL 180 is evidence that the pilot was aware of a pressurization problem.

Investigators also believe that failing to requesting a descent to 10,000 feet where air pressure and oxygen would not have been a problem, accepting a descent of only 3,000 feet to FL250, and declining to declare an emergency indicated the pilot already was affected by hypoxia.

Keep in mind that with hypoxia, not only are you not aware you're being oxygen-starved, you can feel sensations of euphoria. Other symptoms include fatigue, nausea, headache, dizziness, hot and cold flashes, tingling and visual impairment. While time of useful consciousness at FL280 is only about 2.5 to 3 minutes, according to the FAA, at FL180 it is from 20 to 30 minutes. It's possible that when the pilot made his initial request for a descent, he thought FL180 would provide enough breathing room. It's also possible that his mind was already playing hypoxic tricks, and instead of making him ask for a descent "to" 10,000 feet, it had him calculate a descent "of" 10,000 feet.   

The NTSB's Vehicle Recorder Laboratory studied the radio transmissions from the pilot. Some indicated likely dysfunction when, after finishing speaking, he held the transmit switch open for as long as 4.3 seconds without saying anything.

The military pilots brought back photos that were examined by investigators. The photos confirmed that neither occupant was wearing an oxygen mask. Close examination revealed that the bottom corners of the emergency exit door on the right side of the fuselage appeared to be recessed into the door frame. The manufacturer showed investigators that when a TBM 900 is pressurized, that door protruded out from the door frame. In flight at FL280, the cabin would normally be pressurized to about 8,000 feet.

In talking with people who had known and flown with the pilot, investigators learned that he was usually meticulous about preflight inspections and procedures, including opening the door to the oxygen system supply bottle and verifying that the cylinder's valve was turned on. He also would turn on the cockpit oxygen switch and confirm that oxygen was flowing into the standby masks. The NTSB noted, however, that in the wreckage the cockpit oxygen switch was found in the off position. They couldn't determine why it had been off but said it likely didn't matter because neither occupant was wearing a mask.

Investigators noted that the Pilot's Operating Handbook for the airplane was 656 pages long and contained four emergency checklist procedures for responding to CAS messages about the pressurization system. Only one of the procedures called for immediately putting on an oxygen mask, and it was a suggestion rather than a requirement. The Safety Board reported that the airplane manufacturer subsequently revised emergency procedures to make the donning of oxygen masks a required priority item.

The Safety Board reported that the manufacturer had designed the pressurization system so that the GASC is forced to shut down the flow of bleed air if the bleed air temperature gets above a certain point and does not fall back to a lower temperature in 30 seconds. The purpose is to protect the system, the passengers and the airplane. The NTSB reported that as a result of this accident, the manufacturer made changes to the system's programming to make it less aggressive in commanding bleed air shutdowns.

The NTSB determined that the probable cause of this accident was the design of the cabin pressurization system, which made it prone to unnecessary shutdown, combined with a checklist design that prioritized troubleshooting over ensuring that the pilot was sufficiently protected from hypoxia. This resulted in a loss of cabin pressure that rendered the pilot and passenger unconscious during cruise flight and eventually led to an in-flight loss of power due to fuel exhaustion over the open ocean.

In its comments, the NTSB said, "Take charge and tell the controller what you need. Do not be afraid to inform ATC that you are ’unable' if you are given directions you cannot comply with in a safe manner, and do not rely on ATC to provide emergency handling unless requested." It also admonished readers to, "Remember that declaring an emergency isn't giving up control--it's taking control!" The NTSB's concern with declaring emergencies notwithstanding, I find this  accident can benefit us all with an appreciation of just how insidious hypoxia can be.

Peter Katz is editor and publisher of NTSB Reporter, an independent monthly update on aircraft accident investigations and other news concerning the National Transportation Safety Board. To subscribe, visit www.ntsbreporter.us or write to: NTSB Reporter, Subscription Dept., P.O. Box 831, White Plains, NY 10602-0831.