Fliers in small planes at risk of oxygen shortage

MUMBAI: It is a small detail but it could mean the difference between life and death. If you are in a turbo prop aircraft like a Bombardier Q400 or an ATR aircraft, oxygen masks in these flying machines are not deployed automatically during an emergency in case oxygen levels in the passenger cabin dip, making it hard to breathe.

In such situations, passengers in such aircraft are expected to make do with poor oxygen supply for a maximum of four minutes, which is something a healthy person can endure. But if you have an asthma condition or a pulmonary or cardiac problem or are severely anaemic or if you are a heavy smoker, you could be in trouble. The same would apply if you are a senior citizen or if you are flying with a baby.

Bombardier Q400 aircraft have no oxygen masks for passengers. One has to call for help and the flight attendant is expected to rush with an oxygen cylinder which has masks attached. In case of an ATR aircraft, the flight attendant will have to come to your row and manually deploy the oxygen mask, which though is available only for 25 percent of the passengers. Turbo props are the comparatively small aircraft, with 40-70 passenger carrying capacity, with propellers attached to wings that fly on short domestic routes like Mumbai-Surat, Mumbai-Mangalore, Chennai-Calicut, Hyderabad-Calicut etc. There are about 38 such turbo prop aircraft with three airlines in India and on an average these operate about 120 domestic flights a day.

All aircraft that fly above 13,000 feet need to be, what is called in aviation parlance, "pressurized". That is because atmospheric pressure and temperature falls with increase in height (as experienced when travelling to a high-altitude region) and consequently oxygen levels in atmosphere go down. An aircraft cabin is pressurized to keep atmospheric pressure and oxygen at levels comfortable to human beings, so the cabin altitude is maintained to that of about 7000 to 10,000 feet, though the actual altitude of the aircraft would be much higher. When a pressurization problem occurs, the aircraft is brought down to 13,000 feet or lower as at these lower altitudes passengers can breathe normally even if the pressurization system in an aircraft is not functioning properly.

Since jet aircraft like A320s, B737s can fly up to an altitude of about 40,000 feet, these are equipped with oxygen masks that deploy automatically when a pressurisation problem occurs and the cabin altitude climbs to above 14,000 feet. But turbo prob aircraft like ATR and Q400s can fly only up to 25,000 feet. Aircraft manufacturers reason that these aircraft can be put in a rapid descent and brought down to 13,000 feet in about four minutes if a pressurization problem occurs. Consequently, they have not paid much attention to the need for oxygen masks for passengers. Aviation regulators in Canada and Europe (where these two aircraft are manufactured) and in India too do not consider it much of a problem.

"The most significant issue here is that the health status of the passenger decides how well he/she can handle such a situation," said Dr Anil Mehra, CEO of India Aeromedical services, an air ambulance company. "Even an altitude of 13,000 feet is not comfortable for patients with compensatory cardiovascular system or severe anaemia or similar conditions," he added. Capt Mohan Ranganathan, member Civil Aviation Safety Advisory Council, who brought the matter to the notice of the director general of civil aviation last week said: "The aviation regulator should have taken the passengers health and safety into consideration rather than blindly clearing the aircraft for flight without the protection. It is surprising that airlines do not inform the passengers about this in the safety card." He cited a NASA report on an incident that occurred in November 2011 in the US when a Q400 aircraft climbing to 14,000 feet experienced pressurization problem. "All on board including the crew experienced severe discomfort, so this is not an important issue," he added. TOI wrote to the three airlines that operate these aircraft, but all the three have asked for a day to respond.

While ATR aircraft have oxygen masks for 25 percent of passengers, these are not automatically deployed when the cabin pressure falls and the oxygen levels decrease. "Cabin crew members are expected to go to each passenger row and manually deploy the oxygen masks," said a source. The problem here is that the passenger safety card illustrates that oxygen masks will be deployed automatically, which is not the case. "When there is a decompression problem, the commander puts the aircraft into a rapid descent and flight attendants are supposed to go to their seats and stay buckled. Only after the aircraft has levelled off at 13,000 feet, which could take anywhere between a few seconds to four minutes depending on how high the aircraft was, does the cabin crew get up to help, which could be too late for an asthma patient," he added.

In case of Bombardier Q400 aircraft, there are no oxygen masks for passengers at all. The aircraft has portable oxygen cylinders with masks attached and cabin crew is expected to go to the passengers facing difficulty with breathing. "It is surprising that the aviation regulators have allowed passenger aircraft to operate without oxygen masks," said a commander. TOI spoke to about 14 pilots and co-pilots, three of whom had flown ATRs early in their career, and all were surprised to learn that oxygen masks are not deployed automatically in these aircraft types. "I'm sure not a single passenger knows that in turbo prop aircraft they should be prepared to face breathing difficulties in case of depressurization emergency," said a commander.

Said Dr Mehra: "There are no straight answers here, how well can a passenger cope with this depends on the amount of acclimatisation he/she has gone through. But I definitely feel there should be individual oxygen masks for everyone on board these aircraft. "Otherwise, it is about keeping fingers crossed," he said.

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