CSA AT72 at Prague on Sep 17th 2015, smoke indication, 44 taken to hospital and discharged with no symptoms

Last Update: December 14, 2017 / 17:05:57 GMT/Zulu time

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Incident Facts

Date of incident
Sep 17, 2015

Classification
Incident

Flight number
OK-544

Destination
Hamburg, Germany

Aircraft Registration
OK-GFS

Aircraft Type
ATR ATR-72-200

ICAO Type Designator
AT72

A CSA Czech Airlines Avions de Transport Regional ATR-72-212A, registration OK-GFS performing flight OK-544 from Prague (Czech Republic) to Hamburg (Germany) with 63 people on board, was in the initial climb out of Prague when the crew received a smoke indication, stopped the climb at about 5000 feet and returned to Prague for a safe landing about 12 minutes after departure. Emergency services found no trace of fire, smoke or heat. 44 people were taken to hospitals with the suspicion of smoke inhalation but discharged from hospital with no symptoms.

Prague's police reported that they were alerted after an ATR-42-500 reported smoke from air conditioning in the cabin. After landing no traces of fire were found, however 35 people were transported to hospital due to suspected smoke inhalation, another passenger later called in reporting sick.

The airport reported there were no injuries, the passengers taken to hospital were discharged with no symptoms found.

The airline reported the aircraft is being examined, a malfunction of the smoke detector is being suspected.

A passenger reported that it was unusual warm in the aircraft during boarding already, shortly after departure hot air was emitted by the air conditioning vents. Then flight attendants began to use their smoke hoods and oxygen cylinders obviously in reaction to smoke in the forward cabin and supplied passengers with wet towels, about 2 minutes later the aircraft began to return to Prague, the smoke and heat dissipated. The captain announced that the left hand air conditioning systems appeared to be defective, they were now performing an emergency landing back to Prague and passengers should assume the brace position for landing. The aircraft touched down pretty hard, stopped on the runway for about 1-2 minutes before continuing to the apron. Other passengers reported that the left hand side wall of the cabin was hot.

On Oct 13th 2015 the French BEA reported in their weekly bulletin that smoke was detected in the cabin shortly after takeoff, the crew performed the related memory items, declared emergency and performed an immediate air return. The aircraft landed uneventfully. No injuries are being reported. The occurrence was rated a serious incident, Czech's AAII is investigating the occurrence.

On Oct 23rd 2015 Czech's UZPLN (aka AAII) reported that the aircraft was climbing through 4000 feet when smoke became apparent in the cabin and the cabin temperature rose. The crew performed the memory items for smoke in the cabin, declared Mayday. Cabin crew were providing the passengers with filters in the form of wet paper towels. An immediate return to Prague resulted in a safe landing, the passengers disembarked normally and were bussed to the terminal. Maintenance replaced pneumatic seals and pipes associated with the air conditioning system of the aircraft, no heat or fire damage was found.

On Dec 14th 2017 Czech's UZPLN released their final report concluding the cause of the serious incident was:

The cause of the serious incident was the leakage caused by damage/wear and tear of the rubber-textile gaskets in the leaking pneumatic pipeline compensator on the lefthand side under the passenger cabin floor and damage to the rubber-textile compensation bellows connecting the left-hand air conditioning system branch heat exchanger with the system pipeline.

The UZPLN reported that following a normal engine start the aircraft taxied to the holding point for departure where the right hand engine air bleed fault indication came on. The crew shut the #2 bleed air system down with the aim to reset it during the initial climb after takeoff. The aircraft departed runway 24 and was climbing through 3000 feet when the #2 bleed air system was re-enaged without any abnormal indications. Climbing through 3800 feet the crew received a "TEMP SEL OVHT CABIN" indication, the crew observed the temperature in the air conditioning ducts rose. Climbing through 4140 feet the lead flight attendant informed the flight deck of smoke in the cabin. The crew stopped the climb at 4520 feet and returned to Prague. The crew carried out the "smoke on board" checklists while the captain was handflying the aircraft, the crew donned their oxygen masks but did not don their smoke goggles as they only felt smell of smoke. The captain re-engaged the autopilot. While the first officer worked the emergency smoke and air conditioning smoke checklists the intensity of the odour decreased, flight attendants reported the smoke in the cabin was dissipating. The aircraft positioned for an ILS approach to Prague, shortly before touch down the captain instructed via PA "Brace for Impact", the aircraft landed safely and stopped on the runway near taxiway C. Flight attendants confirmed there was no smoke anymore in the cabin, the captain thus decided to taxi the aircraft to the stand for rapid disembarkation there.

The UZPLN reported that there were no injuries.

Maintenance discovered that four textile sealing gaskets of the compensator of the pneumatic pipeline in the left air conditioning system were leaking underneath the passenger floor. The hot air exiting the pipeline affected dust in the area causing smoke and was drawn into left recirculation fan, which distributed the smoke into the cabin.

The UZPLN analysed with respect to the bleed air fault prior to departure: "No technical failure of the system was the cause of the defect signalling during the taxiing but the circumstances regarding the passenger cabin air-conditioning at very high external air temperatures employing No. 2 engine in the “HOTEL MODE” led very likely to the false indication and failure alarm."

The UZPLN analysed the "TEMP SEL OVHT CABIN" indication: "The rise of the air temperature was caused by the hot air leakage from the damaged rubber-textile compensation bellows connecting the heat exchanger of the airconditioning system with the air-conditioning pipeline which led to incorrect regulation of the temperature in the system and to rising of temperature in the air-conditioning system pipeline and to “TEMP SEL OVHT CABIN” signal."

The UZPLN analysed the smoke in the cabin: "The occurrence of smoke in the passenger cabin was caused by the hot air leakage (air temperature up to 200 °C) due to the faulty leak tightness of the pneumatic system compensator. The faulty tightness properties were caused by the damage of the rubber-textile gasket rings in the compensator in the left-hand branch of the pneumatic pipeline under the passenger cabin floor. Here, due to the effect of the hot air stream, the present dust was whirled up. Subsequently, the dust was drawn in by the recirculation fan located also in this area. The said hot air mixed with the whirled dust was then distributed into the passenger cabin. With an absolute certainty, the contamination of the pneumatic system with the working fluids or fumes of the exhaust gases can be eliminated as the cause of the smoke. "

One safety recommendation to the operator was issued to inspect the gaskets underneath the passenger floor on the all their AT72s at the next ground time.
Incident Facts

Date of incident
Sep 17, 2015

Classification
Incident

Flight number
OK-544

Destination
Hamburg, Germany

Aircraft Registration
OK-GFS

Aircraft Type
ATR ATR-72-200

ICAO Type Designator
AT72

This article is published under license from Avherald.com. © of text by Avherald.com.
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