Several of you have sent me stories about the emergency evacuation slide that was inadvertently dropped from a United Airlines 767-300 just prior to landing at Chicago O’Hare on Monday afternoon. This will be a more technical post, but let’s seek to understand how something like this could have happened in the first place. Did someone actually open the emergency exit door? At this point, it is a mystery.
Emergency Evacuation Slide Drops From United 767-300 Over Chicago O’Hare
On July 17, 2023, UA12, a United Airlines 767-300 traveling from Zurich (ZRH) to Chicago (ORD) lost an emergency evacuation slide as it was on approach to Chicago O’Hare International Airport. It appears that pilots and flight attendants onboard were not even aware it had been lost, as it was noticed by maintenance works on arrival.
But residents on the 4700 block of North Chester in Chicago certainly noticed it: their afternoon was suddenly disturbed by a huge boom. The slide hit the roof of Patrick Devitt, damaging it, then slid down before settling in his backyard.
Hours later, uniformed United Airlines personnel were seen collecting it. A United spokesperson shared:
“We immediately contacted the FAA and are working with our team to better understand the circumstances around this matter.”
So how does this happen in the first place? The answer may be in the unique way in which the 767 overwing exit slide is stored outside the aircraft rather than inside the door.
When a similar incident occurred in Canada, investigators explained the occurrence in this way:
The Boeing 767 incorporates an inflatable slide at the inboard rear of each wing to allow the evacuation of passengers who use the over-wing exits during an emergency. Slide deployment is initiated by opening the exit hatch from the inside. The hatch opening motion actuates electrical switches that simultaneously (1) operate a relay to ground out any position command going to the main hydraulic spoiler power controller actuator, and (2) fire the spoiler override actuator which rotates the inboard spoiler to the down position. After a two-second time delay (from the spoiler actuator firing), the latch opening actuator is fired. The latch opening actuator opens the escape slide compartment door latches and fires the door opening actuators located in the escape slide compartment. The slide compartment door, with the escape slide packboard assembly attached, is rotated outboard by the actuators. When the door opens, a mechanical link to a high pressure inflation cylinder triggers the release of gas that inflates the slide.
But notice the bolding. Deployment of the slide is triggered by the opening of the overwing exit in the armed condition. So is that what happened here? And if so, was the flight deck really totally unaware of it?
Or could it be that the slide somehow dropped (since it did not deploy) without the exit door actually being opened?
When a similar incident occurred on a Delta 767 in 2019, it appears it was the airstream that ripped the slide off, but in that case, the slide did deploy.
CONCLUSION
An emergency exit slide dropped from a United 767 while on approach to ORD on Monday. No injuries were reported, although there was property damage reported.
We will be monitoring this story for updates from the FAA and United that better explain how this occured. In the meantime, any theories? Is it possible a passenger partially opened the overwing exit door?
Just want to point out the registration of this aircraft is “N666UA.”
So 666 lol..what luck
The next sentences after your bolded one from the Canadian report is probably the answer: “The hatch opening motion actuates electrical switches that simultaneously (1) operate a relay to ground out any position command going to the main hydraulic spoiler power controller actuator, and (2) fire the spoiler override actuator which rotates the inboard spoiler to the down position. After a two-second time delay (from the spoiler actuator firing), the latch opening actuator is fired.”
Assuming some short or other electrical fault triggered the sequence that would actuate the ramp slide deployment in the same way as if the hatch was opened. Perhaps the pilots probably received some sort of fault or warning regarding spoiler deployment, and (if received) elected to continue the landing. Obviously on the ground it would be evident that the slide pack was deployed, and maybe even observed by passengers over the wing.
so is United on the hook to pay for the damage to the home owner’s property?
You better believe they are, along with some free round trip tickets I imagine.
They’ll get the usual 30k miles Kirby Special like those stuck at Newark a week or two ago!! 🙂
LOL!!!
Was Delta on the hook for a simila incident that happened in 2019? If Delta was, then United should be. If Delta wasn’t, then Unuted shouldn’t be.
Any comment from the best CEO in the business who happens to run the best airline in the world with the best fleet, network and catering? Normally he can’t keep his mouth shut!
Don E-perfectly put. If he’d just STFU and run the airline, it might run better. He is clearly a very smart man.
So true!
I’m uneasy about flying United…. it’s been a long time since I’ve traveled with them without delays for late-discovered tech issues. I have no doubt that they do the required regular maintenance, but somehow my United planes are always broken anyway. It doesn’t inspire confidence in their schedule. It also makes me think about safety in a way I’m not used to.