An evacuation slide on an Allegiant Air Boeing MD-80 malfunctioned during an emergency evacuation last week at Las Vegas McCarran International airport, Allegiant Air tells Flightglogal.
The US Federal Aviation Administration (FAA) is investigating why the slide did not deploy as designed and whether it was properly inspected by the airline, the agency tells Flightglobal.
New details provided by Las Vegas-based Allegiant about the 16 September evacuation paint a clearer picture of circumstances that prompted the airline to ground more than half its MD-80 fleet last week while it inspects emergency slides.
Allegiant says the evacuation, which did not cause any injuries to passengers, was prompted by an alarm from a smoke detector in the aircraft’s lavatory.
The crew also reported there was “fog” visible in the cabin of the aircraft, which was about to depart for Peoria, Illinois, says Allegiant.
The airline says there was no onboard fire. Rather, the auxiliary power unit was burning oil and the resulting smoke was “being sucked back into the aircraft”, says Allegiant.
“It appeared as a haze... like a fog or smoke, and [had] a faint smell,” the airline says, adding that passengers were not in danger.
In response to the smoke alarm, the flight crew ordered an evacuation using the aircraft’s four inflatable slides, manufactured by Zodiac Aerospace.
Allegiant says one of those slides malfunctioned. It “over inflated” and could not be used, and passengers evacuated safely using other slides.
It adds that all slides on the aircraft had been inspected within the last year, as recommended by Zodiac.
“Those slides were all compliant. The fact that [one] didn’t deploy has nothing to do with being out of compliance,” Allegiant says.
Allegiant says that the evacuation prompted a broader review of MD-80 slides, which led it to determine that many slides had not been inspected within the last year. Rather, the airline had overhauled slides every three years.
Zodiac had previously recommended overhauls every three years, but in 2007 changed its recommendations to suggest overhauls once yearly for slides more than 15 years old, according to the airline.
Allegiant’s MD-80s are 24 years old on average, according to Flightglobal's Ascend Online database.
The discovery, announced by Allegiant 20 September, led the airline to ground more than half its fleet of 52 MD-80s, causing delays and flight cancellations.
The airline said that it was sending all non-compliant slides to an outside facility for inspection, a process that would take five days per aircraft.
The airline had 30 MD-80s back in service as of 24 September, and completed its two scheduled flights on 25 September.
Allegiant, which has very few flights on slow travel days but more than 100 on busy days, expects it will operate all flights tomorrow with help from aircraft charted by other carriers.
The airline hopes to have all of its MD-80s back in service by 30 September.